基于级别差法的地下水水质评价方法筛选技术研究

Screening Method for Groundwater Quality Assessment Based on Level Difference Method

地下水水质评价是地下水污染防控和水环境管理的基础.不同评价方法会得到不同的评价结果,因此如何选择合适的评价方法至关重要.目前,缺乏科学、客观的地下水水质评价方法筛选技术.基于此,以洛阳市为例,采用内梅罗指数法、模糊综合评价法和基于免疫进化算法优化的普适法(简称"普适法") 3种方法开展地下水水质评价,通过建立级别差方法,定量筛选最适用评价方法.结果表明:①模糊综合评价法-内梅罗指数法、普适法-模糊综合评价法、普适法-内梅罗指数法3种统计方法计算得到的级别差小于0的比例占比分别为34.62%、19.24%和46.16%,大于0的占比分别为19.23%、23.07%和26.92%,因此模糊综合评价法评价得到的地下水水质级别<普适法评价得到的地下水水质级别<内梅罗指数法评价得到的地下水水质级别.②模糊综合评价法最适用于研究区地下水水质现状评价,采用该方法评价得到研究区地下水水质分为优良(Ⅰ类)、良好(Ⅱ类)、较好(Ⅲ类)、较差(Ⅳ类)和极差(Ⅴ类) 5类(参照GB/T 14848—2018《地下水质量标准》),以良好和较好水质为主,造成地下水水质较差的组分主要为CODMn、总硬度、硝酸盐和汞.研究显示,级别差法可作为定量的地下水水质评价方法筛选技术,能够为地下水水质评价研究提供新的思路.

Groundwater quality assessment is the basis of groundwater pollution control and water environment management.Different assessment methods will result in different results of the groundwater quality.Therefore,it is crucial to choose the most appropriate assessment method.At present,there is little research on the scientific and reasonable selection of appropriate methods for groundwater quality assessment.In order to fill the gap,three methods were used to assess the groundwater quality in Luoyang City,including Nemerow index method,fuzzy comprehensive assessment method and universal exponential formula method based on immune evolutionary algorithm(below abbreviated as universal exponential formula method).Besides,the level difference method was established to quantitatively select the most suitable method for assessing the groundwater quality.The research result showed that the percentages of level difference which is smaller than 0 were 34.62%,19.24%and 46.16%,respectively,when fuzzy comprehensive method subtracted nemerow index method,universal exponential formula method subtracted fuzzy comprehensive method and universal exponential formula method subtracted nemerow index method.The corresponding percentages of level difference of greater than 0 were respectively 19.23%,23.07%and 26.92%.Therefore,the groundwater quality classes determined based on the fuzzy comprehensive method was the lowest,followed by the universal exponential formula and the nemerow index methods.The fuzzy comprehensive method was verified to be the most suitable for assessing the groundwater quality in the study area.Accordingly,groundwater quality in the study area was divided into excellent(ClassⅠ),good(ClassⅡ),relatively good(ClassⅢ),relatively bad(ClassⅣ),and bad(ClassⅤ)(Standard for Groundwater Quality(GB T 14848-2018)).The classes of good and relatively good dominated the study area.The relatively bad groundwater quality was mainly affected by COD Mn,total hardness,nitrate,and mercury.The research showed that the selection method of level difference can objectively and quantitatively determine the appropriate assessment methods of groundwater quality.