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首页> 外文学位 >Hydrogeochemical evaluation and impact of remediation design on arsenic mobility at historical gold mine sites.
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Hydrogeochemical evaluation and impact of remediation design on arsenic mobility at historical gold mine sites.

机译：历史金矿场的水文地球化学评估和修复设计对砷迁移率的影响。

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摘要

Historical gold mine tailings at several sites in Nova Scotia, Canada are publicly accessible and may pose a threat to human and ecosystem health because of high arsenic (As) concentrations in the tailings (max 25 wt.%) and associated pore waters (up to 100 mg/L). Two of these sites, Montague and Goldenville, are under consideration for remediation. Similar tailings sites have been cleaned up by covering the mine wastes with soil. However, the tailings at Montague and Goldenville have been weathering for at least 70 years, leading to a wide range of As-bearing secondary minerals which may dissolve under a soil cover, releasing As to local waters. The challenge of remediating these heterogeneous tailings lies in the different Eh-pH niches in which iron arsenates (oxidizing, acidic), calcium-iron-arsenates (oxidizing, alkaline), and sulfides (reducing) are stable. The main objectives of this study were to: 1) characterize pre-remediation geochemical controls on As mobility in subsurface tailings; 2) establish hydrogeological influences on As mobility; and 3) identify geochemical changes that result when a low organic soil cover is applied to the tailings.;Variable weathering conditions over time have resulted in a continuum of saturation and redox environments and a range of As hosts in the tailings. In some areas, tailings pore waters are mixing with stream waters leading to As transport beyond the tailings. Applying a low organic soil cover does not induce reducing conditions in the tailings or cause dissolved As concentrations to increase compared to field pore water concentrations. This type of soil cover is effective in slowing sulfide mineral oxidation while maintaining stable conditions for secondary As-phases. The results of this research can be used to inform remediation decisions and guide ongoing environmental management of historical gold mine sites.;Pore water measurements were combined with bulk chemistry, scanning electron microscopy, and synchrotron micro-X-ray diffraction analyses, which were used to characterize the mineralogical composition of the tailings. Groundwater and surface water flow regimes throughout the tailings were defined through the use of piezometers and hydraulic conductivity measurements. Laboratory leaching experiments were used to assess the effects of a soil cover on the tailings.
机译：加拿大新斯科舍省多个地点的历史性金矿尾矿是可公开获得的，因为尾矿中砷（As）的浓度高（最高25 wt。％）和相关的孔隙水（最高可达100 mg / L）。这些站点中的两个Montague和Goldenville正在考虑中。通过用土壤覆盖矿山废物，清理了类似的尾矿场。但是，蒙塔古和戈登维尔的尾矿已经风化了至少70年，导致大量含砷的次生矿物质可能在土壤覆盖下溶解，从而向当地水体释放砷。补救这些异质尾矿的挑战在于不同的Eh-pH生态位，其中砷化铁（氧化，酸性），砷化铁钙（氧化，碱性）和硫化物（还原）是稳定的。这项研究的主要目的是：1）表征补救前地球化学对地下尾矿中砷迁移率的控制； 2）建立水文地质对砷迁移率的影响； 3）确定在尾矿上施加低有机土壤覆盖率时产生的地球化学变化。随时间变化的风化条件导致了连续的饱和和氧化还原环境以及尾矿中的一系列As主体。在某些地区，尾矿中的孔隙水与溪流水混合，导致砷转运到尾矿之外。与田间孔隙水浓度相比，施加低有机质土壤覆盖物不会在尾矿中引起还原条件或导致溶解的As浓度增加。这种土壤覆盖物可有效减缓硫化物矿物的氧化，同时保持次级As相的稳定条件。这项研究的结果可用于指导补救决策，并指导正在进行的金矿历史遗址的环境管理。孔隙水测量与体化学，扫描电子显微镜和同步加速器X射线衍射分析相结合来表征尾矿的矿物学组成。整个尾矿中的地下水和地表水流态是通过使用压力计和水力传导率测量来确定的。实验室浸出实验用于评估土壤覆盖物对尾矿的影响。

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  • 作者

    DeSisto, Stephanie L.;

  • 作者单位

    Queen's University (Canada).;

  • 授予单位 Queen's University (Canada).;
  • 学科 Geochemistry.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 520 p.
  • 总页数 520
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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