Recipient Organization
STATE UNIV OF NEW YORK
(N/A)
SYRACUSE,NY 13210
Performing Department
Chemistry
Non Technical Summary
The redox chemistry of atmospheric mercury largely controls where and when this neurotoxin enters ecosystems. Most models of mercury chemistry assume OH or O3initiates oxidation of Hg(0), undeterred by contrary arguments based on physical chemistry. We propose using the power of advanced methods of computational chemistry to investigate mercury redox chemistry to improve atmospheric models. We have evidence that a two-step process involving both OH and O3 could efficiently oxidize Hg(0): OH initiates the process to make HOHg•, and in the second step HOHg• reacts with O3 to make HOHgO• + O2. This suggests Hypothesis 1: The reaction HOHg• + O3possesses a high rate constant, enabling OH to efficiently oxidize Hg(0) to Hg(II) throughout most of the atmosphere.Atmospheric models include the gas-phase reaction Hg + O3despite our ignorance of any thermodynamically feasible products of this reaction. The observation of solid and aerosol products in chamber studies suggests the reaction is surface-catalyzed at the high surface/volume ratios of laboratory experiments. This leads to Hypothesis 2: Hg + O3does NOT initiate Hg(0) oxidation in the gaseous atmosphere.A 2018 paper suggested that light absorption leads to extremely rapid photo-reduction of most Hg(II) compounds, including BrHgONO. By contrast, we published a paper in 2019 giving evidence that that photolysis of BrHgONO, while rapid, did not lead to photo-reduction. This leads to Hypothesis 3: Photo-reduction occurs only for some Hg(II) compounds.Intellectual Merit There is no experimental data of any kind on most of the compounds or reactions we plan to study. We will use cutting-edge methods of relativistic quantum chemistry and computational kinetics to determine the thermodynamics and rate constants for key reactions of Hg-containing radicals. We will also compute absorption cross-sections and photolysis pathways for stable Hg(II) compounds. When our calculations predict extensive production of a previously unsuspected Hg(II) species (e.g., HOHgO•), we will investigate its atmospheric fate. These results will provide insight into the patterns of reactivity and photo-reactivity of important mercury compounds. We will incorporate results of these fundamental studies into two models of atmospheric mercury.Broader Impacts Mercury is a neurotoxin that severely affects human and environmental health. Mercury is emitted to the atmosphere primarily as atomic mercury (Hg(0)), which largely stays in the atmosphere until it is oxidized. Despite the critical role of the redox chemistry of gaseous mercury to its global biogeochemical cycling, our understanding of this chemistry is still in its infancy: we have yet to investigate important reactions, and experimental data is largely missing or contradictory. We will incorporate research results into regional and global atmospheric models. The resulting model simulations will transform our understanding of the global processes controlling where and when mercury enters ecosystems. This, in turn, will advance studies of the health effects of mercury on humans and ecosystems.This project will provide advanced interdisciplinary technical and professional training to a postdoctoral research associate (PRA), a Ph.D. student, and several undergraduate students. The PRA and Ph.D. student will benefit from exposure to diverse aspects of computational science by interacting with two atmospheric modelers and two theoretical chemists (one international). The PI, PRA, and students will conduct outreach with hundreds of K-12 students each year through local science fairs and classroom visits.Awarded Start Date: 9/1/2020Sponsor: National Science Foundation
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
Please contact PI for details.
Project Methods
Please contact PI for details.