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Jarosite treatments promote significantly decreased bioavailability of Pb in soil: Visualizing soil lead remediation
Citation:
Sowers, T., Matthew (Matt) Blackmon, S. Bone, M. Noerpel, G. Diamond, D. Thomas, K. Scheckel, AND K. Bradham. Jarosite treatments promote significantly decreased bioavailability of Pb in soil: Visualizing soil lead remediation. 2022 ASA, CSSA & SSSA International Annual Meeting, Baltimore, MD, November 06 - 09, 2022.
Impact/Purpose:
We showcase the potential for K-jarosite to treat lead-contaminated soils to form plumbojarosite, a Pb mineral of very low bioavailability. This study confirms that plumbojarosite significantly decreased Pb relative bioavailability, making this an exceptionally promising remediation technology. A primary barrier to our early research involving plumbojarosite formation was high temperature requirements for the treatment to function (95-100°C); however, our newly developed K-jarosite method may be performed at room temperature conditions. These findings further ORD’s research on development of soil remediation technologies to reduce lead bioavailability at contaminated sites in support of EPA’s OLEM/OSRTI and Regional offices. ORD’s soil remediation research for lead contaminated soils is listed as a high priority research need for OLEM/OSRTI and EPA Regional offices.
Description:
Lead (Pb) contamination of soils is widespread in the United States and is an important source of Pb exposure in young children. Early life exposure to Pb has serious and long-lasting effects on health, making mitigation a critical public health goal. Removal/replacement of Pb-contaminated soils is often used to reduce exposure; however, this approach can be economically and logistically impractical. An alternative approach to reduce Pb exposure through ingestion of contaminated soil involves the conversion of soil Pb species into forms that are less likely to cross the gastrointestinal tract (GIT) barrier when ingested. Karna et al. (2021) recently developed a novel, heat-dependent Pb mineral precipitation technique that promotes formation of plumbojarosite (PLJ). Conversion of soil Pb to PLJ drastically reduces Pb relative bioavailability by >90%, decreasing the amount of ingested soil Pb that crosses the GIT barrier. However, this technique requires heat (95-100°C) to promote mineral transformation and questions remain as to how Pb and/or PLJ interact with elements as soil moves through the GIT. Here, we examined properties of pre- and post-treatment soils using heat-dependent PLJ precipitation methods and a newly developed K-jarosite application that is conducted at ambient temperature. Bulk and spatially-resolved X-ray absorption spectroscopy revealed that both treatments were effective at converting Pb-contaminated orchard soil to low bioaccessibility/bioavailability PLJ. Additionally, micro-XRF mapping of diet, cecum, and feces samples collected from mice after ingestion of diets containing pre- and post-jarosite treatment soils found that Pb phases changed during GIT transit. Notably, PLJ phases predominated in feces of mice that consumed diets amended with treated soils. These results suggest that jarosite-conversion techniques are a promising option for soil Pb remediation; however, further investigation applying these chemical techniques in field conditions is needed to assess long-term efficacy and suitability.
