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Chromium mobility in ultramafic areas affected by mining activities in Barro Alto massif, Brazil: An isotopic study
Chemical Geology ( IF 3.9 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.chemgeo.2020.120000
Viviana Bolaños-Benítez , Eric D. van Hullebusch , Jean-Louis Birck , Jérémie Garnier , Piet N.L. Lens , Mickaël Tharaud , Cécile Quantin , Yann Sivry

Abstract This work studies the potential release of Cr from solids to surface water and groundwater, and the related isotopic compositions, in a nickel laterite ore deposit from Barro Alto in Brazil (in the State of Goias). This ultramafic system is characterized by elevated concentrations of chromium (Cr). Even largely immobile Cr may be naturally leached from weathering profiles such as laterite to the surface and groundwater. This system is exploited for metal production, and both mining and metallurgical activities result in a significant increase in the trivalent (Cr(III)) and hexavalent chromium (Cr(VI)) concentrations released into the environment via runoff. Among all the samples collected, ores contained higher amounts of chemically and isotopically exchangeable Cr(VI) (ECr(VI)) with values as high as 104 (± 8) mg kg−1. δ53Cr increased from −0.28 (± 0.01)‰ to −0.05 (± 0.01)‰ and the ECr(VI) value was up to 30 times higher in deep soils than at the surface (up to 7 (± 1) mg kg−1). Chemically extracted Cr(VI) (ECr(VI)-KH2PO4) displayed positive δ53Cr value (1.69 (±0.03) ‰) with a similar Cr isotopic composition as the ones measured in freshwater sampled in and around the mine area. It appears that Cr is primarily released as Cr(VI), i.e. the toxic species, and becomes increasingly more available as it moves from the soil profile to the ores and mining residues. Based on the differences in the Cr isotopic composition, this study proves that δ53Cr can be used in environmental studies to trace Cr leaching.

中文翻译:

受巴西巴罗阿尔托地块采矿活动影响的超镁铁质区域的铬迁移率:一项同位素研究

摘要 这项工作研究了巴西巴罗阿尔托(戈亚斯州)的镍红土矿床中 Cr 从固体释放到地表水和地下水中的潜在释放,以及相关的同位素组成。这种超镁铁系统的特点是铬 (Cr) 浓度升高。甚至大部分不动的 Cr 也可能从风化剖面(如红土)中自然浸出到地表和地下水中。该系统用于金属生产,采矿和冶金活动导致通过径流释放到环境中的三价铬 (Cr(III)) 和六价铬 (Cr(VI)) 浓度显着增加。在收集的所有样品中,矿石中含有更多的化学和同位素可交换的 Cr(VI) (ECr(VI)),其值高达 104 (± 8) mg kg-1。δ53Cr 从 -0.28 (± 0.01)‰ 增加到 -0.05 (± 0.01)‰,ECr(VI) 值在深层土壤中比表层高 30 倍(最高 7 (± 1) mg kg−1) )。化学提取的 Cr(VI) (ECr(VI)-KH2PO4) 显示出正 δ53Cr 值 (1.69 (±0.03) ‰),其 Cr 同位素组成与在矿区及其周围取样的淡水中测得的同位素组成相似。似乎 Cr 主要以 Cr(VI)(即有毒物质)的形式释放,并且随着它从土壤剖面移动到矿石和采矿残渣中而变得越来越容易获得。基于Cr同位素组成的差异,本研究证明δ53Cr可用于环境研究以示踪Cr浸出。化学提取的 Cr(VI) (ECr(VI)-KH2PO4) 显示出正 δ53Cr 值 (1.69 (±0.03) ‰),其 Cr 同位素组成与在矿区及其周围取样的淡水中测得的同位素组成相似。似乎 Cr 主要以 Cr(VI)(即有毒物质)的形式释放,并且随着它从土壤剖面移动到矿石和采矿残渣中而变得越来越容易获得。基于Cr同位素组成的差异,本研究证明δ53Cr可用于环境研究以示踪Cr浸出。化学提取的 Cr(VI) (ECr(VI)-KH2PO4) 显示出正 δ53Cr 值 (1.69 (±0.03) ‰),其 Cr 同位素组成与在矿区及其周围取样的淡水中测得的同位素组成相似。似乎 Cr 主要以 Cr(VI)(即有毒物质)的形式释放,并且随着它从土壤剖面移动到矿石和采矿残渣中而变得越来越容易获得。基于Cr同位素组成的差异,本研究证明δ53Cr可用于环境研究以示踪Cr浸出。随着它从土壤剖面移动到矿石和采矿残渣,变得越来越容易获得。基于Cr同位素组成的差异,本研究证明δ53Cr可用于环境研究以示踪Cr浸出。随着它从土壤剖面移动到矿石和采矿残渣,变得越来越容易获得。基于Cr同位素组成的差异,本研究证明δ53Cr可用于环境研究以示踪Cr浸出。
更新日期:2021-02-01
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