Du E.; De vries W.; Liu X.; Fang J.; Galloway J.n.; Jiang Y.

 

[Du, E.; Jiang, Y.] Beijing Normal Univ, State Key Lab Earth Surface Proc & Resource Ecol, Beijing 100875, Peoples R China.

[Du, E.; Jiang, Y.] Beijing Normal Univ, Coll Resources Sci & Technol, Beijing 100875, Peoples R China.

[de Vries, W.] Wageningen Univ, Environm Syst Anal Grp, NL-6700 AA Wageningen, Netherlands.

[de Vries, W.] Wageningen Univ & Res Ctr, alterra, NL-6700 AA Wageningen, Netherlands.

[Liu, X.] China Agr Univ, Coll Resources & Environm Sci, Beijing 100193, Peoples R China.

[Fang, J.] Peking Univ, Dept Ecol, Beijing 100871, Peoples R China.

[Fang, J.] Peking Univ, Key Lab Earth Surface Proc, Minist Educ, Beijing 100871, Peoples R China.

[Galloway, J. N.] Univ Virginia, Dept Environm Sci, Charlottesville, VA 22904 USA.

 

ABSTRACT: Elevated emissions of sulfur dioxide, nitrogen oxides and ammonia in China have resulted in high levels of sulfur and nitrogen deposition, being contributors to soil acidification, especially in and near large cities. However, knowledge gaps still exist in the way that large cities shape spatial patterns of acid deposition. Here, we assessed the patterns of pH, sulfate, nitrate and ammonium in bulk precipitation and throughfall in southern China's forests by synthesizing data from published literature. Concentrations and fluxes of sulfate, nitrate and ammonium in bulk precipitation and throughfall exhibited a power-law increase with a closer distance to the nearest large cities, and accordingly pH showed a logarithmic decline. Our findings indicate the occurrence of urban 'acid islands' with a critical radius of approximately 70 km in southern China, receiving potential acid loads of more than 2 keq ha(-1) yr(-1). These urban acid islands covered an area of 0.70 million km(2), accounting for nearly 30% of the land area in southern China. Despite a significant capacity to neutralize acids in precipitation, our analysis highlights a substantial contribution of ammonium to potential acid load. Our results suggest a joint control on emissions of multiple acid precursors from urban areas in southern China.

Published in SCIENTIFIC REPORTS. 2015,5, DOI: 10.1038/srep12625