title: Persistent source influences on the trailing edge of a groundwater plume, and natural attenuation timeframes: the F-Area Savannah River Site.
abstract: At the Savannah River Site's F-Area, wastewaters containing radionuclides were disposed into seepage basins for decades. After closure and capping in 1991, the U.S. Department of Energy (DOE) has being monitoring and remediating the groundwater plume. Despite numerous studies of the plume, its persistence for over 20 years has not been well understood. To better understand the plume dynamics, a limited number of deep boreholes were drilled to determine the current plume characteristics. A mixing model was developed to predict plume tritium and nitrate concentrations. We found that the plume trailing edges have emerged for some contaminants, and that contaminant recharge from the basin's vadose zone is still important. The model's estimated time-dependent basin drainage rates combined with dilution from natural recharge successfully predicted plume tritium and nitrate concentrations. This new understanding of source zone influences can help guide science-based remediation, and improve predictions of the natural attenuation timeframes.
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, California, USA. jwan@lbl.gov
authors.forename: Jiamin
authors.initials: J
authors.lastname: Wan
authors.forename: Tetsu K
authors.initials: TK
authors.lastname: Tokunaga
authors.forename: Wenming
authors.initials: W
authors.lastname: Dong
authors.forename: Miles E
authors.initials: ME
authors.lastname: Denham
authors.forename: Susan S
authors.initials: SS
authors.lastname: Hubbard
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D060587:Groundwater / Q000032:analysis*; D008962:Models, Theoretical; D009566:Nitrates / Q000032:analysis; D011850:Radioactive Waste; D013022:South Carolina; D014316:Tritium / Q000032:analysis; D014501:Uranium / Q000032:analysis; D014872:Water Movements; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D009566:Nitrates; D011850:Radioactive Waste; D014875:Water Pollutants, Radioactive; D014316:Tritium; D014501:Uranium