Horizontal and Vertical Transport of Uranium in an Arid Weapon-Tested Ecosystem

Armor-penetrating projectiles and fragments of depleted uranium (DU) have been deposited in soils at weapon-tested sites. Soil samples from these military facilities were analyzed by inductively coupled plasma-optical emission spectroscopy and X-ray diffraction to determine U concentrations and transport across an arid ecosystem. Under arid conditions, both vertical transport driven by evaporation (upward) and leaching (downward) and horizontal transport of U driven by surface runoff in the summer were observed. Upward vertical transport was simulated and confirmed under laboratory-controlled conditions, to be leading to the surface due to capillary action via evaporation during alternating wetting and drying conditions. In the field, the 92.8% of U from DU penetrators and fragments remained in the top 5 cm of soil and decreased to background concentrations in less than 20 cm. In locations prone to high amounts of water runoff, U concentrations were reduced significantly after 20 m from the source due to high surface runoff. Uranium was also transported throughout the ecosystem via plant uptake and wild animal consumption between trophic levels, but with limited accumulation in edible portions in plants and animals.