滹沱河冲洪积扇地下水硝酸盐含量的空间分布特征及影响因素

为了解华北平原地下水中硝酸盐的分布状况及影响因素,对石家庄市滹沱河冲洪积扇四个地下水单元的地下水样品进行采集与分析。结果表明:在115个样品中,64.35%的样品水质符合《地下水质量标准》(GB 14848—1993)Ⅴ类标准,地下水质量总体较差,主要的污染指标为硝酸盐和总硬度,超标点位主要分布在西北部两个地下水单元。硝酸盐的浓度范围为0.24~440 mg·L~(-1),其平均浓度与最高浓度分别为GB/T 14848—1993中硝酸盐Ⅲ类标准值的3倍与22倍,属于严重污染;不同地下水单元中硝酸盐浓度差异较大,在研究区内基本呈现从西北到东南、从浅层到深层逐渐降低趋势。除水文地质条件对地下水中硝酸盐含量有重要影响外,污染源类型及其分布也起到了重要作用。通过相关性分析,初步认为研究区西北部两个地下水单元中硝酸盐污染主要来源于点源类型的生活污水及畜禽养殖废水,东南部的两个地下水单元的硝酸盐污染主要来源于面源类型的农业施肥。

Spatial distribution and influencing factors of nitrate content in groundwater of alluvial-pluvial fan of Hutuo River

In order to identify the contamination profiles and spatial distribution of nitrate in the North China Plain, 115 groundwater sam-ples,collected from Hutuo River pluvial fan in Shijiazhuang City, Hebei Province, were analyzed according to the parameters listed in the Quality Standard for Ground Water(GB 14848—1993). Results indicated that the water quality was generally poor. The 64.35% of total samples only met the Class V standards. Nitrate and hardness were the main failed indicators. The sampling sites with poor water quality were mainly located in the two groundwater units in the northwest area. The nitrate concentrations ranged from 0.24 to 440 mg·L-1, with the maximum and the average concentrations being 22 and 3 times higher than the ClassⅢstandard value, respectively. The nitrate concentra-tions spatially decreased from the north-west to the south-east and from shallow to deep stratum of the research area. Hydrogeological con-ditions had an important effect on the distribution of nitrate in groundwater. In addition, the type and distribution of pollution sources also had great contributions. Correlation analysis between chloridion and nitrate, and between total hardness and nitrate indicated that nitrate in the two units of the north-west area came from the discharges of domestic wastewater and livestock and poultry breeding wastewater from the point sources, while nitrate in the other two units located in the south-east area was mainly resulted from the agricultural non-point sources.