Firing range soils yield a diverse fungal community capable of Pb‐mineral solubilization and organic acid secretion

Toyota Auditorium, Howard H. Baker Jr. Center for Public Policy

Lead (Pb) contaminated soils represent severe environmental problems as well as a significant hazard to human health. Many species of fungi are capable of transforming insoluble metal compounds into soluble derivatives, an environmentally important process when these fungi constitute a significant portion of the overall soil community. The objective of this study is to understand the potential capacity of the soil fungal community for Pb-mineral solubilization via organic acid secretion at an abandoned small-arms firing range in east Tennessee. Six soils were collected from locations around the abandoned firing range; these soils were analyzed for total Pb content and used to derive fungal isolates via serial dilution plating. Isolates were screened for organic acid production and solubilization of lead carbonate at concentrations ranging from 3mM to 18mM. Soil Pb concentrations at the site ranged up over 2500 mg kg^-1 and the number of cultivable fungi was not significantly different between soil Pb levels. We obtained 220 total isolates, 26% of which were capable of acidification of two different types of growth media. Types and amounts of organic acids secreted varied with phylogenetic affiliation and several of these species were also capable of solubilizing lead carbonate at all tested concentrations.Many of these acid-producing fungi were also capable of solubilizing lead-carbonate, a Pb-mineral frequently found at both active and abandoned firing ranges. This could mean these fungi are capable of not only acidification but also solubilizing Pb-minerals in their native soil habitats.