神东矿区高氟矿井水分布特征及形成机制

Formation mechanisms for elevated fluoride in the mine water in Shendong coal-mining district

神东矿区煤炭资源丰富,但淡水资源匮乏,高氟矿井水已成为制约矿井水循环利用的关键因素,然而高氟矿井水的来源和形成机制尚未进行过系统研究。系统采集了神东矿区62组不同水体样品,利用数理统计、离子比及因子分析等手段,在矿物溶解与沉淀,蒸发浓缩,阳离子交换,竞争吸附和人为污染作用等方面探讨了神东矿区高氟矿井水的F^(-)质量浓度特征和空间分布规律,并分析了其来源和形成机制。结果显示:神东矿区矿井水中F^(-)质量浓度为0.16~12.75 mg/L,平均值为5.01 mg/L,有77.78%的样品超过了《生活饮用水卫生标准》(GB5749—2006)。从空间分布看,神东矿区矿井水中F^(-)质量浓度呈现西北高,东南低的态势,高氟矿井水主要分布在布尔台矿和乌兰木伦矿等矿区。垂向上看,高氟地下水主要集中分布在埋深150~300 m,主要为3^(-1)煤和5^(-2)煤开采后产生的矿井水的埋深范围。偏碱性,高TDS,Na^(+),HCO_(3)^(-),和低Ca^(2+)是形成高氟矿井水的主要水化学环境。延安组是高氟矿井水最主要的补给来源。高氟矿井水的形成主要受含氟矿物的溶解控制,方解石和白云岩的溶解饱和影响了萤石等含氟矿物的溶解平衡,造成矿井水中F^(-)质量浓度的升高;阳离子交换作用提升了矿井水中Na^(+)的质量浓度,HCO_(3)^(-)的竞争吸附置换出了黏土矿物表面吸附态的F^(-),均促进了F^(-)在矿井水中富集,而蒸发浓缩和人类活动对高氟矿井水形成贡献较小。

Coal resource is rich and water resource is scare in the Shendong coal-mining area.High fluoride(F^(-))mine water has become a restricted factor for its recycling and utilization.However,the spatial distribution,source,and enrichment mechanisms of fluoride have not been fully understood.In this study,62 water samples were collected from the Shendong coal-mining area,Shanxi,China.Samples were analyzed to investigate the distribution,geochemical behavior,and formation mechanisms of fluoride by the correlation analysis,statistics and ions ration analysis combined with geological and hydrogeological conditions.The results show that the F^(-) concentrations in the mine water samples range from 0.16 to 12.75 mg/L,with a mean value of 5.01 mg/L.About 77.78% of the mine water samples exceed China’s national standards(1.00 mg/L)of F^(-)concentration.The F^(-) concentrations in the mine water is generally higher in the northwest and lower in the southeast of Shendong coal-mining area.The high F^(-) mine water is mainly distributed in the Buertai and Wulan Mulun mines and in the depth of 150-300 m,respectively.The F^(-) in the mine water is enriched in a water environment with high alkaline,high TDS,Na^(+),HCO_(3)^(-) and low Ca^(2+) content.The Yan’an groundwater is the main F^(-) source of high F^(-) mine water.The weathering of F^(-) bearing minerals is the main source of F^(-) in the mine water.Precipitation of dolomite and calcite reduces the Ca^(2+) content and promotes the dissolution of fluorite,generating an elevated F^(-) content.The cation exchange contributes to the increase of Na^(+) content and the high HCO_(3)^(-) environment reduces the adsorption capability of minerals,which promote the leaching of F^(-) into the mine water.Whereas,the evaporation and anthropogenic activities effect can be ignored.