ChemInform Abstract: Radical Chemistry in the Gas Phase

ChemInform ◽  
2012 ◽  
Vol 43 (37) ◽  
pp. no-no
Author(s):  
Christian Alcaraz ◽  
Ingo Fischer ◽  
Detlef Schroeder
Keyword(s):  
Gas Phase ◽  
Radical Chemistry

scholarly journals Aqueous chemistry and its role in secondary organic aerosol (SOA) formation

2010 ◽  
Vol 10 (21) ◽  
pp. 10521-10539 ◽  
Author(s):  
Y. B. Lim ◽  
Y. Tan ◽  
M. J. Perri ◽  
S. P. Seitzinger ◽  
B. J. Turpin
Keyword(s):  
Organic Acids ◽  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Base Catalysis ◽  
Radical Reactions ◽  
Oh Radicals ◽  
Aqueous Chemistry ◽  
Radical Chemistry

Abstract. There is a growing understanding that secondary organic aerosol (SOA) can form through reactions in atmospheric waters (i.e., clouds, fogs, and aerosol water). In clouds and wet aerosols, water-soluble organic products of gas-phase photochemistry dissolve into the aqueous phase where they can react further (e.g., with OH radicals) to form low volatility products that are largely retained in the particle phase. Organic acids, oligomers and other products form via radical and non-radical reactions, including hemiacetal formation during droplet evaporation, acid/base catalysis, and reaction of organics with other constituents (e.g., NH4+). This paper provides an overview of SOA formation through aqueous chemistry, including atmospheric evidence for this process and a review of radical and non-radical chemistry, using glyoxal as a model precursor. Previously unreported analyses and new kinetic modeling are reported herein to support the discussion of radical chemistry. Results suggest that reactions with OH radicals tend to be faster and form more SOA than non-radical reactions. In clouds these reactions yield organic acids, whereas in wet aerosols they yield large multifunctional humic-like substances formed via radical-radical reactions and their O/C ratios are near 1.

scholarly journals Substantial secondary organic aerosol formation in a coniferous forest: observations of both day and night time chemistry

2015 ◽  
Vol 15 (20) ◽  
pp. 28005-28035 ◽  
Author(s):  
A. K. Y. Lee ◽  
J. P. D. Abbatt ◽  
W. R. Leaitch ◽  
S.-M. Li ◽  
S. J. Sjostedt ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Coniferous Forest ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Aerosol Formation ◽  
Radical Chemistry ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region at Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas-particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 will arise from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by the OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22–33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol, and so f91 is used as an indicator of BSOA formation pathways. A comparison between laboratory studies in the literature and our field observations highlights the potential importance of gas-phase formation chemistry of BSOA-2 type materials that may not be captured in smog chamber experiments, perhaps due to the wall loss of gas-phase intermediate products.

scholarly journals Gas-Phase Radical Chemistry in the Troposphere

ChemInform ◽  
2005 ◽  
Vol 36 (33) ◽  
Author(s):  
Paul S. Monks
Keyword(s):  
Gas Phase ◽  
Radical Chemistry

scholarly journals Substantial secondary organic aerosol formation in a coniferous forest: observations of both day- and nighttime chemistry

2016 ◽  
Vol 16 (11) ◽  
pp. 6721-6733 ◽  
Author(s):  
Alex K. Y. Lee ◽  
Jonathan P. D. Abbatt ◽  
W. Richard Leaitch ◽  
Shao-Meng Li ◽  
Steve J. Sjostedt ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Coniferous Forest ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Aerosol Formation ◽  
Radical Chemistry ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region in Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas–particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 arises from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is likely less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22–33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol. Using f91 to evaluate BSOA formation pathways in this unpolluted, forested region, heterogeneous oxidation of BSOA-1 is a minor production pathway of BSOA-2.

scholarly journals Air–snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS – Part 1: In-snow bromine activation and its impact on ozone

2014 ◽  
Vol 14 (8) ◽  
pp. 4101-4133 ◽  
Author(s):  
K. Toyota ◽  
J. C. McConnell ◽  
R. M. Staebler ◽  
A. P. Dastoor
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Ambient Air ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Radical Chemistry ◽  
Ozone Loss ◽  
Key Species

Abstract. To provide a theoretical framework towards a better understanding of ozone depletion events (ODEs) and atmospheric mercury depletion events (AMDEs) in the polar boundary layer, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents from porous snowpack and through the atmospheric boundary layer (ABL) as a unified system. This paper constitutes Part 1 of the study, describing a general configuration of the model and the results of simulations related to reactive bromine release from the snowpack and ODEs during the Arctic spring. A common set of aqueous-phase reactions describes chemistry both within the liquid-like layer (LLL) on the grain surface of the snowpack and within deliquesced "haze" aerosols mainly composed of sulfate in the atmosphere. Gas-phase reactions are also represented by the same mechanism in the atmosphere and in the snowpack interstitial air (SIA). Consequently, the model attains the capacity of simulating interactions between chemistry and mass transfer that become particularly intricate near the interface between the atmosphere and the snowpack. In the SIA, reactive uptake on LLL-coated snow grains and vertical mass transfer act simultaneously on gaseous HOBr, a fraction of which enters from the atmosphere while another fraction is formed via gas-phase chemistry in the SIA itself. A "bromine explosion", by which HOBr formed in the ambient air is deposited and then converted heterogeneously to Br2, is found to be a dominant process of reactive bromine formation in the top 1 mm layer of the snowpack. Deeper in the snowpack, HOBr formed within the SIA leads to an in-snow bromine explosion, but a significant fraction of Br2 is also produced via aqueous radical chemistry in the LLL on the surface of the snow grains. These top- and deeper-layer productions of Br2 both contribute to the release of Br2 to the atmosphere, but the deeper-layer production is found to be more important for the net outflux of reactive bromine. Although ozone is removed via bromine chemistry, it is also among the key species that control both the conventional and in-snow bromine explosions. On the other hand, aqueous-phase radical chemistry initiated by photolytic OH formation in the LLL is also a significant contributor to the in-snow source of Br2 and can operate without ozone, whereas the delivery of Br2 to the atmosphere becomes much smaller after ozone is depleted. Catalytic ozone loss via bromine radical chemistry occurs more rapidly in the SIA than in the ambient air, giving rise to apparent dry deposition velocities for ozone from the air to the snow on the order of 10−3 cm s−1 during daytime. Overall, however, the depletion of ozone in the system is caused predominantly by ozone loss in the ambient air. Increasing depth of the turbulent ABL under windy conditions will delay the buildup of reactive bromine and the resultant loss of ozone, while leading to the higher column amount of BrO in the atmosphere. During the Arctic spring, if moderately saline and acidic snowpack is as prevalent as assumed in our model runs on sea ice, the shallow, stable ABL under calm weather conditions may undergo persistent ODEs without substantial contributions from blowing/drifting snow and wind-pumping mechanisms, whereas the column densities of BrO in the ABL will likely remain too low in the course of such events to be detected unambiguously by satellite nadir measurements.

scholarly journals Gas-phase radical chemistry in the troposphere

2005 ◽  
Vol 34 (5) ◽  
pp. 376 ◽  
Author(s):  
Paul S. Monks
Keyword(s):  
Gas Phase ◽  
Radical Chemistry
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