P B Shepson

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Bromine atoms are believed to play a central role in the depletion of surface-level ozone in the Arctic at polar sunrise. Br2, BrCl, and HOBr have been hypothesized as bromine atom precursors, and there is evidence for chlorine atom precursors as well, but these species have not been measured directly. We report here measurements of Br2, BrCl, and Cl2 made(More)
We performed an atmospheric inversion of the CO 2 fluxes over Iowa and the surrounding states, from June to December 2007, at 20 km resolution and weekly timescale. Eight concentration towers were used to constrain the carbon balance in a 1000×1000 km 2 domain in this agricultural region of the US upper midwest. The CO 2 concentrations of the boundaries(More)
It has been shown that sunlit snow and ice plays an important role in processing atmospheric species. Photochemical production of a variety of chemicals has recently been reported to occur in snow/ice and the release of these photochemically generated species may significantly impact the chemistry of the overlying atmosphere. Nitrogen 5 oxide and oxidant(More)
Isoprene hydroxynitrates (IN) are tracers of the photochemical oxidation of isoprene in high NO x environments. Production and loss of IN have a significant influence on the NO x cycle and tropospheric O 3 chemistry. To better understand IN chemistry, a series of photochemical reaction chamber experiments was conducted to determine the IN yield from(More)
This discussion paper is/has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP if available. Abstract The springtime depletion of tropospheric ozone in the Arctic is known to be caused by active halogen photochemistry resulting from halogen atom precursors emitted from snow, ice,(More)
Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to(More)
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