Restoration and Risk Reduction of Lead Mining Waste by Phosphate-Enriched Biosolid Amendments

Abstract Lead (Pb) contamination in environment has been identified as a threat to human health and ecosystems. In an effort to reduce the health and ecological risks associated with Pb mining wastes, a field study was conducted to stabilize Pb using phosphate (P)-enriched biosolid amendments in contaminated mining wastes (average of 1004 mg Pb kg -1 ) located within the Jasper County Superfund Site, southwest Missouri. Experiments consisted of six treatments, including Mizzou Doo (MD); Spent mushroom compost (SMC); Turkey litter compost (TLC); Composted chicken litter (CCL); Composed sewage sludge (CSS); and Triple superphosphate (TSP). Tall fescue seeds were planted following treatments and soil and plant samples collected and analyzed 8-10 years post treatment. Results indicated that all biosolid treatments resulted in effective reductions of bioaccessible, leachable and phytoavailable Pb in the treated waste. The treatments had no toxicological effect to soil microbial community. Analysis of the Pb fractionation revealed that the Pb risk reduction was acomplished by transforming labile Pb to relatively stable species through chemical stabilization reactions as induced by treatments. The solid-phase microprobe analysis confirmed the formation of pyromorphite or pyromorphite-like minerals after treatment. Among the six amendments examined, SMC and MD treatments were shown most effective in context of Pb stabilization and risk reduction. This study demonstrated that the efficacy of Pb stabilization and risk reduction by P-enriched biosolid amendments was long-term and environmental-sound, which could be potentially applied as a cost-effective remedial technology to restore contaminated mining site and safeguard human health and ecosystems from Pb contamination.

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