In Situ Long-Term Reductive Bioimmobilization of Cr(VI) in Groundwater Using Hydrogen Release Compound.

The results of a field experiment designed to test the effectiveness of a novel approach for long-term, in situ bioimmobilization of toxic and soluble Cr(Vl) in groundwater using a hydrogen release compound (HRC)—a slow release glycerol polylactate—are described. The field experiment was conducted at the Hanford Site (Washington), a U.S. Department of Energy nuclear production facility, using a combination of hydrogeological, geophysical, geochemical, and microbiological measurements and analyses of water samples and sediments. The results of this experiment show that a single HRC injection into groundwater stimulates an increase in biomass, a depletion of terminal electron acceptors O2, NO3-, and SO42-, and an increase in Fe2+, resulting in a significant decrease in soluble Cr(Vl). The Cr(VI) concentration has remained below the background concentration in the down gradient pumping! monitoring well, and below the detection limit in the injection well for more than 3 years after the HRC injection. The degree of sustainability of Cr(Vl) reductive bioimmobilization under different redox conditions at this and other contaminated sites is currently under study. [ABSTRACT FROM AUTHOR]