水化学及硫同位素对大冶矿区地下水硫酸盐污染的指示

Indication of Hydrochemistry andδ^(34)S-SO_(4)^(2‒)on Sulfate Pollution of Groundwater in Daye Mining Area

铜铁矿区周边地下水硫酸盐污染是生态环境研究关注的热点问题,精确识别硫酸盐来源及迁移途径对于矿区周边地下水污染防控和供水安全至关重要.利用水化学与硫同位素耦合分析,结合矿区水文地质条件和潜在污染源分布,探讨了区内地下水硫酸盐污染特征、来源及迁移途径.区域内地下水包括松散岩类孔隙水、碳酸盐岩裂隙岩溶水及岩浆岩风化裂隙水,水化学类型主要为HCO_(3)∙SO_(4)-Ca型,水化学组分主要来源于硅酸岩、碳酸盐岩和硫酸盐矿物的溶解以及硫化物氧化;地下水中SO_(4)^(2‒)含量范围为44.4~2089.0 mg/L,高值区主要分布在洪山溪尾矿库、矿渣堆存处及矿业生产区附近;地下水中δ^(34)S-SO_(4)^(2‒)在2.6‰~31.5‰之间,反映其SO_(4)^(2‒)具有多源性.地下水中SO_(4)^(2‒)的主要来源包括含水层中石膏矿物的溶解和黄铁矿等含硫矿物氧化输入,高含量的SO_(4)^(2‒)主要来源于黄铁矿氧化的贡献;矿坑排水、尾矿渗漏、选矿粉尘沉降淋滤下渗以及废水渗漏是地下水硫酸盐污染的主要途径.

Sulfate pollution of groundwater around copper and iron mining areas is a hot issue in ecological environment research.It is very important to identify the sources and migration routes of sulfate in the groundwater system for the prevention of groundwater pollution and the safety of water supply in the mining area.Combined with the hydrogeological setting and the distribution of potential pollutant sources in the mining area,the coupled analysis of hydrochemistry andδ^(34)S-SO_(4)^(2‒)was carried to explore the characteristics,sources and migration pathways of groundwater sulfate pollution in the area.The results show that the groundwater in the area included the pore water in the sedimentary aquifers,the karst water of carbonatite and the fissure water of igneous rocks.The main hydrochemical type was HCO_(3)·SO_(4)-Ca.The formation of hydrochemical components mainly included the dissolution of silicate,carbonate and sulfate minerals,as well as the oxidation of sulfide.The content of SO_(4)^(2‒)ranged between 44.4 mg/L and 2089.0 mg/L.The groundwater with elevated SO_(4)^(2‒)concentration occurred near the Hongshan River tailings reservoir,the slag heap and the industrial areas.The value ofδ^(34)S in regional groundwater ranged between 2.6‰and 31.5‰,indicating that SO_(4)^(2‒)came from multiple sources.The sources of sulfate in groundwater included the dissolution of gypsum,the oxidation of sulfide such as pyrite.The maximum of SO_(4)^(2‒)attributed to the oxidization of pyrite.Mine drainage,tailing leakage,the settling of dust and wastewater infiltration were the main pathways of groundwater pollution.