Bioaccumulation of persistent organic chemicals: mechanisms and models

PCB problems in the future: Foresight from current knowledge

The present study examines a new bioaccumulation model for hydrophobic organic chemicals in aquatic food webs. The purpose of the model is to provide site-specific estimates of chemical concentrations and associated bioconcentration factors, bioaccumulation factors, and biota-sediment accumulation factors in organisms of aquatic food webs using a limited number of chemical, organism, and site-specific data inputs. The model is a modification of a previous model and incorporates new insights regarding the mechanism of bioaccumulation derived from laboratory experiments and field studies as well as improvements in model parameterization. The new elements of the model include: A model for the partitioning of chemicals into organisms; kinetic models for predicting chemical concentrations in algae, phytoplankton, and zooplankton; new allometric relationships for predicting gill ventilation rates in a wide range of aquatic species; and a mechanistic model for predicting gastrointestinal magnification of organic chemicals in a range of species. Model performance is evaluated using empirical data from three different freshwater ecosystems involving 1,019 observations for 35 species and 64 chemicals. The effects of each modification on the model's performance are illustrated. The new model is able to provide better estimates of bioaccumulation factors in comparison to the previous food web bioaccumulation model while the model input requirements remain largely unchanged.

A food web bioaccumulation model for organic chemicals in aquatic ecosystems.

EDITOR'S NOTE: This paper represents 1 of 9 papers generated from a SETAC Pellston Workshop entitled “Science-Based Guidance and Framework for the Evaluation and Identification of PBTs and POPs,” (January 2008, Florida, USA). The workshop objectives were to develop guidance and recommendations on the evaluation of substances fulfilling PBT and POP criteria, using scientific information such as experimental and monitoring data, and computer models. Scientists from academia, industry, and government reviewed current international regulations for the screening of commercial chemicals for bioaccumulation in the context of the current state of bioaccumulation science. On the basis of this review, several recommendations were proposed, including a scientific definition for “bioaccumulative substances,” improved criteria for the characterization of bioaccumulative substances (including the trophic magnification factor and the biomagnification factor), novel methods for measuring and calculating bioaccumulation p...

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Revisiting bioaccumulation criteria for POPs and PBT assessments.

The trophic structure of pelagic communities in lakes of glaciated regions is highly variable due to restricted dispersal of glacial relict taxa and recent species introductions. Much of the enormo...

Food chain structure in Ontario Lakes determines PCB levels in lake trout (Salvelinus namaycush) and other pelagic fish

The dynamics of DDT in lentic environments were studied in a farm pond and four artificial pools. A hypothesis that biological magnification of pesticides was dependent on passage of the residues through a food chain was rejected and a hypothesis that accumulation depends on adsorption and solubility differences was proposed. The mechanism proposed is based on the principle that compounds are exchanged between water and fats. Exchange in fish passes through two stages, from water to blood and from blood to fats, permitting a high degree of magnification in fish. The proposed mechanism accounts for the reported observations that pesticides are excreted by fish, that body load of pesticides increases as the fat content of fish increases, that pesticide magnification by fish is inverse to the water solubility of the compounds and that pesticides persist longer in oligotrophic than eutrophic lentic ecosystems.

Jerry L. Hamelink

Papers

A Proposal: Exchange Equilibria Control the Degree Chlorinated Hydrocarbons are Biologically Magnified in Lentic Environments