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Extracellular polymeric substances altered ferrihydrite (trans)formation and induced arsenic mobilization
Journal of Hazardous Materials ( IF 12.2 ) Pub Date : 2024-05-10 , DOI: 10.1016/j.jhazmat.2024.134434 Kun Gao 1 , Shuai Wang 1 , Wenjing Zhou 1 , Bowei Zhang 1 , Zhi Dang 2 , Chongxuan Liu 1
Journal of Hazardous Materials ( IF 12.2 ) Pub Date : 2024-05-10 , DOI: 10.1016/j.jhazmat.2024.134434 Kun Gao 1 , Shuai Wang 1 , Wenjing Zhou 1 , Bowei Zhang 1 , Zhi Dang 2 , Chongxuan Liu 1
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The behavior of As is closely related to trans(formation) of ferrihydrite, which often coprecipitates with extracellular polymeric substances (EPS), forming EPS-mineral aggregates in natural environments. While the effect of EPS on ferrihydrite properity, mineralogy reductive transformation, and associated As fate in sulfate-reducing bacteria (SRB)-rich environments remains unclear. In this research, ferrihydrite-EPS aggregates were synthesized and batch experiments combined with spectroscopic, microscopic, and geochemical analyses were conducted to address these knowledge gaps. Results indicated that EPS blocked micropores in ferrihydrite, and altered mineral surface area and susceptibility. Although EPS enhanced Fe(III) reduction, it retarded ferrihydrite transformation to magnetite by inhibiting Fe atom exchange in systems with low SO. As a result, 16% of the ferrihydrite was converted into magnetite in the Fh-0.3 treatment, and no ferrihydrite transformation occurred in the Fh-EPS-0.3 treatment. In systems with high SO, however, EPS promoted mackinawite formation and increased As mobilization into the solution. Additionally, the coprecipitated EPS facilitated As(V) reduction to more mobilized As(III) and decreased conversion of As into the residual phase, enhancing the potential risk of As contamination. These findings advance our understanding on biogeochemistry of elements Fe, S, and As and are helpful for accurate prediction of As behavior.
中文翻译：
细胞外聚合物改变水铁矿（转）形成并诱导砷动员
As 的行为与水铁矿的转化（形成）密切相关，水铁矿经常与细胞外聚合物（EPS）共沉淀，在自然环境中形成 EPS 矿物聚集体。然而，EPS 对水铁矿性质、矿物学还原转化以及富含硫酸盐还原菌 (SRB) 环境中相关砷命运的影响仍不清楚。在本研究中，合成了水铁矿-EPS 聚集体，并进行了与光谱、显微镜和地球化学分析相结合的批量实验，以解决这些知识空白。结果表明，EPS 堵塞了水铁矿中的微孔，并改变了矿物表面积和磁化率。虽然 EPS 增强了 Fe(III) 的还原，但它通过抑制低 SO 体系中的 Fe 原子交换来延迟水铁矿向磁铁矿的转化。结果，在Fh-0.3处理中，16%的水铁矿转化为磁铁矿，而在Fh-EPS-0.3处理中没有发生水铁矿转化。然而，在具有高 SO 的系统中，EPS 促进了 Mackinawite 的形成并增加了 As 向溶液中的迁移。此外，共沉淀的 EPS 促进 As(V) 还原为更多流动的 As(III)，并减少 As 转化为残留相，从而增加了 As 污染的潜在风险。这些发现增进了我们对元素 Fe、S 和 As 生物地球化学的理解，有助于准确预测 As 行为。
更新日期：2024-05-10
中文翻译：
细胞外聚合物改变水铁矿（转）形成并诱导砷动员
As 的行为与水铁矿的转化（形成）密切相关，水铁矿经常与细胞外聚合物（EPS）共沉淀，在自然环境中形成 EPS 矿物聚集体。然而，EPS 对水铁矿性质、矿物学还原转化以及富含硫酸盐还原菌 (SRB) 环境中相关砷命运的影响仍不清楚。在本研究中，合成了水铁矿-EPS 聚集体，并进行了与光谱、显微镜和地球化学分析相结合的批量实验，以解决这些知识空白。结果表明，EPS 堵塞了水铁矿中的微孔，并改变了矿物表面积和磁化率。虽然 EPS 增强了 Fe(III) 的还原，但它通过抑制低 SO 体系中的 Fe 原子交换来延迟水铁矿向磁铁矿的转化。结果，在Fh-0.3处理中，16%的水铁矿转化为磁铁矿，而在Fh-EPS-0.3处理中没有发生水铁矿转化。然而，在具有高 SO 的系统中，EPS 促进了 Mackinawite 的形成并增加了 As 向溶液中的迁移。此外，共沉淀的 EPS 促进 As(V) 还原为更多流动的 As(III)，并减少 As 转化为残留相，从而增加了 As 污染的潜在风险。这些发现增进了我们对元素 Fe、S 和 As 生物地球化学的理解，有助于准确预测 As 行为。
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