Persistence of chromate in vadose zone and aquifer sediments in Hanford, Washington.

This study of vadose zone and aquifer sediments beneath a former dichromate spill site showed that the persistence of Cr in the sediments and the large differences in released mass and rate was caused by the dissolution of multiple Cr surface phases. Vadose zone sediments contained numerous 1 to 10 μm high solubility calcium chromate crystals, with lesser amounts of unidentified phases indicated by Ba/Cr association in weathered pyroxenes and Ca/Cr association in weathered Ca-rich plagioclase. Most (>90%) of the Cr mass in these vadose zone sediments was readily leached in laboratory columns at high concentrations (up to 187 mg/L Cr) likely from the highly soluble calcium chromate.

Influence of acidic and alkaline waste solution properties on uranium migration in subsurface sediments.

This study shows that acidic and alkaline wastes co-disposed with uranium into subsurface sediments have significant impact on changes in uranium retardation, concentration, and mass during downward migration. For uranium co-disposal with acidic wastes, significant rapid (i.e.

Enhanced remedial amendment delivery to subsurface using shear thinning fluid and aqueous foam.

A major issue with in situ subsurface remediation is the ability to achieve an even spatial distribution of remedial amendments to the contamination zones in an aquifer or vadose zone. Amendment delivery to the aquifer using shear thinning fluid and to the vadose zone using aqueous foam has the potential to enhance the distribution. 2-D saturated flow cell experiments were conducted to evaluate the enhanced fluid sweeping over heterogeneous system, improved contaminant removal, and extended amendment presence in low-permeability zones achieved by shear thinning fluid delivery.