Particle wall losses in smog chambers

2016 ◽  
Author(s):  
Anonymous
Keyword(s):  
Wall Losses ◽  
Smog Chambers

scholarly journals Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

2015 ◽  
Vol 15 (11) ◽  
pp. 15243-15288
Author(s):  
Q. Bian ◽  
A. A. May ◽  
S. M. Kreidenweis ◽  
J. R. Pierce
Keyword(s):  
Mass Loss ◽  
Gas Phase ◽  
Basis Set ◽  
Wood Smoke ◽  
Smog Chamber ◽  
Organic Mass ◽  
Final Particle ◽  
Wall Losses ◽  
Wall Loss ◽  
Smog Chambers

Abstract. Smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA) formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke) may complicate the behavior of particle and vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimates of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III). We use the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled with the organic volatility basis set (VBS) and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one third of the initial particle-phase organic mass (36%) was lost during the experiments, and roughly half of this particle organic mass loss was from direct particle wall loss (56% of the loss) with the remainder from evaporation of the particles driven by vapor losses to the walls (44% of the loss). We perform a series of sensitivity tests to understand uncertainties in our simulations. Uncertainty in the initial wood-smoke volatility distribution contributes 23% uncertainty to the final particle organic mass remaining in the chamber (relative to base-assumptions simulation). We show that the total mass loss may depend on the effective saturation concentration of vapor with respect to the walls as these values currently vary widely in the literature. The details of smoke dilution during the filling of smog chambers may influence the mass loss to the walls, and a dilution of ~ 25:1 during the experiments increased particle organic mass loss by 64% compared to a simulation where we assume the particles and vapors are initially in equilibrium in the chamber. Finally, we discuss how our findings may influence interpretations of emission factors and SOA production in wood-smoke smog-chamber experiments.

Molecule and aerosol particle wall losses in SMOG chambers made of glass

1989 ◽  
Vol 20 (1) ◽  
pp. 113-122 ◽  
Author(s):  
R. Van Dingenen ◽  
F. Raes ◽  
H. Vanmarcke
Keyword(s):  
Aerosol Particle ◽  
Wall Losses ◽  
Smog Chambers

scholarly journals Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

2015 ◽  
Vol 15 (19) ◽  
pp. 11027-11045 ◽  
Author(s):  
Q. Bian ◽  
A. A. May ◽  
S. M. Kreidenweis ◽  
J. R. Pierce
Keyword(s):  
Mass Loss ◽  
Gas Phase ◽  
Basis Set ◽  
Wood Smoke ◽  
Smog Chamber ◽  
Organic Mass ◽  
Final Particle ◽  
Wall Losses ◽  
Wall Loss ◽  
Smog Chambers

Abstract. Smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA) formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke) may complicate the behavior of particle and vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimations of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III). We use the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled with the organic volatility basis set (VBS) and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one-third of the initial particle-phase organic mass (41 %) was lost during the experiments, and over half of this particle-organic mass loss was from direct particle wall loss (65 % of the loss) with the remainder from evaporation of the particles driven by vapor losses to the walls (35 % of the loss). We perform a series of sensitivity tests to understand uncertainties in our simulations. Uncertainty in the initial wood-smoke volatility distribution contributes 18 % uncertainty to the final particle-organic mass remaining in the chamber (relative to base-assumption simulation). We show that the total mass loss may depend on the effective saturation concentration of vapor with respect to the walls as these values currently vary widely in the literature. The details of smoke dilution during the filling of smog chambers may influence the mass loss to the walls, and a dilution of ~ 25:1 during the experiments increased particle-organic mass loss by 33 % compared to a simulation where we assume the particles and vapors are initially in equilibrium in the chamber. Finally, we discuss how our findings may influence interpretations of emission factors and SOA production in wood-smoke smog-chamber experiments.

Gas and aerosol wall losses in Teflon film smog chambers

1985 ◽  
Vol 19 (12) ◽  
pp. 1176-1182 ◽  
Author(s):  
Peter H. McMurry ◽  
Daniel. Grosjean
Keyword(s):  
Wall Losses ◽  
Smog Chambers ◽  
Teflon Film

scholarly journals Use of a heated graphite scrubber as a means of reducing interferences in UV-absorbance measurements of atmospheric ozone

2017 ◽  
Vol 10 (6) ◽  
pp. 2253-2269 ◽  
Author(s):  
Andrew A. Turnipseed ◽  
Peter C. Andersen ◽  
Craig J. Williford ◽  
Christine A. Ennis ◽  
John W. Birks
Keyword(s):  
Water Vapor ◽  
Solid Phase ◽  
Mercury Vapor ◽  
Packed Bed ◽  
The United States ◽  
Voc Adsorption ◽  
Clean Air ◽  
Smog Chambers ◽  
Equivalent Method ◽  
Ambient Measurements

Abstract. A new solid-phase scrubber for use in conventional ozone (O3) photometers was investigated as a means of reducing interferences from other UV-absorbing species and water vapor. It was found that when heated to 100–130 °C, a tubular graphite scrubber efficiently removed up to 500 ppb ozone and ozone monitors using the heated graphite scrubber were found to be less susceptible to interferences from water vapor, mercury vapor, and aromatic volatile organic compounds (VOCs) compared to conventional metal oxide scrubbers. Ambient measurements from a graphite scrubber-equipped photometer and a co-located Federal equivalent method (FEM) ozone analyzer showed excellent agreement over 38 days of measurements and indicated no loss in the scrubber's ability to remove ozone when operated at 130 °C. The use of a heated graphite scrubber was found to reduce the interference from mercury vapor to ≤ 3 % of that obtained using a packed-bed Hopcalite scrubber. For a series of substituted aromatic compounds (ranging in volatility and absorption cross section at 253.7 nm), the graphite scrubber was observed to consistently exhibit reduced levels of interference, typically by factors of 2.5 to 20 less than with Hopcalite. Conventional solid-phase scrubbers also exhibited complex VOC adsorption and desorption characteristics that were dependent upon the relative humidity (RH), volatility of the VOC, and the available surface area of the scrubber. This complex behavior involving humidity is avoided by use of a heated graphite scrubber. These results suggest that heated graphite scrubbers could be substituted in most ozone photometers as a means of reducing interferences from other UV-absorbing species found in the atmosphere. This could be particularly important in ozone monitoring for compliance with the United States (U.S.) Clean Air Act or for use in VOC-rich environments such as in smog chambers and monitoring indoor air quality.

Computer simulations of Hall thrusters without wall losses designed using two permanent magnetic rings

2016 ◽  
Vol 49 (46) ◽  
pp. 465001 ◽  
Author(s):  
Ding Yongjie ◽  
Peng Wuji ◽  
Wei Liqiu ◽  
Sun Guoshun ◽  
Li Hong ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Hall Thrusters ◽  
Wall Losses ◽  
Magnetic Rings

scholarly journals Technical Note: Effect of varying the <i>λ</i> = 185 and 254 nm photon flux ratio on radical generation in oxidation flow reactors

2020 ◽  
Vol 20 (21) ◽  
pp. 13417-13424
Author(s):  
Jake P. Rowe ◽  
Andrew T. Lambe ◽  
William H. Brune
Keyword(s):  
Residence Time ◽  
Low Cost ◽  
Flux Ratio ◽  
Technical Note ◽  
Photon Flux ◽  
Oh Radicals ◽  
Flow Reactors ◽  
Series Of Experiments ◽  
Radical Generation ◽  
Smog Chambers

Abstract. Oxidation flow reactors (OFRs) complement environmental smog chambers as a portable, low-cost technique for exposing atmospheric compounds to oxidants such as ozone (O3), nitrate (NO3) radicals, and hydroxyl (OH) radicals. OH is most commonly generated in OFRs via photolysis of externally added O3 at λ=254 nm (OFR254) or combined photolysis of O2 and H2O at λ=185 nm plus photolysis of O3 at λ=254 nm (OFR185) using low-pressure mercury (Hg) lamps. Whereas OFR254 radical generation is influenced by [O3], [H2O], and photon flux at λ=254 nm (I254), OFR185 radical generation is influenced by [O2], [H2O], I185, and I254. Because the ratio of photon fluxes, I185:I254, is OFR-specific, OFR185 performance varies between different systems even when constant [H2O] and I254 are maintained. Thus, calibrations and models developed for one OFR185 system may not be applicable to another. To investigate these issues, we conducted a series of experiments in which I185:I254 emitted by Hg lamps installed in an OFR was systematically varied by fusing multiple segments of lamp quartz together that either transmitted or blocked λ=185 nm radiation. Integrated OH exposure (OHexp) values achieved for each lamp type were obtained using the tracer decay method as a function of UV intensity, humidity, residence time, and external OH reactivity (OHRext). Following previous related studies, a photochemical box model was used to develop a generalized OHexp estimation equation as a function of [H2O], [O3], and OHRext that is applicable for I185:I254≈0.001 to 0.1.

scholarly journals Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition

2015 ◽  
Vol 8 (1) ◽  
pp. 309-352 ◽  
Author(s):  
E. A. Bruns ◽  
I. El Haddad ◽  
A. Keller ◽  
F. Klein ◽  
N. K. Kumar ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Aerosol ◽  
Emission Factors ◽  
Smog Chamber ◽  
Wood Combustion ◽  
Flow Reactors ◽  
Aerosol Mass ◽  
Combustion Emissions ◽  
Smog Chambers ◽  
Composition Of Products

Abstract. A variety of tools are used to simulate atmospheric aging, including smog chambers and flow reactors. Traditional, large-scale smog chambers age emissions over the course of hours to days, whereas flow reactors rapidly age emissions using high oxidant concentrations to reach higher degrees of oxygenation than typically attained in smog chamber experiments. The atmospheric relevance of the products generated under such rapid oxidation warrants further study. However, no previously published studies have compared the yields and chemical composition of products generated in flow reactors and smog chambers from the same starting mixture. The yields and composition of the organic aerosol formed from the photo-oxidation of α-pinene and of wood combustion emissions were determined using aerosol mass spectrometry in a smog chamber (SC) and two flow reactors: a potential aerosol mass reactor (PAM) and a micro-smog chamber (MSC). Reactants were sampled from the SC and aged in the MSC and PAM using a range of hydroxyl radical (OH) concentrations and then photo-chemically aged in the SC. The maximum yields/emission factors and the chemical composition of the products in both the α-pinene and wood combustion systems determined with the PAM and SC agreed reasonably well. High OH exposures have been shown previously to lower yields by breaking carbon-carbon bonds and forming higher volatility species, which reside largely in the gas phase, however, fragmentation in the PAM was not observed. The yields determined using the PAM for the α-pinene system were slightly lower than in the SC, possibly from increased wall losses of gas-phase species due to the higher surface area to volume ratios in the PAM, even when offset with better isolation of the sampled flow from the walls. The α-pinene SOA results for the MSC were not directly comparable, as particles were smaller than the optimal AMS transmission range. For the wood combustion system, emission factors measured by the MSC were typically lower than those from the SC, possibly due to nucleation mode particles not observed by the AMS or the condensational loss of gases to the walls inside or after the MSC. The chemical composition of products in the flow reactors and SC were in reasonable agreement in both systems. The emission factors determined using the flow reactors increased relative to the SC when the wood combustion emissions contained higher fractions of aromatic compounds, suggesting that the performance of the flow reactors may be dependent on the chemical composition of the reactants.

scholarly journals Evaluating the impact of new observational constraints on P-S/IVOC emissions, multi-generation oxidation, and chamber wall losses on SOA modeling for Los Angeles, CA

2016 ◽  
Author(s):  
Prettiny K. Ma ◽  
Yunliang Zhao ◽  
Allen L. Robinson ◽  
David R. Worton ◽  
Allen H. Goldstein ◽  
...  
Keyword(s):  
Los Angeles ◽  
Flow Reactor ◽  
Particle Phase ◽  
Fossil Carbon ◽  
Voc Oxidation ◽  
Wall Losses ◽  
The Difference ◽  
Aging Mechanisms ◽  
The Impact ◽  
Model Measurement

Abstract. Secondary Organic Aerosols (SOA) are important contributors to fine PM mass in polluted regions, and their modeling remains poorly constrained. A box model is developed that uses recently published literature parameterizations and data sets to better constrain and evaluate the formation pathways and precursors of urban SOA during the CalNex 2010 campaign in Los Angeles. When using the measurements of IVOCs reported in Zhao et al. (2014) and of SVOCs reported in Worton et al. (2014) the model is biased high at longer photochemical ages whereas at shorter photochemical ages it is biased low, if the yields for VOC oxidation are not updated. The parameterizations using an updated version of the yields, which takes into account the effect of gas phase wall-losses in environmental chambers, show model/measurement agreement at longer photochemical ages, even though some low bias at short photochemical ages still remains. Furthermore, the fossil/non-fossil carbon split of urban SOA simulated by the model is consistent with measurements at the Pasadena ground site. Multi-generation oxidation mechanisms are often employed in SOA models to increase the SOA yields derived from environmental chamber experiments in order to obtain better model/measurement agreement. However, there are many uncertainties associated with these "aging" mechanisms. Thus, SOA formation in the model is compared against data from an oxidation flow reactor (OFR) in order to constrain SOA formation at longer photochemical ages than observed in urban air. The model predicts similar SOA mass when the "aging" mechanisms or the updated version of the yields for VOC oxidation are implemented. The latter case though has SOA formation rates that are more consistent with observations from the OFR. All the model cases evaluated in this work have a large majority of the urban SOA (70–86 %) at Pasadena coming from the oxidation of P-SVOCs and P-IVOCs. The importance of these two types of precursors is further supported by analyzing the percentage of SOA formed at long photochemical ages (1.5 days) as a function of the precursor rate constant. The P-SVOCs and P-IVOCs have rate constants that are similar to highly reactive VOCs that have been previously found to strongly correlate with SOA formation potential measured by the OFR. Finally, the volatility distribution of the total organic mass (gas and particle phase) in the model is compared against measurements. The total SVOC mass simulated is similar to the measurements, but there are important differences in the measured and modeled volatility distributions. A likely reason for the difference is the lack of particle-phase reactions in the model that can oligomerize and/or continue to oxidize organic compounds even after they partition to the particle phase.

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