Resupply Mechanism to a Contaminated Aquifer: A Laboratory Study of U(VI) Desorption from Capillary Fringe Sediments

Journal Article · Wed Sep 15 00:00:00 EDT 2010 · Geochimica et Cosmochimica Acta, 74(18):5155-5170

DOI:https://doi.org/10.1016/j.gca.2010.02.001· OSTI ID:988649

Um, Wooyong; Zachara, John M; Liu, Chongxuan; Moore, Dean A; Rod, Kenton A

Contaminated capillary fringe sediments are believed to function as long term source of U(VI) to Hanford’s 300 Area groundwater uranium plume that discharges to the Columbia River. The deep vadose zone at this site experiences seasonal water table elevation and water compositional changes in response to Columbia River stage. Batch and column desorption experiments of U(VI) were performed on two mildly contaminated sediments from this system that vary in hydrologic position to ascertain their U(VI) release behavior and factors controlling it. Solid phase characterization of the sediments was performed to identify mineralogic and chemical factors controlling U(VI) desorption. The desorption behavior of U(VI) was different from the two sediments in spite of similar chemical and textural characteristics, and non-carbonate mineralogy. Adsorption strength and sorbed U(VI) lability was higher in the near-river sediment 11D. Inland sediment 39B displayed low sorbed U(VI) lability (~ 10%) and measurable solid-phase carbonate content. Kinetic desorption was observed that was attributed to regeneration of labile U(VI) in 11D, and carbonate mineral dissolution in 39B. The desorption reaction was best described as an equilibrium surface complexation reaction. The noted differences in desorption behavior appear to result from U(VI) contamination and hydrologic history, as well as sediment carbonate content. Insights are provided on the dynamic adsorption/desorption behavior of contaminants in linked groundwater-river systems.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 988649
• Report Number(s): PNNL-SA-63210; KP1702030; TRN: US1006702
• Journal Information: Geochimica et Cosmochimica Acta, 74(18):5155-5170, Vol. 74, Issue 18; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ADSORPTION
CARBONATE MINERALS
CARBONATES
COLUMBIA RIVER
CONTAMINATION
DESORPTION
DISSOLUTION
KINETICS
MINERALOGY
PLUMES
REGENERATION
SEDIMENTS
URANIUM
WATER
WATER TABLES
SURFACE COMPLEXATION MODEL
URANIUM(VI) ADSORPTION
HANFORD SEDIMENTS
VADOSE ZONE
GEOCHEMICAL CONDITIONS
REACTIVE TRANSPORT
TERNARY COMPLEXES
POROUS-MEDIA
WATER-FLOW
SORPTION