W11 AM Environmental Chemical Forensics
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 343-344

(MUR-1118-171018) Forensic Methods for Chlorinated Solvents.

Murphy, B¹, Mohsen, F², ¹ Exponent, Sarasota, FL, USA² Exponent, Cranbury, NJ, USA

ABSTRACT- This presentation describes several ways of age-dating and identifying sources of chlorinated solvents such as 1,1,1-trichloroethane (TCA), trichloroethene (TCE) or perchloroethene (PCE). Examples of the methods and use including complicating factors and uncertainties are also given. Age dating methods include the following. (1) Using the position of a ground water plume front together with a contaminant velocity estimate and an adjustment for longitudinal dispersion. (2) Using the observed ratio of TCA to its hydrolysis product, 1,1-dichloroethene, together with a groundwater temperature estimate and a laboratory evaluation of the hydrolysis rate at this temperature. Source identification methods include the following. (3) Plotting parent-daughter ratios in ground water, such as TCE /1,2-dichloroethylene, versus distance to identify additional chlorinated solvent sources. (4) Source identification using isotopes.

Key words: solvents, forensics, TCE, TCA