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Mercury, biotic methylation

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... [Pg.483]

HgCl2 in the presence of estuarine sediments showed distinct seasonal variation, whose rhythm apparently relates to the seasonal ability of the microorganisms to carry out biomethylation (755, 156). The ability of different river sediments to perform biomethylation depended markedly on the nature of the sediments (157, 158) thus, organic sediments reacted appreciably faster than coarse sand. Activated sludge will methylate inorganic mercury compounds under both sterile and nonsterile conditions, suggesting the presence of both biotic and abiotic pathways (159). [Pg.331]

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. [Pg.348]

This ionic mercury (Hgll) adheres to aerosols and thus has a short (days to weeks) residence time in the atmosphere rainfall delivers it to the local soils and rivers. Ionic mercury is readily methylated (eqn. 5.24) by both abiotic and biotic pathways. However, most scientists now agree that methylation by anaerobic sulphate reducing bacteria (SRB) is most important. [Pg.172]

In addition organo-mercuiy compounds are of environmental interest in aquatic systems not only since the Minamata disaster (Takizawa 2000). Especially methylated mercuiy species were detected and monitored in riverine systems as the result of biotic transformation of inorganic mercury... [Pg.17]

Solar radiation drives a number of chemical transformations of mercury. These include (i) atmospheric speciation and deposition, (ii) oxidation-reduction in both freshwater and seawater, and (iii) methyl mercury degradation. Both biotic and abiotic redox reactions are influenced. While microbes have been thought to dominate methyl mercury production, abiotic formation cannot be... [Pg.233]


See other pages where Mercury, biotic methylation is mentioned: [Pg.204]    [Pg.204]    [Pg.461]    [Pg.484]    [Pg.228]    [Pg.79]    [Pg.4649]    [Pg.4670]    [Pg.4922]    [Pg.443]    [Pg.632]    [Pg.13]    [Pg.953]    [Pg.1118]    [Pg.108]    [Pg.129]    [Pg.383]   
See also in sourсe #XX -- [ Pg.204 ]




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