为优化地下水水质监测方案，确定北京顺平岩溶水系统岩溶水水质的主要控制指标，快速掌握地下水水质变化，基于2022年顺平岩溶水系统49件岩溶水样品，综合运用统计分析、Piper三线图和熵权水质指数(entropy weight water quality index，EWQI)分析研究区水化学和水质特征，并耦合逐步多元线性回归分析，探讨能代表研究区岩溶水水质的关键指标。结果显示:①顺平岩溶水系统岩溶水具有微碱性、低盐度的特征，水化学类型主要为HCO3-—Ca2+·Mg2+型(73。47％)。超标指标为Nan(NH3或NH4+中的N，即氨氮以氮计)、pH值、Fe、Mn和F-，超标率分别为10。20％、4。08％、4。08％、4。08％和2。04％。②研究区EWQI平均值为26。33，水质"极好"，其中极好和良好所占比例分别为91。84％和8。16％。③基于地下水水质数据构建的EWQImin模型筛选的关键指标为Nan、Fe、Mn、Nntr(硝氮以氮计，硝酸盐中N)和F-，其决定系数(R2)和百分比误差(PE)分别为0。986和3。88％。表明，EWQImin模型优选指标可以代表顺平岩溶水系统的水质状况，对优化水质监测网等水资源管理提供了参考价值。
Quality evaluation and index optimization of karst water based on EWQI method——A case study of Shunping karst water system in Beijing
Objectives:The construction of groundwater monitoring network often has the problems of large investment and high maintenance cost.How to use limited funds to set up a comprehensive,scientific and reasonable monitoring network,select key characteristic indicators to maximize the information of groundwater environment and improve the efficiency of water quality evaluation has become a hot topic in this field.In this paper,Shunping karst groundwater system is taken as the study area.Through the selection of evaluation methods and the optimization of the number of monitoring indicators,the main control factors of water quality in the study area are identified,and the groundwater-monitoring network is optimized.Methods:Based on 49 karst groundwater samples in Shunping karst water system in 2022,the water chemistry and water quality characteristics of the study area were analyzed by statistical analysis,Piper diagram and entropy weight water quality index(EWQI),and the key indicators that can represent the karst groundwater quality in the study area were discussed by coupling stepwise multiple linear regression analysis.Results:① The karst groundwater of Shunping karst water system has the characteristics of slightly alkaline and low salinity.The hydrochemical type is mainly HCO3-—Ca2+.Mg2+type(73.47％).The over-standard indicators were Nan(Nitrogen in NH3 or NH4+),pH,Fe,Mn and F-,and the over-standard rates were 10.20％,4.08％,4.08％,4.08％and 2.04％,respectively.② The average EWQI in the study area was 26.33,and the water quality was"excellent",of which the proportions of excellent and good were 91.84％and 8.16％,respectively.③ The EWQImin model constructed based on groundwater quality data can well represent the actual EWQI,and the key indicators include Nan,Fe,Mn,Nntr(Nitrogen in NO3-)and F-,and the determination coefficient(R2)and percentage error(PE)values are 0.986 and 3.88％,respectively.Conclusions:The optimization method of groundwater monitoring index based on EWQI and stepwise multiple linear regression can be used as an important reference for optimization index and provide technical methods for regional groundwater environment management.
Shunping karst water systementropy weight water quality index(EWQI)stepwise multiple linear regressionkey indicatorsoptimization method
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