Cadmium (Cd)-bearing sphalerite (SP, ZnS) and smithsonite (SM, ZnCO3) particulate matter (PM) is deposited on soils near carbonate-hosted Zn ore deposits. Whether and how carbonate rocks such as limestone influence the mobility of Cd and Zn in soils is largely unknown. For this reason, we conducted a soil incubation experiment to investigate the chemical and mineralogical changes in soil–soil solution samples, including the occurrence of Cd- and Zn-bearing colloids and nanoparticles. Here the addition of calcite to SP- and SM-spiked soils promoted the formation of Cd- and Zn- bearing nanoparticles and colloids and thus significantly decreased the concentrations of Cd and Zn in soil solutions. Transmission electron microscope and extended X-ray absorption fluorescence spectroscopy showed that the addition of calcite resulted in the formation of Fe-OM-Ca colloids (OM = organic matter), sequestrating Cd and Zn. Furthermore, the release of Ca2+ during the dissolution of calcite promoted the aggregation of colloids and thus decreased the mobility of Cd- and Zn-bearing colloids in the soil column. The addition of calcite also decreased the amount of Cd and Zn released from the dissolution of SP and SM through the formation of calcite nano-layers armoring particles of the SP and SM phases. This study provides new insights into the environmental fate of particulate Cd and Zn in soils around carbonate-hosted Pb-Zn ore deposits. Specifically, it shows that the formation and aggregation of Cd- and Zn-bearing colloids decrease the mobility and bioavailability of both elements.

中文翻译：

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胶体控制富含方解石的土壤中释放的锌和镉物种的移动


含镉 （Cd） 的闪锌矿 （SP， ZnS） 和史密森石 （SM， ZnCO3） 颗粒物 （PM） 沉积在碳酸盐岩赋存的 Zn 矿床附近的土壤上。石灰石等碳酸盐岩是否以及如何影响土壤中 Cd 和 Zn 的流动性在很大程度上是未知的。出于这个原因，我们进行了一项土壤孵育实验，以研究土壤-土壤溶液样品中的化学和矿物学变化，包括含 Cd 和 Zn 胶体和纳米颗粒的出现。在这里，向 SP 和 SM 加标土壤中添加方解石促进了含 Cd 和 Zn 的纳米颗粒和胶体的形成，从而显着降低了土壤溶液中 Cd 和 Zn 的浓度。透射电子显微镜和扩展 X 射线吸收荧光光谱表明，方解石的添加导致 Fe-OM-Ca 胶体（OM = 有机物）的形成，螯合 Cd 和 Zn。此外，方解石溶解过程中 Ca2+ 的释放促进了胶体的聚集，从而降低了含 Cd 和 Zn 胶体在土柱中的迁移率。方解石的添加还通过形成 SP 和 SM 相的方解石纳米层铠装颗粒，减少了 SP 和 SM 溶解释放的 Cd 和 Zn 的量。这项研究为碳酸盐岩型 Pb-Zn 矿床周围土壤中颗粒 Cd 和 Zn 的环境归宿提供了新的见解。具体来说，它表明含 Cd 和 Zn 胶体的形成和聚集降低了这两种元素的迁移率和生物利用度。