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Jarosite-based remediation of Pb/As contaminated soils: Assessing the potential for grass growth and long-term efficacy (2023 SSSA conference)
Citation:
Blackmon, M., T. Sowers, M. Jerden, AND K. Bradham. Jarosite-based remediation of Pb/As contaminated soils: Assessing the potential for grass growth and long-term efficacy (2023 SSSA conference). 2023 ASA, CSSA, SSSA International Annual Meeting, St. Louis, MO, October 29 - November 01, 2023.
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. In continuance of these remediation techniques, we are testing the long-term efficacy and stability of plumbojarosite formation in the presence of liming and grass growing operations, which aim to increase the viability of jarosite-based remediation technologies at residential sites. 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) is a pervasive environmental contaminant commonly sourced from anthropogenic activities such as smelting, lead-based paint, and exhausted leaded gasoline. Soils in residential neighborhoods are of particular concern as soil Pb may cause significant adverse health effects in children (<5 yrs). Generally, removal of contaminated soil and replacement with ‘clean’, low Pb concentration, soil is implemented; however, this process is costly and is not feasible for all contaminated sites. We have recently developed an in situ chemical remediation technology to decrease soil Pb exposure without the need for excavation. Soil Pb can be converted to a highly insoluble Pb-mineral species plumbojarosite (PLJ), greatly reducing Pb relative bioavailability (>90%). However, this treatment process results in significant soil acidification that necessitates further evaluation of post-remediation soil treatments. To assess soil viability, we are conducting grass growth and liming experiments that will allow for nominal soil pH conditions without destabilization of newly-synthesized PLJ. Currently, two soils of variable Pb/As source and concentration have been successfully treated and are being used for vegetation experiments. Centipede and perennial ryegrass are serving as the vegetation parameter, as they are wide-ranging residential grasses that may be tolerant at acidic soil conditions. Potted soil experiments will be subsampled weekly for multiple months, with total element concentrations in soil and vegetation being assessed. Soils will be evaluated for bioaccessibility via an in vitro assay (EPA Method 1340) and plant and soil Pb and/or As speciation will be determined via X-ray absorption spectroscopy. Results will provide insight into PLJ stability in pH-adjusted soils, transfer factors from soils to vegetation, and the potential for grass growth post-treatment.
