Liu Cong-Qiang, Li Si-Liang, Lang Yun-Chao, Xiao Hua-Yun
The State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
Environ Sci Technol. 2006 Nov 15;40(22):6928-33. doi: 10.1021/es0610129.
Nitrate pollution of the karstic groundwater is an increasingly serious problem with the development of Guiyang, the capital city of Guizhou Province, southwest China. The higher content of NO3- in groundwater compared to surface water during both summer and winter seasons indicates that the karstic groundwater system cannot easily recover once contaminated with nitrate. In order to assess the sources and conversion of nitrate in the groundwater of Guiyang, we analyzed the major ions, delta(15)N-NH4+, delta(15)N-NO3-, and delta(18)O-NO3- in surface and groundwater samples collected during both summer and winter seasons. The results show that nitrate is the major dominant species of nitrogen in most water samples and there is a big variation of nitrate sources in groundwater between winter and summer season, due to fast response of groundwater to rain or surface water in the karst area. Combined with information on NO3- /Cl-, the variations of the isotope values of nitrate in the groundwater show a mixing process of multiple sources of nitrate, especially in the summer season. Chemical fertilizer and nitrification of nitrogen-containing organic materials contribute nitrate to suburban groundwater, while the sewage effluents and denitrification mainly control the nitrate distribution in urban groundwater.
随着中国西南部贵州省省会贵阳市的发展，岩溶地区地下水的硝酸盐污染问题日益严重。夏季和冬季地下水中NO3-的含量均高于地表水，这表明岩溶地下水系统一旦受到硝酸盐污染就很难恢复。为了评估贵阳市地下水中硝酸盐的来源和转化，我们分析了夏季和冬季采集的地表水和地下水样品中的主要离子、δ(15)N-NH4+、δ(15)N-NO3-和δ(18)O-NO3-。结果表明，硝酸盐是大多数水样中主要的氮素形态，由于岩溶地区地下水对降雨或地表水的快速响应，冬季和夏季地下水中硝酸盐来源存在很大差异。结合NO3- /Cl-信息，地下水中硝酸盐同位素值的变化显示出硝酸盐多源混合过程，尤其是在夏季。化肥和含氮有机物质的硝化作用为郊区地下水贡献了硝酸盐，而污水排放和反硝化作用则主要控制了城市地下水中硝酸盐的分布。
