Occurrence of PAH in marine organisms and sediments from smelter discharge in Norway

Norwegian aluminium works have each discharged 1–10 tons or more of PAH per annum directly into fjords, most of which originates from the scrubbing of hall gas in connection with Söderberg technology and from the production of anodes. In recent years, discharges have been considerably reduced, but still > 10 tons per year are discharged from the industry. Environmental assessment studies have systematically been performed from about 1980. Analyses of indicator organisms which accumulate PAH in high concentrations without apparent detrimental effects, have been used to assess the extent of contamination of water masses. The blue mussel (Mytilus edulis), and also its close relative the horse mussel (Modiolus modiolus), appear to be the most important indicators. The large amounts of waste have resulted in considerable contamination of fjord biota and sediments. PAH concentrations in indicator organisms of > 1000 times the background values have been recorded within 1–2 km of the outfalls. Elevated concentrations have been traced for more than 35–40 km. Surface sediment concentrations in the range of some hundred μg total PAH/g dry wt. have been observed. The concentration gradients vary but are generally steep. In several receiving waters, considerable improvements have been recorded shortly after a reduction in output load, and concentrations in mussels have fallen to 1100 of previous values in some cases. Remobilization experiments indicate that ‘hot spot’ accumulations might be of significance.