Unsurprisingly, the amount of reactive nitrogen circulating annually on land has been doubled because of increasing anthropogenic activities. Exceedingly large amounts of reactive nitrogen (N-r) are likely to disrupt N dynamics and negatively impact the environment and human health. Guizhou Province, a major energy-producing province in southwest China, is suffering from serious long-term acid deposition. However, little work has been done to quantify the levels of atmospheric N deposition in this province, in which some ecologically vulnerable areas have resulted from rocky desertification. In this study, tissue N contents and delta N-15 signatures in 109 epilithic mosses were analyzed by the ordinary kriging (OK) interpolation technique to determine atmospheric N deposition. Moss N content (136-2.65%) showed a significant decrease from west to east, indicating that the spatial variance of TN deposition was the same as that of moss N content, with an average of 27.74 kg N ha(-1) yr(-1). Moss delta N-15 ranged from -5.89 parts per thousand to -0.72 parts per thousand and showed an opposite spatial variance compared with moss N contents. Negative delta N-15 indicated that the main sources for N deposition were urban sewage and agricultural NH3. According to Moss delta N-15 values, it could be concluded that NH4+-N and NO3--N were the main components of wet deposition, accounting for 52% and 44% of TN, respectively. The deposition fluxes were 14.49 kg N ha(-1) yr(-1) and 12.16 kg N ha(-1) yr(-1), respectively. Although the emission flux of NO3--N far exceeded that of NH4+-N, the amount of NH4+-N deposited on land was larger than that of NO3--N. N deposition in 99.6% of the province exceeded the critical load for terrestrial ecosystems. High N deposition is the main environmental problem facing Guizhou Province, and recommendations regarding regulatory strategies for mitigating atmospheric N pollution are urgently needed. (C) 2016 Elsevier Ltd. All rights reserved.

Publication name	ATMOSPHERIC ENVIRONMENT, 142 145-151; 10.1016/j.atmosenv.2016.07.044 OCT 2016
Author(s)	Qu, Linglu; Xiao, Huayun; Guan, Hui; Zhang, Zhongyi; Xu, Yu
Corresponding author	XIAO Huayun   xiaohuayun@vip.skleg.cn  Chinese Acad Sci, Inst Geochem, State Key Lab Environm Geochem, Guiyang 550081, Peoples R China.

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