Microbial sulfate reduction decreases arsenic mobilization in flooded paddy soils with high potential for microbial Fe reduction.
Microbial sulfate reduction decreases arsenic mobilization in flooded paddy soils with high potential for microbial Fe reduction.
复制标题
DOI：
10.1016/j.envpol.2019.05.086
复制
发表时间：
2019-08
影响因子：
8.9
通讯作者：
Xiaowei Xu;Peng Wang;Jun Zhang;Chuan Chen;Ziping Wang;P. Kopittke;R. Kretzschmar;F. Zhao
中科院分区：
文献类型：
--
作者：
Xiaowei Xu;Peng Wang;Jun Zhang;Chuan Chen;Ziping Wang;P. Kopittke;R. Kretzschmar;F. Zhao
由于砷吸附的铁（羟基）氧化物的还原性溶解，砷（As）往往会在淹没的稻田土壤中移动，导致水稻中砷积累增加，对食品安全和人类健康构成潜在风险。微生物硫酸盐还原是水稻土中重要的生物地球化学过程，但其对砷动员的影响仍知之甚少。在这项研究中，我们在淹没条件下培养了八种受砷污染的水稻土，以研究硫酸盐添加对砷迁移率的影响。测定了孔隙水铁和砷的浓度以及砷的形态。在八种土壤中，添加 50mgS kg−1as 硫酸钠仅降低了两种土壤中的孔隙水亚砷酸盐，这也显示出较高的 Fe2+ 动员能力。进一步的实验表明，向这两种土壤添加硫酸盐刺激了微生物硫酸盐还原，但降低了孔隙水中亚砷酸盐和 Fe2+ 的浓度。此外，硫酸盐的供应增加了固相中与酸性挥发性硫化物相关的砷的分数，并在类似条件下的盆栽实验中减少了水稻对砷的吸收。添加硫酸盐对孔隙水砷的影响因添加钼酸盐（硫酸盐还原菌的抑制剂）而减弱。这些结果表明，共沉淀或吸附亚砷酸盐的次生 FeS 矿物的形成可能是砷固定的机制，这也得到了孔隙水热力学模型的支持。因此，硫酸盐的添加可以固定砷并减少其对稻田土壤中水稻植物的利用率，该土壤具有很高的微生物铁还原潜力，从而提供了一种有效的方法来减轻砷向食物链的转移。
Arsenic (As) tends to mobilize in flooded paddy soil due to the reductive dissolution of the iron (oxyhydr)oxides to which As sorbs, resulting in elevated As accumulation in rice that poses a potential risk to the food safety and human health. Microbial sulfate reduction is an important biogeochemical process in paddy soils, but its impact on As mobilization remains poorly understood. In this study, we incubated eight As-contaminated paddy soils under flooded conditions to investigate the effect of sulfate addition on As mobility. Porewater Fe and As concentrations and As species were determined. Among the eight soils, an addition of 50 mg S kg−1as sodium sulfate decreased porewater arsenite only in two soils, which also showed a high mobilization of Fe2+. Further experiments showed that the addition of sulfate to these two soils stimulated microbial sulfate reduction but decreased porewater concentrations of both arsenite and Fe2+. Additionally, the supply of sulfate increased the fractions of As associated with acid volatile sulfides in the solid phase and decreased As uptake by rice in pot experiments under similar conditions. The effect of sulfate addition on porewater As was diminished by the addition of molybdate, an inhibitor of sulfate reducing bacteria. These results suggest the formation of secondary FeS minerals which co-precipitate or sorb arsenite as a likely mechanism of As immobilization, which was also supported by thermodynamic modeling of the pore water. Thus, sulfate additions can immobilize As and reduce its availability to rice plants in paddy soils containing a high potential for microbial Fe reduction, providing an efficient way to mitigate the As transfer to the food chain.