SREL Reprint #3888

Uranium remobilization from a riparian wetland: Implications on long-term stewardship and extreme rain events

Daniel I. Kaplan1, Karah M. Greene1, Wei Xing1, Arelis M. Rivera-Giboyeaux2, Kenneth M. Kemner3, and Peng Lin1

1Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA
2Atmospheric Technologies Group, Savannah River National Laboratory, Aiken, SC, USA
3Biosciences Division, Argonne National Laboratory, Lemont, IL, USA

Abstract: Natural attenuation of contaminants by wetlands can cause them to become secondary sources of contamination. The objectives of this field study were to: 1) measure the remobilization of uranium (U) in a stream flowing through a contaminated wetland in South Carolina, USA, and 2) develop empirical relationships between rainfall and U remobilization. Stream water was sampled hourly during six storm events ranging from 0.69 to 9.87 cm of rainfall, which caused flow to increase by as much as 1100% with respect to base flow. Uranium concentrations in all filtered samples, U < 0.45μm , were below the Maximum Contaminant Limit of 30 μg/L U. Conversely, as much as 94 vol% of the U in stream samples (g U/L streamwater) was associated with suspended solids, U ≥ 0.45μm. Consequently, significant correlations (p < 0.01) existed between stream water total U and suspended solids concentrations (or turbidity). Using a linear relationship (p < 0.01) between rainfall and remobilized U (g-U/sampling-event), it was estimated that 29% of the remobilized U in the year 2024 occurred during the three days of greatest rainfall. Similarly, using historical rainfall data, it was estimated that 864 kg-U, or 2.2% of the original 43,500 kg-U released into the wetland 55 years ago had been remobilized. This value of remobilized U is consistent with U-mass balance at the study site. Predictions of increased regional total rainfall and the number of extreme rainfall events may increase the rate of contaminant dispersion from riparian systems.

Keywords: Streams; Contaminant transport; Total suspended solids; Uranium

SREL Reprint #3888

Kaplan, D. I., K. M. Greene, W. Xing, A. M. Rivera-Giboyeaux, K. M. Kemner, and P. Lin. 2026. Uranium remobilization from a riparian wetland: Implications on long-term stewardship and extreme rain events. Applied Geochemistry 209(107024).

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