Toxic Substances Hydrology Program
Chlorinated Solvents Contamination
Chlorinated solvents have properties that make them useful for degreasing fats, oils, waxes, and resins. They are used widely and have been manufactured in large quantities. Some chlorinated solvents are dichloromethane, tetrachloroethene, trichloroethane, and tricholoroethene. The U.S. production of these compounds in 1980 were 255,000, 347,000, 314,000, and 121,000 metric tons, respectively.
Chlorinated solvents in general are harmful to human and ecological health. They can cause or are suspected of causing cancer, and are toxic or harmful to aquatic organisms.
Spills and leaks of chlorinated solvents have caused widespread subsurface contamination in the environment. Commonly these contaminants are present in the subsurface in the form of non-aqueous phase liquids (NAPL, the bulk chemical product), as dissolved contaminants in ground water, associated with aquifer sediments, and as vapors in the unsaturated zone. Because the density of these NAPL’s is greater than water, they tend to sink in ground water systems, which results in a complex dispersal and plume patterns, long-term sources in the subsurface, and difficult clean-up. Under the proper conditions, biodegradation and volatilization can contribute significantly to the removal of chlorinated solvents from the subsurface, making natural attenuation a potentially important remediation alternative.
The project activities undertaken fall into 2 general categories: Plume-scale research at representative contamination sites, and research on microbial degradation pathways for chlorinated solvents. More information is provided on these activities as follows:
Plume-Scale Research at Representative Contamination Sites
Microbial Degradation Pathways for Chlorinated Solvents
Program Headlines Related to Chlorinated Solvents Contamination