基于15N同位素技术的岩溶地下河硝酸盐污染变化特征研究--以重庆青木关地下河为例

Variation features of nitrate pollution in karst underground river based on ^(15)N isotope techniques: A case study in the Qingmuguan underground river,Chongqing

根据2010年5月至2010年10月每月对青木关地下河河水的监测数据,利用15 N同位素技术并结合水化学指标,分析地下河的水化学特征以及硝态氮来源的时空变化特征。结果表明,地下河出口丁家龙洞硝态氮浓度(5.077mg/L)比入口天池硝态氮浓度(0.842mg/L)高6倍多。入口天池处地下河河水硝态氮浓度比较低,δ15 N浓度变化范围为-7.0475‰～+7.059‰,变化幅度不大,说明该点的氮污染较低,地下水受外界影响较小,污水和粪便不是主要的δ15 N来源。出口丁家龙洞处的δ15 N浓度变化范围在-21.453‰～+37.825‰,总体浓度高且变化幅度大,受上游养猪场粪便直接排入及降水影响较大。

Groundwater in the Qingmuguan underground river is monitored with hydrochemistry and ~N iso- tope techniques to investigate temporal and spatial variations of nitrate-nitrogen and its possible sources from May, 2010 to October, 2010. The results show that nitrate concentrations are 5. 077 mg/L at the Dingjia- longdong outlet and 0. 842 mg/L at the Tianchi inlet of the underground river. Nitrate concentrations of the groundwater are low at the Tianchi inlet, and the change range of the a^SN concentration is low, from --7. 0475 %0 to ＋7. 059 %0, which proves that the Tianchi inlet only polluted by nitrogen slightly and the outside influence to groundwater also slight, and the sewage and feces are not the major source of alSN in this point. The concentration of alSN at the Dingjialongdong outlet ranges, overall high and changes much more exten- sively, from --21. 453 X0 to ＋37. 825 %0. That proves the Dingjialongdong is affected more strongly by di- rect emission of feces from the pig farm and precipitation.