In Situ Remediation of Arsenic in Topsoil: Evaluating the Effect of Soil Mineralogy on Ferrihydrite Encapsulation.

Surface soil with high concentration arsenic (As) poses a public health risk as a source of incidental dust ingestion or through translocation into groundwater used for drinking. Precipitation of ferrihydrite onto a contaminated soil is an in situ remediation technique with potential to reduce As transport and human exposure after dust ingestion. In this study, arsenate was adsorbed to surfaces of major soil minerals (e.g., goethite, birnessite, gibbsite), ferrihydrite precipitated and the residue air-dried. The residue was then tested for chemical stability by phosphate and in-vitro bioaccessibility (IVBA) extractions and for chemical form by As XAS and Fe XAS at the Advanced Photon Source. Results and environmental implications will be discussed.