Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400715, PR China.
Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR China.
J Hazard Mater. 2023 Oct 5;459:132213. doi: 10.1016/j.jhazmat.2023.132213. Epub 2023 Aug 5.
Sulfate-reducing bacteria (SRB) can immobilize heavy metals in soils through biomineralization, and the parent rock and minerals in the soil are critical to the immobilization efficiency of SRB. To date, there is little knowledge about the fate of Cd associated with the parent rocks and minerals of soil during Cd immobilized by SRB. In this study, we created a model system using clay-size fraction of soil and SRB to explore the role of SRB in immobilizing Cd in soils from stratigraphic successions with high geochemical background. In the system, clay-size fractions (particle size < 2 µm) with concentration of Cd (0.24-2.84 mg/kg) were extracted from soils for bacteria inoculation. After SRB reaction for 10 days, the Cd fraction tended to transform into iron-manganese bound. Further, two clay-size fractions, i.e., the non-crystalline iron oxide (Fe) and the crystalline iron oxide (Fe), were separated by extraction. The reaction of SRB with them verified the transformation of primary iron-bearing minerals into secondary iron-bearing minerals, which contributed to Cd redistribution. This study shows that SRB could exploit the composition and structure of minerals to induce mineral recrystallization, thereby aggravating Cd redistribution and immobilization in clay-size fractions from stratigraphic successions with high geochemical background.
硫酸盐还原菌 (SRB) 可以通过生物矿化作用将重金属固定在土壤中，而土壤中的母岩和矿物对 SRB 的固定效率至关重要。迄今为止，对于在 SRB 固定 Cd 期间与土壤母岩和矿物相关的 Cd 的归宿知之甚少。在这项研究中，我们使用土壤的粘土大小部分和 SRB 创建了一个模型系统，以探索 SRB 在固定具有高地球化学背景的地层土壤中的 Cd 方面的作用。在该系统中，从土壤中提取出含有 Cd（0.24-2.84mg/kg）的粘土大小部分（粒径<2μm）进行细菌接种。在 SRB 反应 10 天后，Cd 部分趋于转化为铁锰结合态。此外，通过提取将两种粘土大小部分，即无定形氧化铁 (Fe) 和结晶氧化铁 (Fe) 分离。SRB 与它们的反应验证了原生含铁矿物向次生含铁矿物的转化，这有助于 Cd 的重新分布。本研究表明，SRB 可以利用矿物的组成和结构来诱导矿物重结晶，从而加剧具有高地球化学背景的地层土壤中粘土大小部分中 Cd 的重新分布和固定。
