Arsenic is a poisonous heavy metal that seriously threat human healthy widely distributed in water and soil environment. The speciation of arsenic is crucial for its environmental behavior and biologic availability. Deep understanding in soil arsenic speciation helps further searching the migration， transformation and redistribution of arsenic and providing means for rational soil remediation. The process of sulfate microbial reduction has significant effect on speciation change and interface behavior of arsenic. However, knowledge in the arsenic speciation and redistribution in such complex system is still scarce.

Associate prof XU Liying and others in the Environmental Molecular Research Group of IAE took arsenic-polluted paddy field in Zhangshi irrigated area in Shenyang as subject, investigated the effect of microbial sulfide-genesis on the process of migration, transformation and redistribution of arsenic under anaerobic conditions. Sulfate was added into the incubation system, the solid product produced in the transformation process was extracted and synchrotron radiation characterization was made. The results showed that iron oxides in soil were transformed into ferrous sulfide and precipitated but not released in liquid phase. On the primary phase, arsenate released into liquid phase and reduced to trivalent arsenic (As III) and then re-sequestered into solid phase. After excess sulfide was generated, the arsenic in solid phase was re-released into liquid phase as thio-arsenite. At the end of incubation, the arsenic in liquid phase entered the crystal lattice of iron sulfate or iron oxide and so held in the solid phase. The results provide some guidance to understand the migration and transformation of arsenic in soils with high sulfate concentration.

The work was supported by NNSFC (41273333, 41531043, 41173119). The results were published in Journal of Hazardous Materials（2016, 301: 538–546, DOI: 10.1016/j.jhazmat.2015.09.030）entitled as Speciation change and redistribution of arsenic in soil under anaerobic microbial activities