Mobilization of PAH from polluted seabed and uptake in the blue mussel (Mytilus edulis L.)

Abstract

In several Norwegian fjords that have received effluents from smelters, there are significant accumulations of polycyclic aromatic hydrocarbons (PAH) in the sediments; near the outfalls, concentrations may reach several hundred μg total PAH g^-1. As the smelters are now implementing measures to clean up and reduce discharges, the accumulations from previous discharges could assume greater relative importance as a potential source. In order to give an assessment of the significance of sedimentary PAH 'hot spots' in Norwegian smelter-affected fjords, an experiment was performed in which seabed sediment sections (0.5 × 0.5 m, 1.3 to 543 μg total PAH g^-1) were collected from the Oslo-, Sauda- and Sunndalsfjords and placed in an experimental set-up in which Oslofjord water taken from a depth of 40 m was passed over the sediment surfaces. The mobilization experiments indicated that a natural seabed containing 100 μg PAH g^-1, and with a resuspension (due to bioturbation) within an expected natural range, might give an annual contribution to the overlying water of the order of 20 kg PAH km^-2. Mussels continuously exposed to the water from the test sediments accumulated PAH in a clear response to concentrations in sediments and water and to the degree of resuspension. PAH from the Saudalsfjord were apparently more bioavailable than those from the Sunndalsfjord, and it is argued that a more rapid accumulation in the former case was stimulated by an elevated organic carbon content in the sediment.