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Berkeley Atmospheric Sciences Center
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Geography @ University of California at Berkeley
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WELCOME... |
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Our research involves atmospheric chemistry and composition, terrestrial-atmosphere exchange of trace gases, halogen biogeochemistry, and stratospheric ozone depletion issues. Three current projects focus on the terrestrial biogeochemistry of methyl bromide (MeBr, CH3Br), methyl chloride (MeCl, CH3Cl), and methyl iodide (MeI, CH3I), collectively known as methyl halides. We have conducted field based flux measurements in Arctic tundra, temperate grasslands, coastal salt marshes, coast sagebrush, chaparral, creosote bush scrub, and boreal and temperate forests. This research has shown that numerous species of plants emit methyl halides at significant rates.
Field measurements will continue to constrain the natural terrestrial fluxes of methyl halides along with other compounds, and fluxes will be correlated with relevant biogeochemical parameters.
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I) Halomethane and methane fluxes in the northern Alaskan coastal tundra
A) Halomethanes: This research project will a) determine whether arctic coastal terrestrial ecosystems are significant sources or sinks of atmospheric methyl halides and chloroform; b) examine the environmental and biological controls on their fluxes; and c) predict the potential effect that arctic climate warming will have on the overall fluxes of these compounds, based on the biogeochemical controls.
B) Methane: Biogeochemical controls on methane fluxes in the tundra and tundra lakes.
Thanks to: National Science Foundation, Office of Polar Programs, Arctic System Science Program, NSF Grant #0435870.
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II) Temperate grassland fluxes of methyl halides using stable isotope tracers
We have developed a technique to simultaneously measure production and consumption fluxes of methyl halides using a stable isotope tracer technique. This method entails the addition of a small amount of 13C labeled methyl halides to an enclosure to track uptake rates, while measurement of 12C methyl halides yields the net flux. Temperate grasslands are believed to be globally significant sinks of methyl halides, but they might also simultaneously be sources as well. Through field work in California, Colorado and Kansas, we will deconvolute the natural source and sink strength in temperate grasslands. Funding from the National Science Foundation Division of Atmospheric Sciences, Atmospheric Chemistry Program, NSF Grant # 0526750.
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 Example of the stable isotope tracer method separating production and consumption of methyl bromide in boreal forest soils.
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III) Genetics of methyl halide production: Publications
We demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides, and that the enzyme primarily responsible for production is encoded by the HOL (HARMLESS TO OZONE LAYER) gene, found on chromosome 2. In mutant plants with a disruption of the HOL gene, methyl halide production is largely eliminated. A phylogenetic analysis suggests that the ability to produce methyl halides is widespread among vascular plants. Collaborators: Dr. Lars Ostergaard and Martin Yanofsky, UCSD. Thanks to the University Corporation for Atmospheric Research, NOAA Postdoctoral Fellowship program, for allowing the opportunity for this interdisciplinary research.
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