Species-specific stable isotope fractionation of mercury during Hg(II) methylation by an anaerobic bacteria (Desulfobulbus propionicus) under dark conditions - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Environmental Science and Technology Année : 2009

Species-specific stable isotope fractionation of mercury during Hg(II) methylation by an anaerobic bacteria (Desulfobulbus propionicus) under dark conditions

Résumé

This work reports the first results on the stable isotope fractionation of Hg during methylation by anaerobic bacteria under dark conditions.TheGC-MC- ICPMSmethodologyemployed is capable of simultaneously measuring the species-specific isotopic composition of different Hg species within the same sample. We have studied Hg isotopic fractionation caused by methylation of Hg(II) standard reference material NIST-3133 in the presence of the pure bacterial strain Desulfobulbus propionicus MUD10 (DSM 6523) under fermentative conditions. We have measured the isotopic composition of Hg(II) and monomethyl mercury (MMHg) in these cultures as a function of time and calculated delta-values for both species versus the starting material (NIST-3133) as a delta-zero standard. Two differentstrategiesfortheincubationwereapplied: singlesampling cultures and a continuous sampling culture. The results obtained have shown that under the conditions employed in this work the methylation of Hg(II) causes mass-dependent fractionation of the Hg isotopes for both Hg(II) substrate and producedMMHg.Suchaprocess occurred under the exponential growth of the bacteria which preferentially methylate the lighter isotopes of Hg. After 96 h for the continuous culture and 140 h for the single sampling cultures,weobserved a change in the fractionation trend in the samples at a similar cell density value (ca. 6.0 × 107 cells mL -1) which suggests the increasing contribution of a simultaneous process balancing methylation extent such as demethylation.Assumingthat Rayleigh type fractionation conditions are met before such suppression, we have obtained a α202/198 fractionation factor of 1.0026 ± 0.0004 for the single sampling cultures.

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Chimie
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hal-01843572 , version 1 (18-07-2018)

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P. Rodŕiguez-Gonźalez, Vladimir Epov, Romain Bridou, Emmanuel Tessier, Remy Guyoneaud, et al.. Species-specific stable isotope fractionation of mercury during Hg(II) methylation by an anaerobic bacteria (Desulfobulbus propionicus) under dark conditions. Environmental Science and Technology, 2009, 43 (24), pp.9183-9188. ⟨10.1021/es902206j⟩. ⟨hal-01843572⟩
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