城市地下水硝酸盐污染及其成因分析

NITRATE POLLUTION OF GROUNDWATER IN URBAN AREA

用N同位素分析方法并结合调查区域土地利用类型的分析 ,对杭州市城区 2 1口水井取样分析以确定杭州城市地下水的水质结果显示 :本地区地下水硝酸盐污染严重 ,杭州城市地下水水质属于Ⅲ类水标准 ,不宜饮用。有 4 0 5 %样品的NO3 N含量超过了世界卫生组织的标准 (N10mgL-1)。我们发现不同的土地利用区有不同的NO3 N水平 (N 0 0 4～ 34 4 1mgL-1)。同时我们引进N同位素方法以辨明NO3 N污染源 :居住区地下水δ15NNO3值为 10 4‰～ 2 2 0‰ ,农业区δ15NNO3值的为 17 5‰～ 19 5‰。生活污水是城市浅层地下水的主要NO3 N污染源。在居住区还存在点源污染 ,如化粪池 ;种植蔬菜施用的有机肥则是农业区的NO3 N污染源。

By the nitrogen isotope method and investigation of the land use in the study area, twenty one wells were sampled to identify the groundwater quality in urban area, Hangzhou City. The result showed that nitrate pollution of the groundwater was serious. The groundwater fell into the water category of Grade Ⅲ in terms of quality and was not potable. There was a high frequency of the samples (40.5% of the total) with nitrate above WHO's standards of N 10 mg L -1 for NO 3 N. Areas different in land use areas were also different in nitrate concentrations (ranging between N 0.04～34.41 mg L -1 ) and δ 15 N NO 3 values (between 7.8‰～35.5‰) of the groundwater. At the same time the nitrogen isotope method to investigate nitrate sources: in residential areas δ 15 N NO 3 was 10.4‰～22.0‰,and in agricultural area 17.5‰～19.5‰. Domestic sewage was the major nitrate source to the shallow groundwater in the urban area, septic tank still existing in the residential, settings the point sources of nitrate, and manure application in the agricultural areas,the non point sources of NO 3 N sources pollution.