Sorption and the Ecological Risk Assessment of Nonionic Organic Contaminants pp. 117-148
Authors: (A.P.K. Jantunen, Laboratory of Aquatic Ecology and Ecotoxicology, Department of Biology, University of Eastern Finland, Joensuu Campus, Finland)
Abstract: Sorption to solid matter affects the mobility, bioavailability and toxicity of organic pollutants in the environment. Such chemicals are bound to both organic and inorganic components of soils and sediments through various absorption and adsorption phenomena, and the tightness of the binding and, consequently, the bioavailability of the chemical vary according to the properties of both the compound and the solid materials it comes to contact with. Ecological risk assessments generally assume that nonionic, lipophilic organic chemicals partition linearly between water and organic material and that equilibrium partitioning applies and therefore the concentrations of the chemical in the organic fraction of solid matter and the storage lipids of organisms feeding on it are approximately the same. This assumption can, however, lead to either underestimation or overestimation of aqueous concentrations, bioaccumulation and toxicity due to, e.g., the variable sorptive properties of organic materials of different origin and maturity, some of which adsorb nonpolar organic contaminants very tightly. Additionally, beyond the fairly well characterized tight binding of planar aromatic compounds to carbonaceous geosorbents ("black carbon"), specific properties of chemicals other than their lipophilicity and specific, particularly inorganic, fractions of the solid matter which may result in tight sorption and reduced bioavailability remain to be recognized. Depending on the nature of the risk assessment, exposure assessment which takes the effects of sorption properly into consideration may be performed by directly measuring bioaccumulation from the contaminated material to a suitable organism in situ or in laboratory, by measuring the concentration of the chemical or extracting it from the material in such a way that the result has a predictable relationship with the bioavailability of the chemical to relevant organisms, or by modeling the environmental partitioning and bioaccumulation of the chemical using more or less basic information, data and assumptions concerning the properties of the chemical and the environmental conditions.
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