Gas: The neglected phase in remediation of metals and radionuclides

NUCL 12

Miles E. Denham, Brian B. Looney, and Amy A. Ekechukwu. Savannah River Technology Center, Westinghouse Savannah River Company, Building 773-42A, Savannah River Site, Aiken, SC 29808

Most strategies for remediating metals and radionuclides in groundwater focus on solid and aqueous phases. Yet the gas phase can also be an important component of remediation. Contaminants that can exist in volatile forms can be sparged from groundwater with air. Likewise, carbon dioxide manipulation can help stabilize contaminants, slowing their migration to exposure points. Finally, gas phase reagents can be used to stabilize inorganic contaminants.

Research at the Savannah River Site has shown that gas phase manipulation can be an effective remediation tool. Dissolved mercury was successfully removed from contaminated groundwater by reduction with stannous chloride followed by air sparging. Similarly, calculations suggest that air sparging of diiodine may be effective for remediating iodine-129. Studies also suggest that some contaminants can be co-precipitated with calcium carbonate by reducing carbon dioxide partial pressure with air sparging after acidic groundwater reacts with limestone. Another approach, currently under study, is injection of phosphate in a gas phase to promote microbial stabilization of inorganic contaminants.