Arsenic Methylation in Soils and Its Relationship with Microbial <i>arsM</i> Abundance and Diversity, and As Speciation in Rice

Methylation of arsenic in soil influences its environmental behavior and accumulation by plants, but little is known about the factors affecting As methylation. As speciation was determined in the pore waters of six soils from diverse geographical locations over 54 days of incubation under flooded conditions. The concentration of methylated As (monomethylarsonic acid, MMA, and dimethylarsinic acid, DMA) varied from 0 to 85 μg L(-1) (0 - 69% of the total As in pore water). Two Bangladeshi paddy soils contaminated by irrigation of As-laden groundwater produced large concentrations of inorganic As but relatively little methylated As. Two contaminated paddy soils from China produced a transient peak of DMA during the early phase of incubation. Methylated As represented considerable proportions of…