facilities within the weapons complex. The inventory of chemicals and mixtures was used to identify generic chemical mixtures to be used by DOE'S Subsurface Science Program in basic research on the subsurface geochemical and microbiological behavior of mixed contaminants (DOE 1990a and b). The generic mixtures contain specific radionuclides, metals, organic ligands, organic solvents, fuel hydrocarbons, and polychlorinated biphenyls (PCBs) in various binary and ternary combinations. The mixtures are representative of in-ground contaminant associations at DOE facilities that are likely to exhibit complex geochemical behavior as a result of intercontaminant reactions and/or microbiologic activity stimulated by organic substances. Use of the generic mixtures will focus research on important mixed contaminants that are likely to be long-term problems at DOE sites and that will require cleanup or remediation.The report provides information on the frequency of associations among different chemicals and compound classes at DOE waste sites that require remediation. For example, radionuclides such as uranium, plutonium, strontium, and cobalt were found, in some cases, to be disposed of with organic substances (e.g., organic acids, complexing agents, and solvents) that could influence radionuclide geochemical behavior and subsurface transport. Knowledge of the types of chemicals that coexist in waste sites is important to remediation for various reasons:. The efficiency of many biotic and abiotic treatment processes for soil and ground-water contaminants is affected by the presence of co-contaminants.m Multiple contaminant species may be treated simultaneously and more effectively by specific aboveground or in-ground techniques if the nature of the contaminant association is understood in advance.rn Certain types of chemical mixtures may require special precautions or the development of new remediation strategies or techniques.rn In-ground remediation activities may selectively mobilize certain mixtures of chemical constituents to air or ground water, thereby increasing environmental risk; or some mixtures may be stabilized, thus reducing environmental impact.iiiThe report provides quantitative information on the frequency of occurrence of binary, ternary, and higher order contaminant mixtures in the 91 waste sites. This quantitative information may be used to refine or guide the development of new aboveground and in situ remediation strategies that can be used throughout the weapons complex.Scientists T waste sites at 18 U.S. Department of Energy (DOE) facilities. The review was conducted to identify (1) inorganic and organic contaminants found within soil and ground water at DOE waste sites, ( 2 ) their concentration ranges, and (3) their frequency of occurrence as single compounds and as binary, ternary, quaternary, and higher order contaminant mixtures. Fuel hydrocarbons, chlorinated hydrocarbons, radionuclides, metals, inorganic anions, and ketones were the contaminant classes most frequently measured in the ground at...
