The Theory of Accumulation and its Relationship to the Choice of Monitoring Matrices for Dioxins

Abstract

There now exists a sufficient body of theoretical knowledge to translate an environmental input into a matrix concentration. The chemical dynamics of an environmental contaminant will depend on first, the physico-chemical properties of the chemical and secondly, the properties of the different ecosystem compartments. In the case of dioxins in aquatic systems, the combination of a few fundamental measurements such as molecular weight, vapor pressure, solubility, quantum yield, and octanol-water partition coefficient can be used to predict a chemical’s fate and persistence patterns in water, sediments, and biota. While their low water solubility combined with their high octanol-water partition coefficient indicate a high affinity for sediments and biota, theory predicts that the pattern should be homologue specific and a wide range of accumulation patterns should be observed. Even though one would predict that sediments would have a much higher concentration than the biota at equilibrium, the theory of sediment sorption versus that for bioaccumulation suggests that the equilibrium would be reached only after a long period of time. Consequently, in the short-term, biota could be a more appropriate monitoring matrix. Additionally, the bioaccumulation potential of various types of organisms can be modelled on the basis of their metabolic requirements. Thus, because fish depend on water to satisfy their respiratory requirements, they appear more likely to be useful indicators of aquatic contamination than organisms higher on the food chain.