The release of cadmium during the natural weathering process of cadmium-containing strata is a significant source of cadmium pollution in both water and soil. The Hetang formations, wildly located in Jiangxi Province Zhejiang Province and Anhui Province in China, is a typical example of a cadmium-rich black shale stratum and is one of the primary sources of soil cadmium contamination. The bottom coal seam of this formation has been found to contain high levels of cadmium, with concentrations up to 11.26 mg/kg. As a result of water flow eroding the riverbed, parent rocks containing cadmium undergo continuous weathering, releasing cadmium elements. This process contributes to cadmium pollution in downstream soil, originating from the geological background. By utilizing techniques such as FE-SEM, EDS, and optical microscopy, this study investigates the distribution of iron in rock fragments with varying degrees of weathering in the riverbed. The research aims to examine the influence of iron distribution on the migration of cadmium originating from geological background sources. Based on the co-occurrence and co-migration characteristics of iron and cadmium in the study area, this research aims to reveal the migration features of geological background source cadmium by exploring the distribution patterns of iron sediment within rock fragments. By comparing sediment samples from both upstream and downstream river channels, we were able to identify three distinct stages that indicate the presence of cadmium originating from geological sources under weathering conditions: the unweathered stage; the intra-detritus migration stage, and the completely weathered stage; intra-detritus migration stage; and completely weathered stage. Furthermore, after leaving the Hetang formations shale outcrop area, there was a sharp decrease in content for Hetang formations detritus. At this point geological background source cadmium had largely escaped from constraints imposed by rock microstructure and had come into full contact with water. The findings from this research deepen our understanding regarding migration patterns for geological background source cadmium. They also reveal formation processes for geological background source cadmium pollution and provide a theoretical basis for identification and treatment for geological background source cadmium pollution.

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浙江省地质背景源镉迁移相分类研究

含镉地层自然风化过程中镉的释放是水和土壤镉污染的重要来源。荷塘组广泛分布于我国江西、浙江、安徽等地，是富镉黑色页岩地层的典型，是土壤镉污染的主要来源之一。该地层底部煤层被发现镉含量较高，浓度高达11.26 mg/kg。由于水流侵蚀河床，含镉母岩不断风化，释放出镉元素。这一过程导致了下游土壤中源于地质背景的镉污染。本研究利用 FE-SEM、EDS 和光学显微镜等技术，研究了河床不同风化程度的岩石碎片中铁的分布。该研究旨在探讨铁的分布对地质背景来源的镉迁移的影响。基于研究区铁、镉的共生和共运移特征，本研究旨在通过探究岩屑中铁沉积物的分布规律，揭示地质背景源镉的运移特征。通过比较上游和下游河道的沉积物样本，我们能够确定三个不同的阶段，表明在风化条件下存在来自地质来源的镉：未风化阶段；碎屑内运移阶段、完全风化阶段；碎屑内迁移阶段；和完全风化阶段。此外，离开荷塘组页岩露头区后，荷塘组碎屑含量急剧下降。此时，地质背景源镉已基本摆脱岩石微观结构的限制，并与水充分接触。这项研究的结果加深​​了我们对地质背景源镉迁移模式的理解。揭示了地质背景源镉污染的形成过程，为地质背景源镉污染的识别和治理提供了理论依据。