The success of the rapidly desorbing fraction as an available fraction was challenged by using sediment ingesting and noningesting oligochaetes (Lumbriculus variegatus) together with passive samplers (semipermeable membrane devices, SPMDs) in accumulation and kinetic modelling exercises for carbon-14 labelled model compounds (pyrene, benzo[a]pyrene and 3,4,'3',4'-tetrachlorobiphenyl). Passive samplers clearly produced lower uptake rate constants and stead state factors than either of the oligochaete treatments when residue concentrations were based on animal lipid or total SPMD weight, The rapidly desorbing chemical fractions in sediments did not show a significant relationship with the biota sediment accumulation factors or SPMD accumulation factors. A distinctly better relationship wits observed between the accumulation factors and the desorption rate constants. The results support the assumption that desorption plays an important role in bioavailability. although animal behaviour and the diffusional limitations of hydrophobic contaminants in sediment together probably affect the actual available Pool, (C) 2005 Elsevier Ltd. All rights reserved.
