淮河流域浅层地下水水化学特征10年对比分析及其环境变迁意义

Comparison of the hydrochemical characteristics of shallow groundwater in the Huaihe River Basin during a ten-year period and its significance to environmental change

浅层地下水是淮河流域重要的农业灌溉和农村分散供水水源,开展水化学特征演变分析能为区域用水安全、粮食安全保障提供科学依据。该次研究应用数值统计、舒卡列夫分类、Piper三线图、水质评价等方法,对比分析10年间隔(2009年和2019年)的水化学分析数据,总结浅层地下水化学特征变化规律。结果表明:10年之后,淮河流域浅层地下水更趋于弱碱性,溶解性总固体和总硬度平均值有所增长,但中位值略有下降,最大值抬升较多;优势离子排序没有变化,Na^(+)和HCO_(3)^(-)仍为淮河流域浅层地下水中主要优势离子,水化学组分空间变异性进一步增强;水化学类型仍以Na-Ca-Mg·HCO_(3)型和Ca-Mg·HCO_(3)型为主,但Na-Ca-Mg·HCO_(3)型占比大幅减少,Ca-Mg·HCO_(3)型略有增加,水化学类型趋于分散化和复杂化。比较而言,淮北平原西部浅层地下水化学变化主要表现为HCO_(3)型占比增加,水质趋于改善;淮北平原中部主要表现为Ca型、HCO_(3)型减少,Ⅰ—Ⅲ类水占比降幅明显;南四湖水系平原Na-Ca-Mg·HCO_(3)型占比显著下降,Na·SO_(4)-Cl型则显著增加,鲁北诸河水系平原Na·Cl型、Na·SO_(4)-Cl型显著增加,南四湖水系平原和鲁北诸河水系平原Ⅴ类水占比较大。

In the Huaihe River Basin,the shallow groundwater plays a significant role in rural scattered water supply and farmland irrigation.The analysis on hydrochemical characteristics changes of the shallow groundwater in the region will provide scientific basis for ensuring local water and food security.In order to summarize the variation rule of the shallow groundwater chemical properties,the study adopted numerical statistics,Shukarev classification,Piper three-line graph,and water quality evaluation to compare and analyze the hydrochemical data of a ten-year interval between 2009 and 2019.The results show that the shallow groundwater of Huaihe Basin has weakly alkaline pH values,rising mean values of total dissolved solids and total hardness but decreasing median and maximum values of these variables.There is no order change of the main ions,which are still dominated by Na^(+)and HCO_(3)^(-)in the shallow Huaihe groundwater with further enhancement of spatial variability of the hydrochemical components.Na-Ca-Mg·HCO_(3)and Ca-Mg·HCO_(3)continued to be the main hydrochemical types,but the proportion of Na-Ca-Mg·HCO_(3)decreased apparently while Ca-Mg·HCO_(3)increased slightly,showing the diversification and complication of the hydrochemical types.Comparatively speaking,the hydrochemical changes of the shallow groundwater in the Western Huaibei Plain are mainly reflected in the proportion increase of HCO_(3)^(-)type and the water quality improvement;while those in the Central Huaibei Plain are characterized with the decrease of the Ca type-HCO_(3)type and obvious proportion decrease of I-III type water.The proportion of Na-Ca-Mg·HCO_(3)dramatically decreased while the ratio of Na·SO_(4)-Cl significantly increased in the the Nansihu Plain,and the proportion of Na·Cl and Na·SO_(4)-Cl increased evidently in the Lubei River drainage plain,on both of the two plains the V type water account for a larger part.