Water Science & Technology Vol 66 No 3 pp 536–542 © IWA Publishing 2012 doi:10.2166/wst.2012.193
Identification of nitrate sources in Taihu Lake and its major inflow rivers in China, using δ15N-NO3− and δ18O-NO3− values
Zi-Xiang Chen, Guang Liu, Wei-Guo Liu, Michael H. W. Lam, Gui-Jian Liu and Xue-Bin Yin
School of Earth and Space Science, University of Science and Technology of China (USTC), Hefei, Anhui 230026, China E-mail: xbyin@ustc.edu.cn
Advanced Laboratory for Environmental Research and Technology, Joint Advanced Research Center, USTC-CityU, Suzhou, Jiangsu 215123, China
State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi'an, Shanxi 710075, China
Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, China
ABSTRACT
In the present study, δ15N and δ18O-NO3− values, as well as concentrations of some major ion tracers were determined in seasonal water samples from Taihu Lake and major watersheds to investigate the temporal and spatial variations of nitrate sources and assess the underlying nitrogen (N) biogeochemistry process. The results lead to the conclusion that the nitrate concentrations in Taihu Lake are lower in summer than that in winter due to the dilution effect of wet deposition. In winter, sewage and manure were the primary nitrate sources in major inflow rivers and North Taihu Lake (NTL), while nitrate sources in East Taihu Lake (ETL) probably derived from soil organic N. In summer, atmospheric deposition and sewage/manure inputs appear to play an important role in controlling the distribution of nitrates in the whole lake. The δ18O-NO3− values suggest that the nitrate produced from microbial nitrification is another major nitrate source during both winter and summer months. The variations in isotopic values in nitrate suggest denitrification enriched the heavier isotopes of nitrate in NTL in winter and in ETL in summer.
Keywords: denitrification; dual isotopes; nitrate source; nitrification; Taihu Lake
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