title: The influence of sample drying and storage conditions on methylmercury determination in soils and sediments.
abstract: The separate influences of drying and storage conditions on methylmercury (MeHg) concentrations in soil and sediment samples were investigated. Concentrations of MeHg and total Hg were determined in various soil and sediment samples that had been stored or dried under differing conditions. The influence of drying conditions (oven-drying (40 °C) versus freeze-drying) on MeHg concentrations in marine sediments, river sediments, soils, and paddy field soils was investigated (n = 43). The ratio of the MeHg concentration in oven-dried sub-samples divided by the concentration in freeze-dried sub-samples ranged from 0 to 336%. In order to confirm the production of MeHg during storage in some samples, Hg2+was added at 15 mg kg-1to a paddy soil, and the sample was then stored at 30 °C. The concentrations of MeHg at 1-h, 1-day, 4-days and 7-days after Hg2+spiking were 2.0 ± 0.1, 13.8 ± 1.0, 36.0 ± 5.0, and 24.9 ± 1.6 μg kg-1(n = 3), respectively. The concentration of MeHg at 4-days after Hg spiking and sterilizing (121 °C, 30 min) was 1.8 μg kg-1, similar to the original value. These results indicate that bacterial Hg methylation and MeHg demethylation occurred within days in the soil. In addition, tests of the stability of MeHg in wet and dry samples during storage were also performed. Overall, our results indicate that the best way to preserve MeHg in soil and sediment samples is to freeze the samples immediately after collection, followed subsequently by freeze-drying, grinding, homogenization, and storage of the dry material in cool, dark conditions until analysis.
authors.affiliation: Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan. Electronic address: kodama@sci.kagoshima-u.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kodamatani
authors.affiliation: Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Maeda
authors.affiliation: Metropolitan Council Environmental Services, 2400 Childs Road, St. Paul, MN 55106, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Balogh
authors.affiliation: Metropolitan Council Environmental Services, 2400 Childs Road, St. Paul, MN 55106, USA.
authors.forename: Yabing H
authors.initials: YH
authors.lastname: Nollet
authors.affiliation: Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kanzaki
authors.affiliation: Division of Earth and Environmental Science, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tomiyasu
mesh_terms: D003890:Desiccation; D004784:Environmental Monitoring / Q000379:methods*; D005612:Freeze Drying; D019015:Geologic Sediments / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D045483:Rivers; D012989:Soil Pollutants / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical
keywords: Freeze-drying; Methylmercury; Oven-drying; Sediment; Soil; Storage