Sources and migration of nitrate in groundwater in the Xishan karst aquifer in Beijing
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摘要: 西山岩溶水作为北京市重要的供水水源，在区域水文地质调查过程中发现西山岩溶水补给区一些样品硝酸盐浓度偏高，然而其周围岩溶水中硝酸盐浓度并未见明显变化（浓度均值为18.81 mg/L），具点状硝酸盐源特征。岩溶含水层中硝酸盐分布特征和影响因素具有重要的研究意义。文章利用岩溶水化学和同位素分析结果研究了岩溶水硝酸盐分布和来源，利用IsoSource软件计算各来源的贡献率。结果表明：军庄—永丰屯径流区和军庄—古城—玉泉山泉径流区岩溶水中硝酸盐主要来源于生活废水、土壤有机氮矿化和大气沉降，贡献率值分别为37.1%、36.3%、26.6%；潭柘寺—四季青岩溶水中硝酸盐在潭柘寺补给区有养殖场废水下渗影响，径流区中硝酸盐含量低并发生反硝化降解作用。永定河水源硝酸盐不是岩溶水硝酸盐的主要来源。研究成果对西山岩溶水中硝酸盐的控制具有重要参考价值。Abstract: The Xishan karst groundwater is an important source of water supply in Beijing. During the process of regional hydrogeological survey, it was found that the nitrate concentration of a few groundwater samples in the recharge area of the karst groundwater was high, however, the nitrate concentration in the surrounding karst groundwater did not change significantly (the average concentration was 18.81 mg/L), which was characterized by a point source of nitrate. The distribution characteristics and influence factors of nitrate in the karst aquifers are of great significance. In this paper, the distribution and possible sources of nitrate in the karst groundwater are studied by using the results of karst hydrochemical and isotopic analyses and the contribution rate of each possible source is calculated by using the IsoSource software. The results show that the main source of nitrate in the karst aquifer of the Junzhuang- ongfengtun runoff area and the Junzhuang-Gucheng-Yuquanshan Spring runoff area comes from domestic sewage, soil organic nitrogen mineralization and atmospheric sedimentation, and the contribution rates are 37.1%, 36.3% and 26.6%, respectively. Nitrate in the karst groundwater near Tanzhishi-Sijiqing is affected by infiltration of aquaculture waste water, nitrate content in the runoff area is low, and denitrification degradation occurs. The nitrate of the Yongding River is not the main source in the Xishan karst groundwater. The results are of important reference value for the control of nitrate in the Xishan karst groundwater.
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Key words:
- nitrate origin /
- isotopes /
- karst aquifer /
- Xishan in Beijing
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