CAS Key Laboratory of Mineralogy and Metallogeny & Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, 510640, Guangzhou, China; CAS Center for Excellence in Deep Earth Science, 511 Kehua Street, 510640, Guangzhou, China; University of Chinese Academy of Science, 19 Yuquan Road, 100049, Beijing, China.
CAS Key Laboratory of Mineralogy and Metallogeny & Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 511 Kehua Street, 510640, Guangzhou, China; CAS Center for Excellence in Deep Earth Science, 511 Kehua Street, 510640, Guangzhou, China.
Environ Pollut. 2023 Jan 1;316(Pt 1):120491. doi: 10.1016/j.envpol.2022.120491. Epub 2022 Oct 22.
Carbonate-bound speciation is a critical sink of potentially toxic elements (PTEs) like cadmium (Cd) in soil and sediment. In a phosphate-rich environment, carbonate minerals could be replaced by phosphate minerals such as dicalcium phosphate dihydrate (DCPD, also known as brushite), octacalcium phosphate (OCP), and hydroxylapatite (HAP). Currently, it is unclear the migration and fate of PTEs during the replacement of PTEs-bearing carbonates by HAP and related intermediate minerals. Therefore, we synthesized Cd-bearing calcite by the coprecipitation method and converted it to DCPD, OCP, and HAP to investigate the redistribution and fate of Cd. The results showed that Cd incorporation in calcite significantly inhibited their replacement by DCPD and OCP, respectively. 1.26% of Cd in calcite was released into the solution when DCPD replaced calcite, and subsequently, most of the released Cd was recaptured by OCP. Significantly, the released Cd was below 0.05‰ when all the solid converted to HAP. These results suggested that with the application of phosphate fertilizer in alkaline soil, the secondary calcium phosphate minerals could control the environmental behavior of Cd.
碳酸盐结合态是土壤和沉积物中潜在有毒元素（PTEs）如镉（Cd）的重要汇。在富含磷酸盐的环境中，碳酸盐矿物可能被磷酸盐矿物如二水磷酸二钙（DCPD，也称为透钙磷石）、八水磷酸钙（OCP）和羟基磷灰石（HAP）所取代。目前，尚不清楚在 HAP 和相关中间矿物取代含 PTEs 的碳酸盐时，PTEs 的迁移和归宿。因此，我们通过共沉淀法合成了含 Cd 的方解石，并将其转化为 DCPD、OCP 和 HAP，以研究 Cd 的再分布和归宿。结果表明，Cd 在方解石中的掺入显著抑制了它们分别被 DCPD 和 OCP 的取代。当 DCPD 取代方解石时，方解石中有 1.26%的 Cd 释放到溶液中，随后大部分释放的 Cd 被 OCP 重新捕获。值得注意的是，当所有固体转化为 HAP 时，释放的 Cd 低于 0.05‰。这些结果表明，在碱性土壤中施用磷肥时，次生磷酸钙矿物可以控制 Cd 的环境行为。
