Toxicokinetics, toxicity and lethal body residues of two chlorophenols in the oligochaete worm, Lumbriculus variegatus, in different sediments Anna Nikkil€ a a, * , Anssi Halme b , Jussi V.K. Kukkonen b a Department of Biological and Environmental Science, University of Jyv€ askyl€ a, P.O. Box 35, FIN-40351 Jyv€ askyl€ a, Finland b Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland Received 19 November 2001; received in revised form 15 August 2002; accepted 7 November 2002 Abstract Bioavailability, toxicokinetics and toxicity (LC 50 ) of water- and sediment-associated 2,4,5-trichlorophenol (2,4,5- TCP) and pentachlorophenol (PCP) were measured in Lumbriculus variegatus M€ uller in a set of experiments. The critical body residue approach was applied by measuring also the lethal body residues (LBR 50 ). Freshwater and three different sediments with various sediment organic carbon (SOC) concentrations were used as exposure media. SOC decreased the bioavailability of both chlorophenols, and the uptake rates decreased by 81% and 91% for 2,4,5-TCP and PCP, respectively, in the sediment with a SOC of 6.9% compared to those in sediment with a SOC of 0.5%. SOC appeared to be an important factor controlling the bioavailability as after the carbon normalisation the difference between the sediments was much smaller. The 96-h LC 50 values for instance for PCP were 145.3 lg/l in freshwater, and 6.8 and 8.1 lg/g dry weight in sediments with SOC concentrations of 0.5% and 2.4%, respectively. The LBR 50 values, were practically the same in freshwater and sediments: between 1.0 and 1.6 and from 0.4 to 0.9 lmol/g wet weight for 2,4,5-TCP and PCP, respectively, demonstrating the usefulness of this method for accurate, and more comparable, measurement of toxicity of chemicals with the same mode of toxic action in varying conditions. L. variegatus expressed a dose–response sediment avoidance behaviour but the PCP tissue concentrations were not affected by this behaviour. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Bioavailability; Depuration; Lethal body residue; Oligochaetes; Pentachlorophenol; 2,4,5-trichlorophenol; Sediment 1. Introduction Chlorophenols are harmful to aquatic life because of their capability to become bioaccumulated and cause toxicity (Coulston and Kolbye, 1994). Due to their rel- atively high lipophilicity, they are often also sorbed by the organic matrix of particles and tend to remain as- sociated with sediments, this resulting on the one hand into reduced bioavailability and on the other hand into longer lasting contamination of recipient areas. Various kinds of use of chlorophenols in the 20th century over many decades raised concern over their potentially adverse effects on freshwater biota and the environment some 20 years ago. Chlorophenols, in- cluding the two used as model compounds in this study, 2,4,5-trichlorophenol (2,4,5-TCP) and pentachlorophe- nol (PCP), have been used as fungicides and other pes- ticides, and wood preservatives, as well as for other industrial, agricultural and commercial uses (Coulston and Kolbye, 1994; Lampi, 1996). They can also be formed during the chlorine bleaching of pulp in pulp and paper mills (Coulston and Kolbye, 1994). The Chemosphere 51 (2003) 35–46 www.elsevier.com/locate/chemosphere * Corresponding author. Tel.: +358-14-612914; fax: +358-14- 2602321. 0045-6535/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. PII:S0045-6535(02)00791-9