Assessing the efficacy of phosphate and lime amendments in immobilizing three forms of lead in contaminated soil: An in vivo study on C57/BL6 mice simulating environmentally realistic exposure pathways.

Lead (Pb) bioavailability differs depending on the specific Pb species present in the area. Adding organic and inorganic soil amendments can ameliorate the mobility of Pb in the soil. However, there is a scarcity of in vivo studies investigating the impact of these amendments on mammals via environmentally realistic exposure pathways. We evaluated the accumulation of Pb in blood and tissues of mice living on soils spiked with one of three Pb species (hydrocerussite [2PbCO3·Pb(OH)2], lead sulfate [PbSO4], and lead sulfide [PbS]) and compared the efficacy of phosphate (triple super phosphate [TSP] or phosphoric acid) or liming (calcined dolomite) amendments in reducing Pb accumulation from these soils via realistic exposure pathways. The Pb species in the spiked soil were investigated via X-ray absorption near edge structures (XANES) spectroscopy. C57/BL6 mice (six per group) were exposed to both Pb-spiked and amended soils by housing them on the soil for three months and thus simulating realistic exposure pathways. XANES analysis revealed that Pb carbonates were the dominant phase in all Pb-spiked soils. The group exposed to 2PbCO3·Pb(OH)2 had the greatest Pb accumulation in brain, trachea, kidneys, liver, bone, and blood, but not lungs, whereas the PbS-exposed group accumulated more Pb in the lungs. TSP was the most effective chemical stabilizer of the three amendments, facilitating reductions in the 2PbCO3·Pb(OH)2, PbSO4, and PbS exposure groups of 68-88%, 44-62%, and 6-49%, respectively. This suggests that chemical remediation using phosphate sources may be effective for immobilizing various Pb species in soils.