Desert mine tailings present a significant health risk to proximal communities from off-site wind and water transport of metal-laden particles. Tailings undergo oxidative biogeochemical alteration in response to e.g., bimodal annual precipitation forcing, with pyrite oxidation being catalyzed by a dominantly autotrophic microbial biomass leading to strong redox zonation in the top meter(s) and sulfate surface crust formation. Options for remediation include vegetation establishment to diminish physical erosion and off-site contaminant transport. Changes in microbial composition and metal(loid) nano-scale speciation during infusion of water and organic matter into weathered desert tailings remain poorly known. Our field, mesocosm and laboratory studies show that  ensuing disequilibrium results in an accretion of neutrophilic heterotrophic microbial biomass concurrent with a time series of (bio)geochemical transformations in Fe, S and Mn minerals. These weathering reactions then control the form, fate and bioavailability of toxic metal(loid)s including Pb, Zn and As.

Toxic metal(loid) speciation is controlled by iron mineral (bio)weathering inphyto-stabilized mine tailings

246th National Meeting (2013)

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