Corrosion of Depleted Uranium in an Arid Environment: Soil-Geomorphology, SEM/EDS, XRD, and Electron Microprobe Analyses

Abstract

Corrosion of anthropogenic uranium in natural environments is not well understood, but is important for determining potential health risks and mobility in the environment. A site in the southwestern United States contains depleted uranium that has been weathering for approximately 22 years. Soil-geomorphic, SEM/EDS, XRD, and electron microprobe analyses were conducted to determine the processes controlling the uranium corrosion. Schoepite and metaschoepite are the primary products of corrosion, and occur as silica-cemented, mixed schoepite-metaschoepite/clay/silt aggregates, as schoepite/metaschoepite-only aggregates, or rarely as coatings upon soil grains. Current extraction procedures do not adequately explain the behavior of uranium in alkaline soils when amorphous silica and clay coatings are present. Soil geomorphology and chemistry at this site limit uranium mobility and decreases potential health risks. However, if land-use and/or regional climate changes occur, uranium mobility could increase.

Keywords:

• Schoepite
• metaschoepite
• arid soils
• sulfate
• amorphous silica.

This work was funded by the Environmental Assessment Division of Argonne National Laboratory through a contract with the US Navy Facilities Engineering Command. Thanks to two anonymous reviewers for helpful suggestions to an earlier manuscript, Robyn Howley for field assistance, James Talbot of K/T GeoServices and Nancy McMillan, NMSU for XRD assistance, and Gus P. Williams provided the field photographs.