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Environmental context Uranium is a key contaminant of concern because of its high persistence in the environment and toxicity to organisms. The bicarbonate ion is an important complexing agent for uranyl ions and one of the main variables affecting its dissolution. Results from this investigation provide rate law parameters for the dissolution kinetics of synthetic sodium autunite that can influence uranium mobility in the subsurface. Abstract Hydrogen carbonate (also known as bicarbonate) is one of the most significant components within the uranium geochemical cycle. In aqueous solutions, bicarbonate forms strong complexes with uranium. As such, aqueous bicarbonate may significantly increase the rate of uranium release from uranium minerals. Quantifying the relationship of aqueous bicarbonate solutions to the rate of uranium release during dissolution is critical to understanding the long-term fate of uranium within the environment. Single-pass flow-through experiments were conducted to estimate the rate of uranium release from Na meta-autunite as a function of bicarbonate solutions (0.0005–0.003M) over the pH range of 6–11 and temperatures of 5–60°C. Consistent with the results of previous investigations, the rate of uranium release from sodium autunite exhibited minimal dependency on temperature, but was strongly dependent on pH and increasing concentrations of bicarbonate solutions. Most notably at pH 7, the rate of uranium release exhibited a 370-fold increase relative to the rate of uranium release in the absence of bicarbonate. However, the effect of increasing concentrations of bicarbonate solutions on the release of uranium was significantly less under higher pH conditions. It is postulated that at high pH values, surface sites are saturated with carbonate, thus the addition of more bicarbonate would have less effect on uranium release. Results indicate that the activation energies were unaffected by temperature and bicarbonate concentration variations, but were strongly dependent on pH conditions. As the pH increased from 6 to 11, the activation energy values were observed to decrease from 29.94 to 13.07kJmol–1. The calculated activation energies suggest a surface controlled dissolution mechanism.

A major focus of Department of Energy’s (DOE’s) environmental management mission at the Hanford site involves characterizing and remediating contaminated soil and groundwater; stabilizing contaminated soil; remediating disposal sites; decontaminating and decommissioning structures, and demolishing former plutonium production process buildings, nuclear reactors, and separation plants; maintaining inactive waste sites; transitioning facilities into the surveillance and maintenance program; and mitigating effects to biological and cultural resources from site development and environmental cleanup and restoration activities. For example, a total of 470,914 metric tons of contaminated soil from 100 Areas remediation activities were disposed at the Environmental Restoration Disposal Facility (ERDF) during 2004 [5]. The Applied Research Center (ARC) at Florida International University (FIU) is supporting the Hanford’s site remediation program by analyzing the effectiveness of several soil stabilizers (fixatives) for contamination control during excavation activities. The study is focusing on determining the effects of varying soil conditions, temperature, humidity and wind velocity on the effectiveness of the candidate stabilizers. The test matrix consists of a soil penetration-depth study, wind tunnel experiments for determination of threshold velocity, and temperature and moisture-controlled drying/curing experiments. These three set of experiments are designed to verify performance metrics, as well as provide insight into what fundamental forces are altered by the use of the stabilizer. This paper only presents the preliminary results obtained during wind tunnel experiments using dry Hanford soil samples (with 2.7% moisture by weight). These dry soil samples were exposed to varying wind speeds from 2.22 m/sec to 8.88 m/sec. Furthermore, airborne particulate data was collected for the dry Hanford soil experiments using an aerosol analyzer instrument.