Dissertation/Thesis Abstract

Microbial colonization and dissolution of mercury sulfide minerals
by Vazquez Rodriguez, Adiari Iraida, Ph.D., Harvard University, 2014, 149; 3645085
Abstract (Summary)

Mercury (Hg) is a toxic heavy metal that poses significant human and environmental health risks. Mineral-associated Hg is the largest reservoir of Hg in the environment where it can account for nearly 60% of the global Hg mass inventory. A large fraction of this pool is comprised of mercury sulfide (HgS) minerals, including metacinnabar (beta-HgS). HgS minerals have long been considered insignificant sources of Hg to aqueous or atmospheric pools in all but severely acidic environments due to their low solubility and slow abiotic dissolution kinetics. Little previous work has been conducted investigating the bacterial colonization of HgS minerals and the potential role of these mineral-associated communities in impacting the mobility of mineral-hosted Hg. To address this gap in knowledge, the studies within this dissertation employed a combination of field- and laboratory-based methods. Using culture-independent techniques, this work revealed that sulfur-oxidizing bacteria can extensively colonize metacinnabar within aerobic, near neutral pH, creek sediments, suggesting a potential role for chemolithotrophic bacteria in metacinnabar weathering. Within laboratory incubations, the dominant bacterial colonizer ( Thiobacillus thioparus), induced extensive release and volatilization of metacinnabar-hosted Hg. These findings expose a new pathway for metacinnabar dissolution and point to mineral-hosted Hg as an underappreciated source of elemental Hg that may contribute to global atmospheric Hg budgets. In addition, this work elucidates the importance of thiosulfate, a major intermediate sulfur species in the environment, in stimulating metacinnabar dissolution. Therefore, the work within this dissertation shows that authigenic HgS minerals are not merely a sink for Hg within non-acidic natural environments and instead are a source of dissolved and gaseous Hg. This work provides critical information for predicting the transport of Hg in the environment and for developing appropriate management and remediation strategies for Hg-contaminated systems.

Indexing (document details)
Advisor: Hansel, Colleen M.
Commitee: Johnston, David T., Lamborg, Carl H., Wofsy, Steven C.
School: Harvard University
Department: Engineering and Applied Sciences
School Location: United States -- Massachusetts
Source: DAI-B 76/03(E), Dissertation Abstracts International
Subjects: Biogeochemistry, Geobiology, Environmental science
Keywords: Geomicrobiology, Mercury cycle, Mercury sulfide, Metacinnabar dissolution, Microbial ecology, Sulfur oxidizing bacteria
Publication Number: 3645085
ISBN: 9781321335613
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