BIOAVAILABILITY OF HEXABROMOCYCLODODECANE TO THE POLYCHAETE HEDISTE DIVERSICOLOR: EXPOSURE THROUGH SEDIMENT AND FOOD FROM A CONTAMINATED FJORD

摘要

Knowledge of the bioavailability of brominated flame retardants for sediment-dwelling organisms is limited. The present study investigated bioaccumulation of hexabromocyclododecane (HBCD) in the ragworm Hediste diversicolor exposed to field-contaminated sediments and food. Sediments and blue mussels (Mytilus edulis) were sampled from a fjord on the Norwegian west coast known to be highly contaminated with the brominated flame retardant HBCD. During a four-week experiment, ragworms were either exposed to sediment containing moderate or high concentrations of HBCD, or they were fed contaminated soft tissue from mussel. Although mean sediment concentrations were as high as 40ug/g dry weight in the contaminated sediments, no HBCD were detected in the exposed ragworms (detection limit up to 2.0ug/g wet wt). In contrast, the exposure to contaminated food (mussel) resulted in elevated body concentrations of 9.1 ng HBCD/g wet weight. The partitioning of HBCD in the test-sediments appeared to be influenced by the quantity and quality of the sediment organic matter (up to 15% total organic carbon). The presence of small plastic beads (<2mm), which were shown to contain a mean of 50ug/g dry weight of HBCD, could explain the low bioavailability of the flame retardant in the sediment. Hexabromocyclododecane in food appeared to be readily assimilated in the ragworm, however, and the diastereomer pattern indicated a relative increase of α-HBCD from mussel to ragworm. Hence, in the sampled areas of the fjord, trophic transfer appeared to be a more important mechanism for the entry of HBCD into the local benthic food web than sediment-to-biota accumulation.