川西北尾矿堆中砷迁移行为及其耦合作用下渗透性研究

Arsenic pollution from tailing waste in mine area is a common environmental geological problem in the gold and uranium mines of the northwest of Sichuan province of China. The transport of arsenic in tailing not only is controlled by the common factors, but also determined by the permeability of system due to the various mineralogical characteristics and water-rock interactions. So, the problem of permeability is need to be considered individually. No matter how good or bad the hydraulic conductivity of tailing system develops to be, will directly affect the mobilization or retention of arsenic in tailing. In addition, the secondary mineralization, reductive dissolution and biological clogging will play obvious actions on permeability. So the study on arsenic transport and permeability under coupling interactions has scientific significance. However, these processes haven’t been understood until now. This study will systematically investigate arsenic transport and permeability under coupling interactions aimed at high arsenic-content tailing waste in the northwest of Sichuan province, China. Based on the monitoring of arsenic mobilization and on-line hydraulic conductivity, reveal the coupling mechanisms controlling transport and permeability, such as mineralization, biologically reductive dissolution and so on. With these understanding, we continue to investigate the transport behavior of arsenic and hydraulic conductivity of passivated tailing system from three different cover patterns (mixed-style, interlayer-style and cap cover-style dumps), and reveal their mechanisms. The successful practice of this project will benefit for the understanding of transport in the water-rock interaction, further scientifically making treatment measure.

矿区含砷尾矿污染是我国川西北铀和金矿面临的一个常见环境地质问题。尾矿堆中砷不仅受经典迁移因素控制，而且由于其堆体矿物多样及其各种水岩作用存在，这使得迁移过程需要对渗透性进行单独考虑。堆体渗透性优劣都直接影响砷的迁移或再固定，同时次生矿化、还原沉淀和微生物溶解和堵塞这些长期作用，又集中体现在渗透性上。因此研究砷迁移过程及其耦合渗透性的意义明显，然而目前对这些过程尚未认识清楚。本项目拟针对川西地区高砷尾矿开展砷迁移及其耦合作用下渗透性研究。通过多因素迁移和在线渗透性监测，揭示水岩作用过程中矿化、生物还原溶解等对迁移和体系渗透性的耦合机制。基于此进一步对比尾矿堆混层、互层和盖层三种不同处理方式下砷迁移和渗透性，揭示其中有效控制机制。本项目的实施有助于丰富水岩作用中的迁移认识，并建立长效尾矿治理方案。

本项目对砷黄铁矿和雄黄矿区砷迁移行为进行调查，研究发现1）砷黄铁矿在氧化还原波动条件下，释放砷的行为有显著差异；2）季节性变化温度、微生物群落变化是溪流中砷迁移和形态主要驱动因素，通过沉积物总量结合流域流量体积、流域段流过时间建立的模型，预测旱季2.39mg/L，雨季8.98mg/L的砷，这与实际测得旱季3.28mg/L，雨季10.4mg/L的结果较为接近。3）藻的存在对溪流底部释放砷量有显著影响，发现砷（V）是主要形态占 70-89%，砷（III）是次要形态占 30-11%，地表水体砷最高浓度为 10400μg/L，旱季水体砷浓度要低于雨季砷浓度，通过模型计算每年有 8.3 吨的砷向外输出。微生物群落变化发现，该区域 Protecbacteria，Bacteroidetes，Cyanobacteria，Firmicutes和Verrucomicrobia 是砷矿区溪流主要微生物群落；4）利用钢厂尾渣slag能够很好的阻滞砷迁移扩散，孔隙水渗透性变化能够被水压传感器捕获，且受次生矿化影响。5）贫铁型硫化砷矿区，诸如雄黄矿，含砷硫化物中杂质铁能够参与砷的氧化过程，加速砷的释放。