Abstract

Understanding Cd and Pb in vitro bioaccessibility (IVBA) is important for evaluating human health risks in mine-impacted soils. In this field study, we assessed Cd and Pb bioaccessibility in a heavy metal contaminated mine impacted soil that received Low and High Compost applications (180 and 360 Mg ha−1, respectively), and Native Prairie soils within close proximity to the impacted soil, using three in vitro methods (Unites States Environmental Protection Agency (US EPA) pH 1.5, US EPA pH 2.5, and Ohio State University pH 1.8). Total Cd concentrations under High Compost (10.3 mg kg−1) exceeded the US EPA regional screening level (RSL)–residential soil Cd concentration for ingestion non-cancer risk in children (7.8 mg kg−1), while Low Compost and Native Prairie soils were below the RSL. Total Pb (<75 mg kg−1) in all sites was below the US EPA RSL for Pb for non-cancer risk in children (200 mg kg−1). Within each extraction method, Cd IVBA remained consistently high (>70% of total) across all three sites for at least US EPA pH 1.5 and OSU pH 1.8. In contrast, Pb IVBA varied across methods, with the pH 2.5 extraction consistently yielding lower Pb IVBA as compared to the other IVBA methods. These findings suggest that Cd poses a challenge for risk mitigation at this site, while Pb shows more promising stabilization outcomes. Findings highlight the importance of tailoring amendment strategies and selecting appropriate in vitro assays when assessing remediation effectiveness and risk within multi-metal contaminated mine-impacted sites, while emphasizing the need for long-term field validation of metal stability under real-world conditions.

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