银川地区潜水环境背景值研究

An Analysis of Background Value of Phreatic Water in Yinchuan Area

尽可能获取人类活动影响之前或影响相对较小时期的化学组分含量可作为一个地区的环境背景值。在综合分析银川地区水文地质条件基础上,将研究区划分为4个水环境单元,应用数理统计方法,对1987-1989年潜水水质资料进行分析,以平均值、标准差、变异系数和含量范围等给出各单元潜水10个项目的环境背景值,分析了潜水环境背景值的空间分布规律及区域变异特征。结果表明:潜水环境背景值在河湖积平原区最高,河漫滩和冲洪积平原区次之,山前洪积倾斜平原区最低。潜水环境背景值的空间变化特征反映了地下水流的水文地球化学作用从溶滤→溶滤、浓缩平衡→浓缩的分带特征,服从自山前补给区向河岸排泄区水化学组分由亏缺转向富集的演化规律,在东部河漫滩地带黄河补给冲淡作用明显。

To some degree,the contents of the chemical components of a region before or during a relatively low-impact period can be used as the environmental background value for a region.In this paper,four environmental zones of phreatic water are divided in Yinchuan Area on the basis of comprehensive analysis of the hydrogeological condition.The phreatic water quality results in 1987-1989 are analyzed by mathematical statistics method,and the background values of 10 components in each zones are given by using concentration value,standard deviation,coefficient of variation and range of content.The spatial distribution law and regional variability of phreatic background value are analyzed.The results show that the phreatic background value is the highest in the fluvial-lacustrine plain area,the second in floodplains and alluvial-diluvial plains,and the lowest in the diluvial inclined plains.The spatial variation characteristics of the background values of the phreatic reflect the zonal characteristics of the hydrologic geochemistry of groundwater flow,from the main role of dissolution to the balance of filter and concentration,and then to the concentration of the main role.Following the evolution law of hydrochemical components from deficit to enrichment in the discharge area from the piedmont recharge area,and river dilution is obvious in the eastern floodplains.