三姑泉域岩溶地下水水化学特征及形成演化机制

Hydrogeochemical characteristics and evolution mechanism of karst groundwater in the catchment area of the Sangu Spring

三姑泉域岩溶地下水对晋东南地区居民生活及煤炭基地建设起着重要支撑作用。受煤炭资源大规模开采及人类活动加剧的影响,岩溶地下水水化学环境演变剧烈。通过分析三姑泉域的125个岩溶地下水、14个地表水及14个雨水样品,综合利用统计分析、变异系数分析、氢氧稳定同位素、Gibbs模型、离子相关关系、矿物饱和指数及因子分析,确定岩溶地下水的补给来源,分析三个子系统间岩溶水水化学特征、差异及形成演化机制。结果表明:岩溶水δD值为−77‰~−42‰,δ^(18)O值为−10.6‰~−4.5‰,且沿大气降雨线分布,显示岩溶地下水以大气降水入渗补给为主。子系统Ⅰ与子系统Ⅱ和子系统Ⅲ具有明显不同的水化学特征和水文地球化学演化进程。子系统Ⅰ岩溶水为低TDS软水,73%为HCO_(3)Ca(Mg)型水;子系统Ⅱ、子系统Ⅲ为低TDS软水高TDS硬水,水化学类型复杂,36%~40%为HCO_(3)·SO_(4)Ca·Mg型水,24%~45%为SO_(4)·HCO_(3)Ca型水。因子分析表明,区域岩溶地下水化学形成演化主要受控于水-岩作用、人类活动、地表水和局部裂隙水渗漏的影响。水-岩作用使得岩溶水化学组分以SO_(4)^(2-)、HCO_(3)-、SO_(4)^(2-)、Ca^(2+)、Mg^(2+)为主,采矿活动导致含量增加,农业活动导致NO_(3)-含量增加,污水排放和裂隙水渗漏导致Cl^(−)和Na+含量增加。研究结果可为岩溶水水资源开发和管理提供科学依据。

The karst groundwater in the catchment area of the Sangu Spring plays an important supporting role in the residents'living and coal base construction in southeastern Shanxi Province.With the large-scale coal mining and the intensification of human activities,the hydrochemistry of the regional karst groundwater has changed drastically.In this study,125 karst groundwater,14 surface water and 14 rain water samples were collected and tested.The descriptive statistical analysis,coefficient of variation analysis,hydrogen and oxygen stable isotopes,Gibbs model,ion correlation,mineral saturation index and factor analysis are comprehensively used to determine the replenishment sources of the karst groundwater,the differences of hydrochemical characteristics and evolution mechanism among the subsystems.The results show that theδD andδ^(18)O values of the karst groundwater range from−77‰to−42‰and from−10.6‰to−4.5‰,respectively,and the data points fall near the local meteoric water line(LMWL),indicating that the karst groundwater are mainly recharged by infiltration from precipitation.The hydrochemical characteristics and hydrogeochemical evolution processes between subsystemsⅠandⅡ-Ⅲwere obviously different.The karst groundwater of subsystemⅠhas low salinity and is soft water,and 73%of the groundwater is of HCO_(3)-Ca(Mg)type.However,the karst groundwater in subsystemsⅡandⅢchanges from low salinity and soft water to high salinity and hard water,and 36%to 40%of the water is of HCO_(3)·SO_(4)-Ca·Mg type and 24%to 45%,of SO_(4)·HCO_(3)-Ca type.Factor analyses show that the hydrochemical evolution processes of the regional karst groundwater are mainly controlled by water-rock interactions,human activities,leakage of surface water and local fissure water.Hydrochemical compositions of,HCO_(3)-,SO_(4)^(2-),Ca^(2+)and Mg^(2+)are mainly controlled by water-rock interactions.A higher concentration of SO_(4)^(2-)is controlled by mining activities,NO_(3)-is controlled by agriculture activities and Cl^(−)and Na+are controlled by sewage discharge and leakage of fissure water.The results will be instructive for improving the management and utilization of groundwater resources for the local government.