Studies at numerous sites have shown high variability in the degradation rates of chlorinated solvents as measured by microcosm studies with <sup>14</sup>C labeled contaminants. The ability of nutrient and carbon additions to stimulate degradation can vary widely. Although some of these variations can be related to the structure of the extant microbial community, the presence of other less refractory contaminants may be critical fctors impacting the rate of chlorocarbon mineralization. Relaatively highe rates of TCE degradation have been observed in the DOE K-25 burial grounds with diverse organic loadings as well as in areas that show evidence for hydrocarbon contamination. Similarly, at other sites where there was TCE in the absence of hydrocarbons or other contaminants, the measured degradation rates have often been found to be very low. At various other sites, the intrasite variability in degradation rates appeared to be related to the presence of hydrocarbon contamination. The highest rates were observed at sites with evidence of hydrocarbons. These observations indicated that the viability of natural attenuation as a remediation option for chlorinated solvents might depend in part on the presence co-contaminants such as hydrocarbons or natural matter.
Date: April 19, 1999
Creator: Kinsall, B.L.; Palumbo, A.V.; Pfiffner, S.M.; Phelps, T.J. & Salpas, P.
This research hypotheses is: (1) Indigenous microorganisms in the shallow aquifer at the FRC have the capability to reduce U(VI) and Tc(VII) but rates are limited by--Scarce electron donor, Low pH and potentially toxic metals, and High nitrate. (2) U(VI) and Tc(VII) reduction rates can be increased by--Successive donor additions, Raising pH to precipitate toxic metals, and Adding humics to complex toxic metals and serve as electron shuttles.
Date: March 17, 2004
Creator: Istok, J.; Jones, J.; Park, M.; Sapp, M.; Selko, E.; Laughman, R. et al.