scholarly journals Temperature dependence of secondary organic aerosol yield from the ozonolysis of β-pinene

2006 ◽  
Vol 6 (5) ◽  
pp. 10275-10297 ◽  
Author(s):  
C. Stenby ◽  
U. Pöschl ◽  
P. von Hessberg ◽  
M. Bilde ◽  
O. J. Nielsen ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Measurement Data ◽  
Organic Aerosol ◽  
Reaction Products ◽  
Aerosol Formation ◽  
Product Model ◽  
High Particle

Abstract. The temperature dependence of secondary organic aerosol (SOA) formation from ozonolysis of β-pinene was studied in a flow reactor at 263–303 K and 1007 hPa. The observed SOA yields were of similar magnitude as predicted by a two-product model based on detailed gas phase chemistry (Jenkin, 2004), reaching maximum values of 0.22–0.39 at high particle mass concentrations. However, the measurement data exhibited significant deviations (up to 50%) from the predicted linear dependence on inverse temperature. When fitting the measurement data with a two-product model, we found that both the partitioning coefficients (Kom,i) and the stoichiometric yields (αi) of the low-volatile and semi-volatile species vary with temperature. The results indicate that not only the reaction product vapour pressures but also the relative contributions of different gas-phase or multiphase reaction channels are dependent on temperature. We suggest that the modelling of secondary organic aerosol formation in the atmosphere needs to take into account the effects of temperature on the pathways and kinetics of the involved chemical reactions as well as on the gas-particle partitioning of the reaction products.

scholarly journals Rate constant and secondary organic aerosol formation from the gas-phase reaction of eugenol with hydroxyl radicals

2019 ◽  
Vol 19 (3) ◽  
pp. 2001-2013 ◽  
Author(s):  
Changgeng Liu ◽  
Yongchun Liu ◽  
Tianzeng Chen ◽  
Jun Liu ◽  
Hong He
Keyword(s):  
Rate Constant ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Relative Rate ◽  
Organic Aerosol ◽  
Organic Nitrates ◽  
Phase Reaction ◽  
Aerosol Formation ◽  
Product Model ◽  
Formation Potential

Abstract. Methoxyphenols are an important organic component of wood-burning emissions and considered to be potential precursors of secondary organic aerosol (SOA). In this work, the rate constant and SOA formation potential for the OH-initiated reaction of 4-allyl-2-methoxyphenol (eugenol) were investigated for the first time in an oxidation flow reactor (OFR). The rate constant was 8.01±0.40×10-11 cm3 molecule−1 s−1, determined by the relative rate method. The SOA yield first increased and then decreased as a function of OH exposure and was also dependent on eugenol concentration. The maximum SOA yields (0.11–0.31) obtained at different eugenol concentrations could be expressed well by a one-product model. The carbon oxidation state (OSC) increased linearly and significantly as OH exposure rose, indicating that a high oxidation degree was achieved for SOA. In addition, the presence of SO2 (0–198 ppbv) and NO2 (0–109 ppbv) was conducive to increasing SOA yield, for which the maximum enhancement values were 38.6 % and 19.2 %, respectively. The N∕C ratio (0.032–0.043) indicated that NO2 participated in the OH-initiated reaction, subsequently forming organic nitrates. The results could be helpful for further understanding the SOA formation potential from the atmospheric oxidation of methoxyphenols and the atmospheric aging process of smoke plumes from biomass burning emissions.

scholarly journals The effect of temperature and water on secondary organic aerosol formation from ozonolysis of limonene, Δ<sup>3</sup>-carene and α-pinene

2008 ◽  
Vol 8 (21) ◽  
pp. 6541-6549 ◽  
Author(s):  
Å. M. Jonsson ◽  
M. Hallquist ◽  
E. Ljungström
Keyword(s):  
Temperature Dependence ◽  
Low Temperatures ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Reaction Rates ◽  
Chemical Mechanism ◽  
Positive Temperature ◽  
Aerosol Formation ◽  
Secondary Chemistry

Abstract. The effect of reaction temperature and how water vapour influences the formation of secondary organic aerosol (SOA) in ozonolysis of limonene, Δ3-carene and α-pinene, both regarding number and mass of particles, has been investigated by using a laminar flow reactor (G-FROST). Experiments with cyclohexane and 2-butanol as OH scavengers were compared to experiments without any scavenger. The reactions were conducted in the temperature range between 298 and 243 K, and at relative humidities between <10 and 80%. Results showed that there is still a scavenger effect on number and mass concentrations at low temperatures between experiments with and without an addition of an OH scavenger. This shows that the OH chemistry is influencing the SOA formation also at these temperatures. The overall temperature dependence on SOA formation is not as strong as expected from partitioning theory. In some cases there is even a positive temperature dependence that must be related to changes in the chemical mechanism and/or reduced rates of secondary chemistry at low temperatures. The precursor's α-pinene and Δ3-carene exhibit a similar temperature dependence regarding both number and mass of particles formed, whereas limonene shows a different dependence. The water effect at low temperature could be explained by physical uptake and cluster stabilisation. At higher temperatures, only a physical explanation is not sufficient and the observations are in line with water changing the chemical mechanism or reaction rates. The data presented adds to the understanding of SOA contribution to new particle formation and atmospheric degradation mechanisms.

scholarly journals Temperature and humidity dependence of secondary organic aerosol yield from the ozonolysis of β-pinene

2007 ◽  
Vol 7 (1) ◽  
pp. 2091-2132 ◽  
Author(s):  
C. Stenby ◽  
U. Pöschl ◽  
P. von Hessberg ◽  
M. Bilde ◽  
O. J. Nielsen ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Measurement Data ◽  
Organic Aerosol ◽  
Inverse Temperature ◽  
Product Model ◽  
Temperature And Humidity ◽  
Dry Conditions ◽  
Humidity Dependence

Abstract. The temperature dependence of secondary organic aerosol (SOA) formation from ozonolysis of β-pinene was studied in a flow reactor at 263 K–303 K and 1007 hPa under dry and humid conditions (0% and 26%–68% relative humidity, respectively). The observed SOA yields were of similar magnitude as predicted by a two-product model based on detailed gas phase chemistry (Jenkin, 2004), reaching maximum values of 0.18–0.39 at high particle mass concentrations (Mo). Under dry conditions, however, the measurement data exhibited significant oscillatory deviations from the predicted linear increase with inverse temperature (up to 50% at high Mo). Under humid conditions the SOA yield exhibited a linear decrease with inverse temperature, which is opposite to modelled temperature dependence and implies that the model substantially overestimates the yield at low temperatures and underestimates it at high temperatures (deviations up to 80% at high Mo). For the atmospherically relevant concentration level of Mo=10 μg m−3 and temperature range 263 K–293 K, the results from humid experiments in this study indicate that the SOA yield of β-pinene ozonolysis may be well represented by an average value of 0.15 with an uncertainty estimate of ±0.05. When fitting the measurement data with a two-product model, both the partitioning coefficients (Kom,i) and the stoichiometric yields (αi) of the low-volatile and semi-volatile model species were found to vary with temperature. The results indicate that not only the reaction product vapour pressures but also the relative contributions of different gas-phase or multiphase reaction channels are strongly dependent on temperature and the presence of water vapour. In fact, the oscillatory positive temperature dependence observed under dry conditions and the negative temperature dependence observed under humid conditions indicate that the SOA yield is governed much more by the temperature and humidity dependence of the involved chemical reactions than by vapour pressure temperature dependencies. We suggest that the elucidation and modelling of SOA formation need to take into account the effects of temperature and humidity on the pathways and kinetics of the involved chemical reactions as well as on the gas-particle partitioning of the reaction products.

scholarly journals Modeling organic aerosols in a megacity: comparison of simple and complex representations of the volatility basis set approach

2010 ◽  
Vol 10 (12) ◽  
pp. 30205-30277 ◽  
Author(s):  
M. Shrivastava ◽  
J. Fast ◽  
R. Easter ◽  
W. I. Gustafson ◽  
R. A. Zaveri ◽  
...  
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Computational Cost ◽  
Organic Aerosols ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Basis Set ◽  
Aerosol Formation ◽  
Secondary Organic Aerosol Formation ◽  
The City

Abstract. The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) is modified to include a volatility basis set (VBS) treatment of secondary organic aerosol formation. The VBS approach, coupled with SAPRC-99 gas-phase chemistry mechanism, is used to model gas-particle partitioning and multiple generations of gas-phase oxidation of organic vapors. In addition to the detailed 9-species VBS, a simplified mechanism using 2 volatility species (2-species VBS) is developed and tested for similarity to the 9-species VBS in terms of both mass and oxygen-to-carbon ratios of organic aerosols in the atmosphere. WRF-Chem results are evaluated against field measurements of organic aerosols collected during the MILAGRO 2006 campaign in the vicinity of Mexico City. The simplified 2-species mechanism reduces the computational cost by a factor of 2 as compared to 9-species VBS. Both ground site and aircraft measurements suggest that the 9-species and 2-species VBS predictions of total organic aerosol mass as well as individual organic aerosol components including primary, secondary, and biomass burning are comparable in magnitude. In addition, oxygen-to-carbon ratio predictions from both approaches agree within 25%, providing evidence that the 2-species VBS is well suited to represent the complex evolution of organic aerosols. Model sensitivity to amount of anthropogenic semi-volatile and intermediate volatility (S/IVOC) precursor emissions is also examined by doubling the default emissions. Both the emission cases significantly under-predict primary organic aerosols in the city center and along aircraft flight transects. Secondary organic aerosols are predicted reasonably well along flight tracks surrounding the city, but are consistently over-predicted downwind of the city. Also, oxygen-to-carbon ratio predictions are significantly improved compared to prior studies by adding 15% oxygen mass per generation of oxidation; however, all modeling cases still under-predict these ratios downwind as compared to measurements, suggesting a need to further improve chemistry parameterizations of secondary organic aerosol formation.

scholarly journals In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

2015 ◽  
Vol 15 (21) ◽  
pp. 30409-30471 ◽  
Author(s):  
B. B. Palm ◽  
P. Campuzano-Jost ◽  
A. M. Ortega ◽  
D. A. Day ◽  
L. Kaser ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Pine Forest ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Photochemical Aging

Abstract. Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative time scales of condensation of low volatility organic compounds (LVOCs) onto particles, condensational loss to the walls, and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 μg m-3 when LVOC fate corrected), with maximum formation observed at 0.4–1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene + p-cymene concentrations, including a substantial increase just after sunrise at 07:00 LT. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than could be explained by the VOCs measured in ambient air. Several recently-developed instruments quantified ambient semi- and intermediate-volatility organic compounds (S/IVOCs) that were not detected by a PTR-TOF-MS. An SOA yield of 24–80 % from those compounds can explain the observed SOA, suggesting that these typically unmeasured S/IVOCs play a substantial role in ambient SOA formation. Our results allow ruling out condensation sticking coefficients much lower than 1. Our measurements help clarify the magnitude of SOA formation in forested environments, and demonstrate methods for interpretation of ambient OFR measurements.

scholarly journals Volatility and lifetime against OH heterogeneous reaction of ambient Isoprene Epoxydiols-Derived Secondary Organic Aerosol (IEPOX-SOA)

2016 ◽  
Author(s):  
Weiwei Hu ◽  
Brett B. Palm ◽  
Douglas A. Day ◽  
Pedro Campuzano-Jost ◽  
Jordan E. Krechmer ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Heterogeneous Reaction ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Amazon Forest ◽  
Reaction Products ◽  
Ambient Conditions ◽  
Forested Areas ◽  
Humidity Dependence

Abstract. Isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to organic aerosol (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting for example for 16–36 % of the submicron OA in the SE US summer. Particle evaporation measurements from a thermodenuder show that the volatility of ambient IEPOX-SOA is lower than that of bulk OA and also much lower than that of known monomer IEPOX-SOA tracer species, indicating that IEPOX-SOA likely exists mostly as oligomers in the aerosol phase. The OH aging process of ambient IEPOX-SOA was investigated with an oxidation flow reactor (OFR). New IEPOX-SOA formation in the reactor was negligible, as the OFR cannot accelerate processes such as aerosol uptake and reactions that do not scale with OH. Simulation results indicate that adding ~ 100 µg m−3 of pure H2SO4 to the ambient air allows to efficiently form IEPOX-SOA in the reactor. The heterogeneous reaction rate coefficient of ambient IEPOX-SOA with OH radical (kOH) was estimated as 4.0 ± 2.0 × 10−13 cm3 molec−1 s−1, which is equivalent to more than a 2-week lifetime. A similar kOH was found for measurements of OH oxidation of ambient Amazon forest air in an OFR. At higher OH exposures in the reactor (> 1 × 1012 molec. cm−3 s), the mass loss of IEPOX-SOA due to heterogeneous reaction was mainly due to revolatilization of fragmented reaction products. We report for the first time OH reactive uptake coefficients (γOH = 0.59 ± 0.33 in SE US and γOH = 0.68 ± 0.38 in Amazon) for SOA under ambient conditions. A relative humidity dependence of kOH and γOH was observed, consistent with surface area-limited OH uptake. No decrease of kOH was observed as OH concentrations increased. These observation of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.

scholarly journals Application of the Statistical Oxidation Model (SOM) to Secondary Organic Aerosol formation from photooxidation of C<sub>12</sub> alkanes

2013 ◽  
Vol 13 (3) ◽  
pp. 1591-1606 ◽  
Author(s):  
C. D. Cappa ◽  
X. Zhang ◽  
C. L. Loza ◽  
J. S. Craven ◽  
L. D. Yee ◽  
...  
Keyword(s):  
Formation Process ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atomic Ratio ◽  
Model Parameters ◽  
Reaction Products ◽  
Aerosol Formation ◽  
Volatile Organic ◽  
Oxidation Model ◽  
Mechanism Of Oxidation

Abstract. Laboratory chamber experiments are the main source of data on the mechanism of oxidation and the secondary organic aerosol (SOA) forming potential of volatile organic compounds. Traditional methods of representing the SOA formation potential of an organic do not fully capture the dynamic, multi-generational nature of the SOA formation process. We apply the Statistical Oxidation Model (SOM) of Cappa and Wilson (2012) to model the formation of SOA from the formation of the four C12 alkanes, dodecane, 2-methyl undecane, cyclododecane and hexylcyclohexane, under both high- and low-NOx conditions, based upon data from the Caltech chambers. In the SOM, the evolution of reaction products is defined by the number of carbon (NC) and oxygen (NO) atoms, and the model parameters are (1) the number of oxygen atoms added per reaction, (2) the decrease in volatility upon addition of an oxygen atom and (3) the probability that a given reaction leads to fragmentation of the molecules. Optimal fitting of the model to chamber data is carried out using the measured SOA mass concentration and the aerosol O:C atomic ratio. The use of the kinetic, multi-generational SOM is shown to provide insights into the SOA formation process and to offer promise for application to the extensive library of existing SOA chamber experiments that is available.

scholarly journals Enhancement of Secondary Organic Aerosol Formation and its Oxidation State by SO<sub>2</sub> during Photooxidation of 2-Methoxyphenol

2018 ◽  
Author(s):  
Changgeng Liu ◽  
Tianzeng Chen ◽  
Yongchun Liu ◽  
Jun Liu ◽  
Hong He ◽  
...  
Keyword(s):  
Oxidation State ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Wood Smoke ◽  
Organic Nitrates ◽  
Carbon Oxidation ◽  
Formation Processes ◽  
Aerosol Formation ◽  
Product Model ◽  
Seed Particles

Abstract. 2-Methoxyphenol (guaiacol) is derived from the lignin pyrolysis and taken as a potential tracer for wood smoke emissions. In this work, the effect of SO2 at atmospheric levels (0–56 ppb) on secondary organic aerosol (SOA) formation and its oxidation state during guaiacol photooxidation was investigated in the presence of various inorganic seed particles (NaCl and (NH4)2SO4). Without SO2 and seed particles, SOA yields (9.46–26.37 %) obtained at different guaiacol concentration (138.83–2197.36 μg m−3) could be well expressed by a one-product model. The presence of SO2 resulted in enhancing SOA yield by 14.05–23.66 %. With (NH4)2SO4 and NaCl seed particles, SOA yield was enhanced by 23.06 % and 29.57 %, respectively, which further increased significantly to 29.78–53.47 % in the presence of SO2, suggesting that SO2 and seed particles have a synergetic contribution to SOA formation. It should be noted that SO2 was found to be in favor of increasing the carbon oxidation state (OSC) of SOA, indicating that the functionalization reaction should be more dominant than oligomerization reaction. In addition, the average N/C ratio of SOA was 0.037, which revealed that NOx participated in the photooxidation process, consequently leading to the formation of organic nitrates. The experimental results demonstrate the importance of SO2 on the formation processes of SOA and organosulfates, and also are helpful to further understand SOA formation from the atmospheric photooxidation of guaiacol and its subsequent impacts on air quality and climate.

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