NSLS II XFM Beamline

Agricultural soil treated (historically) with arsenical herbicide for wetland rice production was characterized at various points over the growing season to monitor arsenic speciation under different field conditions (ie alternating wet and dry cycles).  During the dry season, soil at 25cm depth contained an abundance of micron-sized arsenopyrite (FeAsS) grains.  During the wet season (flooded), the soil arsenic speciation was dominated by secondary precipitates identified as As-bearing iron and manganese oxyhydroxides.  Alternating wet and dry conditions drive arsenic release via mineral dissolution but secondary precipitation as As-bearing Fe and Mn (oxy)hydroxides reduces As mobility in paddy soil.  Image and sample from Matthew Reid at Cornell.  

Maguffin, S. C., Abu-Ali, L., Tappero, R. V., Pena, J., Rohila, J. S., McClung, A. M., & Reid, M. C. (2020). Influence of manganese abundances on iron and arsenic solubility in rice paddy soils. Geochimica et Cosmochimica Acta, 276, 50-69.