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Evaluating controls on potentially toxic element release in circum-neutral mine water: a case study from the abandoned Pb–Zn mines of Leadhills and Wanlockhead, South of Scotland, United Kingdom
Environmental Earth Sciences ( IF 2.8 ) Pub Date : 2020-07-11 , DOI: 10.1007/s12665-020-09108-x
Uche O. Chukwura , Andrew S. Hursthouse

Historic sulphidic Pb–Zn mining catchments at Leadhills and Wanlockhead, in the south of Scotland, UK have a legacy of mining of PbS (galena) and ZnS (sphalerite) from the twelfth century to the 1930s. The mining activities created tailing piles, ponds, adits and contaminated soils that contribute leaching and surface runoff of potentially toxic elements, particularly lead (Pb), which impact on the surface water and groundwater and are rapidly diluted in the wider catchment area. Studies by environmental regulators have shown that Pb, Cd and Zn in water can locally exceed the Environmental Quality Standards (EQS), particularly at Leadhills. To evaluate geochemical controls on release, 20 water sources (adits, surface water and near-surface groundwater) were sampled over four seasons (spring, summer, autumn and winter) over a 1-year period and characterized. Samples were circum-neutral pH from 6.3 to 7.9 (with average total dissolved solids < 55.0 mg/L), with no characteristics of acid mine drainage. The concentrations of PTEs in the water exceed UK EQS and WHO standards (and non-compliance on the Water Framework Directives). Geochemical modelling (GWB and PHREEQCv2) predicted mineral control on solubility which identified PbSO4 (anglesite), Fe2O3 ferric oxide (haematite), Fe3O4 (magnetite), FeCO3 (siderite), CaMg(CO3)2 (dolomite), CaCO3 (calcite) and Ca(Fe·Mg)(CO3)2 (ankerite) to be important. These were confirmed in solid phases analysed from tailings and sediments in contact with the hydrological cycle at the sites. Multivariate statistical analysis (PCA) of water samples associated with leaching through mine tailings showed strong seasonal variation with some elements (Fe, Cu, Cd, Pb, Na, Ca and Zn) with higher variance. The strong negative association of pH with soluble Zn, Cu, As, Cd and Pb highlights typical sulfide oxidation processes are taking place and supported by a positive correlation with temperature. Dissolution processes of mineral phases indicated by positive association of TDS and EC with Na, Ca and Zn. The data from PCA suggest contributions with potential for active generation of acid mine drainage and dissolution of solid phases influencing the release of PTEs into surface waters.

中文翻译:

评价环境中性矿井水中潜在有毒元素释放的控制措施:以英国苏格兰南部利德希尔斯和万洛克黑德的废弃铅锌矿为例

英国苏格兰南部利德希尔斯(Leadhills)和万洛克黑德(Wanlockhead)具有历史性的硫化铅铅矿开采流域,从十二世纪到1930年代都有铅铅矿(方铅矿)和锌铅矿(方铅矿)的开采历史。采矿活动造成了尾矿堆,池塘,坑洼和受污染的土壤,这些土壤对潜在的有毒元素(特别是铅(Pb))的浸出和地表径流产生了影响,这些元素对地表水和地下水产生影响,并在更广泛的集水区迅速被稀释。环境监管机构的研究表明,水中的Pb,Cd和Zn可以局部超过环境质量标准(EQS),尤其是在Leadhills。为了评估释放的地球化学控制效果,在四个季节(春季,夏季,秋季和冬季),并以1年为特征。样品的环境中性pH值为6.3至7.9(平均总溶解固体<55.0 mg / L),无酸性矿山排水特征。水中PTE的浓度超过英国EQS和WHO的标准(以及不遵守水框架指令的规定)。地球化学模型(GWB和PHREEQCv2)预测的矿物溶解度控制,从而确定了PbSO 4(角铁),Fe 2 O 3氧化铁(赤铁矿),Fe 3 O 4(磁铁矿),FeCO 3(菱铁矿),CaMg(CO 32(白云石),CaCO 3(方解石)和Ca(Fe·Mg)(CO 32(无铁矿)很重要。这些是在与水文循环接触的尾矿和沉积物中分析的固相中证实的。与通过矿山尾矿浸出相关的水样的多变量统计分析(PCA)显示,某些元素(铁,铜,镉,铅,钠,钙和锌)的强季节性变化具有较高的变异性。pH与可溶性Zn,Cu,As,Cd和Pb的负相关性很强,这表明典型的硫化物氧化过程正在发生,并与温度呈正相关。TDS和EC与Na,Ca和Zn的正相关表明矿物相的溶解过程。PCA的数据表明,酸性矿山排水的活跃产生和固相溶解的影响可能会影响PTE释放到地表水中。
更新日期:2020-07-11
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