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Guyancourt, France

Legrand M.,French National Center for Scientific Research | Legrand M.,University Grenoble alpes | Preunkert S.,French National Center for Scientific Research | Preunkert S.,University Grenoble alpes | And 11 more authors.
Atmospheric Chemistry and Physics | Year: 2014

During the austral summer 2011/2012 atmospheric nitrous acid (HONO) was investigated for the second time at the Concordia site (75°060 S, 123°330 E), located on the East Antarctic Plateau, by deploying a long-path absorption photometer (LOPAP). Hourly mixing ratios of HONO measured in December 2011/January 2012 (35±5.0 pptv) were similar to those measured in December 2010/January 2011 (30.4±3.5 pptv). The large value of the HONO mixing ratio at the remote Concordia site suggests a local source of HONO in addition to weak production from oxidation of NO by the OH radical. Laboratory experiments demonstrate that surface snow removed from Concordia can produce gasphase HONO at mixing ratios half that of the NOx mixing ratio produced in the same experiment at typical temperatures encountered at Concordia in summer. Using these lab data and the emission flux of NOxfrom snow estimated from the vertical gradient of atmospheric concentrations measured during the campaign, a mean diurnal HONO snow emission ranging between 0.5 and 0.8×109 molecules cm-2s-1is calculated. Model calculations indicate that, in addition to around 1.2 pptv of HONO produced by the NO oxidation, these HONO snow emissions can only explain 6.5 to 10.5 pptv of HONO in the atmosphere at Concordia. To explain the difference between observed and simulated HONO mixing ratios, tests were done both in the field and at lab to explore the possibility that the presence of HNO4had biased the measurements of HONO. Source

Kukui A.,Laboratoire des Atmospheres | Legrand M.,CNRS Laboratory for Glaciology and Environmental Geophysics | Ancellet G.,Laboratoire des Atmospheres | Gros V.,French Climate and Environment Sciences Laboratory | And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2012

Measurements of OH and total peroxy RO2 (HO2 plus organic peroxy) radicals were conducted in December 2010/January 2011 at the coastal East Antarctic site of Dumont d'Urville (DDU, 66°40'S 140°01'E) as part of the Oxidant Production over Antarctic Land and its Export (OPALE) project. Compared to measurements carried out at the West Antarctic coast, relatively high concentrations of radicals were found with 24 h average values of 2.1 × 106 and 3.3 × 108 molecule cm -3 for OH and peroxy radicals, respectively. On the basis of the steady state calculations, the observed high concentration of peroxy radicals is in good agreement with the observed levels of O3 and HCHO representing via their photolysis the major primary radical sources. The observed OH levels at DDU could be explained only assuming some RO2 to OH conversion mechanism equivalent to the presence of NO in the range of 10 to 50 pptv. As neither NO nor halogen oxides were measured at DDU the mechanism of this recycling could not be explicitly identified. However, an examination of variability of radical levels as a function of the origin (oceanic versus continental) of sampled air masses suggests a more important OH production from RO2 recycling in continental air masses. © 2012 American Geophysical Union. All Rights Reserved. Source

Grilli R.,Joseph Fourier University | Legrand M.,CNRS Laboratory for Glaciology and Environmental Geophysics | Kukui A.,Laboratoire des Atmospheres | Kukui A.,CNRS Physics Laboratory | And 3 more authors.
Geophysical Research Letters | Year: 2013

IO, BrO, and NO2 were measured for the first time at Dumont d'Urville (East Antarctic coast) during summer 2011/2012 by using a near-UV-Visible laser spectrometer based on mode-locked cavity-enhanced absorption spectroscopy. IO mixing ratios ranged from the 2σ detection limit (0.04 pptv) up to 0.15 pptv. BrO remained close or below the detection limit (2 pptv) of the instrument. Daily averaged NO2 values ranged between the detection limit (10 pptv) and 60 pptv being far higher than levels of a few pptv commonly observed in the remote marine boundary layer. Data are discussed and compared with those available for another coastal Antarctic station (Halley, West Antarctica). It is shown that the oxidative capacity of the atmospheric boundary layer at coastal Antarctic sites is quite different in nature from West to East Antarctica, with the halogen chemistry being promoted at West and the OH chemistry at East. Key Points First measurements of IO, BrO and NO2 at East Antarctica ©2013. American Geophysical Union. All Rights Reserved. Source

Preunkert S.,CNRS Laboratory for Glaciology and Environmental Geophysics | Preunkert S.,University Grenoble alpes | Legrand M.,CNRS Laboratory for Glaciology and Environmental Geophysics | Legrand M.,University Grenoble alpes | And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2015

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 mg'2 sg'1 at night and 3 and 5 × 1012 molecules mg'2 sg'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. © Author(s) 2015. CC Attribution 3.0 License. Source

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