Detection of localized methylmercury contamination by use of the mussel adductor muscle in Minamata Bay and Kagoshima Bay, Japan

Based on our previous finding that the concentrations of total mercury in m ussel adductor muscle approximated those of methylmercury, we compared conc entrations of total mercury in the adductor muscle of the mussel Mytilus ga lloprovincialis, collected from four sites around Minamata City from 1993 t o 1995 and four sites in Kagoshima Bay from 1997 to 1998, to assess the lev el of localized methylmercury contamination. Though the input of mercury fr om the chemical plant had stopped by around 1970, concentrations of total m ercury in the mussel adductor muscle were higher at two sites (26-121 ng/g, n = 135) near the main fallout of wastewater from the chemical plant in Mi namata Bay than at the other sites, i.e. two sites 1-5 km from the former s ites in Minamata City (6-28 ng/g, n = 52), and all sites in Kagoshima Bay ( 2-30 ng/g, n = 287). The localized methylmercury contamination around the c hemical plant in Minamata Bay was documented also by our sensitive analysis of mercury concentrations in seawater and sediment samples. The survey of concentrations of total mercury in the mussel adductor muscle seems to be u seful for monitoring the methylmercury contamination in coastal areas. (C) 2000 Elsevier Science B.V. All rights reserved.