Methylation of mercury

Thus, both elemental mercury and the mineral form cinnabar (HgS) can release Hg++, the mercuric ion. Bacteria can then methylate it to form sequentially CH3 Hg+, the methyl mercuric cation, and dimethyl mercury. The latter, like elemental mercury, is volatile and tends to pass into the atmosphere when formed. The methylation of mercury can be accomplished in the environment by bacteria, notably in sediments. 

Landner L (1971) Biochemical model for biological methylation of mercury suggested from methylation studies in-vivo with Neurospora crassa. Nature 230 452-454. 

Methylation of mercury in natural waters. Pages 201-210 in J. O. Nriagu (ed.). The Biogeochemistry of Mercury in the Environment. Elsevier/North-Holland Biomedical Press, NY). 

Berman, M. and R. Bartha. 1986. Levels of chemical versus biological methylation of mercury in sediments. Bull. Environ. Contam. Toxicol. 36 401-404. 

Callister, S.M. and H.R. Winfrey. 1986. Microbial methylation of mercury in upper Wisconsin River sediments. Water Air Soil Pollut. 29 453-465. 

Mercon is a patented liquid mercury vapor suppressant designed to stop and absorb mercury vapors. The chemical process used creates a mercuric salt or sulfide. The reagents react with the metal and absorb any ambient vapor. Mercon products have the ability to stop and absorb any methylation of mercury in water. 

Compeau, G. C. Bartha, R. (1985). Sulfate-reducing bacteria principal methylators of mercury in anoxic estuarine sediment. Applied and Environmental Microbiology, 50, 498-502. 

The rate of methylation of mercury in anaerobically incubated estuarine sediments proved to be inversely related to salinity (267) this is consistent with results reported in Section II,A. Methylmercuric ion forms in sediments upon addition of HgCl2, with a lag phase of 1 month (268). Biomethylation by lake water columns and by sediments coincided, apparently being related to overall microbial activity, and showed periodic fluctuations (269). Topping and Davies have demonstrated that mercury can be methylated in the water column of a sea loch (270). As has previously been noted, tin compounds can be methylated by sediments (121-124), and this is also true for lead (134-136, 271). The relative proportions of biotic and abiotic methylation processes for such systems still remain to be determined. 

Figure 8 Sulfate/Sulfide controls on mercury methylation in aquatic environments —the Gilmour curve. At relatively low sulfate concentrations (most freshwaters), methylation of mercury is limited hy the rate of sulfate reduction. At higher sulfate concentrations (saltwaters), sulfide buildup from relatively high rates of sulfate reduction results in decreased bioavailahility of mercury (figure from Danger et al. (2001) after Gilmour and Henry (1991).

Jensen, S. and Jernelov, A., 1969. Biological methylation of mercury in aquatic organisms. Nature, 223 753—754. 

The biological methylation of mercury (e.g., from weathering, volcanism, fossil fuels, chloralkali electrolysis) is effected by microorganisms that utilize methylco-balamin (2c) see Section 5.1.2. 

Landner (1971), in his investigations on Neurospora crassa, connects the methylation of mercury with the biosynthesis of methyl ions. 

Watras JC and Hugkabff JW, eds. (1994) Mercury pollution — Integration and Synthesis. Lewis Publishers, Boca Raton-Ann Arbor-London-Tokyo. Wfbfr J (1993) Review of possible paths for abiotic methylation of mercury(II) in the aquatic environment. Chemosphere 26 2063 — 2077. 

Mercury Deposition of sulfate enhances methylation of mercury. Surface water acidification increases mercury accumulation in fish Branfireun et al. 1999, Driscoll et al. 1994... 

High sulfate levels also limit high methylation of mercury in wetland environments. Energy flow involving reduced sulfur species formed through sulfate reduction also occurs in salt marshes. 

Wetlands provide a unique interface between soil substrate, water, and biota, which supports various mercury transformations. Methylation of mercury occurs through chemical (abiotic) and biochemical (biotic) processes. Abiotic reactions involve transmethylation and photochemical processes (Ullirich et al., 2001). Biotic processes involve enzymatic and nonenzymatic metabolic meth-ylations by microorganisms (Choi and Bartha, 1993). The relative importance of abiotic versus... 

MD Baker, WE Inniss, Cl Mayfield, PTS Wong, YK Chau. Effect of pH on the methylation of mercury and arsenic by sediment microorganisms. Environ Technol Lett 4 89-100, 1983. 

Sulfate-reducing bacteria are the most important mercury-methylating agents in aquatic environments, with the most important site of methylation at the oxic-anoxic interface in sediments a similar pattern is documented for wetlands. In sediments, miao-bial methylation of mercury is fastest in the upper profiles where rate of sulfate reduction... 

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