| Abstract
| - Although one potential drawback of wetland constructionand restoration is the formation of monomethylmercury,it may be possible to decrease net mercury methylation withthe use of an appropriate sediment amendment. Usingpure cultures of the sulfate-reducing bacterium Desulfobulbuspropionicus (1pr3), we tested the hypothesis that addingferrous iron to sulfidic wetland sediments decreases mercurysolubility and bioavailability and, therefore, net methylation.In sediment-free cultures, net mercury methylationdecreased with increasing [Fe(II)]. After 72 h of incubation,more than four times as much net methylmercury formedin the lowest ([Fe(II)] = 10-6 M) treatment (180 ± 33pM) as compared with the highest ([Fe(II)] = 10-2 M)treatment (42 ± 14 pM). In cultures containing a modelwetland sediment, more than three times as muchmethylmercury was observed in 10-6 M Fe(II) treatments(1,010 ± 95 pM) as compared with treatments amendedwith 10-2 M Fe(II) (300 ± 46 pM). Initial filterable mercurymeasurements and chemical equilibrium speciationpredictions suggest that the lower net methylmercuryproduction in the high-iron treatments was due to a decreasein sulfide activity and a concomitant decrease in theconcentration of dissolved mercury. Although ironamendments could potentially minimize net mercurymethylation in engineered wetland sediments, furtherresearch under field conditions is required to assess theefficacy of this approach.
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