Silicone rubber passive samplers for measuring pore water and exchangeable concentrations of polycyclic aromatic hydrocarbons concentrations in sediments.

The use of a silicone rubber passive sampler for the assessment of the availability of lipophilic organic contaminants in sediments is described. The passive sampler accumulated polycyclic aromatic hydrocarbons (PAHs) from sediments with an equilibration time of 20 days for most PAHs. The method was used to measure the free dissolved concentrations in pore water of 30 PAHs (parent and alkylated), their water exchangeable concentrations and sediment-water partition coefficients in field sediments from a Scottish sea loch that supports fish farming. Fluoranthene and pyrene dominated the PAH concentration composition in the pore waters. The water exchangeable concentration reflected the pyrogenic pollution pattern found in the sediments and indicated that a proportion of the PAHs were not available for exchange with the aqueous phase. Strong linear relationships between organic carbon normalised sediment-water partition coefficients (logK(oc)) and corresponding octanol-water partition coefficients of PAHs were obtained. The logK(oc) values obtained are on average, 0.6 log units higher than literature values commonly used in sediment risk assessments, consequently direct measurements of logK(oc) in field sediments should be used to improve the reliability of risk assessments.