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RISS 인기검색어
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- 저자 : Perdrial, Nicolas (검색결과 2 건)
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Chang, Hyun-shik,Um, Wooyong,Rod, Kenton,Serne, R. Jeff,Thompson, Aaron,Perdrial, Nicolas,Steefel, Carl I.,Chorover, Jon American Chemical Society 2011 Environmental science & technology Vol.45 No.19
<P>Leaching behavior of Sr and Cs in the vadose zone of Hanford site (Washington) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10<SUP>–5</SUP> and 10<SUP>–3</SUP> molal representative of LO- and HI-sediment, respectively) as surrogates for <SUP>90</SUP>Sr and <SUP>137</SUP>Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2011/esthag.2011.45.issue-19/es2010368/production/images/medium/es-2011-010368_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es2010368'>ACS Electronic Supporting Info</A></P>
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Wang, Guohui,Um, Wooyong,Wang, Zheming,Reinoso-Maset, Estela,Washton, Nancy M.,Mueller, Karl T.,Perdrial, Nicolas,O’Day, Peggy A.,Chorover, Jon American Chemical Society 2017 Environmental science & technology Vol.51 No.19
<P>The reaction of acidic radioactive waste with sediments can induce mineral transformation reactions that, in turn, control contaminant fate. Here, sediment weathering by synthetic uranium containing acid solutions was investigated using bench-scale experiments to simulate waste disposal conditions at Hanford's cribs (Hanford, WA). During acid weathering, the presence of phosphate exerted a strong influence over uranium mineralogy and a rapidly precipitated, crystalline uranium phosphate phase (meta-ankoleite [K(UO2)(PO4).3H(2)O] was identified using spectroscopic and diffraction-based techniques. In phosphate-free system, uranium oxyhydroxide minerals such as K-compreignacite [K-2(UO2)(6)O-4(OH)(6).7H(2)O] were formed. Single-pass flow-through (SPFT) and column leaching experiments using synthetic Hanford pore water showed that uranium precipitated as meta-ankoleite during acid weathering was strongly retained in the sediments, with an average release rate of 2.67 X 10(-12) mol g(-1) s(-1). In the absence of phosphate, uranium release was controlled by dissolution of uranium oxyhydroxide (compreignacitetype) mineral with a release rate of 1.05-2.42 X 10(-1) mol g(-1) s(-1). The uranium mineralogy and release rates determined for both systems in this study support the development of accurate U-release models for the prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.</P>
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