Mercury Methylation in Macrophyte Roots of a Tropical Lake

Mercury (Hg) methylation was studied in water,sediment and Eichhornia crassipesroots of a freshwater lake, in Rio de Janeiro(Brazil). Samples were incubated with203HgCl2 and the Me203Hg producedwas measured by liquid scintillation.Methylmercury (MeHg) production was <10-3% in water, low in sediment (up to5.8%) and high in E. crassipesroots (21–27%). Higher MeHg formation wasfound in aerobic conditions for the roots and inanaerobic conditions for the sediment.Methylation increased with incubation time, upto 5 days. A 3-day incubation period was used inthe majority of the assays, to avoid large scalephysico-chemical changes inside the incubationflasks. Methylation was not detected inheat-sterilized root samples. Sodium sulphatestimulated Hg methylation while sodium molybdateinhibited the process in samples incubated for3, 6, 12, 24, 48 and 72 hr. This suggeststhat sulphidogenic bacteria are responsible forthe methylation process. Experiments with rootsstored at 5 and 25 °C fordifferent periods before incubation, indicatethat methylation is modified by storage time and temperature.

[1]  K. Finster,et al.  Sulphate reduction associated with roots and rhizomes of the marine macrophyte Zostera marina , 1998 .

[2]  R. Bartha,et al.  Methylation and demethylation of mercury under controlled redox, pH and salinity conditions , 1984, Applied and environmental microbiology.

[3]  S. Shrivastava,et al.  Observation on the Utility of Integrated Aquatic Macrophyte Base System for Mercury Toxicity Removal , 1997, Bulletin of environmental contamination and toxicology.

[4]  E. A. Henry,et al.  Mercury methylation in aquatic systems affected by acid deposition. , 1991, Environmental pollution.

[5]  C. Gilmour,et al.  Methylmercury production in the anoxic hypolimnion of a Dimictic Seepage Lake , 1995 .

[6]  R. Bartha,et al.  Sulfate-Reducing Bacteria: Principal Methylators of Mercury in Anoxic Estuarine Sediment , 1985, Applied and environmental microbiology.

[7]  P. Craig.  Organometallic Compounds in the Environment , 2002 .

[8]  B. Forsberg,et al.  Autotrophic Carbon Sources for Fish of the Central Amazon , 1993 .

[9]  J. D. Guimarães,et al.  Mercury methylation in a tropical macrophyte: influence of abiotic parameters , 1999 .

[10]  James H. Weber,et al.  Review of possible paths for abiotic methylation of mercury(II) in the aquatic environment , 1993 .

[11]  P. Garrison,et al.  Trophic transfer of methyl mercury in the northern Florida Everglades , 1998 .

[12]  Martin M. Shafer,et al.  Influences of watershed characteristics on mercury levels in wisconsin rivers. , 1995, Environmental science & technology.

[13]  H. Lewerenz,et al.  Methylmercury (Environmental Health Criteria No. 101). 144 Seiten, 5 Abb. 11 Tab. World Health Organization, Geneva 1990. Preis: 16, — Sw.fr.; 12,80 US $ , 1991 .

[14]  J. Rudd,et al.  Measurement of Mercury Methylation in Lake Water and Sediment Samples , 1980, Applied and environmental microbiology.

[15]  B. Jørgensen,et al.  Pathways and Microbiology of Thiosulfate Transformations and Sulfate Reduction in a Marine Sediment (Kattegat, Denmark) , 1991, Applied and environmental microbiology.

[16]  G. A. Gill,et al.  Methylmercury concentrations and production rates across a trophic gradient in the northern Everglades , 1998 .

[17]  M. Winfrey,et al.  Seasonal and Spatial Variations in Mercury Methylation and Demethylation in an Oligotrophic Lake , 1987, Applied and environmental microbiology.

[18]  O. Malm,et al.  Hg methylation in sediments and floating meadows of a tropical lake in the Pantanal floodplain, Brazil , 1998 .

[19]  A. Heyes,et al.  The hydrology and methylmercury dynamics of a Precambrian shield headwater peatland , 1996 .

[20]  G. Wagner,et al.  Heavy metal distribution in Bulgaria using Populus nigra ‘Italica’ as a biomonitor , 1995 .