SREL Reprint #3367

Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values

Paul G. Koster van Groos1, Daniel I. Kaplan2, Hyun-shik Chang3, John C. Seaman3,
Dien Li2, Aaron D. Peacock4, Kirk G. Scheckel5, and Peter R. Jaffé1

1Princeton University, Princeton, NJ 08540, USA
2Savannah River National Laboratory, Aiken, SC 29808, USA
3Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA
4Pace Analytical Energy Services, Pittsburgh, PA 15238, USA
5US EPA, Cincinnati, OH 45268, USA

Abstract: Small-scale continuous flow wetland mesocosms (~0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments. Micro X-ray absorption near-edge structure (µ-XANES) spectroscopy indicated that U was associated with the plant roots primarily as U(VI) or U(V), with limited evidence of U(IV). Micro X-ray fluorescence (µ-XRF) of plant roots suggested that for high iron loading at circumneutral pH, U was co-located with Fe, perhaps co-precipitated with root Fe plaques, while for low iron loading at a pH of ~4 the correlation between U and Fe was not significant, consistent with previous observations of U associated with organic matter. Quantitative PCR analyses indicated that the root exposed sediments also contained elevated numbers of Geobacter spp., which are likely associated with enhanced iron cycling, but may also reduce mobile U(VI) to less mobile U(IV) species.

Keywords: Uranium fate, Uranium sequestration, Wetlands, Iron, Rhizosphere, Plants

SREL Reprint #3367

Koster van Groos, P., D. I. Kaplan, H. Chang, J. C. Seaman, D. Li, A. D. Peacock, K. G. Scheckel, and P. R. Jaffé. 2016. Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values. Chemosphere 163(2016): 116-124.

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