Atmos. Chem. Phys. Discuss., 6, 7177-7205, 2006
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Processes controlling the concentration of hydroperoxides at Jungfraujoch Observatory, Switzerland
S. J. Walker1, M. J. Evans1, A. V. Jackson1, M. Steinbacher2, C. Zellweger2, and J. B. McQuaid1
1Institute for Atmospheric Science, School of the Earth and Environment, University of Leeds, Leeds, UK
2Swiss Federal Institute for Materials Science and Technology (Empa), Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland

Abstract. An automated, ground-based instrument was used to measure gas-phase hydroperoxides at the Jungfraujoch High Altitude Research Station as part of the Free Tropospheric EXperiment (FREETEX) during February/March 2003. A nebulising reflux concentrator sampled ambient air twice hourly, prior to on-site analysis by HPLC speciation, coupled with post-column peroxidase derivatisation and fluorescence detection. Hydrogen peroxide (H2O2) concentrations reached up to 1420 pptv over the 13-day period with a mean of 206±261 pptv (± one standard deviation). Methyl hydroperoxide (CH3OOH) reached up to 921 pptv with a mean of 76±96 pptv. No other organic hydroperoxides were detected. The lack of an explicit diurnal cycle suggests that hydroperoxide concentrations are chiefly influenced by transport processes rather than local photochemistry at this mountainous site. We find elevated concentrations of H2O2 in air masses originating from the south-west indicative of higher concentrations of HOx due to more active photochemistry. Air which has been recently polluted exhibits low H2O2 concentration due to a combination of suppression of HO2 by NOx and deposition. We also conclude that despite being at a high alpine site, the vast majority of the air observed was extensively influence by the boundary layer during our campaign (diagnosed from high CO concentrations and the high NOx to NOy ratio) resulting in deposition of H2O2 to the surface and hence reduced H2O2 concentrations. The concentrations of H2O2 sampled here are consistent with previous box modelling studies of hydroperoxides which invoked a depositional sink.

Citation: Walker, S. J., Evans, M. J., Jackson, A. V., Steinbacher, M., Zellweger, C., and McQuaid, J. B.: Processes controlling the concentration of hydroperoxides at Jungfraujoch Observatory, Switzerland, Atmos. Chem. Phys. Discuss., 6, 7177-7205, doi:10.5194/acpd-6-7177-2006, 2006.
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