Biogeochemical Controls on the Corrosion of Depleted Uranium Alloy in Subsurface Soils

Abstract

Military activities have left a legacy of depleted uranium (DU) penetrator waste in the near-surface terrestrial environment. To understand the fate of this DU alloy, the mechanisms and controlling factors of corrosion need to be determined. In this study, field-moist and waterlogged microcosms were used to investigate the effect of redox conditions and soil water content on the corrosion and fate of DU in subsurface soil, and the impact of corroding DU on the soil microbial population. The mechanism of corrosion and the corrosion products formed were highly dependent on the water status of the soil. Under field-moist conditions, DU corroded at a rate of 0.49 +/- 0.06 g cm(-2) y(-1) and the main U input to surrounding soil was large metaschoepite [(UO2)8O2(OH)12 x (H2O)10] particles. However, underwaterlogged conditions the rate of corrosion was significantly slower at 0.01-0.02 g cm(-2) y(-1) and occurred with the release of dissolved species to the surrounding environment. Corrosion ceases under reducing conditions, thus redox conditions are important in determining the persistence of penetrators in the environment. Corroding DU alters the redox conditions in the surrounding environment and both mechanisms of corrosion impact the microbial community.

Products of in Situ Corrosion of Depleted Uranium Ammunition in Bosnia and Herzegovina Soils

“…3 Using the size information on penetrators reported by Bleise et al, 2 it is roughly estimated that the corrosion rate of the "HP" and "Hz" penetrators is 0.22 ± 0.05 and 0.26 ± 0.05 g cm −2 yr −1 , respectively (Table S2). These values fall in the range of the corrosion rates reported in laboratory column 19 and microcosm 16,18 studies with unsaturated soils (0.1−0.5 g cm…”

“…Other studies also investigated U mineralogy of corroded DU bulk metal. For example, in laboratory microcosms, DU metal coupons cut from penetrators corroded in sandy soil, 16 estuarine sediment 17 or silty-loam soil 18 for about 500 days. The results indicated that DU metal mainly corroded to metaschoepite in unsaturated sandy and silty-loam soils, whereas uraninite formed in suboxic/anoxic estuarine sediment.…”

Modulation of Medium pH by Caulobacter crescentus Facilitates Recovery from Uranium-Induced Growth Arrest

“…S1 in the supplemental material. The pH of each growth medium, including those lacking added uranyl nitrate, was standardized through the addition of an equivalent amount of HNO 3 . Where indicated, the supernatant from cell cultures was collected by centrifugation at 20,000 ϫ g for 8 min and then filtered through a 0.22-m membrane.…”

“…The membrane potential probe bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DIBAC 4 (3)] (Molecular Probes, Inc.), which enters cells with depolarized membranes, and the dead cell stain propidium iodide ReadyProbes (PI) (Molecular Probes, Inc.) were used to assess cell viability during growth arrest induced by 350 M U(VI). DIBAC 4 (3) was added at 1 g/ml, and PI was used according to the manufacturer's instructions.…”

“…At circumneutral pH, U(VI) oxycations are present and form stable, soluble complexes with carbonate, phosphate, and natural organic matter, which greatly influence the mobility and toxicity of U(VI) (1). The formation of these complexes is governed by pH, redox potential, temperature, and ligand concentration (1,3,4). Although the relationship between U(VI) speciation and bioavailability is complex since certain ligands can either promote or inhibit U(VI) immobilization depending on the environmental conditions, it is evident that U(VI) in strong complexes or adsorbed to colloidal or particulate matter has reduced bioavailability and toxicity compared to those of the naked U(VI) oxycation (1,5).…”