华北平原某集约化种植区地下水污染探讨

Pollution of Groundwater in an Intensive Cropping Area, North China

以华北平原某集约化种植区为典型研究区域,通过对采集的8个地下水样品及11个土壤样品分析,探讨集约化种植区地下水的污染程度,解析其污染影响机制。结果表明:该集约化种植地区土壤中残留物主要为有机氯农药,多环芳烃及邻苯二甲酸酯类有机化合物。地下水中硝酸盐含量显著增加;重金属中以Cr含量最高,但均未超标;地下水并未受到有机氯农药的污染,但仍显示有多氯联苯的输入;半挥发性有机物检出种类较多,其中残留农膜释放的邻苯二甲酸酯类有机化合物浓度最高;地下水已受到较为严重的污染。集约化种植区大量施用化肥、农药和覆盖农膜,污染负荷严重,灌溉频繁且量大,污染质运移驱动力大是地下水污染的根本原因;当地包气带中黏性土厚度不均以及井孔止水不严等因素也成为了地下水受到污染的直接原因。

Eight groundwater samples and eleven soil samples were collected in an intensive cropping area, North China, to analyze the pollution extent of groundwater and identify the pollution mechanism from the source to the object. The results demonstrate that the organic residues in soil are mainly composed of organo-chlorine pesticide, polycyclic aromatic hydrocarbons and phthalates acid esters. The nitrate concentration in groundwater has been growing rapidly, and Cr is the highest one among heavy metals, none of which, however, exceeds the threshold quality for groundwater standard. Groundwater is free from organo-chlorine pesticide contamination, but it still suffers from some input of polychlorinated biphenyls. Several semi-volatilized organic compounds were detected in groundwater samples, among which the phthalates acid esters released from plastic membrane has the maximum quantity. As indicated above, groundwater has been heavily polluted. The fundamental causes for groundwater contamination are massive fertilizer, pesticides and plastic membrane used in the intensive cropping area causing serious pollution load and the high frequency of irrigation serving as compelling force of pollutant acceleration. The heterogeneous thickness of clay in the vadose zone and incompletely sealed wells are also factors with which intensive cropping activities influence groundwater quality.