scholarly journals Kinetic and mechanistic study of the reaction between methane sulphonamide (CH<sub>3</sub>S(O)<sub>2</sub>NH<sub>2</sub>) and OH

2019 ◽  
Author(s):  
Matias Berasategui ◽  
Damien Amedro ◽  
Achim Edtbauer ◽  
Jonathan Williams ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
Rate Coefficient ◽  
Relative Rate ◽  
Hydrogen Abstraction ◽  
Initial Step ◽  
Ambient Air ◽  
Mechanistic Study ◽  
Photo Oxidation ◽  
Mixing Ratios ◽  
In Situ Detection ◽  
First Time

Abstract. Methane sulphonamide (MSAM), CH3S(O)2NH2, has recently been detected for the first time in ambient air over the Red Sea and the Gulf of Aden where peak mixing ratios of ~ 60 pptv were recorded. Prior to this study the rate constant for its reaction with the OH radical and the products thereby formed were unknown, precluding assessment of its role in the atmosphere. We studied the OH-initiated photo-oxidation of MSAM in air (298 K, 700 Torr total pressure) in a photochemical reactor using in situ detection of MSAM and its products by FTIR absorption spectroscopy. The relative rate technique, using three different reference compounds, was used to derive a rate coefficient of (1.4 ± 0.3) ×10−13 cm3 molecule−1 s−1. The main end products of the photo-oxidation observed by FTIR were CO2, CO, SO2 and HNO3 with molar yields of (0.73 ± 0.11), (0.28 ± 0.04), (0.96 ± 0.15) and (0.62 ± 0.09), respectively. N2O and HC(O)OH were also observed in smaller yields (0.09 ± 0.02), (0.03 ± 0.01). Both the low rate coefficient and the products formed are consistent with hydrogen abstraction from the -CH3 group as the dominant initial step. Based on our results MSAM has an atmospheric lifetime with respect to loss by reaction with OH of about 80 days.

scholarly journals Kinetic and mechanistic study of the reaction between methane sulfonamide (CH<sub>3</sub>S(O)<sub>2</sub>NH<sub>2</sub>) and OH

2020 ◽  
Vol 20 (5) ◽  
pp. 2695-2707 ◽  
Author(s):  
Matias Berasategui ◽  
Damien Amedro ◽  
Achim Edtbauer ◽  
Jonathan Williams ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
Rate Coefficient ◽  
Relative Rate ◽  
Hydrogen Abstraction ◽  
Initial Step ◽  
Ambient Air ◽  
Mechanistic Study ◽  
Photo Oxidation ◽  
Mixing Ratios ◽  
In Situ Detection ◽  
First Time

Abstract. Methane sulfonamide (MSAM), CH3S(O)2NH2, was recently detected for the first time in ambient air over the Red Sea and the Gulf of Aden where peak mixing ratios of ≈60 pptv were recorded. Prior to this study the rate constant for its reaction with the OH radical and the products thereby formed were unknown, precluding assessment of its role in the atmosphere. We have studied the OH-initiated photo-oxidation of MSAM in air (298 K, 700 Torr total pressure) in a photochemical reactor using in situ detection of MSAM and its products by Fourier transform infrared (FTIR) absorption spectroscopy. The relative rate technique, using three different reference compounds, was used to derive a rate coefficient of (1.4±0.3)×10-13cm3molec.-1s-1. The main end products of the photo-oxidation observed by FTIR were CO2, CO, SO2, and HNO3 with molar yields of (0.73±0.11), (0.28±0.04), (0.96±0.15), and (0.62±0.09), respectively. N2O and HC(O)OH were also observed in smaller yields of (0.09±0.02) and (0.03±0.01). Both the low rate coefficient and the products formed are consistent with hydrogen abstraction from the −CH3 group as the dominant initial step. Based on our results MSAM has an atmospheric lifetime with respect to loss by reaction with OH of about 80 d.

scholarly journals A self-consistent, multivariate method for the determination of gas-phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical

2018 ◽  
Vol 18 (6) ◽  
pp. 4039-4054 ◽  
Author(s):  
Jacob T. Shaw ◽  
Richard T. Lidster ◽  
Danny R. Cryer ◽  
Noelia Ramirez ◽  
Fiona C. Whiting ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Ambient Air ◽  
Rate Coefficients ◽  
Oxidation Reactions ◽  
Simultaneous Study ◽  
The University ◽  
Good Agreement

Abstract. Gas-phase rate coefficients are fundamental to understanding atmospheric chemistry, yet experimental data are not available for the oxidation reactions of many of the thousands of volatile organic compounds (VOCs) observed in the troposphere. Here, a new experimental method is reported for the simultaneous study of reactions between multiple different VOCs and OH, the most important daytime atmospheric radical oxidant. This technique is based upon established relative rate concepts but has the advantage of a much higher throughput of target VOCs. By evaluating multiple VOCs in each experiment, and through measurement of the depletion in each VOC after reaction with OH, the OH + VOC reaction rate coefficients can be derived. Results from experiments conducted under controlled laboratory conditions were in good agreement with the available literature for the reaction of 19 VOCs, prepared in synthetic gas mixtures, with OH. This approach was used to determine a rate coefficient for the reaction of OH with 2,3-dimethylpent-1-ene for the first time; k =  5.7 (±0.3)  ×  10−11 cm3 molecule−1 s−1. In addition, a further seven VOCs had only two, or fewer, individual OH rate coefficient measurements available in the literature. The results from this work were in good agreement with those measurements. A similar dataset, at an elevated temperature of 323 (±10) K, was used to determine new OH rate coefficients for 12 aromatic, 5 alkane, 5 alkene and 3 monoterpene VOC + OH reactions. In OH relative reactivity experiments that used ambient air at the University of York, a large number of different VOCs were observed, of which 23 were positively identified. Due to difficulties with detection limits and fully resolving peaks, only 19 OH rate coefficients were derived from these ambient air samples, including 10 reactions for which data were previously unavailable at the elevated reaction temperature of T =  323 (±10) K.

scholarly journals A self-consistent, multi-variate method for the determination of gas phase rate coefficients, applied to reactions of atmospheric VOCs and the hydroxyl radical

2017 ◽  
Author(s):  
Jacob T. Shaw ◽  
Richard T. Lidster ◽  
Danny R. Cryer ◽  
Noelia Ramirez ◽  
Graham A. Boustead ◽  
...  
Keyword(s):  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Ambient Air ◽  
Rate Coefficients ◽  
Oxidation Reactions ◽  
Oh Reactions ◽  
Simultaneous Study ◽  
Good Agreement

Abstract. Gas-phase rate coefficients are fundamental to understanding atmospheric chemistry, yet experimental data are not available for the oxidation reactions of many of the thousands of volatile organic compounds (VOCs) observed in the troposphere. Here a new experimental method is reported for the simultaneous study of reactions between multiple different VOCs and OH, the most important daytime atmospheric radical oxidant. This technique is based upon established relative rate concepts but has the advantage of a much higher throughput of target VOCs. By evaluating multiple VOCs in each experiment, and through measurement of the depletion in each VOC after reaction with OH, the OH + VOC reaction rate coefficients can be derived. Results from experiments conducted under controlled laboratory conditions were in good agreement with the available literature for the reaction of nineteen VOCs, prepared in synthetic gas mixtures, with OH. This approach was used to determine a rate coefficient for the reaction of OH with 2,3-dimethylpent-1-ene for the first time; k = 5.7 (&amp;pm;0.3) × 10–11–cm3 molecule−1 s−1. In addition, a further seven VOCs had only two, or fewer, individual OH rate coefficient measurements available in the literature. The results from this work were in good agreement with those measurements. A similar dataset, at an elevated temperature of 323 (±10) K, was used to determine new OH rate coefficients for twelve aromatic, five alkane, five alkene and three monoterpene VOC + OH reactions. In OH relative reactivity experiments that used ambient air at the University of York, a large number of different VOCs were observed, of which 23 were positively identified. 19 OH rate coefficients were derived from these ambient air samples, including ten reactions for which data was previously unavailable at the elevated reaction temperature of T = 323 (±10) K.

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

2015 ◽  
Vol 15 (12) ◽  
pp. 6689-6705 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand ◽  
M. M. Frey ◽  
A. Kukui ◽  
J. Savarino ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ambient Air ◽  
Snow Surface ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
Emission Fluxes ◽  
Oxidation Chemistry ◽  
First Time ◽  
Phase Production ◽  
Interstitial Air

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.

scholarly journals Formaldehyde (HCHO) in air, snow and interstitial air at Concordia (East Antarctic plateau) in summer

2014 ◽  
Vol 14 (23) ◽  
pp. 32027-32070 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand ◽  
M. Frey ◽  
A. Kukui ◽  
J. Savarino ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ambient Air ◽  
Snow Surface ◽  
Snow Pack ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
Emission Fluxes ◽  
Oxidation Chemistry ◽  
First Time ◽  
Interstitial Air

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 analyser. Snow emission fluxes were estimated from vertical gradients of mixing ratios observed between 1 cm and 1 m above the snow surface as well as between interstitial air a few cm below the surface and in air just above the snow-pack. Typical flux values range between 1 to 2 × 1012 molecules m−2 s−1 at night and 3 to 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.

scholarly journals The Impact of Ambient Atmospheric Mineral-Dust Particles on the Calcification of Lungs

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 125
Author(s):  
Mariola Jabłońska ◽  
Janusz Janeczek ◽  
Beata Smieja-Król
Keyword(s):  
Mineral Dust ◽  
Smoking Habit ◽  
Lower Lobe ◽  
Ambient Air ◽  
Dust Particles ◽  
Masking Effect ◽  
Amorphous Calcium Carbonate ◽  
Calcium Salts ◽  
The Impact ◽  
First Time

For the first time, it is shown that inhaled ambient air-dust particles settled in the human lower respiratory tract induce lung calcification. Chemical and mineral compositions of pulmonary calcium precipitates in the lung right lower-lobe (RLL) tissues of 12 individuals who lived in the Upper Silesia conurbation in Poland and who had died from causes not related to a lung disorder were determined by transmission and scanning electron microscopy. Whereas calcium salts in lungs are usually reported as phosphates, calcium salts precipitated in the studied RLL tissue were almost exclusively carbonates, specifically Mg-calcite and calcite. These constituted 37% of the 1652 mineral particles examined. Mg-calcite predominated in the submicrometer size range, with a MgCO3 content up to 50 mol %. Magnesium plays a significant role in lung mineralization, a fact so far overlooked. The calcium phosphate (hydroxyapatite) content in the studied RLL tissue was negligible. The predominance of carbonates is explained by the increased CO2 fugacity in the RLL. Carbonates enveloped inhaled mineral-dust particles, including uranium-bearing oxides, quartz, aluminosilicates, and metal sulfides. Three possible pathways for the carbonates precipitation on the dust particles are postulated: (1) precipitation of amorphous calcium carbonate (ACC), followed by its transformation to calcite; (2) precipitation of Mg-ACC, followed by its transformation to Mg-calcite; (3) precipitation of Mg-free ACC, causing a localized relative enrichment in Mg ions and subsequent heterogeneous nucleation and crystal growth of Mg-calcite. The actual number of inhaled dust particles may be significantly greater than was observed because of the masking effect of the carbonate coatings. There is no simple correlation between smoking habit and lung calcification.

scholarly journals High resolution nanoscale chemical analysis of bitumen surface microstructures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ayse N. Koyun ◽  
Julia Zakel ◽  
Sven Kayser ◽  
Hartmut Stadler ◽  
Frank N. Keutsch ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Force Microscopy ◽  
Photo Oxidation ◽  
Atomic Force ◽  
Para Phase ◽  
Key Sites ◽  
Respective Surface ◽  
Surface Domains ◽  
Surface Microstructures ◽  
First Time

AbstractSurface microstructures of bitumen are key sites in atmospheric photo-oxidation leading to changes in the mechanical properties and finally resulting in cracking and rutting of the material. Investigations at the nanoscale remain challenging. Conventional combination of optical microscopy and spectroscopy cannot resolve the submicrostructures due to the Abbe restriction. For the first time, we report here respective surface domains, namely catana, peri and para phases, correlated to distinct molecules using combinations of atomic force microscopy with infrared spectroscopy and with correlative time of flight—secondary ion mass spectrometry. Chemical heterogeneities on the surface lead to selective oxidation due to their varying susceptibility to photo-oxidation. It was found, that highly oxidized compounds, are preferentially situated in the para phase, which are mainly asphaltenes, emphasising their high oxidizability. This is an impressive example how chemical visualization allows elucidation of the submicrostructures and explains their response to reactive oxygen species from the atmosphere.

scholarly journals Uptake of NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> to Saharan dust, ambient urban aerosol and soot: a relative rate study

2010 ◽  
Vol 10 (6) ◽  
pp. 2965-2974 ◽  
Author(s):  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Mineral Dust ◽  
Relative Rate ◽  
Simultaneous Detection ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Ambient Aerosols ◽  
Mixing Ratios ◽  
A Value ◽  
Rate Study ◽  
Absolute Basis

Abstract. The uptake of NO3 and N2O5 to Saharan dust, ambient aerosols and soot was investigated using a novel and simple relative rate method with simultaneous detection of both NO3 and N2O5. The use of cavity ring down spectroscopy to detect both trace gases enabled the measurements to be carried out at low mixing ratios (<500 pptv or 1×1010 molecule cm−3). The uptake coefficient ratio, γ(NO3)/γ(N2O5), was determined to be 0.9±0.4 for Saharan dust, independent of relative humidity, NO3 or N2O5 mixing ratio and exposure time. Ambient (urban) aerosols showed a very limited capacity to take up N2O5 but were reactive towards NO3 with γ(NO3)/γ(N2O5)>15. A value of γ(NO3)/γ(N2O5)~1.5–3 was obtained when using candle generated soot. The relative rate obtained for Saharan dust can be placed on an absolute basis using our recently determined value of γ(N2O5)=1×10−2 to give γ(NO3)=9×10−3, which is significantly smaller than the single previous value. With the present uptake coefficient, reaction of NO3 with mineral dust will generally not contribute significantly to its NO3 loss in the boundary atmosphere or to the nitration of mineral dust.

scholarly journals Experimental pieces of evidence for Mycobacterium ulcerans dormancy

2020 ◽  
Author(s):  
A. Loukil ◽  
R. Lalaoui ◽  
H. Bogreau ◽  
S. Regoui ◽  
M. Drancourt ◽  
...  
Keyword(s):  
Physiological State ◽  
Nile Red ◽  
Buruli Ulcer ◽  
Ambient Air ◽  
Opportunistic Pathogen ◽  
Oxygen Depletion ◽  
Mycobacterium Ulcerans ◽  
Ecological Niches ◽  
Intracellular Lipid ◽  
First Time

ABSTRACTBackgroundWhether Mycobacterium ulcerans, the etiological agent of the neglected Buruli ulcer in numerous tropical countries, would exist in a dormant state as reported for closely related Mycobacterium species, is not established.MethodologySix M. ulcerans strains were exposed to a progressive depletion in oxygen for two months, using a previously described Wayne model of dormancy; and further examined by microscopy using DDD staining, microcalorimetry and subculture in the presence of dead and replicative M. ulcerans as controls.Principal Findings/ConclusionsM. ulcerans CU001 strain died during the progressive oxygen depletion and four of five remaining strains exhibited Nile Red-stained intracellular lipid droplets after DDD staining and a 14-20-day regrowth when exposed to ambient air, diagnosing dormancy. A fifth M. ulcerans 19423 strain stained negative in DDD and slowly regrew in 27 days. Three tested M. ulcerans strains yielded microcalorimetric pattern similar to that of the negative (dead) homologous controls, differing from that of the homologous positive (replicative) controls. The relevance of these experimental observations, suggesting a previously unreported dormancy state of M. ulcerans, needs to be investigated in the natural ecological niches where M. ulcerans thrive and in Buruli ulcer lesions.Author summaryMycobacterium ulcerans is an environmental opportunistic pathogen of mammals and humans, causing a subcutaneous necrotizing infection named Buruli ulcer. Molecular detection of M. ulcerans DNA revealed different ecological niches where M. ulcerans may thrive, but the molecular biology approach does not catch the physiological state of M. ulcerans in these different ecological niches. Thus, the reservoir and the mode of transmission of M. ulcerans remain elusive. Here, we investigated experimental dormancy of M. ulcerans by using a previously described Wayne model of dormancy coupled with microscopy using DDD staining, microcalorimetry and subculture. Our findings demonstrate for the first time that some M. ulcerans strains exhibit a physiological state of dormancy; potentially limiting isolation and culture of M. ulcerans from environmental niches.

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