| Abstrakt: |
Mercury (Hg) methylation was studied in water, sediment and Eichhornia crassipes roots of a freshwater lake, in Rio de Janeiro (Brazil). Samples were incubated with 203HgCl2 and the Me203Hg produced was measured by liquid scintillation. Methylmercury (MeHg) production was <10-3% in water, low in sediment (up to 5.8%) and high in E. crassipes roots (21–27%). Higher MeHg formation was found in aerobic conditions for the roots and in anaerobic conditions for the sediment. Methylation increased with incubation time, up to 5 days. A 3-day incubation period was used in the majority of the assays, to avoid large scale physico-chemical changes inside the incubation flasks. Methylation was not detected in heat-sterilized root samples. Sodium sulphate stimulated Hg methylation while sodium molybdate inhibited the process in samples incubated for 3, 6, 12, 24, 48 and 72 hr. This suggests that sulphidogenic bacteria are responsible for the methylation process. Experiments with roots stored at 5 and 25 °C for different periods before incubation, indicate that methylation is modified by storage time and temperature. [ABSTRACT FROM AUTHOR] |
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