滹沱河冲洪积扇地下水硝酸盐的污染特征及污染源解析

Characteristics and source apportionment of groundwater nitrate contamination in the Hutuo River alluvial-pluvial fan regions

为研究滹沱河冲洪积扇地区地下水硝酸盐污染机制,对滹沱河冲洪积扇地区地下水和地表水进行了采样监测,运用环境健康风险评价模型对研究区硝酸盐进行评价,采用水化学和多元统计方法研究了滹沱河冲洪积扇地区地下水硝酸盐污染问题。结果表明:研究区地表水NO-3污染较轻,NO-3均值为19.54 mg/L,所有水样均未超出我国地表水环境质量标准(45 mg/L);但是,地下水已经受到了NO-3的严重污染,NO-3均值为75.84 mg/L,且有30.43%水样超出我国地下水质量标准(88.6 mg/L)。研究区3个水文地质单元地下水硝酸盐的平均个人年健康风险分别为4.94×10-8、1.99×10-8和2.61×10-9,低于国际辐射防护委员会(ICRP)推荐的最大可接受风险水平(5.0×10-5/a),因此,认为不会对人群构成严重危害。水文地质单元和地下水埋深对硝酸盐污染有显著影响,但是,土地利用类型对硝酸盐浓度的影响不显著。滹沱河冲洪积扇地区地下水硝酸盐的主要污染来源是生活污水和化肥。此外,强烈开采地下水也是该地区NO-3污染的诱因。

Based on investigation of groundwater and surface water of the Hutuo River alluvial-pluvial fan in October, 2015, the pollution mechanism of nitrate in the region were identified by using the water chemical and multivariate statistical technology. The results show that the nitrate contamination is lighter for surface water and the mean concentration of nitrate is 19.54 mg/L, and all the samples are not over the environmental quality standard for surface water in China （GB 3838--2002）. For groundwater, however, the mean concentration of nitrate is 75.84 mg/L and 30.43% of the samples are over the quality standard in China （88.6 mg/L） , indicating that the groundwater has suffered serious nitrate pollution. The personal annual risk caused by nitrate in three hydrogeological units of the Hutuo River alluvial-pluvial fan regions are 4.94×10^-8, 1.99 × 10^-8 and 2.61 × 10^-9, respectively, and are lower than the maximum allowance risk level recommended by ICRP （5.0 × 10^-5/a）. Therefore, it is at an acceptable level and will not cause obvious health hazards. There are significant difference between nitrate concentration resulting fiom the different hydrogeological subregions and groundwater depth. However, there are no significant differences between tile land use and the nitrate concentration. The mainly sources of NO3- pollution is the domestic sewage and cheroical fertilizer in the study area. In addition, the groundwater intensely exploited is a major inducing factor for the NO3- pollution.