ISSN:
0268-2605
Keywords:
manganese oxides
;
montmorillonite
;
kaolinite
;
mercury(II)
;
methylation
;
Chemistry
;
Industrial Chemistry and Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The effects of freshwater sediment components such as kaolinite, montmorillonite and birnessite (δ-MnO2) on the biomethylation of mercury(II) in a synthetic growth medium (M-IIY) were assessed. Additions of kaolinite or montmorillonite to media containing mercuriC nitrate [Hg(NO3)2; 12 μg Hg ml-1] had no significant effect on either bacterial growth or the production of methylmercury (CH3Hg+). However, whereas the addition of birnessite resulted in only a small (ca 4%) increase in bacterial growth, it also produced a significant decrease (ca 50%) in the production of CH3Hg+. Further, it was demonstrated that, with the exception of kaolinite, adsorption of mercury(II) onto the sediment components before they were added to the M-IIY medium decreased its bioavailability, i.e., the amounts of CH3Hg+ produced from the adsorbed mercury(II) were significantly lower than those produced from equivalent concentrations of Hg(NO3)2 in the absence of the mineral colloids. In the case of montmorillonite, CH3Hg+ production was decreased by 21% relative to the control system. Most striking was the case of birnessite, in which no CH3Hg+ was detected after a 25 h incubation period and only very small quantities of CH3Hg+ (3-7 ng l-1) were present in the medium after 336 h. These data demonstrate that mineral colloids common in freshwater sediments significantly influence the extent of biomethylation of mercury(II) adsorbed on their surfaces. Birnessite, in particular, is a very effective inhibitor of the biomethylation of surface-bound mercury(II). Therefore, it may be possible to reduce the severity of mercury pollution in some aquatic environments by adding a reactive manganese oxide, such as birnessite, to the system and thereby to inhibit the transformation (methylation) of inorganic mercury(II) into the much more toxic CH3Hg+ species. © 1998 John Wiley & Sons, Ltd.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
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