风化作用下煤矸石中重金属释放的地球化学效应

发布时间：2018-10-15 07:53

【摘要】：在风化作用下,长期露天堆放或填埋利用煤矸石中污染物释放直接影响周边环境。本文以陕西韩城桑树坪和燎原矿区煤矸石为研究对象,研究物理风化(煤矸石粒径大小)和化学风化(淋滤作用、冻融作用、浸泡作用)对煤矸石污染物释放的影响。本文结合淋滤实验、冻融循环实验、浸泡实验分析粒径大小和硫含量高低对煤矸石中污染物释放的影响和冻融循环过程中煤矸石重金属形态转化特征,解释煤矸石中污染物释放的地球化学机理,最后评价了风化作用下煤矸石中污染物释放的潜在生态风险。1.淋滤风化作用下,淋出液中HCO3-、Cl-、K+、Ca2+、Mg2+、Cd、Fe、Mn、Ni、Zn均表现出快速释放,淋滤初期至淋滤后期浓度急剧下降后逐渐趋于平稳。粒径大小对淋出液常量组分影响较大,粒径越小,释放越快。硫含量高的煤矸石淋出液抑制其常量组分的释放,促进其重金属元素的释放。2.冻融风化作用直接影响重金属元素的赋存形态。冻融强度越高:As、Cd、Cu从有机态向可交换态转化比例增高,Cr从碳酸盐态向可交换态以及铁锰态向碳酸盐态转化比例增高,Pb从铁锰态向可交换态转化比例越大,从有机态向碳酸盐态转化比例越小。3.冻融风化作用直接影响煤矸石污染物的浸出释放,冻融强度越高,矿物晶格中As、Cd、Cr、Cu、Pb越易浸出,使之浸出浓度远高于低强度冻融作用下煤矸石浸出液的浓度。4.冻融强度和矸石粒径直接影响矸石-水的地球化学作用,矸石粒径越小,冻融强度越高,其矿物大量溶解释放而使浸出液各矿物饱和指数明显升高。5.冻融风化作用下煤矸石中重金属RAC生态风险指数评价结果为:NiCdCuPbAsCr。冻融强度越高,重金属As、Cd、Cu、Pb潜在RAC风险指数越高。冻融作用后的矸石在水的浸泡作用下,其Hakanson潜在生态风险指数随冻融作用的进行呈现出先升高后降低的变化趋势,其Hakanson潜在生态风险指数为:CdCuAsPbCr。
[Abstract]:Under the action of weathering, long-term open-air stacking or landfill utilization of coal gangue release of pollutants directly affect the surrounding environment. In this paper, the effects of physical weathering (particle size of coal gangue) and chemical weathering (leaching, freeze-thawing, soaking) on the release of coal gangue pollutants were studied. In this paper, the effects of particle size and sulfur content on the release of pollutants from coal gangue were analyzed by means of leaching experiment, freeze-thaw cycle experiment and soaking experiment, and the transformation characteristics of heavy metals in coal gangue during freeze-thaw cycle were analyzed. The geochemical mechanism of pollutant release from coal gangue is explained and the potential ecological risk of pollutant release from coal gangue under weathering is evaluated. Under the action of leaching and weathering, the HCO3-,Cl-,K, Ca2, Mg2 and Cd,Fe,Mn,Ni,Zn in the leaching solution were rapidly released, and the concentration of HCO3-,Cl-,K, Ca2, Mg2 and Cd,Fe,Mn,Ni,Zn decreased sharply from the early stage to the late stage of leaching. The size of particle size has a great influence on the constant component of leaching solution, the smaller the particle size, the faster the release. The leaching solution of coal gangue with high sulfur content inhibited the release of its main components and promoted the release of heavy metal elements. 2. Freezing and thawing weathering directly affect the occurrence of heavy metal elements. The higher the freeze-thaw intensity is, the higher the conversion ratio of As,Cd,Cu is from organic state to exchangeable state, the ratio of Cr transition from carbonate state to exchangeable state and iron and manganese state to carbonate state, and the ratio of Pb transformation from iron and manganese state to exchangeable state is higher. The ratio of transformation from organic state to carbonate state is smaller. 3. Freeze-thaw weathering directly affects the leaching and release of coal gangue pollutants. The higher the freeze-thaw intensity, the easier As,Cd,Cr,Cu,Pb leaching in mineral lattice, which makes the leaching concentration much higher than the concentration of coal gangue leachate under low intensity freezing and thawing. 4. The freezing and thawing strength and the particle size of gangue directly affect the geochemistry of gangue and water. The smaller the particle size of gangue, the higher the freezing and thawing strength, the higher the mineral dissolution and release, the higher the saturation index of each mineral in the leachate. The evaluation results of RAC ecological risk index of heavy metals in coal gangue under freezing and thawing weathering are as follows: NiCdCuPbAsCr. The higher the freeze-thaw intensity, the higher the potential RAC risk index of heavy metal As,Cd,Cu,Pb. After freezing and thawing, the Hakanson potential ecological risk index of gangue increased first and then decreased with the freezing and thawing. The Hakanson potential ecological risk index of gangue was as follows: CdCuAsPbCr..
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD849.5;X752

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