Interactions among phosphate amendments, microbes and uranium mobility in contaminated sediments

Abstract

The use of sequestering agents for the transformation of radionuclides in low concentrations in contaminated soils/sediments offers considerable potential for longterm environmental cleanup. This study evaluated the influence of four phosphate amendments and two microbial amendments on U availability. The synchrotron X-ray fluorescence mapping of the untreated U-contaminated sediment showed that U was closely associated with Mn. All tested phosphate amendments reduced aqueous U concentration more than 90%, likely due to formation of insoluble phosphate precipitates.The addition of A. piechaudii and P. putida alone were found to reduce U concentrations 63% and 31% respectively. Uranium sorption in phosphate treatments was significantly reduced in the presence of microbes. However, increased microbial activity in the treated sediment led to reduction of phosphate effectiveness. The average U concentration in 1 M MgCl 2 extract from U amended sediment was 437 µg/kg, but in the same sediment without microbes (autoclaved sediment), the extractable U concentration was only 103 µg/kg. When the autoclaved amended sediment was treated with autoclaved biological apatite, U concentration in the 1 M MgCl 2 extract was ~0 µg/kg. Together these tests suggest that microbes may enhance U leaching and reduce phosphate amendment remedial effectiveness.

The effects of non-metabolizing bacterial cells on the precipitation of U, Pb and Ca phosphates

“…The numerals "1", "2", and "3" represent saturation state conditions discussed in detail in the text and are presented here for reference. Gorman-Lewis et al, 2005;Knox et al 2008). However, the opposite occurs in most of our experiments, with higher aqueous U concentrations in the B. subtilis biotic experiments.…”

The effect of the tetraalkylammonium salts on the protonation thermodynamics of the phytate anion

“…Recently, a review on the sequestering ability of this ligand in aqueous solutions, with particular reference to natural waters and biological fluids [6], has also been reported. Some applications of phytic acid regard its use in the remediation field for the removal of toxic metal and organo-metal cations [7][8][9][10], in electrochemistry as sensor [11] and many others described in recent reviews [6,[12][13][14][15][16].…”

Optimization of Chromium Removal by the Indigenous Bacterium Bacillus spp. REP02 Using the Response Surface Methodology

“…REP02 was able to utilize Mg 2+ ions when the concentration of this ion was low in simple medium, thereby stimulating chromium removal. Bacteria may enhance the uptake of heavy metals by increasing Mg 2+ -soluble fraction by dissolution and desorption due to the secretion of protons [28]. …”