title: Reevaluation of Minamata Bay, 25 years after the dredging of mercury-polluted sediments.
abstract: A detailed investigation of mercury concentrations in the bottom sediments of Minamata Bay was performed in May, 2012. A total of 691 sediment samples were obtained from 107 sampling points in the bay. The weighted average total mercury concentration and the total mass of mercury in the bottom sediments of Minamata Bay were estimated to be 2.3mg/kg dry weight basis and 3.4 tons, respectively. The average concentration of total mercury in the surface layer of the sediments was 3.0mg/kg dry weight basis, and the distribution pattern of total mercury concentrations in the surface layer was found to have changed little in comparison to results reported 25 years ago. In addition, based on the results of seawater monitoring in Minamata Bay from 2010 to 2012, the amounts of total mercury and methylmercury mobilized from sediments and dissolved in the water column were 0.7 and 0.1 kg/yr, respectively.
authors.affiliation: National Institute for Minamata Disease, Department of Environmental Science and Epidemiology, Environmental Chemistry Section, 4058-18 Hama, Minamata, Kumamoto 867-0008, Japan. Electronic address: Matsuyam@nimd.go.jp.
authors.forename: Matsuyama
authors.initials: M
authors.lastname: Akito
authors.affiliation: Kyushu University, Faculty of Engineering, Nishiku Motooka 744, Fukuoka 819-0395, Japan. Electronic address: yano@civil.kyushu-u.ac.jp.
authors.forename: Yano
authors.initials: Y
authors.lastname: Shinichiro
authors.affiliation: Kyushu University, Faculty of Engineering, Nishiku Motooka 744, Fukuoka 819-0395, Japan.
authors.forename: Hisano
authors.initials: H
authors.lastname: Akihiro
authors.affiliation: National Institute for Minamata Disease, Department of Environmental Science and Epidemiology, Environmental Chemistry Section, 4058-18 Hama, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Kindaichi
authors.initials: K
authors.lastname: Michiaki
authors.affiliation: National Institute for Minamata Disease, Department of Environmental Science and Epidemiology, Environmental Chemistry Section, 4058-18 Hama, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Sonoda
authors.initials: S
authors.lastname: Ikuko
authors.affiliation: Nagasaki University, Faculty of Engineering, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan.
authors.forename: Tada
authors.initials: T
authors.lastname: Akihide
authors.affiliation: International Mercury Laboratory Inc., Minamata, Kumamoto 867-0034, Japan.
authors.forename: Akagi
authors.initials: A
authors.lastname: Hirokatsu
mesh_terms: D061006:Bays / Q000737:chemistry*; D004784:Environmental Monitoring; D004787:Environmental Pollution / Q000032:analysis; D019015:Geologic Sediments / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Minamata Bay; Outflow; Sediment; Spatial distribution; Total-Hg