scholarly journals Why do organic aerosols exist? Understanding aerosol lifetimes using the two-dimensional volatility basis set

2013 ◽  
Vol 10 (3) ◽  
pp. 151 ◽  
Author(s):  
N. M. Donahue ◽  
W. Chuang ◽  
S. A. Epstein ◽  
J. H. Kroll ◽  
D. R. Worsnop ◽  
...  
Keyword(s):  
Human Health ◽  
Gas Phase ◽  
Fine Particles ◽  
Critical Role ◽  
Organic Aerosols ◽  
Basis Set ◽  
Oh Radicals ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Oxidation Chemistry

Environmental context Fine particles (aerosols) containing organic compounds are central players in two important environmental issues: aerosol-climate effects and human health effects (including mortality). Although organics constitute half or more of the total fine-particle mass, their chemistry is extremely complex; of critical importance is ongoing oxidation chemistry in both the gas phase and the particle phase. Here we present a method for representing that oxidation chemistry when the actual composition of the organics is not known and show that relatively slow oxidant uptake to particles plays a key role in the very existence of organic aerosols. Abstract Organic aerosols play a critical role in atmospheric chemistry, human health and climate. Their behaviour is complex. They consist of thousands of organic molecules in a rich, possibly highly viscous mixture that may or may not be in phase equilibrium with organic vapours. Because the aerosol is a mixture, compounds from all sources interact and thus influence each other. Finally, most ambient organic aerosols are highly oxidised, so the molecules are secondary products formed from primary emissions by oxidation chemistry and possibly non-oxidative association reactions in multiple phases, including gas-phase oxidation, aqueous oxidation, condensed (organic) phase reactions and heterogeneous interactions of all these phases. In spite of this complexity, we can make a strong existential statement about organic aerosol: They exist throughout the troposphere because heterogeneous oxidation by OH radicals is more than an order of magnitude slower than comparable gas-phase oxidation.

Gas-Phase Oxidation of Methyl Crotonate and Ethyl Crotonate. Kinetic Study of Their Reactions toward OH Radicals and Cl Atoms

2012 ◽  
Vol 116 (24) ◽  
pp. 6127-6133 ◽  
Author(s):  
Mariano A. Teruel ◽  
Julio Benitez-Villalba ◽  
Norma Caballero ◽  
María B. Blanco
Keyword(s):  
Kinetic Study ◽  
Gas Phase ◽  
Oh Radicals ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Cl Atoms

Gas Phase Oxidation of Nicotine by OH Radicals: Kinetics, Mechanisms, and Formation of HNCO

2016 ◽  
Vol 3 (9) ◽  
pp. 327-331 ◽  
Author(s):  
Nadine Borduas ◽  
Jennifer G. Murphy ◽  
Chen Wang ◽  
Gabriel da Silva ◽  
Jonathan P. D. Abbatt
Keyword(s):  
Gas Phase ◽  
Oh Radicals ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide

2004 ◽  
Vol 38 (25) ◽  
pp. 4093-4098 ◽  
Author(s):  
Magda Claeys ◽  
Wu Wang ◽  
Alina C Ion ◽  
Ivan Kourtchev ◽  
András Gelencsér ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Gas Phase ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Oxidation Products ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

scholarly journals An isotope view on ionising radiation as a source of sulphuric acid

2012 ◽  
Vol 12 (2) ◽  
pp. 5039-5064 ◽  
Author(s):  
M. B. Enghoff ◽  
N. Bork ◽  
S. Hattori ◽  
C. Meusinger ◽  
M. Nakagawa ◽  
...  
Keyword(s):  
Gas Phase ◽  
Sulphuric Acid ◽  
Gamma Rays ◽  
Uv Light ◽  
Isotope Ratio Mass Spectrometry ◽  
Ionising Radiation ◽  
Oh Radicals ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Mass Dependent

Abstract. Sulphuric acid is an important factor in aerosol nucleation and growth. It has been shown that ions enhance the formation of sulphuric acid aerosols, but the exact mechanism has remained undetermined. Furthermore some studies have found a deficiency in the sulphuric acid budget, suggesting a missing source. In this study the production of sulphuric acid from SO2 through a number of different pathways is investigated. The production methods are standard gas phase oxidation by OH radicals produced by ozone photolysis with UV light, liquid phase oxidation by ozone, and gas phase oxidation initiated by gamma rays. The distributions of stable sulphur isotopes in the products and substrate were measured using isotope ratio mass spectrometry. All methods produced sulphate enriched in 34S and we find a δ34S value of 8.7 ± 0.4‰ (1 standard deviation) for the UV-initiated OH reaction. Only UV light (Hg emission at 253.65 nm) produced a clear non-mass-dependent excess of 33S. The pattern of isotopic enrichment produced by gamma rays is similar, but not equal, to that produced by aqueous oxidation of SO2 by ozone. This, combined with the relative yields of the experiments, suggests a mechanism in which ionising radiation may lead to hydrated ion clusters that serve as nanoreactors for S(IV) to S(VI) conversion.

scholarly journals Biogenic SOA formation through gas-phase oxidation and gas-to-particle partitioning – comparison between process models of varying complexity

2014 ◽  
Vol 14 (8) ◽  
pp. 11001-11040
Author(s):  
E. Hermansson ◽  
P. Roldin ◽  
A. Rusanen ◽  
D. Mogensen ◽  
N. Kivekäs ◽  
...  
Keyword(s):  
Gas Phase ◽  
Global Climate Models ◽  
Process Models ◽  
Oxidation Products ◽  
Basis Set ◽  
Chemical Mechanism ◽  
Air Mass ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Air Mass Trajectory

Abstract. Biogenic volatile organic compounds (BVOCs) emitted by the vegetation play an important role for the aerosol mass loadings since the oxidation products of these compounds can take part in the formation and growth of secondary organic aerosols (SOA). The concentrations and properties of BVOCs and their oxidation products in the atmosphere are poorly characterized, which leads to high uncertainties in modeled SOA mass and properties. In this study the formation of SOA has been modeled along an air mass trajectory over the northern European boreal forest using two aerosol dynamics box models where the prediction of the condensable organics from the gas-phase oxidation of BVOC is handled with schemes of varying complexity. The use of box model simulations along an air mass trajectory allows us to, under atmospheric relevant conditions, compare different model parameterizations and their effect on SOA formation. The result of the study shows that the modeled mass concentration of SOA is highly dependent on the organic oxidation scheme used to predict the oxidation products. A near-explicit treatment of organic gas-phase oxidation (Master Chemical Mechanism version 3.2) was compared to oxidation schemes that use the volatility basis set (VBS) approach. The resulting SOA mass modeled with different VBS-schemes varies by a factor of about 7 depending on how the first generation oxidation products are parameterized and how they subsequently age (e.g. how fast the gas-phase oxidation products react with the OH-radical, how they respond to temperature changes and if they are allowed to fragment during the aging process). Since the VBS approach is frequently used in regional and global climate models due to its relatively simple treatment of the oxidation products compared to near-explicit oxidation schemes; better understanding of the abovementioned processes are needed. Compared to the most commonly used VBS-schemes, the near-explicit method produces less – but more oxidized – SOA.

scholarly journals Biogenic SOA formation through gas-phase oxidation and gas-to-particle partitioning – a comparison between process models of varying complexity

2014 ◽  
Vol 14 (21) ◽  
pp. 11853-11869 ◽  
Author(s):  
E. Hermansson ◽  
P. Roldin ◽  
A. Rusanen ◽  
D. Mogensen ◽  
N. Kivekäs ◽  
...  
Keyword(s):  
Gas Phase ◽  
Global Climate Models ◽  
Process Models ◽  
Oxidation Products ◽  
Basis Set ◽  
Chemical Mechanism ◽  
Air Mass ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Air Mass Trajectory

Abstract. Biogenic volatile organic compounds (BVOCs) emitted by vegetation play an important role for aerosol mass loadings since the oxidation products of these compounds can take part in the formation and growth of secondary organic aerosols (SOA). The concentrations and properties of BVOCs and their oxidation products in the atmosphere are poorly characterized, which leads to high uncertainties in modeled SOA mass and properties. In this study, the formation of SOA has been modeled along an air-mass trajectory over northern European boreal forest using two aerosol dynamics box models where the prediction of the condensable organics from the gas-phase oxidation of BVOC is handled with schemes of varying complexity. The use of box model simulations along an air-mass trajectory allows us to compare, under atmospheric relevant conditions, different model parameterizations and their effect on SOA formation. The result of the study shows that the modeled mass concentration of SOA is highly dependent on the organic oxidation scheme used to predict oxidation products. A near-explicit treatment of organic gas-phase oxidation (Master Chemical Mechanism version 3.2) was compared to oxidation schemes that use the volatility basis set (VBS) approach. The resulting SOA mass modeled with different VBS schemes varies by a factor of about 7 depending on how the first-generation oxidation products are parameterized and how they subsequently age (e.g., how fast the gas-phase oxidation products react with the OH radical, how they respond to temperature changes, and if they are allowed to fragment during the aging process). Since the VBS approach is frequently used in regional and global climate models due to its relatively simple treatment of the oxidation products compared to near-explicit oxidation schemes, a better understanding of the above-mentioned processes is needed. Based on the results of this study, fragmentation should be included in order to obtain a realistic SOA formation. Furthermore, compared to the most commonly used VBS schemes, the near-explicit method produces less – but more oxidized – SOA.

scholarly journals Organic peroxide and OH formation in aerosol and cloud water: laboratory evidence for this aqueous chemistry

2015 ◽  
Vol 15 (12) ◽  
pp. 17367-17396 ◽  
Author(s):  
Y. B. Lim ◽  
B. J. Turpin
Keyword(s):  
Gas Phase ◽  
Organic Compounds ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Organic Peroxide ◽  
Oh Radicals ◽  
Organic Peroxides ◽  
Aqueous Chemistry ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Aqueous chemistry in atmospheric waters (e.g., cloud droplets or wet aerosols) is well accepted as an atmospheric pathway to produce secondary organic aerosol (SOAaq). Water-soluble organic compounds with small carbon numbers (C2-C3) are precursors for SOAaq and products include organic acids, organic sulfates, and high molecular weight compounds/oligomers. Fenton reactions and the uptake of gas-phase OH radicals are considered to be the major oxidant sources for aqueous organic chemistry. However, the sources and availability of oxidants in atmospheric waters are not well understood. The degree to which OH is produced in the aqueous phase affects the balance of radical and non-radical aqueous chemistry, the properties of the resulting aerosol, and likely its atmospheric behavior. This paper demonstrates organic peroxide formation during aqueous photooxidation of methylglyoxal using ultra high resolution Fourier Transform Ion Cyclotron Resonance electrospray ionization mass spectrometry (FTICR-MS). Organic peroxides are known to form through gas-phase oxidation of volatile organic compounds. They contribute secondary organic aerosol (SOA) formation directly by forming peroxyhemiacetals, and epoxides, and indirectly by enhancing gas-phase oxidation through OH recycling. We provide simulation results of organic peroxide/peroxyhemiacetal formation in clouds and wet aerosols and discuss organic peroxides as a source of condensed-phase OH radicals and as a contributor to aqueous SOA.

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