School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China.
South China Institute of Environmental Sciences, Ministry of Ecology and Environment of the People's Republic of China, Guangzhou 510535, China.
Sci Total Environ. 2024 Oct 10;946:174275. doi: 10.1016/j.scitotenv.2024.174275. Epub 2024 Jun 25.
Schwertmannite (Sch) is found in environments abundant in iron and sulfate. Microorganisms that utilize iron or sulfate can induce the phase transition of Schwertmannite, consequently leading to the redistribution of coexisting pollutants. However, the impact of the molar ratio of sulfate to iron (S/Fe) on the microbial-mediated transformation of Schwertmannite and its implications for the fate of cadmium (Cd) have not been elucidated. In this study, we examined how S/Fe influenced mineral transformation and the fate of Cd during microbial reduction of Cd-loaded Schwertmannite by Desulfovibrio vulgaris. Our findings revealed that an increase in the S/Fe ratio facilitated sulfate-reducing bacteria (SRB) in mitigating the toxicity of Cd, thereby expediting the generation of sulfide (S(-II)) and subsequently triggering mineral phase transformation. As the S/Fe ratio increased, the predominant minerals in the system transitioned from prismatic-cluster vivianite to rose-shaped mackinawite. The Cd phase and distribution underwent corresponding alterations. Cd primarily existed in its oxidizable state, with its distribution being directly linked not only to FeS content but also showing a robust correlation with phosphorus. The coexistence of vivianite and FeS minerals proved to be more favorable for Cd immobilization. These findings have significant implications for understanding the biogeochemistry of iron (oxyhydr)oxides and Cd fate in anaerobic environments.
纤铁矿（Sch）存在于富含铁和硫酸盐的环境中。利用铁或硫酸盐的微生物可以诱导纤铁矿的相转变，从而导致共存污染物的重新分布。然而，硫酸盐与铁的摩尔比（S/Fe）对微生物介导的纤铁矿转化及其对镉（Cd）命运的影响尚未阐明。在这项研究中，我们研究了 S/Fe 如何影响微生物还原 Cd 负载的纤铁矿过程中矿物转化和 Cd 的命运。我们的研究结果表明，增加 S/Fe 比有利于硫酸盐还原菌（SRB）减轻 Cd 的毒性，从而加速硫化物（S(-II)）的生成，进而引发矿物相转变。随着 S/Fe 比的增加，体系中的主要矿物从棱柱簇磷铁矾转变为玫瑰形的磁黄铁矿。Cd 相和分布也发生了相应的变化。Cd 主要以其可氧化态存在，其分布不仅直接与 FeS 含量有关，而且与磷之间存在很强的相关性。磷铁矾和 FeS 矿物的共存被证明更有利于 Cd 的固定。这些发现对于理解铁（氧）氢氧化物的生物地球化学和厌氧环境中 Cd 命运具有重要意义。
