DOE/SC0001389 Final technical report: Investigation of uranium attenuation and release at column and pore scales in response to advective geochemical gradients

doi:10.2172/1079214

GSTDTAP > 地球科学

DOI	10.2172/1079214
报告编号	DOE/SC0001389-1
来源ID	OSTI ID: 1079214
	DOE/SC0001389 Final technical report: Investigation of uranium attenuation and release at column and pore scales in response to advective geochemical gradients
	Savage, Kaye S. [Wofford College]; Zhu, Wenyi [Wofford College]; Barnett, Mark O. [Auburn University]
	2013-05-13
出版年	2013
语种	英语
国家	美国
领域	地球科学
英文摘要	Experimental approach Column experiments were devised to investigate the role of changing fluid composition on mobility of uranium through a sequence of geologic media. Fluids and media were chosen to be relevant to the ground water plume emanating from the former S-3 ponds at the Oak Ridge Integrated Field Research Challenge (ORIFC) site. Synthetic ground waters were pumped upwards at 0.05 mL/minute for 21 days through layers of quartz sand alternating with layers of uncontaminated soil, quartz sand mixed with illite, quartz sand coated with iron oxides, and another soil layer. Increases in pH or concentration of phosphate, bicarbonate, or acetate were imposed on the influent solutions after each 7 pore volumes while uranium (as uranyl) remained constant at 0.1mM. A control column maintained the original synthetic groundwater composition with 0.1mM U. Pore water solutions were extracted to assess U retention and release in relation to the advective ligand or pH gradients. Following the column experiments, subsamples from each layer were characterized using microbeam X-ray absorption spectroscopy (XANES) in conjunction with X-ray fluorescence mapping and compared to sediment core samples from the ORIFC, at SSRL Beam Line 2-3. Results U retention of 55-67mg occurred in phosphate >pH >control >acetate >carbonate columns. The mass of U retained in the first-encountered quartz layer in all columns was highest and increased throughout the experiment. The rate of increase in acetate- and bicarbonate-bearing columns declined after ligand concentrations were raised. U also accumulated in the first soil layer; the pH-varied column retained most, followed by the increasing-bicarbonate column. The mass of U retained in the upper layers was far lower. Speciation of U, interpreted from microbeam XANES spectra and XRF maps, varied within and among the columns. Evidence of minor reduction to U(IV) was observed in the first-encountered quartz layer in the phosphate, bicarbonate, and pH columns while only U(VI) was observed in the control and acetate columns. In the soil layer, the acetate and bicarbonate columns both indicate minor reduction to U(IV), but U(VI) predominated in all columns. In the ORIFC soils, U was consistently present as U(VI); sorption appears to be the main mechanism of association for U present with Fe and/or Mn, while U occurring with P appears in discrete particles consistent with a U mineral phase. U in soil locations with no other elemental associations shown by XRF are likely uranium oxide phases.
英文关键词	X-ray absorption spectroscopy reactive transport ground water
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来源平台	US Department of Energy (DOE)
引用统计
文献类型	科技报告
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/6082
专题	地球科学
推荐引用方式 GB/T 7714	Savage, Kaye S. [Wofford College],Zhu, Wenyi [Wofford College],Barnett, Mark O. [Auburn University]. DOE/SC0001389 Final technical report: Investigation of uranium attenuation and release at column and pore scales in response to advective geochemical gradients,2013.