Summary (1995-2000)

This program concentrates on the development of methods to evaluate risks from a hazardous waste disposal site, and is assessing the feasibility of mitigating such risks using either native soil micro-organisms or bacteria with specific biodegradative traits. The principle hypothesis for this approach is that a waste site is a dynamic system which presents evolving risks. Changes in risk to organisms located near a waste site are a function of various interrelated actions including the movement of toxic chemicals within and off the site, the chemically and microbiologically catalyzed transformations of waste materials, and the toxicant interactions which are based on exposures to multiple chemicals. This program aims to understand these changes in order to design remediation strategies for the most hazardous materials located at a particular site. Substances chosen for study include chlorinated hydrocarbons and toxic metals. The program consists of twelve projects (eight nonbiomedical, four biomedical) that are supported by four laboratory cores and administrative, outreach, and training cores.

Six projects center on bioremediation technologies with research involving collaborative efforts from the disciplines of engineering, microbiology, and soil sciences. One project focuses on biodegradation within metal and organic contaminated soils, and will use the biomarker assays developed in the project to document changes in the soil microflora following additions of contaminants to soil in field scale lysimeters. A comparative project is examining biosurfactant enhanced in-situ remediation of soils contaminated with metals. In another project, the influence of coupled physical chemical processes on bioremediation and biodegradation of organic compounds is being evaluated. One project investigates bacterial transport in saturated, unsaturated, and air-sparged porous media. Another project is directed toward development of abiotic and biotic systems for reductive dehalogenation of haloorganics in water. In a separate project, methane/air stimulation of bioventing for destruction of halogenated aliphatic compounds is being explored.

Risk assessment issues are emphasized in projects which concentrate on chemical transport and hazard identification. One project focusses on the transport of hydrophobic organic contaminants in the vadose zone. Another project is exploring non equilibrium transport of trace metals in polluted aquifers. Biomedical projects are in place to investigate the detoxification of metals and to analyze metal-metal interactions in the kidney. One project is examining the determination of toxic metal species in environmental and biological matrices. Another project highlights cardiac teratogenicity of trichloroethylene (TCE), dichloroethylene, and the resulting metabolites.

The outreach core centers on U.S.- Mexico health-related issues, primarily dealing with border environmental problems, and on increasing interactions with industry. Collaborating institutions include: Universidad Nacional Autonoma de Mexico, the Rocky Mountain Poison Center and Precision Lysimeters.