Water contamination by geogenic hexavalent chromium is an emerging issue in areas developed on ultramafic rocks and their weathering products. In this study, samples of serpentinites, soil, and laterites were collected and analyzed for the levels of Cr species, distribution into phases of different mobility, mineralogy, Cr oxidation capacity, and leaching of Cr(VI). Total chromium (2176–21,929 mg kg⁻¹) was mainly found in Cr spinels (~ 50% wt as Cr₂O₃) and Fe (hydr)oxides (2.5% wt). Total Cr(VI) contents (0.49–11.5 mg kg⁻¹) increased from the serpentinites to the soil and lateritic deposit, i.e., during the advanced stages of weathering, which were accompanied by increased Cr mobility. Batch experiments of 500-h duration showed that Cr(VI) released in water at rates of 0.25–1.20 nM h^–1. Rates were higher in water of pH 5.7 rather than pH 8.5, because more Cr(VI) was formed during the experimental period. Asbolane-type Mn oxides and Mn-bearing crystalline Fe oxides were responsible for Cr(III) oxidation. Most of the generated Cr(VI) (52–79% of total Cr(VI)) remained solid-bound by adsorption and/or precipitation processes. Because all samples had a self-capacity to oxidize Cr(III), it seems that retention processes will ultimately define the extent of geogenic Cr(VI) contamination of aquatic systems.

地质六价铬对水的污染是超镁铁质岩石及其风化产物开发的地区的一个新问题。在这项研究中，收集并分析了蛇纹岩、土壤和红土样品的 Cr 物种水平、不同流动相的分布、矿物学、Cr 氧化能力和 Cr(VI) 的浸出。总铬（2176–21,929 mg kg ^-1）主要存在于 Cr 尖晶石（约 50% wt 作为 Cr ₂ O ₃）和 Fe（氢）氧化物（2.5% wt）中。总 Cr(VI) 含量 (0.49–11.5 mg kg ^-1 ) 从蛇纹岩到土壤和红土沉积物增加，即在风化的晚期阶段，伴随着铬迁移率的增加。500 小时的批量实验表明，Cr(VI) 在水中的释放速率为 0.25–1.20 nM h ^–1。在 pH 值 5.7 而不是 pH 值 8.5 的水中，速率更高，因为在实验期间形成了更多的 Cr(VI)。Asbolane 型 Mn 氧化物和含 Mn 结晶 Fe 氧化物是 Cr(III) 氧化的原因。大多数生成的 Cr(VI)（占总 Cr(VI) 的 52-79%）通过吸附和/或沉淀过程保持固结。由于所有样品都具有氧化 Cr(III) 的自身能力，因此保留过程似乎最终将确定水生系统的地源 Cr(VI) 污染程度。