Beijing Normal University, Beijing, 100875, China.
Beijing Normal University, Beijing, 100875, China.
Chemosphere. 2022 Nov;307(Pt 4):136200. doi: 10.1016/j.chemosphere.2022.136200. Epub 2022 Aug 26.
Lability and bioaccessibility of anthropogenic toxic heavy metals in arid calcareous soils are critical to understand their ecological and health risks. This study examined toxic heavy metal speciation in the calcareous soil contaminated by nonferrous metal smelting. Results demonstrated that approximately 70 years' nonferrous metal smelting and mining in Baiyin led to significant contamination of nearby soil down to about 200 cm depth by cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), with more serious contamination in the downwind areas of smelting or mining. More than half of Cd, Cu, Pb, and Zn in the soil was present in the labile fractions while more than 75% of cobalt (Co), chromium (Cr), nickel (Ni), and vanadium (V) was present in the residual fraction. Carbonate minerals in this calcareous soil play an important role in the labile fractions, with approximate 25% of Cd and Pb and 15% of Cu and Zn bound in carbonates. Bioaccessible Cd, Cu, Pb, and Zn in the soil were approximately 49.8%, 29.4%, 12.2%, and 33.8% in gastric phase and 13.5%, 15.9%, 4.3%, and 9.1% in intestinal phase of their total concentrations, respectively. Therefore, Cd and Zn were removed from gastric solution to a greater extent than Cu and Pb by neutral intestine environment. However, bioaccessible Co, Cr, Ni, and V in the soil were less than 3% of their total concentrations. Bioaccessibility of these metals but Cu in this calcareous soil was significantly lower than that for the acidic Ultisols and Alfisols in U.S. The concentrations of Cd, Cu, Pb, Zn, and Ni in each chemical and bioaccessible forms were significantly correlated linearly with their total concentrations in the calcareous soil, while only residual concentration was significantly correlated with the total concentration for Co, Cr, and V. These linear slopes showed that relative lability and bioaccessibility increased for Cd, but decreased for Cu, Pb, and Zn with the increase in their total concentrations in the calcareous soil. Direct oral soil ingestion would not pose a non-carcinogenic health risk to local children. However, very high potential ecological risk would be caused by these metals in the soil. These results provide improved insights into the biogeochemical processes of anthropogenic toxic heavy metals in the arid calcareous soils worldwide.
人为有毒重金属在干旱钙质土壤中的活性和生物可给性对于理解其生态和健康风险至关重要。本研究考察了受有色金属冶炼污染的钙质土壤中有毒重金属的形态。结果表明，在过去的 70 年中，白银地区的有色金属冶炼和采矿活动导致附近土壤受到严重污染，污染深度约达 200cm，下风区的污染更为严重。土壤中约有一半的镉（Cd）、铜（Cu）、铅（Pb）和锌（Zn）以活性形态存在，钴（Co）、铬（Cr）、镍（Ni）和钒（V）的大部分以残渣态存在。该钙质土壤中的碳酸盐矿物对活性形态的重金属有重要的贡献，约有 25%的 Cd 和 Pb 以及 15%的 Cu 和 Zn 与碳酸盐结合。土壤中可生物利用的 Cd、Cu、Pb 和 Zn 分别占其总量的 49.8%、29.4%、12.2%和 33.8%（胃阶段）和 13.5%、15.9%、4.3%和 9.1%（肠阶段）。因此，中性肠环境下，Cd 和 Zn 比 Cu 和 Pb 更易从胃溶液中被去除。然而，土壤中可生物利用的 Co、Cr、Ni 和 V 不到其总量的 3%。与美国的酸性 Ultisols 和 Alfisols 相比，该钙质土壤中这些金属（但 Cu 除外）的生物可利用性显著降低。土壤中各化学形态和可生物利用形态的 Cd、Cu、Pb、Zn 和 Ni 浓度与土壤中总浓度呈显著线性相关，而 Co、Cr 和 V 仅与残渣态浓度显著相关。这些线性斜率表明，随着土壤中总浓度的增加，Cd 的相对活性和生物可利用性增加，而 Cu、Pb 和 Zn 的相对活性和生物可利用性降低。直接口服土壤不会对当地儿童造成非致癌健康风险。然而，土壤中这些金属将造成极高的潜在生态风险。这些结果为了解干旱钙质土壤中人为有毒重金属的生物地球化学过程提供了更深入的认识。
