渭河流域关中段地下水硝态氮来源解析

为定性及定量识别地下水中氮的污染来源及迁移转化特征，本文在水化学分析的基础上结合氮氧稳定同位素技术及SIAR模型对渭河流域关中段地下水补给来源、地下水中氮污染特征进行了判断.结果表明，渭河流域关中段地下水的主要水化学类型为HCO₃-Ca+Mg型，地下水由降水快速入渗补给和地表水入渗补给.地下水氮污染以硝态氮形式为主，在所采集的34个地下水水样中，硝态氮含量的变化范围为0.154~36.717mg/L，平均含量为6.17mg/L，其中硝态氮含量超过Ⅲ类地下水标准的采样点共有2个，超标率为5.9%.氮循环的主导作用为硝化作用.地下水δ¹⁵N-NO₃^-含量的变化范围为+6.08‰~+16.42‰，δ¹⁵O-NO₃^-含量的变化范围为+9.38‰~+12.514‰，硝态氮污染主要受到人类活动的影响，土壤有机氮、粪便及污废水和大气沉降是地下水硝态氮的主要贡献者，平均贡献率分别为44.65%、40.03%和15.32%.

The source identification of nitrate in groundwater in Guanzhong section of Weihe river basin

In order to identify the source of nitrogen pollution in groundwater and the characteristics of its migration and transformation qualitatively and quantitatively, the nitrogen and oxygen stable isotope technology and the SIAR model on the basis of hydrochemical analysis were combined in this paper to judge the source of groundwater recharge and the characteristics of groundwater nitrogen pollution in Guanzhong section of Weihe River Basin. The results showed that the main hydrochemical type of groundwater in the Guanzhong section of the Weihe River Basin was HCO₃-Ca+Mg, and the groundwater was mainly recharged by rapid infiltration of precipitation and infiltration of surface water. Groundwater nitrogen pollution was mainly in the form of nitrate nitrogen. In all 34 groundwater samples collected, the variation range of nitrate nitrogen content was 0.154~36.717 mg/L, with an average content of 6.17 mg/L. The nitrate nitrogen content in two sampling points exceeded the Grade III groundwater standard, and the exceeding rate was 5.9%. The dominant role of nitrogen cycle was nitrification. The variation range of δ¹⁵N-NO₃^- content in groundwater was +6.08‰~+16.42‰ while δ¹⁵O-NO₃^- was +9.38‰~+12.514‰. Nitrate nitrogen pollution was mainly affected by human activities, soil organic nitrogen, manure and sewage and atmospheric deposition were the main contributors to groundwater nitrate nitrogen, with an average contribution rate of 44.65%, 40.03% and 15.32%, respectively.