[Mechanism and Environmental Effect on Nitrogen Addition to Microbial Process of Arsenic Immobilization in Flooding Paddy Soils].

Abstract

China is one of the largest rice producers in the world, and rice production plays an important role in food security. Currently, arsenic pollution in paddy soils is one of most serious soil pollutions in China. Since paddy soils are maintained in a flooding anoxic condition for long periods, the rate and extent of arsenic transformation processes governed by microbial activities are stronger than that of chemical processes. Thus, understanding the key processes and relating mechanisms of microbial arsenic fixation in paddy soils will provide a theoretical basis for controlling arsenic pollution in paddy soils. In this study, based on a comprehensive analysis of arsenic migration in paddy soils and relating influencing factors, two important pathways relating to As(Ⅲ) fixation through microbial activities were illustrated:microbial ČFe(Ⅱ) oxidation coupled with As(Ⅲ) fixation (indirect process) and direct fixation through microbial As(Ⅲ) oxidation (direct process). Additionally, the influences of speciation and the distribution of nitrogen in paddy soils to the processes of microbial arsenic fixations were discussed and by extension, the expressions of key genes and metabolic mechanisms relating to microbial arsenic fixation and nitrogen transformation. Finally, the recent advances in microbial remediation used to control arsenic pollution in paddy soils were summarized, and relating future perspectives targeting microbial remediation were proposed.