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Research Topics: |
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ATMOSPHERIC MERCURY POLLUTION The element mercury, best known as the shiny liquid used in old thermometers, is a toxic substance. Within humans, mercury impairs childhood development, causes neurological disorders, and may contribute to cardiac problems. My work aims to better understand the chemical processes that control the deposition of mercury from the atmosphere to ecosystems. The key reactions are the redox reactions which determine the ratio of oxidized to elemental mercury. While many redox reactions have been measured in the laboratory, it is still not clear which reactions dominate in the natural environment, since laboratory conditions may not be representative of atmospheric conditions. I'm currently examining whether atomic bromine, released from sea salt and biogenic bromocarbons, could be an important oxidant of Hg(0) on a global scale.
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The figure at right shows the geochemical mercury cycle among the soil, air and water reservoirs. Although emissions to the atmosphere from the ocean and soil exceed direct anthropogenic emissions, much of the mercury that evades from soil and water was originally released to the earth's surface through mining and industry.
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Posters and Publications
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TRANS-BORDER AIR POLLUTION Air pollution flows freely across political and geographic boundaries. This poses a problem for regulatory agencies, like the EPA, that may not have jurisdiction over the emissions sources that foul their air. Using a DC-8 research airplane, the NASA INTEX-B mission (March-May 2006) sampled air pollution generated in Asia as it flowed across the Pacific Ocean towards North America. While en route, exposure to sunlight and the reactive chemicals of the atmosphere change the chemical composition of the pollution. For example, unburned hydrocarbons (e.g. methane or CH4) released from fossil fuels react with atmospheric oxidants, such as the hydroxyl radical (OH), to generate carbon dioxide (CO2) and ozone (O3). While at high altitudes ozone in the "ozone layer" blocks harmful ultraviolet radiation, at the surface ozone irritates the lungs, causes respiratory diseases, and damages crops.
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My job in INTEX is to forecast where the pollution will be,
in order to direct the NASA DC-8 research airplane into it. We use
the consensus of several forecast models to plan the locations and
heights of our flights.
Click on the image for our forecast of CO for April 22-27, 2006. |
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The image above shows ribbons of concentrated carbon monoxide (CO)
stretching across the Pacific Ocean, as predicted by our computer model (GEOS-Chem).
We use CO as an indicator for the presence of many air pollutants that are produced through
combustion. Cold fronts loft CO from the surface, where it is
produced, to high altitudes where strong winds rapidly transport the
pollution across the Pacific in less than a week. Fronts appear in
the image and animation as long ribbons of CO extending over 30
degrees or more. In March-May, when weather patterns are most
favorable for trans-Pacific transport, Asian sources can increase the
concentration of some harmful pollutants, such as ozone and CO, by
10-20% in Western US States.
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Posters and Publications
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SCIENTIFIC FIGURES In addition to creating scientific content, I am very interested in the design of scientific figures. I've contributed flexible color utilities to the GAMAP software package, which is widely used by the Atmospheric Chemistry Modeling Group. The software improvements include color schemes optimized for readability in geospatial applications. I have also written documents and given informal seminars on designing better scientific figures for graduate students in Earth and Planetary Science at Harvard University |
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Seminars and Documents
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As a graduate student and member of the