Nanoparticle-facilitated transport of uranium and nickel in contaminated sediments near a nuclear weapons processing facility

The Department of Energys Savannah River Site (SRS) has released a total of over 44,000 kg of depleted uranium (U) and a similar amount of nickel (Ni) into the Tims Branch-Steed Pond (TBSP) system. Failure of the Steed Pond dam in the 1980s exposed sediments that facilitated significant transfer of U to downstream ecosystems largely in association with particulates suspended during rainfall events. In order to evaluate the effects of TBSP re-vegetation, we assessed U mass flux during rain events, and spiked TBSP soils with several different amendments after oxic, anoxic, and pH adjusted laboratory incubations. Current storm event U mass flux has diminished since re-vegetation. Soil incubations indicated anoxic conditions in seasonally saturated sediments were potentially a major source of generating mobile U, while phosphate amendments can generate colloids. Understanding conditions responsible for U dispersion in contaminated systems and the forms of this U may lead to controlling future mobilization.