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 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.

Probing aerosol formation by comprehensive measurements of gas phase oxidation products

2013 ◽  
Author(s):  
Mikael Ehn ◽  
Einhard Kleist ◽  
Heikki Junninen ◽  
Mikko Sipilä ◽  
Tuukka Petäjä ◽  
...  
Keyword(s):  
Gas Phase ◽  
Oxidation Products ◽  
Aerosol Formation ◽  
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 Comprehensive Atmospheric Modeling of Reactive Cyclic Siloxanes and Their Oxidation Products

2017 ◽  
Author(s):  
Nathan J. Janechek ◽  
Kaj M. Hansen ◽  
Charles O. Stanier
Keyword(s):  
Gas Phase ◽  
Rural Areas ◽  
Seasonal Variability ◽  
Urban Areas ◽  
Parent Compound ◽  
Atmospheric Modeling ◽  
Oxidation Products ◽  
Aerosol Formation ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Cyclic volatile methyl siloxanes (cVMS) are important components in personal care products that transport and react in the atmosphere. Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and their gas phase oxidation products have been incorporated into the Community Multiscale Air Quality (CMAQ) model. Gas phase oxidation products, as the precursor to secondary organic aerosol from this compound class, were included to quantify the maximum potential for aerosol formation from gas phase reactions with OH. Four 1-month periods were modeled to quantify typical concentrations, seasonal variability, spatial patterns, and vertical profiles. Typical model concentrations showed parent compounds were highly dependent on population density as cities had monthly averaged peak D5 concentrations up to 432 ng m−3. Peak oxidized D5 concentrations were significantly less, up to 9 ng m−3 and were located downwind of major urban areas. Model results were compared to available measurements and previous simulation results. Seasonal variation was analyzed and differences in seasonal influences were observed between urban and rural locations. Parent compound concentrations in urban and peri-urban locations were sensitive to transport factors, while parent compounds in rural areas and oxidized product concentrations were influenced by large-scale seasonal variability in OH.

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.

scholarly journals Comprehensive atmospheric modeling of reactive cyclic siloxanes and their oxidation products

2017 ◽  
Vol 17 (13) ◽  
pp. 8357-8370 ◽  
Author(s):  
Nathan J. Janechek ◽  
Kaj M. Hansen ◽  
Charles O. Stanier
Keyword(s):  
Gas Phase ◽  
Rural Areas ◽  
Seasonal Variability ◽  
Urban Areas ◽  
Parent Compound ◽  
Atmospheric Modeling ◽  
Oxidation Products ◽  
Aerosol Formation ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Cyclic volatile methyl siloxanes (cVMSs) are important components in personal care products that transport and react in the atmosphere. Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and their gas-phase oxidation products have been incorporated into the Community Multiscale Air Quality (CMAQ) model. Gas-phase oxidation products, as the precursor to secondary organic aerosol from this compound class, were included to quantify the maximum potential for aerosol formation from gas-phase reactions with OH. Four 1-month periods were modeled to quantify typical concentrations, seasonal variability, spatial patterns, and vertical profiles. Typical model concentrations showed parent compounds were highly dependent on population density as cities had monthly averaged peak D5 concentrations up to 432 ng m−3. Peak oxidized D5 concentrations were significantly less, up to 9 ng m−3, and were located downwind of major urban areas. Model results were compared to available measurements and previous simulation results. Seasonal variation was analyzed and differences in seasonal influences were observed between urban and rural locations. Parent compound concentrations in urban and peri-urban locations were sensitive to transport factors, while parent compounds in rural areas and oxidized product concentrations were influenced by large-scale seasonal variability in OH.

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