Bioaccumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzofuran and extractable organic chlorine at a bleached-kraft mill site in a northern Canadian river system

Abiotic and biotic environmental compartments in a northern Canadian river system have been analyzed for poly-chlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and extractable organochlorines (EOCl) down-stream of a bleached-kraft mill. The water column, deposited and suspended sediments, invertebrates, and tissues from several fish species were analyzed. The data indicate that (a) conversion of the mill bleaching process to 100% chlorine dioxide virtually eliminated the discharge of PCDDs and PCDFs; (b) PCDD, PCDF, and EOCl transport occurred primarily in suspended sediments; and (c) the food choice of filter-feeding insects by specific fish species such as the mountain whitefish (Prosopium williamsoni) was an important determinant in the food-chain transfer of the principal compounds, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF). Relative to mountain whitefish, TCDD and TCDF levels in another bottom feeding species, longnose sucker (Catostomus catostomus), were at least an order of magnitude lower. Food-chain biomagnification of TCDD and TCDF was not observed in omnivorous and predatory species, burbot (Lota lota) and walleye (Stizostedium vitreum), for which lipid-adjusted levels were similar to those in the longnose sucker. These data indicate that organism lipid levels alone are not sufficient to predict species-specific bioaccumulation of these hydrophobic compounds, and that site-specific transport and species foodmore » choice parameters should be included in bioaccumulation models for hydrophobic compounds such as PCDDs and PCDFs.« less