Bioaccumulation of 2,3,7,8‐tetrachlorodibenzo‐P‐dioxin in feral fish collected from a bleach‐kraft paper mill receiving stream

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Abstract
Bleach‐kraft mill (BKM) processes may result in the formation and release of a number of chlorinated organic compounds, including 2,3,7,8‐tetrachIorodibenzo‐p‐dioxin (TCDD). Contamination of aquatic ecosystems by TCDD is of concern due to the chemical's toxicity, bioaccu‐mulation potential, and persistence in the environment. Sediment samples and tissues from three species of fish and one invertebrate were collected downstream from a BKM facility and were analyzed for TCDD. Concentrations of TCDD were greatest in the bowfin, particularly in the ovary of a gravid female (46.1 pg/g). There appeared to be no correlation between either trophic position or habitat classification (i.e., epibenthic or pelagic) and TCDD tissue concentrations. Sediments collected near the mill outfall contained elevated levels of TCDD as great as 52.8 ppt. Sediment‐based BAFs and lipid‐ and carbon‐normalized bioavailability indexes (BI) were calculated for the fish livers and gonads, and blue crab hepatopancreas. BAF*s varied by a factor of 27, depending on species and organ, whereas Bis had an approximate seven‐fold variation. It appears that organic carbon‐and lipid‐normalization factors may be more accurate predictors of the extent of bioaccumulation in resident biota from TCDD‐contaminated sediments than either BAF*s or BCFs. As there is currently only a limited understanding of species variability in absorption and deposition of TCDD, a more accurate estimation of TCDD levels in feral fish tissues may not be possible.