Abstract
This article discusses a method for identifying sources of chlorinated solvent releases without the need to formulate site-specific degradation rates. Instead, converting measured concentrations of daughter products to equivalent concentrations of parent products furnishes the needed information. The method is illustrated with a case study, and consists of two parts: 1) developing a picture of what the plume would have looked like if biodegradation and hydrolysis had not occurred, and 2) factoring in what is known about groundwater flow direction. The relevance of this method for identifying areas where biodegradation has occurred and for age-dating plumes is also discussed.
Notes
1For example, 23 of 41 sites in EPA's vapor intrusion database have TCE (US EPA 2008). The chemical with the second highest number of sites is PCE with 14. The TCA breakdown product 1,1-dichloroethylene is found at eight of the 41 sites.
1New Jersey Department of Environmental Protection, 2005);
2Assuming fraction of organic carbon (foc) = 0.002, porosity (n) = 0.3, bulk density (ρ b) = 1.7;
3TCE is the parent for cis- and trans-1,2-DCE; vinyl chloride and TCA form the parent for 1,1-DCE, 1,1-DCA and chloroethane.