Fundamental Time Scales Governing Organic Aerosol Multiphase Partitioning and Oxidative Aging

2015 ◽  
Vol 49 (16) ◽  
pp. 9768-9777 ◽  
Author(s):  
Haofei Zhang ◽  
David R. Worton ◽  
Steve Shen ◽  
Theodora Nah ◽  
Gabriel Isaacman-VanWertz ◽  
...  
Keyword(s):  
Time Scales ◽  
Organic Aerosol ◽  
Oxidative Aging

scholarly journals Characterization of secondary organic aerosol from heated-cooking-oil emissions: evolution in composition and volatility

2021 ◽  
Vol 21 (6) ◽  
pp. 5137-5149 ◽  
Author(s):  
Manpreet Takhar ◽  
Yunchun Li ◽  
Arthur W. H. Chan
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Carbon Number ◽  
Complex Mixture ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Atmospheric Evolution ◽  
Oxidative Aging ◽  
Cooking Oil

Abstract. Cooking emissions account for a major fraction of urban organic aerosol. It is therefore important to understand the atmospheric evolution in the physical and chemical properties of organic compounds emitted from cooking activities. In this work, we investigate the formation of secondary organic aerosol (SOA) from oxidation of gas-phase organic compounds from heated cooking oil. The chemical composition of cooking SOA is analyzed using thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS). While the particle-phase composition of SOA is a highly complex mixture, we adopt a new method to achieve molecular speciation of the SOA. All the GC-elutable material is classified by the constituent functional groups, allowing us to provide a molecular description of its chemical evolution upon oxidative aging. Our results demonstrate an increase in average oxidation state (from −0.6 to −0.24) and decrease in average carbon number (from 5.2 to 4.9) with increasing photochemical aging of cooking oil, suggesting that fragmentation reactions are key processes in the oxidative aging of cooking emissions within 2 d equivalent of ambient oxidant exposure. Moreover, we estimate that aldehyde precursors from cooking emissions account for a majority of the SOA formation and oxidation products. Overall, our results provide insights into the atmospheric evolution of cooking SOA, a majority of which is derived from gas-phase oxidation of aldehydes.

scholarly journals Appearance of strong absorbers and fluorophores in limonene-O3secondary organic aerosol due to NH4+-mediated chemical aging over long time scales

2010 ◽  
Vol 115 (D5) ◽  
Author(s):  
David L. Bones ◽  
Dana K. Henricksen ◽  
Stephen A. Mang ◽  
Michael Gonsior ◽  
Adam P. Bateman ◽  
...  
Keyword(s):  
Time Scales ◽  
Organic Aerosol ◽  
Chemical Aging ◽  
Long Time

scholarly journals Characterization of secondary organic aerosol from heated cooking oil emissions: evolution in composition and volatility

2020 ◽  
Author(s):  
Manpreet Takhar ◽  
Yunchun Li ◽  
Arthur W. H. Chan
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Carbon Number ◽  
Complex Mixture ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Atmospheric Evolution ◽  
Oxidative Aging ◽  
Cooking Oil

Abstract. Cooking emissions account for a major fraction of urban organic aerosol. It is therefore important to understand the atmospheric evolution in the physical and chemical properties of organic compounds emitted from cooking activities. In this work, we investigate the formation of secondary organic aerosol (SOA) from oxidation of gas-phase organic compounds from heated cooking oil. The chemical composition of cooking SOA is analyzed using thermal desorption-gas chromatography-mass spectrometry. While the particle-phase composition of SOA is a highly complex mixture, we adopt a new method to achieve molecular speciation of the SOA. All the GC elutable material is classified by the constituent functional groups, allowing us to provide a molecular description of its chemical evolution upon oxidative aging. Our results demonstrate an increase in average oxidation state (from −0.6 to −0.24), and decrease in average carbon number (from 5.2 to 4.9) with increasing photochemical aging of cooking oil, suggesting that fragmentation reactions are key processes in the oxidative aging of cooking emissions within 2 days equivalent of ambient oxidant exposure. Moreover, we estimate that aldehyde precursors from cooking emissions account for a majority of the SOA formation and oxidation products. Overall, our results provide insights into the atmospheric evolution of cooking SOA, a majority of which is derived from gas-phase oxidation of aldehydes.

a-pinene autoxidation at sub-second time-scales

2020 ◽  
Author(s):  
Matti Rissanen ◽  
Shawon Barua ◽  
Jordan Krechmer ◽  
Theo Kurtén ◽  
Siddharth Iyer
Keyword(s):  
Reaction Time ◽  
Organic Compounds ◽  
Time Scales ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Computational Study ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Ionization Mass

<p>Atmospheric aerosols impact climate and health. Most of the smallest atmospheric nanoparticles are formed by oxidation of volatile organic compounds (VOC) and subsequent condensation of resulting low-volatile vapors. Biogenic terpenes are the largest atmospheric secondary organic aerosol (SOA) source, and among these, a-pinene likely the single most important compound.</p><p> Recently, autoxidation changed the paradigm of long processing time-scales in the formation of SOA [1, 2]. Previous experiments with cyclic unsaturated compounds have indicated the autoxidation to be very rapid, forming compounds with even 10 O-atoms infused to the carbon structure in a few seconds timeframe [3-6]. Berndt et al. noted that the whole process was apparently finished already at about 1.5 seconds reaction time in cyclohexene ozonolysis initiated autoxidation, indicated by the “frozen” peroxy radical product distribution beyond this reaction time [4].</p><p>Here we performed sub-second time-scale flow reactor experiments of a-pinene ozonolysis initiated autoxidation under ambient atmospheric conditions to constrain the timeframe needed to form the first highly-oxidized reaction products, and to inspect the peroxy radical dynamics at significantly shorter reaction times than have been previously possible. The shortest achievable reaction time was around 0.1 seconds and was enabled by the new Multi-scheme chemical IONization (MION) inlet setup [7]. Nitrate and bromide were used as reagent ions in this work.</p><p> </p><p><strong>References:</strong></p><ol><li>J. D. Crounse, et al. Autoxidation of Organic Compounds in the Atmosphere, J. Phys. Chem. Lett., 2013, 4, 3513-3520.</li> <li>M. Ehn, et al. A large source of low-volatility secondary organic aerosol, Nature, 2014, 506, 476-479.</li> <li>M. P. Rissanen, et al. The formation of highly oxidized multifunctional products in the ozonolysis of cyclohexene, J. Am. Chem. Soc., 2014, 136, 15596-15606.</li> <li>T. Berndt, et al. Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO<sub>2</sub> Radicals and Their Reactions with NO, NO<sub>2</sub>, SO<sub>2</sub>, and Other RO<sub>2</sub> Radicals, J. Phys. Chem. A, 2015, 119, 10336-10348.</li> <li>M. P. Rissanen, et al. Kulmala, Effects of Chemical Complexity on the Autoxidation Mechanisms of Endocyclic Alkene Ozonolysis Products: From Methylcyclohexenes toward Understanding α-Pinene, J. Phys. Chem. A, 2015, 119, 4633-4650.</li> <li>T. Kurtén, et al. Computational Study of Hydrogen Shifts and Ring-Opening Mechanisms in α-Pinene Ozonolysis Products, J. Phys. Chem. A, 2015, 119, 11366-11375.</li> <li>M. P. Rissanen, et al. Multi-scheme chemical ionization inlet (MION) for fast switching of reagent ion chemistry in atmospheric pressure chemical ionization mass spectrometry (CIMS) applications, Atmos. Meas. Tech., 2019, 12, 6635-6646.</li> </ol>

Effect of heterogeneous oxidative aging on light absorption by biomass burning organic aerosol

2019 ◽  
Vol 53 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Eleanor C. Browne ◽  
Xiaolu Zhang ◽  
Jonathan P. Franklin ◽  
Kelsey J. Ridley ◽  
Thomas W. Kirchstetter ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Light Absorption ◽  
Organic Aerosol ◽  
Oxidative Aging

Equilibration time scales of organic aerosol inside thermodenuders: Evaporation kinetics versus thermodynamics

2010 ◽  
Vol 44 (5) ◽  
pp. 597-607 ◽  
Author(s):  
Ilona Riipinen ◽  
Jeffrey R. Pierce ◽  
Neil M. Donahue ◽  
Spyros N. Pandis
Keyword(s):  
Time Scales ◽  
Organic Aerosol ◽  
Equilibration Time ◽  
Evaporation Kinetics

LVSEM: Past Present and Future

1990 ◽  
Vol 48 (1) ◽  
pp. 364-365
Author(s):  
James B. Pawley
Keyword(s):  
Field Emission ◽  
Line Width ◽  
Time Scales ◽  
Silicon Oxide ◽  
Beam Current ◽  
High Brightness ◽  
High Beam ◽  
Fixed Charges ◽  
Beam Voltage ◽  
Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

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