Polycyclic aromatic hydrocarbon (PAH) concentration and composition determined in farmed blue mussels (Mytilus edulis) in a sea loch pre- and post-closure of an aluminium smelter

Abstract

Concentrations of polycyclic aromatic hydrocarbons (2- to 6-ring parent and branched PAH) from an actively producing commercial shellfish farm in Loch Leven, Scotland, were found in excess of 4000 ng g⁻¹ wet weight tissue. These concentrations were considerably greater than had been recorded from mussels sampled elsewhere around the Scottish mainland. The PAH composition of the mussels from Loch Leven was dominated by the 5-ring, parent compounds; benzo[b]fluoranthene was the dominant compound. This data was consistent with the source being a discharge from an aluminium smelter. The individual compounds benz[a]anthracene, benzo[a]pyrene and dibenz[a,h]anthracene returned values of 304 ng g⁻¹, 446 ng g⁻¹ and 39 ng g⁻¹ respectively; these were well above the 15 ng g⁻¹ pragmatic guideline limit. Over the two year monitoring period, the concentrations of these compounds in mussels from Loch Etive, a reference location, ranged between ‘not detected’ and 4 ng g⁻¹ (for benz[a]anthracene). Mussels were transferred from a clean location to Loch Leven which demonstrated that the rate of uptake of PAH was rapid. Following closure of the aluminium smelter, the PAH concentrations in mussels decreased. Differences between the two sites within Loch Leven were noted with the longer-term impact remaining greater for the mussels closer to the original point discharge.