Bhavsar Satyendra P, Gandhi Nilima, Diamond Miriam L
Department of Chemical Engineering, University of Toronto, Toronto, Ontario, Canada.
Chemosphere. 2008 Jan;70(5):914-24. doi: 10.1016/j.chemosphere.2007.06.082. Epub 2007 Aug 20.
Atmospheric deposition of metals emitted from mining operations has raised metal concentrations in the surrounding soils. This repository may be remobilized and act as a source of metals to nearby surface aquatic systems. It is important to understand metal dynamics and the impact of various chemistry and fate parameters on metal movement in the soil environment in order to evaluate risk associated with metals in terrestrial ecosystems and accurately establish critical discharge limits that are protective of aquatic biota. Here we extend our previously developed coupled multispecies metal fate-TRANsport and SPECiation/complexation (TRANSPEC) model, which was applicable to surface aquatic systems. The extended TRANSPEC, termed TRANSPEC-II, estimates the partition coefficient, K(d), between the soil-solid and -soluble phases using site-specific data and a semi-empirical regression model obtained from literature. A geochemical model calculates metal and species fractions in the dissolved and colloidal phases of the soil solution. The multispecies fugacity/aquivalence based fate-transport model then estimates inter-media transport rates such as leaching from soil, soil runoff, and water-sediment exchanges of each metal species. The model is illustratively applied to Ni in the Kelly Lake watershed (Sudbury, Ontario, Canada), where several mining operations are located. The model results suggest that the current atmospheric fallout supplies only 4% of Ni removed from soil through soil runoff and leaching. Soil runoff contributes about 20% of Ni entering into Kelly Lake with the rest coming from other sources. Leaching to groundwater, apart from runoff, is also a major loss process for Ni in the soil. A sensitivity analysis indicates that raising soil pH to above 6 may substantially reduce metal runoff and improve water quality of nearby water bodies that are impacted by runoff.
采矿作业排放的金属通过大气沉降增加了周边土壤中的金属浓度。这一储存库中的金属可能会再次活化,并成为附近地表水生系统的金属来源。了解金属动态以及各种化学和归宿参数对土壤环境中金属迁移的影响,对于评估陆地生态系统中与金属相关的风险以及准确确定保护水生生物群的临界排放限值至关重要。在此,我们扩展了我们之前开发的适用于地表水生系统的多物种金属归宿-迁移与形态/络合耦合(TRANSPEC)模型。扩展后的TRANSPEC模型(称为TRANSPEC-II)使用特定场地数据和从文献中获得的半经验回归模型来估算土壤固相和可溶性相之间的分配系数K(d)。一个地球化学模型计算土壤溶液溶解相和胶体相中金属及其物种的分数。然后,基于多物种逸度/等效性的归宿-迁移模型估算各金属物种的介质间迁移速率,如从土壤中的淋溶、土壤径流以及水-沉积物交换。该模型以加拿大安大略省萨德伯里凯利湖流域的镍为例进行了应用,该流域有多个采矿作业。模型结果表明,当前的大气沉降仅提供了通过土壤径流和淋溶从土壤中去除的镍的4%。土壤径流贡献了进入凯利湖的镍的约20%,其余来自其他来源。除径流外,镍向地下水的淋溶也是土壤中镍的一个主要损失过程。敏感性分析表明,将土壤pH值提高到6以上可能会大幅减少金属径流,并改善受径流影响的附近水体的水质。