ROCK FRAGMENTS IN TCE MICROCOSMS FOR BEDROCK AQUIFERS

Trichloroethene (TCE) is an organic solvent that has been linked to significant human health effects at low concentrations in potable water. Because TCE is heavier than water and recalcitrant to degradation in most environments, it will often contaminate fractured bedrock aquifers when released. TCE microcosms are needed to evaluate fractured rock aquifers because biodegradation is one of the few potentially effective ways to remediate TCE in fractured rock and, because there typically are few bedrock monitoring wells at a TCE release site, microcosms provide an accessible and reproducible method to assess biodegradation potential.

The purpose of this study was to evaluate microcosm methods that can be used to predict the in situ anaerobic reductive dechlorination of TCE in bedrock aquifers, in biotic intrinsic (i.e., microcosm conditions that simulate in situ conditions without amendment or adjustment) and biotic amended (i.e., microcosm conditions that are amended to stimulate growth) preparations compared to abiotic preparations using a TCE contaminated fractured bedrock as a model. The effect of granular media in the microcosms as a growth surface and nutrient source was also assessed. The effect of in situ incubation of granular media was further assessed by comparison of media incubated for 45 days in a groundwater well within a TCE plume and sterilized media. Effects were evaluated by comparison of TCE concentrations between microcosms prepared with different initial conditions but incubated and sampled under conditions consistent across all preparations and treatments.