27-25 Modeling Microbial Modulation of Lead Dynamics in Soil–Plant Systems: Insights from Switchgrass and Rhizosphere Interactions

Session: Environmental Geochemistry and Health (Posters)

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Abstract:

Lead (Pb) contamination of soils, particularly from mining activities and mining wastes, represents a persistent threat to both ecosystem and human health. While total Pb is routinely measured, its speciation and bioavailability remain rarely modeled quantitatively. Phytoremediation, especially when enhanced by rhizosphere microbial communities, offers a promising mitigation strategy.

Switchgrass (Panicum virgatum), a native perennial grass abundant at the Tar Creek Superfund site (a historic Pb-Zn mining area), has demonstrated strong potential for heavy metal phytoremediation. In this study, we combined greenhouse experiments with a numerical model to investigate Pb dynamics across a gradient of soil Pb concentrations (0–2000 mg/kg). Switchgrass was grown with and without inoculation of indigenous rhizosphere microbes, including arbuscular mycorrhizal (AM) fungi. Soil Pb was fractionated into bioavailable (soluble, exchangeable, acid-soluble) and bound (reducible, oxidizable, residual) pools, and their transformations were simulated over 120 days.

Modeling results predicted that >80% of bioavailable Pb could be removed within 120 days, regardless of the presence of microbes. However, microbial inoculation significantly stabilized the bioavailable-to-bound Pb conversion rate and reduced Pb mobility, highlighting a microbial buffering capacity under high Pb stress. This stabilization helps retain Pb in less bioavailable forms, limiting its mobility and reducing the risk of downstream human exposure.

These findings highlight the critical role of indigenous microbial communities in enhancing phytostabilization performance. Given the adaptability of the modeling framework, this approach can be extended to assess Pb and other metal dynamics in other plant–microbe systems and support the design of microbe-assisted remediation strategies across a range of contaminated sites.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9380

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