The fate of resin acids and resin acid-derived compounds in aquatic environment contaminated by chemical wood industry

Abstract

Because of the transition of pulp manufacturing technology from chlorine bleaching to elemental chlorine free and total chlorine free bleaching processes, more attention has been drawn to wood-derived and other non-chlorinated compounds in treated discharges from pulp mills. The occurrence of resin acids and resin acid-derived base neutrals, particularly retene (7-isopropyl-1-methylphenanthrene) in sediments and sedimenting particles in lake areas polluted by mill effluents was studied in this work. At Southern Lake Saimaa substantial concentrations of these substances were observed in sedimenting particles (highest concentration of retene and resin acids 54 and 1500 μg/g d.w., respectively). High concentrations were also observed in sediments of both industrial areas studied (at Southern Lake Saimaa 1600 and 1500 μg/g d.w. of retene and resin acids, respectively; at Lake Lievestuoreenjärvi 3300 and 1100 μg/g d.w.). In an anaerobic incubation of a sedimental microbial consortium spiked with dehydroabietic acid, the amount of dehydroabietic acid decreased and the amount of retene increased at 24 °C, indicating the biotransformation of the former to the latter. At 4 °C no changes were observed over a one year of incubation. Under aerobic conditions the concentrations of both retene and dehydroabietic acid decreased. In order to assess the bioavailability of the lipophilic, apparently particle-bound retene to fish we analysed bile samples of feral perch (Perca fluviatilis) and roach (Rutilus rutilus) caught downstream of the pulp mill sewer in an area with high concentrations of retene in the sediment and from the reference area upstream from the mill. Retene was found in the bile of roach, but not in the bile of perch caught downstream of the mill, indicating that retene is bioavailable to benthic fish species. We also studied the utility of fish bile analysis in experimentally exposed whitefish (Coregonus lavaretus) to assess the exposure of fish to elemental chlorine free bleached, biologically treated pulp and paper mill effluents and evaluated the most suitable compounds for tracers. The results revealed that the bleaching-derived chlorinated phenolics still are the most suitable tracers of exposure to bleached kraft mill effluent.