Acid rain

@article{doi101021ja01250a059,
    author = "Harned, Herbert S. and Davis, R. T.",
    title = "The Ionization Constant of Carbonic Acid in Water and the Solubility of Carbon Dioxide in Water and Aqueous Salt Solutions from 0 to 50°",
    year = "1943",
    journal = "Journal of the American Chemical Society",
    url = "https://doi.org/10.1021/ja01250a059",
    doi = "10.1021/ja01250a059",
    openalex = "W2313107789"
}

@article{doi101016001670375590034x,
    author = "Gorham, Eville",
    title = "On the acidity and salinity of rain",
    year = "1955",
    journal = "Geochimica et Cosmochimica Acta",
    url = "https://doi.org/10.1016/0016-7037(55)90034-x",
    doi = "10.1016/0016-7037(55)90034-x",
    openalex = "W2006633749"
}

The distribution of yearly averages of the concentration of various inorganic ions in rain water over the United States is discussed. The major source of Cl−is the ocean. The Cl−/Na+ ratio, however, is considerably less than that in sea water. It is very likely that this is caused by excess Na+ from the soil. A similar distribution of excess material from the soil is observed with K+. In contrast to Na&plus: and K+, which are rather uniformly distributed over the United States, Ca+ shows highest values over the Southwest, in agreement with the occurrence of dust storms. Most of the SO4— over the ocean originates from sea spray. The source of additional SO4— is the land. Budget considerations indicate that about 30 per cent of this additional SO4— on a global scale is due to human activities. On the basis of the data presented, the average global residence time of SO2 is estimated to be 40 days. This value is compared with available data on residence times of other constituents which are also primarily controlled by washout.

@article{doi1011751520046919580150417tcocsp20co2,
    author = "Junge, Christian and Werby, R. T.",
    title = "THE CONCENTRATION OF CHLORIDE, SODIUM, POTASSIUM, CALCIUM, AND SULFATE IN RAIN WATER OVER THE UNITED STATES",
    year = "1958",
    journal = "Journal of Meteorology",
    abstract = "The distribution of yearly averages of the concentration of various inorganic ions in rain water over the United States is discussed. The major source of Cl−is the ocean. The Cl−/Na+ ratio, however, is considerably less than that in sea water. It is very likely that this is caused by excess Na+ from the soil. A similar distribution of excess material from the soil is observed with K+. In contrast to Na\&plus: and K+, which are rather uniformly distributed over the United States, Ca+ shows highest values over the Southwest, in agreement with the occurrence of dust storms. Most of the SO4— over the ocean originates from sea spray. The source of additional SO4— is the land. Budget considerations indicate that about 30 per cent of this additional SO4— on a global scale is due to human activities. On the basis of the data presented, the average global residence time of SO2 is estimated to be 40 days. This value is compared with available data on residence times of other constituents which are also primarily controlled by washout.",
    url = "https://doi.org/10.1175/1520-0469(1958)015<0417:tcocsp>2.0.co;2",
    doi = "10.1175/1520-0469(1958)015<0417:tcocsp>2.0.co;2",
    openalex = "W2078957100"
}

@article{doi1010160013932774900354,
    author = "Wood, Tim and Bormann, Franz–Josef",
    title = "The effects of an artificial acid mist upon the growth of Betula alleghaniensis britt",
    year = "1974",
    journal = "Environmental Pollution (1970)",
    url = "https://doi.org/10.1016/0013-9327(74)90035-4",
    doi = "10.1016/0013-9327(74)90035-4",
    openalex = "W2051465941"
}

@article{doi1010160043135474900128,
    author = "Beamish, Richard J.",
    title = "Loss of fish populations from unexploited remote lakes in Ontario, Canada as a consequence of atmospheric fallout of acid",
    year = "1974",
    journal = "Water Research",
    url = "https://doi.org/10.1016/0043-1354(74)90012-8",
    doi = "10.1016/0043-1354(74)90012-8",
    openalex = "W2146380832"
}

Analysis of recent precipitation samples from the northeastern United States has shown a consistent p H of less than 4.4, when the expected p H based upon equilibrium with CO 2 would be 5.6. A stoichiometric formation process being assumed, some 65% of the acidity is due to H 2 SO 4, 30% to HNO 3, and less than 5% to HCl. The p H values may be predicted from chemical content and generally agree to within 0.1 p H unit with the observed p H. The distribution of acid precipitation encompasses most of the northeastern United States. This pattern apparently has existed since about 1950–1955, but the intensity of acid deposition, especially that due to HNO 3, has increased since then. Analysis of prevailing winds indicates that much of the acidity originates as a general source over industrial areas in the Midwest.

@article{doi101029wr010i006p01133,
    author = "Cogbill, Charles V. and Likens, Gene E.",
    title = "Acid precipitation in the northeastern United States",
    year = "1974",
    journal = "Water Resources Research",
    abstract = "Analysis of recent precipitation samples from the northeastern United States has shown a consistent p H of less than 4.4, when the expected p H based upon equilibrium with CO 2 would be 5.6. A stoichiometric formation process being assumed, some 65\% of the acidity is due to H 2 SO 4, 30\% to HNO 3, and less than 5\% to HCl. The p H values may be predicted from chemical content and generally agree to within 0.1 p H unit with the observed p H. The distribution of acid precipitation encompasses most of the northeastern United States. This pattern apparently has existed since about 1950–1955, but the intensity of acid deposition, especially that due to HNO 3, has increased since then. Analysis of prevailing winds indicates that much of the acidity originates as a general source over industrial areas in the Midwest.",
    url = "https://doi.org/10.1029/wr010i006p01133",
    doi = "10.1029/wr010i006p01133",
    openalex = "W2054680869"
}

At present, acid rain or snow is falling on most of the northeastern United States. The annual acidity value averages about pH 4, but values between pH 2.1 and 5 have been recorded for individual storms. The acidity of precipitation in this region apparently increased about 20 years ago, and the increase may have been associated with the augmented use of natural gas and with the installation of particle-removal devices in tall smokestacks. Only some of the ecological and economic effects of this widespread introduction of strong acids into natural systems are known at present, but clearly they must be considered in proposals for new energy sources and in the development of air quality emission standards.

@article{doi101126science18441421176,
    author = "Likens, Gene E. and Bormann, Franz–Josef",
    title = "Acid Rain: A Serious Regional Environmental Problem",
    year = "1974",
    journal = "Science",
    abstract = "At present, acid rain or snow is falling on most of the northeastern United States. The annual acidity value averages about pH 4, but values between pH 2.1 and 5 have been recorded for individual storms. The acidity of precipitation in this region apparently increased about 20 years ago, and the increase may have been associated with the augmented use of natural gas and with the installation of particle-removal devices in tall smokestacks. Only some of the ecological and economic effects of this widespread introduction of strong acids into natural systems are known at present, but clearly they must be considered in proposals for new energy sources and in the development of air quality emission standards.",
    url = "https://doi.org/10.1126/science.184.4142.1176",
    doi = "10.1126/science.184.4142.1176",
    openalex = "W1986898463",
    references = "doi1010160013932774900354, doi101016001670375590034x, doi1010160043135474900128, doi101029wr004i005p01115, doi1010800013915719729932992, doi101139f72169, doi1011751520046919580150417tcocsp20co2, doi1023071942313, doi1023072259041"
}

@article{doi101038scientificamerican107943,
    author = "Likens, Gene E. and Wright, Richard F. and Galloway, James N. and Bütler, Thomas",
    title = "Acid Rain",
    year = "1979",
    journal = "Scientific American",
    url = "https://doi.org/10.1038/scientificamerican1079-43",
    doi = "10.1038/scientificamerican1079-43",
    openalex = "W4234179445"
}

Atmospheric inputs of sulfuric acid and nitric acid to noncalcareous higher-elevation watersheds in the White Mountain and Adirondack regions lead to comparatively high concentrations of dissolved aluminum in surface and ground waters. This phenomenon appears to result from modern increases in soil aluminum leaching. Transport of this aluminum to acidified lakes can lead to fish mortality. Combined results from areas of silicate bedrock in the United States and Europe suggest that aluminum represents an important biogeochemical linkage between terrestrial and aquatic environments exposed to acid precipitation.

@article{doi101126science2044390304,
    author = "Cronan, Christopher S. and Schofield, Carl L.",
    title = "Aluminum Leaching Response to Acid Precipitation: Effects on High-Elevation Watersheds in the Northeast",
    year = "1979",
    journal = "Science",
    abstract = "Atmospheric inputs of sulfuric acid and nitric acid to noncalcareous higher-elevation watersheds in the White Mountain and Adirondack regions lead to comparatively high concentrations of dissolved aluminum in surface and ground waters. This phenomenon appears to result from modern increases in soil aluminum leaching. Transport of this aluminum to acidified lakes can lead to fish mortality. Combined results from areas of silicate bedrock in the United States and Europe suggest that aluminum represents an important biogeochemical linkage between terrestrial and aquatic environments exposed to acid precipitation.",
    url = "https://doi.org/10.1126/science.204.4390.304",
    doi = "10.1126/science.204.4390.304",
    openalex = "W1999068559"
}

@article{doi1010160016703781902763,
    author = "Johnson, Noye M. and Driscoll, Charles T. and Eaton, John S. and Likens, Gene E. and McDowell, William H.",
    title = "‘Acid rain’, dissolved aluminum and chemical weathering at the Hubbard Brook Experimental Forest, New Hampshire",
    year = "1981",
    journal = "Geochimica et Cosmochimica Acta",
    url = "https://doi.org/10.1016/0016-7037(81)90276-3",
    doi = "10.1016/0016-7037(81)90276-3",
    openalex = "W2005586297"
}

@article{doi101038299548a0,
    author = "van Breemen, N. and Burrough, P.A. and Velthorst, E.J. and van Dobben, H.F. and de Wit, Toke and Ridder, T. B. and Reijnders, H. F. R.",
    title = "Soil acidification from atmospheric ammonium sulphate in forest canopy throughfall",
    year = "1982",
    journal = "Nature",
    url = "https://doi.org/10.1038/299548a0",
    doi = "10.1038/299548a0",
    openalex = "W2010723012"
}

@incollection{doi10100797894009698341,
    author = "Ulrich, B.",
    title = "A Concept of Forest Ecosystem Stability and of Acid Deposition as Driving Force for Destabilization",
    year = "1983",
    url = "https://doi.org/10.1007/978-94-009-6983-4\_1",
    doi = "10.1007/978-94-009-6983-4\_1",
    openalex = "W2225825204"
}

@article{doi1010160004698183900586,
    author = "Harte, John",
    title = "An investigation of acid precipitation in Qinghai province, China",
    year = "1983",
    journal = "Atmospheric Environment (1967)",
    url = "https://doi.org/10.1016/0004-6981(83)90058-6",
    doi = "10.1016/0004-6981(83)90058-6",
    openalex = "W2080506024"
}

@article{doi101021es00117a723,
    author = "Galloway, James N. and Norton, Stephen A. and Church, M. Robbins",
    title = "Freshwater acidification from atmospheric deposition of sulfuric acid: A conceptual model",
    year = "1983",
    journal = "Environmental Science \& Technology",
    url = "https://doi.org/10.1021/es00117a723",
    doi = "10.1021/es00117a723",
    openalex = "W1974601531"
}

Acid rain is widely believed to be responsible for acidifying soil and water in areas of North America and northern Europe. However, factors commonly considered to make landscapes susceptible to acidification by acid rain are the same factors long known to strongly acidify soils through the natural processes of soil formation. Recovery from extreme and widespread careless land use has also occurred in regions undergoing acidification. There is evidence that acidification by acid rain is superimposed on long-term acidification induced by changes in land use and consequent vegetative succession. Thus, the interactions of acid rain, acid soil, and vegetation need to be carefully examined on a watershed basis in assessing benefits expected from proposed reductions in emissions of oxides of sulfur and nitrogen.

@article{doi101126science2214610520,
    author = "Krug, Edward C. and Frink, C. R.",
    title = "Acid Rain on Acid Soil: A New Perspective",
    year = "1983",
    journal = "Science",
    abstract = "Acid rain is widely believed to be responsible for acidifying soil and water in areas of North America and northern Europe. However, factors commonly considered to make landscapes susceptible to acidification by acid rain are the same factors long known to strongly acidify soils through the natural processes of soil formation. Recovery from extreme and widespread careless land use has also occurred in regions undergoing acidification. There is evidence that acidification by acid rain is superimposed on long-term acidification induced by changes in land use and consequent vegetative succession. Thus, the interactions of acid rain, acid soil, and vegetation need to be carefully examined on a watershed basis in assessing benefits expected from proposed reductions in emissions of oxides of sulfur and nitrogen.",
    url = "https://doi.org/10.1126/science.221.4610.520",
    doi = "10.1126/science.221.4610.520",
    openalex = "W2053281725",
    references = "doi1010079781461262329, doi1010079781468401042, doi101007bf02940573, doi1010160016703781902763, doi1010970001069419411100000009, doi1010970001069419800500000002, doi101126science2044390304, doi1023071942609, doi1023072259041, openalexw2788221439"
}

@article{galloway1983freshwater,
    author = "Galloway, James N. and Norton, Stephen A. and Church, M. Robbins",
    title = "Freshwater acidification from atmospheric deposition of sulfuric acid: A conceptual model",
    year = "1983",
    journal = "Environmental Science \& Technology",
    url = "https://doi.org/10.1021/es00117a723",
    doi = "10.1021/es00117a723",
    number = "11",
    openalex = "W1974601531",
    pages = "541A-545A",
    volume = "17",
    references = "doi101007bf02419414, doi101007bf02419415, doi101021es00105a719, doi101038278542a0, doi101139f83103, openalexw1524392736"
}

Hydrogen ions in precipitation are correlated much more closely with sulfate than with nitrate, whereas ammonium ions are correlated more closely with nitrate than with sulfate. Target loadings of 14 to 16 kilograms of wet sulfate deposition per hectare per year, instead of 20 as suggested hitherto, are probably necessary to produce average pH values of 4.6 to 4.7, the approximate boundary levels for damage to aquatic ecosystems. Cluster analysis reveals that there are three linked groups of ions related to air pollution, agriculture, and sea spray.

@article{doi101126science2254660407,
    author = "Gorham, Eville and Martin, Frank B. and Litzau, Jack T.",
    title = "Acid Rain: Ionic Correlations in the Eastern United States, 1980-1981",
    year = "1984",
    journal = "Science",
    abstract = "Hydrogen ions in precipitation are correlated much more closely with sulfate than with nitrate, whereas ammonium ions are correlated more closely with nitrate than with sulfate. Target loadings of 14 to 16 kilograms of wet sulfate deposition per hectare per year, instead of 20 as suggested hitherto, are probably necessary to produce average pH values of 4.6 to 4.7, the approximate boundary levels for damage to aquatic ecosystems. Cluster analysis reveals that there are three linked groups of ions related to air pollution, agriculture, and sea spray.",
    url = "https://doi.org/10.1126/science.225.4660.407",
    doi = "10.1126/science.225.4660.407",
    openalex = "W2085999659"
}

The concentrations of H(+), SO(4)(2-), and NO(3)(-) in the precipitation of eastern North America are greater now than they were historically as a result of fossil-fuel combustion. Because of a lack of data prior to 1950, the absolute increases in the concentrations of these three ions are unknown. This problem can be addressed by comparing the composition of precipitation from areas sensitive to acidic deposition with that of precipitation from remote areas. An analysis of precipitation data indicates that many areas of eastern North America receive precipitation with substantially greater H(+), SO(4)(2-), and NO(3)(-) concentrations than remote areas. For example, SO(4)(2-), the most ecologically significant indicator of change, is enriched 2 to 16 times in eastern North American precipitation relative to its concentration in remote areas.

@article{doi101126science2264676829,
    author = "Galloway, James N. and Likens, Gene E. and Hawley, Mark E.",
    title = "Acid Precipitation: Natural Versus Anthropogenic Components",
    year = "1984",
    journal = "Science",
    abstract = "The concentrations of H(+), SO(4)(2-), and NO(3)(-) in the precipitation of eastern North America are greater now than they were historically as a result of fossil-fuel combustion. Because of a lack of data prior to 1950, the absolute increases in the concentrations of these three ions are unknown. This problem can be addressed by comparing the composition of precipitation from areas sensitive to acidic deposition with that of precipitation from remote areas. An analysis of precipitation data indicates that many areas of eastern North America receive precipitation with substantially greater H(+), SO(4)(2-), and NO(3)(-) concentrations than remote areas. For example, SO(4)(2-), the most ecologically significant indicator of change, is enriched 2 to 16 times in eastern North American precipitation relative to its concentration in remote areas.",
    url = "https://doi.org/10.1126/science.226.4676.829",
    doi = "10.1126/science.226.4676.829",
    openalex = "W2075436552"
}

(1) Multiple regression analysis was applied to single-event samples of throughfall beneath oak trees to separate the contributions of dry deposition and canopy exchange to the net deposition (throughfall minus precipitation). (2) Results for chestnut oak (Quercusprinus L.) in the growing season indicate that 62 and 42% of the net deposition of SO2and Ca2+, respectively, were supplied by canopy exchange, with the remainder being washed-off dry deposition. For white oak (Quercus alba L.), the corresponding values were 81 and 73%. (3) Dry deposition accounted for 30 and 71% of the total atmospheric input of SO2and Ca2+, respectively. (4) For nitrate, dry deposition was at least 30% of the total atmospheric input, but some uptake of both wet and dry deposition probably occurred in the canopy. (5) For potassium, much of the measured dry deposition appeared to be particulate material released and redeposited within the canopy. (6) Wet deposition dominated the throughfall flux of sulphate and nitrate, but dry deposition dominated that for Ca2+ and canopy exchange dominated that for K+.

@article{doi1023072405064,
    author = "Lovett, Gary M. and Lindbeŕg, Steven E.",
    title = "Dry Deposition and Canopy Exchange in a Mixed Oak Forest as Determined by Analysis of Throughfall",
    year = "1984",
    journal = "Journal of Applied Ecology",
    abstract = "(1) Multiple regression analysis was applied to single-event samples of throughfall beneath oak trees to separate the contributions of dry deposition and canopy exchange to the net deposition (throughfall minus precipitation). (2) Results for chestnut oak (Quercusprinus L.) in the growing season indicate that 62 and 42\% of the net deposition of SO2and Ca2+, respectively, were supplied by canopy exchange, with the remainder being washed-off dry deposition. For white oak (Quercus alba L.), the corresponding values were 81 and 73\%. (3) Dry deposition accounted for 30 and 71\% of the total atmospheric input of SO2and Ca2+, respectively. (4) For nitrate, dry deposition was at least 30\% of the total atmospheric input, but some uptake of both wet and dry deposition probably occurred in the canopy. (5) For potassium, much of the measured dry deposition appeared to be particulate material released and redeposited within the canopy. (6) Wet deposition dominated the throughfall flux of sulphate and nitrate, but dry deposition dominated that for Ca2+ and canopy exchange dominated that for K+.",
    url = "https://doi.org/10.2307/2405064",
    doi = "10.2307/2405064",
    openalex = "W2330556845"
}

Quantitative predictions of the effects of acid deposition onterrestrial and aquatic systems require physically based, process‐oriented models of catchment soil water and streamwater chemistry. A desirable characteristic of such models is that they include terms to describe the important phenomena controlling a system's chemical response to acidic deposition, yet be restricted in complexity so that they can be implemented on diverse systems with a minimum of a priori data. We present an assessment of a conceptual model of soil water and streamwater chemistry based on soil cation exchange, dissolution of aluminum hydroxide, and solution of carbon dioxide, all processes that occur in catchment soils and that have rapid equilibration times. The model is constructed using an “average” or lumped representation of these spatially distributed catchment processes. The adequacy of the model is assessed by applying it to 3 years of soil water and streamwater chemistry data from White Oak Run, Virginia, a second‐order stream in the Shenandoah National Park. Soil properties predicted by the model are in good agreement with presently available measurements of those soil properties. The success of the model suggests that lumped representations of complex and spatially distributed chemical reactions in soils can efficiently describe the gross chemical behavior of whole catchments (e.g., p H, alkalinity, and major ionic concentrations in surface waters). Further assessment of the adequacy of this conceptual approach will require more detailed empirical knowledge of the soil processes being modeled, particularly soil cation exchange and the variability of soil CO 2 partial pressures.

@article{doi101029wr021i001p00051,
    author = "Cosby, B. J. and Hornberger, George M. and Galloway, James N. and Wright, Richard F.",
    title = "Modeling the Effects of Acid Deposition: Assessment of a Lumped Parameter Model of Soil Water and Streamwater Chemistry",
    year = "1985",
    journal = "Water Resources Research",
    abstract = "Quantitative predictions of the effects of acid deposition onterrestrial and aquatic systems require physically based, process‐oriented models of catchment soil water and streamwater chemistry. A desirable characteristic of such models is that they include terms to describe the important phenomena controlling a system's chemical response to acidic deposition, yet be restricted in complexity so that they can be implemented on diverse systems with a minimum of a priori data. We present an assessment of a conceptual model of soil water and streamwater chemistry based on soil cation exchange, dissolution of aluminum hydroxide, and solution of carbon dioxide, all processes that occur in catchment soils and that have rapid equilibration times. The model is constructed using an “average” or lumped representation of these spatially distributed catchment processes. The adequacy of the model is assessed by applying it to 3 years of soil water and streamwater chemistry data from White Oak Run, Virginia, a second‐order stream in the Shenandoah National Park. Soil properties predicted by the model are in good agreement with presently available measurements of those soil properties. The success of the model suggests that lumped representations of complex and spatially distributed chemical reactions in soils can efficiently describe the gross chemical behavior of whole catchments (e.g., p H, alkalinity, and major ionic concentrations in surface waters). Further assessment of the adequacy of this conceptual approach will require more detailed empirical knowledge of the soil processes being modeled, particularly soil cation exchange and the variability of soil CO 2 partial pressures.",
    url = "https://doi.org/10.1029/wr021i001p00051",
    doi = "10.1029/wr021i001p00051",
    openalex = "W2083991228",
    references = "doi1010079781461344520, doi1010079781461567615, doi1010160016003250904364, doi1010160016703781902763, doi101021ja01250a059, doi101021ja01851a058, doi101038scientificamerican107943, doi10106311698996, doi101126science2214610520, galloway1983freshwater, openalexw1486416230"
}

@article{doi101038317027a0,
    author = "Calvert, Jack G. and Lazrus, A. L. and Kok, Gregory L. and Heikes, Brian G. and Walega, J. and Lind, John A. and Cantrell, C. A.",
    title = "Chemical mechanisms of acid generation in the troposphere",
    year = "1985",
    journal = "Nature",
    url = "https://doi.org/10.1038/317027a0",
    doi = "10.1038/317027a0",
    openalex = "W2034643367",
    references = "doi101038scientificamerican107943"
}

@book{doi1010079781441985361,
    author = "Reuss, J. O. and Johnson, D. W.",
    title = "Acid Deposition and the Acidification of Soils and Waters",
    year = "1986",
    booktitle = "Ecological studies",
    url = "https://doi.org/10.1007/978-1-4419-8536-1",
    doi = "10.1007/978-1-4419-8536-1",
    openalex = "W1579071281"
}

Coal combustion is the primary contributor to atmospheric pollution in China, especially so In big cities. Particulate matter and sulfur dioxide are the two main pollutants worthy of attention. Concentration of suspended particles is usually higher in northern cities than in southern cities and higher in winter than in summer. In the case of sulfur dioxide, concentrations are high in the heating season (wintertime) in northern cities, but also in some of the cities in the southwest part of China. Rainfall with pH less than 5.6 occurs mostly to the south of the Yangtze River, especially so in the cities of Chongqing and Gueiyang, and their neighboring areas, and also In the southwest part of China. No acid rain, however, has been found in Beijing and Tianjin. Although the formation of acid rain can thus be thought of as dependent on the presence of enough sulfur dioxide, other factors such as airborne particles and ammonia also play an important role. The difference is, therefore, explained and theorem postulated with supporting data. Ways of abating atmospheric pollution are, in essence, related to improved coal burning; some simple methods are suggested for nationwide control options.

@article{doi10108000022470198610466074,
    author = "Zhao, Dianwu and Sun, Bozen",
    title = "Atmospheric Pollution from Coal Combustion in China",
    year = "1986",
    journal = "Journal of the Air Pollution Control Association",
    abstract = "Coal combustion is the primary contributor to atmospheric pollution in China, especially so In big cities. Particulate matter and sulfur dioxide are the two main pollutants worthy of attention. Concentration of suspended particles is usually higher in northern cities than in southern cities and higher in winter than in summer. In the case of sulfur dioxide, concentrations are high in the heating season (wintertime) in northern cities, but also in some of the cities in the southwest part of China. Rainfall with pH less than 5.6 occurs mostly to the south of the Yangtze River, especially so in the cities of Chongqing and Gueiyang, and their neighboring areas, and also In the southwest part of China. No acid rain, however, has been found in Beijing and Tianjin. Although the formation of acid rain can thus be thought of as dependent on the presence of enough sulfur dioxide, other factors such as airborne particles and ammonia also play an important role. The difference is, therefore, explained and theorem postulated with supporting data. Ways of abating atmospheric pollution are, in essence, related to improved coal burning; some simple methods are suggested for nationwide control options.",
    url = "https://doi.org/10.1080/00022470.1986.10466074",
    doi = "10.1080/00022470.1986.10466074",
    openalex = "W1965490667"
}

Airborne particles and vapors contributed significantly to the nutrient requirements and the pollutant load of a mixed hardwood forest in the eastern United States. Dry deposition was an important mechanism of atmospheric input to the foliar canopy, occurring primarily by vapor uptake for sulfur, nitrogen, and free acidity and by particle deposition for calcium and potassium. The canopy retained 50 to 70 percent of the deposited free acidity and nitrogen, but released calcium and potassium. Atmospheric deposition supplied 40 and 100 percent of the nitrogen and sulfur requirements, respectively, for the annual woody increment. This contribution was underestimated significantly by standard bulk deposition collectors.

@article{doi101126science2314734141,
    author = "Lindbeŕg, Steven E. and Lovett, Gary M. and Richter, Daniel D. and Johnson, Dale W.",
    title = "Atmospheric Deposition and Canopy Interactions of Major Ions in a Forest",
    year = "1986",
    journal = "Science",
    abstract = "Airborne particles and vapors contributed significantly to the nutrient requirements and the pollutant load of a mixed hardwood forest in the eastern United States. Dry deposition was an important mechanism of atmospheric input to the foliar canopy, occurring primarily by vapor uptake for sulfur, nitrogen, and free acidity and by particle deposition for calcium and potassium. The canopy retained 50 to 70 percent of the deposited free acidity and nitrogen, but released calcium and potassium. Atmospheric deposition supplied 40 and 100 percent of the nitrogen and sulfur requirements, respectively, for the annual woody increment. This contribution was underestimated significantly by standard bulk deposition collectors.",
    url = "https://doi.org/10.1126/science.231.4734.141",
    doi = "10.1126/science.231.4734.141",
    openalex = "W1971806884"
}

@article{openalexw168580091,
    author = "Zhao, Dianwu and Sun, Bozen",
    title = "Air pollution and acid rain in China",
    year = "1986",
    journal = "AMBIO",
    openalex = "W168580091"
}

@misc{crutzen1987acid1,
    author = "Crutzen, P",
    title = "Acid rain at the K/T boundry",
    year = "1987",
    howpublished = "Nature, v. 330, p. 108-109",
    note = "talkorigins\_source = {true}; raw\_reference = {Crutzen, P., 1987, Acid rain at the K/T boundry: Nature, v. 330, p. 108-109.}"
}

Wet‐only rain samples were collected and chemically analyzed during 1980–1984 at Katherine, Australia, as part of the Global Precipitation Chemistry Project. Rainfall averaged 104 cm/yr and ranged from 74.6 cm in 1982–1983 to 135.7 cm in 1983–1984. Total cation concentration was about 29 μeq/L. The volume‐weighted mean H + concentration expressed as p H was 4.73, 64% of the free acidity was due to organic acids (formic and acetic). The p H due to strong mineral acids only was 5.08. Air mass trajectories during the wet season were predominantly from the northeast (51%), and this trajectory was most important in terms of deposition. Although there is a high frequency of lightning during the wet season, no evidence was found that it contributed significantly to the nitrate concentration in rain. Because concentrations decreased markedly with amount of precipitation, the total deposition of dissolved substances was not correlated directly with the amount of rain. Comparisons were made between the chemistry of rain at Katherine and with other remote areas and with the eastern United States.

@article{doi101029jd092id11p13299,
    author = "Likens, Gene E. and Keene, W. C. and Miller, John M. and Galloway, James N.",
    title = "Chemistry of precipitation from a remote, terrestrial site in Australia",
    year = "1987",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Wet‐only rain samples were collected and chemically analyzed during 1980–1984 at Katherine, Australia, as part of the Global Precipitation Chemistry Project. Rainfall averaged 104 cm/yr and ranged from 74.6 cm in 1982–1983 to 135.7 cm in 1983–1984. Total cation concentration was about 29 μeq/L. The volume‐weighted mean H + concentration expressed as p H was 4.73, 64\% of the free acidity was due to organic acids (formic and acetic). The p H due to strong mineral acids only was 5.08. Air mass trajectories during the wet season were predominantly from the northeast (51\%), and this trajectory was most important in terms of deposition. Although there is a high frequency of lightning during the wet season, no evidence was found that it contributed significantly to the nitrate concentration in rain. Because concentrations decreased markedly with amount of precipitation, the total deposition of dissolved substances was not correlated directly with the amount of rain. Comparisons were made between the chemistry of rain at Katherine and with other remote areas and with the eastern United States.",
    url = "https://doi.org/10.1029/jd092id11p13299",
    doi = "10.1029/jd092id11p13299",
    openalex = "W2071267535"
}

The composition of precipitation in China is highly influenced by fossil fuel combustion and agricultural and cultural practices. Compared to the eastern United States, precipitation in China generally has higher concentrations of sulfate, ammonium, and calcium. Wet deposition rates of sulfur in China are 7 to 130 times higher than those in a remote area in the Southern Hemisphere. In many areas of the world, significant ecological changes have occurred in ecosystems that have acid deposition rates substantially less than those currently existing in China.

@article{doi101126science23648081559,
    author = "Galloway, James N. and Dian-wu, Zhao and Jiling, Xiong and Likens, Gene E.",
    title = "Acid Rain: China, United States, and a Remote Area",
    year = "1987",
    journal = "Science",
    abstract = "The composition of precipitation in China is highly influenced by fossil fuel combustion and agricultural and cultural practices. Compared to the eastern United States, precipitation in China generally has higher concentrations of sulfate, ammonium, and calcium. Wet deposition rates of sulfur in China are 7 to 130 times higher than those in a remote area in the Southern Hemisphere. In many areas of the world, significant ecological changes have occurred in ecosystems that have acid deposition rates substantially less than those currently existing in China.",
    url = "https://doi.org/10.1126/science.236.4808.1559",
    doi = "10.1126/science.236.4808.1559",
    openalex = "W1971704780",
    references = "doi1010079781441985361, doi1010079781461330332, doi1010160004698183900586, doi101029jd092id11p13299, doi10108000022470198610466074, doi1010970001069419230300000004, doi101126science2254660407, doi101126science2264676829, galloway1983freshwater, openalexw168580091"
}

@article{doi1010160004698188900406,
    author = "Dianwu, Zhao and Jiling, Xiong and Xu, Yu and Chan, Walter H.",
    title = "Acid rain in southwestern China",
    year = "1988",
    journal = "Atmospheric Environment (1967)",
    url = "https://doi.org/10.1016/0004-6981(88)90040-6",
    doi = "10.1016/0004-6981(88)90040-6",
    openalex = "W1974719690"
}

Acid-vulnerable areas are more numerous and widespread than believed 7 years ago. Lakes and streams in acid-vulnerable areas of northeastern North America have suffered substantial declines in acid-neutralizing capacity, the worst cases resulting in biological damage. Many invertebrates are very sensitive to acidification, with some disappearing at pH values as high as 6.0. However, the recent rate of acidification of lakes is slower than once predicted, in part the result of decreases in sulfur oxide emissions. A discussion of some of the processes that have contributed to the acidification of lakes as well as those that have protected acid-sensitive freshwaters is presented. The author is in the Department of Fisheries and Oceans, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada.

@article{doi101126science2394836149,
    author = "Schindler, D. W.",
    title = "Effects of Acid Rain on Freshwater Ecosystems",
    year = "1988",
    journal = "Science",
    abstract = "Acid-vulnerable areas are more numerous and widespread than believed 7 years ago. Lakes and streams in acid-vulnerable areas of northeastern North America have suffered substantial declines in acid-neutralizing capacity, the worst cases resulting in biological damage. Many invertebrates are very sensitive to acidification, with some disappearing at pH values as high as 6.0. However, the recent rate of acidification of lakes is slower than once predicted, in part the result of decreases in sulfur oxide emissions. A discussion of some of the processes that have contributed to the acidification of lakes as well as those that have protected acid-sensitive freshwaters is presented. The author is in the Department of Fisheries and Oceans, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada.",
    url = "https://doi.org/10.1126/science.239.4836.149",
    doi = "10.1126/science.239.4836.149",
    openalex = "W2073974376",
    references = "doi101007bf02505178, doi1010160004698186901800, doi101029jc087ic11p08771, doi101029wr021i001p00051, doi101038279409a0, doi101038284161a0, doi101126science18441421176, doi101126science2214610520, doi101126science23648081559, doi1023071942440, doi1023072256395, doi1023072256691, openalexw168580091"
}

@incollection{doi10100797894009092368,
    author = "Bredemeier, Michael",
    title = "Forest Canopy Transformation of Atmospheric Deposition",
    year = "1989",
    url = "https://doi.org/10.1007/978-94-009-0923-6\_8",
    doi = "10.1007/978-94-009-0923-6\_8",
    openalex = "W1510511433",
    references = "doi1010079789400969834, doi10100797894009698341, doi10100797894009698342, doi101007bf00390660, doi101007bf02197866, doi1010160004698178902287, doi101126science2314734141, doi101146annurevpp05060154000335, doi1023072405064, openalexw1549689101"
}

@article{doi101016096016869090252i,
    author = "Lindbeŕg, Steven E. and Bredemeier, Michael and Schaefer, Douglas and Qi, Lijuan",
    title = "Atmospheric concentrations and deposition of nitrogen and major ions in conifer forests in the United States and Federal Republic of Germany",
    year = "1990",
    journal = "Atmospheric Environment Part A General Topics",
    url = "https://doi.org/10.1016/0960-1686(90)90252-i",
    doi = "10.1016/0960-1686(90)90252-i",
    openalex = "W1968614412"
}

@book{openalexw3133631291,
    author = "Bright, Michael",
    title = "Acid Rain",
    year = "1991",
    url = "https://openalex.org/W3133631291",
    openalex = "W3133631291"
}

A complementary DNA encoding a salicylic acid (SA)-binding protein has been cloned. Its properties suggest involvement in SA-mediated induction of systemic acquired resistance (SAR) in plants. The sequence of the protein is similar to that of catalases and the protein exhibits catalase activity. Salicylic acid specifically inhibited the catalase activity in vitro and induced an increase in H2O2 concentrations in vivo. H2O2 or compounds, such as SA, that inhibit catalases or enhance the generation of H2O2, induced expression of defense-related genes associated with SAR. Thus, the action of SA in SAR is likely mediated by elevated amounts of H2O2.

@article{doi101126science8266079,
    author = "Chen, Zhixiang and Silva, Hermán and Klessig, Daniel F.",
    title = "Active Oxygen Species in the Induction of Plant Systemic Acquired Resistance by Salicylic Acid",
    year = "1993",
    journal = "Science",
    abstract = "A complementary DNA encoding a salicylic acid (SA)-binding protein has been cloned. Its properties suggest involvement in SA-mediated induction of systemic acquired resistance (SAR) in plants. The sequence of the protein is similar to that of catalases and the protein exhibits catalase activity. Salicylic acid specifically inhibited the catalase activity in vitro and induced an increase in H2O2 concentrations in vivo. H2O2 or compounds, such as SA, that inhibit catalases or enhance the generation of H2O2, induced expression of defense-related genes associated with SAR. Thus, the action of SA in SAR is likely mediated by elevated amounts of H2O2.",
    url = "https://doi.org/10.1126/science.8266079",
    doi = "10.1126/science.8266079",
    openalex = "W2061954020"
}

Wet deposition of nitrogen compounds was measured and dry and cloud water deposition were estimated at 11 forested sites in North America and one site in Europe. Dry deposition was a significant pathway of N input to all the forests, averaging 46% of the total deposition. At most of these sites, NH 4 + was the dominant form of fixed N in the air, but HNO 3 vapor dominated the dry deposition of N. Coarse-particle deposition was often important, but fine-particle deposition usually contributed only a small amount of the dry-deposited N. The deposition rates of inorganic N, which ranged between 4.8 and 27 kg N•ha −1 •year −1, were generally much higher than has been reported by other studies measuring only wet or bulk deposition. The highest deposition rates were at the high-elevation sites in the southeastern and northeastern United States and much of the deposition at these sites was attributed to cloud water. Throughfall and stemflow (TF + SF) flux was also measured at all sites, and the net canopy exchange (NCE = (TF + SF)–total deposition) was found to be negative (indicating consumption of N in the canopy) for NH 4 + and NO 3 −, and positive (indicating canopy release) for organic N. Past reports of canopy release of NO 3 − can probably be attributed to washoff of dry-deposited NO 3 − species. Consumption of inorganic N in the canopy ranged from 1 to 12 kg N•ha −1 •year −1, and was highest in the spruce and spruce–fir stands. When organic N was included in the canopy N balance, the net canopy uptake of N was generally < 15% of the total system N requirement. Total N deposition was a linear function of wet deposition for low-elevation sites, and dry deposition was a linear function of the net throughfall flux for NO 3 −.

@article{doi101139x93200,
    author = "Lovett, Gary M. and Lindbeŕg, Steven E.",
    title = "Atmospheric deposition and canopy interactions of nitrogen in forests",
    year = "1993",
    journal = "Canadian Journal of Forest Research",
    abstract = "Wet deposition of nitrogen compounds was measured and dry and cloud water deposition were estimated at 11 forested sites in North America and one site in Europe. Dry deposition was a significant pathway of N input to all the forests, averaging 46\% of the total deposition. At most of these sites, NH 4 + was the dominant form of fixed N in the air, but HNO 3 vapor dominated the dry deposition of N. Coarse-particle deposition was often important, but fine-particle deposition usually contributed only a small amount of the dry-deposited N. The deposition rates of inorganic N, which ranged between 4.8 and 27 kg N•ha −1 •year −1, were generally much higher than has been reported by other studies measuring only wet or bulk deposition. The highest deposition rates were at the high-elevation sites in the southeastern and northeastern United States and much of the deposition at these sites was attributed to cloud water. Throughfall and stemflow (TF + SF) flux was also measured at all sites, and the net canopy exchange (NCE = (TF + SF)–total deposition) was found to be negative (indicating consumption of N in the canopy) for NH 4 + and NO 3 −, and positive (indicating canopy release) for organic N. Past reports of canopy release of NO 3 − can probably be attributed to washoff of dry-deposited NO 3 − species. Consumption of inorganic N in the canopy ranged from 1 to 12 kg N•ha −1 •year −1, and was highest in the spruce and spruce–fir stands. When organic N was included in the canopy N balance, the net canopy uptake of N was generally < 15\% of the total system N requirement. Total N deposition was a linear function of wet deposition for low-elevation sites, and dry deposition was a linear function of the net throughfall flux for NO 3 −.",
    url = "https://doi.org/10.1139/x93-200",
    doi = "10.1139/x93-200",
    openalex = "W1968744913"
}

Research on air pollution and acidic deposition during the last 15 yr has greatly increased our knowledge of the rates and the processes of atmospheric deposition. The invigoration of the field has been a direct result of interchange and cooperation among ecosystem ecologists, micrometeorologists, and plant physiological ecologists who each approach the study of atmospheric deposition from different perspectives. This has led to the widespread realization among ecologists of the importance of dry and cloud deposition and the introduction of new methods to estimate these fluxes. In this paper I summarize the current understanding of atmospheric deposition processes, measurement methods, and patterns of deposition in North America. Dry deposition measurements are still highly uncertain in most cases, and methodology is still an active area of research and debate, but it seems clear that ecologists will require a suite of different methods to evaluate dry deposition fluxes of the various elements important to ecosystems. Standard model formulations have been developed for estimating dry and cloud deposition, and these models are finding wide use in flux estimation at sites where direct measurements are unavailable. National monitoring networks for wet and dry deposition have been established and are providing information on continental— and regional—scale patterns. Research has demonstrated that deposition rates are increased substantially at high—elevation sites by enhancement of wet, dry, and especially, cloud deposition. Patterns of O 3 exposure are also different at high—elevation sites. The deposition of O 3, while mechanistically similar to that of other gases, has been treated differently in the ecological and botanical literature because of its direct phytotoxicity at ambient concentrations in industrialized areas. Current efforts in ozone exposure research involve determining appropriate exposure indices for interpreting biological responses and coupling models of atmospheric transport with models of ozone disposition within the plant.

@article{doi1023071941997,
    author = "Lovett, Gary M.",
    title = "Atmospheric Deposition of Nutrients and Pollutants in North America: An Ecological Perspective",
    year = "1994",
    journal = "Ecological Applications",
    abstract = "Research on air pollution and acidic deposition during the last 15 yr has greatly increased our knowledge of the rates and the processes of atmospheric deposition. The invigoration of the field has been a direct result of interchange and cooperation among ecosystem ecologists, micrometeorologists, and plant physiological ecologists who each approach the study of atmospheric deposition from different perspectives. This has led to the widespread realization among ecologists of the importance of dry and cloud deposition and the introduction of new methods to estimate these fluxes. In this paper I summarize the current understanding of atmospheric deposition processes, measurement methods, and patterns of deposition in North America. Dry deposition measurements are still highly uncertain in most cases, and methodology is still an active area of research and debate, but it seems clear that ecologists will require a suite of different methods to evaluate dry deposition fluxes of the various elements important to ecosystems. Standard model formulations have been developed for estimating dry and cloud deposition, and these models are finding wide use in flux estimation at sites where direct measurements are unavailable. National monitoring networks for wet and dry deposition have been established and are providing information on continental— and regional—scale patterns. Research has demonstrated that deposition rates are increased substantially at high—elevation sites by enhancement of wet, dry, and especially, cloud deposition. Patterns of O 3 exposure are also different at high—elevation sites. The deposition of O 3, while mechanistically similar to that of other gases, has been treated differently in the ecological and botanical literature because of its direct phytotoxicity at ambient concentrations in industrialized areas. Current efforts in ozone exposure research involve determining appropriate exposure indices for interpreting biological responses and coupling models of atmospheric transport with models of ozone disposition within the plant.",
    url = "https://doi.org/10.2307/1941997",
    doi = "10.2307/1941997",
    openalex = "W2003099721"
}

@article{doi101007bf01186176,
    author = "Wang, Wenxing and Wang, Tao",
    title = "On the origin and the trend of acid precipitation in China",
    year = "1995",
    journal = "Water Air \& Soil Pollution",
    url = "https://doi.org/10.1007/bf01186176",
    doi = "10.1007/bf01186176",
    openalex = "W1976657310"
}

@article{doi101016135223109600115x,
    author = "Wang, Wenxing and Wang, Tao",
    title = "On acid rain formation in China",
    year = "1996",
    journal = "Atmospheric Environment",
    url = "https://doi.org/10.1016/1352-2310(96)00115-x",
    doi = "10.1016/1352-2310(96)00115-x",
    openalex = "W2160280933"
}

Long-term data from the Hubbard Brook Experimental Forest, New Hampshire, suggest that although changes in stream pH have been relatively small, large quantities of calcium and magnesium have been lost from the soil complex and exported by drainage water because of inputs of acid rain and declines in atmospheric deposition of base cations. As a result, the recovery of soil and streamwater chemistry in response to any decreases in acid deposition will be delayed significantly.

@article{doi101126science2725259244,
    author = "Likens, Gene E. and Driscoll, Charles T. and Buso, D. C.",
    title = "Long-Term Effects of Acid Rain: Response and Recovery of a Forest Ecosystem",
    year = "1996",
    journal = "Science",
    abstract = "Long-term data from the Hubbard Brook Experimental Forest, New Hampshire, suggest that although changes in stream pH have been relatively small, large quantities of calcium and magnesium have been lost from the soil complex and exported by drainage water because of inputs of acid rain and declines in atmospheric deposition of base cations. As a result, the recovery of soil and streamwater chemistry in response to any decreases in acid deposition will be delayed significantly.",
    url = "https://doi.org/10.1126/science.272.5259.244",
    doi = "10.1126/science.272.5259.244",
    openalex = "W2084337353",
    references = "doi1010079781461242321, doi101007bf00000881, doi101007bf01874965, doi101029wr010i006p01133, doi101038362438a0, doi101038367351a0, doi101038scientificamerican107943, doi1011751520046919580150417tcocsp20co2, doi102134jeq199500472425002400020002x, doi105860choice516175"
}

@article{doi101016s1462901198000434,
    author = "Larssen, Thorjørn and Seip, Hans M. and Semb, Arne and Mulder, Jan and Muniz, I. P. and Vogt, Rolf D. and Lydersen, Espen and Angell, Valter and Dagang, Tang and Eilertsen, Odd",
    title = "Acid deposition and its effects in China: an overview",
    year = "1999",
    journal = "Environmental Science \& Policy",
    url = "https://doi.org/10.1016/s1462-9011(98)00043-4",
    doi = "10.1016/s1462-9011(98)00043-4",
    openalex = "W2055445016",
    references = "openalexw168580091"
}

@article{doi101016s0168945299001971,
    author = "Velikova, Violeta and Yordanov, I. and Edreva, A.",
    title = "Oxidative stress and some antioxidant systems in acid rain-treated bean plants",
    year = "2000",
    journal = "Plant Science",
    url = "https://doi.org/10.1016/s0168-9452(99)00197-1",
    doi = "10.1016/s0168-9452(99)00197-1",
    openalex = "W2111444582",
    references = "doi101006abio19769999, doi1010160003269776905273, doi1010160003986168906541, doi101016s0021925819838425, doi101016s0304423896009223, doi101105tpc971031, doi101111j139930541991tb00121x, doi101111j139930541997tb04780x, doi101126science8266079, doi1012019781003574927"
}

@article{doi101016s0269749199002791,
    author = "Larssen, Thorjørn and Carmichael, Gregory R.",
    title = "Acid rain and acidification in China: the importance of base cation deposition",
    year = "2000",
    journal = "Environmental Pollution",
    url = "https://doi.org/10.1016/s0269-7491(99)00279-1",
    doi = "10.1016/s0269-7491(99)00279-1",
    openalex = "W2047004203",
    references = "doi101029wr021i001p00051"
}

@article{larssen2000acid,
    author = "Larssen, T. and Carmichael, G.R.",
    title = "Acid rain and acidification in China: the importance of base cation deposition",
    year = "2000",
    journal = "Environmental Pollution",
    url = "https://doi.org/10.1016/s0269-7491(99)00279-1",
    doi = "10.1016/s0269-7491(99)00279-1",
    number = "1",
    openalex = "W2047004203",
    pages = "89-102",
    volume = "110",
    references = "doi101007bf01186176, doi101007bf01257121, doi1010160004698188900406, doi101016135223109600115x, doi101016s1352231096002361, doi101016s1462901198000434, doi101029wr021i001p00051, doi101038367351a0, doi102134jeq199500472425002400020002x, openalexw168580091"
}

The location and mechanisms responsible for the carbon sink in northern mid-latitude lands are uncertain. Here, we used an improved estimation method of forest biomass and a 50-year national forest resource inventory in China to estimate changes in the storage of living biomass between 1949 and 1998. Our results suggest that Chinese forests released about 0.68 petagram of carbon between 1949 and 1980, for an annual emission rate of 0.022 petagram of carbon. Carbon storage increased significantly after the late 1970s from 4.38 to 4.75 petagram of carbon by 1998, for a mean accumulation rate of 0.021 petagram of carbon per year, mainly due to forest expansion and regrowth. Since the mid-1970s, planted forests (afforestation and reforestation) have sequestered 0.45 petagram of carbon, and their average carbon density increased from 15.3 to 31.1 megagrams per hectare, while natural forests have lost an additional 0.14 petagram of carbon, suggesting that carbon sequestration through forest management practices addressed in the Kyoto Protocol could help offset industrial carbon dioxide emissions.

@article{doi101126science1058629,
    author = "Fang, Jingyun and Chen, Anping and Peng, Changhui and Zhao, Shuqing and Ci, Longjun",
    title = "Changes in Forest Biomass Carbon Storage in China Between 1949 and 1998",
    year = "2001",
    journal = "Science",
    abstract = "The location and mechanisms responsible for the carbon sink in northern mid-latitude lands are uncertain. Here, we used an improved estimation method of forest biomass and a 50-year national forest resource inventory in China to estimate changes in the storage of living biomass between 1949 and 1998. Our results suggest that Chinese forests released about 0.68 petagram of carbon between 1949 and 1980, for an annual emission rate of 0.022 petagram of carbon. Carbon storage increased significantly after the late 1970s from 4.38 to 4.75 petagram of carbon by 1998, for a mean accumulation rate of 0.021 petagram of carbon per year, mainly due to forest expansion and regrowth. Since the mid-1970s, planted forests (afforestation and reforestation) have sequestered 0.45 petagram of carbon, and their average carbon density increased from 15.3 to 31.1 megagrams per hectare, while natural forests have lost an additional 0.14 petagram of carbon, suggesting that carbon sequestration through forest management practices addressed in the Kyoto Protocol could help offset industrial carbon dioxide emissions.",
    url = "https://doi.org/10.1126/science.1058629",
    doi = "10.1126/science.1058629",
    openalex = "W2047744778"
}

Abstract. The MAGIC model of the responses of catchments to acidic deposition has been applied and tested extensively over a 15 year period at many sites and in many regions around the world. Overall, the model has proven to be robust, reliable and useful in a variety of scientific and managerial activities. Over the years, several refinements and additions to MAGIC have been proposed and/or implemented for particular applications. These adjustments to the model structure have all been included in a new version of the model (MAGIC7). The log aluminium – pH relationship now does not have to be fixed to aluminium trihydroxide solubility. Buffering by organic acids using a triprotic analog is now included. Dynamics of nitrogen retention and loss in catchments can now be linked to soil nitrogen and carbon pools. Simulation of short-term episodic response by mixing fractions of different water types is also possible. This paper presents a review of the conceptual structure of MAGIC7 relating to long-term simulation of acidification and recovery, describes the conceptual basis of the new nitrogen dynamics and provides a comprehensive update of the equations, variables, parameters and inputs for the model. Keywords: process-based model, acid deposition, recovery

@article{doi105194hess54992001,
    author = "Cosby, B. J. and Ferrier, Robert C. and Jenkins, A. and Wright, Richard F.",
    title = "Modelling the effects of acid deposition: refinements, adjustments and inclusion of nitrogen dynamics in the MAGIC model",
    year = "2001",
    journal = "Hydrology and earth system sciences",
    abstract = "Abstract. The MAGIC model of the responses of catchments to acidic deposition has been applied and tested extensively over a 15 year period at many sites and in many regions around the world. Overall, the model has proven to be robust, reliable and useful in a variety of scientific and managerial activities. Over the years, several refinements and additions to MAGIC have been proposed and/or implemented for particular applications. These adjustments to the model structure have all been included in a new version of the model (MAGIC7). The log aluminium – pH relationship now does not have to be fixed to aluminium trihydroxide solubility. Buffering by organic acids using a triprotic analog is now included. Dynamics of nitrogen retention and loss in catchments can now be linked to soil nitrogen and carbon pools. Simulation of short-term episodic response by mixing fractions of different water types is also possible. This paper presents a review of the conceptual structure of MAGIC7 relating to long-term simulation of acidification and recovery, describes the conceptual basis of the new nitrogen dynamics and provides a comprehensive update of the equations, variables, parameters and inputs for the model. Keywords: process-based model, acid deposition, recovery",
    url = "https://doi.org/10.5194/hess-5-499-2001",
    doi = "10.5194/hess-5-499-2001",
    openalex = "W2028787241",
    references = "doi1010079781441985361, doi1010160016703783902181, doi101016037811279406092w, doi101016s0378112797001242, doi101021cenv034n034p4017, doi101029wr021i001p00051, doi10106311698996, doi101126science2635147641, doi1023071941889, openalexw2275862880"
}

Concern is resurfacing in the United States over the long-term effects of excess nitrogen (N) deposition and mobility in the environment. We present here a new synthesis of existing data sets for the northeastern United States, intended to answer a single question: Is N deposition altering the N status of forest ecosystems in this region? Surface water data suggest a significant increase in nitrate losses with N deposition. Soil data show an increase in nitrification with decreasing ratio of soil carbon to nitrogen (C:N) but weaker relationships between N deposition and soil C:N ratio or nitrification. Relationships between foliar chemistry and N deposition are no stronger than with gradients of climate and elevation. The differences in patterns for these three groups of indicators are explained by the degree of spatial and temporal integration represented by each sample type. The surface water data integrate more effectively over space than the foliar or soil data and therefore allow a more comprehensive view of N saturation. We conclude from these data that N deposition is altering N status in northeastern forests.

@article{doi1016410006356820030530375indatn20co2,
    author = "Aber, John D. and Goodale, Christine L. and Ollinger, Scott V. and Smith, Marie-Louise and Magill, Alison H. and Martin, Mary E. and Hallett, Richard A. and Stoddard, John L.",
    title = "Is Nitrogen Deposition Altering the Nitrogen Status of Northeastern Forests?",
    year = "2003",
    journal = "BioScience",
    abstract = "Concern is resurfacing in the United States over the long-term effects of excess nitrogen (N) deposition and mobility in the environment. We present here a new synthesis of existing data sets for the northeastern United States, intended to answer a single question: Is N deposition altering the N status of forest ecosystems in this region? Surface water data suggest a significant increase in nitrate losses with N deposition. Soil data show an increase in nitrification with decreasing ratio of soil carbon to nitrogen (C:N) but weaker relationships between N deposition and soil C:N ratio or nitrification. Relationships between foliar chemistry and N deposition are no stronger than with gradients of climate and elevation. The differences in patterns for these three groups of indicators are explained by the degree of spatial and temporal integration represented by each sample type. The surface water data integrate more effectively over space than the foliar or soil data and therefore allow a more comprehensive view of N saturation. We conclude from these data that N deposition is altering N status in northeastern forests.",
    url = "https://doi.org/10.1641/0006-3568(2003)053[0375:indatn]2.0.co;2",
    doi = "10.1641/0006-3568(2003)053[0375:indatn]2.0.co;2",
    openalex = "W2135771209",
    references = "doi101126science2725259244"
}

@article{goss2003a,
    author = "Goss, Lisa M.",
    title = "A Demonstration of Acid Rain and Lake Acidification: Wet Deposition of Sulfur Dioxide",
    year = "2003",
    journal = "Journal of Chemical Education",
    url = "https://doi.org/10.1021/ed080p39",
    doi = "10.1021/ed080p39",
    number = "1",
    openalex = "W2092744150",
    pages = "39",
    volume = "80",
    references = "openalexw1599334980"
}

@article{doi101016jenvsci200405005,
    author = "Menz, Fredric C. and Seip, Hans M.",
    title = "Acid rain in Europe and the United States: an update",
    year = "2004",
    journal = "Environmental Science \& Policy",
    url = "https://doi.org/10.1016/j.envsci.2004.05.005",
    doi = "10.1016/j.envsci.2004.05.005",
    openalex = "W2149580636",
    references = "doi1010079781441985361, doi101016002216949090130p, doi101016s0301421503001563, doi101029wr021i001p00051, doi10103835000537, doi10103844114, doi1015790044744731264, doi1016410006356820010510180aditnu20co2, doi105194hess52832001, openalexw2112482114"
}

This is a manual for the Global Atmosphere Watch Precipitation Chemistry (GAW-PC) Programme. Where possible, it describes standard operating procedures and otherwise provides guidance on methods and procedures. The objectives of the GAW Precipitation Chemistry Programme are as follows: (1) to assure the harmonization of measurements conducted globally by various regional and national programmes; (2) to enable quantification of patterns and trends in the composition of atmospheric precipitation at global and regional scales; (3) to improve the understanding of biogeochemical cycles of major chemical species; (4) to facilitate global assessments of acid deposition and to investigate long-range transport from major source areas; and (5) to provide the data needed for evaluating the effects of acid deposition on major ecosystems, for example, coastal and sensitive areas, and for developing control measures. To address the first objective and to improve the quality of global data, the GAW-PC Programme has undertaken to revise its standard operating procedures, including all on-site, laboratory, data management and quality assurance aspects of the measurement system. The new procedures documented and presented in these chapters are for major ions in precipitation. The major ions and measurements covered in this manual are as follows: Sulfate, Chloride, Calcium, Conductivity, Nitrate, Sodium, Magnesium, Ammonium, Potassium, and pH. Other provisional measurements include Alkalinity and Organic Acids.

@article{openalexw1909762359,
    author = "Allan, Mary Ann",
    title = "Manual for the GAW Precipitation Chemistry Programme: Guidelines, Data Quality Objectives and Standard Operating Procedures",
    year = "2004",
    journal = "Defense Technical Information Center (DTIC)",
    abstract = "This is a manual for the Global Atmosphere Watch Precipitation Chemistry (GAW-PC) Programme. Where possible, it describes standard operating procedures and otherwise provides guidance on methods and procedures. The objectives of the GAW Precipitation Chemistry Programme are as follows: (1) to assure the harmonization of measurements conducted globally by various regional and national programmes; (2) to enable quantification of patterns and trends in the composition of atmospheric precipitation at global and regional scales; (3) to improve the understanding of biogeochemical cycles of major chemical species; (4) to facilitate global assessments of acid deposition and to investigate long-range transport from major source areas; and (5) to provide the data needed for evaluating the effects of acid deposition on major ecosystems, for example, coastal and sensitive areas, and for developing control measures. To address the first objective and to improve the quality of global data, the GAW-PC Programme has undertaken to revise its standard operating procedures, including all on-site, laboratory, data management and quality assurance aspects of the measurement system. The new procedures documented and presented in these chapters are for major ions in precipitation. The major ions and measurements covered in this manual are as follows: Sulfate, Chloride, Calcium, Conductivity, Nitrate, Sodium, Magnesium, Ammonium, Potassium, and pH. Other provisional measurements include Alkalinity and Organic Acids.",
    openalex = "W1909762359"
}

A demonstration showing acid rain formation is described. Oxides of sulfur and nitrogen that result from the burning of fossil fuels are the major pollutants of acid rain. In this demonstration, SO2 gas is produced by the burning of matches. An acid-base indicator will show that the dissolved gas turns an aqueous solution acidic. What acid rain is

@article{openalexw2184727780,
    author = "Fong, Man Wai",
    title = "A demonstration of acid rain",
    year = "2004",
    journal = "Asia-Pacific Forum on Science Learning and Teaching",
    abstract = "A demonstration showing acid rain formation is described. Oxides of sulfur and nitrogen that result from the burning of fossil fuels are the major pollutants of acid rain. In this demonstration, SO2 gas is produced by the burning of matches. An acid-base indicator will show that the dissolved gas turns an aqueous solution acidic. What acid rain is",
    openalex = "W2184727780",
    references = "goss2003a"
}

@incollection{blake2005acid,
    author = "Blake, L.",
    title = "ACID RAIN AND SOIL ACIDIFICATION",
    year = "2005",
    booktitle = "Encyclopedia of Soils in the Environment",
    url = "https://doi.org/10.1016/b0-12-348530-4/00083-7",
    doi = "10.1016/b0-12-348530-4/00083-7",
    openalex = "W2504157999",
    pages = "1-11",
    references = "doi10100797814612445611, doi101016b9780125906555x50014, doi101038307599a0, doi101046j13652389199900253x, doi10108002827588609382413, doi101111j136523891990tb00051x, doi1023072403462"
}

@article{doi101021es0626133,
    author = "Larssen, Thorjørn and Lydersen, Espen and Tang, Dagang and He, Yi and Gao, Jixi and Liu, Haiying and Duan, Lei and Seip, Hans M. and Vogt, Rolf D. and Mulder, Jan and Shao, Min and Wang, Yanhui and He, Shang and Zhang, Xiaoshan and Solberg, Svein and Aas, Wenche and Økland, Tonje and Eilertsen, Odd and Angell, Valter and Li, Q and Zhao, Dawei and Xiang, Renjun and Xiao, Jinshong and Luo, Jiahai",
    title = "Acid Rain in China",
    year = "2006",
    journal = "Environmental Science \& Technology",
    url = "https://doi.org/10.1021/es0626133",
    doi = "10.1021/es0626133",
    openalex = "W2093880921"
}

@article{doi101016jscitotenv200702028,
    author = "Chen, Xi and Mulder, Jan",
    title = "Atmospheric deposition of nitrogen at five subtropical forested sites in South China",
    year = "2007",
    journal = "The Science of The Total Environment",
    url = "https://doi.org/10.1016/j.scitotenv.2007.02.028",
    doi = "10.1016/j.scitotenv.2007.02.028",
    openalex = "W2046499893",
    references = "doi101007bf01186169"
}

Anthropogenic nitrous pollutant emissions in China significantly increased during the last decades, which contributed to the accelerated nitrogen (N) deposition. In order to characterize spatial pattern of nitrogen deposition, we employed the kriging technique to interpolate sampling data of precipitation chemistry and ambient air concentration from site‐network observations over China. The estimation of wet deposition in China was limited to aqueous NO 3 − and NH 4 +, while ambient NO 2 was the only species involved in the predicted dry deposition fluxes. To obtain wet deposition fluxes, precipitation concentration was multiplied by 20‐year mean precipitation amounts with a resolution of 10 × 10 km. Dry deposition fluxes were products of the interpolated ambient NO 2 concentration and deposition velocities modeled for the main vegetation types in China. The total deposition rates of wet and dry deposition peaked over the central south China, with maximum values of 63.53 kg N ha −1 yr −1, and an average value of 12.89 kg N ha −1 yr −1. With ambient NO 2 concentration data spanning from the year 1990 through 2003, we detected and evaluated trends in the time series of the annual values of atmospheric NO 2 concentration. Significant upward trends at 21 of 102 sites were exhibited, with median percent change of 61.45% over the period 1990–2003. In addition, spatially continuous patterns of dry deposition fluxes based on ambient NO 2 measurements in two 5‐year phases, 9 years apart, were carried out. On average, there was a rise of 7.66% in NO 2 dry deposition during 9 years throughout China.

@article{doi1010292006jd007990,
    author = "Lü, Chaoqun and Tian, Hanqin",
    title = "Spatial and temporal patterns of nitrogen deposition in China: Synthesis of observational data",
    year = "2007",
    journal = "Journal of Geophysical Research Atmospheres",
    abstract = "Anthropogenic nitrous pollutant emissions in China significantly increased during the last decades, which contributed to the accelerated nitrogen (N) deposition. In order to characterize spatial pattern of nitrogen deposition, we employed the kriging technique to interpolate sampling data of precipitation chemistry and ambient air concentration from site‐network observations over China. The estimation of wet deposition in China was limited to aqueous NO 3 − and NH 4 +, while ambient NO 2 was the only species involved in the predicted dry deposition fluxes. To obtain wet deposition fluxes, precipitation concentration was multiplied by 20‐year mean precipitation amounts with a resolution of 10 × 10 km. Dry deposition fluxes were products of the interpolated ambient NO 2 concentration and deposition velocities modeled for the main vegetation types in China. The total deposition rates of wet and dry deposition peaked over the central south China, with maximum values of 63.53 kg N ha −1 yr −1, and an average value of 12.89 kg N ha −1 yr −1. With ambient NO 2 concentration data spanning from the year 1990 through 2003, we detected and evaluated trends in the time series of the annual values of atmospheric NO 2 concentration. Significant upward trends at 21 of 102 sites were exhibited, with median percent change of 61.45\% over the period 1990–2003. In addition, spatially continuous patterns of dry deposition fluxes based on ambient NO 2 measurements in two 5‐year phases, 9 years apart, were carried out. On average, there was a rise of 7.66\% in NO 2 dry deposition during 9 years throughout China.",
    url = "https://doi.org/10.1029/2006jd007990",
    doi = "10.1029/2006jd007990",
    openalex = "W2098076869",
    references = "larssen2000acid"
}

@article{doi101016jepsl200802039,
    author = "Li, Si‐Liang and Calmels, Damien and Han, Guilin and Gaillardet, Jérôme and Liu, Cong‐Qiang",
    title = "Sulfuric acid as an agent of carbonate weathering constrained by δ13CDIC: Examples from Southwest China",
    year = "2008",
    journal = "Earth and Planetary Science Letters",
    url = "https://doi.org/10.1016/j.epsl.2008.02.039",
    doi = "10.1016/j.epsl.2008.02.039",
    openalex = "W2047695035",
    references = "doi101016jatmosenv200610030, doi101021es0626133"
}

Abstract. The nitrogen (N) emissions to the atmosphere and N deposition to forest ecosystems are increasing rapidly in Southeast Asia, but little is known about the fates and effects of elevated N deposition in forest ecosystems in this warm and humid region. Here we report the concentrations and fluxes of dissolved inorganic (DIN) and organic N (DON) in precipitation, throughfall, surface runoff and soil solution for three subtropical forests in a region of South China under high air pollution over two years (2004 and 2005), to investigate how deposited N is processed, and to examine the importance of DON in the N budget. The precipitation DIN input was 32–34 kg N ha−1 yr−1. An additional input of 18 kg N ha−1 yr−1 as DON was measured in 2005, which to our knowledge is the highest DON flux ever measured in precipitation. A canopy uptake of DIN was indicated in two young conifer dominated forests (72–85% of DIN input reached the floor in throughfall), whereas no uptake occurred in an old-growth broadleaf forest. The DON fluxes in throughfall were similar to that in precipitation in all forests. In the younger forests, DIN was further retained in the soil, with 41–63% of precipitation DIN leached below the 20-cm soil depth. Additionally, about half of the DON input was retained in these forests. The N retention in two young aggrading forests (21–28 kg N ha−1 yr−1) was in accordance with the estimates of N accumulation in biomass and litter accretion. In the old-growth forest, no N retention occurred, but rather a net loss of 8–16 kg N ha−1 yr−1 from the soil was estimated. In total up to 60 kg N ha−1 yr−1 was leached from the old-growth forest, indicating that this forest was completely N saturated and could not retain additional anthropogenic N inputs. We found that the majority of DIN deposition as well as of DIN leaching occurred in the rainy season (March to August) and that monthly DIN concentrations and fluxes in leaching were positively related to those in throughfall in all three forests, implying that part of the N leaching was hydrologically driven. Our results suggest that long-term high N deposition has caused elevated N leaching in all three forest types although most pronounced in the old-growth forest where wood increment was negligible or even negative. N availability even exceeded the biotic N demand in the young aggrading forests, with intensive rain in the growing season further enhancing N leaching in these forests.

@article{doi105194bg53392008,
    author = "Fang, Yunting and Gundersen, Per and Mo, Jiangming and Zhu, Weixing",
    title = "Input and output of dissolved organic and inorganic nitrogen in subtropical forests of South China under high air pollution",
    year = "2008",
    journal = "Biogeosciences",
    abstract = "Abstract. The nitrogen (N) emissions to the atmosphere and N deposition to forest ecosystems are increasing rapidly in Southeast Asia, but little is known about the fates and effects of elevated N deposition in forest ecosystems in this warm and humid region. Here we report the concentrations and fluxes of dissolved inorganic (DIN) and organic N (DON) in precipitation, throughfall, surface runoff and soil solution for three subtropical forests in a region of South China under high air pollution over two years (2004 and 2005), to investigate how deposited N is processed, and to examine the importance of DON in the N budget. The precipitation DIN input was 32–34 kg N ha−1 yr−1. An additional input of 18 kg N ha−1 yr−1 as DON was measured in 2005, which to our knowledge is the highest DON flux ever measured in precipitation. A canopy uptake of DIN was indicated in two young conifer dominated forests (72–85\% of DIN input reached the floor in throughfall), whereas no uptake occurred in an old-growth broadleaf forest. The DON fluxes in throughfall were similar to that in precipitation in all forests. In the younger forests, DIN was further retained in the soil, with 41–63\% of precipitation DIN leached below the 20-cm soil depth. Additionally, about half of the DON input was retained in these forests. The N retention in two young aggrading forests (21–28 kg N ha−1 yr−1) was in accordance with the estimates of N accumulation in biomass and litter accretion. In the old-growth forest, no N retention occurred, but rather a net loss of 8–16 kg N ha−1 yr−1 from the soil was estimated. In total up to 60 kg N ha−1 yr−1 was leached from the old-growth forest, indicating that this forest was completely N saturated and could not retain additional anthropogenic N inputs. We found that the majority of DIN deposition as well as of DIN leaching occurred in the rainy season (March to August) and that monthly DIN concentrations and fluxes in leaching were positively related to those in throughfall in all three forests, implying that part of the N leaching was hydrologically driven. Our results suggest that long-term high N deposition has caused elevated N leaching in all three forest types although most pronounced in the old-growth forest where wood increment was negligible or even negative. N availability even exceeded the biotic N demand in the young aggrading forests, with intensive rain in the growing season further enhancing N leaching in these forests.",
    url = "https://doi.org/10.5194/bg-5-339-2008",
    doi = "10.5194/bg-5-339-2008",
    openalex = "W2169342740",
    references = "doi101016jatmosenv200610030"
}

Acidification of rain-water is identified as one of the most serious environmental problems of transboundary nature. Acid rain is mainly a mixture of sulphuric and nitric acids depending upon the relative quantities of oxides of sulphur and nitrogen emissions. Due to the interaction of these acids with other constituents of the atmosphere, protons are released causing increase in the soil acidity Lowering of soil pH mobilizes and leaches away nutrient cations and increases availability of toxic heavy metals. Such changes in the soil chemical characteristics reduce the soil fertility which ultimately causes the negative impact on growth and productivity of forest trees and crop plants. Acidification of water bodies causes large scale negative impact on aquatic organisms including fishes. Acidification has some indirect effects on human health also. Acid rain affects each and every components of ecosystem. Acid rain also damages man-made materials and structures. By reducing the emission of the precursors of acid rain and to some extent by liming, the problem of acidification of terrestrial and aquatic ecosystem has been reduced during last two decades.

@article{openalexw2186096382,
    author = "Singh, Anita and Agrawal, Madhoolika",
    title = "Acid rain and its ecological consequences.",
    year = "2008",
    journal = "PubMed",
    abstract = "Acidification of rain-water is identified as one of the most serious environmental problems of transboundary nature. Acid rain is mainly a mixture of sulphuric and nitric acids depending upon the relative quantities of oxides of sulphur and nitrogen emissions. Due to the interaction of these acids with other constituents of the atmosphere, protons are released causing increase in the soil acidity Lowering of soil pH mobilizes and leaches away nutrient cations and increases availability of toxic heavy metals. Such changes in the soil chemical characteristics reduce the soil fertility which ultimately causes the negative impact on growth and productivity of forest trees and crop plants. Acidification of water bodies causes large scale negative impact on aquatic organisms including fishes. Acidification has some indirect effects on human health also. Acid rain affects each and every components of ecosystem. Acid rain also damages man-made materials and structures. By reducing the emission of the precursors of acid rain and to some extent by liming, the problem of acidification of terrestrial and aquatic ecosystem has been reduced during last two decades.",
    url = "https://openalex.org/W2186096382",
    openalex = "W2186096382",
    references = "doi1010160004698180902280, doi101023a1021398008726, doi101029jc087ic11p08771, doi10103844114, doi101126science2044390304, doi1015790044744730120, doi1015790044744731264, doi105194hess52832001, openalexw179400839, openalexw3133631291"
}

Facing challenges of increased energy consumption and related regional air pollution, China has been aggressively implementing flue gas desulfurization (FGD) and phasing out small inefficient units in the power sector in order to achieve the national goal of 10% reduction in sulfur dioxide (SO(2)) emissions from 2005 to 2010. In this paper, the effect of these measures on soil acidification is explored. An integrated methodology is used, combining emission inventory data, emission forecasts, air quality modeling, and ecological sensitivities indicated by critical load. National emissions of SO(2), oxides of nitrogen (NO(X)), particulate matter (PM), and ammonia (NH(3)) in 2005 were estimated to be 30.7, 19.6, 31.3, and 16.6 Mt, respectively. Implementation of existing policy will lead to reductions in SO(2) and PM emissions, while those of NO(X) and NH(3) will continue to rise, even under tentatively proposed control measures. In 2005, the critical load for soil acidification caused by sulfur (S) deposition was exceeded in 28% of the country's territory, mainly in eastern and south-central China. The area in exceedance will decrease to 26% and 20% in 2010 and 2020, respectively, given implementation of current plans for emission reductions. However, the exceedance of the critical load for nitrogen (N, combining effects of eutrophication and acidification) will double from 2005 to 2020 due to increased NO(X) and NH(3) emissions. Combining the acidification effects of S and N, the benefits of SO(2) reductions during 2005-2010 will almost be negated by increased N emissions. Therefore abatement of N emissions (NO(X) and NH(3)) and deposition will be a major challenge to China, requiring policy development and technology investments. To mitigate acidification in the future, China needs a multipollutant control strategy that integrates measures to reduce S, N, and PM.

@article{doi101021es901430n,
    author = "Zhao, Yu and Duan, Lei and Xing, Jia and Larssen, Thorjørn and Nielsen, Chris and Hao, Jiming",
    title = "Soil Acidification in China: Is Controlling SO 2 Emissions Enough?",
    year = "2009",
    journal = "Environmental Science \& Technology",
    abstract = "Facing challenges of increased energy consumption and related regional air pollution, China has been aggressively implementing flue gas desulfurization (FGD) and phasing out small inefficient units in the power sector in order to achieve the national goal of 10\% reduction in sulfur dioxide (SO(2)) emissions from 2005 to 2010. In this paper, the effect of these measures on soil acidification is explored. An integrated methodology is used, combining emission inventory data, emission forecasts, air quality modeling, and ecological sensitivities indicated by critical load. National emissions of SO(2), oxides of nitrogen (NO(X)), particulate matter (PM), and ammonia (NH(3)) in 2005 were estimated to be 30.7, 19.6, 31.3, and 16.6 Mt, respectively. Implementation of existing policy will lead to reductions in SO(2) and PM emissions, while those of NO(X) and NH(3) will continue to rise, even under tentatively proposed control measures. In 2005, the critical load for soil acidification caused by sulfur (S) deposition was exceeded in 28\% of the country's territory, mainly in eastern and south-central China. The area in exceedance will decrease to 26\% and 20\% in 2010 and 2020, respectively, given implementation of current plans for emission reductions. However, the exceedance of the critical load for nitrogen (N, combining effects of eutrophication and acidification) will double from 2005 to 2020 due to increased NO(X) and NH(3) emissions. Combining the acidification effects of S and N, the benefits of SO(2) reductions during 2005-2010 will almost be negated by increased N emissions. Therefore abatement of N emissions (NO(X) and NH(3)) and deposition will be a major challenge to China, requiring policy development and technology investments. To mitigate acidification in the future, China needs a multipollutant control strategy that integrates measures to reduce S, N, and PM.",
    url = "https://doi.org/10.1021/es901430n",
    doi = "10.1021/es901430n",
    openalex = "W2049293538",
    references = "doi101016jatmosenv200608046, doi101016jatmosenv200808021, doi101021es015601k, doi101021es0626133, doi1010292002jd003093, doi1010292007jd008684, doi10102997gb02266, doi10103844114, doi105194acp744192007, openalexw1585568164"
}

Abstract. As demonstrated in a number of investigations, gaseous sulfuric acid plays a central role in atmospheric aerosol formation. Using chemical ionization mass spectrometer the gas-phase sulfuric acid and OH concentration were measured in Hyytiälä, SMEAR II station, Southern Finland during 24 March to 28 June 2007. Clear diurnal cycles were observed as well as differences between new particle formation event days and non-event days. Typically, the daily maximum concentrations of gas phase sulfuric acid varied from 3×105 to 2×106 molec cm−3 between non-event and event days. Noon-time OH concentrations varied from 3-6×105 molec cm−3 and not a clear difference between event and non-events was detected. The measured time series were also used as a foundation to develop reasonable proxies for sulfuric acid concentration. The proxies utilized source and sink terms, and the simplest proxy is radiation times sulfur dioxide divided by condensation sink. Since it is still challenging to measure sulfuric acid in ambient concentrations, and due to its significant role in atmospheric particle formation, reasonable proxies are needed. We use all together three different proxies and one chemical box model and compared their results to the measured data. The proxies for the sulfuric acid concentration worked reasonably well, and will be used to describe sulfuric acid concentrations in SMEAR II station, when no measured sulfuric acid data is available. With caution the proxies could be applied to other environments as well.

@article{doi105194acp974352009,
    author = "Petäjä, Tuukka and Mauldin, Roy L. and Kosciuch, E. and McGrath, J. and Nieminen, Tuomo and Paasonen, Pauli and Boy, Michael and Adamov, Alexey and Kotiaho, Tapio and Kulmala, Markku",
    title = "Sulfuric acid and OH concentrations in a boreal forest site",
    year = "2009",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. As demonstrated in a number of investigations, gaseous sulfuric acid plays a central role in atmospheric aerosol formation. Using chemical ionization mass spectrometer the gas-phase sulfuric acid and OH concentration were measured in Hyytiälä, SMEAR II station, Southern Finland during 24 March to 28 June 2007. Clear diurnal cycles were observed as well as differences between new particle formation event days and non-event days. Typically, the daily maximum concentrations of gas phase sulfuric acid varied from 3×105 to 2×106 molec cm−3 between non-event and event days. Noon-time OH concentrations varied from 3-6×105 molec cm−3 and not a clear difference between event and non-events was detected. The measured time series were also used as a foundation to develop reasonable proxies for sulfuric acid concentration. The proxies utilized source and sink terms, and the simplest proxy is radiation times sulfur dioxide divided by condensation sink. Since it is still challenging to measure sulfuric acid in ambient concentrations, and due to its significant role in atmospheric particle formation, reasonable proxies are needed. We use all together three different proxies and one chemical box model and compared their results to the measured data. The proxies for the sulfuric acid concentration worked reasonably well, and will be used to describe sulfuric acid concentrations in SMEAR II station, when no measured sulfuric acid data is available. With caution the proxies could be applied to other environments as well.",
    url = "https://doi.org/10.5194/acp-9-7435-2009",
    doi = "10.5194/acp-9-7435-2009",
    openalex = "W2067917216",
    references = "doi10111911632486, doi105194acp736632007"
}

@book{doi1010079781402058851,
    author = "Brimblecombe, Peter and Hara, Hiroshi and Houle, Daniel and Novák, Martin",
    title = "Acid Rain - Deposition to Recovery",
    year = "2010",
    url = "https://doi.org/10.1007/978-1-4020-5885-1",
    doi = "10.1007/978-1-4020-5885-1",
    openalex = "W2105377300"
}

Vast quantities, on the order of megatons, of pollutants are emitted monthly to the atmosphere both by natural and anthropogenic sources. The evaluation of rainwater composition has great importance in understanding the atmospheric chemical composition, as water drops scavenge particles and soluble atmospheric pollutants. Most students are aware that SO2 is one of the pollutants related to the acidification of the atmosphere owing to its oxidation in the gas or liquid phase that produces sulfate and H+, but the situation is more complex in the presence of other common pollutants such as ammonia or formaldehyde. To give insight into the chemistry occurring in the gas and liquid phases, a demonstration is described where the pH of a “raindrop” is monitored during absorption of SO2 followed by exposure to H2O2, with or without previous contact with gaseous CH2O. The effect of the presence of alkalinizing substances such as NH3 in the atmosphere is evaluated as well. The raindrop is simulated by the wet bulb of a combination glass electrode exposed to the gas phase. Measurements can be made with any pH meter, although data acquisition with a computer is advantageous to illustrate the kinetics of the processes, as shown in the article.

@article{doi101021ed800046j,
    author = "Lopes, Fernando Silva and Coelho, Lúcia Helena Gomes and Gutz, Ivano Gebhardt Rolf",
    title = "Unraveling the Role of Sulfur Compounds in Acid Rain Formation: Experiments on a Wetted Glass pH Electrode",
    year = "2010",
    journal = "Journal of Chemical Education",
    abstract = "Vast quantities, on the order of megatons, of pollutants are emitted monthly to the atmosphere both by natural and anthropogenic sources. The evaluation of rainwater composition has great importance in understanding the atmospheric chemical composition, as water drops scavenge particles and soluble atmospheric pollutants. Most students are aware that SO2 is one of the pollutants related to the acidification of the atmosphere owing to its oxidation in the gas or liquid phase that produces sulfate and H+, but the situation is more complex in the presence of other common pollutants such as ammonia or formaldehyde. To give insight into the chemistry occurring in the gas and liquid phases, a demonstration is described where the pH of a “raindrop” is monitored during absorption of SO2 followed by exposure to H2O2, with or without previous contact with gaseous CH2O. The effect of the presence of alkalinizing substances such as NH3 in the atmosphere is evaluated as well. The raindrop is simulated by the wet bulb of a combination glass electrode exposed to the gas phase. Measurements can be made with any pH meter, although data acquisition with a computer is advantageous to illustrate the kinetics of the processes, as shown in the article.",
    url = "https://doi.org/10.1021/ed800046j",
    doi = "10.1021/ed800046j",
    openalex = "W2030958072",
    references = "goss2003a"
}

The elemental composition of rainwater, throughfall, and soil solutions of a forest ecosystem in the acid rain control region of southwest China was investigated during 2007-2008 to assess the acid buffering capacity of different forest covers. A possible seasonal distribution of wet deposition was identified. Sulfur was determined as the dominant acidification precursor in this region. The chemical composition of rainfall intercepted by the forest canopy was modified substantially; generally the ion concentrations were increased by dry deposition and foliar leaching. As an exception, the concentration of NH(4)(+) and NO(3)(-) decreased in throughfall, which was probably due to the absorption of nitrogen by the leaves. Elemental concentrations in soil solutions decreased with depth. The water conservation capacity of different forests was also evaluated. The most appropriate forest vegetation for water conservation and remediation of acid precipitation in this region was explored for the sake of ecosystem management, ecological restoration and economic development.

@article{doi101039c0em00116c,
    author = "Chen, Jing and Li, Wei and Gao, Fang",
    title = "Biogeochemical effects of forest vegetation on acid precipitation-related water chemistry: a case study in southwest China.",
    year = "2010",
    journal = "Journal of environmental monitoring: JEM",
    abstract = "The elemental composition of rainwater, throughfall, and soil solutions of a forest ecosystem in the acid rain control region of southwest China was investigated during 2007-2008 to assess the acid buffering capacity of different forest covers. A possible seasonal distribution of wet deposition was identified. Sulfur was determined as the dominant acidification precursor in this region. The chemical composition of rainfall intercepted by the forest canopy was modified substantially; generally the ion concentrations were increased by dry deposition and foliar leaching. As an exception, the concentration of NH(4)(+) and NO(3)(-) decreased in throughfall, which was probably due to the absorption of nitrogen by the leaves. Elemental concentrations in soil solutions decreased with depth. The water conservation capacity of different forests was also evaluated. The most appropriate forest vegetation for water conservation and remediation of acid precipitation in this region was explored for the sake of ecosystem management, ecological restoration and economic development.",
    url = "https://pubmed.ncbi.nlm.nih.gov/20859590/",
    doi = "10.1039/c0em00116c",
    openalex = "W2051052861",
    pmid = "20859590",
    references = "doi10100797894009092368, doi101007bf01186169, doi101016jatmosenv200610030, doi101016jatmosenv200907031, doi101016s0045653503000286, doi101016s0269749103000198, doi101021es0626133, doi102134jeq199500472425002400020002x, larssen2000acid"
}

Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.

@article{doi101126science1182570,
    author = "Guo, Jingheng and Liu, Xu and Zhang, Ying and Shen, Jianning and Han, Wenxuan and Zhang, Wei and Christie, Peter and Goulding, K. W. T. and Vitousek, Peter M. and Zhang, F.S.",
    title = "Significant Acidification in Major Chinese Croplands",
    year = "2010",
    journal = "Science",
    abstract = "Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.",
    url = "https://doi.org/10.1126/science.1182570",
    doi = "10.1126/science.1182570",
    openalex = "W2065762344",
    references = "doi101038nature04095, doi101126science1097329, doi101126science1152509, doi1018901051076119970070737haotgn20co2"
}

Abstract. With the rapid development of the economy, the sulfur dioxide (SO2) emission from China since 2000 is of increasing concern. In this study, we estimate the annual SO2 emission in China after 2000 using a technology-based methodology specifically for China. From 2000 to 2006, total SO2 emission in China increased by 53%, from 21.7 Tg to 33.2 Tg, at an annual growth rate of 7.3%. Emissions from power plants are the main sources of SO2 in China and they increased from 10.6 Tg to 18.6 Tg in the same period. Geographically, emission from north China increased by 85%, whereas that from the south increased by only 28%. The emission growth rate slowed around 2005, and emissions began to decrease after 2006 mainly due to the wide application of flue-gas desulfurization (FGD) devices in power plants in response to a new policy of China's government. This paper shows that the trend of estimated SO2 emission in China is consistent with the trends of SO2 concentration and acid rain pH and frequency in China, as well as with the increasing trends of background SO2 and sulfate concentration in East Asia. A longitudinal gradient in the percentage change of urban SO2 concentration in Japan is found during 2000–2007, indicating that the decrease of urban SO2 is lower in areas close to the Asian continent. This implies that the transport of increasing SO2 from the Asian continent partially counteracts the local reduction of SO2 emission downwind. The aerosol optical depth (AOD) products of Moderate Resolution Imaging Spectroradiometer (MODIS) are found to be highly correlated with the surface solar radiation (SSR) measurements in East Asia. Using MODIS AOD data as a surrogate of SSR, we found that China and East Asia excluding Japan underwent a continuous dimming after 2000, which is in line with the dramatic increase in SO2 emission in East Asia. The trends of AOD from both satellite retrievals and model over East Asia are also consistent with the trend of SO2 emission in China, especially during the second half of the year, when sulfur contributes the largest fraction of AOD. The arrested growth in SO2 emissions since 2006 is also reflected in the decreasing trends of SO2 and SO42− concentrations, acid rain pH values and frequencies, and AOD over East Asia.

@article{doi105194acp1063112010,
    author = "Lü, Zifeng and Streets, David G. and Zhang, Q. and Wang, Shuxiao and Carmichael, Gregory R. and Cheng, Yafang and Wei, Chao and Chin, Mian and Diehl, T. and Tan, Q.",
    title = "Sulfur dioxide emissions in China and sulfur trends in East Asia since 2000",
    year = "2010",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. With the rapid development of the economy, the sulfur dioxide (SO2) emission from China since 2000 is of increasing concern. In this study, we estimate the annual SO2 emission in China after 2000 using a technology-based methodology specifically for China. From 2000 to 2006, total SO2 emission in China increased by 53\%, from 21.7 Tg to 33.2 Tg, at an annual growth rate of 7.3\%. Emissions from power plants are the main sources of SO2 in China and they increased from 10.6 Tg to 18.6 Tg in the same period. Geographically, emission from north China increased by 85\%, whereas that from the south increased by only 28\%. The emission growth rate slowed around 2005, and emissions began to decrease after 2006 mainly due to the wide application of flue-gas desulfurization (FGD) devices in power plants in response to a new policy of China's government. This paper shows that the trend of estimated SO2 emission in China is consistent with the trends of SO2 concentration and acid rain pH and frequency in China, as well as with the increasing trends of background SO2 and sulfate concentration in East Asia. A longitudinal gradient in the percentage change of urban SO2 concentration in Japan is found during 2000–2007, indicating that the decrease of urban SO2 is lower in areas close to the Asian continent. This implies that the transport of increasing SO2 from the Asian continent partially counteracts the local reduction of SO2 emission downwind. The aerosol optical depth (AOD) products of Moderate Resolution Imaging Spectroradiometer (MODIS) are found to be highly correlated with the surface solar radiation (SSR) measurements in East Asia. Using MODIS AOD data as a surrogate of SSR, we found that China and East Asia excluding Japan underwent a continuous dimming after 2000, which is in line with the dramatic increase in SO2 emission in East Asia. The trends of AOD from both satellite retrievals and model over East Asia are also consistent with the trend of SO2 emission in China, especially during the second half of the year, when sulfur contributes the largest fraction of AOD. The arrested growth in SO2 emissions since 2006 is also reflected in the decreasing trends of SO2 and SO42− concentrations, acid rain pH values and frequencies, and AOD over East Asia.",
    url = "https://doi.org/10.5194/acp-10-6311-2010",
    doi = "10.5194/acp-10-6311-2010",
    openalex = "W2056537970",
    references = "doi101021es0626133, doi101021es901430n, doi1010292002jd003093, doi1010292003jd003697, doi1010292008jd011470, doi101029jc087ic02p01231, doi101109tgrs2006872333, doi101126science1103215, doi1011751520046919990560127smoamm20co2, doi101175jas33851, doi105194acp744192007, doi105194acp951312009"
}

Here we present the first detailed study on fluxes of sulfur (S), nitrogen (N), and major cations in Chinese subtropical forest catchments. Data are from four study sites, differing in inputs of atmospheric pollutants and sensitivity to acidification. Results show important differences from most sites in North America and Europe. Dry deposition of S, N, and calcium (Ca) is considerably larger than wet deposition in most cases causing deposition fluxes ranging from moderate to very high, both for acidifying compounds (S deposition 1.5-10.5 kiloequivalents per hectare and year (keq ha(-1) yr(-1)); N deposition 0.4 to 2.5 keq ha(-1) yr(-1)) and for alkaline compounds (Ca deposition 0.8 to 5.7 keq ha(-1) yr(-1)). More than half of the input of acidity is neutralized by alkalinity associated with Ca deposition. Furthermore, the retention of incoming S and N is small in the soil root zone, but considerable in the deeper soils or riparian zone. Drainage water from the root zone of the soils at the two sites with the highest deposition show pronounced acidification. For the two sites with moderate deposition inputs, the root zones are retaining some of the incoming S and buffer some of the incoming acidity. The subsoils and the riparian zonesare strong sinks for N, S, and Ca. This is associated with substantial acid neutralization at all sites. These features are of major importance for the understanding of the long-term effects of acidification in China.

@article{doi101021es103426p,
    author = "Larssen, Thorjørn and Duan, Lei and Mulder, Jan",
    title = "Deposition and Leaching of Sulfur, Nitrogen and Calcium in Four Forested Catchments in China: Implications for Acidification",
    year = "2011",
    journal = "Environmental Science \& Technology",
    abstract = "Here we present the first detailed study on fluxes of sulfur (S), nitrogen (N), and major cations in Chinese subtropical forest catchments. Data are from four study sites, differing in inputs of atmospheric pollutants and sensitivity to acidification. Results show important differences from most sites in North America and Europe. Dry deposition of S, N, and calcium (Ca) is considerably larger than wet deposition in most cases causing deposition fluxes ranging from moderate to very high, both for acidifying compounds (S deposition 1.5-10.5 kiloequivalents per hectare and year (keq ha(-1) yr(-1)); N deposition 0.4 to 2.5 keq ha(-1) yr(-1)) and for alkaline compounds (Ca deposition 0.8 to 5.7 keq ha(-1) yr(-1)). More than half of the input of acidity is neutralized by alkalinity associated with Ca deposition. Furthermore, the retention of incoming S and N is small in the soil root zone, but considerable in the deeper soils or riparian zone. Drainage water from the root zone of the soils at the two sites with the highest deposition show pronounced acidification. For the two sites with moderate deposition inputs, the root zones are retaining some of the incoming S and buffer some of the incoming acidity. The subsoils and the riparian zonesare strong sinks for N, S, and Ca. This is associated with substantial acid neutralization at all sites. These features are of major importance for the understanding of the long-term effects of acidification in China.",
    url = "https://doi.org/10.1021/es103426p",
    doi = "10.1021/es103426p",
    openalex = "W2329180246",
    references = "doi101007s106610054336z, doi101016jatmosenv200610030, doi101016jscitotenv200702028, doi101021es0626133, doi101023a1020972100496, doi1010292002jd003093, doi101126science1182570, doi102136sssaj198603615995005000030013x, larssen2000acid, openalexw654605314"
}

We studied the atmospheric deposition of phosphorus (P) forms along an elevation gradient, and its contribution to the total external P loading of lakes in the Tatra Mountains and the Bohemian Forest, from 1998 to 2009. The aim was to evaluate how topographical (soil and vegetation pools in the catchment) and morphological (catchment‐to‐lake area ratio) characteristics of catchment–lake systems affect in‐lake nutrient structures in remote mountain areas. Concentrations of dissolved organic carbon (DOC), total phosphorus (TP), and total organic nitrogen (TON) were closely related (p < 0.001) to each other in lakes and their inlets. Terrestrial TP export (57–1183 μmol m −2 yr −1 on a catchment area basis) and lake‐water TP concentrations (0.05–1.0 μmol L −1) were closely associated with DOC leaching, exhibiting significant (p < 0.001) exponential relationships with increasing soil cover in the catchments. Precipitation fluxes of TP (460–918 μmol m −2 yr −1, average 692 μmol m −2 yr −1, with 50% being soluble reactive P) increased with precipitation along the elevation gradient and were highest in windy mountain areas. The C: N and C: P ratios of external nutrient inputs to the lakes were higher for terrestrial than atmospheric sources by a factor of ∼ 4 and 32, respectively, and the relative atmospheric contribution to the total external P loading of lakes was inversely related to the soil cover of catchments and the ratio between catchment and lake areas. The different composition and proportion of terrestrial and atmospheric nutrient inputs to mountain lakes along the vegetation zones determine the stoichiometric balance between the DOC and P available as nutrients for the food webs of natural mountain lakes.

@article{doi104319lo20115641343,
    author = "Kopáček, Jiřı́ and Hejzlar, Josef and Vrba, Jaroslav and Stuchlı́k, Evžen",
    title = "Phosphorus loading of mountain lakes: Terrestrial export and atmospheric deposition",
    year = "2011",
    journal = "Limnology and Oceanography",
    abstract = "We studied the atmospheric deposition of phosphorus (P) forms along an elevation gradient, and its contribution to the total external P loading of lakes in the Tatra Mountains and the Bohemian Forest, from 1998 to 2009. The aim was to evaluate how topographical (soil and vegetation pools in the catchment) and morphological (catchment‐to‐lake area ratio) characteristics of catchment–lake systems affect in‐lake nutrient structures in remote mountain areas. Concentrations of dissolved organic carbon (DOC), total phosphorus (TP), and total organic nitrogen (TON) were closely related (p < 0.001) to each other in lakes and their inlets. Terrestrial TP export (57–1183 μmol m −2 yr −1 on a catchment area basis) and lake‐water TP concentrations (0.05–1.0 μmol L −1) were closely associated with DOC leaching, exhibiting significant (p < 0.001) exponential relationships with increasing soil cover in the catchments. Precipitation fluxes of TP (460–918 μmol m −2 yr −1, average 692 μmol m −2 yr −1, with 50\% being soluble reactive P) increased with precipitation along the elevation gradient and were highest in windy mountain areas. The C: N and C: P ratios of external nutrient inputs to the lakes were higher for terrestrial than atmospheric sources by a factor of ∼ 4 and 32, respectively, and the relative atmospheric contribution to the total external P loading of lakes was inversely related to the soil cover of catchments and the ratio between catchment and lake areas. The different composition and proportion of terrestrial and atmospheric nutrient inputs to mountain lakes along the vegetation zones determine the stoichiometric balance between the DOC and P available as nutrients for the food webs of natural mountain lakes.",
    url = "https://doi.org/10.4319/lo.2011.56.4.1343",
    doi = "10.4319/lo.2011.56.4.1343",
    openalex = "W2168590941",
    references = "doi101016jatmosenv200907031"
}

Abstract. Continuous measurements of atmospheric ammonia (NH3) were conducted using Ogawa passive samplers from February 2008 to July 2010 at an urban site and from January 2007 to July 2010 at a rural site in Beijing, China. NH4+ in fine particles was also collected at the rural site during 2008–2009. The field comparison between the Ogawa passive samplers and an active analyzer for NH3 conducted at the urban site assures the quality and accuracy of the measurements. The concentrations of NH3 at the urban site ranged from 0.7 to 85.1 ppb, with the annual average of 18.5 ± 13.8 and 23.5 ± 18.0 ppb in 2008 and 2009, respectively. The NH3 concentrations at the rural site were lower than those at urban site, and varied from 0.8 to 42.9 ppb, with the annual average of 4.5 ± 4.6, 6.6 ± 7.0 and 7.1 ± 3.5 ppb in 2007, 2008 and 2009, respectively. The data showed marked seasonal variations at both sites. The results emphasized traffic to be a significant source of NH3 concentrations in winter in urban areas of Beijing. This was illustrated by the strong correlations of NH3 with the traffic related pollutants (NOx and CO) and also by the bimodal diurnal cycle of NH3 concentrations that was synchronized with traffic. Similar patterns were not observed during the summer, suggesting other non-traffic sources became more important. At the rural site, the daily NH4+ concentrations ranged from 0.10 to 36.53 μg m−3, with an average of 7.03 μg m−3 from June 2008 to December 2009. Monthly NH3 were significantly correlated with NH4+ concentrations. Average monthly NH3/NH4+ ratios varied from 0.13 to 2.28, with an average of 0.73. NH4+ in PM2.5 was primarily associated with SO4−2 at the rural site.

@article{doi105194acp1161392011,
    author = "Meng, Zhaoyang and Lin, Weili and Jiang, Xiujie and Yan, Pengcheng and Wang, Yu and Zhang, Yuhong and Jia, Xiaofang and Yu, Xiaolan",
    title = "Characteristics of atmospheric ammonia over Beijing, China",
    year = "2011",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. Continuous measurements of atmospheric ammonia (NH3) were conducted using Ogawa passive samplers from February 2008 to July 2010 at an urban site and from January 2007 to July 2010 at a rural site in Beijing, China. NH4+ in fine particles was also collected at the rural site during 2008–2009. The field comparison between the Ogawa passive samplers and an active analyzer for NH3 conducted at the urban site assures the quality and accuracy of the measurements. The concentrations of NH3 at the urban site ranged from 0.7 to 85.1 ppb, with the annual average of 18.5 ± 13.8 and 23.5 ± 18.0 ppb in 2008 and 2009, respectively. The NH3 concentrations at the rural site were lower than those at urban site, and varied from 0.8 to 42.9 ppb, with the annual average of 4.5 ± 4.6, 6.6 ± 7.0 and 7.1 ± 3.5 ppb in 2007, 2008 and 2009, respectively. The data showed marked seasonal variations at both sites. The results emphasized traffic to be a significant source of NH3 concentrations in winter in urban areas of Beijing. This was illustrated by the strong correlations of NH3 with the traffic related pollutants (NOx and CO) and also by the bimodal diurnal cycle of NH3 concentrations that was synchronized with traffic. Similar patterns were not observed during the summer, suggesting other non-traffic sources became more important. At the rural site, the daily NH4+ concentrations ranged from 0.10 to 36.53 μg m−3, with an average of 7.03 μg m−3 from June 2008 to December 2009. Monthly NH3 were significantly correlated with NH4+ concentrations. Average monthly NH3/NH4+ ratios varied from 0.13 to 2.28, with an average of 0.73. NH4+ in PM2.5 was primarily associated with SO4−2 at the rural site.",
    url = "https://doi.org/10.5194/acp-11-6139-2011",
    doi = "10.5194/acp-11-6139-2011",
    openalex = "W2157788523",
    references = "doi101126science23648081559"
}

This study is an analysis of 344 days with rainfall recorded during five years in a remote regional background EMEP (Cooperative Programme for the Monitoring and Evaluation of the Long Range Transmission of Air Pollutants in Europe) station in Spain. The chemical composition of the rainwater associated with air masses (nine categories) and weather types (26 categories) was characterized. The chemical composition of rainwater was dominated by calcium (Ca2+) and sulphate (SO42−-S), with VWM (Volume Weighted Mean) during the period studied (2002–2006), with 55 μeq/L and 34 μeqS/L, respectively. Calcium, sodium (Na+), ammonium (NH4+-N) and magnesium (Mg2+) seem to be dominant components in the neutralization of the rainwater. By applying Pearson correlations, principal component analysis and enrichment factors, it is possible to identify source types for the precipitation constituents. Interannual and intra-annual variability was also been studied. High calcium levels are associated with the frequent intrusions of Saharan dust that occur during the summer, and the maximums of chlorine and sodium in the winter may be due to the greater amount of maritime air recorded during this season. Wet deposition was determined by focusing on nitrogen deposition, registering mean annual values of 155 mgN/m2/year (from the NO3−-N) and 165 mgN/m2/year (from the NH4+-N).

@article{doi104209aaqr2012030068,
    author = "Calvo, Ana and Pont, Véronique and Olmo, F.J. and Castro, Amaya and Alados‐Arboledas, Lucas and Vicente, Ana and Fernández‐Raga, María and Fraile, Roberto",
    title = "Air Masses and Weather Types: A Useful Tool for Characterizing Precipitation Chemistry and Wet Deposition",
    year = "2012",
    journal = "Aerosol and Air Quality Research",
    abstract = "This study is an analysis of 344 days with rainfall recorded during five years in a remote regional background EMEP (Cooperative Programme for the Monitoring and Evaluation of the Long Range Transmission of Air Pollutants in Europe) station in Spain. The chemical composition of the rainwater associated with air masses (nine categories) and weather types (26 categories) was characterized. The chemical composition of rainwater was dominated by calcium (Ca2+) and sulphate (SO42−-S), with VWM (Volume Weighted Mean) during the period studied (2002–2006), with 55 μeq/L and 34 μeqS/L, respectively. Calcium, sodium (Na+), ammonium (NH4+-N) and magnesium (Mg2+) seem to be dominant components in the neutralization of the rainwater. By applying Pearson correlations, principal component analysis and enrichment factors, it is possible to identify source types for the precipitation constituents. Interannual and intra-annual variability was also been studied. High calcium levels are associated with the frequent intrusions of Saharan dust that occur during the summer, and the maximums of chlorine and sodium in the winter may be due to the greater amount of maritime air recorded during this season. Wet deposition was determined by focusing on nitrogen deposition, registering mean annual values of 155 mgN/m2/year (from the NO3−-N) and 165 mgN/m2/year (from the NH4+-N).",
    url = "https://doi.org/10.4209/aaqr.2012.03.0068",
    doi = "10.4209/aaqr.2012.03.0068",
    openalex = "W2150625309",
    references = "doi1010079781402058851"
}

Abstract. Emissions of reactive nitrogen (N) species can affect surrounding ecosystems via atmospheric deposition. However, few long-term and multi-site measurements have focused on both the wet and the dry deposition of individual N species in large areas of Northern China. Thus, the magnitude of atmospheric deposition of various N species in Northern China remains uncertain. In this study, the wet and dry atmospheric deposition of different N species was investigated during a three-year observation campaign at ten selected sites in Northern China. The results indicate that N deposition levels in Northern China were high with a ten-site, three-year average of 60.6 kg N ha−1 yr−1. The deposition levels showed spatial and temporal variation in the range of 28.5–100.4 kg N ha−1 yr−1. Of the annual total deposition, 40% was deposited via precipitation, and the remaining 60% was comprised of dry-deposited forms. Compared with gaseous N species, particulate N species were not the major contributor of dry-deposited N; they contributed approximately 10% to the total flux. On an annual basis, oxidized species accounted for 21% of total N deposition, thereby implying that other forms of gaseous N, such as NH3, comprised a dominant portion of the total flux. The contribution of NO3− to N deposition was enhanced in certain urban and industrial areas, possibly due to the fossil fuse combustion. As expected, the total N deposition in Northern China was significantly larger than the values reported by national scale monitoring networks in Europe, North America and East Asia because of high rates of wet deposition and gaseous NH3 dry deposition. Taken together, these findings show that NH3 emissions should be abated to mitigate high N deposition and associated potential impacts on ecosystems in Northern China. The present results improve our understanding of spatio-temporal variations of magnitudes, pathways and species of deposited N in the target areas, and are important not only to inform conservation and regulatory bodies but also to initiate further detailed studies. Uncertainties among current observations underscore the need to quantify the impact of vegetation on dry deposition and to refine the simulation of dry deposition velocity.

@article{doi105194acp1265152012,
    author = "Pan, Yuepeng and Wang, Yonghong and Tang, Guiqian and Wu, Dan",
    title = "Wet and dry deposition of atmospheric nitrogen at ten sites in Northern China",
    year = "2012",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. Emissions of reactive nitrogen (N) species can affect surrounding ecosystems via atmospheric deposition. However, few long-term and multi-site measurements have focused on both the wet and the dry deposition of individual N species in large areas of Northern China. Thus, the magnitude of atmospheric deposition of various N species in Northern China remains uncertain. In this study, the wet and dry atmospheric deposition of different N species was investigated during a three-year observation campaign at ten selected sites in Northern China. The results indicate that N deposition levels in Northern China were high with a ten-site, three-year average of 60.6 kg N ha−1 yr−1. The deposition levels showed spatial and temporal variation in the range of 28.5–100.4 kg N ha−1 yr−1. Of the annual total deposition, 40\% was deposited via precipitation, and the remaining 60\% was comprised of dry-deposited forms. Compared with gaseous N species, particulate N species were not the major contributor of dry-deposited N; they contributed approximately 10\% to the total flux. On an annual basis, oxidized species accounted for 21\% of total N deposition, thereby implying that other forms of gaseous N, such as NH3, comprised a dominant portion of the total flux. The contribution of NO3− to N deposition was enhanced in certain urban and industrial areas, possibly due to the fossil fuse combustion. As expected, the total N deposition in Northern China was significantly larger than the values reported by national scale monitoring networks in Europe, North America and East Asia because of high rates of wet deposition and gaseous NH3 dry deposition. Taken together, these findings show that NH3 emissions should be abated to mitigate high N deposition and associated potential impacts on ecosystems in Northern China. The present results improve our understanding of spatio-temporal variations of magnitudes, pathways and species of deposited N in the target areas, and are important not only to inform conservation and regulatory bodies but also to initiate further detailed studies. Uncertainties among current observations underscore the need to quantify the impact of vegetation on dry deposition and to refine the simulation of dry deposition velocity.",
    url = "https://doi.org/10.5194/acp-12-6515-2012",
    doi = "10.5194/acp-12-6515-2012",
    openalex = "W2169794216",
    references = "doi101021es0626133"
}

Abstract. From 2006 to 2007, the daily concentrations of major inorganic water-soluble constituents, mineral aerosol, organic carbon (OC) and elemental carbon (EC) in ambient PM10 samples were investigated from 16 urban, rural and remote sites in various regions of China, and were compared with global aerosol measurements. A large difference between urban and rural chemical species was found, normally with 1.5 to 2.5 factors higher in urban than in rural sites. Optically-scattering aerosols, such as sulfate (~16%), OC (~15%), nitrate (~7%), ammonium (~5%) and mineral aerosol (~35%) in most circumstance, are majorities of the total aerosols, indicating a dominant scattering feature of aerosols in China. Of the total OC, ~55%–60% can be attributed to the formation of the secondary organic carbon (SOC). The absorbing aerosol EC only accounts for ~3.5% of the total PM10. Seasonally, maximum concentrations of most aerosol species were found in winter while mineral aerosol peaks in spring. In addition to the regular seasonal maximum, secondary peaks were found for sulfate and ammonium in summer and for OC and EC in May and June. This can be considered as a typical seasonal pattern in various aerosol components in China. Aerosol acidity was normally neutral in most of urban areas, but becomes some acidic in rural areas. Based on the surface visibility observations from 681 meteorological stations in China between 1957 and 2005, four major haze areas are identified with similar visibility changes, namely, (1) Hua Bei Plain in N. China, and the Guanzhong Plain; (2) E. China with the main body in the Yangtze River Delta area; (3) S. China with most areas of Guangdong and the Pearl River Delta area; (4) The Si Chuan Basin in S.W. China. The degradation of visibility in these areas is linked with the emission changes and high PM concentrations. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and weather-climate effects, and in validating atmospheric models.

@article{doi105194acp127792012,
    author = "Zhang, X. Y. and Wang, Y. Q. and Niu, Tao and Zhang, X. C. and Gong, Sunling and Zhang, Yuhong and Sun, Junying",
    title = "Atmospheric aerosol compositions in China: spatial/temporal variability, chemical signature, regional haze distribution and comparisons with global aerosols",
    year = "2012",
    journal = "Atmospheric chemistry and physics",
    abstract = "Abstract. From 2006 to 2007, the daily concentrations of major inorganic water-soluble constituents, mineral aerosol, organic carbon (OC) and elemental carbon (EC) in ambient PM10 samples were investigated from 16 urban, rural and remote sites in various regions of China, and were compared with global aerosol measurements. A large difference between urban and rural chemical species was found, normally with 1.5 to 2.5 factors higher in urban than in rural sites. Optically-scattering aerosols, such as sulfate (\textasciitilde 16\%), OC (\textasciitilde 15\%), nitrate (\textasciitilde 7\%), ammonium (\textasciitilde 5\%) and mineral aerosol (\textasciitilde 35\%) in most circumstance, are majorities of the total aerosols, indicating a dominant scattering feature of aerosols in China. Of the total OC, \textasciitilde 55\%–60\% can be attributed to the formation of the secondary organic carbon (SOC). The absorbing aerosol EC only accounts for \textasciitilde 3.5\% of the total PM10. Seasonally, maximum concentrations of most aerosol species were found in winter while mineral aerosol peaks in spring. In addition to the regular seasonal maximum, secondary peaks were found for sulfate and ammonium in summer and for OC and EC in May and June. This can be considered as a typical seasonal pattern in various aerosol components in China. Aerosol acidity was normally neutral in most of urban areas, but becomes some acidic in rural areas. Based on the surface visibility observations from 681 meteorological stations in China between 1957 and 2005, four major haze areas are identified with similar visibility changes, namely, (1) Hua Bei Plain in N. China, and the Guanzhong Plain; (2) E. China with the main body in the Yangtze River Delta area; (3) S. China with most areas of Guangdong and the Pearl River Delta area; (4) The Si Chuan Basin in S.W. China. The degradation of visibility in these areas is linked with the emission changes and high PM concentrations. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and weather-climate effects, and in validating atmospheric models.",
    url = "https://doi.org/10.5194/acp-12-779-2012",
    doi = "10.5194/acp-12-779-2012",
    openalex = "W2163882954",
    references = "doi105194acp1063112010"
}

A global assessment of precipitation chemistry and deposition has been carried out under the direction of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Scientific Advisory Group for Precipitation Chemistry (SAG-PC). The assessment addressed three questions: (1) what do measurements and model estimates of precipitation chemistry and wet, dry and total deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity, and phosphorus show globally and regionally? (2) has the wet deposition of major ions changed since 2000 (and, where information and data are available, since 1990) and (3) what are the major gaps and uncertainties in our knowledge? To that end, regionally-representative measurements for two 3-year-averaging periods, 2000–2002 and 2005–2007, were compiled worldwide. Data from the 2000–2002 averaging period were combined with 2001 ensemble-mean modeling results from 21 global chemical transport models produced in Phase 1 of the Coordinated Model Studies Activities of the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). The measurement data and modeling results were used to generate global and regional maps of major ion concentrations in precipitation and deposition. A major product of the assessment is a database of quality assured ion concentration and wet deposition data gathered from regional and national monitoring networks. The database is available for download from the World Data Centre for Precipitation Chemistry (http://wdcpc.org/). The assessment concludes that global concentrations and deposition of sulfur and nitrogen are reasonably well characterized with levels generally highest near emission sources and more than an order of magnitude lower in areas largely free of anthropogenic influences. In many parts of the world, wet deposition of reduced nitrogen exceeds that of oxidized nitrogen and is increasing. Sulfur and nitrogen concentrations and deposition in North America and Europe have declined significantly in line with emission reduction policies. Major regions of the world, including South America, the more remote areas of North America, much of Asia, Africa, Oceania, polar regions, and all of the oceans, are inadequately sampled for all of the major ions in wet and dry deposition, and particularly so for phosphorus, organic forms of nitrogen, and weak acids including carbonates and organic acids. Measurement-based inferential estimates of dry deposition are limited to sulfur and some nitrogen in only a few regions of the world and methods are highly uncertain. The assessment concludes with recommendations to address major gaps and uncertainties in global ion concentration and deposition measurements.

@article{doi101016jatmosenv201310060,
    author = "Vet, Robert and Artz, Richard S. and Carou, Silvina and Shaw, Mike and Ro, Chul‐Un and Aas, Wenche and Baker, Alex R. and Bowersox, Van C. and Dentener, Frank and Galy‐Lacaux, Corinne and Hou, Amy and Pienaar, Jacobus J. and Gillett, Robert and Forti, M. C. and Gromov, Sergey and Hara, Hiroshi and Ходжер, Т. В. and Mahowald, N. M. and Ničković, Slobodan and Rao, P.S.P. and Reid, Neville W.",
    title = "A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus",
    year = "2013",
    journal = "Atmospheric Environment",
    abstract = "A global assessment of precipitation chemistry and deposition has been carried out under the direction of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Scientific Advisory Group for Precipitation Chemistry (SAG-PC). The assessment addressed three questions: (1) what do measurements and model estimates of precipitation chemistry and wet, dry and total deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity, and phosphorus show globally and regionally? (2) has the wet deposition of major ions changed since 2000 (and, where information and data are available, since 1990) and (3) what are the major gaps and uncertainties in our knowledge? To that end, regionally-representative measurements for two 3-year-averaging periods, 2000–2002 and 2005–2007, were compiled worldwide. Data from the 2000–2002 averaging period were combined with 2001 ensemble-mean modeling results from 21 global chemical transport models produced in Phase 1 of the Coordinated Model Studies Activities of the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). The measurement data and modeling results were used to generate global and regional maps of major ion concentrations in precipitation and deposition. A major product of the assessment is a database of quality assured ion concentration and wet deposition data gathered from regional and national monitoring networks. The database is available for download from the World Data Centre for Precipitation Chemistry (http://wdcpc.org/). The assessment concludes that global concentrations and deposition of sulfur and nitrogen are reasonably well characterized with levels generally highest near emission sources and more than an order of magnitude lower in areas largely free of anthropogenic influences. In many parts of the world, wet deposition of reduced nitrogen exceeds that of oxidized nitrogen and is increasing. Sulfur and nitrogen concentrations and deposition in North America and Europe have declined significantly in line with emission reduction policies. Major regions of the world, including South America, the more remote areas of North America, much of Asia, Africa, Oceania, polar regions, and all of the oceans, are inadequately sampled for all of the major ions in wet and dry deposition, and particularly so for phosphorus, organic forms of nitrogen, and weak acids including carbonates and organic acids. Measurement-based inferential estimates of dry deposition are limited to sulfur and some nitrogen in only a few regions of the world and methods are highly uncertain. The assessment concludes with recommendations to address major gaps and uncertainties in global ion concentration and deposition measurements.",
    url = "https://doi.org/10.1016/j.atmosenv.2013.10.060",
    doi = "10.1016/j.atmosenv.2013.10.060",
    openalex = "W2012375906",
    references = "doi101016jatmosenv200610030, doi101021es0626133, doi101021es901430n, doi105194acp1063112010, doi105194acp736632007"
}

The Chinese government has established compulsory targets to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions by 8% and 10%, respectively, during 2010-2015. In this study, the effect of the policy was evaluated by predicting the recovery of acidified forest soil in Chongqing, an area severely impacted by acid rain in southwest China. Since precipitation has decreased significantly in this area in recent years, the impact of drought on soil acidification was also considered. A dynamic acidification model, MAGIC, was used to predict future trends in soil chemistry under different scenarios for deposition reduction as well as drought. We found that the current regulation of SO2 emission abatement did not significantly increase soil water pH values, the Ca2+ to Al3+ molar ratio (Ca/Al), or soil base saturation to the level of 2000 before 2050. NOx emission control would have less of an effect on acidification recovery, while emission reduction of particulate matter could offset the benefits of SO2 reduction by greatly decreasing the deposition of base cations, particularly Ca(2+). Continuous droughts in the future might also delay acidification recovery. Therefore, more stringent SO2 emission control should be implemented to facilitate the recovery of seriously acidified areas in China.

@article{doi101016jscitotenv201306108,
    author = "Duan, Lei and Liu, Jing and Xin, Yan and Larssen, Thorjørn",
    title = "Air-pollution emission control in China: impacts on soil acidification recovery and constraints due to drought.",
    year = "2013",
    journal = "The Science of the total environment",
    abstract = "The Chinese government has established compulsory targets to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions by 8\% and 10\%, respectively, during 2010-2015. In this study, the effect of the policy was evaluated by predicting the recovery of acidified forest soil in Chongqing, an area severely impacted by acid rain in southwest China. Since precipitation has decreased significantly in this area in recent years, the impact of drought on soil acidification was also considered. A dynamic acidification model, MAGIC, was used to predict future trends in soil chemistry under different scenarios for deposition reduction as well as drought. We found that the current regulation of SO2 emission abatement did not significantly increase soil water pH values, the Ca2+ to Al3+ molar ratio (Ca/Al), or soil base saturation to the level of 2000 before 2050. NOx emission control would have less of an effect on acidification recovery, while emission reduction of particulate matter could offset the benefits of SO2 reduction by greatly decreasing the deposition of base cations, particularly Ca(2+). Continuous droughts in the future might also delay acidification recovery. Therefore, more stringent SO2 emission control should be implemented to facilitate the recovery of seriously acidified areas in China.",
    url = "https://pubmed.ncbi.nlm.nih.gov/23891996/",
    doi = "10.1016/j.scitotenv.2013.06.108",
    openalex = "W2049871486",
    pmid = "23891996",
    references = "doi101021es0626133, doi101021es103426p, doi101021es901430n, doi101029wr021i001p00051, doi101038484161a, doi101126science23648081559, doi105194acp119312011, doi105194hess54992001, larssen2000acid, openalexw168580091"
}

We documented the effects of acidic atmospheric deposition and soil acidification on the canopy health, basal area increment, and regeneration of sugar maple (SM) trees across the Adirondack region of New York State, in the northeastern United States, where SM are plentiful but not well studied and where widespread depletion of soil calcium (Ca) has been documented. Sugar maple is a dominant canopy species in the Adirondack Mountain ecoregion, and it has a high demand for Ca. Trees in this region growing on soils with poor acid-base chemistry (low exchangeable Ca and % base saturation [BS]) that receive relatively high levels of atmospheric sulfur and nitrogen deposition exhibited a near absence of SM seedling regeneration and lower crown vigor compared with study plots with relatively high exchangeable Ca and BS and lower levels of acidic deposition. Basal area increment averaged over the 20th century was correlated (p < 0.1) with acid-base chemistry of the Oa, A, and upper B soil horizons. A lack of Adirondack SM regeneration, reduced canopy condition, and possibly decreased basal area growth over recent decades are associated with low concentrations of nutrient base cations in this region that has undergone soil Ca depletion from acidic deposition.

@article{doi101021es401864w,
    author = "Sullivan, Timothy J. and Lawrence, Gregory B. and Bailey, Scott W. and McDonnell, Todd C. and Beier, Colin M. and Weathers, Kathleen C. and McPherson, Greggory and Bishop, Daniel A.",
    title = "Effects of Acidic Deposition and Soil Acidification on Sugar Maple Trees in the Adirondack Mountains, New York",
    year = "2013",
    journal = "Environmental Science \& Technology",
    abstract = "We documented the effects of acidic atmospheric deposition and soil acidification on the canopy health, basal area increment, and regeneration of sugar maple (SM) trees across the Adirondack region of New York State, in the northeastern United States, where SM are plentiful but not well studied and where widespread depletion of soil calcium (Ca) has been documented. Sugar maple is a dominant canopy species in the Adirondack Mountain ecoregion, and it has a high demand for Ca. Trees in this region growing on soils with poor acid-base chemistry (low exchangeable Ca and \% base saturation [BS]) that receive relatively high levels of atmospheric sulfur and nitrogen deposition exhibited a near absence of SM seedling regeneration and lower crown vigor compared with study plots with relatively high exchangeable Ca and BS and lower levels of acidic deposition. Basal area increment averaged over the 20th century was correlated (p < 0.1) with acid-base chemistry of the Oa, A, and upper B soil horizons. A lack of Adirondack SM regeneration, reduced canopy condition, and possibly decreased basal area growth over recent decades are associated with low concentrations of nutrient base cations in this region that has undergone soil Ca depletion from acidic deposition.",
    url = "https://doi.org/10.1021/es401864w",
    doi = "10.1021/es401864w",
    openalex = "W1996007188",
    references = "doi101016s0269749103000198"
}

To protect important resources under their bureau’s purview, the United States National Park Service’s (NPS) Arctic Network (ARCN) has developed a series of “vital signs” that are to be periodically monitored. One of these vital signs focuses on wet and dry deposition of atmospheric chemicals and further, the establishment of critical load (CL) values (thresholds for ecological effects based on cumulative depositional loadings) for nitrogen (N), sulfur, and metals. As part of the ARCN terrestrial monitoring programs, samples of the feather moss Hylocomium splendens are being collected and analyzed as a cost-effective means to monitor atmospheric pollutant deposition in this region. Ultimately, moss data combined with refined CL values might be used to help guide future regulation of atmospheric contaminant sources potentially impacting Arctic Alaska. But first, additional long-term studies are needed to determine patterns of contaminant deposition as measured by moss biomonitors and to quantify ecosystem responses at particular loadings/ ranges of contaminants within Arctic Alaska. Herein we briefly summarize 1) current regulatory guidance related to CL values 2) derivation of CL models for N and metals, 3) use of mosses as biomonitors of atmospheric deposition and loadings, 4) preliminary analysis of vulnerabilities and risks associated with CL estimates for N, 5) preliminary analysis of existing data for characterization of CL values for N for interior Alaska and 6) implications for managers and future research needs.

@article{doi104236ojap201324010,
    author = "Linder, Greg and Brumbaugh, William G. and Neitlich, Peter and Little, Edward E.",
    title = "Atmospheric Deposition and Critical Loads for Nitrogen and Metals in Arctic Alaska: Review and Current Status",
    year = "2013",
    journal = "Open Journal of Air Pollution",
    abstract = "To protect important resources under their bureau’s purview, the United States National Park Service’s (NPS) Arctic Network (ARCN) has developed a series of “vital signs” that are to be periodically monitored. One of these vital signs focuses on wet and dry deposition of atmospheric chemicals and further, the establishment of critical load (CL) values (thresholds for ecological effects based on cumulative depositional loadings) for nitrogen (N), sulfur, and metals. As part of the ARCN terrestrial monitoring programs, samples of the feather moss Hylocomium splendens are being collected and analyzed as a cost-effective means to monitor atmospheric pollutant deposition in this region. Ultimately, moss data combined with refined CL values might be used to help guide future regulation of atmospheric contaminant sources potentially impacting Arctic Alaska. But first, additional long-term studies are needed to determine patterns of contaminant deposition as measured by moss biomonitors and to quantify ecosystem responses at particular loadings/ ranges of contaminants within Arctic Alaska. Herein we briefly summarize 1) current regulatory guidance related to CL values 2) derivation of CL models for N and metals, 3) use of mosses as biomonitors of atmospheric deposition and loadings, 4) preliminary analysis of vulnerabilities and risks associated with CL estimates for N, 5) preliminary analysis of existing data for characterization of CL values for N for interior Alaska and 6) implications for managers and future research needs.",
    url = "https://doi.org/10.4236/ojap.2013.24010",
    doi = "10.4236/ojap.2013.24010",
    openalex = "W2004420869",
    references = "doi1010079781402058851"
}

Southern Nigeria is a major cassava producing area that has been subjected to air pollution from increasing industrial activities and population explosion in the coastal towns and cities. The level of pollution is not expected to change drastically in the immediate future. Investigations were carried out to study the changes in the morphology, survival, growth and yield of TMS 96/1672 cultivar of cassava Manihot esculenta (Crantz) to simulated acid rain. The plants were exposed to simulated acid rain of pH 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0 (control) respectively. Simulated acid rain induced morphological changes including chlorosis, early leaf senescence, necrosis, leaf abscission, leaf folding and death. Plant height, leaf area, fresh weight, dry weight, relative growth rate, chlorophyll content and the harvest index was the highest at pH 7.0 (control) and significantly (p<0.05) decreased with increasing acidity. The results indicates that TMS 96/1672 cultivar of Manihot esculenta exhibited growth stimulation at low acidity of pH 2.0 and it is likely to be retarded in future due to rapid and uncontrolled industrialization.

@article{doi105539jasv6n1p96,
    author = "Odiyi, Bridget O. and Bamidele, J. J. F.",
    title = "Effects of Simulated Acid Rain on Growth and Yield of Cassava Manihot esculenta (Crantz)",
    year = "2013",
    journal = "Journal of Agricultural Science",
    abstract = "Southern Nigeria is a major cassava producing area that has been subjected to air pollution from increasing industrial activities and population explosion in the coastal towns and cities. The level of pollution is not expected to change drastically in the immediate future. Investigations were carried out to study the changes in the morphology, survival, growth and yield of TMS 96/1672 cultivar of cassava Manihot esculenta (Crantz) to simulated acid rain. The plants were exposed to simulated acid rain of pH 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0 (control) respectively. Simulated acid rain induced morphological changes including chlorosis, early leaf senescence, necrosis, leaf abscission, leaf folding and death. Plant height, leaf area, fresh weight, dry weight, relative growth rate, chlorophyll content and the harvest index was the highest at pH 7.0 (control) and significantly (p<0.05) decreased with increasing acidity. The results indicates that TMS 96/1672 cultivar of Manihot esculenta exhibited growth stimulation at low acidity of pH 2.0 and it is likely to be retarded in future due to rapid and uncontrolled industrialization.",
    url = "https://doi.org/10.5539/jas.v6n1p96",
    doi = "10.5539/jas.v6n1p96",
    openalex = "W2164110591",
    references = "doi1010079781402058851"
}

Atmospheric deposition to forests has been monitored within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with sampling and analyses of bulk precipitation and throughfall at several hundred forested plots for more than 15 years. The current deposition of inorganic nitrogen (nitrate and ammonium) and sulphate is highest in central Europe as well as in some southern regions. We compared linear regression and Mann–Kendall trend analysis techniques often used to detect temporal trends in atmospheric deposition. The choice of method influenced the number of significant trends. Detection of trends was more powerful using monthly data compared to annual data. The slope of a trend needed to exceed a certain minimum in order to be detected despite the short-term variability of deposition. This variability could to a large extent be explained by meteorological processes, and the minimum slope of detectable trends was thus similar across sites and many ions. The overall decreasing trends for inorganic nitrogen and sulphate in the decade to 2010 were about 2% and 6%, respectively. Time series of about 10 and 6 years were required to detect significant trends in inorganic nitrogen and sulphate on a single plot. The strongest decreasing trends were observed in western central Europe in regions with relatively high deposition fluxes, whereas stable or slightly increasing deposition during the last 5 years was found east of the Alpine region as well as in northern Europe. Past reductions in anthropogenic emissions of both acidifying and eutrophying compounds can be confirmed due to the availability of long-term data series but further reductions are required to reduce deposition to European forests to levels below which significant harmful effects do not occur according to present knowledge.

@article{doi101016jatmosenv201406054,
    author = "Waldner, Peter and Marchetto, Aldo and Thimonier, Anne and Schmitt, Maria and Rogora, Michela and Granke, Oliver and Mues, Volker and Hansen, Karin and Karlsson, Gunilla Pihl and Žlindra, Daniel and Clarke, Nicholas and Verstraeten, Arne and Lazdiņš, Andis and Schimming, Claus and Iacoban, Carmen and Lindroos, Antti‐Jussi and Vanguelova, Elena and Benham, Sue and Meesenburg, Henning and Nicolas, Manuel and Kowalska, Anna and Apuhtin, Vladislav and Napa, Ülle and Lachmanová, Zora and Kristoefel, Ferdinand and Bleeker, Albert and Ingerslev, Morten and Vesterdal, Lars and Molina, Juan and Fischer, Uwe and Seidling, Walter and Jonard, Mathieu and O’Dea, Philip and Johnson, James and Fischer, Richard and Lorenz, Martin",
    title = "Detection of temporal trends in atmospheric deposition of inorganic nitrogen and sulphate to forests in Europe",
    year = "2014",
    journal = "Atmospheric Environment",
    abstract = "Atmospheric deposition to forests has been monitored within the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with sampling and analyses of bulk precipitation and throughfall at several hundred forested plots for more than 15 years. The current deposition of inorganic nitrogen (nitrate and ammonium) and sulphate is highest in central Europe as well as in some southern regions. We compared linear regression and Mann–Kendall trend analysis techniques often used to detect temporal trends in atmospheric deposition. The choice of method influenced the number of significant trends. Detection of trends was more powerful using monthly data compared to annual data. The slope of a trend needed to exceed a certain minimum in order to be detected despite the short-term variability of deposition. This variability could to a large extent be explained by meteorological processes, and the minimum slope of detectable trends was thus similar across sites and many ions. The overall decreasing trends for inorganic nitrogen and sulphate in the decade to 2010 were about 2\% and 6\%, respectively. Time series of about 10 and 6 years were required to detect significant trends in inorganic nitrogen and sulphate on a single plot. The strongest decreasing trends were observed in western central Europe in regions with relatively high deposition fluxes, whereas stable or slightly increasing deposition during the last 5 years was found east of the Alpine region as well as in northern Europe. Past reductions in anthropogenic emissions of both acidifying and eutrophying compounds can be confirmed due to the availability of long-term data series but further reductions are required to reduce deposition to European forests to levels below which significant harmful effects do not occur according to present knowledge.",
    url = "https://doi.org/10.1016/j.atmosenv.2014.06.054",
    doi = "10.1016/j.atmosenv.2014.06.054",
    openalex = "W2153338597",
    references = "doi101007bf01186169"
}

@article{doi101016jatmosenv201409005,
    author = "Du, Enzai and Jiang, Yuan and Fang, Jingyun and de Vries, W.",
    title = "Inorganic nitrogen deposition in China's forests: Status and characteristics",
    year = "2014",
    journal = "Atmospheric Environment",
    url = "https://doi.org/10.1016/j.atmosenv.2014.09.005",
    doi = "10.1016/j.atmosenv.2014.09.005",
    openalex = "W2060122352",
    references = "doi10100797894009092368, doi101007bf01186169"
}

Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long-term N deposition on soil acidification processes in tropical forests. We have established a long-term N-deposition experiment in an N-rich lowland tropical forest of Southern China since 2002 with N addition as NH4 NO3 of 0, 50, 100 and 150 kg N ha(-1) yr(-1). We measured soil acidification status and element leaching in soil drainage solution after 6-year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid-sensitive showing high acidification (pH(H2O) <4.0), negative water-extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8%) throughout soil profiles. Long-term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable Al(3+), but increased cation exchange capacity (CEC). Nitrogen addition-induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20 cm depth, but not at 40 cm. Furthermore, there was no evidence that Al(3+) was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H(+) dominating changes of soil cation pool, an exhausted base cation pool, N-addition stimulating SOC production, and N saturation. Our results suggest that long-term N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future.

@article{doi101111gcb12665,
    author = "Lu, X. L. and Mao, Qinggong and Gilliam, Frank S. and Luo, Yiqi and Mo, Jiangming",
    title = "Nitrogen deposition contributes to soil acidification in tropical ecosystems",
    year = "2014",
    journal = "Global Change Biology",
    abstract = "Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long-term N deposition on soil acidification processes in tropical forests. We have established a long-term N-deposition experiment in an N-rich lowland tropical forest of Southern China since 2002 with N addition as NH4 NO3 of 0, 50, 100 and 150 kg N ha(-1) yr(-1). We measured soil acidification status and element leaching in soil drainage solution after 6-year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid-sensitive showing high acidification (pH(H2O) <4.0), negative water-extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8\%) throughout soil profiles. Long-term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable Al(3+), but increased cation exchange capacity (CEC). Nitrogen addition-induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20 cm depth, but not at 40 cm. Furthermore, there was no evidence that Al(3+) was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H(+) dominating changes of soil cation pool, an exhausted base cation pool, N-addition stimulating SOC production, and N saturation. Our results suggest that long-term N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future.",
    url = "https://doi.org/10.1111/gcb.12665",
    doi = "10.1111/gcb.12665",
    openalex = "W2171127082",
    references = "doi101016s0269749103000198, doi101021es0626133, doi101126science2214610520, larssen2000acid"
}

@article{huang2014research,
    author = "Huang, Juan and Mo, JiangMing and Zhang, Wei and Lu, XianKai",
    title = "Research on acidification in forest soil driven by atmospheric nitrogen deposition",
    year = "2014",
    journal = "Acta Ecologica Sinica",
    url = "https://doi.org/10.1016/j.chnaes.2014.10.002",
    doi = "10.1016/j.chnaes.2014.10.002",
    number = "6",
    openalex = "W2050649769",
    pages = "302-310",
    volume = "34",
    references = "doi1010079783642751684, doi101007bf02369968, doi101007s0044200605625, doi101016037811279406092w, doi101016jenvpol201008002, doi101038ngeo339, doi101126science1182570, doi101146annureves17110186001033, doi101146annurevpp29060178002455, doi1023071311067"
}

Abstract Elevated anthropogenic nitrogen (N) deposition has caused nitrate (NO 3 −) leaching, an indication of N saturation, in several temperate and boreal forests across the Northern Hemisphere. So far, the occurrence of N saturation in subtropical forests and its effects on the chemistry of the typically highly weathered soils, forest growth, and biodiversity have received little attention. Here we investigated N saturation and the effects of chronically high N inputs on soil and vegetation in a typical, subtropical Masson pine (Pinus massoniana) forest at Tieshanping, southwest China. Seven years of N flux data obtained in ambient conditions and in response to field manipulation, including a doubling of N input either as ammonium nitrate (NH 4 NO 3) or as sodium nitrate (NaNO 3) solution, resulted in a unique set of N balance data. Our data showed extreme N saturation with near‐quantitative leaching of NO 3 −, by far the dominant form of dissolved inorganic N in soil water. Even after 7 years, NH 4 +, added as NH 4 NO 3, was nearly fully converted to NO 3 −, thus giving rise to a major acid input into the soil. Despite the large acid input, the decrease in soil pH was insignificant, due to pH buffering caused by Al 3+ mobilization and enhanced SO 4 2− adsorption. In response to the NH 4 NO 3 ‐induced increase in soil acidification and N availability, ground vegetation showed significant reduction of abundance and diversity, while Masson pine growth further declined. By contrast, addition of NaNO 3 did not cause soil acidification. The comparison of NH 4 NO 3 treatment and NaNO 3 treatment indicated that pine growth decline was mainly attributed to acidification‐induced nutrient imbalance, while the loss in abundance of major ground species was the combining effect of N saturation and acidification. Therefore, N emission control is of primary importance to curb further acidification and eutrophication of forest soils in much of subtropical south China.

@article{doi1010022015jg003048,
    author = "Huang, Yongmei and Kang, Ronghua and Mulder, Jan and Zhang, Ting and Duan, Lei",
    title = "Nitrogen saturation, soil acidification, and ecological effects in a subtropical pine forest on acid soil in southwest China",
    year = "2015",
    journal = "Journal of Geophysical Research Biogeosciences",
    abstract = "Abstract Elevated anthropogenic nitrogen (N) deposition has caused nitrate (NO 3 −) leaching, an indication of N saturation, in several temperate and boreal forests across the Northern Hemisphere. So far, the occurrence of N saturation in subtropical forests and its effects on the chemistry of the typically highly weathered soils, forest growth, and biodiversity have received little attention. Here we investigated N saturation and the effects of chronically high N inputs on soil and vegetation in a typical, subtropical Masson pine (Pinus massoniana) forest at Tieshanping, southwest China. Seven years of N flux data obtained in ambient conditions and in response to field manipulation, including a doubling of N input either as ammonium nitrate (NH 4 NO 3) or as sodium nitrate (NaNO 3) solution, resulted in a unique set of N balance data. Our data showed extreme N saturation with near‐quantitative leaching of NO 3 −, by far the dominant form of dissolved inorganic N in soil water. Even after 7 years, NH 4 +, added as NH 4 NO 3, was nearly fully converted to NO 3 −, thus giving rise to a major acid input into the soil. Despite the large acid input, the decrease in soil pH was insignificant, due to pH buffering caused by Al 3+ mobilization and enhanced SO 4 2− adsorption. In response to the NH 4 NO 3 ‐induced increase in soil acidification and N availability, ground vegetation showed significant reduction of abundance and diversity, while Masson pine growth further declined. By contrast, addition of NaNO 3 did not cause soil acidification. The comparison of NH 4 NO 3 treatment and NaNO 3 treatment indicated that pine growth decline was mainly attributed to acidification‐induced nutrient imbalance, while the loss in abundance of major ground species was the combining effect of N saturation and acidification. Therefore, N emission control is of primary importance to curb further acidification and eutrophication of forest soils in much of subtropical south China.",
    url = "https://doi.org/10.1002/2015jg003048",
    doi = "10.1002/2015jg003048",
    openalex = "W2117651938",
    references = "doi101021es103426p"
}

Elevated anthropogenic nitrogen (N) deposition has become an important driver of soil acidification at both regional and global scales. It remains unclear, however, how long-term N deposition affects soil buffering capacity in tropical forest ecosystems and in ecosystems of contrasting land-use history. Here, we expand on a long-term N deposition experiment in three tropical forests that vary in land-use history (primary, secondary, and planted forests) in Southern China, with N addition as NH4NO3 of 0, 50, 100, and 150 kg N ha(-1) yr(-1), respectively. Results showed that all three forests were acid-sensitive ecosystems with poor soil buffering capacity, while the primary forest had higher base saturation and cation exchange capacity than others. However, long-term N addition significantly accelerated soil acidification and decreased soil buffering capacity in the primary forest, but not in the degraded secondary and planted forests. We suggest that ecosystem N status, influenced by different land-use history, is primarily responsible for these divergent responses. N-rich primary forests may be more sensitive to external N inputs than others with low N status, and should be given more attention under global changes in the future, because lack of nutrient cations is irreversible.

@article{doi101021es5047233,
    author = "Lu, X. L. and Mao, Qinggong and Mo, Jiangming and Gilliam, Frank S. and Zhou, Guoyi and Luo, Yiqi and Zhang, Wei and Huang, Juan",
    title = "Divergent Responses of Soil Buffering Capacity to Long-Term N Deposition in Three Typical Tropical Forests with Different Land-Use History",
    year = "2015",
    journal = "Environmental Science \& Technology",
    abstract = "Elevated anthropogenic nitrogen (N) deposition has become an important driver of soil acidification at both regional and global scales. It remains unclear, however, how long-term N deposition affects soil buffering capacity in tropical forest ecosystems and in ecosystems of contrasting land-use history. Here, we expand on a long-term N deposition experiment in three tropical forests that vary in land-use history (primary, secondary, and planted forests) in Southern China, with N addition as NH4NO3 of 0, 50, 100, and 150 kg N ha(-1) yr(-1), respectively. Results showed that all three forests were acid-sensitive ecosystems with poor soil buffering capacity, while the primary forest had higher base saturation and cation exchange capacity than others. However, long-term N addition significantly accelerated soil acidification and decreased soil buffering capacity in the primary forest, but not in the degraded secondary and planted forests. We suggest that ecosystem N status, influenced by different land-use history, is primarily responsible for these divergent responses. N-rich primary forests may be more sensitive to external N inputs than others with low N status, and should be given more attention under global changes in the future, because lack of nutrient cations is irreversible.",
    url = "https://doi.org/10.1021/es5047233",
    doi = "10.1021/es5047233",
    openalex = "W1978705250",
    references = "doi101016s0269749103000198"
}

Nitrogen (N) deposition-induced soil acidification has become a global problem. However, the response patterns of soil acidification to N addition and the underlying mechanisms remain far from clear. Here, we conducted a meta-analysis of 106 studies to reveal global patterns of soil acidification in responses to N addition. We found that N addition significantly reduced soil pH by 0.26 on average globally. However, the responses of soil pH varied with ecosystem types, N addition rate, N fertilization forms, and experimental durations. Soil pH decreased most in grassland, whereas boreal forest was not observed a decrease to N addition in soil acidification. Soil pH decreased linearly with N addition rates. Addition of urea and NH4NO3 contributed more to soil acidification than NH4-form fertilizer. When experimental duration was longer than 20 years, N addition effects on soil acidification diminished. Environmental factors such as initial soil pH, soil carbon and nitrogen content, precipitation, and temperature all influenced the responses of soil pH. Base cations of Ca2+, Mg2+ and K+ were critical important in buffering against N-induced soil acidification at the early stage. However, N addition has shifted global soils into the Al3+ buffering phase. Overall, this study indicates that acidification in global soils is very sensitive to N deposition, which is greatly modified by biotic and abiotic factors. Global soils are now at a buffering transition from base cations (Ca2+, Mg2+ and K+) to non-base cations (Mn2+ and Al3+). This calls our attention to care about the limitation of base cations and the toxic impact of nonbase cations for terrestrial ecosystems with N deposition.

@article{doi10108817489326102024019,
    author = "Tian, Dashuan and Niu, Shuli",
    title = "A global analysis of soil acidification caused by nitrogen addition",
    year = "2015",
    journal = "Environmental Research Letters",
    abstract = "Nitrogen (N) deposition-induced soil acidification has become a global problem. However, the response patterns of soil acidification to N addition and the underlying mechanisms remain far from clear. Here, we conducted a meta-analysis of 106 studies to reveal global patterns of soil acidification in responses to N addition. We found that N addition significantly reduced soil pH by 0.26 on average globally. However, the responses of soil pH varied with ecosystem types, N addition rate, N fertilization forms, and experimental durations. Soil pH decreased most in grassland, whereas boreal forest was not observed a decrease to N addition in soil acidification. Soil pH decreased linearly with N addition rates. Addition of urea and NH4NO3 contributed more to soil acidification than NH4-form fertilizer. When experimental duration was longer than 20 years, N addition effects on soil acidification diminished. Environmental factors such as initial soil pH, soil carbon and nitrogen content, precipitation, and temperature all influenced the responses of soil pH. Base cations of Ca2+, Mg2+ and K+ were critical important in buffering against N-induced soil acidification at the early stage. However, N addition has shifted global soils into the Al3+ buffering phase. Overall, this study indicates that acidification in global soils is very sensitive to N deposition, which is greatly modified by biotic and abiotic factors. Global soils are now at a buffering transition from base cations (Ca2+, Mg2+ and K+) to non-base cations (Mn2+ and Al3+). This calls our attention to care about the limitation of base cations and the toxic impact of nonbase cations for terrestrial ecosystems with N deposition.",
    url = "https://doi.org/10.1088/1748-9326/10/2/024019",
    doi = "10.1088/1748-9326/10/2/024019",
    openalex = "W2150284769"
}

The purpose of this study is to investigate the understanding on the acid-base, acid rain and soil acidification of the elementary students. The participants in the current study were 280 6th graders from a elementary school in Gyeongnam Province. A questionnaire consists of four categories: understanding of (a) acid-base basic knowledge, (b) acid rain and (c) soil acidification. (d) In addition, students were asked to comment about the introduction of the acid rain experiment in the science textbook. The results are as follows; First, the results regarding acid-base basic knowledge. They know the classification, characteristics, and properties of acid-based solutions well but they don't know the acid-base neutralization, examples using properties and application in real life. Second, the results regarding acid rain, students know the definition and damage of acid rain but they don't know the causing substances, emission source and way of solution of acid rain for lack of knowledge. Third, the results regarding soil acidification was the well-known part for the students because they had continued learning about the soil from the lesson of acid rain. Also, we looked into the difference in gender and region about the understanding of acid-base, acid rain and soil acidification. According to the gender of the data about the understanding of acid-base, acid rain and soil acidification, the percentage of correct answers of female was higher than male's. Also we expected that urban students were higher than rural students on the understanding of acid-base, acid rain and soil acidification, but the understanding of urban students were similar to rural students. Fourth, we got positive answers and negative answers to the introduction of acid rain experiment. Most of the positive opinion were I want to know a lot acid rain experiment", followed by "It is possible to prevent the risk of the damage and It seems to having fun and new order. Most of the negative opinion were Acid rain experiment may be difficult and complicated followed by Just a theory in the book is enough, Acid rain experiment were boring and not fun, Acid rain experiment is dangerous, There are many to study in this order.

@article{doi1013000jfmse20152761764,
    author = "KIM, Sung-Kyu",
    title = "An Understanding of Elementary School Students on the Acid-Base, Acid Rain and Soil Acidification",
    year = "2015",
    journal = "Journal of Fisheries and Marine Sciences Education",
    abstract = {The purpose of this study is to investigate the understanding on the acid-base, acid rain and soil acidification of the elementary students. The participants in the current study were 280 6th graders from a elementary school in Gyeongnam Province. A questionnaire consists of four categories: understanding of (a) acid-base basic knowledge, (b) acid rain and (c) soil acidification. (d) In addition, students were asked to comment about the introduction of the acid rain experiment in the science textbook. The results are as follows; First, the results regarding acid-base basic knowledge. They know the classification, characteristics, and properties of acid-based solutions well but they don't know the acid-base neutralization, examples using properties and application in real life. Second, the results regarding acid rain, students know the definition and damage of acid rain but they don't know the causing substances, emission source and way of solution of acid rain for lack of knowledge. Third, the results regarding soil acidification was the well-known part for the students because they had continued learning about the soil from the lesson of acid rain. Also, we looked into the difference in gender and region about the understanding of acid-base, acid rain and soil acidification. According to the gender of the data about the understanding of acid-base, acid rain and soil acidification, the percentage of correct answers of female was higher than male's. Also we expected that urban students were higher than rural students on the understanding of acid-base, acid rain and soil acidification, but the understanding of urban students were similar to rural students. Fourth, we got positive answers and negative answers to the introduction of acid rain experiment. Most of the positive opinion were I want to know a lot acid rain experiment", followed by "It is possible to prevent the risk of the damage and It seems to having fun and new order. Most of the negative opinion were Acid rain experiment may be difficult and complicated followed by Just a theory in the book is enough, Acid rain experiment were boring and not fun, Acid rain experiment is dangerous, There are many to study in this order.},
    url = "https://doi.org/10.13000/jfmse.2015.27.6.1764",
    doi = "10.13000/jfmse.2015.27.6.1764",
    openalex = "W2317982143",
    references = "goss2003a"
}

@article{doi101007s113560167365y,
    author = "Tao, Yu and Dan, Dai and He, Chengda and Xu, Qiujin and Wu, Fengchang",
    title = "Response of sediment calcium and magnesium species to the regional acid deposition in eutrophic Taihu Lake, China",
    year = "2016",
    journal = "Environmental Science and Pollution Research",
    url = "https://doi.org/10.1007/s11356-016-7365-y",
    doi = "10.1007/s11356-016-7365-y",
    openalex = "W2517322006",
    references = "goss2003a"
}

We review and synthesize the current state of knowledge regarding acid deposition and its environmental effects across Asia. The extent and magnitude of acid deposition in Asia became apparent only about one decade after this issue was well described in Europe and North America. In addition to the temperate zone, much of eastern and southern Asia is situated in the tropics and subtropics, climate zones hitherto little studied with respect to the effects of high loads of acid deposition. Surface waters across Asia are generally not sensitive to the effects of acid deposition, whereas soils in some regions are sensitive to acidification due to low mineral weathering. However, soil acidification was largely neutralized by such processes as base cation deposition, nitrate (NO3) denitrification, and sulfate (SO4 2) adsorption. Accompanying the decrease in S deposition in recent years, N deposition is of increasing concern in Asia. The acidifying effect of N deposition may be more important than S deposition in well drained tropical/subtropical soils due to high SO4 2 adsorption. The risk of regional soil acidification is a major threat in Eastern Asia, indicated by critical load exceedance in large areas.

@article{doi101016jatmosenv201607018,
    author = "Duan, Lei and Yu, Qian and Zhang, Qiang and Wang, Zifa and Pan, Yuepeng and Larssen, Thorjørn and Tang, Jie and Mulder, Jan",
    title = "Acid deposition in Asia: Emissions, deposition, and ecosystem effects",
    year = "2016",
    journal = "Atmospheric Environment",
    abstract = "We review and synthesize the current state of knowledge regarding acid deposition and its environmental effects across Asia. The extent and magnitude of acid deposition in Asia became apparent only about one decade after this issue was well described in Europe and North America. In addition to the temperate zone, much of eastern and southern Asia is situated in the tropics and subtropics, climate zones hitherto little studied with respect to the effects of high loads of acid deposition. Surface waters across Asia are generally not sensitive to the effects of acid deposition, whereas soils in some regions are sensitive to acidification due to low mineral weathering. However, soil acidification was largely neutralized by such processes as base cation deposition, nitrate (NO3) denitrification, and sulfate (SO4 2) adsorption. Accompanying the decrease in S deposition in recent years, N deposition is of increasing concern in Asia. The acidifying effect of N deposition may be more important than S deposition in well drained tropical/subtropical soils due to high SO4 2 adsorption. The risk of regional soil acidification is a major threat in Eastern Asia, indicated by critical load exceedance in large areas.",
    url = "https://doi.org/10.1016/j.atmosenv.2016.07.018",
    doi = "10.1016/j.atmosenv.2016.07.018",
    openalex = "W2470399159",
    references = "doi101016jatmosenv201310060, doi101016jenvpol201008002, doi101016jscitotenv201306108, doi101021es0626133, doi101021es103426p, doi101021es901430n, doi101038nature11917, doi101111gcb12665, doi101111gcb13333, doi101111j13652486200901950x, doi101126science1182570, doi101126science23648081559, doi1016410006356820030530375indatn20co2, doi105194acp1063112010, doi105194acp1111012011, doi105194acp13110192013, larssen2000acid, openalexw168580091"
}

@article{doi101016jenvsoft201601009,
    author = "Bonten, L.T.C. and Reinds, G.J. and Posch, Maximilian",
    title = "A model to calculate effects of atmospheric deposition on soil acidification, eutrophication and carbon sequestration",
    year = "2016",
    journal = "Environmental Modelling \& Software",
    url = "https://doi.org/10.1016/j.envsoft.2016.01.009",
    doi = "10.1016/j.envsoft.2016.01.009",
    openalex = "W2272995397",
    references = "doi105194hess54992001"
}

In forests of the humid subtropics of China, chronically elevated nitrogen (N) deposition, predominantly as ammonium (NH 4 +), causes significant nitrate (NO 3 -) leaching from well-drained acid forest soils on hill slopes (HS), whereas significant retention of NO 3 - occurs in near-stream environments (groundwater discharge zones, GDZ). To aid our understanding of N transformations on the catchment level, we studied spatial and temporal variabilities of concentration and natural abundance (δ 15 N and δ 18 O) of nitrate (NO 3 -) in soil pore water along a hydrological continuum in the N-saturated Tieshanping (TSP) catchment, southwest China. Our data show that effective removal of atmogenic NH 4 + and production of NO 3 - in soils on HS were associated with a significant decrease in δ 15 N-NO 3 -, suggesting efficient nitrification despite low soil pH. The concentration of NO 3 - declined sharply along the hydrological flow path in the GDZ. This decline was associated with a significant increase in both δ 15 N and δ 18 O of residual NO 3 -, providing evidence that the GDZ acts as an N sink due to denitrification. The observed apparent 15 N enrichment factor (ε) of NO 3 - of about -5‰ in the GDZ is similar to values previously reported for efficient denitrification in riparian and groundwater systems. Episode studies in the summers of 2009, 2010 and 2013 revealed that the spatial pattern of δ 15 N and δ 18 O-NO 3 - in soil water was remarkably similar from year to year. The importance of denitrification as a major N sink was also seen at the catchment scale, as largest δ 15 N-NO 3 - values in stream water were observed at lowest discharge, confirming the importance of the relatively small GDZ for N removal under base flow conditions. This study, explicitly recognizing hydrologically connected landscape elements, reveals an overlooked but robust N sink in N-saturated, subtropical forests with important implications for regional N budgets.

@article{doi101111gcb13333,
    author = "Yu, Longfei and Zhu, Jing and Mulder, Jan and Dörsch, Peter",
    title = "Multiyear dual nitrate isotope signatures suggest that N‐saturated subtropical forested catchments can act as robust N sinks",
    year = "2016",
    journal = "Global Change Biology",
    abstract = "In forests of the humid subtropics of China, chronically elevated nitrogen (N) deposition, predominantly as ammonium (NH 4 +), causes significant nitrate (NO 3 -) leaching from well-drained acid forest soils on hill slopes (HS), whereas significant retention of NO 3 - occurs in near-stream environments (groundwater discharge zones, GDZ). To aid our understanding of N transformations on the catchment level, we studied spatial and temporal variabilities of concentration and natural abundance (δ 15 N and δ 18 O) of nitrate (NO 3 -) in soil pore water along a hydrological continuum in the N-saturated Tieshanping (TSP) catchment, southwest China. Our data show that effective removal of atmogenic NH 4 + and production of NO 3 - in soils on HS were associated with a significant decrease in δ 15 N-NO 3 -, suggesting efficient nitrification despite low soil pH. The concentration of NO 3 - declined sharply along the hydrological flow path in the GDZ. This decline was associated with a significant increase in both δ 15 N and δ 18 O of residual NO 3 -, providing evidence that the GDZ acts as an N sink due to denitrification. The observed apparent 15 N enrichment factor (ε) of NO 3 - of about -5‰ in the GDZ is similar to values previously reported for efficient denitrification in riparian and groundwater systems. Episode studies in the summers of 2009, 2010 and 2013 revealed that the spatial pattern of δ 15 N and δ 18 O-NO 3 - in soil water was remarkably similar from year to year. The importance of denitrification as a major N sink was also seen at the catchment scale, as largest δ 15 N-NO 3 - values in stream water were observed at lowest discharge, confirming the importance of the relatively small GDZ for N removal under base flow conditions. This study, explicitly recognizing hydrologically connected landscape elements, reveals an overlooked but robust N sink in N-saturated, subtropical forests with important implications for regional N budgets.",
    url = "https://doi.org/10.1111/gcb.13333",
    doi = "10.1111/gcb.13333",
    openalex = "W2344280798",
    references = "doi101007bf02374138, doi101016jscitotenv201306108, doi101021ac010088e, doi101021ac020113w, doi101038nature06592, doi101038nature11917, doi101126science1136674, doi101201noe0849338304ch410, doi1016410006356820030530341tnc20co2, doi1018901051076119970070737haotgn20co2, doi102136sssaj198403615995004800060013x"
}

@article{zhu2016the,
    author = "Zhu, Qichao and De Vries, Wim and Liu, Xuejun and Zeng, Mufan and Hao, Tianxiang and Du, Enzai and Zhang, Fusuo and Shen, Jianbo",
    title = "The contribution of atmospheric deposition and forest harvesting to forest soil acidification in China since 1980",
    year = "2016",
    journal = "Atmospheric Environment",
    url = "https://doi.org/10.1016/j.atmosenv.2016.04.023",
    doi = "10.1016/j.atmosenv.2016.04.023",
    openalex = "W2342090496",
    pages = "215-222",
    volume = "146",
    references = "doi101007bf02369968, doi101016jhal201110027, doi101016jscitotenv201306108, doi101021es103426p, doi101038299548a0, doi101038307599a0, doi101038nature11917, doi101038ngeo339, doi101126science1058629, doi101126science1182570, doi101126science2785339827, doi105194acp1111012011"
}

@article{doi101016jenvpol201708014,
    author = "Yu, Haili and He, Nianpeng and Wang, Qiufeng and Zhu, Jianxing and Gao, Yang and Zhang, Yunhai and Jia, Yanlong and Yu, Guirui",
    title = "Development of atmospheric acid deposition in China from the 1990s to the 2010s",
    year = "2017",
    journal = "Environmental Pollution",
    url = "https://doi.org/10.1016/j.envpol.2017.08.014",
    doi = "10.1016/j.envpol.2017.08.014",
    openalex = "W2751956264",
    references = "doi101016jatmosenv201607018, doi101016s0269749103000198, openalexw2186096382"
}

@article{doi101016jscitotenv201706044,
    author = "Du, Enzai and Dong, Dan and Zeng, Xuetong and Sun, Zhengzhong and Jiang, Xiaofei and de Vries, W.",
    title = "Direct effect of acid rain on leaf chlorophyll content of terrestrial plants in China",
    year = "2017",
    journal = "The Science of The Total Environment",
    url = "https://doi.org/10.1016/j.scitotenv.2017.06.044",
    doi = "10.1016/j.scitotenv.2017.06.044",
    openalex = "W2733737944",
    references = "doi101016jatmosenv201607018, openalexw2186096382, zhu2016the"
}

Abstract. Chronically elevated nitrogen (N) deposition has led to severe nutrient imbalance in forest soils. Particularly in tropical and subtropical forest ecosystems, increasing N loading has aggravated phosphorus (P) limitation of biomass production, and has resulted in elevated emissions of nitrous oxide (N2O) and reduced uptake of methane (CH4), both of which are important greenhouse gases. Yet, the interactions of N and P and their effects on greenhouse gas emissions remain elusive. Here, we report N2O and CH4 emissions together with soil N and P data for a period of 18 months following a single P addition (79 kg P ha−1, as NaH2PO4 powder) to an N-saturated, Masson pine-dominated forest soil at TieShanPing (TSP), Chongqing, south-western (SW) China. We observed a significant decline in both nitrate (NO3−) concentrations in soil water (5 and 20 cm depths) and in soil N2O emissions, following P application. We hypothesise that enhanced N uptake by plants in response to P addition, resulted in less available NO3− for denitrification. By contrast to most other forest ecosystems, TSP is a net source of CH4. P addition significantly decreased CH4 emissions and turned the soil from a net source into a net sink. Based on our observation and previous studies in South America and China, we believe that P addition relieves N inhibition of CH4 oxidation. Within the 1.5 years after P addition, no significant increase of forest growth was observed and P stimulation of forest N uptake by understorey vegetation remains to be confirmed. Our study indicates that P fertilisation of N-saturated, subtropical forest soils may mitigate N2O and CH4 emissions, in addition to alleviating nutrient imbalances and reducing losses of N through NO3− leaching.

@article{doi105194bg1430972017,
    author = "Yu, Longfei and Wang, Yihao and Zhang, Xiaoshan and Dörsch, Peter and Mulder, Jan",
    title = "Phosphorus addition mitigates N 2 O and CH 4 emissions in N-saturated subtropical forest, SW China",
    year = "2017",
    journal = "Biogeosciences",
    abstract = "Abstract. Chronically elevated nitrogen (N) deposition has led to severe nutrient imbalance in forest soils. Particularly in tropical and subtropical forest ecosystems, increasing N loading has aggravated phosphorus (P) limitation of biomass production, and has resulted in elevated emissions of nitrous oxide (N2O) and reduced uptake of methane (CH4), both of which are important greenhouse gases. Yet, the interactions of N and P and their effects on greenhouse gas emissions remain elusive. Here, we report N2O and CH4 emissions together with soil N and P data for a period of 18 months following a single P addition (79 kg P ha−1, as NaH2PO4 powder) to an N-saturated, Masson pine-dominated forest soil at TieShanPing (TSP), Chongqing, south-western (SW) China. We observed a significant decline in both nitrate (NO3−) concentrations in soil water (5 and 20 cm depths) and in soil N2O emissions, following P application. We hypothesise that enhanced N uptake by plants in response to P addition, resulted in less available NO3− for denitrification. By contrast to most other forest ecosystems, TSP is a net source of CH4. P addition significantly decreased CH4 emissions and turned the soil from a net source into a net sink. Based on our observation and previous studies in South America and China, we believe that P addition relieves N inhibition of CH4 oxidation. Within the 1.5 years after P addition, no significant increase of forest growth was observed and P stimulation of forest N uptake by understorey vegetation remains to be confirmed. Our study indicates that P fertilisation of N-saturated, subtropical forest soils may mitigate N2O and CH4 emissions, in addition to alleviating nutrient imbalances and reducing losses of N through NO3− leaching.",
    url = "https://doi.org/10.5194/bg-14-3097-2017",
    doi = "10.5194/bg-14-3097-2017",
    openalex = "W2548155793",
    references = "doi101111gcb13333"
}

Abstract. The nitrate to ammonium ratios in nitrogen (N) compounds in wet atmospheric deposits have increased over the recent past, which is a cause for some concern as the individual effects of nitrate and ammonium deposition on the biomass of different soil microbial communities and enzyme activities are still poorly defined. We established a field experiment and applied ammonium (NH4Cl) and nitrate (NaNO3) at monthly intervals over a period of 4 years. We collected soil samples from the ammonium and nitrate treatments and control plots in three different seasons, namely spring, summer, and fall, to evaluate the how the biomass of different soil microbial communities and enzyme activities responded to the ammonium (NH4Cl) and nitrate (NaNO3) applications. Our results showed that the total contents of phospholipid fatty acids (PLFAs) decreased by 24 and 11 % in the ammonium and nitrate treatments, respectively. The inhibitory effects of ammonium on Gram-positive bacteria (G+) and bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi (AMF) PLFA contents ranged from 14 to 40 % across the three seasons. We also observed that the absolute activities of C, N, and P hydrolyses and oxidases were inhibited by ammonium and nitrate, but that nitrate had stronger inhibitory effects on the activities of acid phosphatase (AP) than ammonium. The activities of N-acquisition specific enzymes (enzyme activities normalized by total PLFA contents) were about 21 and 43 % lower in the ammonium and nitrate treatments than in the control, respectively. However, the activities of P-acquisition specific enzymes were about 19 % higher in the ammonium treatment than in the control. Using redundancy analysis (RDA), we found that the measured C, N, and P hydrolysis and polyphenol oxidase (PPO) activities were positively correlated with the soil pH and ammonium contents, but were negatively correlated with the nitrate contents. The PLFA biomarker contents were positively correlated with soil pH, soil organic carbon (SOC), and total N contents, but were negatively correlated with the ammonium contents. The soil enzyme activities varied seasonally, and were highest in March and lowest in October. In contrast, the contents of the microbial PLFA biomarkers were higher in October than in March and June. Ammonium may inhibit the contents of PLFA biomarkers more strongly than nitrate because of acidification. This study has provided useful information about the effects of ammonium and nitrate on soil microbial communities and enzyme activities.

@article{doi105194bg1448152017,
    author = "Zhang, Chuang and Zhang, Xinyu and Zou, Hongtao and Kou, Liang and Yang, Yang and Wen, Xue-Fa and Li, Shenggong and Wang, Huimin and Sun, Xiaomin",
    title = "Contrasting effects of ammonium and nitrate additions on the biomass of soil microbial communities and enzyme activities in subtropical China",
    year = "2017",
    journal = "Biogeosciences",
    abstract = "Abstract. The nitrate to ammonium ratios in nitrogen (N) compounds in wet atmospheric deposits have increased over the recent past, which is a cause for some concern as the individual effects of nitrate and ammonium deposition on the biomass of different soil microbial communities and enzyme activities are still poorly defined. We established a field experiment and applied ammonium (NH4Cl) and nitrate (NaNO3) at monthly intervals over a period of 4 years. We collected soil samples from the ammonium and nitrate treatments and control plots in three different seasons, namely spring, summer, and fall, to evaluate the how the biomass of different soil microbial communities and enzyme activities responded to the ammonium (NH4Cl) and nitrate (NaNO3) applications. Our results showed that the total contents of phospholipid fatty acids (PLFAs) decreased by 24 and 11 \% in the ammonium and nitrate treatments, respectively. The inhibitory effects of ammonium on Gram-positive bacteria (G+) and bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi (AMF) PLFA contents ranged from 14 to 40 \% across the three seasons. We also observed that the absolute activities of C, N, and P hydrolyses and oxidases were inhibited by ammonium and nitrate, but that nitrate had stronger inhibitory effects on the activities of acid phosphatase (AP) than ammonium. The activities of N-acquisition specific enzymes (enzyme activities normalized by total PLFA contents) were about 21 and 43 \% lower in the ammonium and nitrate treatments than in the control, respectively. However, the activities of P-acquisition specific enzymes were about 19 \% higher in the ammonium treatment than in the control. Using redundancy analysis (RDA), we found that the measured C, N, and P hydrolysis and polyphenol oxidase (PPO) activities were positively correlated with the soil pH and ammonium contents, but were negatively correlated with the nitrate contents. The PLFA biomarker contents were positively correlated with soil pH, soil organic carbon (SOC), and total N contents, but were negatively correlated with the ammonium contents. The soil enzyme activities varied seasonally, and were highest in March and lowest in October. In contrast, the contents of the microbial PLFA biomarkers were higher in October than in March and June. Ammonium may inhibit the contents of PLFA biomarkers more strongly than nitrate because of acidification. This study has provided useful information about the effects of ammonium and nitrate on soil microbial communities and enzyme activities.",
    url = "https://doi.org/10.5194/bg-14-4815-2017",
    doi = "10.5194/bg-14-4815-2017",
    openalex = "W2767056529",
    references = "huang2014research"
}

Abstract Soil nitrogen (N), phosphorus (P), potassium (K), and pH are important determinants and indicators of soil fertility and quality. Especially in forest, these soil properties are highly variable in space and time. However, more information on these properties in subtropical forests is needed to improve soil nutrients management and to sustain the productivity of subtropical forests. We collected a total of 838 forest topsoil samples (0–30 cm in depth) based on a 4‐km (E‐W) × 6‐km (S‐N) grid system in subtropical China. Geostatistics (i.e., global and local Moran's I) and geographical information system (GIS) techniques were applied to reveal the spatial distribution of N, P, and K contents and pH in subtropical forest soils. All the measured properties were highly variable. Soil N contents ranged from 9.55 mg kg −1 to 862.40 mg kg −1, P contents from 0.10 mg kg −1 to 195.40 mg kg −1, K contents from 10.00 mg kg −1 to 390.00 mg kg −1, and pH values from 2.69 to 8.09. The soil N, P and K contents correlated positively with soil organic carbon (SOC), while soil pH correlated negatively with SOC (P < 0.05). Global Moran's I revealed that soil N, P, and K contents and pH had significant positive spatial autocorrelations, and clear spatial patterns were identified based on local Moran's I. An exponential model was the best fitted model for soil N, P, K contents and pH. Spatial dependence was moderate for all studied soil variables, indicating that both intrinsic and extrinsic factors played a vital role in spatial heterogeneity. Distribution maps showed that soil N and K had similar spatial distribution patterns: a low value area surrounded by bands of higher values. A large‐scale low content area was observed in the spatial distribution map of soil P. An opposite trend was found for the spatial pattern of soil pH. The spatial distribution maps provide useful information for sustainable forest and environment management in subtropical China.

@article{doi101002jpln201800134,
    author = "Dai, Wei and Li, Yuhuan and Fu, Weijun and Jiang, Peikun and Zhao, Keli and Li, Yongfu and Penttinen, Petri",
    title = "Spatial variability of soil nutrients in forest areas: A case study from subtropical China",
    year = "2018",
    journal = "Journal of Plant Nutrition and Soil Science",
    abstract = "Abstract Soil nitrogen (N), phosphorus (P), potassium (K), and pH are important determinants and indicators of soil fertility and quality. Especially in forest, these soil properties are highly variable in space and time. However, more information on these properties in subtropical forests is needed to improve soil nutrients management and to sustain the productivity of subtropical forests. We collected a total of 838 forest topsoil samples (0–30 cm in depth) based on a 4‐km (E‐W) × 6‐km (S‐N) grid system in subtropical China. Geostatistics (i.e., global and local Moran's I) and geographical information system (GIS) techniques were applied to reveal the spatial distribution of N, P, and K contents and pH in subtropical forest soils. All the measured properties were highly variable. Soil N contents ranged from 9.55 mg kg −1 to 862.40 mg kg −1, P contents from 0.10 mg kg −1 to 195.40 mg kg −1, K contents from 10.00 mg kg −1 to 390.00 mg kg −1, and pH values from 2.69 to 8.09. The soil N, P and K contents correlated positively with soil organic carbon (SOC), while soil pH correlated negatively with SOC (P < 0.05). Global Moran's I revealed that soil N, P, and K contents and pH had significant positive spatial autocorrelations, and clear spatial patterns were identified based on local Moran's I. An exponential model was the best fitted model for soil N, P, K contents and pH. Spatial dependence was moderate for all studied soil variables, indicating that both intrinsic and extrinsic factors played a vital role in spatial heterogeneity. Distribution maps showed that soil N and K had similar spatial distribution patterns: a low value area surrounded by bands of higher values. A large‐scale low content area was observed in the spatial distribution map of soil P. An opposite trend was found for the spatial pattern of soil pH. The spatial distribution maps provide useful information for sustainable forest and environment management in subtropical China.",
    url = "https://doi.org/10.1002/jpln.201800134",
    doi = "10.1002/jpln.201800134",
    openalex = "W2890704164",
    references = "doi1010029781119115151, doi101016jagee201105002, doi101016jforeco200508015, doi101016jgeoderma200809015, doi101016jgeoderma200901021, doi101016jgeoderma201212011, doi101016jscitotenv201306108, doi101016s0065211308004070, doi101126science1182570, doi101198tech2001s65, doi102136sssaj199403615995005800050033x"
}

@article{doi101007s4174201800840,
    author = "Debnath, Biswojit and Irshad, Muhammad Atif and Mitra, Sangeeta and Li, Min and Rizwan, Hafiz Muhammad and Liu, Shuang and Pan, Tenfei and Qiu, Dongliang",
    title = "Acid Rain Deposition Modulates Photosynthesis, Enzymatic and Non-enzymatic Antioxidant Activities in Tomato",
    year = "2018",
    journal = "International Journal of Environmental Research",
    url = "https://doi.org/10.1007/s41742-018-0084-0",
    doi = "10.1007/s41742-018-0084-0",
    openalex = "W2795145872",
    references = "doi101039c0em00116c"
}

@article{doi101016jscitotenv201712245,
    author = "Vuorenmaa, Jussi and Augustaitis, Algirdas and Beudert, Burkhard and Bochenek, Witold and Clarke, Nicholas and de Wit, Heleen A. and Dirnböck, Thomas and Frey, Jane and Hakola, Hannele and Kleemola, Sirpa and Kobler, Johannes and Krám, Pavel and Lindroos, Antti‐Jussi and Lundin, Lars and Löfgren, Stefan and Marchetto, Aldo and Pecka, Tomasz and Schulte‐Bisping, Hubert and Skotak, Krzysztof and Srybny, Anatoly and Szpikowski, Józef and Ukonmaanaho, Liisa and Váňa, Milan and Åkerblom, Staffan and Forsius, Martin",
    title = "Long-term changes (1990–2015) in the atmospheric deposition and runoff water chemistry of sulphate, inorganic nitrogen and acidity for forested catchments in Europe in relation to changes in emissions and hydrometeorological conditions",
    year = "2018",
    journal = "The Science of The Total Environment",
    url = "https://doi.org/10.1016/j.scitotenv.2017.12.245",
    doi = "10.1016/j.scitotenv.2017.12.245",
    openalex = "W2783651040",
    references = "doi101007bf01186169"
}

Abstract Acid deposition arising from sulphur (S) and nitrogen (N) emissions from fossil fuel combustion and agriculture has contributed to the acidification of terrestrial ecosystems in many regions globally. However, in Europe and North America, S deposition has greatly decreased in recent decades due to emissions controls. In this study, we assessed the response of soil solution chemistry in mineral horizons of European forests to these changes. Trends in pH, acid neutralizing capacity (ANC), major ions, total aluminium (Al tot) and dissolved organic carbon were determined for the period 1995–2012. Plots with at least 10 years of observations from the ICP Forests monitoring network were used. Trends were assessed for the upper mineral soil (10–20 cm, 104 plots) and subsoil (40–80 cm, 162 plots). There was a large decrease in the concentration of sulphate () in soil solution; over a 10‐year period (2000–2010), decreased by 52% at 10–20 cm and 40% at 40–80 cm. Nitrate was unchanged at 10–20 cm but decreased at 40–80 cm. The decrease in acid anions was accompanied by a large and significant decrease in the concentration of the nutrient base cations: calcium, magnesium and potassium (Bc = Ca 2+ + Mg 2+ + K +) and Al tot over the entire dataset. The response of soil solution acidity was nonuniform. At 10–20 cm, ANC increased in acid‐sensitive soils (base saturation ≤10%) indicating a recovery, but ANC decreased in soils with base saturation >10%. At 40–80 cm, ANC remained unchanged in acid‐sensitive soils (base saturation ≤20%, ≤ 4.5) and decreased in better‐buffered soils (base saturation >20%, > 4.5). In addition, the molar ratio of Bc to Al tot either did not change or decreased. The results suggest a long‐time lag between emission abatement and changes in soil solution acidity and underline the importance of long‐term monitoring in evaluating ecosystem response to decreases in deposition.

@article{doi101111gcb14156,
    author = "Johnson, James and Pannatier, Elisabeth Graf and Carnicelli, Stefano and Cecchini, Guia and Clarke, Nicholas and Cools, Nathalie and Hansen, Karin and Meesenburg, Henning and Nieminen, Tiina M. and Karlsson, Gunilla Pihl and Titeux, Hugues and Vanguelova, Elena and Verstraeten, Arne and Vesterdal, Lars and Waldner, Peter and Jonard, Mathieu",
    title = "The response of soil solution chemistry in European forests to decreasing acid deposition",
    year = "2018",
    journal = "Global Change Biology",
    abstract = "Abstract Acid deposition arising from sulphur (S) and nitrogen (N) emissions from fossil fuel combustion and agriculture has contributed to the acidification of terrestrial ecosystems in many regions globally. However, in Europe and North America, S deposition has greatly decreased in recent decades due to emissions controls. In this study, we assessed the response of soil solution chemistry in mineral horizons of European forests to these changes. Trends in pH, acid neutralizing capacity (ANC), major ions, total aluminium (Al tot) and dissolved organic carbon were determined for the period 1995–2012. Plots with at least 10 years of observations from the ICP Forests monitoring network were used. Trends were assessed for the upper mineral soil (10–20 cm, 104 plots) and subsoil (40–80 cm, 162 plots). There was a large decrease in the concentration of sulphate () in soil solution; over a 10‐year period (2000–2010), decreased by 52\% at 10–20 cm and 40\% at 40–80 cm. Nitrate was unchanged at 10–20 cm but decreased at 40–80 cm. The decrease in acid anions was accompanied by a large and significant decrease in the concentration of the nutrient base cations: calcium, magnesium and potassium (Bc = Ca 2+ + Mg 2+ + K +) and Al tot over the entire dataset. The response of soil solution acidity was nonuniform. At 10–20 cm, ANC increased in acid‐sensitive soils (base saturation ≤10\%) indicating a recovery, but ANC decreased in soils with base saturation >10\%. At 40–80 cm, ANC remained unchanged in acid‐sensitive soils (base saturation ≤20\%, ≤ 4.5) and decreased in better‐buffered soils (base saturation >20\%, > 4.5). In addition, the molar ratio of Bc to Al tot either did not change or decreased. The results suggest a long‐time lag between emission abatement and changes in soil solution acidity and underline the importance of long‐term monitoring in evaluating ecosystem response to decreases in deposition.",
    url = "https://doi.org/10.1111/gcb.14156",
    doi = "10.1111/gcb.14156",
    openalex = "W2794709645",
    references = "doi101021es103426p, zhu2016the"
}

Acid rain (AR) is a serious global environmental issue causing physio-morphological changes in plants. Melatonin, as an indoleamine molecule, has been known to mediate many physiological processes in plants under different kinds of environmental stress. However, the role of melatonin in acid rain stress tolerance remains inexpressible. This study investigated the possible role of melatonin on different physiological responses involving reactive oxygen species (ROS) metabolism in tomato plants under simulated acid rain (SAR) stress. SAR stress caused the inhibition of growth, damaged the grana lamella of the chloroplast, photosynthesis, and increased accumulation of ROS and lipid peroxidation in tomato plants. To cope the detrimental effect of SAR stress, plants under SAR condition had increased both enzymatic and nonenzymatic antioxidant substances compared with control plants. But such an increase in the antioxidant activities were incapable of inhibiting the destructive effect of SAR stress. Meanwhile, melatonin treatment increased SAR-stress tolerance by repairing the grana lamella of the chloroplast, improving photosynthesis and antioxidant activities compared with those in SAR-stressed plants. However, these possible effects of melatonin are dependent on concentration. Moreover, our study suggests that 100-μM melatonin treatment improved the SAR-stress tolerance by increasing photosynthesis and ROS scavenging antioxidant activities in tomato plants.

@article{doi103390molecules23020388,
    author = "Debnath, Biswojit and Hussain, Mubasher and Irshad, Muhammad Atif and Mitra, Sangeeta and Li, Min and Liu, Shuang and Qiu, Dongliang",
    title = "Exogenous Melatonin Mitigates Acid Rain Stress to Tomato Plants through Modulation of Leaf Ultrastructure, Photosynthesis and Antioxidant Potential",
    year = "2018",
    journal = "Molecules",
    abstract = "Acid rain (AR) is a serious global environmental issue causing physio-morphological changes in plants. Melatonin, as an indoleamine molecule, has been known to mediate many physiological processes in plants under different kinds of environmental stress. However, the role of melatonin in acid rain stress tolerance remains inexpressible. This study investigated the possible role of melatonin on different physiological responses involving reactive oxygen species (ROS) metabolism in tomato plants under simulated acid rain (SAR) stress. SAR stress caused the inhibition of growth, damaged the grana lamella of the chloroplast, photosynthesis, and increased accumulation of ROS and lipid peroxidation in tomato plants. To cope the detrimental effect of SAR stress, plants under SAR condition had increased both enzymatic and nonenzymatic antioxidant substances compared with control plants. But such an increase in the antioxidant activities were incapable of inhibiting the destructive effect of SAR stress. Meanwhile, melatonin treatment increased SAR-stress tolerance by repairing the grana lamella of the chloroplast, improving photosynthesis and antioxidant activities compared with those in SAR-stressed plants. However, these possible effects of melatonin are dependent on concentration. Moreover, our study suggests that 100-μM melatonin treatment improved the SAR-stress tolerance by increasing photosynthesis and ROS scavenging antioxidant activities in tomato plants.",
    url = "https://doi.org/10.3390/molecules23020388",
    doi = "10.3390/molecules23020388",
    openalex = "W2791775393",
    references = "doi101006abio19960292, doi101007978140203218912, doi101007bf00018060, doi101007s004250050524, doi1010160003269771903708, doi101016jplaphy201212012, doi101016s0168945299001971, doi101039c0em00116c, doi101042bst0110591, doi101093jexbot51345659, doi101093jxb51345659, doi101093oxfordjournalspcpa076232"
}

Acid rain is a serious worldwide environmental problem which reduces the growth and yield of crops. Melatonin, as a pleiotropic molecule has been known to improve stress tolerance by limiting the oxidative damage of plants exposed to adverse environments. However, the role of exogenous melatonin particularly on the yield and antioxidant compounds in tomato fruits under abiotic stress condition remains inexpressible. This observation aims to identify the influence of melatonin treatment under simulated acid rain (SAR) condition on fruit qualities, phenolics, flavonoids, and carotenoids concentration in fruits, and yield of tomatoes. Our study results showed that the fruits of SAR-stressed plants had higher quality traits and antioxidant bioactive compounds by increasing antioxidant activities against SAR-induced oxidative stress compared with fruits of control plants. Nonetheless, these improvements to antioxidant activities in fruits under SAR-condition remained unable to prevent the reduction of the yield. However, SAR-stressed plants treated by melatonin exhibited upgradation on the fruit quality traits, antioxidant compounds and yield attributes through accelerating oxidant-scavenging antioxidant actions in fruits compared with fruits of SAR-stressed plants. Meanwhile, our results suggest that exogenous melatonin plays an important role in improvement of bioactive compounds and yield traits in tomato fruits through regulating antioxidant system.

@article{doi103390molecules23081868,
    author = "Debnath, Biswojit and Hussain, Mubasher and Li, Min and Lu, Xiaocao and Sun, Yueting and Qiu, Dongliang",
    title = "Exogenous Melatonin Improves Fruit Quality Features, Health Promoting Antioxidant Compounds and Yield Traits in Tomato Fruits under Acid Rain Stress",
    year = "2018",
    journal = "Molecules",
    abstract = "Acid rain is a serious worldwide environmental problem which reduces the growth and yield of crops. Melatonin, as a pleiotropic molecule has been known to improve stress tolerance by limiting the oxidative damage of plants exposed to adverse environments. However, the role of exogenous melatonin particularly on the yield and antioxidant compounds in tomato fruits under abiotic stress condition remains inexpressible. This observation aims to identify the influence of melatonin treatment under simulated acid rain (SAR) condition on fruit qualities, phenolics, flavonoids, and carotenoids concentration in fruits, and yield of tomatoes. Our study results showed that the fruits of SAR-stressed plants had higher quality traits and antioxidant bioactive compounds by increasing antioxidant activities against SAR-induced oxidative stress compared with fruits of control plants. Nonetheless, these improvements to antioxidant activities in fruits under SAR-condition remained unable to prevent the reduction of the yield. However, SAR-stressed plants treated by melatonin exhibited upgradation on the fruit quality traits, antioxidant compounds and yield attributes through accelerating oxidant-scavenging antioxidant actions in fruits compared with fruits of SAR-stressed plants. Meanwhile, our results suggest that exogenous melatonin plays an important role in improvement of bioactive compounds and yield traits in tomato fruits through regulating antioxidant system.",
    url = "https://doi.org/10.3390/molecules23081868",
    doi = "10.3390/molecules23081868",
    openalex = "W2884193706",
    references = "doi101016jplaphy201212012, doi101039c0em00116c"
}

Abstract To elucidate the dynamics of aluminium (Al), an element potentially toxic and strongly affected by acidification processes, in soils, we selected two regions that were similar in relief, soil types, and vegetation cover but differed markedly in their history of acid precipitation: the Jizerské Mountains (anthropogenically acidified) and the Novohradské Mountains (naturally acidified) in the Czech Republic. The levels of Al forms (exchangeable and organically bound) associated with different environmental impacts were measured and univalent, divalent and trivalent Al species were quantified using HPLC/IC. Exchangeable and organically bound Al concentrations were higher in the anthropogenically acidified area. Only the concentrations of the least-dangerous species, the univalent, in organic soil horizons were similar for both mountains. The concentrations of exchangeable Al forms were correlated with Ca concentrations and with pH in the organic horizon. The known relationship of Al with soil pH was stronger in the mineral horizons. Relationships of exchangeable Al forms concentrations with sulphur concentrations or even more with the sulphur calcium molar ratio were found only in the Jizerské Mountains, not in the Novohradské. Generally, the obtained results support the hypothesis that mechanisms differed between natural and anthropogenic acidification.

@article{doi101007s11676019010611,
    author = "Pavlů, Lenka and Borůvka, Luboš and Drábek, Ondřej and Nikodem, Antonín",
    title = "Effect of natural and anthropogenic acidification on aluminium distribution in forest soils of two regions in the Czech Republic",
    year = "2019",
    journal = "Journal of Forestry Research",
    abstract = "Abstract To elucidate the dynamics of aluminium (Al), an element potentially toxic and strongly affected by acidification processes, in soils, we selected two regions that were similar in relief, soil types, and vegetation cover but differed markedly in their history of acid precipitation: the Jizerské Mountains (anthropogenically acidified) and the Novohradské Mountains (naturally acidified) in the Czech Republic. The levels of Al forms (exchangeable and organically bound) associated with different environmental impacts were measured and univalent, divalent and trivalent Al species were quantified using HPLC/IC. Exchangeable and organically bound Al concentrations were higher in the anthropogenically acidified area. Only the concentrations of the least-dangerous species, the univalent, in organic soil horizons were similar for both mountains. The concentrations of exchangeable Al forms were correlated with Ca concentrations and with pH in the organic horizon. The known relationship of Al with soil pH was stronger in the mineral horizons. Relationships of exchangeable Al forms concentrations with sulphur concentrations or even more with the sulphur calcium molar ratio were found only in the Jizerské Mountains, not in the Novohradské. Generally, the obtained results support the hypothesis that mechanisms differed between natural and anthropogenic acidification.",
    url = "https://doi.org/10.1007/s11676-019-01061-1",
    doi = "10.1007/s11676-019-01061-1",
    openalex = "W2983061144",
    references = "huang2014research"
}

@article{doi101016jatmosenv201812026,
    author = "Pierret, Marie-Claire and Viville, Daniel and Dambrine, Étienne and Cotel, Solenn and Probst, Anne",
    title = "Twenty-five year record of chemicals in open field precipitation and throughfall from a medium-altitude forest catchment (Strengbach - NE France): An obvious response to atmospheric pollution trends",
    year = "2019",
    journal = "Atmospheric Environment",
    url = "https://doi.org/10.1016/j.atmosenv.2018.12.026",
    doi = "10.1016/j.atmosenv.2018.12.026",
    openalex = "W2907588700",
    references = "doi101016jatmosenv200907031"
}

@article{doi101038s4156101903524,
    author = "Yu, Guirui and Jia, Yanlong and He, Nianpeng and Zhu, Jianxing and Chen, Zhi and Wang, Qiufeng and Piao, Shilong and Liu, Xuejun and He, Honglin and Guo, Xuebing and Wen, Zhang and Pan, Li and Ding, Guoan and Goulding, K. W. T.",
    title = "Stabilization of atmospheric nitrogen deposition in China over the past decade",
    year = "2019",
    journal = "Nature Geoscience",
    url = "https://doi.org/10.1038/s41561-019-0352-4",
    doi = "10.1038/s41561-019-0352-4",
    openalex = "W2937260348"
}

Atmospheric nitrogen (N) deposition has increased substantially across China since 1980; however, data for N deposition fluxes since the 2000s has been very limited. Understanding and mitigating the impacts of N deposition requires long-term quantification of dry as well as wet deposition of key reactive nitrogen (Nr) species. Here we present a dataset for inorganic N concentrations and deposition for the period 2010-2015 in China, compiled from the nationwide deposition monitoring network. The dataset comprises information from 32 monitoring sites on concentrations and bulk deposition (wet plus part of dry deposition) fluxes of NH 4 + -N and NO 3 - -N, air concentrations and dry deposition fluxes of the major Nr species NH 3, NO 2, HNO 3, and particulate NH 4 + and NO 3 -. This unique database is available inter alia to advance understanding of the spatial patterns of inorganic N concentrations and deposition in China and its associated effects, constrain primary Nr (e.g., NH 3, NO x) emission inventories, and validate outputs of atmospheric chemistry and transport models.

@article{doi101038s4159701900612,
    author = "Xu, Wen and Zhang, Lin and Liu, Xuejun",
    title = "A database of atmospheric nitrogen concentration and deposition from the nationwide monitoring network in China",
    year = "2019",
    journal = "Scientific Data",
    abstract = "Atmospheric nitrogen (N) deposition has increased substantially across China since 1980; however, data for N deposition fluxes since the 2000s has been very limited. Understanding and mitigating the impacts of N deposition requires long-term quantification of dry as well as wet deposition of key reactive nitrogen (Nr) species. Here we present a dataset for inorganic N concentrations and deposition for the period 2010-2015 in China, compiled from the nationwide deposition monitoring network. The dataset comprises information from 32 monitoring sites on concentrations and bulk deposition (wet plus part of dry deposition) fluxes of NH 4 + -N and NO 3 - -N, air concentrations and dry deposition fluxes of the major Nr species NH 3, NO 2, HNO 3, and particulate NH 4 + and NO 3 -. This unique database is available inter alia to advance understanding of the spatial patterns of inorganic N concentrations and deposition in China and its associated effects, constrain primary Nr (e.g., NH 3, NO x) emission inventories, and validate outputs of atmospheric chemistry and transport models.",
    url = "https://doi.org/10.1038/s41597-019-0061-2",
    doi = "10.1038/s41597-019-0061-2",
    openalex = "W2944642697",
    references = "zhu2016the"
}

China has been experiencing fine particle (i.e., aerodynamic diameters ≤ 2.5 µm; PM 2.5) pollution and acid rain in recent decades, which exert adverse impacts on human health and the ecosystem. Recently, ammonia (i.e., NH 3) emission reduction has been proposed as a strategic option to mitigate haze pollution. However, atmospheric NH 3 is also closely bound to nitrogen deposition and acid rain, and comprehensive impacts of NH 3 emission control are still poorly understood in China. In this study, by integrating a chemical transport model with a high-resolution NH 3 emission inventory, we find that NH 3 emission abatement can mitigate PM 2.5 pollution and nitrogen deposition but would worsen acid rain in China. Quantitatively, a 50% reduction in NH 3 emissions achievable by improving agricultural management, along with a targeted emission reduction (15%) for sulfur dioxide and nitrogen oxides, can alleviate PM 2.5 pollution by 11-17% primarily by suppressing ammonium nitrate formation. Meanwhile, nitrogen deposition is estimated to decrease by 34%, with the area exceeding the critical load shrinking from 17% to 9% of China's terrestrial land. Nevertheless, this NH 3 reduction would significantly aggravate precipitation acidification, with a decrease of as much as 1.0 unit in rainfall pH and a corresponding substantial increase in areas with heavy acid rain. An economic evaluation demonstrates that the worsened acid rain would partly offset the total economic benefit from improved air quality and less nitrogen deposition. After considering the costs of abatement options, we propose a region-specific strategy for multipollutant controls that will benefit human and ecosystem health.

@article{doi101073pnas1814880116,
    author = "Liu, Mingxu and Huang, Xin and Song, Yu and Tang, Jie and Cao, Junji and Zhang, Xiaoye and Zhang, Qiang and Wang, Shuxiao and Xu, Tingting and Kang, Ling and Cai, Xuhui and Zhang, Hongsheng and Yang, Fumo and Wang, Huanbo and Yu, Jian Zhen and Lau, Alexis K.H. and He, Ling‐Yan and Huang, Xiaofeng and Duan, Lei and Ding, Aijun and Xue, Likun and Gao, Jian and Liu, Bin and Zhu, Tong",
    title = "Ammonia emission control in China would mitigate haze pollution and nitrogen deposition, but worsen acid rain",
    year = "2019",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "China has been experiencing fine particle (i.e., aerodynamic diameters ≤ 2.5 µm; PM 2.5) pollution and acid rain in recent decades, which exert adverse impacts on human health and the ecosystem. Recently, ammonia (i.e., NH 3) emission reduction has been proposed as a strategic option to mitigate haze pollution. However, atmospheric NH 3 is also closely bound to nitrogen deposition and acid rain, and comprehensive impacts of NH 3 emission control are still poorly understood in China. In this study, by integrating a chemical transport model with a high-resolution NH 3 emission inventory, we find that NH 3 emission abatement can mitigate PM 2.5 pollution and nitrogen deposition but would worsen acid rain in China. Quantitatively, a 50\% reduction in NH 3 emissions achievable by improving agricultural management, along with a targeted emission reduction (15\%) for sulfur dioxide and nitrogen oxides, can alleviate PM 2.5 pollution by 11-17\% primarily by suppressing ammonium nitrate formation. Meanwhile, nitrogen deposition is estimated to decrease by 34\%, with the area exceeding the critical load shrinking from 17\% to 9\% of China's terrestrial land. Nevertheless, this NH 3 reduction would significantly aggravate precipitation acidification, with a decrease of as much as 1.0 unit in rainfall pH and a corresponding substantial increase in areas with heavy acid rain. An economic evaluation demonstrates that the worsened acid rain would partly offset the total economic benefit from improved air quality and less nitrogen deposition. After considering the costs of abatement options, we propose a region-specific strategy for multipollutant controls that will benefit human and ecosystem health.",
    url = "https://doi.org/10.1073/pnas.1814880116",
    doi = "10.1073/pnas.1814880116",
    openalex = "W2935492565",
    references = "doi101016jatmosenv201607018, doi101021es0626133, larssen2000acid"
}

Regional severe haze represents an enormous environmental problem in China, influencing air quality, human health, ecosystem, weather, and climate. These extremes are characterized by exceedingly high concentrations of fine particulate matter (smaller than 2.5 µm, or PM 2.5) and occur with extensive temporal (on a daily, weekly, to monthly timescale) and spatial (over a million square kilometers) coverage. Although significant advances have been made in field measurements, model simulations, and laboratory experiments for fine PM over recent years, the causes for severe haze formation have not yet to be systematically/comprehensively evaluated. This review provides a synthetic synopsis of recent advances in understanding the fundamental mechanisms of severe haze formation in northern China, focusing on emission sources, chemical formation and transformation, and meteorological and climatic conditions. In particular, we highlight the synergetic effects from the interactions between anthropogenic emissions and atmospheric processes. Current challenges and future research directions to improve the understanding of severe haze pollution as well as plausible regulatory implications on a scientific basis are also discussed.

@article{doi101073pnas1900125116,
    author = "An, Zhisheng and Huang, Ru‐Jin and Zhang, Renyi and Tie, Xuexi and Li, Guohui and Cao, Junji and Zhou, Weijian and Shi, Zhengguo and Han, Yongming and Gu, Zhaolin and Ji, Yuemeng",
    title = "Severe haze in northern China: A synergy of anthropogenic emissions and atmospheric processes",
    year = "2019",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Regional severe haze represents an enormous environmental problem in China, influencing air quality, human health, ecosystem, weather, and climate. These extremes are characterized by exceedingly high concentrations of fine particulate matter (smaller than 2.5 µm, or PM 2.5) and occur with extensive temporal (on a daily, weekly, to monthly timescale) and spatial (over a million square kilometers) coverage. Although significant advances have been made in field measurements, model simulations, and laboratory experiments for fine PM over recent years, the causes for severe haze formation have not yet to be systematically/comprehensively evaluated. This review provides a synthetic synopsis of recent advances in understanding the fundamental mechanisms of severe haze formation in northern China, focusing on emission sources, chemical formation and transformation, and meteorological and climatic conditions. In particular, we highlight the synergetic effects from the interactions between anthropogenic emissions and atmospheric processes. Current challenges and future research directions to improve the understanding of severe haze pollution as well as plausible regulatory implications on a scientific basis are also discussed.",
    url = "https://doi.org/10.1073/pnas.1900125116",
    doi = "10.1073/pnas.1900125116",
    openalex = "W2939064738"
}

Abstract With continuous nitrogen (N) enrichment and sulfur (S) deposition, soil acidification has accelerated and become a global environmental issue. However, a full understanding of the general pattern of ecosystem belowground processes in response to soil acidification due to the impacting factors remains elusive. We conducted a meta-analysis of soil acidification impacts on belowground functions using 304 observations from 49 independent studies, mainly including soil cations, soil nutrient, respiration, root and microbial biomass. Our results show that acid addition significantly reduced soil pH by 0.24 on average, with less pH decrease in forest than non-forest ecosystems. The response ratio of soil pH was positively correlated with site precipitation and temperature, but negatively with initial soil pH. Soil base cations (Ca 2+, Mg 2+, Na +) decreased while non-base cations (Al 3+, Fe 3+) increased with soil acidification. Soil respiration, fine root biomass, microbial biomass carbon and nitrogen were significantly reduced by 14.7%, 19.1%, 9.6% and 12.1%, respectively, under acid addition. These indicate that soil carbon processes are sensitive to soil acidification. Overall, our meta-analysis suggests a strong negative impact of soil acidification on belowground functions, with the potential to suppress soil carbon emission. It also arouses our attention to the toxic effects of soil ions on terrestrial ecosystems.

@article{doi10108817489326ab239c,
    author = "Meng, Cheng and Tian, Dashuan and Zeng, Hui and Li, Zhaolei and Yi, Chuixiang and Niu, Shuli",
    title = "Global soil acidification impacts on belowground processes",
    year = "2019",
    journal = "Environmental Research Letters",
    abstract = "Abstract With continuous nitrogen (N) enrichment and sulfur (S) deposition, soil acidification has accelerated and become a global environmental issue. However, a full understanding of the general pattern of ecosystem belowground processes in response to soil acidification due to the impacting factors remains elusive. We conducted a meta-analysis of soil acidification impacts on belowground functions using 304 observations from 49 independent studies, mainly including soil cations, soil nutrient, respiration, root and microbial biomass. Our results show that acid addition significantly reduced soil pH by 0.24 on average, with less pH decrease in forest than non-forest ecosystems. The response ratio of soil pH was positively correlated with site precipitation and temperature, but negatively with initial soil pH. Soil base cations (Ca 2+, Mg 2+, Na +) decreased while non-base cations (Al 3+, Fe 3+) increased with soil acidification. Soil respiration, fine root biomass, microbial biomass carbon and nitrogen were significantly reduced by 14.7\%, 19.1\%, 9.6\% and 12.1\%, respectively, under acid addition. These indicate that soil carbon processes are sensitive to soil acidification. Overall, our meta-analysis suggests a strong negative impact of soil acidification on belowground functions, with the potential to suppress soil carbon emission. It also arouses our attention to the toxic effects of soil ions on terrestrial ecosystems.",
    url = "https://doi.org/10.1088/1748-9326/ab239c",
    doi = "10.1088/1748-9326/ab239c",
    openalex = "W2947213882",
    references = "doi101016jatmosenv201607018, doi101016s0269749103000198"
}

Increasing nitrogen (N) deposition in subtropical forests in south China causes N saturation, associated with significant nitrate (NO 3 -) leaching. Strong N attenuation may occur in groundwater discharge zones hydrologically connected to well-drained hillslopes, as has been shown for the subtropical headwater catchment "TieShanPing", where dual NO 3 - isotopes indicated that groundwater discharge zones act as an important N sink and hotspot for denitrification. Here, we present a regional study reporting inorganic N fluxes over two years together with dual NO 3 - isotope signatures obtained in two summer campaigns from seven forested catchments in China, representing a gradient in climate and atmospheric N input. In all catchments, fluxes of dissolved inorganic N indicated efficient conversion of NH 4 + to NO 3 - on well-drained hillslopes, and subsequent interflow of NO 3 - over the argic B-horizons to groundwater discharge zones. Depletion of 15 N- and 18 O-NO 3 - on hillslopes suggested nitrification as the main source of NO 3 -. In all catchments, except one of the northern sites, which had low N deposition rates, NO 3 - attenuation by denitrification occurred in groundwater discharge zones, as indicated by simultaneous 15 N and 18 O enrichment in residual NO 3 -. By contrast to the southern sites, the northern catchments lack continuous and well-developed groundwater discharge zones, explaining less efficient N removal. Using a model based on 15 NO 3 - signatures, we estimated denitrification fluxes from 2.4 to 21.7 kg N ha -1 year -1 for the southern sites, accounting for more than half of the observed N removal. Across the southern catchments, estimated denitrification scaled proportionally with N deposition. Together, this indicates that N removal by denitrification is an important component of the N budget of southern Chinese forests and that natural NO 3 - attenuation may increase with increasing N input, thus partly counteracting further aggravation of N contamination of surface waters in the region.

@article{doi101111gcb14596,
    author = "Yu, Longfei and Mulder, Jan and Zhu, Jing and Zhang, Xiaoshan and Wang, Zhangwei and Dörsch, Peter",
    title = "Denitrification as a major regional nitrogen sink in subtropical forest catchments: Evidence from multi‐site dual nitrate isotopes",
    year = "2019",
    journal = "Global Change Biology",
    abstract = {Increasing nitrogen (N) deposition in subtropical forests in south China causes N saturation, associated with significant nitrate (NO 3 -) leaching. Strong N attenuation may occur in groundwater discharge zones hydrologically connected to well-drained hillslopes, as has been shown for the subtropical headwater catchment "TieShanPing", where dual NO 3 - isotopes indicated that groundwater discharge zones act as an important N sink and hotspot for denitrification. Here, we present a regional study reporting inorganic N fluxes over two years together with dual NO 3 - isotope signatures obtained in two summer campaigns from seven forested catchments in China, representing a gradient in climate and atmospheric N input. In all catchments, fluxes of dissolved inorganic N indicated efficient conversion of NH 4 + to NO 3 - on well-drained hillslopes, and subsequent interflow of NO 3 - over the argic B-horizons to groundwater discharge zones. Depletion of 15 N- and 18 O-NO 3 - on hillslopes suggested nitrification as the main source of NO 3 -. In all catchments, except one of the northern sites, which had low N deposition rates, NO 3 - attenuation by denitrification occurred in groundwater discharge zones, as indicated by simultaneous 15 N and 18 O enrichment in residual NO 3 -. By contrast to the southern sites, the northern catchments lack continuous and well-developed groundwater discharge zones, explaining less efficient N removal. Using a model based on 15 NO 3 - signatures, we estimated denitrification fluxes from 2.4 to 21.7 kg N ha -1 year -1 for the southern sites, accounting for more than half of the observed N removal. Across the southern catchments, estimated denitrification scaled proportionally with N deposition. Together, this indicates that N removal by denitrification is an important component of the N budget of southern Chinese forests and that natural NO 3 - attenuation may increase with increasing N input, thus partly counteracting further aggravation of N contamination of surface waters in the region.},
    url = "https://doi.org/10.1111/gcb.14596",
    doi = "10.1111/gcb.14596",
    openalex = "W2916345503",
    references = "doi101111gcb13333"
}

The chemical composition of precipitation was assessed in 27 European countries from 2000 to 2017, offering a general point of view on the rainwater chemistry in Europe, contributing to a larger understanding of air pollution and atmospheric chemistry. The volume-weighted mean concentrations (VWM) were calculated, showing the relative dominance of SO 4 2− and Cl−, explaining the acidic and slightly acidic pH values that ranged from 4.19 to 5.82 over Europe. The VWM concentrations of ionic species measured in rainwater usually followed the SO 4 2 > Cl− > Na+ > NH4+ > NO3− > H+ > Ca2+ > Mg2+ > K+ > HCO3− downward order, with small exceptions, depending on the industrial activity or legal framework of a particular area. Fractional acidity showed that ~ 69% of the inorganic acidity in precipitation is neutralised, whilst neutralisation factors showed that Na+ and NH4+ contributed the most to the neutralising process. The relationship between acidic and neutralising compounds was further examined by calculating the ionic ratios. Wet deposition rates showed the dominance of acidic compounds over neutralising ones, reflecting the climatic influences and the local and regional economic characteristics of different regions from Europe. Origins of major ions in rainwater were examined using the sea salt and non-sea salt fractions, crustal and marine enrichment factors, correlation analysis and the Principal Component Analysis, showing the significant influence of anthropogenic sources (industry, agriculture, traffic). Natural sources (maritime, terrestrial) also play a major role in influencing the precipitation chemistry of the European continent. The main conclusion of this study regarding the precipitation chemistry of the European continent during the studied period is represented by the relative homogenous distribution of the analysed chemical species, which is most likely due to the unitary economic development and to the implementation of common European policies in the field of environmental protection. Since the pH is still acidic due to the anthropogenic emissions, more attention should be given to the implementation of environmental legislation, especially in non-European Union countries or in countries that joined recently.

@article{doi101186s1230201902349,
    author = "Keresztesi, Ágnes and Birsan, Marius‐Victor and Niță, Ion-Andrei and Bodor, Zsolt and Szép, Róbert",
    title = "Assessing the neutralisation, wet deposition and source contributions of the precipitation chemistry over Europe during 2000–2017",
    year = "2019",
    journal = "Environmental Sciences Europe",
    abstract = "The chemical composition of precipitation was assessed in 27 European countries from 2000 to 2017, offering a general point of view on the rainwater chemistry in Europe, contributing to a larger understanding of air pollution and atmospheric chemistry. The volume-weighted mean concentrations (VWM) were calculated, showing the relative dominance of SO 4 2− and Cl−, explaining the acidic and slightly acidic pH values that ranged from 4.19 to 5.82 over Europe. The VWM concentrations of ionic species measured in rainwater usually followed the SO 4 2 > Cl− > Na+ > NH4+ > NO3− > H+ > Ca2+ > Mg2+ > K+ > HCO3− downward order, with small exceptions, depending on the industrial activity or legal framework of a particular area. Fractional acidity showed that \textasciitilde\ 69\% of the inorganic acidity in precipitation is neutralised, whilst neutralisation factors showed that Na+ and NH4+ contributed the most to the neutralising process. The relationship between acidic and neutralising compounds was further examined by calculating the ionic ratios. Wet deposition rates showed the dominance of acidic compounds over neutralising ones, reflecting the climatic influences and the local and regional economic characteristics of different regions from Europe. Origins of major ions in rainwater were examined using the sea salt and non-sea salt fractions, crustal and marine enrichment factors, correlation analysis and the Principal Component Analysis, showing the significant influence of anthropogenic sources (industry, agriculture, traffic). Natural sources (maritime, terrestrial) also play a major role in influencing the precipitation chemistry of the European continent. The main conclusion of this study regarding the precipitation chemistry of the European continent during the studied period is represented by the relative homogenous distribution of the analysed chemical species, which is most likely due to the unitary economic development and to the implementation of common European policies in the field of environmental protection. Since the pH is still acidic due to the anthropogenic emissions, more attention should be given to the implementation of environmental legislation, especially in non-European Union countries or in countries that joined recently.",
    url = "https://doi.org/10.1186/s12302-019-0234-9",
    doi = "10.1186/s12302-019-0234-9",
    openalex = "W2964856653",
    references = "doi101016s0045653503000286"
}

@article{doi101007s10533020006738,
    author = "Langenhove, Leandro Van and Verryckt, Lore T. and Bréchet, Laëtitia and Courtois, Élodie A. and Stahl, Clément and Hofhansl, Florian and Bauters, Marijn and Sardans, Jordi and Boeckx, Pascal and Fransén, Erik and Peñuelas, Josep and Janssens, Ivan A.",
    title = "Atmospheric deposition of elements and its relevance for nutrient budgets of tropical forests",
    year = "2020",
    journal = "Biogeochemistry",
    url = "https://doi.org/10.1007/s10533-020-00673-8",
    doi = "10.1007/s10533-020-00673-8",
    openalex = "W3025715193",
    references = "doi10100797894009092368"
}

China has experienced a dramatic change in atmospheric reactive nitrogen (Nr) emissions over the past four decades. However, it remains unclear how nitrogen (N) deposition has responded to increases and/or decreases in Nr emissions. This study quantitatively assesses temporal and spatial variations in measurements of bulk and calculated dry N deposition in China from 1980 to 2018. A long-term database (1980-2018) shows that bulk N deposition peaked in around 2000, and had declined by 45% by 2016-2018. Recent bulk and dry N deposition (based on monitoring from 2011 to 2018) decreased from 2011 to 2018, with current average values of 19.4 ± 0.8 and 20.6 ± 0.4 kg N ha -1 yr -1, respectively. Oxidized N deposition, especially dry deposition, decreased after 2010 due to NO x emission controls. In contrast, reduced N deposition was approximately constant, with reductions in bulk NH 4 + -N deposition offset by a continuous increase in dry NH 3 deposition. Elevated NH 3 concentrations were found at nationwide monitoring sites even at urban sites, suggesting a strong influence of both agricultural and non-agricultural sources. Current emission controls are reducing Nr emissions and deposition but further mitigation measures are needed, especially of NH 3, built on broader regional emission control strategies.

@article{doi101016jenvint2020106022,
    author = "Wen, Zhang and Xu, Wen and Li, Qi and Han, Mengjuan and Tang, Aohan and Zhang, Ying and Luo, Xiaosheng and Shen, Jianlin and Wang, Wei and Li, Kaihui and Pan, Yuepeng and Zhang, Lin and Li, Wenqing and Collett, Jeffery L. and Zhong, Buqing and Wang, Xuemei and Goulding, K. W. T. and Zhang, Fusuo and Liu, Xuejun",
    title = "Changes of nitrogen deposition in China from 1980 to 2018",
    year = "2020",
    journal = "Environment International",
    abstract = "China has experienced a dramatic change in atmospheric reactive nitrogen (Nr) emissions over the past four decades. However, it remains unclear how nitrogen (N) deposition has responded to increases and/or decreases in Nr emissions. This study quantitatively assesses temporal and spatial variations in measurements of bulk and calculated dry N deposition in China from 1980 to 2018. A long-term database (1980-2018) shows that bulk N deposition peaked in around 2000, and had declined by 45\% by 2016-2018. Recent bulk and dry N deposition (based on monitoring from 2011 to 2018) decreased from 2011 to 2018, with current average values of 19.4 ± 0.8 and 20.6 ± 0.4 kg N ha -1 yr -1, respectively. Oxidized N deposition, especially dry deposition, decreased after 2010 due to NO x emission controls. In contrast, reduced N deposition was approximately constant, with reductions in bulk NH 4 + -N deposition offset by a continuous increase in dry NH 3 deposition. Elevated NH 3 concentrations were found at nationwide monitoring sites even at urban sites, suggesting a strong influence of both agricultural and non-agricultural sources. Current emission controls are reducing Nr emissions and deposition but further mitigation measures are needed, especially of NH 3, built on broader regional emission control strategies.",
    url = "https://doi.org/10.1016/j.envint.2020.106022",
    doi = "10.1016/j.envint.2020.106022",
    openalex = "W3090692320",
    references = "doi101007s1053300403700, doi101016jatmosenv201310060, doi101016jscitotenv201306108, doi101038nature11917, doi101038nature13774, doi101038s4156101903524, doi101038s4159702004622, doi101073pnas1900125116, doi101126science1136674, doi105194acp18140952018, doi105194acp744192007"
}

Atmospheric reactive nitrogen (N r) has been a cause of serious environmental pollution in China. Historically, China used too little N r in its agriculture to feed its population. However, with the rapid increase in N fertilizer use for food production and fossil fuel consumption for energy supply over the last four decades, increasing gaseous N r species (e.g. NH 3 and NO x) have been emitted to the atmosphere and then deposited as wet and dry deposition, with adverse impacts on air, water and soil quality as well as plant biodiversity and human health. This paper reviews the issues associated with this in a holistic way. The emissions, deposition, impacts, actions and regulations for the mitigation of atmospheric N r are discussed systematically. Both NH 3 and NO x make major contributions to environmental pollution but especially to the formation of secondary fine particulate matter (PM 2.5), which impacts human health and light scattering (haze). In addition, atmospheric deposition of NH 3 and NO x causes adverse impacts on terrestrial and aquatic ecosystems due to acidification and eutrophication. Regulations and practices introduced by China that meet the urgent need to reduce N r emissions are explained and resulting effects on emissions are discussed. Recommendations for improving future N management for achieving 'win-win' outcomes for Chinese agricultural production and food supply, and human and environmental health, are described. This article is part of a discussion meeting issue 'Air quality, past present and future'.

@article{doi101098rsta20190324,
    author = "Liu, Xuejun and Xu, Wen and Du, Enzai and Tang, Aohan and Zhang, Y. and Zhang, Y. Y. and Wen, Z. and Hao, Tianxiang and Pan, Yuepeng and Zhang, Lin and Gu, Baojing and Zhao, Yu and Shen, Jianlin and Zhou, Feng and Gao, Ziwen and Feng, ZhiYuan and Chang, Yunhua and Goulding, K. W. T. and Collett, Jeffrey L. and Vitousek, Peter M. and Zhang, Fusuo",
    title = "Environmental impacts of nitrogen emissions in China and the role of policies in emission reduction",
    year = "2020",
    journal = "Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering Sciences",
    abstract = "Atmospheric reactive nitrogen (N r) has been a cause of serious environmental pollution in China. Historically, China used too little N r in its agriculture to feed its population. However, with the rapid increase in N fertilizer use for food production and fossil fuel consumption for energy supply over the last four decades, increasing gaseous N r species (e.g. NH 3 and NO x) have been emitted to the atmosphere and then deposited as wet and dry deposition, with adverse impacts on air, water and soil quality as well as plant biodiversity and human health. This paper reviews the issues associated with this in a holistic way. The emissions, deposition, impacts, actions and regulations for the mitigation of atmospheric N r are discussed systematically. Both NH 3 and NO x make major contributions to environmental pollution but especially to the formation of secondary fine particulate matter (PM 2.5), which impacts human health and light scattering (haze). In addition, atmospheric deposition of NH 3 and NO x causes adverse impacts on terrestrial and aquatic ecosystems due to acidification and eutrophication. Regulations and practices introduced by China that meet the urgent need to reduce N r emissions are explained and resulting effects on emissions are discussed. Recommendations for improving future N management for achieving 'win-win' outcomes for Chinese agricultural production and food supply, and human and environmental health, are described. This article is part of a discussion meeting issue 'Air quality, past present and future'.",
    url = "https://doi.org/10.1098/rsta.2019.0324",
    doi = "10.1098/rsta.2019.0324",
    openalex = "W3088126573",
    references = "doi101016jenvint2020106022, zhu2016the"
}

@article{doi101016jatmosres2021105566,
    author = "Geng, Jianwei and Li, Hengpeng and Chen, Dongqiang and Nei, Xiaofei and Diao, Yaqin and Zhang, Wangshou and Pang, Jiaping",
    title = "Atmospheric nitrogen deposition and its environmental implications at a headwater catchment of Taihu Lake Basin, China",
    year = "2021",
    journal = "Atmospheric Research",
    url = "https://doi.org/10.1016/j.atmosres.2021.105566",
    doi = "10.1016/j.atmosres.2021.105566",
    openalex = "W3134419322",
    references = "huang2014research"
}

Atmospheric nitrogen (N) deposition is a vital component of the global N cycle. Excessive N deposition on the Earth's surface has adverse impacts on ecosystems and humans. Quantification of atmospheric N deposition is indispensable for assessing and addressing N deposition-induced environmental issues. In the present review, we firstly summarized the current methods applied to quantify N deposition (wet, dry, and total N deposition), their advantages and major limitations. Secondly, we illustrated the long-term N deposition monitoring networks worldwide and the results attained via such long-term monitoring. Results show that China faces heavier N deposition than the United States, European countries, and other countries in East Asia. Next, we proposed a framework for estimating the atmospheric wet and dry N deposition using a combined method of surface monitoring, modeling, and satellite remote sensing. Finally, we put forth the critical research challenges and future directions of the atmospheric N deposition. CAPSULE: A review of quantification methods and the global data on nitrogen deposition and a systematic framework was proposed for quantifying nitrogen deposition.

@article{doi101016jecoenv2021112180,
    author = "Zhang, Qi and Li, Yanan and Wang, Mengru and Wang, Kai and Meng, Fanlei and Liu, Lei and Zhao, Yuanhong and Ma, Lin and Zhu, Qichao and Xu, Wen and Zhang, Fusuo",
    title = "Atmospheric nitrogen deposition: A review of quantification methods and its spatial pattern derived from the global monitoring networks",
    year = "2021",
    journal = "Ecotoxicology and Environmental Safety",
    abstract = "Atmospheric nitrogen (N) deposition is a vital component of the global N cycle. Excessive N deposition on the Earth's surface has adverse impacts on ecosystems and humans. Quantification of atmospheric N deposition is indispensable for assessing and addressing N deposition-induced environmental issues. In the present review, we firstly summarized the current methods applied to quantify N deposition (wet, dry, and total N deposition), their advantages and major limitations. Secondly, we illustrated the long-term N deposition monitoring networks worldwide and the results attained via such long-term monitoring. Results show that China faces heavier N deposition than the United States, European countries, and other countries in East Asia. Next, we proposed a framework for estimating the atmospheric wet and dry N deposition using a combined method of surface monitoring, modeling, and satellite remote sensing. Finally, we put forth the critical research challenges and future directions of the atmospheric N deposition. CAPSULE: A review of quantification methods and the global data on nitrogen deposition and a systematic framework was proposed for quantifying nitrogen deposition.",
    url = "https://doi.org/10.1016/j.ecoenv.2021.112180",
    doi = "10.1016/j.ecoenv.2021.112180",
    openalex = "W3154060361",
    references = "doi101016jenvint2020106022"
}

Deadwood represents an important carbon stock and contributes to climate change mitigation. Wood decomposition is mainly driven by fungal communities. Their composition is known to change during decomposition, but it is unclear how environmental factors such as wood chemistry affect these successional patterns through their effects on dominant fungal taxa. We analysed the deadwood of Fagus sylvatica and Abies alba across a deadwood succession series of >40 years in a natural fir-beech forest in the Czech Republic to describe the successional changes in fungal communities, fungal abundance and enzymatic activities and to link these changes to environmental variables. The fungal communities showed high levels of spatial variability and beta diversity. In young deadwood, fungal communities showed higher similarity among tree species, and fungi were generally less abundant, less diverse and less active than in older deadwood. pH and the carbon to nitrogen ratio (C/N) were the best predictors of the fungal community composition, and they affected the abundance of half of the dominant fungal taxa. The relative abundance of most of the dominant taxa tended to increase with increasing pH or C/N, possibly indicating that acidification and atmospheric N deposition may shift the community composition towards species that are currently less dominant.

@article{doi103390jof7060412,
    author = "Lepinay, Clémentine and Jiráska, Lucie and Tláskal, Vojtěch and Brabcová, Vendula and Vrška, Tomáš and Baldrián, Petr",
    title = "Successional Development of Fungal Communities Associated with Decomposing Deadwood in a Natural Mixed Temperate Forest",
    year = "2021",
    journal = "Journal of Fungi",
    abstract = "Deadwood represents an important carbon stock and contributes to climate change mitigation. Wood decomposition is mainly driven by fungal communities. Their composition is known to change during decomposition, but it is unclear how environmental factors such as wood chemistry affect these successional patterns through their effects on dominant fungal taxa. We analysed the deadwood of Fagus sylvatica and Abies alba across a deadwood succession series of >40 years in a natural fir-beech forest in the Czech Republic to describe the successional changes in fungal communities, fungal abundance and enzymatic activities and to link these changes to environmental variables. The fungal communities showed high levels of spatial variability and beta diversity. In young deadwood, fungal communities showed higher similarity among tree species, and fungi were generally less abundant, less diverse and less active than in older deadwood. pH and the carbon to nitrogen ratio (C/N) were the best predictors of the fungal community composition, and they affected the abundance of half of the dominant fungal taxa. The relative abundance of most of the dominant taxa tended to increase with increasing pH or C/N, possibly indicating that acidification and atmospheric N deposition may shift the community composition towards species that are currently less dominant.",
    url = "https://doi.org/10.3390/jof7060412",
    doi = "10.3390/jof7060412",
    openalex = "W3165316616",
    references = "huang2014research"
}

Air pollution has been a long-term problem, especially in urban areas, that eventually accelerates the formation of acid rain (AR), but recently it has emerged as a serious environmental issue worldwide owing to industrial and economic growth, and it is also considered a major abiotic stress to agriculture. Evidence showed that AR exerts harmful effects in plants, especially on growth, photosynthetic activities, antioxidant activities and molecular changes. Effectiveness of several bio-regulators has been tested so far to arbitrate various physiological, biochemical and molecular processes in plants under different diverse sorts of environmental stresses. In the current review, we showed that silicon (tetravalent metalloid and semi-conductor), glutathione (free thiol tripeptide) and melatonin (an indoleamine low molecular weight molecule) act as influential growth regulators, bio-stimulators and antioxidants, which improve plant growth potential, photosynthesis spontaneity, redox-balance and the antioxidant defense system through quenching of reactive oxygen species (ROS) directly and/or indirectly under AR stress conditions. However, earlier research findings, together with current progresses, would facilitate the future research advancements as well as the adoption of new approaches in attenuating the consequence of AR stress on crops, and might have prospective repercussions in escalating crop farming where AR is a restraining factor.

@article{doi103390molecules26040862,
    author = "Debnath, Biswojit and Sikdar, Ashim and Islam, Md. Shahidul and Hasan, Md. Kamrul and Li, Min and Qiu, Dongliang",
    title = "Physiological and Molecular Responses to Acid Rain Stress in Plants and the Impact of Melatonin, Glutathione and Silicon in the Amendment of Plant Acid Rain Stress",
    year = "2021",
    journal = "Molecules",
    abstract = "Air pollution has been a long-term problem, especially in urban areas, that eventually accelerates the formation of acid rain (AR), but recently it has emerged as a serious environmental issue worldwide owing to industrial and economic growth, and it is also considered a major abiotic stress to agriculture. Evidence showed that AR exerts harmful effects in plants, especially on growth, photosynthetic activities, antioxidant activities and molecular changes. Effectiveness of several bio-regulators has been tested so far to arbitrate various physiological, biochemical and molecular processes in plants under different diverse sorts of environmental stresses. In the current review, we showed that silicon (tetravalent metalloid and semi-conductor), glutathione (free thiol tripeptide) and melatonin (an indoleamine low molecular weight molecule) act as influential growth regulators, bio-stimulators and antioxidants, which improve plant growth potential, photosynthesis spontaneity, redox-balance and the antioxidant defense system through quenching of reactive oxygen species (ROS) directly and/or indirectly under AR stress conditions. However, earlier research findings, together with current progresses, would facilitate the future research advancements as well as the adoption of new approaches in attenuating the consequence of AR stress on crops, and might have prospective repercussions in escalating crop farming where AR is a restraining factor.",
    url = "https://doi.org/10.3390/molecules26040862",
    doi = "10.3390/molecules26040862",
    openalex = "W3128172906",
    references = "doi101039c0em00116c"
}

Acid deposition in China has been declining since the 2000s. While this may help mitigate acidification in forest soils and water, little is known about the recovery of soils and water from previous severe acidification in tropical China. Here, we assessed the chemistry of mineral soils, water, and acid gases (SO 2 and NO x) from three successional forest types in tropical China from 2000 to 2022. Our results showed that soil pH increased synchronously from 3.9 (2000-2015) to 4.2 (2016-2022) across all three forest types, with exchangeable acid initially decreasing and thereafter stabilizing. Surface and ground water pH also gradually increased throughout the monitoring period. Soil pH recovery was stronger in the primary than in the planted forest. However, soil pH recovery lagged behind the increase in rainfall pH by approximately a decade. The recovery of soil pH was likely related to the positive effects of the dissolution of Al/Fe-hydroxysulfate mineral and subsequent sulfur desorption on soil acid-neutralizing capacity, increased soil organic matter, and climate warming, but was likely moderated by increased exchangeable aluminum and potentially proton-producing hydroxysulfate mineral dissolution that caused the lagged soil pH recovery. Surface and ground water pH recovery was attributed to increased water acid-neutralizing capacity. Our study reports the potential for the recovery of acidified soil and water following decreased acid deposition and provides new insights into the functional recovery of acid-sensitive forests.

@article{doi101021acsest3c01416,
    author = "Lie, Zhiyang and Huang, Wenjuan and Zhou, Guoyi and Zhang, Deqiang and Yan, Junhua and Jiang, Jun and Neilson, Roy and Zhou, Shu‐Yi‐Dan and Zhang, Wanjun and Aguila, Luis Carlos Ramos and Chu, Guowei and Liu, Shizhong and Meng, Ze and Zhang, Qianmei and Liu, Juxiu",
    title = "Acidity of Soil and Water Decreases in Acid-Sensitive Forests of Tropical China",
    year = "2023",
    journal = "Environmental Science \& Technology",
    abstract = "Acid deposition in China has been declining since the 2000s. While this may help mitigate acidification in forest soils and water, little is known about the recovery of soils and water from previous severe acidification in tropical China. Here, we assessed the chemistry of mineral soils, water, and acid gases (SO 2 and NO x) from three successional forest types in tropical China from 2000 to 2022. Our results showed that soil pH increased synchronously from 3.9 (2000-2015) to 4.2 (2016-2022) across all three forest types, with exchangeable acid initially decreasing and thereafter stabilizing. Surface and ground water pH also gradually increased throughout the monitoring period. Soil pH recovery was stronger in the primary than in the planted forest. However, soil pH recovery lagged behind the increase in rainfall pH by approximately a decade. The recovery of soil pH was likely related to the positive effects of the dissolution of Al/Fe-hydroxysulfate mineral and subsequent sulfur desorption on soil acid-neutralizing capacity, increased soil organic matter, and climate warming, but was likely moderated by increased exchangeable aluminum and potentially proton-producing hydroxysulfate mineral dissolution that caused the lagged soil pH recovery. Surface and ground water pH recovery was attributed to increased water acid-neutralizing capacity. Our study reports the potential for the recovery of acidified soil and water following decreased acid deposition and provides new insights into the functional recovery of acid-sensitive forests.",
    url = "https://doi.org/10.1021/acs.est.3c01416",
    doi = "10.1021/acs.est.3c01416",
    openalex = "W4384924292",
    references = "doi101007bf02369968, doi1010160016703782901685, doi101016jenvpol200412023, doi101016jscitotenv201306108, doi101023a1021398008726, doi101038s4156101903524, doi101073pnas1814880116, doi10108817489326102024019, doi1010970001069419850400000019, doi101126science2725259244, doi101139a05015"
}

Soil pH is critically important in regulating soil nutrients and thus influencing the biodiversity and ecosystem functions of terrestrial ecosystems. Despite the ongoing threat of nitrogen (N) pollution especially in the fast-developing regions, it remains unclear how increasing N deposition affects soil pH across global terrestrial ecosystems. By conducting a global meta-analysis with paired observations of soil pH under N addition and control from 634 studies spanning major types of terrestrial ecosystems, we show that soil acidification increases rapidly with N addition amount and is most severe in neutral-pH soils. Grassland soil pH decreases most strongly under high N addition while wetlands are the least acidified. By extrapolating these relationships to global mapping, we reveal that atmospheric N deposition leads to a global average soil pH decline of -0.16 in the past 40 years and regions encompassing Eastern United States, Southern Brazil, Europe, and South and East Asia are the hotspots of soil acidification under N deposition. Our results highlight that anthropogenically amplified atmospheric N deposition has profoundly altered global soil pH and chemistry. They suggest that atmospheric N deposition is a major threat to global terrestrial biodiversity and ecosystem functions.

@article{doi101111gcb16813,
    author = "Chen, Chen and Xiao, Wenya and Chen, Han Y. H.",
    title = "Mapping global soil acidification under N deposition",
    year = "2023",
    journal = "Global Change Biology",
    abstract = "Soil pH is critically important in regulating soil nutrients and thus influencing the biodiversity and ecosystem functions of terrestrial ecosystems. Despite the ongoing threat of nitrogen (N) pollution especially in the fast-developing regions, it remains unclear how increasing N deposition affects soil pH across global terrestrial ecosystems. By conducting a global meta-analysis with paired observations of soil pH under N addition and control from 634 studies spanning major types of terrestrial ecosystems, we show that soil acidification increases rapidly with N addition amount and is most severe in neutral-pH soils. Grassland soil pH decreases most strongly under high N addition while wetlands are the least acidified. By extrapolating these relationships to global mapping, we reveal that atmospheric N deposition leads to a global average soil pH decline of -0.16 in the past 40 years and regions encompassing Eastern United States, Southern Brazil, Europe, and South and East Asia are the hotspots of soil acidification under N deposition. Our results highlight that anthropogenically amplified atmospheric N deposition has profoundly altered global soil pH and chemistry. They suggest that atmospheric N deposition is a major threat to global terrestrial biodiversity and ecosystem functions.",
    url = "https://doi.org/10.1111/gcb.16813",
    doi = "10.1111/gcb.16813",
    openalex = "W4380077697",
    references = "doi101016jgeoderma2019114107"
}

@article{doi101007s11104024069645,
    author = "Qiu, Sihui and Xia, Shiting and Liu, Fengcai and Yu, Mengxiao and Chang, Zhongbing and Wang, Ying‐Ping and Yan, Junhua and Jiang, Jun",
    title = "Acid deposition promotes soil carbon sequestration in terrestrial ecosystems of China",
    year = "2024",
    journal = "Plant and Soil",
    url = "https://doi.org/10.1007/s11104-024-06964-5",
    doi = "10.1007/s11104-024-06964-5",
    openalex = "W4402899617",
    references = "doi101021acsest3c01416"
}

Global forest soil acidification has become a significant environmental concern, making it essential to gain a comprehensive understanding of research hotspots in this field. Acidic substances in forest soil originate from both external and internal factors. To investigate this issue, we conducted a visual analysis of 2325 papers published between 2004 and 2024 using the Web of Science Database, along with the visualization and analysis tools CiteSpace and VOSviewer. Over the past 20 years, the number of publications on global forest soil acidification has steadily increased. China and the United States have far more publications than any other country. Key research hotspots include soil acidification, atmospheric deposition, nitrogen deposition, heavy metals, soil pH, plant growth, impacts and governance, each displaying distinct characteristics at different stages. This review offers a comprehensive overview of recent advances in global forest soil acidification research and serves as a valuable reference for both research and practical applications. It examines the current state of this global environmental problem, the long-term effects of acidification and forest succession, and the eco-environmental effects associated with soil acidification. It also proposes sustainable solutions to mitigate forest soil acidification and outlines potential future research topics. These efforts aim to support the stable development of forest ecosystems and promote ongoing research in this critical area.

@article{doi103390f16050733,
    author = "Zhang, Yujie and Zhou, Jiangmin and Chen, Hualin",
    title = "Global Trajectories of Forest Soil Acidification: A Scientometric Synthesis of Drivers, Impacts and Sustainable Solutions",
    year = "2025",
    journal = "Forests",
    abstract = "Global forest soil acidification has become a significant environmental concern, making it essential to gain a comprehensive understanding of research hotspots in this field. Acidic substances in forest soil originate from both external and internal factors. To investigate this issue, we conducted a visual analysis of 2325 papers published between 2004 and 2024 using the Web of Science Database, along with the visualization and analysis tools CiteSpace and VOSviewer. Over the past 20 years, the number of publications on global forest soil acidification has steadily increased. China and the United States have far more publications than any other country. Key research hotspots include soil acidification, atmospheric deposition, nitrogen deposition, heavy metals, soil pH, plant growth, impacts and governance, each displaying distinct characteristics at different stages. This review offers a comprehensive overview of recent advances in global forest soil acidification research and serves as a valuable reference for both research and practical applications. It examines the current state of this global environmental problem, the long-term effects of acidification and forest succession, and the eco-environmental effects associated with soil acidification. It also proposes sustainable solutions to mitigate forest soil acidification and outlines potential future research topics. These efforts aim to support the stable development of forest ecosystems and promote ongoing research in this critical area.",
    url = "https://doi.org/10.3390/f16050733",
    doi = "10.3390/f16050733",
    openalex = "W4409813382",
    references = "doi101021acsest3c01416"
}