A food chain model of 2,3,7,8-tetrachlorodibenzofuran bioaccumulation in a northern Canadian river system

Field data from a comprehensive study of chemical contaminants including polychlorinated dibenzofurans provided the opportunity for comparison of predicted and observed concentrations in fish and invertebrates in sediment-invertebrate-fish food chains. The field study was from the Athabasca River downstream of a bleached-kraft pulp mill in northwest Alberta, Canada. The food chain model used predator-prey relationships which resulted in distinct exposure pathways for fish inhabiting the river. The model distinguished between exposure to suspended and deposited sediments in the Athabasca River. Concentrations of 2,3,7,8-tetrachlorodibenzofuran (TCDF) in two bottom feeding fish species, mountain whitefish (Prosopium williamsoni) and longnose sucker (Catostomus catostomus), and one piscivorous fish species, northern pike (Esox lucius), as well as in invertebrates were measured in the field samples. A sensitivity analysis revealed that exposure of mountain whitefish to TCDF sorbed to suspended solids through consumption of filter feeding invertebrates was the primary exposure pathway. Furthermore, failure to consider consumption of bottom sediments by longnose sucker resulted in underpredicted tissue concentrations compared to observed values.