Sr and As mobilization during the microbial reduction of bacteriogenic iron oxide (BIOS)

Pour en savoir plus sur Danielle Fortin, cf. http://homepage.mac.com/drfab/media/danielle.html Resume: Bacteriogenic iron oxides (BIOS) naturally occur in a wide range of environments including wetlands, hydrothermal sea vents and hot springs. BIOS are essentially composed of neutrophilic iron-oxidizing bacteria and poorly ordered iron oxides, such as ferrihydrite. Given their high surface reactivity and surface area, they have been shown to be efficient sorbents of aqueous contaminants. The present study investigates the redox stability of naturally occurring BIOS and the fate of their sorb contaminants (As and Sr). Results indicate that BIOS samples (composed of ferrihydrite and smaller amouns of lepidocrocite and goethite) from a wetland area and gold mine tailing undergo rapide microbial reduction in the presence of a well known iron-reducing bacterium (i.e., Shewanella putrefaciens CN32). In fact, the reduction rates observed for the various BIOS samples far exceed those of synthetic iron oxides (ferrihydrite). The results also show that the presence of sorbed Sr and As (present as outer-sphere and inner-sphere complexes, respectively) stabilizes BIOS during microbial reduction by blocking reactive sites onto the iron oxides. Finally, the fate of Sr and As during reduction mirrors that of Fe(II), indicating that all sorbed contaminants are released back into solution