青海省北川河流域地下水水化学特征与水质评价

目的]分析北川河流域地下水化学特征，从地下水的资源属性角度出发客观评价流域地下水水质状况，为区域地下水环境保护提供数据支撑。方法]利用2019年北川河流域水文地质水资源调查所获取的189组地下水化学数据分析流域地下水化学成分的分布特征和来源。依据地下水富水性分级对单个样品点的水质类型赋予不同的系数，构建基于地下水富水性分级的区域水质评价方法。结果]北川河流域地下水化学分布具有较大的空间变化。上游丘陵山区和河谷平原区广泛分布HCO₃~-型淡水，向下游逐渐出现SO₄^2-,Cl~-类型的微咸水、咸水以及指示人类活动影响的HCO₃·Cl-Na型淡水；碳酸盐岩和硅酸盐岩风化溶解对地下水水化学组分来源具有控制作用，局部区域因蒸发浓缩而富集；Al,Fe,Th等天然背景元素是造成流域地下水水质超标的主要指标，Pb,CCl₄、NO₃~-等典型污染组分在工业区和人口集中区地下水中超标更加明显，在人为污染及天然高背景双因素驱动下河谷区地下水质更加复杂；基于采样点数量统计的...

Chemical Characteristics and Quality Evaluation of Groundwater in Beichuan River Basin in Qinghai Province

Objective] The chemical characteristics of groundwater in Beichuan River basin were analysed, and groundwater quality was evaluated objectively from the perspective of resource attributes of groundwater in order to provide data support for regional groundwater environmental protection. Methods] 189 sets of groundwater chemical data acquired by hydrogeological surveys in 2019 were selected to analyze the distribution characteristics and sources of groundwater chemical composition in Beichuan River basin. An evaluation method for regional groundwater quality was constructed by assigning different coefficients for water quality type to a single sampling point. Results] The groundwater chemical distribution of Beichuan River basin exhibited a large spatial variability. HCO₃-type freshwater was widely disturbed in the upstream sections of the hilly mountainous area and the valley plain area , and SO₄^2-, Cl-type brackish and salt water, as well as HCO₃·Cl-Na type freshwater gradually appeared downstream, indicating human activities. Weathered dissolution of carbonate rock and silicate rock controlled the source of groundwater chemical components, but local areas were enriched due to evaporation concentration. Natural background elements such as Al, Fe, and Th were the main influencing indicators that had exceeded the underground water quality standard in the study area, but typical contamination components such as Pb, NO₃^-, and carbon tetrachloride were more obvious in the industrial zone and the population-concentrated area. Under the driving influences of human pollution and naturally high background conditions, the underground water quality in the river valley plain was more complicated. The over-standard ratios of the hilly mountainous region and the valley plain region based on the quantity of sampling points were 57.0% and 27.1% respectively, but these values were reduced to 29.4% and 12.6% according to the new evaluation method proposed in this study. Conclusion] The impact of human pollution on the chemical components of groundwater was mainly concentrated in middle and lower reaches of the valley plain zone, and chemical components of groundwater in most other regions were controlled by natural background conditions. Through the newly proposed regional groundwater quality evaluation method, groundwater quality evaluation results and groundwater resources were combined, and the proportion of abundant high quality groundwater area was highlighted in the whole area. Finally, the problem of excessive over-standard rate in the regional groundwater quality evaluation results was effectively resolved.