Retene (7-isopropyl-1-methylphenantrene) is an alkyl substituted PAH derived primarily from bacterial aromatization of abietic type resin acids. Retene has been shown to induce cytochrome P450 1A in rainbow trout whereas e.g. dehydroabietic acid does not induce it. We analysed resin acids and retene in sediments from seven sites receiving pulp and paper mill effluents from 4 mills, and from two reference sites. All mills have employed treatment of waste waters by activated sludge. The highest concentration of retene measured in sediment was 1600 μg/g d.w. (11 700 μg/g organic carbon, OC) while the highest concentration of resin acids was 1500 μg/g d.w. (9 300 μg/g OC). Downstream from the point (12 km) of bleached kraft mill effluent discharge, the concentration of retene at the depth of 5-10 cm in sediment was still 16 μg/g d.w. (650 μg/g OC) and the concentration of resin acids 139 μg/g d.w. (1700 μg/g OC). Background concentration for retene on the upstream reference site was below 0.1 μg/g d.w and for resin acids below 70 μg/g d.w. Substantial concentrations of retene (54 μg/g d.w.) and resin acids (1470 μg/g d.w.) were also detected in sedimenting particles collected at the sediment sampling sites. When the concentrations and sedimentation rates before and after the installation of activated sludge systems were compared, the effect of improved waste water treatment on total amount of sedimenting resin acids and retene (μg/m2/day) is clear. To assess the bioavailability of retene we analysed its concentration in the bile of feral fish caught 1-2 km downstream of pulp and paper mill. Data on roach shows that retene in sediments can be bioavailable to fish feeding on benthic food chain.

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