Abstract
Abstract. 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 analyzer. Snow emission fluxes were estimated from vertical gradients of mixing ratios observed at 1 cm and 1 m above the snow surface as well as in interstitial air a few centimeters below the surface and in air just above the snowpack. Typical flux values range between 1 and 2 × 1012 molecules m−2 s−1 at night and 3 and 5 × 1012 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 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. Simulations indicate that the gas-phase production from CH4 oxidation largely contributes (66%) to the observed HCHO mixing ratios. In addition, HCHO snow emissions account for ~ 30% at night and ~ 10% at noon to the observed HCHO levels.
Highlights
Over continents, formaldehyde is produced within the atmosphere during the oxidation of numerous hydrocarbons emitted by anthropogenic and natural sources and directly emitted by combustion
The aims of the present study are (1) to document the boundary layer HCHO mixing ratio at Concordia during the OPALE (Oxidant Production over Antarctic Land and its Export) project (Preunkert et al, 2012), (2) to quantify the summer HCHO snow emissions under conditions encountered at day and night at Concordia, and (3) to compare the role of snow emissions with that of the gas-phase production of HCHO in central Antarctica
HCHO measurements conducted in the three environmental compartments confirm that the snow at Concordia is a net source of HCHO in summer throughout day and night
Summary
Formaldehyde is produced within the atmosphere during the oxidation of numerous hydrocarbons emitted by anthropogenic and natural sources and directly emitted by combustion. The understanding of the budget of HCHO in polar regions is of importance since HCHO represents an important source of RO2 radicals in the remote polar atmosphere, and is intimately linked to the oxidative capacity of the atmosphere in these regions This is true in margin regions of Antarctica as concluded on the basis of examinations of the observed HOx budgets at Halley (Bloss et al, 2007) and Dumont d’Urville (DDU; Kukui et al, 2012).
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