渭河流域地下水氮污染的来源示踪及其迁移转化过程识别  

Identification of nitrogen pollution sources and the fate of nitrogen in groundwater in the Weihe River Basin

作　　者：杨楠[1] 张妍 孙豪 王超[2] YANG Nan;ZHANG Yan;SUN Hao;WANG Chao(College of Urban and Environmental Science,Northwest University,Xi'an 710127;State Key Laboratory of Eco-hydraulics in Northwest Arid Region,Xi'an University of Technology,Xi'an 710048)

机构地区：[1]西北大学城市与环境学院,西安710127 [2]西安理工大学,西北旱区生态水利国家重点实验室,西安710048

出　　处：《环境科学学报》2025年第1期272-282,共11页Acta Scientiae Circumstantiae

基　　金：国家自然科学基金面上项目(No.42273056)。

摘　　要：地下水氮污染与人类健康息息相关,对氮污染来源的划分是有效控制地下水污染的关键.本研究采集了渭河流域地下水样品,结合水化学方法和环境稳定同位素技术,对冬夏两季地下水中氮污染的时空分布特征、迁移转化过程及来源进行了研究,并结合SIAR同位素混合模型定量分析了不同来源氮对地下水硝酸盐氮的贡献率.结果表明,硝酸盐氮是渭河流域地下水氮污染的主要形式.夏季和冬季硝酸盐氮与氨氮浓度无显著性差异(p>0.05),而亚硝酸盐氮浓度在冬季显著大于夏季(p<0.01).硝酸盐氮浓度在空间上无显著性差异,亚硝酸盐氮浓度下游大于上、中游(p<0.01),氨氮浓度表现为中游大于上游和下游(p<0.01).冬季宝鸡市、兴平市与夏季宝鸡市、眉县、兴平市附近采样点硝酸盐氮浓度超过生活饮用水卫生标准(GB 5749-2022)规定的10 mg·L^(-1),两季超标率分别为20%和30%,超标样品δ^(15)N范围为+1.33%~+14.36%.地下水硝酸盐氮的主要来源是粪便及污废水、化肥以及土壤有机氮,以上来源对冬季地下水硝酸盐氮的贡献率分别为42.73%、22.99%和21.84%,对夏季的贡献率分别为40.34%、36.97%和18.02%,大气沉降在两季对地下水氮污染的贡献最小.冬季氮转化的主要过程是硝化作用与异化硝酸盐还原作用(DNRA),而夏季的主导过程为硝化作用,异化硝酸盐还原作用相对较弱.提高生活污废水收集效率,改善化粪池管理,推广有机肥料的施用,提高肥料与土壤中氮利用效率是减少渭河流域地下水硝酸盐氮的重要举措.Nitrogen pollution in groundwater has significant implications for human health,therefore identifying the nitrogen pollution sources is crucial for effective groundwater pollution control.This study collected Groundwater samples from the Weihe River Basin during the summer and winter seasons.Hydrochemical methods and environmental stable isotope techniques were applied to investigate the spatio-temporal distribution characteristics,migration and transformation processes,and sources of nitrogen pollution in groundwater.The SIAR isotope mixing model was utilized to quantitaty the contribution rates of different sources to groundwater nitrogen.Results showed that nitrate is the primary form of nitrogen pollution in groundwater.There were no significant differences in the concentration of nitrate nitrogen(NO_(3)^(-)-N)and ammonium nitrogen(NH_(4)^(+)-N)between summer and winter(p>0.05).However,nitrite nitrogen(NO_(2)^(-)-N)concentrations were significantly higher in winter than in summer(p<0.01).Spatially,There were no significant differences in NO_(3)^(-)-N concentrations.NO_(2)^(-)-N concentrations were higher downstream compared to upstream and midstream(p<0.01),while ammonium nitrogen concentrations were higher midstream than upstream and downstream(p<0.01).The nitrate nitrogen concentrations of groundwater samples collected from Baoji City and Xingping City in winter and from Baoji City,Meixian County,and Xingping City in summer exceeded the drinking water standard limit of 10 mg·L^(-1)(GB 5749-2022),with exceeding rates of 20%and 30%,respectively.Theδ^(15)N values of the samples ranged from+1.33%to+14.36%.The main sources of groundwater nitrate were identified as manure and sewage(42.73%in winter,40.34%in summer),fertilizers(22.99%in winter,36.97%in summer),and soil organic nitrogen(21.84%in winter,18.02%in summer).The contribution of atmospheric deposition to groundwater nitrogen pollution was found to be minimal both in summer and winter.The nitrification and dissimilatory nitrate reduction to ammonium(DNRA

关 键 词：地下水 氮污染 氮氧双同位素 迁移转化 季节性变化 

分 类 号：X523[环境科学与工程—环境工程]