Formaldehyde (HCHO) in air, snow, and interstitial air at Concordia (East Antarctic Plateau) in summer

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 × 10 12 molecules m −2 s −1 at night and 3 and 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 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 CH 4 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.

Understanding mercury oxidation and air–snow exchange on the East Antarctic Plateau: a modeling study

“…3.4). The concentrations of Br are estimated assuming a photochemical steady state: (Holmes et al, 2010), where J BrO is the BrO photolysis frequency, and k BrO+NO and k Br+O 3 are rate constants for BrO+NO → Br+NO 2 and Br + O 3 → BrO + O 2 , respectively (Sander et al, 2011).…”

Impact of exhaust emissions on chemical snowpack composition at Concordia Station, Antarctica

“…Two identical multi-inlet snow sampling manifolds ("snow tower") for collection of interstitial and ambient air were constructed, with a design similar to that described by Seok et al (2009) (Fig. 2b).…”

Reviewer Comments on " Intrusion, retention, and snowpack chemical effects from exhaust emissions at Concordia Station, Antarctica" by Helmig et al.

“…Even though not as sensitive to pollution as NOx I urge the authors to present and discuss those data during pollution events to achieve a more general picture of pollution impacts near the station. For example formaldehyde has been discussed as a snowpack HOx radical precursor at Dome C (Preunkert et al, 2015), and it would be important to understand if and how station pollution changes also nearby CH2O profiles in snow.…”