Atmospheric nitrogen oxides (NO and NO2) at Dome C, East Antarctica, during the OPALE campaign

Mixing ratios of the atmospheric nitrogen oxides NO and NO2 were measured as part of the OPALE (Oxidant Production in Antarctic Lands & Export) campaign at Dome C, East Antarctica (75.1 degrees S, 123.3 degrees E, 3233 m), during December 2011 to January 2012. Profiles of NOx mixing ratios of the lower 100m of the atmosphere confirm that, in contrast to the South Pole, air chemistry at Dome C is strongly influenced by large diurnal cycles in solar irradiance and a sudden collapse of the atmospheric boundary layer in the early evening. Depth profiles of mixing ratios in firn air suggest that the upper snowpack at Dome C holds a significant reservoir of photolytically produced NO2 and is a sink of gas-phase ozone (O-3). First-time observations of bromine oxide (BrO) at Dome C show that mixing ratios of BrO near the ground are low, certainly less than 5 pptv, with higher levels in the free troposphere. Assuming steady state, observed mixing ratios of BrO and RO2 radicals are too low to explain the large NO2 : NO ratios found in ambient air, possibly indicating the existence of an unknown process contributing to the atmospheric chemistry of reactive nitrogen above the Antarctic Plateau. During 2011-2012, NOx mixing ratios and flux were larger than in 2009-2010, consistent with also larger surface O-3 mixing ratios resulting from increased net O-3 production. Large NOx mixing ratios at Dome C arise from a combination of continuous sunlight, shallow mixing height and significant NOx emissions by surface snow (F-NOx). During 23 December 2011-12 January 2012, median F-NOx was twice that during the same period in 20092010 due to significantly larger atmospheric turbulence and a slightly stronger snowpack source. A tripling of F-NOx in December 2011 was largely due to changes in snowpack source strength caused primarily by changes in NO3- concentrations in the snow skin layer, and only to a secondary order by decrease of total column O-3 and associated increase in NO3- photolysis rates. A source of uncertainty in model estimates of F-NOx is the quantum yield of NO3- photolysis in natural snow, which may change over time as the snow ages

Evidence of atmospheric nanoparticle formation from emissions of marine microorganisms

International audienceEarth, as a whole, can be considered as a living organism emitting gases and particles into its atmosphere, in order to regulate its own temperature. In particular, oceans may respond to climate change by emitting particles that ultimately will influence cloud coverage. At the global scale, a large fraction of the aerosol number concentration is formed by nucleation of gas-phase species, but this process has never been directly observed above oceans. Here we present, using semicontrolled seawater-air enclosures, evidence that nucleation may occur from marine biological emissions in the atmosphere of the open ocean. We identify iodine-containing species as major precursors for new particle clusters’ formation, while questioning the role of the commonly accepted dimethyl sulfide oxidation products, in forming new particle clusters in the region investigated and within a time scale on the order of an hour. We further show that amines would sustain the new particle formation process by growing the new clusters to larger sizes. Our results suggest that iodine-containing species and amines are correlated to different biological tracers. These observations, if generalized, would call for a substantial change of modeling approaches of the sea-to-air interactions

PROSPECTS OF MANUFACTURING TUNNELING AND DRILLING EQUIPMENT TOOLING IN THE RECYCLING OF HIGH-ALLOY STEELS WASTES

The technological aspects of processing and remelting of dispersed metal scrap, generated during polishing and grinding of tools made from high speed steel and carbide and lump scrap for the manufacture of drilling equipment and mining equipment are investigated

IMPROVEMENT OF THE QUALITY OF PUMPING GROUP CASTINGS

The main results of changing of high-strength antipenetration coatings in the result of development of the potentialities of their main component – refractory filler are given

The atmospheric impact of Monoterpene ozonolysis intermediates: rate constant and secondary organic aerosol formation within SO2 oxidation

International audienc

The atmospheric impact of Monoterpene ozonolysis intermediates: rate constant and secondary organic aerosol formation within SO2 oxidation

International audienc

Intercomparison of peroxy radical instruments at the HELIOS atmospheric simulation chamber

International audiencePeroxy radicals (HO 2 and RO 2 ) are key species in atmospheric chemistry, which together with the hydroxyl radical (OH), are involved in oxidation processes leading to the formation of secondary pollutants such as ozone and organic aerosols. Monitoring these short-lived species during intensive field campaigns and comparing the measured concentrations to box model simulations allow assessing the reliability of chemical mechanisms implemented in atmospheric models. However, ambient measurements of peroxy radicals are still considered challenging and only a few techniques have been used for field measurements. Three complementary instruments capable of ambient measurements of pe roxy radicals have been deployed together at the HELIOS atmospheric simulation chamber (Orléans, France) in October 2018. These instruments rely on the PEroxy Radical Chemical Amplification (PERCA), Laser Induced Fluorescence-Fluorescent Assay by Gas Expansion (LIF-FAGE), and Chemical Ionisation Mass Spectrometry (CIMS) techniques. Several chamber experiments have been conducted under dark and irradiated conditions, including oxidation experiments of dihydrogen, methane, pentene, isoprene, and α-pinene. In this presentation, the agreement between the different instruments will be discussed in the light of supporting measurements of volatile organic compounds and inorganic species (O3, NO, NO2), photolysis frequencies, as well as box modelling of the chamber chemistry

Intercomparison of peroxy radical instruments at the HELIOS atmospheric simulation chamber

International audiencePeroxy radicals (HO 2 and RO 2 ) are key species in atmospheric chemistry, which together with the hydroxyl radical (OH), are involved in oxidation processes leading to the formation of secondary pollutants such as ozone and organic aerosols. Monitoring these short-lived species during intensive field campaigns and comparing the measured concentrations to box model simulations allow assessing the reliability of chemical mechanisms implemented in atmospheric models. However, ambient measurements of peroxy radicals are still considered challenging and only a few techniques have been used for field measurements. Three complementary instruments capable of ambient measurements of pe roxy radicals have been deployed together at the HELIOS atmospheric simulation chamber (Orléans, France) in October 2018. These instruments rely on the PEroxy Radical Chemical Amplification (PERCA), Laser Induced Fluorescence-Fluorescent Assay by Gas Expansion (LIF-FAGE), and Chemical Ionisation Mass Spectrometry (CIMS) techniques. Several chamber experiments have been conducted under dark and irradiated conditions, including oxidation experiments of dihydrogen, methane, pentene, isoprene, and α-pinene. In this presentation, the agreement between the different instruments will be discussed in the light of supporting measurements of volatile organic compounds and inorganic species (O3, NO, NO2), photolysis frequencies, as well as box modelling of the chamber chemistry