Temperature dependence of OH uptake by carbonaceous surfaces of atmospheric importance

Liu, Yong; Ivanov, A. V.; Zelenov, V. V.; Molina, Mario J.

doi:10.1134/s199079311202008x

Cited by 8 publications

(10 citation statements)

References 25 publications

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“…Although we cannot rule out some chemical changes during TD heating, this conclusion is dictated by the data at the lowest TD temperatures, when such chemistry is less likely. Lopez-Hilfiker et al (2016) have shown that oligomer decomposition for IEPOX-SOA upon heating at ∼ 90 • was important during the SE US study, but that process will only make the measured volatility of IEPOX-SOA in TD higher than it should be. This reinforces our conclusion about the low volatility of ambient IEPOX-SOA, consistent with the independent results of Lopez-Hilfiker et al 2016.…”

Section: Low Volatility Of Iepox-soamentioning

confidence: 97%

“…The volatility distributions of IEPOX-SOA and OA were estimated following the method of Faulhaber et al (2009), based on calibration of the relationship between TD temperature and organic species saturation concentration at 298 K (C * ). Similar methods have been developed for other thermal desorption instruments (e.g., Chattopadhyay and Ziemann, 2005;Lopez-Hilfiker et al, 2016). The volatility distribution of IEPOX-SOA ( Fig.…”

Section: Low Volatility Of Iepox-soamentioning

confidence: 98%

“…To describe the aging process, OA reaction rate coefficients with OH radicals (k OH ), or alternatively, uptake coefficients of OH (γ OH ), defined as the fraction of OH collisions with a compound that result in reaction, have been reported for numerous laboratory studies. Values of effective γ OH (≤ 0.01 to ≥ 1) also can vary significantly under different reaction conditions, such as different OA species (George and Abbatt, 2010), temperature and humidity (Park et al, 2008;Liu et al, 2012;Slade and Knopf, 2014), OH concentrations (Slade and Knopf, 2013;Arangio et al, 2015), and particle phase state or coatings (McNeill et al, 2008;Arangio et al, 2015). Most of the studies that have reported k OH and γ OH are based on laboratory experiments, with few experimental determinations of k OH based on field measurements under ambient conditions (Slowik et al, 2012;Ortega et al, 2016), while no γ OH has been reported based on field studies to our knowledge.…”

Section: Introductionmentioning

confidence: 99%

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Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA)

et al. 2016

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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 southeastern United States (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 does not 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 IEPOX-SOA to be efficiently formed 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 observations of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.

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Section: Low Volatility Of Iepox-soamentioning

confidence: 97%

Section: Low Volatility Of Iepox-soamentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA)

et al. 2016

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“…day of aging. During IOP2, it was observed that isoprene would peak during the day around 15:00-16:00 local time and MT would peak later, around 18:00 local time (Liu et al, 2016;Martin et al, 2016). Isoprene was primarily depleted through oxidation reactions by nighttime, but MT had a background level that remained approximately constant between midnight and noon (local times) when the concentrations would begin to rise again (Fig.…”

Section: Goamazon2014/5 Casesmentioning

confidence: 98%

Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling

et al. 2018

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Abstract. Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size-distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09 and 0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp > 60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24 %–95 % of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

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“…Heterogeneous reactions contribute to aerosol aging and influence aerosol lifetime (George and Abbatt, 2010;George et al, 2015;Kroll et al, 2015). Many laboratory studies have reported uptake coefficients of OH, γ OH , defined as the fraction of OH collisions with a particle-phase compound that result in a reaction, with values of effective γ OH ranging from ≤ 0.01 to > 1, depending upon the reaction conditions (e.g., McNeill et al, 2008;15 Park et al, 2008;George and Abbatt, 2010;Liu et al, 2012;Slade and Knopf, 2013;Arangio et al, 2015;.…”

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confidence: 99%

Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modelling

Hodshire¹,

Palm²,

Alexander³

et al. 2018

Preprint

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Abstract. Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes 35 in the OFR. Specifically, we use OFR exposures between 0.09-0.9 equivalent days of OH aging from the 2011 BEACHONRoMBAS and the GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60 nm in diameter.We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (D p >60 nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the 5 larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H 2 SO 4 -organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24-95% of the 10 observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes.

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Temperature dependence of OH uptake by carbonaceous surfaces of atmospheric importance

Cited by 8 publications

References 25 publications

Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA)

Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA)

Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling

Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modelling

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