title: Sorption and bioreduction of hexavalent uranium at a military facility by the Chesapeake Bay.
abstract: Directly adjacent to the Chesapeake Bay lies the Aberdeen Proving Ground, a U.S. Army facility where testing of armor-piercing ammunitions has resulted in the deposition of >70,000 kg of depleted uranium (DU) to local soils and sediments. Results of previous environmental monitoring suggested limited mobilization in the impact area and no transport of DU into the nation's largest estuary. To determine if physical and biological reactions constitute mechanisms involved in limiting contaminant transport, the sorption and biotransformation behavior of the radionuclide was studied using geochemical modeling and laboratory microcosms (500 ppb U(VI) initially). An immediate decline in dissolved U(VI) concentrations was observed under both sterile and non-sterile conditions due to rapid association of U(VI) with natural organic matter in the sediment. Reduction of U(VI) to U(IV) occurred only in non-sterile microcosms. In the non-sterile samples, intrinsic bioreduction of uranium involved bacteria of the order Clostridiales and was only moderately enhanced by the addition of acetate (41% vs. 56% in 121 days). Overall, this study demonstrates that the migration of depleted uranium from the APG site into the Chesapeake Bay may be limited by a combination of processes that include rapid sorption of U(VI) species to natural organic matter, followed by slow, intrinsic bioreduction to U(IV).
authors.affiliation: Center for Water and Health, Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. dongw@ornl.gov
authors.forename: Wenming
authors.initials: W
authors.lastname: Dong
authors.forename: Guibo
authors.initials: G
authors.lastname: Xie
authors.forename: Todd R
authors.initials: TR
authors.lastname: Miller
authors.forename: Mark P
authors.initials: MP
authors.lastname: Franklin
authors.forename: Tanya Palmateer
authors.initials: TP
authors.lastname: Oxenberg
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Bouwer
authors.forename: William P
authors.initials: WP
authors.lastname: Ball
authors.forename: Rolf U
authors.initials: RU
authors.lastname: Halden
mesh_terms: D000327:Adsorption; D001711:Biotransformation; D003013:Clostridium / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D004787:Environmental Pollution / Q000032:analysis*; D006812:Humic Substances; D008396:Maryland; D008889:Military Personnel; D011850:Radioactive Waste / Q000032:analysis*; D011868:Radioisotopes / Q000032:analysis; D011891:Rain; D012988:Soil Microbiology; D012990:Soil Pollutants, Radioactive / Q000032:analysis; D014501:Uranium / Q000032:analysis*; D014872:Water Movements; D014878:Water Pollution, Radioactive / Q000032:analysis / Q000517:prevention & control
chemical_list: D006812:Humic Substances; D011850:Radioactive Waste; D011868:Radioisotopes; D012990:Soil Pollutants, Radioactive; D014501:Uranium