The concentrations of mercury in fish taken from Liverpool Bay and Morecambe Bay in 1998

摘要

Mercury levels in commercial fish species have been monitored by the Burnham Laboratory since the 1970s (e.g. Portmann, 1979). Early results indicated that the highest concentrations were found in four areas, Liverpool Bay, Morecambe Bay and Swansea Bay, all of which received discharges containing mercury from the chlor-alkali industry and in the outer Thames Estuary where a significant input was via sewage sludge disposal. Annual monitoring of these four areas commenced in the early 1980s, followingthe adoption in 1980 by the Paris Commission, of the mercury EQS. This required that in areas receiving significant mercury inputs, the concentration of mercury in a representative sample of fish flesh chosen as an indicator should not exceed 0.30 mg kg~(-1) on a wet weight basis. Monitoring soon indicated that the concentrations of mercury in Swansea Bay and the Thames Estuary were no longer elevated to a level potentially exceeding the EQS and in 1985 it was agreed that monitoring in these areas could cease. Mercury concentrations remained relatively high at this time in Liverpool and Morecambe Bays and results continued to be reported to OSPAR until 1994 (though at two yearly intervals from 1990), when it was agreed that the requirement for regularreporting could cease. Some re-assurance monitoring has been undertaken since that time and the results from the most recent survey, carried out in 1998, are summarised in Table 8. The concentration of mercury in individual fish species is now very muchless than the limit of 0.50 mg kg~(-1) set in European Community Decision 93/35 I/EEC on maximum limits for mercury in fishery products. The overall mean concentration in fish from both areas was 0,16 mg kg~(-1), so reassurance can continue to be giventhat the mercury EQS will not be breached.