摘要
Mercury-contaminated industrial effluent was discharged over a 30-year period into Princess Royal Harbour, a marine embayment on the south coast of Western Australia. The discharge of effluent was stopped in 1984 and most fish taken from the harbour at that time contained concentrations of Hg in their muscle tissue which exceeded the maximum permitted concentration (0.5 mg kg−1) set by Australian health authorities. To allay human health concerns, the contaminated portion of the harbour was closed to all forms of commercial and recreational fishing in 1984. The course of Hg contamination following cessation of the effluent discharge was monitored by determining Hg concentrations in the muscle tissue of eight teleost fish species, namely cobbler (Cnidoglanis macrocephalus), rock flathead (Platycephalus laevigatus), striped trumpeter (Pelates sexlineatus), King George whiting (Sillaginodes punctata), Australian herring (Arripis georgianus), brown-spotted wrasse (Pseudolabrus parilus), spiny-tailed leatherjacket (Bigener brownii) and six-spined leatherjacket (Meuschenia freycineti), sampled near the effluent outfall on 14 occasions from 1984 to 1993. Mercury concentration showed a significant positive relationship with length of fish for five of the species and a significant negative relationship with length for two species. Four species showed significant differences in Hg concentration depending on season (summer vs winter); summer concentrations were generally higher than those in winter. The Hg concentrations decreased with time and were about 50%of their initial values by 1993. In general, fish Hg levels had decreased to below the maximum permitted concentration by 1991 and the closed portion of the harbour was reopened in 1992. For most species, however, the rate of reduction in Hg concentration was less in the latter part of the study. The data suggest that future reductions in Hg concentrations in fish may be less than those achieved in the first 10 years, and that for some species Hg concentrations could remain elevated for many years.