Evolution mechanism of a groundwater system in the opencast coalmine area in the typical prairie
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摘要: 伊敏露天煤矿位于中国东北部呼伦贝尔草原上，多年来的矿业活动对区域地下水环境造成严重影响，同时也给原本脆弱的草原生态环境带来威胁。文章以伊敏煤矿区地下水为研究对象，对比煤矿开采前（1973年）后（2016年）地下水系统的变化特征，运用流场对比、数理统计、Piper三线图、库尔洛夫式等对矿区地下水流场和水化学场的时空演化规律进行研究，以揭示强烈人工干预下草原矿区地下水与环境的相互作用机制。结果表明：露天煤矿开采活动使矿区地下水原生的还原环境变为氧化环境，煤层中的黄铁矿(FeS 2)被氧化、产酸并引发后续一系列反应，其结果导致矿区地下水pH值降低，总硬度(TH)、SO 2- 4、Fe 2+、Fe 3+、Ca 2+、Mg 2+离子浓度升高；水化学类型由以HCO 3—Na ·Ca ·Mg型为主演化为以HCO 3 ·SO 4—Na ·Ca ·Mg型为主；煤矿开采强烈疏排地下水加速了区域地下水循环速度，使地下水向着淡化方向发展，TDS、COD、Na ++K +等均呈降低趋势。Abstract: The Yimin coal mine is located in the Hulunbuir Prairie in northeastern China. The development of the mineral exploration of many years has caused tremendous influence on the regional groundwater environment and also threatened the vulnerable prairie ecological system. In this paper, the groundwater system in the Yimin coal mine area is taken as the research object. Characteristics of the groundwater system before and after the mining are compared in order to reveal the interaction mechanism of groundwater and environment under the intensive manual intervention in a prairie mining area. A comprehensive study of the temporal and spatial evolution of groundwater flow system and geo-chemical characteristics in the coal mining area is carried out by means of groundwater flow field comparison, mathematical statistics, comparison of contour map and Piper diagrams. The results show that the open pit coal mining increases access of O 2 to the subsurface and changes the original reduction environment into an oxidation environment, which facilitates sustained pyrite oxidation, acid production, and subsequent reactions. As a result, the pH value decreases, total hardness (TH) and concentrations of SO 2- 4, Fe 2+, Fe 3+, Ca 2+ and Mg 2+ increase significantly. In addition, the hydrochemical type of groundwater changes from HCO 3—Na ·Ca ·Mg type to HCO 3 ·SO 4—Na ·Ca ·Mg type. Under the influence of groundwater drainage of the opencast coal mining, the groundwater circulation is accelerated, which leads to an evolution of desalination of groundwater, and the chemical indicators such as TDS, COD and Na ++K + show a decreasing trend in the coal mine area.
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Key words:
- groundwater /
- hydrogeochemistry /
- oxidation conditions /
- water-rock interaction /
- ecological system /
- Yimin coal mine
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