PW20 New Approaches to Determining Soil and Sediment Exposures
Exhibit Hall
8:00 AM - Wednesday
(PW290) A method to measure the fugacities of hydrophobic organic contaminants in spiked and field-collected sediments.
Meloche, L1, Otton, V1, Ikonomou, M2, Gobas, F1, 1 School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada2 Institute for Ocean Sciences, Department of Fisheries and Oceans, Sidney, British Columbia, Canada
ABSTRACT- It is increasingly recognized that the total concentration of organic chemicals in sediments is a poor predictor of the ability of sediment bound chemicals to bioaccumulate or cause toxicity. Many studies have concluded that only a fraction of the total concentration, i.e. the bioavailable fraction, is available for uptake and has the potential to cause toxicity. We hypothesize that the fugacity is a better measure of the bioavailable concentration in sediments than the total concentration in the sediments. Unfortunately, a practical method to measure the fugacity of chemicals in sediment does not exist. In this study, we present a method, based on thin-film solid-phase extraction, to measure the fugacities of hydrophobic organic contaminants in sediment samples. The method involves placing sediment in vials coated with the solid phase extracting medium, ethylene vinyl acetate (EVA). We applied this method to measure the fugacities of chlorobenzenes and polychlorinated biphenyls (PCBs) in two different sediments that were spiked in the laboratory and in field sediment collected from Sydney Harbour, Nova Scotia. Results indicate that the method is reproducible, with coefficients of variation for triplicate extractions averaging 6.6% for the spiked sediment experiments and 7.8% for the field sediment experiment. Time to reach 95% equilibrium (t95) ranged from 3.4 to 492 hours. Uptake rate constants were negatively correlated to the octanol-water partition coefficient for congeners in the field-collected sediment, and for chemicals in the spiked sediment experiments. The effect of ageing was examined by comparing the equilibrium EVA concentrations from spiked sediments aged for different periods. A significant decrease in available concentration was observed for the chlorobenzenes and two PCB congeners (PCB 26 and PCB 52) in the spiked Robert's Bank sediment. We conclude that this method provides a simple and relatively rapid means to approximate chemical bioavailability in sediment.
Key words: fugacity, bioavailability , hydrophobic organic contaminants, equilibrium sampling device