| Formation and dissolution of nanoscale mercuric sulfides: implications for microbial bioavailability and biotransformation | |
| Presenter | Anh Pham, Carleton University |
| Session Title | Coupled Cycling of Biogeochemical Critical Elements and Contaminants |
| Abstract | Mercury (Hg) has been recognized as a global contaminant. While all forms of Hg are toxic, it is monomethylmercury (MeHg), a neurotoxin produced by Hg-methylating microorganisms, which has raised the biggest concerns. As a result, much of the research to date has aimed at understanding the mechanism through which MeHg is formed, and identifying environmental factors that control this process. Researchers have learnt that MeHg is mostly produced in anoxic settings by several anaerobic bacteria, and that dissolved Hg are likely the species that get converted into MeHg. Additionally, our recent findings have indicated that in anoxic settings nanoparticulate HgS minerals (nano-HgS) are likely the predominant Hg species. Therefore, the concentration of dissolved Hg and Hg bioavailability in those settings are likely controlled by the precipitation and dissolution of nano-HgS. This seminar will discuss how the use of a series of synchrotron-based characterization techniques (e.g., Small Angle X-ray Scattering and X-ray Absorption Spectroscopy), coupled with various methods to quantify for dissolved Hg (e.g., filtration, ultracentrifugation, and DGT- diffusive gradient in thin films), has allowed us to gain new insights into the formation, structural and aggregation properties, and dissolution rates of nano-HgS. How this information can be used to better predict MeHg production will be discussed. |