Mertz Samuel, Devau Nicolas, Thouin Hugues, Battaglia-Brunet Fabienne, Norini Marie-Paule, Crampon Marc, Le Forestier Lydie
BRGM, BP 36009, 45060 Cedex 2 Orléans, France; Univ. Orléans, CNRS, BRGM, ISTO, UMR 7327, F-45071, Orléans, France.
BRGM, BP 36009, 45060 Cedex 2 Orléans, France.
Sci Total Environ. 2025 Jan 15;960:178248. doi: 10.1016/j.scitotenv.2024.178248. Epub 2025 Jan 6.
Mine tailing deposits pose a global problem, as they may contain metal contaminants in various geochemical forms and are likely to be leached from the surface into the underlying groundwater, which can result in health and/or environmental risks. Unfortunately, little is currently known regarding the water flow and mass balance related to leaching in the vadose zone as these factors are still difficult to measure at the field scale. A pilot-scale experiment was run in a 1 m instrumented column for 6 months to address this issue. This 70 cm high column was filled with highly Pb-contaminated tailings and then watered regularly. The top half remained unsaturated while the bottom half was kept saturated. Continuous water flow and water saturation measurements were recorded and the physico-chemical properties of the soil solutions were monitored weekly at different levels in the column. A 1D multicomponent reactive transport model was built to simulate the fate and transport of Pb as well as other elements. The variably saturated water flow was simulated using the Richards equation, while the van Genuchten analytic form was used to describe the unsaturated soil hydraulic properties. The main processes considered to simulate the reactive transport were advection-dispersion, thermodynamic equilibrium, and kinetically-controlled dissolution-precipitation reactions. The most reactive Pb-bearing phases accounted for in the simulation were anglesite (PbSO) and plumbojarosite PbFe(SO)(OH). The simulations accurately reproduced the water flow and mass balance as well as the drop of 2 pH units experimentally measured in the pore solution. This trend resulted from plumbojarosite dissolution followed by ferrihydrite precipitation. The increased Pb concentration in the soil solution induced by the dissolution of Pb-bearing phases was partially offset by Pb-sorption onto newly formed iron oxides and the precipitation of secondary mineral phases, e.g. anglesite. The modeling results could be used to assess potential risks of groundwater contamination by mine tailings.
尾矿沉积物是一个全球性问题，因为它们可能含有各种地球化学形态的金属污染物，并且很可能从地表淋滤到下层地下水中，这可能导致健康和/或环境风险。不幸的是，目前对于渗流带中与淋滤相关的水流和质量平衡知之甚少，因为这些因素在现场尺度上仍然难以测量。为了解决这个问题，在一个1米长的仪器化柱中进行了中试规模的实验，为期6个月。这个70厘米高的柱子填充了高铅污染的尾矿，然后定期浇水。上半部分保持不饱和状态，而下半部分保持饱和状态。记录了连续的水流和水饱和度测量数据，并每周在柱中的不同深度监测土壤溶液的物理化学性质。建立了一个一维多组分反应传输模型来模拟铅以及其他元素的归宿和传输。使用理查兹方程模拟可变饱和水流，同时使用范格内uchten解析形式描述非饱和土壤水力性质。模拟反应传输时考虑的主要过程是平流扩散、热力学平衡和动力学控制的溶解-沉淀反应。模拟中考虑的最具反应性的含铅相是硫酸铅矿（PbSO）和羟铁铅矾PbFe(SO)(OH)。模拟准确地再现了水流和质量平衡以及在孔隙溶液中实验测量到的2个pH单位的下降。这种趋势是由羟铁铅矾溶解后接着水铁矿沉淀导致的。含铅相溶解引起的土壤溶液中铅浓度的增加部分被新形成的铁氧化物对铅的吸附以及次生矿物相（如硫酸铅矿）的沉淀所抵消。建模结果可用于评估尾矿对地下水污染的潜在风险。
