Antimony release and volatilization from organic-rich and iron-rich submerged soils
Jaime N. Caplette, Susan Wilson, Adrien Mestrot
Abstract
Antimony (Sb) is an poorly understood, increasingly common pollutant, especially in soils susceptible to waterlogging. We investigated the impact of waterlogging on Sb release, methylation, and volatilization from an organic-rich wetland soil and an iron (Fe)-rich floodplain soil in a 27-day microcosm experiment. The release of Sb into the porewaters of the organic-rich soil was environmentally relevant and immediate with waterlogging (3.2 to 3.5 mg L-1), and likely associated with a complex interplay of sulfide precipitation, sorption with organic matter and manganese (Mn) (oxyhydr)oxides in the soil. The release of Sb from the Fe-rich soil was likely associated with Fe-(oxyhydr)oxide reduction and immobilized due to co-precipitation with Fe-sulfides or as Sb-sulfides. Volatile Sb was produced from the soils after waterlogging. The organic-rich soil produced more volatile Sb (409 to 835 ng kgsoil-1), but the Fe-rich soil volatilized Sb more efficiently. The negligible association of Sb volatilization with soil parameters indicates a more complex underlying, potentially microbial, mechanism and that antimony volatilization could be ubiquitous and not dependent on specific soil properties. Future works should investigate the microbial and physiochemical drivers of Sb volatilization in soils as it may be an environmentally relevant part of the biogeochemical cycle. Antimony (Sb) is a ubiquitous, but toxic, contaminant. The fate of Sb in anoxic, waterlogged environments is poorly understood and even less studied are the microbial-mediated transformations of Sb (e.g., methylation and volatilization) although some species are hazardous to human health. The release mechanisms of Sb from the solid to aqueous-phase, and transfer to the atmosphere (volatilization) is largely unknown and understudied but may introduce Sb into the atmosphere and in turn impact its biogeochemical cycle. Investigating the release of Sb and subsequent transformations of Sb in the aqueous and gaseous forms is addressed in this manuscript and is of high importance to better understand the fate and cycling of Sb in the environment.