Bioaccumulation of lindane and hexachlorobenzene by tubificid sludgeworms (Oligochaeta) under standardised laboratory conditions

Lipophilic chemicals released into the aquatic environment tend to adsorb to suspended material and sediments. These compounds are therefore not bioavailable to many pelagic organisms, and their overall bioaccumulation is often not adequately covered by the currently prescribed measuring of bioconcentration in fish. The assessment of bioaccumulation in sediment-dwelling organisms shall give more detailed information on the hazard of chemicals for aquatic ecosystems. Therefore a standardised test design is required. The freshwater tubificids Tubifex tubifex and Limnodrilus hoffmeisteri were chosen as test organisms, while 14C-Lindane (γ-Hexachlorocyclohexane, γ-HCH), and 14C-Hexachlorobenzene served as test substances. The bioaccumulation studies were carried out in a static system consisting of artificial sediment and reconstituted water. Uptake as well as deputation phases were examined. Bioaccumulation factors (BAF) were determined from the ratio of concentration in worm tissue to concentration in sediment, and from the ratio of uptake rate constant (ks) to elimination rate constant (ke), respectively. Lindane concentrations were found to be about 4 times higher in the worms compared to the sediment, HCB was accumulated by a factor of approximately 7. The tubificid bioaccumulation factors of Lindane and HCB are discussed in comparison to corresponding fish bioconcentration data from lieterature. The presented data show that the assessment of bioaccumulation based exclusively on the extrapolation of fish-BCF to other organisms and environmental compartments is not appropriate.