Concentration of retene and resin acids in sedimenting particles collected from a bleached kraft mill effluent receiving lake

The concentration of retene, a di-alkyl substituted PAH derived microbially and thermally from dehydroabietic acid, eight resin acids and their derivatives were analysed from sedimenting particles collected from five lake sites receiving pulp and paper mill effluents and from two reference sites. At five of the sites, samples were collected prior and after a conventional aerated lagoon wastewater treatment system of the mill was modernized with an activated sludge plant, and elemental chlorine free bleaching (ECF) had replaced chlorine bleaching. The highest level of retene was 30.0–53.8 μg/g dry weight (d.w.), observed 3 km downstream from the mill. Nine kilometers downstream from the mill the concentration of retene was still 8.7–17.4 μg/g d.w., distinctly exceeding that of the upstream reference (0.2–4.4 μg/g d.w). The highest concentration of resin acids was 1474 μg/g d.w., the most abundant resin acid being dehydroabietic acid. The concentrations of retene and resin acids showed a distance related decrease downstream to a mill. The technology changes at the pulp and paper mill decreased both the sedimentation rate and the concentration of resin acids and retene in sedimenting particles. Presence of other resin derived neutral compounds (dehydroabietin, tetrahydroretene and fichtelite) in sedimenting particles was also revealed.