SREL Reprint #3597

Uranium attenuated by a wetland 50 years after release into a stream

Daniel I. Kaplan1, Ronald Smith2, Connor J. Parker3, Matthew Baker4, Tristan Cabrera3,
Brennan O. Ferguson3, Kenneth M. Kemner5, Michael Laird1, Christina Logan4, Jeffry Lott4, Lisa Manglass3, Nicole E. Martinez3, Dawn Montgomery3, John C. Seaman4, Morgan Shapiro4, and Brian A. Powell1,3

1Savannah River National Laboratory, Aiken, South Carolina 29808, United States
2Savannah River Nuclear Solutions, Aiken, South Carolina 29808, United States
3Department of Environmental Engineering and Earth Science, Clemson University,
Clemson, South Carolina 29634, United States
4Savannah River Ecology Laboratory, University of Georgia,
Aiken, South Carolina 29808, United States
5Argonne National Laboratory, Argonne, Illinois 60439, United States

Abstract: Wetlands have several important roles in the hydrological cycle, including maintaining water quality by removing surface and groundwater contaminants. Over time, the wetlands themselves can become contaminated, posing a secondary environmental threat. The objective of this study was to calculate the inventory of uranium (U) remaining in a wetland 50 years after the Fuel Fabrication Facility on the Savannah River Site located in South Carolina released 43.5 Mg of U into the nearby environment. Over 232,700 gamma spectra and their associated global positioning system (GPS) coordinates were collected and collated into a map of the contaminated land area. Five core samples were also collected that contained U concentrations as high as 14,099 mg/kg (background levels are about 2.7 mg/kg U). The contaminated area was 278,000 m2, and it contained 36.2 Mg U, about 83% of the U released. About 80% of the U in the wetland was concentrated in a former beaver pond, a 73,000 m2 area (26% of the contaminated area). This contaminated wetland area was almost 2 km from the source, indicating that it comprised unique hydro-biogeochemical properties for immobilizing the released U. To the best of our knowledge, this is the first data-rich study to quantify the long-term effectiveness of a wetland to immobilize inorganic contaminants. Significant environmental changes to the system, such as those associated with hydrology, forest fires, or anthropogenic land use, may alter the complex hydro-biogeochemical interactions necessary for the long-term immobilization of the U.

Keywords: natural attenuation, wetlands, gamma spectroscopy, contaminant inventory, source terms, depth profiles, global positioning system

SREL Reprint #3597

Kaplan, D. I., R. Smith, C. J. Parker, M. Baker, T. Cabrera, B. O. Ferguson, K. M. Kemner, M. Laird, C. Logan, J. Lott, L. Manglass, N. E. Martinez, D. Montgomery, J. C. Seaman, M. Shapiro, and B. A. Powell. 2020. Uranium attenuated by a wetland 50 years after release into a stream. ACS Earth and Space Chemistry 4(8): 1360-1366.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).