Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 128 43, Prague 2, Czech Republic.
Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, 128 43, Prague 2, Czech Republic.
Chemosphere. 2021 Aug;277:130306. doi: 10.1016/j.chemosphere.2021.130306. Epub 2021 Mar 17.
In this study, two Czech wetland soils enriched in authigenic sulfide minerals (especially realgar) were collected from the saturated zone (60-100 cm), flooded with local groundwater and allowed to dry for up to 98 days. The objective was to examine the mobility of As, Fe, S and trace metals using selective chemical extractions, S isotopes and X-ray diffraction through the drying process. During the initial stage of incubation (∼20 days), the re-flooding of the soils triggered a microbially-mediated SO reduction, which immobilized the Co, Cu and Ni. The reductive dissolution of As-bearing Fe (oxyhydr)oxides and the release of As were documented only in the Fe-rich/organic-low soil. Over the next stage of incubation (∼75 days), the exposure and drying of the soils led to the oxidation of the Fe and As sulfides. The arsenic and trace metals released via oxidation of the sulfide phases (particularly Fe sulfides) were almost entirely sequestered by the Fe(III) (oxyhydr)oxides, but acidification during the oxidation stage of the incubation resulted in the pH-dependent release of the As and trace metals (Co, Cu, Ni) (especially in the Fe-rich/organic-low soil). These findings suggest that sulfidic soils in wetlands can be considered as long-term sources of As during major drought events.
在这项研究中，从饱和区（60-100 厘米）采集了两份富含自生硫化物矿物（尤其是雄黄）的捷克湿地土壤，并用当地地下水淹没并允许干燥长达 98 天。目的是通过干燥过程中的选择性化学提取、S 同位素和 X 射线衍射来研究 As、Fe、S 和痕量金属的迁移性。在最初的孵育阶段（约 20 天），土壤的重新淹没引发了微生物介导的 SO 还原，从而固定了 Co、Cu 和 Ni。仅在富铁/低有机质土壤中记录了含 As 的 Fe（氢氧化物）氧化物的还原溶解和 As 的释放。在接下来的孵育阶段（约 75 天），土壤的暴露和干燥导致 Fe 和 As 硫化物的氧化。通过硫化物相（特别是 Fe 硫化物）氧化释放的砷和痕量金属几乎完全被 Fe(III)（氢氧化物）氧化物固定，但在孵育氧化阶段的酸化导致 pH 依赖性释放 As 和痕量金属（Co、Cu、Ni）（特别是在富铁/低有机质土壤中）。这些发现表明，湿地中的硫化土壤在主要干旱事件期间可以被视为 As 的长期来源。
