土壤-水稻系统砷的生物地球化学过程研究进展

Arsenic biogeochemical processing in the soil–rice system

本文综述了具有不同渗氧能力基因型水稻对土壤砷结合形态、水稻根表铁膜、砷吸收的影响以及不同根际氧化还原条件对土壤砷形态、水稻砷积累、砷转运载体表达的影响,分析了硅的不同施加量对水稻砷吸收的研究进展及其作用机制,从土壤铁矿物氧化和还原两个方面总结了根际铁循环对砷环境行为的影响以及对砷污染土壤修复的潜在价值,以期为最终降低水稻砷吸收提供理论参考。微生物介导的铁氧化还原对砷的环境行为如砷的溶解释放、吸附沉淀、形态转化等有重要影响,而铁细菌的胞外电子传递过程促进了铁的矿物相转化并耦合砷的钝化,在未来工作中值得进一步关注和研究。

Arsenic(As)contamination of paddy soils in south China has received increasing attention, as it has caused severe rice contamination and negatively affects the health of millions of people who rely on rice as a staple food. The As biogeochemical process in soil contributes critically in the control of As contamination. In this article, the mechanism of As uptake and translocation in the soil–plant system has been summarized. In addition, the effect of radial oxygen loss(ROL)of different rice genotypes on As fractionation in soil, Fe plaque formation, and As accumulation in rice and the effect of water management on As speciation in soil, As uptake, and expression of As transporters in rice have been systematically reviewed. Rice genotypes with high ROL formed extra Fe plaque on roots, which reduced As uptake in rice. Compared with continuous flooding, water management with intermittent flooding and aerobic soil conditions significantly reduced As uptake and accumulation in rice. Moreover, the effect of Si application to soil on As uptake in rice and related mechanisms were examined, with the Si/As ratio in soils the major factor controlling the As uptake in rice. In addition, the effect of Fe redox processes on As biogeochemical behaviors were studied. The microorganism-mediated Fe redox reaction had significant influence on As behaviors such as dissolution, release, adsorption, coprecipitation, and speciation. Moreover, the extracellular electron transfer process of Fe oxidation and reduction bacteria significantly impacted the transformation of Fe minerals and related As immobilization in soils, which deserves further attention in future research.