北京市集约化农区地下水硝酸盐含量变化分析

Nitrate Contamination of Groundwater Under Intensive Agricultural Regions of Beijing

为分析和评价北京市地下水硝酸盐污染状况,以北京市集约化农区13个郊区县为研究对象,采集2005—2012年地下水样本,分析测定其NO-3-N含量。结果表明,地下水NO-3-N平均含量为6.34mg·L-1,年际均值在5.85～6.93mg·L-1之间,符合国家地下水质量标准(GB/T14848-93)的Ⅲ类水质标准,超标率(>10mg·L-1)和严重超标率(>20mg·L-1)分别为19.36%和6.73%。地下水NO-3-N含量雨季后略高于雨季前;不同作物种植区地下水NO-3-N平均含量顺序为蔬菜种植区>粮食作物区>其他作物区>果树种植区,均值分别为7.66、6.15、5.58mg·L-1和4.97mg·L-1;NO-3-N含量随地下水埋深增加呈明显下降趋势。

Groundwater samples were collected from intensive agricultural regions of 13 districts in Beijing from 2005 to 2012 to determine the status of nitrate nitrogen（N） contamination in groundwater. The results indicated that the mean concentration of nitrate-N of all samples analysed in Beijing was 6.34 mg NO-3-N·L-1. There were 19.36% of the samples exceeding 10 mg·L^-1, and 6.73% of the samples exceeding 20 mg·L^-1. The annual average concentration of nitrate-N varied from 5.85 mg·L^-1 to 6.93 mg·L^-1, which met the category III national water quality standard. Nitrate leaching was enhanced by rainfall and higher concentrations of nitrate-N in groundwater were observed after rainy seasons. The nitrate-N concentration in groundwater was affected by the land use system in the following order：vegetable field〉arable cropping〉other land uses〉orchards, with the mean nitrate-N concentration being 7.66 mg·L^-1, 6.15 mg·L^-1, 5.58 mg·L^-1 and 4.97 mg·L^-1, respectively. The nitrate-N concentration in groundwater decreased with increasing groundwater depth, and the average concentration within 30 m was 12.71 mg·L^-1, exceeding the WHO drinking water guideline.