School of Metallurgy and Environment, Central South University, Changsha, 410083, China.
School of Metallurgy and Environment, Central South University, Changsha, 410083, China.
Environ Pollut. 2020 May;260:114010. doi: 10.1016/j.envpol.2020.114010. Epub 2020 Jan 20.
The microbe-driven iron cycle plays an important role in speciation transformation and migration of arsenic (As) in soil-rice systems. In this study, pot experiments were used to investigate the effect of bacterial iron (Fe) reduction processes in soils on As speciation and migration, as well as on As uptake in soil-rice system. During the rice growth period, pH and electrical conductivity (EC) in soil solutions initially increased and then decreased, with the ranges of 7.4-8.8 and 116.3-820 mS cm, respectively. The concentrations of Fe, total As and As(III) showed an increasing trend in the rhizosphere and non-rhizosphere soil solutions with the increasing time. Fe concentrations were significantly positively correlated with total As and As(III) concentrations (***p < 0.001) in the soil solutions. The abundances of the arsenate reductase gene (arsC) and the As(III) S-adenosylmethionine methyltransferase gene (arsM) in rhizosphere soils were higher than those in non-rhizosphere soils, while the abundance of the Fe-reducing bacteria (Geo) showed an opposite trend. Moreover, it showed that the Geo abundance was significantly positively correlated with that of the arsC (***p < 0.001) and arsM (**p < 0.01) genes, respectively. The abundances of Geo, arsC and arsM genes were significantly positively correlated with the concentrations of Fe, total As and As(III) in the soil solutions (*p < 0.05). Moreover, the abundances of arsC and arsM genes were significantly negatively correlated with total As and As(III) in rice grains (*P < 0.05). These results showed that the interaction of bacterial Fe reduction process and radial oxygen loss from roots promoted the reduction and methylation of As, and then decreased As uptake by rice, which provided a theoretical basis for alleviating As pollution in paddy soils.
微生物驱动的铁循环在土壤-水稻系统中砷的形态转化和迁移中起着重要作用。本研究采用盆栽实验，研究了土壤中细菌铁还原过程对砷形态和迁移以及土壤-水稻系统中砷吸收的影响。在水稻生长期间，土壤溶液的 pH 值和电导率（EC）先升高后降低，范围分别为 7.4-8.8 和 116.3-820 mS cm。根际和非根际土壤溶液中 Fe、总 As 和 As(III) 的浓度随时间的增加呈增加趋势。土壤溶液中 Fe 浓度与总 As 和 As(III) 浓度呈显著正相关（***p < 0.001）。根际土壤中砷酸盐还原酶基因（arsC）和 As(III) S-腺苷甲硫氨酸甲基转移酶基因（arsM）的丰度高于非根际土壤，而 Fe 还原细菌（Geo）的丰度则呈现相反的趋势。此外，Geo 的丰度与 arsC（***p < 0.001）和 arsM（**p < 0.01）基因的丰度呈显著正相关。Geo、arsC 和 arsM 基因的丰度与土壤溶液中 Fe、总 As 和 As(III) 的浓度呈显著正相关（*p < 0.05）。此外，arsC 和 arsM 基因的丰度与水稻籽粒中总 As 和 As(III) 呈显著负相关（*P < 0.05）。这些结果表明，细菌铁还原过程与根际径向耗氧的相互作用促进了 As 的还原和甲基化，从而降低了水稻对 As 的吸收，为缓解稻田土壤 As 污染提供了理论依据。
