Evaluation and application of anion exchange resins to measure groundwater uranium flux at a former uranium mill site Valerie Stucker a , James Ranville a, *, Mark Newman b , Aaron Peacock d , Jaehyun Cho c , Kirk Hatfield b a Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO, USA b Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL, USA c Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL, USA d Microbial Insights Inc., Rockford, TN, USA article info Article history: Received 16 December 2010 Received in revised form 22 June 2011 Accepted 23 June 2011 Available online 13 July 2011 Keywords: Ion exchange Contaminant Passive flux meter Sorption abstract Laboratory tests and a field validation experiment were performed to evaluate anion exchange resins for uranium sorption and desorption in order to develop a uranium passive flux meter (PFM). The mass of uranium sorbed to the resin and corresponding masses of alcohol tracers eluted over the duration of groundwater installation are then used to determine the groundwater and uranium contaminant fluxes. Laboratory based batch experiments were performed using Purolite A500, Dowex 21K and 21K XLT, Lewatit S6328 A resins and silver impregnated activated carbon to examine uranium sorption and extraction for each material. The Dowex resins had the highest uranium sorption, followed by Lewatit, Purolite and the activated carbon. Recoveries from all ion exchange resins were in the range of 94e99% for aqueous uranium in the environmentally relevant concentra- tion range studied (0.01e200 ppb). Due to the lower price and well-characterized tracer capacity, Lewatit S6328 A was used for field-testing of PFMs at the DOE UMTRA site in Rifle, CO. The effect on the flux measurements of extractant (nitric acid)/resin ratio, and uranium loading were investigated. Higher cumulative uranium fluxes (as seen with concentrations > 1 ug U/gram resin) yielded more homogeneous resin samples versus lower cumulative fluxes (<1 ug U/gram resin), which caused the PFM to have areas of localized concentration of uranium. Resin homogenization and larger volume extractions yield reproducible results for all levels of uranium fluxes. Although PFM design can be improved to measure flux and groundwater flow direction, the current methodology can be applied to uranium transport studies. ª 2011 Elsevier Ltd. All rights reserved. 1. Introduction Uranium is a contaminant of concern at many DOE former mining and milling sites. With the passing of the Uranium Mill Tailings Radiation Control Act (UMTRCA) in 1978, tail- ings were removed to repositories and the surface soil was remediated from 24 inactive uranium mill sites. In Rifle, Colorado, the site of a former uranium and vanadium mill, * Corresponding author. E-mail address: jranvill@mines.edu (J. Ranville). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 45 (2011) 4866 e4876 0043-1354/$ e see front matter ª 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2011.06.030