| Trichloroethene (TCE) was used extensively at several locations at the Santa Susana Field Laboratory (SSFL), near Simi Valley, California, between 1948 and 1995. During that time it is estimated that up to 500 000 gallons of immiscible-phase TCE may have been released at 15 locations into the fractured interbedded sandstone and shale underlying the site, including 6 rocket test stands. Dense non-aqueous phase liquid (DNAPL) at the site has since disappeared due to dissolution and matrix diffusion. The contaminant mass now exists as plumes with contaminant transport in the fractures with nearly all dissolved and sorbed mass residing in the low-permeability rock matrix. The identification of cis-dichloroethene (cDCE), trans-dichloroethene (tDCE), and 1,1-dichloroethene (1,1-DCE) by Hurley (2003) in the rock matrix at the SSFL provides the first evidence of TCE degradation in fractured sandstone. Historical aqueous concentration data from monitoring wells indicate the presence of cDCE, t-DCE, 1,1-DCE, and vinyl chloride (VC) in the groundwater, however the trends in time do not provide evidence for the degree of TCE dechlorination. In this study, stable carbon isotopes of TCE and cDCE were used to identify and quantify degradation. (Abstract shortened by UMI.)... |
