HR: 0830h
AN: H11D-0887    [PDF]
TI: Field Sampling and Modeling of Creosote-Derived Contamination in a Tdally Forced Aquifer
AU: * Bishop, C
EM: cbishop@eos.ubc.ca
AF: University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4 Canada
AB: We are investigating the fate and transport of a creosote-derived groundwater contaminant plume found in an aquifer adjacent to and beneath a large, tidally forced river. The site, located in Coquitlam, BC, is adjacent to the Fraser River, and has been an active wood preserving facility since the 1920's. In the on-shore source zone, creosote has penetrated into the aquifer and a dissolved-phase plume, composed primarily of naphthalene, flows in the site aquifer from the source zone towards and below the river, eventually discharging from the river bottom. A capture well has been operated since 1996 to contain and capture the contaminant source. Previous research at this site has documented that biodegradation of naphthalene takes place in the plume fringe in the region of the aquifer that is beneath the river, but not onshore. Abundant methane and ferrous iron in the aquifer suggests that iron reduction and methanogenesis are the dominant terminal electron accepting processes. High offshore naphthalene concentrations sampled in 1999 despite three years of source containment and degradation led to the hypothesis that the plume may be at steady state due to buffering of contaminant concentrations by desorption from aquifer sediments. Naphthalene concentrations sampled in this study show that the contaminant plume is not at steady state. Results of groundwater flow modelling and sorption data show that the continued presence of high concentrations of naphthalene offshore are likely due to incomplete source containment or to slow migration of contaminants from upgradient regions of the aqueous plume. Although naphthalene has been the focus of all previous investigations of the offshore plume at this site, recent sampling shows that two other components of creosote, indane and benzothiophene, become the dominant components of the aqueous phase plume as it approaches the discharge point. Significant concentrations of these contaminants are likely discharging to the river. Relative enrichment of these compounds along the plume profile, despite their lower sorptive properties and therefore greater susceptibility to tidally-driven mass loss, suggests that these components are not biodegraded to the same degree as naphthalene.
DE: 1803 Anthropogenic effects
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting