An equilibrium model of organic chemical accumulation in aquatic food webs with sediment interaction

Abstract A five-compartment steady-state food-web model is constructed that includes a benthic invertebrate compartment Four exposure routes are considered in the description of accumulation by benthic animals ingestion of particulate contaminants associated with (a) sediment organic carbon and (b) overlying phytoplankton and ventilation of free dissolved contaminant in (c) interstitial and (d) overlying water Normalization of organism lipid-based chemical concentration to sediment organic carbon (the biota sediment factor, BSF) or to overlying water concentration (the bioaccumulation factor, BAF) indicates the significance of the sediment/overlying water partition coefficient for systems that have a benthic component The impact of the benthic component on a forage fish is related directly to this partitioning Application of the model to an amphipod-scul pin web for Lake Ontario indicates (a) amphipod water exposure is a combination of interstitial and overlying water concentrations, (b) amphipod feeding appears to be a combination of overlying phy toplankton and sediment organic carbon, (c) amphipod and sculpin chemical assimilation efficiency appears to be a complicated function of octanol-water partition coefficient, (d) observed BAF for amphipod and sculpin is about one order of magnitude higher than log Kow in the range 5 5 to 7 0 and is calculated to be due almost entirely to food-web transfer from the sediment, as opposed to uptake from the water route