废弃矿井地下水中多环芳烃的降解与迁移机理

Coal is the dominant fossil energy for China. During the past decades of high intensity mining thousands of coal mines have been closed because of the coal exhaustion or national policy. Due to the close of coal mine, the environmental problems like the groundwater contamination especially become urgent. Groundwater depression funnels generated because of the over-pumping groundwater in mining process, the huge impact of which lead to the change of interrelation between hydrodynamics and hydrochemistry in surrounding area. Groundwater storage and transportation condition might be destroyed again since the recovery of water level after the close of coal mine. The open system will be converted to closed-semi closed system in mining process. Accoding to the field investigaiton, organic pollutants like the emulsified oil, polycyclic aromatic hydrocarbons(PAHs) generated during mining process, as well from the mining field, coal-bearing strata and adjacent aquifer severely contaminated the groundwater, had turned the abandoned coal mine to potential pollution source.The organic pollutants migrates, degrades and transforms under the complex hydrogeochemical condition of the abandoned coal mine. This project will focus on studying the degradation and transformation mechanism of PAHs in the closed condition of the abandoned coal mine, revealing the influence of different hydrogeochemical conditions (temperature, pH, inorganic salts, organic matter and microbial) on the transformation degradation mechanism of PAHs, meanwhile determining the degradation products and the destination of PAHs at the abandoned coal mine. Migration model of organic pollutants in the groundwater of abandoned coal mine will be constructed. The special hydrogeological structure of the abandoned mine will be quantitively characterized by the simulating experiment and numerical simulation results. A COMSOL Multiphysics simulator will be developmentd to reveal the migration and transformation rule of PAHs at abandoned coal mine. The accomplishments of the study will enrich coal mine hydrogeochemistry theory, and have important application value on risk assessment on groundwater contamination at abandoned coal mine.

随着我国煤矿关闭数量日趋增加，由矿井关闭引发的地下水污染问题逐渐凸显。煤矿关闭后，地下水位回弹，造成串层污染，尤其是废弃矿井中乳化油、多环芳烃等有机污染物在复杂水文地球化学条件下会发生迁移、降解和转化。本项目重点研究多环芳烃在矿井封闭条件下的降解转化机理，揭示不同水文地球化学条件（温度、pH、无机盐、有机质和微生物）对多环芳烃的转化、降解的影响机制，明确多环芳烃在废弃矿井中降解产物及归宿；基于废弃矿井特殊的水文地质结构，通过实验模拟和数值模拟量化关键水文地质参数，构建废弃矿井地下水有机污染物迁移模型，揭示废弃矿井地下水中多环芳烃迁移规律。上述研究成果将进一步丰富煤矿水文地球化学理论，并对废弃矿井地下水有机污染风险评估具有重要的应用价值。

项目通过现场调研、理论分析、实验模拟和数值模拟，重点研究了废弃矿井封闭条件下地下水中多环芳烃的迁移转化机理，以及不同环境因子对多环芳烃降解转化的影响，在区域废弃矿井环境管理、地下水污染风险防控方面有一定的指导意义。主要结论包括：（1）研究了徐州、淮南、淄博、峰峰、兖州、阳泉等典型煤矿区环境中多环芳烃的赋存特征，结果表明煤、井下污泥及矿井水中多环芳烃含量分别为0.388~28.665 μg/g、0.64~24.02 μg/g和0.56~4.61 μg/L，针对矿井水中多环芳烃生态风险进行评估，发现研究区矿井水多环芳烃污染整体为高风险。（2）确定了矿井水、井下污泥中多环芳烃的主要来源于原煤释放及煤的燃烧，基于原煤-矸石释放源完成了360天的废弃矿井模拟实验，结果表明封闭条件下煤-矸石中低环多环芳烃更易于向水环境中迁移，矿井水中乳化油等有机物会促进多环芳烃的释放。（3）分析了600-700m深度煤矿井下细菌群落的分布，煤矿井下最丰富的细菌门类为变形菌门(平均占比36.9%)、厚壁菌门(平均占比24.0%)、放线菌门(平均占比20.0%)及绿湾菌门(平均占比6.8%)，主要受pH、C/N等环境因素影响，通过135天的细菌群落演替模拟实验，发现煤矿关闭后，部分好氧菌群（如节杆菌属）逐渐被厌氧菌及兼性厌氧菌（如芽孢杆菌）取代，群落多样性呈先增加后减少的趋势。（4）筛选了封闭条件下多环芳烃高效降解菌，并利用该菌株开展了菲降解实验，结果表明该菌株通过邻苯二甲酸途径降解菲，符合一级动力学方程，在25~30℃、弱碱性条件下降解效率较高，可达95%以上，同时，降解过程还受矿井水中铁、硫酸盐等因素的影响；此外，研究筛选选了菲的专性降解菌群，结果表明封闭条件下不同降解菌群可通过邻苯二甲酸途径或菲醌途径降解菲。（5）基于GMS模拟软件的MT3DMS模块及多环芳烃释放参数，模拟了徐州贾汪矿区闭矿后地下水中多环芳烃的迁移规律。