淮北煤田中层水源微量元素地球化学演化及其对矿区表生环境的响应

The rising issue of underground water pollution and drinking water safety concerns both the academics and the general public. Up till now, there are no authoritarian explanations to questions such as: How is mid-layer water contaminated by mining and surface environmental media (e.g. coal gangue and mining waste water, etc.) and to what extent? Where does pollution come from and through which channels? What are the pollutants and counteractants? and so on. This project takes as an example of the Huaibei mining area, which is a concealed minefield in North China, to monitor and study on selected surface environmental media in the mining area which may be connected with mid-layer water. The study aims to expound, under intensive water supply, the geochemical evolution of trace elements in mid-layer water and the pollution caused by toxic and hazardous trace elements; to uncover the fate of trace elements, toxic and hazardous ones in particular, in the system of “surface-shallow layer-mid layer”; through simulated experiments and field studies to explore how factors, such as the thickness of the first aquiclude and lithological properties, constrain the trace elements in “surface-shallow layer” from seepage to mid layer. With references to the hydrogeological features of the aquifers and aquicludes, general composition of underground water, and researches on environmental isotopes, it is to identify the source of toxic and hazardous trace elements in mid-layer water, as well as polluting channels, and to discuss the coupling relation between the seepage field of mid-layer water and the geochemical field of the trace elements, laying the scientific foundation for water protection from the roots.

饮用地下水污染及饮水安全问题日益受到学界和民众的广泛关注。采煤扰动下，矿区表生环境介质（如煤矸石、矿井废水等）对中层水源是否有影响？影响程度如何？污染来源和途径是什么？污染因子及制约因素有哪些？等科学问题，至今没有权威的解答。本项目拟以华北隐伏型煤田淮北煤田为例，对与中层水源具有潜在联系的矿区典型表生环境介质进行布点监测，以期阐明高强度供水条件下中层水源微量元素地球化学演变特征及有害有毒微量元素污染现状；揭示“表生—浅层—中层”环境系统中微量元素特别是有害有毒微量元素的归趋机制；通过模拟实验和野外印证，探索第一隔水层厚度及岩性等因素对“表生—浅层”环境中微量元素向中层环境归趋的制约机理；并结合含（隔）水层水文地质条件、地下水常规成分及环境同位素等研究成果，明确中层水源有害有毒微量元素的污染来源和途径、探讨中层水渗流场与微量元素地球化学场之间的耦合关系，为从源头上保护水源地环境提供科学依据。

矿区表生环境特殊而复杂，“三废”（矸石山、粉煤灰、岩煤粉尘、矿井水）以及地表纳污水体等普遍存在，有害或有毒微量元素在大规模供水的影响下，参与地球化学循环，有可能影响供水水源地的水质，威胁饮水安全。鉴于此，本项目通过对淮北煤田“表生—浅层—中层”环境中微量元素及常规水化学组分的动态监测，开展了以下研究：. ①进行了矿区表生环境影响下的浅—中层水常规组分含量特征及其形成作用研究，分析了浅层、中层水之间的水文地球化学联系，为矿区“表生—浅层—中层”环境水文地球化学循环研究奠定了基础。. ②开展了浅—中层水微量元素含量特征研究，揭示了微量元素地球化学作用及迁移转化机制，筛选出主要污染元素（如Fe、Mn、As、F等），进行了地球化学循环与溯源研究，为中层水源饮用途径的健康风险评价提供了依据。. ③开展了矿区表生环境影响下的地表水、浅层及中层水D/18O同位素监测，得到了地表水、浅层水和中层水的D、18O同位素线性方程，为浅—中层水的补给来源研究提供了科学依据。. ④应用多种方法对矿区表生环境影响下的浅—中层水进行了环境质量及微量元素健康风险评价，发现中层水中Cr的致癌风险大于Cd，经饮水途径摄入的微量元素对人体产生致癌风险较小。. ⑤开展了微藻去除矿区地下水中Fe、Mn、Cu、As的实验研究，可以为矿区中层水源地环境保护与微量元素污染修复提供借鉴。. ⑥基于矿区中层水渗流场与水化学场耦合机制研究，提出了从源头上保护中层水水环境的措施，为矿区供水水源地科学管理与合理开发利用提供参考。. 取得的主要成果是，获得了矿区不同水体D-18O曲线并探讨了浅—中层水补给源，阐明了浅—中层水微量元素地球化学特征及其对pH的响应机制，定量评价了浅—中层水环境质量与健康风险程度，研究了矿区土壤微量重金属元素地球化学特征及来源以及矿区不同动态水体之间的水文地球化学联系，实验论证了微藻去除矿区地下水中Fe、Mn、Cu、As的可行性并探讨了地下水环境演化对矿业工程扰动的响应特征。