塔城盆地地下水“三氮”污染特征及成因

Distribution and source of nitrogen pollution in groundwater in the Tacheng Basin

地下水氮元素污染是一个全球性的环境问题,其来源和迁移转化特征是国内外研究的热点。文章以新疆塔城盆地80组地下水样品水化学组分测试结果为依据,研究塔城盆地地下水"三氮"污染特征。结果表明:塔城盆地地下水质量总体较好;对比2017年发布的地下水质量标准,深层承压水"三氮"均未超标;浅层地下水"三氮"污染较轻,"三氮"超标点零星分布于地下水的中下游冲洪积平原区,其中,NO3-N超标率最高,超标率为8.8%; NO2-N和NH4-N次之,超标率均为1.3%。沿着地下水流向,从山区到盆地中央的平原区,地下水污染逐渐变重。"三氮"重污染点主要分布在塔城市、额敏县及其周边地区。区内地下水污染点的分布与工矿企业污染源、污水处理厂、垃圾填埋场等大型污染源的分布具有一定的相关性。城市化进程中,生活污水的不合理排放是塔城盆地"三氮"污染的主要来源,而通过排污河流下渗是研究区地下水"三氮"污染的重要途径;氧化还原条件、p H值、包气带岩性结构、补径排条件等是"三氮"迁移转化及其空间分布的主要影响因素。

Eighty shallow groundwater samples were collected from the Tacheng Basin and analyzed for chemical compositions to investigate the nitrogen pollution in groundwater in the basin.The results indicate that the shallow groundwater in the Tacheng Basin is significantly polluted by nitrate.8.8% of the groundwater samples have concentrations of NO3-N exceeding the drinking water standard,and the rate is1.3% for NO2-N and NH4-N.The points with nitrogen exceeding the standard mainly occur in the alluvial plain of the middle and lower reaches along the groundwater flow direction.Heavy nitrogen pollution sites mainly exist near the cities of Tacheng and Yin and their surrounding areas.The occurrence of nitrogenpolluted points are adjacent to the sewage treatment plants,landfill sites and other major pollution sources.In the process of urbanization,the irrational discharge of domestic sewage is the main source of nitrogen pollution in the Tacheng basin,and the infiltration of sewage is an important way to cause nitrogen pollution in the groundwater in the study area.Redox conditions,pH,rock types of the aerated zone and conditions of fillingand discharging are the main factors affecting the transport and transformation of nitrogen pollution in the groundwater.