Scottish Marine and Freshwater Science Vol 01 No 17

Concentrations of hazardous substances, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated dipheyl ethers (PBDEs) and the metals cadmium (Cd), mercury (Hg) and lead (Pb), were determined in sediment and biota from around Scotland. The concentrations were investigated using assessment criteria developed by OSPAR and ICES.

PAH and PCB concentrations in sediment and biota in all Scottish regions, except the Clyde, are unlikely to give rise to pollution effects.

Lead concentrations in the Clyde and Moray Firth sediment are of concern and may give rise to pollution effects. Concentrations of Cd in deep water fish liver from Rockall were above the EC maximum level and, therefore, may be of concern from the perspective of human health.

Concentrations of PBDEs observed in Scottish sediments were low with all congeners below the limit of detection (LoD; 0.03 µg kg-1 dry weight) in 140 out of a total of 307 samples analysed. Higher concentrations were found in fish liver, although concentrations were low in all regions except the Clyde. The environmental significance of these concentrations could not be assessed due to the lack of suitable assessment criteria.

Organic contaminant concentrations (PAHs, PCBs and PBDEs) in sediment, and also fish liver for PCBs and PBDEs, were significantly higher in the Clyde compared to all other regions. Within the Clyde highest PCB and PAH concentrations were associated with known point sources such as the former sewage sludge dump site at Garroch Head, the dredge spoil dump site at Cloch Point and the former naval base at Holy Loch.

Modelled Toxic Equivalent (TEQ) concentrations indicated that in all Scottish regions, including the Clyde, PCB concentrations in fish liver are unlikely to result in any risk to human health.

Few trends were detected in contaminant concentrations in biota or sediment at any Scottish site with more than five years data, but where a trend was detected, this was downwards. Most downward trends were for PAHs in Clyde sediment.

Concentrations of contaminants in the Clyde were generally at levels such that there is an unacceptable risk of chronic effects occurring in marine species. This is mainly due to historic industrial inputs. However, downward trends were detected for Pb and PAHs in Clyde sediment indicating that the implementation of relevant regulations is beginning to have a positive environmental impact.

For all other regions the status of contaminants is generally acceptable in that concentrations are at levels where it can be assumed that little or no risks are posed to the environment and its living resources at the population or community level. There were some exceptions. These were Pb in Moray Firth sediments, PCBs in East Scotland sediments and Cd in fish from Hebrides, Rockall and Bailey. However, the overall status of the various regions, with respect to the assessed hazardous substances, can be considered to be acceptable (at least green). Thus Scotland has made substantial progress towards delivering a vision that includes clean seas