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Two independent investigators reported that humic substances in the aquatic environment decrease the bioconcentration factors and uptake rates for hydrophobic compounds. This is quantitatively explained in terms of rapid, reversible binding and slow, irreversible binding by humic matter. The type of humic matter determines, among others, the extent of binding. Irreversibly bound compounds were found not to be available for uptake. It was suggested, based on data for concentrations of PAH in sediment and water, that combustion derived products (e.g. PAH and dioxins) may be present in sediment in high concentrations but that their concentrations in water may be lower than estimated from their n-octanol-water partition coefficients because of reduced availability. Also compound properties other than hydrophobicity determine uptake rates. Large molecules, with chain lengths of more than 4.3 nm or cross-sections of more than 0.96 nm were found not to be taken up by fish. An example was given of a dioxin for which the lethality to goldfish was decreased as a result of metabolism. These, and many other, processes in the environment are integrated in models to estimate concentrations of micropollutants in the environment. An evaluation of the comparison of the EXAMS model and a fugacity model was performed with data on chloroform and some chlorinated hydroxybenzenes in a Scandinavian bay. There was a good agreement between the data and the predictions except for a tetrachlorocatechol. The reason for this exception is thought to be higher sorption by sediment than predicted by the n-octanol-water partition coefficient along with a poor representation of sedimentation in the models. An overview was given of the analytical efforts on PAH and PCBs in Belgium. Models for the estimation of environmental concentrations of micropollutants are useful for the assessment of new chemicals. A presentation demonstrated the use of these models in Germany for the assessment of notified chemicals.

Additional information

Bibliographic Reference: EUR 11357 EN (1987) MF, PP 61, ECU 4.00, BLOW-UP COPY, ECU 8.75, EUROFFICE, LUXEMBOURG, BP 1003, GDL
Availability: Can be ordered online
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