scholarly journals Measurement and interpretation of gas phase formaldehyde concentrations obtained during the CHABLIS campaign in coastal Antarctica

2008 ◽  
Vol 8 (14) ◽  
pp. 4085-4093 ◽  
Author(s):  
R. A. Salmon ◽  
S. J.-B. Bauguitte ◽  
W. Bloss ◽  
M. A. Hutterli ◽  
A. E. Jones ◽  
...  
Keyword(s):  
Gas Phase ◽  
Austral Summer ◽  
Research Station ◽  
Steady State Analysis ◽  
Sources And Sinks ◽  
Data Coverage ◽  
Absolute Concentrations ◽  
Instrumental Detection Limit ◽  
Phase Production

Abstract. Gas phase formaldehyde concentrations were measured during the 2004–2005 CHABLIS campaign at Halley research station, Antarctica. Data coverage span from May 2004 through to January 2005, thus capturing the majority of the year, with a wintertime minimum of near or below the instrumental detection limit rising to between 50 and 200 pptv during the austral summer. Factors controlling HCHO concentration include local chemical sources and sinks, and exchange with the snow surface. The measured seasonality is in line with previous observations from Neumayer station, with maximum in summer and minimum during the winter months, but with lower absolute concentrations throughout the year. The gas-phase production of HCHO was dominated by methane oxidation and a steady-state analysis showed that reactions of iodine and bromine species substantially reduced the predicted HCHO levels based upon in situ chemistry. This indicates a substantial additional HCHO source to be present that could be explained by a snowpack source.

scholarly journals Measurement and interpretation of gas phase formaldehyde concentrations obtained during the CHABLIS campaign in coastal Antarctica

2008 ◽  
Vol 8 (1) ◽  
pp. 2337-2357
Author(s):  
R. A. Salmon ◽  
S. J.-B. Bauguitte ◽  
W. Bloss ◽  
M. A. Hutterli ◽  
A. E. Jones ◽  
...  
Keyword(s):  
Steady State ◽  
Gas Phase ◽  
Research Station ◽  
Snow Surface ◽  
Sources And Sinks ◽  
Oxidation Of Methane ◽  
Data Coverage ◽  
Absolute Concentrations

Abstract. Gas phase formaldehyde concentrations were measured during the 2004-5 CHABLIS campaign at Halley research station, Antarctica. Data coverage span from March 2004 through to January 2005 thus capturing the majority of the year. Factors controlling HCHO concentration include local chemical sources and sinks, and exchange with the snow surface. The measured seasonality is in line with previous observations from Neumayer station, with maximum in summer and minimum during the winter months, but with lower absolute concentrations throughout the year. Steady state calculations show oxidation of methane to be the overwhelming source of formaldehyde during the summer, with destruction dominated by photolysis and reaction with Br atoms.

scholarly journals Comparison of different methods to retrieve effective snow grain size in central Antarctica

2017 ◽  
Author(s):  
Tim Carlsen ◽  
Gerit Birnbaum ◽  
André Ehrlich ◽  
Johannes Freitag ◽  
Georg Heygster ◽  
...  
Keyword(s):  
Grain Size ◽  
Measurement System ◽  
Surface Albedo ◽  
Austral Summer ◽  
Surface Energy Budget ◽  
Research Station ◽  
Polar Regions ◽  
Radiation Measurement ◽  
In Situ Observations

Abstract. The effective size of snow grains (reff) affects the reflectivity of snow surfaces and thus the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA) was monitored for a two-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS, ground-based) and the Spectral Modular Airborne Radiation measurement sysTem (SMART, airborne). The Snow Grain Size and Pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified and applied to the ground-based and airborne observations collected in this study. Furthermore, spectral ratios of surface albedo at 1280 nm and 1100 nm wavelength were used to reduce the retrieval uncertainty. Additionally, the algorithm originally developed for cloudless conditions was adapted to handle overcast conditions. Optical in situ observations of SSA utilizing an IceCube device were used to validate the retrieval results. The SSA retrieved from CORAS observations varied between 27 m2 kg-1 and 86 m2 kg-1. Snowfall events caused distinct SSA maxima which were often followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of fresh fallen ice crystals (vice versa for reff). SSA retrieved by data from CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved by the airborne SMART observations underestimated the ground-based observations by a factor of 2.1 (overestimation of reff).

scholarly journals Summertime NO<sub>x</sub> measurements during the CHABLIS campaign: can source and sink estimates unravel observed diurnal cycles?

2012 ◽  
Vol 12 (2) ◽  
pp. 989-1002 ◽  
Author(s):  
S. J.-B. Bauguitte ◽  
W. J. Bloss ◽  
M. J. Evans ◽  
R. A. Salmon ◽  
P. S. Anderson ◽  
...  
Keyword(s):  
Gas Phase ◽  
Production Efficiency ◽  
Emission Rate ◽  
Austral Summer ◽  
Ozone Production ◽  
Research Station ◽  
Summer Period ◽  
Diurnal Cycles ◽  
Solar Noon ◽  
Halogen Oxides

Abstract. NOx measurements were conducted at the Halley Research Station, coastal Antarctica, during the austral summer period 1 January–10 February 2005. A clear NOx diurnal cycle was observed with minimum concentrations close to instrumental detection limit (5 pptv) measured between 04:00–05:00 GMT. NOx concentrations peaked (24 pptv) between 19:00–20:00 GMT, approximately 5 h after local solar noon. An optimised box model of NOx concentrations based on production from in-snow nitrate photolysis and chemical loss derives a mean noon emission rate of 3.48 × 108 molec cm−2 s−1, assuming a 100 m boundary layer mixing height, and a relatively short NOx lifetime of ~6.4 h. This emission rate compares to directly measured values ranging from 2.1 to 12.6 × 108 molec cm−2 s−1 made on 3 days at the end of the study period. Calculations of the maximum rate of NO2 loss via a variety of conventional HOx and halogen oxidation processes show that the lifetime of NOx is predominantly controlled by halogen processing, namely BrNO3 and INO3 gas-phase formation and their subsequent heterogeneous uptake. Furthermore the presence of halogen oxides is shown to significantly perturb NOx concentrations by decreasing the NO/NO2 ratio. We conclude that in coastal Antarctica, the potential ozone production efficiency of NOx emitted from the snowpack is mitigated by the more rapid NOx loss due to halogen nitrate hydrolysis.

scholarly journals In Situ Observation of Electron-Beam-Induced Formation of Nano-Structures in PbTe

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 163
Author(s):  
Iryna Zelenina ◽  
Igor Veremchuk ◽  
Yuri Grin ◽  
Paul Simon
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Atomic Scale ◽  
In Situ Observation ◽  
Nano Structures ◽  
Transmission Electron ◽  
Initial Crystal

Nano-scaled thermoelectric materials attract significant interest due to their improved physical properties as compared to bulk materials. Well-shaped nanoparticles such as nano-bars and nano-cubes were observed in the known thermoelectric material PbTe. Their extended two-dimensional nano-layer arrangements form directly in situ through electron-beam treatment in the transmission electron microscope. The experiments show the atomistic depletion mechanism of the initial crystal and the recrystallization of PbTe nanoparticles out of the microparticles due to the local atomic-scale transport via the gas phase beyond a threshold current density of the beam.

scholarly journals An Atmospheric Origin for HCN-Derived Polymers on Titan

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 965
Author(s):  
Zoé Perrin ◽  
Nathalie Carrasco ◽  
Audrey Chatain ◽  
Lora Jovanovic ◽  
Ludovic Vettier ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Formation Process ◽  
Upper Atmosphere ◽  
Gas Mixture ◽  
Space Probe ◽  
Atmospheric Haze ◽  
Formation And Evolution ◽  
Haze Formation

Titan’s haze is strongly suspected to be an HCN-derived polymer, but despite the first in situ measurements by the ESA-Huygens space probe, its chemical composition and formation process remain largely unknown. To investigate this question, we simulated the atmospheric haze formation process, experimentally. We synthesized analogues of Titan’s haze, named Titan tholins, in an irradiated N2–CH4 gas mixture, mimicking Titan’s upper atmosphere chemistry. HCN was monitored in situ in the gas phase simultaneously with the formation and evolution of the haze particles. We show that HCN is produced as long as the particles are absent, and is then progressively consumed when the particles appear and grow. This work highlights HCN as an effective precursor of Titan’s haze and confirms the HCN-derived polymer nature of the haze.

In Situ Optical Analysis of the Gas Phase during the Deposition of Silicon Carbide from Methyltrichlorosilane

1996 ◽  
Vol 143 (5) ◽  
pp. 1654-1661 ◽  
Author(s):  
M. Ganz ◽  
N. Dorval ◽  
M. Lefebvre ◽  
M. Péalat ◽  
F. Loumagne ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Gas Phase ◽  
Optical Analysis

ZIEGLER-NATTA PROPYLENE POLYMERIZATION IN GAS PHASE: PRODUCTION OF HIGHLY ISOTACTIC POLYMERS

1972 ◽  
Vol 1 (4) ◽  
pp. 327-329 ◽  
Author(s):  
Yoshiharu Doi ◽  
Ichiro Okura ◽  
Tominaga Keii
Keyword(s):  
Gas Phase ◽  
Propylene Polymerization ◽  
Phase Production

Effect of Reactor Shape and Gas Mixing on Gas Phase Production of Fine SiO2 Particles by Hydrolysis of Tetramethoxysilane

2008 ◽  
Vol 34 (2) ◽  
pp. 261-265 ◽  
Author(s):  
Toshinori Kojima ◽  
Kengo Tachi ◽  
Jun-ichi Sakai ◽  
Shigeru Kato ◽  
Shigeo Satokawa
Keyword(s):  
Gas Phase ◽  
Gas Mixing ◽  
Sio2 Particles ◽  
Hydrolysis Of ◽  
Phase Production

scholarly journals Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

2014 ◽  
Vol 7 (1) ◽  
pp. 81-93 ◽  
Author(s):  
D. J. Miller ◽  
K. Sun ◽  
L. Tao ◽  
M. A. Khan ◽  
M. A. Zondlo
Keyword(s):  
Gas Phase ◽  
Quantum Cascade Laser ◽  
High Temporal Resolution ◽  
Reduced Pressure ◽  
Total Uncertainty ◽  
Atmospheric Ammonia ◽  
Quantum Cascade ◽  
Open Path ◽  
Time Calibration

Abstract. We demonstrate a compact, open-path, quantum cascade-laser-based atmospheric ammonia sensor operating at 9.06 μm for high-sensitivity, high temporal resolution, ground-based measurements. Atmospheric ammonia (NH3) is a gas-phase precursor to fine particulate matter, with implications for air quality and climate change. Currently, NH3 sensing challenges have led to a lack of widespread in situ measurements. Our open-path sensor configuration minimizes sampling artifacts associated with NH3 surface adsorption onto inlet tubing and reduced pressure sampling cells, as well as condensed-phase partitioning ambiguities. Multi-harmonic wavelength modulation spectroscopy allows for selective and sensitive detection of atmospheric pressure-broadened absorption features. An in-line ethylene reference cell provides real-time calibration (±20% accuracy) and normalization for instrument drift under rapidly changing field conditions. The sensor has a sensitivity and noise-equivalent limit (1σ) of 0.15 ppbv NH3 at 10 Hz, a mass of ~ 5 kg and consumes ~ 50 W of electrical power. The total uncertainty in NH3 measurements is 0.20 ppbv NH3 ± 10%, based on a spectroscopic calibration method. Field performance of this open-path NH3 sensor is demonstrated, with 10 Hz time resolution and a large dynamic response for in situ NH3 measurements. This sensor provides the capabilities for improved in situ gas-phase NH3 sensing relevant for emission source characterization and flux measurements.

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