The environmental risk of Cd in soils strongly depends on the mobilization of Cd in soils. However, limited knowledge exists on the redistribution of exogenic Cd inputs in soils, especially across diverse lithological regions. Herein, we aimed to investigate the fate of Cd in soils from two mining areas with contrasting lithologies (siliceous and calcareous) using stable Cd isotopes. The isotope tracing results confirm that mining activities are the main Cd source in both areas. The positive correlation between δ114/110Cd values and goethite/dolomite content indicates the release of heavy Cd isotopes during the dissolution of exogenetic minerals. Additionally, high contents of exchangeable Cd (11 % to 36 %) and Fe oxide-bound Cd (29 % to 42 %) drive plant pumps to transport heavy Cd isotopes from the deeper to upper horizons of the soils from the siliceous area. In the calcareous area, the total organic carbon content is positively correlated with the Cd concentration and δ114/110Cd value, suggesting potential complexation of Cd with organic matter due to the stabilizing effect of carbonate minerals on soil organic matter. This study highlights the different redistributions of exogenous Cd in soils from diverse lithological regions, emphasizing the need to consider regional lithology when developing soil quality standards for Cd.

中文翻译：

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不同基岩岩性受采矿影响土壤中的 Cd 移动：来自稳定 Cd 同位素的见解


土壤中 Cd 的环境风险在很大程度上取决于土壤中 Cd 的移动。然而，关于土壤中外生 Cd 输入的再分配知识有限，尤其是在不同的岩性区域。在此，我们旨在使用稳定的 Cd 同位素研究两个岩性对比鲜明的矿区（硅质和钙质）土壤中 Cd 的命运。同位素示踪结果证实，采矿活动是这两个地区的主要 Cd 来源。δ114/110Cd 值与针铁矿/白云石含量呈正相关，表明外生矿物溶解过程中释放了重 Cd 同位素。此外，高含量的可交换 Cd（11 % 至 36%）和氧化铁结合 Cd（29 % 至 42%）驱动植物泵将重 Cd 同位素从硅质区域从土壤的更深层输送到上层。在钙质区，总有机碳含量与 Cd 浓度和 δ114/110Cd 值呈正相关，表明碳酸盐矿物对土壤有机质的稳定作用可能导致 Cd 与有机质络合。本研究强调了不同岩性区域土壤中外源 Cd 的不同再分布，强调在制定 Cd 土壤质量标准时需要考虑区域岩性。