CONCENTRATION OF RETENE AND RESIN ACIDS IN SEDIMENTING PARTICLES COLLECTED FROM A BLEACHED KRAFT MILL EFFLUENT RECEIVING LAKE H. LEPPA È NEN 1 *, J. V. K. KUKKONEN 2M and A. O. J. OIKARI 1 1 University of JyvaÈskylaÈ, Department of Biological and Environmental Sciences, P.O. Box 35, Fin- 40351 JyvaÈskylaÈ, Finland and 2 University of Joensuu, Department of Biology, P.O. Box 111, Fin-80101 Joensuu, Finland (First received 1 February 1999; accepted in revised form 1 July 1999) AbstractÐThe 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 ®ve lake sites receiving pulp and paper mill euents and from two reference sites. At ®ve 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 mg/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 mg/g d.w., distinctly exceeding that of the upstream reference (0.2±4.4 mg/g d.w). The highest concentration of resin acids was 1474 mg/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 ®chtelite) in sedimenting particles was also revealed. # 2000 Elsevier Science Ltd. All rights reserved Key wordsÐBKME, retene, resin acids, particles, sediment, waste water treatment INTRODUCTION Retene (7-isopropyl-1-methylphenantrene) is a poly- nuclear aromatic hydrocarbon (PAH) that has been found in sludge of the aerated wastewater stabilis- ation basin of pulp and paper mills and in high concentrations in sediments downstream of pulp and paper industry (Zender et al., 1994; Koistinen et al., 1998; LeppaÈnen and Oikari, 1999). In sedi- ments retene is believed to be formed by anaerobic microbial transformation of dehydroabietic acid (Tavendale et al., 1997a,b). Since retene is hydro- phobic (log K ow 0 6) (Burnison et al., 1996) it is likely adsorbed to suspended solids during biologi- cal wastewater treatment and in receiving aquatic environment. Recent studies on embryo-larval stages of zebra®sh and rainbow trout show that subchronic exposure to retene causes exposure-re- lated increases in the prevalence of (chemically induced) blue sac disease, a disease originally described for persistent chlorinated compounds, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (Billiard and Hodson, 1998). The common factor for retene and dioxin-exposed ®sh is prolonged induction of mixed function oxygenase (MFO) activity due to either continued exposure (retene) or chemical per- sistence (dioxin) (Fragoso et al., 1998). This far, based on several eects, the threshold concentration approximates 16±32 mg/L waterborne retene, but even lower concentrations were observed to cause ®n necrosis and opercular loss, which might cause death of larval ®sh due to subsequent bacterial or fungal infection (Billiard et al., 1997). In developing embryos of Paci®c herring the LOEC value for ede- mic yolk sac and pericardium approximates 10 mg/L (Oikari, 1999). The bioavailability of retene to feral benthic ®sh was recently demonstrated (LeppaÈnen and Oikari, 1999). Resin acids, a group of diterpene wood extrac- tives, are very abundant in canal resin of coniferous trees (50% of canal resin of spruce consists of resin acids) (SjoÈstroÈm, 1993). They are commonly found in pulp and paper mill euents, waters receiving euents (Kaplin et al., 1997; LeppaÈnen et al., 1998) and adjacent sediments (Lee and Peart, 1991; Wat. Res. Vol. 34, No. 5, pp. 1604±1610, 2000 # 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0043-1354/00/$ - see front matter 1604 www.elsevier.com/locate/watres PII: S0043-1354(99)00313-9 *Author to whom all correspondence should be addressed. Tel.: +358-14-602-335; fax: +358-14-602-321; e-mail: hjleppan@tukki.jyu.®