Atmospheric transport of urban-derived NH(x): Evidence from nitrogen concentration and delta(15)N in epilithic mosses at Guiyang, SW China |
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Authors: | Liu Xue-Yan Xiao Hua-Yun Liu Cong-Qiang Li You-Yi Xiao Hong-Wei |
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Institution: | a State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China b Graduate University of the Chinese Academy of Sciences, Beijing 100049, China |
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Abstract: | Nitrogen concentration and δ15N in 175 epilithic moss samples were investigated along four directions from urban to rural sites in Guiyang, SW China. The spatial variations of moss N concentration and δ15N revealed that atmospheric N deposition is dominated by NHx-N from two major sources (urban sewage NH3 and agricultural NH3), the deposition of urban-derived NHx followed a point source pattern characterized by an exponential decline with distance from the urban center, while the agricultural-derived NHx was shown to be a non-point source. The relationship between moss N concentration and distance (y = 1.5e−0.13x + 1.26) indicated that the maximum transporting distance of urban-derived NHx averaged 41 km from the urban center, and it could be determined from the relationship between moss δ15N and distance y = 2.54 ln(x) − 12.227] that urban-derived NHx was proportionally lower than agricultural-derived NHx in N deposition at sites beyond 17.2 km from the urban center. Consequently, the variation of urban-derived NHx with distance from the urban center could be modeled as y = 56.272e−0.116x − 0.481 in the Guiyang area. |
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Keywords: | Atmospheric N deposition Nitrogen isotope Moss Ammonium City area NHx NOx |
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