Karst areas are formed from the dissolution of carbonate rocks and are present worldwide. The soil found in such areas is enriched in heavy metals, such as cadmium (Cd), lead (Pb) and Arsenic (As), and has geological high-background characteristics. However, this enrichment is anomalous depending on the type of bedrock, and the mechanism of enrichment has not yet been comprehensively elucidated. To explore the mechanisms of Cd enrichment in these soils, we investigated the distribution patterns and migration characteristics of Cd during the weathering and pedogenesis of carbonate rocks, and the causes of Cd enrichment and associated ecological risks were determined. The conclusions were as follows: (1) In the process of natural evolution, the boundary between the dissolution of carbonate rocks and the weathering of insoluble substances is unclear, resulting in the overlap of and interaction between the processes of dissolution-accumulation-weathering and pedogenesis. (2) In addition to the enrichment effects caused by the dissolution of carbonate rocks and the inheritance, the readsorption of insoluble substances and the retention of secondary carrier minerals are the main driving forces of Cd enrichment. (3) During the late stage of weathering of insoluble materials, soil acidification significantly promotes the Cd activation process. When the proportion of active Cd significantly increases, the ecological risk potential increases, especially in geological high-background areas rich in Cd.

中文翻译：

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西南地区高地球化学背景岩溶地区土壤中镉（Cd）富集的机理


喀斯特地区是由碳酸盐岩的溶解形成的，遍布世界各地。在这些地区发现的土壤富含重金属，如镉 （Cd）、铅 （Pb） 和砷 （As），并具有地质高本底特征。然而，根据基岩的类型，这种富集是异常的，并且富集机制尚未得到全面阐明。为探究这些土壤中 Cd 富集的机制，我们研究了碳酸盐岩风化和成因过程中 Cd 的分布模式和迁移特征，并确定了 Cd 富集的原因和相关生态风险。结论如下：（1）在自然演化过程中，碳酸盐岩的溶解与不溶性物质的风化界限不明确，导致溶出-积累-风化和土壤发生过程之间存在重叠和相互作用。（2）除了碳酸盐岩溶蚀和继承引起的富集效应外，不溶性物质的再吸附和次生载体矿物的保留是 Cd 富集的主要驱动力。（3）在不溶性物质风化后期，土壤酸化显著促进了Cd活化过程。当活性 Cd 比例显著增加时，生态风险潜能增加，尤其是在富含 Cd 的地质高背景地区。