Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values. (November 2016)

• Record Type: Journal Article
• Authors: Koster van Groos, Paul G.; Kaplan, Daniel I.; Chang, Hyun-shik; Seaman, John C.; Li, Dien; Peacock, Aaron D.; Scheckel, Kirk G.; Jaffé, Peter R.
• Is Part Of: Chemosphere. Volume 163(2016)
• Page Start: 116
• Page End: 124
• Publication Date: 2016-11
• Subjects: Uranium fate -- Uranium sequestration -- Wetlands -- Iron -- Rhizosphere -- Plants; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2016.08.012
• Languages: English
• ISSNs: 0045-6535

Abstract

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. Highlights: Wetland mesocosms used to examine U and iron (Fe) interactions at plant roots. U was less mobile near roots and found as U(V) or U(VI). U was associated with Fe phases on roots. Fe cycling in rhizosphere may facilitate U immobilization.