Nucleation and Precipitation Processes in the Vadose Zone During Contaminant Transport - PowerPoint PPT Presentation

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Nucleation and Precipitation Processes in the Vadose Zone During Contaminant Transport

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  1. Nucleation and Precipitation Processes in the Vadose Zone During Contaminant Transport BurcuUyusur, Christophe Darnault - UIC Civil and Materials Engineering Department; Kathryn L. Nagy, Neil C. Sturchio, SoufianeMekki - UIC Earth and Environmental Science Department Primary Grant Support: U.S. Department of Energy • Leakage has been determined in the vadose zone sediments of Hanford Site, U.S. Department of Energy Complex in Washington since 1950s, including radioactive elements such as uranium. • Preferential flow, a common phenomena in unsaturated soil, is the movement of water and solutes faster than the average pore water velocity due to fingering. • Visualization and mapping of simulated Hanford leakage water • Contaminant mobility is affected by sorption, colloid formation, nucleation and precipitation of secondary solids. • Characterize and quantify the formation of secondary precipitates in the presence of uranium with quartz and feldspar minerals. • Investigation of possible colloid formation • SEM and EDS of metaschoepite(UO3·n(H2O)(n<2) (Buck et al., 2004) • Three dimensional unsaturated column experiments • Two dimensional light transmission visualization experiments • Autoradiography Technique • Surface Analysis techniques (BET Gas Adsorption; AFM-Atomic Force Microscopy; XRD-X Ray Diffraction) • Insight Analysis Techniques (TRLFS-Time Resolved Laser Fluorescence Spectroscopy; EXAFS- Extended X-Ray Absorption Fine Structure) • Incorporation of the data to a reactive transport code • Understanding the fate and transport of uranium in simulated Hanford vadose zone • Refining the conditions needed for incorporation of radionuclides into secondary solids. • Predicting the effect of precipitates on vadose zone flow. • Modeling with colloids, nucleation, precipitation, sorption incorporated • Extracting general governing ideas applicable to other radioactive contaminated sites