汉江下游河流渗滤系统原生劣质地下水分布特征及影响因素研究

Distribution characteristics and influencing factors of poor-quality native groundwater in river percolation system in the lower reaches of the Hanjiang River

江汉平原原生劣质地下水问题日趋严重,地下水中砷、亚铁、锰、铵态氮含量严重超标,对居民生产生活和饮用水安全造成了不利影响,但相关研究仍较为薄弱。以汉江下游典型河流渗滤系统为研究对象,对研究区内距离汉江5 km及主要支流2 km范围内的地下水样品的水化学成分及原生劣质组分进行测试分析,旨在查明江汉下游河流渗滤系统原生劣质地下水的分布特征,并探讨其主要影响因素。结果显示:平面上,地下水原生劣质组分呈高度空间异质性,相邻的采样点浓度可能相差很大,极大值点多出现在河流拐弯处;垂向上,地下水中As、Fe^(2+)、Mn、NH_(4-)N高值多出现在20 m左右的深度;强烈的还原环境、中性pH值和富含有机质是该层地下水富集原生劣质组分的主要原因;河流渗滤通过改变地下水的氧化还原条件、酸碱条件和有机质含量影响河流渗滤系统原生劣质地下水的分布。

The problem of inferior-quality groundwater in the Jianghan plain is becoming more and more serious.The contents of arsenic,ferrous iron,manganese and ammonium nitrogen(so-called“inferior components”)in the native groundwater are well above the safety standards for drinking water,which has an negative impact on the residents’lives,yet the related research is still relatively weak.In this study,aiming to find out the distribution characteristics of poor-quality native groundwater in the Hanjiang river filtration system,we took a typical area in the downstream of the Hanjiang river filtration system as the research object.We analyzed the chemical composition and the“inferior components”in water samples collected 5 km from the Hanjiang River and 2 km within the range of the main river branch,and discussed the main factors influencing the quality of native groundwater.The results show that on the plane,the“inferior components”of native groundwater were highly heterogeneous spatially,with their concentration varied greatly in adjacent sampling points and the maximum value points mostly found at the river bends.In the vertical direction,the high As,Fe^(2+),Mn and NH_(4-)N values in groundwater occurred mostly at a depth of about 20 m.Strong reducing environment,neutral pH and rich organic matter are the main reasons that the“inferior components”are concentrated in groundwater.River leachate affect the distribution of inferior-quality native groundwater by changing the redox condition,environmental alkalinity and organic matter content in groundwater.