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Direct Kinetic Studies of the Gas Phase Transformation of Elemental Mercury by Hydroxyl and Halogen Radicals

EPA Grant Number: F6B10067
Title: Direct Kinetic Studies of the Gas Phase Transformation of Elemental Mercury by Hydroxyl and Halogen Radicals
Investigators: Donohoue, Deanna
Institution: University of Miami
EPA Project Officer: Just, Theodore J.
Project Period: August 1, 2006 through July 31, 2008
Project Amount: $74,172
RFA: STAR Graduate Fellowships (2006)
Research Category: Academic Fellowships , Mercury , Fellowship - Atmospheric Sciences , Air Quality and Air Toxics

Description:

Objective:

Over the last decade our understanding of mercury cycling has dramatically changed. The observation of high mercury concentrations in regions with no known sources, such as the Arctic, and the rapid loss of mercury from atmosphere in these regions at polar sunrise (AMDE) have lead to the recognition that elemental mercury, Hg0, can undergo rapid gas phase oxidation under standard atmospheric conditions. However, the mechanism and importance of this transformation is still unclear. The goal of this study is to determine reaction rate coefficients for the reactions of elemental mercury with hydroxyl and halogen radicals. These rate coefficients will provide insight into the mechanism of atmospheric mercury oxidation, and aid in the development of effective pollution controls for mercury emissions in the United States and worldwide.

Approach:

This project will use a Laser Induced Fluorescence (LIF) technique already employed at the University of Miami. The LIF technique will monitor the concentration of the mercury or the radical as they react, generating a concentration verses time profile. From this profile, a rate coefficient for the reaction can be obtained.

Expected Results:

This work will enhance our current knowledge concerning the biogeochemical cycling of mercury. The hydroxyl radical is often called the atmospheric vacuum cleaner, thus the determination of the rate coefficient for the reaction of mercury and the hydroxyl radical is essential in understanding mercury chemistry. Even a slow rate coefficient can have broad implications for the lifetime, concentration and distribution of mercury in the atmosphere. The determination of the rate coefficients associated with halogen radical reactions is necessary to clarify the unique mercury chemistry observed in Polar Regions, broaden our understanding of the mercury chemistry over the oceans, and provide insight into the chemistry of regions which have elevated levels of halogen radicals. All of these results will be essential to the modeling community as vital data which can be incorporated into global and regional mercury models and then used to evaluate the impacts of mercury emissions in order to develop effective mercury pollution control policies.

Supplemental Keywords:

mercury, atmosphere, gas phase, mercury oxidation, Laser Induced Fluorescence (LIF), kinetics, rate coefficients, hydroxyl radical, halogen radicals, polar sunrise, Atmospheric Mercury Depletion Episodes (AMDE), , Air, Scientific Discipline, air toxics, Environmental Chemistry, fate and transport, mercury emissions, emission control strategies, atmospheric mercury cycling, air pollutants, oxidation reactions, gas phase

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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