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 1330 pptv over the 13-day period with a mean of
183±233 pptv (± one standard deviation). Methyl hydroperoxide
(CH3OOH) reached up to 379 pptv with a mean of 51±55 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.
There was some evidence that elevated concentrations of H2O2 existed
in air-masses originating from the south-west, suggesting higher concentrations
of HOx due to more active photochemistry. Air which had been recently
polluted exhibited low H2O2 concentration due to a combination of
suppression of HO2 by NOx and deposition. The concentrations of
H2O2 sampled here are consistent with previous box modelling studies
of hydroperoxides, except in periods influenced by the boundary layer, where
agreement required 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., 6, 5525-5536, doi:10.5194/acp-6-5525-2006, 2006.