Lead transformation to plumbojarosite remains stable following lime addition for lead and arsenic contaminated soils

Lead (Pb) is a highly toxic element that remains sequestered in soils long after deposition. Despite the environmental recalcitrance of soil Pb, acidic gastric conditions may promote solubilization of soil Pb following incidental ingestion. Potassium jarosite (KJ) based remediation is a promising in situ chemical remediation technique which can reduce bioaccessible soil Pb to 5.8 - 18.2% via conversion to an acid-stable mineral: plumbojarosite (PLJ). Treatment effectiveness is markedly greater than current alternatives (e.g., phosphate); however, KJ-treatment acidifies the soil. Lime addition is necessary to reestablish vegetative cover and promote future land use. Jarosite family minerals may destablize at pH > 4, necessitating stability investigations of newly formed jarosite phases post-lime. Therefore, we performed stability experiments at simulated field conditions for 6 weeks to assess jarosite-based remediation efficacy at environmentally nominal pH conditions. Smelter-impacted and legacy pesticide (lead arsenate) contaminated soils (SM and LP, respectively) were evaluated. Soils were adjusted to a range of pH conditions using either CaCO3 or Ca(OH)2 to faciliate growth of common U.S. grasses - centipede and perennial ryegrass. Grass growth occurred in limed samples from pH 4.3 - 8.6 with XAS-confirmed PLJ stability over a six-week period. Lead in vitro bioaccessibility (IVBA)% results for all treated soils were consistent with PLJ formation, showing averaged reductions of 77.3-8.0% and 81.6-11.0% post treatment in LP and SM soils, respectively, with a reduction in As IVBA% across all soils. Successful treatment at environmentally-applicable conditions lays the groundwork for low cost Superfund cleanup efforts of Pb/As contaminated residential sites.