Long-term corrosion and leaching of depleted uranium (DU) in the soil

The corrosion and leaching of depleted uranium (DU) was investigated for three years using six DU munitions (145 – 264 g DU) each buried in a column with a soil core of ca. 3.3 kg dry soil mass. The columns were installed in an air-conditioned la-boratory. Each week they were irrigated and 238U was determined in the effluents by Inductively Coupled Plasma Mass Spectrometry. In addition, 235U was measured oc-casionally in order to assure that the origin of 238U was predominantly the DU muniti-on. On average, 14.5 g corresponding to 7.9 % of the initial DU mass was corroded after three years indicating an acceleration of the corrosion as compared to the first year (see Schimmack et al., Radiat Environ Biophysics 44: 183-191 (2005)). The leaching rates increased much stronger than the corrosion by factors of more than 100 resulting in a mean total amount of leached 238U of 13 mg as compared to 0.03 mg after the first year. The uranium species identified by time-resolved laser-induced fluorescence spectroscopy were mainly hydroxo and carbonate compounds in the seepage water and phosphate compounds in the corroded material. It is concluded that the dramatic increase of the leaching and its large temporal and spatial variability do not allow any extrapolation into the future. However, the high level of the 238U concentrations in the seepage water demands further investigations on the transport of 238U through the soil in order to estimate the concentration of 238U from DU muniti-ons in the groundwater for areas affected by DU weapons.