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(430) PAH uptake: influence of molecular weight, organism size and tissues in marine organisms.
Skadsheim, Arnfinn*,1, Jonsson, Grete1, Aas, Endre1, 1 RF-Rogaland Research, Stavanger, Norway
ABSTRACT- In aquatic systems oil is a lipo- or petrophilic hydrocarbon source, tissues of organisms a lipophilic hydrocarbon sink, and the intervening water is the lipophobic medium through which hydrocarbons have to pass from source to sink. PAH molecular weight influences uptake rates, concentration levels and effects in organisms. However, also organism size, organism building complexity and lipid density (as weight per cent) of tissues influence body burden and effects. At similar exposures to water dissolved PAH mixture from oil we found that the proportion of large molecular weight PAH increased as part of total body burden when organism size was reduced. Total body burden concentration was also influenced by organism size. The results reflect a change from within body dynamics to surface related processes. They are explained by PAH partitioning between water and organic tissue. The smallest organisms are frequently the most sensitive ones in acute toxicity tests. However, compared to the focus on the sensitivity of different species, the profound impact that organism size alone has on uptake and effects of lipophilic substances is not adequately dealt with in aquatic environmental assessments. Finding increased uptake of the most water-soluble PAH in organisms as gill ventilation efficiency increased, triggered uptake and effect studies in small fish by exposure to finely dispersed oil. PAH molecular weight, lipid density and tissue type influenced PAH profiles and concentrations in skin, muscle and liver. The gross qualitative PAH profile was rapidly established, but PAH molecular weight dependent uptake patterns were found with exposure concentration and exposure time. The utility of lipid normalisation may be questioned because sum PAH per weight unit lipid increased with per cent lipid content in tissue. Elucidation of the dynamic PAH partitioning in tissues might guide interpretation of repeated and fluctuating exposures as well as effect expression. Models covering tissue and organism size related properties have to be developed for appropriate predictions of PAH bioconcentration in aquatic organisms.
Key words: PAH, bioconcentration, organism size, tissue lipids
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