Formaldehyde (HCHO) in air, snow and interstitial air at Concordia (East Antarctic plateau) in summer
Résumé
During the 2011/12 and 2012/13 austral summers HCHO was investigated for the first time in ambient air, snow, and interstitial air at the Concordia site located near Dome C on the East Antarctic plateau by deploying an Aerolaser AL-4021 analyser. Snow emission fluxes were estimated from vertical gradients of mixing ratios observed between 5 1 cm and 1 m above the snow surface as well as between interstitial air a few cm below the surface and in air just above the snow-pack. Typical flux values range between 1 to 2 × 10 12 molecules m −2 s −1 at night and 3 to 5 × 10 12 molecules m −2 s −1 at noon. Shading experiments suggest that the photochemical HCHO production in the snowpack at Concordia remains negligible compared to temperature-driven air–snow exchanges. At 10 1 m above the snow surface, the observed mean mixing ratio of 130 pptv and its diurnal cycle characterized by a slight decrease around noon are quite well reproduced by 1-D simulations that include snow emissions and gas phase methane oxidation chemistry.
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