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| - Linking Solid Phase Speciation of Pb Sequestered to Birnessite to Oral Pb Bioaccessibility: Implications for Soil Remediation
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| - Speciation and bioaccessibility of Pb sorbed to birnessite using EXAFS is examined and the possible use of birnessite as a remediation tool is explored.
- Lead (Pb) sorption onto oxide surfaces in soils may strongly influence the risk posed from incidental ingestion of lead-contaminated soils. In this study, Pb was sorbed to a model soil mineral, birnessite, and was placed in a simulated gastrointestinal tract (in vitro) to simulate the possible effects of ingestion of a soil contaminated with Pb. The changes in Pb speciation were determined using extended X-ray absorption fine structure and X-ray absorption near edge spectroscopy. Birnessite has a very high affinity for Pb with a sorption maximum of 0.59 mol Pb kg−1 (approximately 12% Pb sorbed by mass) in which there was no detectable bioaccessible Pb (<0.002%). Surface speciation of the birnessite Pb was determined to be a triple corner sharing complex in the birnessite interlayer. Lead sorbed to Mn oxide in contaminated media will have a very low (≈ 0) Pb bioaccessibility and present little risk associated with incidental ingestion of soil. These results suggest that birnessite, and other Mn oxides would be powerful remediation tools for Pb-contaminated media because of their high affinity for Pb.
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