Recent trends in organochlorine residue's in mussels (Mytilus edulis) from the Mersey Estuary

Blue mussels (Mytilus edulis) taken from several sites in the Mersey Estuary, an urban-industrial water body in NW England, have been analyzed for residues of the persistent organochlorines, DDT, PCB congeners nos. 28, 52, 101, 118, 138, 153 and 180 (ICES7), and alpha -MHCH (alpha -methyl hexachlorocyclohexane). The concentration range for Sigma PCB (ICES7) was 13.9-34.9 mug kg(-1) in 1994 compared with 9.6-31.9 mug kg(-1) in 1998, whilst the equivalent concentrations of Sigma DDT were 8.9-32.4 mug kg(-1) and 4.5-16.8 mug kg(-1), respectively. The concentration of alpha -MHCH, an organochlorine largely restricted to the Mersey Estuary, was 1.2-11 mug kg(-1) in 1994 and 0.3-1.3 mug kg(-1) in 1998. At both sampling dates the inner estuary sites of Rock Ferry and Egremont were more contaminated than the outer estuary sites of New Brighton, Dove Point and Caldy Blacks. The lower concentrations of organochlorines in mussels in 1998 compared with 1994 are thought to be early evidence of significant improvements in water quality derived from major capital investment in the treatment of industrial effluents and sewage wastewater, linked to a combination of stricter legislative controls and the environmental benefits from the adoption of new, clean technologies in manufacturing. (C) 2001 Elsevier Science Ltd. All rights reserved.