Dissolution of sedimentary polycyclic aromatic hydrocarbons into the lugworm's (Arenicola marina) digestive fluids

We studied the mechanism(s) by which a deposit feeder can solubilize PAH fr om contaminated sediments as well as the implications of these mechanisms f or factors controlling PAH bioavailability. Arenicola marina digestive flui ds solubilize 4.6 mu g mL-' phenanthrene and 2.0 mu g mL(-1) benzo[a]pyrene -concentrations greater than the PAH's seawater solubilities-when incubated with pure PAH solids. This enhanced solubilization is largely due to surfa ctant micelles in the digestive fluid. In experiments with contaminated sed iments that repeat the incubation or vary the solid-fluid ratio, these and other PAHs saturate at much lower concentrations (often between 0.01 and 0. 1 mu g mL(-1)). Less solubilization is likely due to sorption of digestive surfactants by sedimentary organic matter and competition from other sedime ntary hydrophobic solutes, such as aliphatic hydrocarbons, for remaining mi cellar space. Nevertheless, gut fluid concentrations of high molecular weig ht PAHs are greater than those predicted from equilibrium partitioning theo ry, indicating the importance of the digestive pathway for hydrophobic orga nic contaminant exposure and bioaccumulation.