Outdoor smog-chamber experiments: reactivity of methanol exhaust

1985 ◽  
Author(s):  
H. E. Jeffries ◽  
K. G. Sexton ◽  
M. S. Holleman
Keyword(s):  
Smog Chamber

scholarly journals Development of a secondary organic aerosol formation mechanism: comparison with smog chamber experiments and atmospheric measurements

2007 ◽  
Vol 7 (3) ◽  
pp. 8361-8393 ◽  
Author(s):  
L. E. Olcese ◽  
J. E. Penner ◽  
S. Sillman
Keyword(s):  
New England ◽  
Formation Mechanism ◽  
General Circulation ◽  
Circulation Model ◽  
Average Error ◽  
Smog Chamber ◽  
Vapor Pressures ◽  
Aerosol Formation ◽  
Atmospheric Measurements ◽  
Chamber Measurements

Abstract. A new mechanism to simulate the formation of secondary organic aerosols (SOA) from reactive primary hydrocarbons is presented, together with comparisons with experimental smog chamber results and ambient measurements found in the literature. The SOA formation mechanism is based on an approach using calculated vapor pressures and a selection of species that can partition to the aerosol phase from a gas phase photochemical mechanism. The mechanism has been validated against smog chamber measurements using α-pinene, xylene and toluene as SOA precursors, and has an average error of 17%. Qualitative comparisons with smog chamber measurements using isoprene were also performed. A comparison against SOA production in the TORCH 2003 experiment (atmospheric measurements) had an average error of only 12%. This contrasts with previous efforts, in which it was necessary to increase partition coefficients by a factor of 500 in order to match the observed values. Calculations for rural and urban-influenced regions in the eastern U.S. suggest that most of the SOA is biogenic in origin, mainly originated from isoprene. A 0-dimensional calculation based on the New England Air Quality Study also showed good agreement with measured SOA, with about 40% of the total SOA from anthropogenic precursors. This mechanism can be implemented in a general circulation model (GCM) to estimate global SOA formation under ambient NOx and HOx levels.

scholarly journals Impact of aftertreatment devices on primary emissions and secondary organic aerosol formation potential from in-use diesel vehicles: results from smog chamber experiments

2010 ◽  
Vol 10 (6) ◽  
pp. 16055-16109 ◽  
Author(s):  
R. Chirico ◽  
P. F. DeCarlo ◽  
M. F. Heringa ◽  
T. Tritscher ◽  
R. Richter ◽  
...  
Keyword(s):  
Urban Areas ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Catalyst ◽  
Particulate Filter ◽  
Exhaust Aftertreatment ◽  
Smog Chamber ◽  
Aerosol Formation ◽  
Diesel Particulate ◽  
Diesel Vehicles

Abstract. Diesel particulate matter (DPM) is a significant source of aerosol in urban areas and has been linked to adverse health effects. Although newer European directives have introduced increasingly stringent standards for primary PM emissions, gaseous organics emitted from diesel cars can still lead to large amounts of secondary organic aerosol (SOA) in the atmosphere. Here we present results from smog chamber investigations characterizing the primary organic aerosol (POA) and the corresponding SOA formation at atmospherically relevant concentrations for three in-use diesel vehicles with different exhaust aftertreatment systems. One vehicle lacked exhaust aftertreatment devices, one vehicle was equipped with a diesel oxidation catalyst (DOC) and the final vehicle used both a DOC and diesel particulate filter (DPF). The experiments presented here were obtained from the vehicles at conditions representative of idle mode, and for one car in addition at a speed of 60 km/h. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was used to measure the organic aerosol (OA) concentration and to obtain information on the chemical composition. For the conditions explored in this paper, primary aerosols from vehicles without a particulate filter consisted mainly of black carbon (BC) with a low fraction of organic matter (OM, OM/BC<0.5), while the subsequent aging by photooxidation resulted in a consistent production of SOA only for the vehicles without a DOC and with a deactivated DOC. After 5 h of aging ~80% of the total organic aerosol was on average secondary and the estimated "emission factor" for SOA was 0.23–0.56 g/kg fuel burned. In presence of both a DOC and a DPF, primary particles with a mobility diameter above 5 nm were 300±19 cm−3, and only 0.01 g SOA per kg fuel burned was produced within 5 h after lights on. The mass spectra indicate that POA was mostly a non-oxidized OA with an oxygen to carbon atomic ratio (O/C) ranging from 0.097 to 0.190. Five hours of oxidation led to a more oxidized OA with an O/C range of 0.208 to 0.369.

scholarly journals Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber

2011 ◽  
Vol 11 (3) ◽  
pp. 7423-7467 ◽  
Author(s):  
T. Tritscher ◽  
J. Dommen ◽  
P. F. DeCarlo ◽  
P. B. Barmet ◽  
A. P. Praplan ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Organic Aerosol ◽  
Heterogeneous Reactions ◽  
Physical Parameters ◽  
Oh Radicals ◽  
Smog Chamber ◽  
Chemical Aging ◽  
Aerosol Mass ◽  
Gas Phase Oxidation ◽  
Substantial Change

Abstract. The evolution of secondary organic aerosols (SOA) during (photo-)chemical aging processes was investigated in a smog chamber. SOA from 10–40 ppb α-pinene was formed during ozonolysis followed by aging with OH radicals. The particles' volatility and hygroscopicity (expressed as volume fraction remaining (VFR) and hygroscopicity parameter κ) were measured with a volatility and hygroscopicity tandem differential mobility analyzer (V/H-TDMA). These measurements were used as sensitive physical parameters to reveal the possible mechanisms responsible for the chemical changes in the SOA composition during aging: A change of VFR and/or κ during processing of atmospheric aerosol may occur either by addition of SOA mass (by condensation) or by an exchange of molecules in the SOA by other molecules with different properties. The former process increases the SOA mass by definition, while the latter keeps the SOA mass roughly constant and may occur either by heterogeneous reactions on the surface of the SOA particles, by homogeneous reactions like oligomerization or by an evaporation – gas-phase oxidation – recondensation cycle. Thus, when there is a substantial change in the aerosol mass with time, the condensation mechanism may be assumed to be dominant, while, when the mass stays roughly constant the exchange mechanism is likely to be dominant, a process termed ripening here. Depending on the phase of the experiment, an O3 mediated condensation, O3 mediated ripening, OH mediated condensation, and OH mediated ripening could be distinguished. During the O3 mediated condensation the particles volatility decreased (increasing VFR) while the hygroscopicity increased. Thereafter, in the course of O3 mediated ripening volatility continued to decrease, but hygroscopicity stayed roughly constant. After exposing the SOA to OH radicals an OH mediated condensation started with a significant increase of SOA mass. Concurrently, hygroscopicity and volatility increased. This phase was then followed by an OH mediated ripening with a decrease of volatility.

Experimental Study of the Photochemical Reaction in the Smog Chamber Using a Chernin Multipass Cell

2013 ◽  
Vol 33 (8) ◽  
pp. 0830001
Author(s):  
程跃 Cheng Yue ◽  
赵卫雄 Zhao Weixiong ◽  
胡长进 Hu Changjin ◽  
顾学军 Gu Xuejun ◽  
裴世鑫 Pei Shixin ◽  
...  
Keyword(s):  
Experimental Study ◽  
Photochemical Reaction ◽  
Multipass Cell ◽  
Smog Chamber

scholarly journals Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber

2011 ◽  
Vol 11 (22) ◽  
pp. 11477-11496 ◽  
Author(s):  
T. Tritscher ◽  
J. Dommen ◽  
P. F. DeCarlo ◽  
M. Gysel ◽  
P. B. Barmet ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Volume Fraction ◽  
Chemical Characterization ◽  
Mass Gain ◽  
Heterogeneous Reactions ◽  
Oh Radicals ◽  
Smog Chamber ◽  
Chemical Aging ◽  
Aerosol Mass ◽  
Significant Mass

Abstract. The evolution of secondary organic aerosols (SOA) during (photo-)chemical aging processes was investigated in a smog chamber. Fresh SOA from ozonolysis of 10 to 40 ppb α-pinene was formed followed by aging with OH radicals. The particles' volatility and hygroscopicity (expressed as volume fraction remaining (VFR) and hygroscopicity parameter κ) were measured in parallel with a volatility and hygroscopicity tandem differential mobility analyzer (V/H-TDMA). An aerosol mass spectrometer (AMS) was used for the chemical characterization of the aerosol. These measurements were used as sensitive parameters to reveal the mechanisms possibly responsible for the changes in the SOA composition during aging. A change of VFR and/or κ during processing of atmospheric aerosols may occur either by addition of SOA mass (by condensation) or by a change of SOA composition leading to different aerosol properties. The latter may occur either by heterogeneous reactions on the surface of the SOA particles, by condensed phase reactions like oligomerization or by an evaporation – gas-phase oxidation – recondensation cycle. The condensation mechanism showed to be dominant when there is a substantial change in the aerosol mass by addition of new molecules to the aerosol phase with time. Experiments could be divided into four periods based on the temporal evolution (qualitative changes) of VFR, κ and organic mass: O3 induced condensation, ripening, and OH induced chemical aging first with substantial mass gain and then without significant mass gain. During the O3 induced condensation the particles' volatility decreased (increasing VFR) while the hygroscopicity increased. Thereafter, in the course of ripening volatility continued to decrease, but hygroscopicity stayed roughly constant. After exposing the SOA to OH radicals an OH induced chemical aging with substantial mass gain started resulting in the production of at least 50 % more SOA mass. This new SOA mass was highly volatile and oxidized. This period was then followed by further OH induced chemical aging without significant mass gain leading to a decrease of volatility while hygroscopicity and SOA mass stayed roughly constant.

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