Abstract

Sewage sludge dumping at Garroch Head in the Firth of Clyde ceased on 31 December 1998. Eighteen of the 209 chlorinated biphenyls (CBs) were measured in plaice livers, collected in 1999 and 2000, from the former Garroch Head dump site. Samples were also obtained from Pladda, a site reasonably remote from the former dump site but also in the Clyde, in 1999 only. These results were compared to the CB concentrations in plaice livers collected between 1992 and 1998 from Garroch Head and Pladda. Additional samples were also taken from a clean reference site, close to Colonsay. Concentrations of the congeners in the livers of fish caught at the former Garroch Head dump site in 1999 were marginally higher than those from Pladda, with a mean CB concentration of 1861 µg kg⁻¹ lipid in the Garroch Head plaice livers and 1725 µg kg⁻¹ lipid for the sample from Pladda. The mean CB concentration in the 2000 Garroch Head samples was 2253 µg kg⁻¹ lipid. CB concentration in plaice livers from Colonsay were lower than both the Pladda and Garroch Head fish, with plaice livers from Colonsay giving a mean CB concentration of 1076 µg kg⁻¹ lipid in 1999 and 345.1 µg kg⁻¹ lipid in 2000. The data was evaluated using principal component analysis (PCA). Pattern analysis was undertaken by normalising to the recalcitrant CB 153. There was an indication that the CB pattern has changed since the cessation of dumping with the proportion of tri- and tetra-chlorinated CBs being lower in plaice from Garroch Head than in previous years.