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Sample records for aerosol soa production

  1. Rethinking the global secondary organic aerosol (SOA) budget: stronger production, faster removal, shorter lifetime

    NASA Astrophysics Data System (ADS)

    Hodzic, Alma; Kasibhatla, Prasad S.; Jo, Duseong S.; Cappa, Christopher D.; Jimenez, Jose L.; Madronich, Sasha; Park, Rokjin J.

    2016-06-01

    Recent laboratory studies suggest that secondary organic aerosol (SOA) formation rates are higher than assumed in current models. There is also evidence that SOA removal by dry and wet deposition occurs more efficiently than some current models suggest and that photolysis and heterogeneous oxidation may be important (but currently ignored) SOA sinks. Here, we have updated the global GEOS-Chem model to include this new information on formation (i.e., wall-corrected yields and emissions of semi-volatile and intermediate volatility organic compounds) and on removal processes (photolysis and heterogeneous oxidation). We compare simulated SOA from various model configurations against ground, aircraft and satellite measurements to assess the extent to which these improved representations of SOA formation and removal processes are consistent with observed characteristics of the SOA distribution. The updated model presents a more dynamic picture of the life cycle of atmospheric SOA, with production rates 3.9 times higher and sinks a factor of 3.6 more efficient than in the base model. In particular, the updated model predicts larger SOA concentrations in the boundary layer and lower concentrations in the upper troposphere, leading to better agreement with surface and aircraft measurements of organic aerosol compared to the base model. Our analysis thus suggests that the long-standing discrepancy in model predictions of the vertical SOA distribution can now be resolved, at least in part, by a stronger source and stronger sinks leading to a shorter lifetime. The predicted global SOA burden in the updated model is 0.88 Tg and the corresponding direct radiative effect at top of the atmosphere is -0.33 W m-2, which is comparable to recent model estimates constrained by observations. The updated model predicts a population-weighed global mean surface SOA concentration that is a factor of 2 higher than in the base model, suggesting the need for a reanalysis of the contribution of

  2. Aqueous aerosol SOA formation: impact on aerosol physical properties.

    PubMed

    Woo, Joseph L; Kim, Derek D; Schwier, Allison N; Li, Ruizhi; McNeill, V Faye

    2013-01-01

    Organic chemistry in aerosol water has recently been recognized as a potentially important source of secondary organic aerosol (SOA) material. This SOA material may be surface-active, therefore potentially affecting aerosol heterogeneous activity, ice nucleation, and CCN activity. Aqueous aerosol chemistry has also been shown to be a potential source of light-absorbing products ("brown carbon"). We present results on the formation of secondary organic aerosol material in aerosol water and the associated changes in aerosol physical properties from GAMMA (Gas-Aerosol Model for Mechanism Analysis), a photochemical box model with coupled gas and detailed aqueous aerosol chemistry. The detailed aerosol composition output from GAMMA was coupled with two recently developed modules for predicting a) aerosol surface tension and b) the UV-Vis absorption spectrum of the aerosol, based on our previous laboratory observations. The simulation results suggest that the formation of oligomers and organic acids in bulk aerosol water is unlikely to perturb aerosol surface tension significantly. Isoprene-derived organosulfates are formed in high concentrations in acidic aerosols under low-NO(x) conditions, but more experimental data are needed before the potential impact of these species on aerosol surface tension may be evaluated. Adsorption of surfactants from the gas phase may further suppress aerosol surface tension. Light absorption by aqueous aerosol SOA material is driven by dark glyoxal chemistry and is highest under high-NO(x) conditions, at high relative humidity, in the early morning hours. The wavelength dependence of the predicted absorption spectra is comparable to field observations and the predicted mass absorption efficiencies suggest that aqueous aerosol chemistry can be a significant source of aerosol brown carbon under urban conditions.

  3. Chemical characterization of the main secondary organic aerosol (SOA) products formed through aqueous-phase photonitration of guaiacol

    NASA Astrophysics Data System (ADS)

    Kitanovski, Z.; Čusak, A.; Grgić, I.; Claeys, M.

    2014-04-01

    Guaiacol (2-methoxyphenol) and its derivatives can be emitted into the atmosphere by thermal degradation (i.e. burning) of wood lignins. Due to its volatility, guaiacol is predominantly distributed in the atmospheric gaseous phase. Recent studies have shown the importance of aqueous-phase reactions in addition to the dominant gas-phase and heterogeneous reactions of guaiacol, in the formation of secondary organic aerosol (SOA) in the atmosphere. The main objectives of the present study were to chemically characterize the low-volatility SOA products of the aqueous-phase photonitration of guaiacol and examine their possible presence in urban atmospheric aerosols. The aqueous-phase reactions were carried out under simulated sunlight and in the presence of H2O2 and nitrite. The formed guaiacol reaction products were concentrated by using solid-phase extraction (SPE) and then purified by means of semi-preparative high-performance liquid chromatography (HPLC). The fractionated individual compounds were isolated as pure solids and further analyzed with liquid-state 1H, 13C and 2D nuclear magnetic resonance (NMR) spectroscopy and direct infusion negative ion electrospray ionization tandem mass spectrometry ((-)ESI-MS/MS). The NMR and product ion (MS2) spectra were used for unambiguous product structure elucidation. The main products of guaiacol photonitration are 4-nitroguaiacol (4NG), 6-nitroguaiacol (6NG), and 4,6-dinitroguaiacol (4,6DNG). Using the isolated compounds as standards, 4NG and 4,6DNG were unambiguously identified in winter PM10 aerosols from the city of Ljubljana (Slovenia) by means of HPLC/(-)ESI-MS/MS. Owing to the strong absorption of UV and visible light, 4,6DNG could be an important constituent of atmospheric "brown" carbon, especially in regions affected by biomass burning.

  4. Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties

    NASA Astrophysics Data System (ADS)

    Emanuelsson, E. U.; Hallquist, M.; Kristensen, K.; Glasius, M.; Bohn, B.; Fuchs, H.; Kammer, B.; Kiendler-Scharr, A.; Nehr, S.; Rubach, F.; Tillmann, R.; Wahner, A.; Wu, H.-C.; Mentel, Th. F.

    2012-08-01

    Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. Several experiments with exclusively anthropogenic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m-3. The yields (0.5-9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for anthropogenic SOA enabled application of a simplified model to calculate the chemical turnover of the anthropogenic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining at 343 K: 0.86-0.94). The anthropogenic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of anthropogenic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. A strong positive correlation was found between changes in volatility and O/C with the exception during dark

  5. Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties

    NASA Astrophysics Data System (ADS)

    Emanuelsson, E. U.; Hallquist, M.; Kristensen, K.; Glasius, M.; Bohn, B.; Fuchs, H.; Kammer, B.; Kiendler-Scharr, A.; Nehr, S.; Rubach, F.; Tillmann, R.; Wahner, A.; Wu, H.-C.; Mentel, Th. F.

    2013-03-01

    Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of α-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m-3. The yields (0.5 to 9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86-0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also

  6. Modeling SOA production from the oxidation of intermediate volatility alkanes

    NASA Astrophysics Data System (ADS)

    Aumont, B.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J.; Madronich, S.

    2012-12-01

    Secondary Organic Aerosols (SOA) production and ageing is a multigenerational oxidation process involving the formation of successive organic compounds with higher oxidation degree and lower vapour pressure. This process was investigated using the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere). Results for the C8-C24 n-alkane series show the expected trends, i.e. (i) SOA yield grows with the carbon backbone of the parent hydrocarbon, (ii) SOA yields decreases with the decreasing pre-existing organic aerosol concentration, (iii) the number of generations required to describe SOA production increases when the pre-existing organic aerosol concentration decreases. Most SOA contributors were found to be not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA) but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA). Branched alkanes are more prone to fragment in the early stage of the oxidation than their corresponding linear analogues. Fragmentation is expected to alter both the yield and the mean oxidation state of the SOA. Here, GECKO-A is applied to generate highly detailed oxidation schemes for various series of branched and cyclised alkanes. Branching and cyclisation effects on SOA yields and oxidation states will be examined.

  7. Formation of Epoxide Derived SOA and Gas-Phase Acids through Aqueous Aerosol Processing in the Southeastern United States during SOAS

    NASA Astrophysics Data System (ADS)

    Skog, K.; Teng, A.; Nguyen, T. B.; Nguyen, K.; Suda, S. R.; Xu, L.; Isaacman-VanWertz, G. A.; Feiner, P. A.; Zhang, L.; Olson, K. F.; Koss, A.; Wild, R. J.; St Clair, J.; Crounse, J.; Baumann, K.; Wennberg, P. O.; Petters, M.; Carlton, A. M. G.; Ng, N. L.; Brune, W. H.; De Gouw, J. A.; Goldstein, A. H.; Brown, S. S.; Edgerton, E. S.; McNeill, V. F.; Keutsch, F. N.

    2015-12-01

    Secondary organic aerosol (SOA) contributes to climate and adversely affects human health, but the formation of SOA is poorly understood. Recent studies have proposed that aqueous processing of water-soluble compounds like glyoxal and IEPOX can help explain the abundance of organosulfates, higher oxygen to carbon ratios, and SOA abundance. A comprehensive set of ambient gas- and aerosol-phase data was collected during June and July of 2013 as part of the Southern Oxidant and Aerosol Study (SOAS) at the Centreville, AL ground site. Both gas-phase photochemistry and aqueous-phase aerosol chemistry were modeled using a zero-dimensional box model. While it has been suggested that glyoxal can contribute to aqueous aerosol through the formation of acids and higher-molecular-weight compounds, it did not produce enhanced aqSOA concentrations. Instead, processing of aqueous glyoxal resulted in the production of gas-phase acids. AqSOA consisted almost entirely of epoxide processing products, mainly from the processing of IEPOX to methyl tetrol, and the organosulfate. In addition, the pinene oxides contributed to the formation of aqSOA, through the formation of organosulfates, diols, and organonitrates. These data are consistent with the abundance of IEPOX and pinene oxide organonitrate derived SOA seen at this site.

  8. CMAQ Application to the Southern Oxidant and Aerosol Study (SOAS)

    EPA Pesticide Factsheets

    CMAQ was used to simulate conditions during the the Southern Oxidant and Aerosol Study (SOAS) in the summer of 2013. Data collected as part of this study have been used to perform diagnostic model evaluation.

  9. An SOA model for toluene oxidation in the presence of inorganic aerosols.

    PubMed

    Cao, Gang; Jang, Myoseon

    2010-01-15

    A predictive model for secondary organic aerosol (SOA) formation including both partitioning and heterogeneous reactions is explored for the SOA produced from the oxidation of toluene in the presence of inorganic seed aerosols. The predictive SOA model comprises the explicit gas-phase chemistry of toluene, gas-particle partitioning, and heterogeneous chemistry. The resulting products from the explicit gas phase chemistry are lumped into several classes of chemical species based on their vapor pressure and reactivity for heterogeneous reactions. Both the gas-particle partitioning coefficient and the heterogeneous reaction rate constant of each lumped gas-phase product are theoretically determined using group contribution and molecular structure-reactivity. In the SOA model, the predictive SOA mass is decoupled into partitioning (OM(P)) and heterogeneous aerosol production (OM(H)). OM(P) is estimated from the SOA partitioning model developed by Schell et al. (J. Geophys. Res. 2001, 106, 28275-28293 ) that has been used in a regional air quality model (CMAQ 4.7). OM(H) is predicted from the heterogeneous SOA model developed by Jang et al. (Environ. Sci. Technol. 2006, 40, 3013-3022 ). The SOA model is evaluated using a number of the experimental SOA data that are generated in a 2 m(3) indoor Teflon film chamber under various experimental conditions (e.g., humidity, inorganic seed compositions, NO(x) concentrations). The SOA model reasonably predicts not only the gas-phase chemistry, such as the ozone formation, the conversion of NO to NO(2), and the toluene decay, but also the SOA production. The model predicted that the OM(H) fraction of the total toluene SOA mass increases as NO(x) concentrations decrease: 0.73-0.83 at low NO(x) levels and 0.17-0.47 at middle and high NO(x) levels for SOA experiments with high initial toluene concentrations. Our study also finds a significant increase in the OM(H) mass fraction in the SOA generated with low initial toluene

  10. The SOA formation model combined with semiempirical quantum chemistry for predicting UV-Vis absorption of secondary organic aerosols.

    PubMed

    Zhong, Min; Jang, Myoseon; Oliferenko, Alexander; Pillai, Girinath G; Katritzky, Alan R

    2012-07-07

    A new model for predicting the UV-visible absorption spectra of secondary organic aerosols (SOA) has been developed. The model consists of two primary parts: a SOA formation model and a semiempirical quantum chemistry method. The mass of SOA is predicted using the PHRCSOA (Partitioning Heterogeneous Reaction Consortium Secondary Organic Aerosol) model developed by Cao and Jang [Environ. Sci. Technol., 2010, 44, 727]. The chemical composition is estimated using a combination of the kinetic model (MCM) and the PHRCSOA model. The absorption spectrum is obtained by taking the sum of the spectrum of each SOA product calculated using a semiempirical NDDO (Neglect of Diatomic Differential Overlap)-based method. SOA was generated from the photochemical reaction of toluene or α-pinene at different NO(x) levels (low NO(x): 24-26 ppm, middle NO(x): 49 ppb, high NO(x): 104-105 ppb) using a 2 m(3) indoor Teflon film chamber. The model simulation reasonably agrees with the measured absorption spectra of α-pinene SOA but underestimates toluene SOA under high and middle NO(x) conditions. The absorption spectrum of toluene SOA is moderately enhanced with increasing NO(x) concentrations, while that of α-pinene SOA is not affected. Both measured and calculated UV-visible spectra show that the light absorption of toluene SOA is much stronger than that of α-pinene SOA.

  11. Key parameters controlling OH-initiated formation of secondary organic aerosol in the aqueous phase (aqSOA)

    NASA Astrophysics Data System (ADS)

    Ervens, Barbara; Sorooshian, Armin; Lim, Yong B.; Turpin, Barbara J.

    2014-04-01

    Secondary organic aerosol formation in the aqueous phase of cloud droplets and aerosol particles (aqSOA) might contribute substantially to the total SOA burden and help to explain discrepancies between observed and predicted SOA properties. In order to implement aqSOA formation in models, key processes controlling formation within the multiphase system have to be identified. We explore parameters affecting phase transfer and OH(aq)-initiated aqSOA formation as a function of OH(aq) availability. Box model results suggest OH(aq)-limited photochemical aqSOA formation in cloud water even if aqueous OH(aq) sources are present. This limitation manifests itself as an apparent surface dependence of aqSOA formation. We estimate chemical OH(aq) production fluxes, necessary to establish thermodynamic equilibrium between the phases (based on Henry's law constants) for both cloud and aqueous particles. Estimates show that no (currently known) OH(aq) source in cloud water can remove this limitation, whereas in aerosol water, it might be feasible. Ambient organic mass (oxalate) measurements in stratocumulus clouds as a function of cloud drop surface area and liquid water content exhibit trends similar to model results. These findings support the use of parameterizations of cloud-aqSOA using effective droplet radius rather than liquid water volume or drop surface area. Sensitivity studies suggest that future laboratory studies should explore aqSOA yields in multiphase systems as a function of these parameters and at atmospherically relevant OH(aq) levels. Since aerosol-aqSOA formation significantly depends on OH(aq) availability, parameterizations might be less straightforward, and oxidant (OH) sources within aerosol water emerge as one of the major uncertainties in aerosol-aqSOA formation.

  12. Primary particulate emissions and secondary organic aerosol (SOA) formation from idling diesel vehicle exhaust in China.

    PubMed

    Deng, Wei; Hu, Qihou; Liu, Tengyu; Wang, Xinming; Zhang, Yanli; Song, Wei; Sun, Yele; Bi, Xinhui; Yu, Jianzhen; Yang, Weiqiang; Huang, Xinyu; Zhang, Zhou; Huang, Zhonghui; He, Quanfu; Mellouki, Abdelwahid; George, Christian

    2017-03-26

    In China diesel vehicles dominate the primary emission of particulate matters from on-road vehicles, and they might also contribute substantially to the formation of secondary organic aerosols (SOA). In this study tailpipe exhaust of three typical in-use diesel vehicles under warm idling conditions was introduced directly into an indoor smog chamber with a 30m(3) Teflon reactor to characterize primary emissions and SOA formation during photo-oxidation. The emission factors of primary organic aerosol (POA) and black carbon (BC) for the three types of Chinese diesel vehicles ranged 0.18-0.91 and 0.15-0.51gkg-fuel(-1), respectively; and the SOA production factors ranged 0.50-1.8gkg-fuel(-1) and SOA/POA ratios ranged 0.7-3.7 with an average of 2.2. The fuel-based POA emission factors and SOA production factors from this study for idling diesel vehicle exhaust were 1-3 orders of magnitude higher than those reported in previous studies for idling gasoline vehicle exhaust. The emission factors for total particle numbers were 0.65-4.0×10(15)particleskg-fuel(-1), and particles with diameters less than 50nm dominated in total particle numbers. Traditional C2-C12 precursor non-methane hydrocarbons (NMHCs) could only explain less than 3% of the SOA formed during aging and contribution from other precursors including intermediate volatile organic compounds (IVOC) needs further investigation.

  13. Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA.

    PubMed

    Lopez-Hilfiker, F D; Mohr, C; D'Ambro, E L; Lutz, A; Riedel, T P; Gaston, C J; Iyer, S; Zhang, Z; Gold, A; Surratt, J D; Lee, B H; Kurten, T; Hu, W W; Jimenez, J; Hallquist, M; Thornton, J A

    2016-03-01

    We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) μg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.

  14. Oxidant supply and aqueous photochemical SOA formation in cloud droplets and aqueous aerosol

    NASA Astrophysics Data System (ADS)

    Turpin, B. J.; Ervens, B.; Lim, Y. B.

    2012-12-01

    Many recent laboratory, field and model studies point to significant contributions to the total secondary organic aerosol (SOA) budget from aqueous phase reactions in cloud droplets and aqueous aerosol particles. Laboratory studies of the photochemical oxidation of glyoxal and methylglyoxal in the aqueous phase show a strong dependence on the initial concentration of dissolved organics, with preferential formation of large molecules (dimers, oligomers) at the high concentrations found in ambient deliquesced aerosol particles. In such experimental studies OH radicals are produced in the aqueous phase (via hydrogen peroxide photolysis) and OH radical is assumed to be the major oxidant. An explicit aqueous photooxidation mechanism has been validated, in part, based on the observed temporal evolution of organic intermediates and products in these experiments. In this work, this mechanism was incorporated into multiphase process models (box, cloud parcel) in order to further explore aqueous SOA formation in dilute cloud droplets and concentrated aerosol particles. We found that the predicted SOA mass in both aqueous phases can be comparable despite the much lower liquid water content in aerosols, where oligomer formation is favored. Direct uptake from the gas phase was the largest source of OH radicals in the aqueous phase. In-situ production through the Fenton reaction (Fe), hydrogen peroxide and nitrate photolysis were minor sources. Since phase transfer is slower than the OH(aq) consumption by organics, modeled OH(aq) concentrations were smaller by 1-2 orders of magnitude than predicted based on thermodynamic equilibrium. Our model studies suggest that, unless there are substantial additional sources of OH radical in the aqueous phase, aqueous SOA formation will be oxidant limited. Since the phase transfer rate is a function of the drop (or particle) surface area, aqueous SOA formation may occur preferentially at or near the drop/particle surface (e.g., be surface

  15. Aerosol mass spectrometric features of biogenic SOA: observations from a plant chamber and in rural atmospheric environments.

    PubMed

    Kiendler-Scharr, Astrid; Zhang, Qi; Hohaus, Thorsten; Kleist, Einhard; Mensah, Amewu; Mentel, Thomas F; Spindler, Christian; Uerlings, Ricarda; Tillmann, Ralf; Wildt, Jürgen

    2009-11-01

    Secondary organic aerosol (SOA) is known to form from a variety of anthropogenic and biogenic precursors. Current estimates of global SOA production vary over 2 orders of magnitude. Since no direct measurement technique for SOA exists, quantifying SOA remains a challenge for atmospheric studies. The identification of biogenic SOA (BSOA) based on mass spectral signatures offers the possibility to derive source information of organic aerosol (OA) with high time resolution. Here we present data from simulation experiments. The BSOA from tree emissions was characterized with an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS). Collection efficiencies were close to 1, and effective densities of the BSOA were found to be 1.3 +/- 0.1 g/cm(3). The mass spectra of SOA from different trees were found to be highly similar. The average BSOA mass spectrum from tree emissions is compared to a BSOA component spectrum extracted from field data. It is shown that overall the spectra agree well and that the mass spectral features of BSOA are distinctively different from those of OA components related to fresh fossil fuel and biomass combustions. The simulation chamber mass spectrum may potentially be useful for the identification and interpretation of biogenic SOA components in ambient data sets.

  16. Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

    NASA Astrophysics Data System (ADS)

    Hu, W. W.; Campuzano-Jost, P.; Palm, B. B.; Day, D. A.; Ortega, A. M.; Hayes, P. L.; Krechmer, J. E.; Chen, Q.; Kuwata, M.; Liu, Y. J.; de Sá, S. S.; McKinney, K.; Martin, S. T.; Hu, M.; Budisulistiorini, S. H.; Riva, M.; Surratt, J. D.; St. Clair, J. M.; Isaacman-Van Wertz, G.; Yee, L. D.; Goldstein, A. H.; Carbone, S.; Brito, J.; Artaxo, P.; de Gouw, J. A.; Koss, A.; Wisthaler, A.; Mikoviny, T.; Karl, T.; Kaser, L.; Jud, W.; Hansel, A.; Docherty, K. S.; Alexander, M. L.; Robinson, N. H.; Coe, H.; Allan, J. D.; Canagaratna, M. R.; Paulot, F.; Jimenez, J. L.

    2015-10-01

    Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accounted by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC5H6O (fC5H6O= C5H6O+/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O in IEPOX-SOA is always elevated (12-40 ‰) but varies substantially between locations, which is shown to reflect

  17. Characterization of a real-time tracer for isoprene epoxydiols-derived secondary organic aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

    DOE PAGES

    Hu, W. W.; Campuzano-Jost, P.; Palm, B. B.; ...

    2015-10-23

    Substantial amounts of secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), which are oxidation products of isoprene mainly under low-NO conditions. Total IEPOX-SOA, which may include SOA formed from other parallel isoprene oxidation pathways, was quantified by applying positive matrix factorization (PMF) to aerosol mass spectrometer (AMS) measurements. The IEPOX-SOA fractions of organic aerosol (OA) in multiple field studies across several continents are summarized here and show consistent patterns with the concentration of gas-phase IEPOX simulated by the GEOS-Chem chemical transport model. During the Southern Oxidant and Aerosol Study (SOAS), 78 % of PMF-resolved IEPOX-SOA is accountedmore » by the measured IEPOX-SOA molecular tracers (2-methyltetrols, C5-Triols, and IEPOX-derived organosulfate and its dimers), making it the highest level of molecular identification of an ambient SOA component to our knowledge. An enhanced signal at C5H6O+ (m/z 82) is found in PMF-resolved IEPOX-SOA spectra. To investigate the suitability of this ion as a tracer for IEPOX-SOA, we examine fC5H6O (fC5H6O= C5H6O+/OA) across multiple field, chamber, and source data sets. A background of ~ 1.7 ± 0.1 ‰ (‰ = parts per thousand) is observed in studies strongly influenced by urban, biomass-burning, and other anthropogenic primary organic aerosol (POA). Higher background values of 3.1 ± 0.6 ‰ are found in studies strongly influenced by monoterpene emissions. The average laboratory monoterpene SOA value (5.5 ± 2.0 ‰) is 4 times lower than the average for IEPOX-SOA (22 ± 7 ‰), which leaves some room to separate both contributions to OA. Locations strongly influenced by isoprene emissions under low-NO levels had higher fC5H6O (~ 6.5 ± 2.2 ‰ on average) than other sites, consistent with the expected IEPOX-SOA formation in those studies. fC5H6O in IEPOX-SOA is always elevated (12–40 ‰) but varies substantially between locations, which is shown

  18. Relationship between aerosol oxidation level and hygroscopic properties of laboratory generated secondary organic aerosol (SOA) particles

    NASA Astrophysics Data System (ADS)

    Massoli, P.; Lambe, A.; Ahern, A.; Williams, L. R.; Ehn, M.; Mikkila, J.; Canagaratna, M.; Brune, W. H.; Onasch, T. B.; Jayne, J.; Petdjd, T. T.; Kulmala, M. T.; Laaksonen, A.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.

    2010-12-01

    Laboratory experiments investigated the relationship between degree of oxidation and hygroscopic properties of secondary organic aerosol (SOA) particles. The hygroscopic growth factor (HGF), the CCN activity (κCCN) and the degree of aerosol oxidation (represented by the atomic O:C ratio) were measured for α-pinene, 1,3,5-trimethylbenzene (TMB), m-xylene and α pinene/m-xylene mixture SOA generated via OH radical oxidation in an aerosol flow reactor. Our results show that both HGF and κCCN increase with O:C. The TMB and m-xylene SOA were, respectively, the least and most hygroscopic of the system studied. An average HGF of 1.25 and a κCCN of 0.2 were measured at O:C of 0.65, in agreement with results reported for ambient data. The HGF based κ(κHGF) under predicted the κCCN values of 20 to 50% for all but the TMB SOA. Within the limitations of instrumental capabilities, we define the extent to which the hygroscopic properties of SOA particles can be predicted from their oxidation level and provide parameterizations suitable for interpreting ambient data.

  19. SOA FROM ISOPRENE OXIDATION PRODUCTS: MODEL SIMULATION OF CLOUD CHEMISTRY

    EPA Science Inventory

    Recent laboratory evidence supports the hypothesis that secondary organic aerosol (SOA) is formed in the atmosphere through aqueous-phase reactions in clouds. The results of batch photochemical reactions of glyoxal, methylglyoxal and hydrogen peroxide are presented. These labor...

  20. Relationship between aerosol oxidation level and hygroscopic properties of laboratory generated secondary organic aerosol (SOA) particles

    NASA Astrophysics Data System (ADS)

    Massoli, P.; Lambe, A. T.; Ahern, A. T.; Williams, L. R.; Ehn, M.; Mikkilä, J.; Canagaratna, M. R.; Brune, W. H.; Onasch, T. B.; Jayne, J. T.; Petäjä, T.; Kulmala, M.; Laaksonen, A.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.

    2010-12-01

    Laboratory experiments investigated the relationship between oxidation level and hygroscopic properties of secondary organic aerosol (SOA) particles generated via OH radical oxidation in an aerosol flow reactor. The hygroscopic growth factor at 90% RH (HGF90%), the CCN activity ($\\kappa$ORG,CCN) and the level of oxidation (atomic O:C ratio) of the SOA particles were measured. Both HGF90% and $\\kappa$ORG,CCN increased with O:C; the HGF90% varied linearly with O:C, while $\\kappa$ORG,CCN mostly followed a nonlinear trend. An average HGF90% of 1.25 and $\\kappa$ORG,CCN of 0.19 were measured for O:C of 0.65, in agreement with results reported for ambient data. The $\\kappa$ORG values estimated from the HGF90% ($\\kappa$ORG,HGF) were 20 to 50% lower than paired $\\kappa$ORG,CCN values for all SOA particles except 1,3,5-trimethylbenzene (TMB), the least hygroscopic of the SOA systems. Within the limitations of instrumental capabilities, we show that differences in hygroscopic behavior among the investigated SOA systems may correspond to differences in elemental composition.

  1. Impact of NOx on secondary organic aerosol (SOA) formation from β-pinene photooxidation

    NASA Astrophysics Data System (ADS)

    Sarrafzadeh, Mehrnaz; Pullinen, Iida; Springer, Monika; Kleist, Einhard; Tillmann, Ralf; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Hastie, Donald R.; Wildt, Jürgen

    2016-04-01

    Secondary organic aerosols (SOA) generated from atmospheric oxidation of volatile organics contributes substantially to the global aerosol load. It has been shown that odd nitrogen (NOx) has a significant influence on the formation of this SOA. In this study, we investigated SOA formation from β-pinene photooxidation in the Jülich Plant Atmosphere Chamber (JPAC) under varying NOx conditions. At higher-NOx levels, the SOA yield was significantly suppressed by increasing the NOx concentration. However at lower-NOx levels the opposite trend, an increase in SOA with increasing NOx concentration, was observed. This increase was likely due to the increased OH concentration in the stirred flow reactor. By holding the OH concentration constant for all experiments we removed the potential effect of OH concentration on SOA mass growth. In this case increasing the NOx concentration only decreased the SOA yield. In addition, the impact of NOx on SOA formation was explored in the presence of ammonium sulfate seed aerosols. This suggested that SOA yield was only slightly suppressed under increasing NOx concentrations when seed aerosol was present.

  2. Present-day to 21st century projections of secondary organic aerosol (SOA) from a global climate-aerosol model with an explicit SOA formation scheme

    NASA Astrophysics Data System (ADS)

    Lin, G.; Penner, J. E.; Zhou, C.

    2014-12-01

    Secondary organic aerosol (SOA) has been shown to be an important component of non-refractory submicron aerosol in the atmosphere. The presence of SOA can influence the earth's radiative balance by contributing to the absorption and scattering of radiation and by altering the properties of clouds. Globally, a large fraction of SOA originates from biogenic volatile organic compounds (BVOCs), emissions of which depend on vegetation cover and climate. Temperature, CO2 concentration, and land use and land cover change have been shown to be major drivers of global isoprene emission changes in future climates. Additionally, the SOA concentration in the atmosphere not only depends on BVOC emissions, but is also controlled by anthropogenic emissions, temperature, precipitation and the oxidative capacity of the atmosphere. To project the change in SOA concentrations in the future requires a model that fully couples a BVOC emission model that represents these BVOC emission drivers, together with a sophisticated atmospheric model of SOA formation and properties. Recent studies have suggested that traditional parameterized SOA formation mechanisms that are tuned to fit smog chamber data do not fully account for the complexity and dynamics of real SOA system, calling into the question of the validity and completeness of previous SOA projections. In this study, we investigate the response of SOA mass to future physical climate change, to land cover and land use change, to changes in BVOCs emissions, and to changes in anthropogenic aerosol and gas species emissions for the year 2100, utilizing a global climate-aerosol model (CAM5-IMPACT): the NCAR Community Atmospheric Model (CAM5) coupled with a global aerosol model (IMPACT). The IMPACT model has sophisticated detailed process-based mechanisms describing aerosol microphysics and SOA formation through both gas phase and multiphase reactions. We perform sensitivity tests to isolate the relative roles of individual global change

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

    DOE PAGES

    Hu, Weiwei; Palm, Brett B.; Day, Douglas A.; ...

    2016-09-19

    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 withmore » 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

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

    SciTech Connect

    Hu, Weiwei; Palm, Brett B.; Day, Douglas A.; Campuzano-Jost, Pedro; Krechmer, Jordan E.; Peng, Zhe; de Sá, Suzane S.; Martin, Scot T.; Alexander, M. Lizabeth; Baumann, Karsten; Hacker, Lina; Kiendler-Scharr, Astrid; Koss, Abigail R.; de Gouw, Joost A.; Goldstein, Allen H.; Seco, Roger; Sjostedt, Steven J.; Park, Jeong-Hoo; Guenther, Alex B.; Kim, Saewung; Canonaco, Francesco; Prévôt, André S. H.; Brune, William H.; Jimenez, Jose L.

    2016-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Hu, Weiwei; Palm, Brett B.; Day, Douglas A.; Campuzano-Jost, Pedro; Krechmer, Jordan E.; Peng, Zhe; de Sá, Suzane S.; Martin, Scot T.; Lizabeth Alexander, M.; Baumann, Karsten; Hacker, Lina; Kiendler-Scharr, Astrid; Koss, Abigail R.; de Gouw, Joost A.; Goldstein, Allen H.; Seco, Roger; Sjostedt, Steven J.; Park, Jeong-Hoo; Guenther, Alex B.; Kim, Saewung; Canonaco, Francesco; Prévôt, André S. H.; Brune, William H.; Jimenez, Jose L.

    2016-09-01

    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.

  6. Acid-catalyzed Reactions in Model Secondary Organic Aerosol (SOA): Insights using Desorption-electrospray Ionization (DESI) Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Fiddler, M. N.; Cooks, R. G.; Shepson, P.

    2008-12-01

    Atmospheric aerosols are presently little understood in terms of their sources, formation, and effect on climate forcing, despite their significant impacts on climate change and respiratory health. Secondary organic aerosols (SOA), which were thought to arise entirely from simple gas-particle partitioning, have recently been found to contain oligomeric species which result from the condensed-phase reactions of volatile organic compounds (VOCs). The non-methane VOC with the greatest emission flux, isoprene, is known to produce aerosols through chemistry involving its oxidation products. We selected one of its major oxidation product, methacrolein, to assess its role in oligomeric SOA formation in response to the acidic conditions found in cloud water. Since it has been found that acidified aerosol produces oligomeric species with greater molecular weight and yield, acid-catalyzed oligomerization is likely a significant process in the formation of SOA. Aqueous solutions of methacrolein were acidified with sulfuric acid, and studied using linear ion trap mass spectrometry (LIT-MS) with a home-built desorption-electrospray ionization (DESI) source. An extremely heterogeneous mixture of products was produced in this system, resulting from hydrolysis, acid- catalyzed oxidation, reduction, and organosulfate formation. Evidence for disproportionation and heterocycle formation are proposed as reaction mechanisms hitherto unrecognized in the production of SOA. The proposed structure and formation mechanism for several species, based upon their MS/MS spectra, will also be presented.

  7. Secondary Organic Aerosol (SOA) formation from hydroxyl radical oxidation and ozonolysis of monoterpenes

    NASA Astrophysics Data System (ADS)

    Zhao, D. F.; Kaminski, M.; Schlag, P.; Fuchs, H.; Acir, I.-H.; Bohn, B.; Häseler, R.; Kiendler-Scharr, A.; Rohrer, F.; Tillmann, R.; Wang, M. J.; Wegener, R.; Wildt, J.; Wahner, A.; Mentel, T. F.

    2014-05-01

    Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (α-pinene, β-pinene, and limonene) by OH dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR chamber in Jülich, Germany, at low NOx (0.01-1 ppbV) and low ozone (O3) concentration. OH concentration and OH reactivity were measured directly so that the overall reaction rates of organic compounds with OH were quantified. Multi-generation reaction process, particle growth, new particle formation, particle yield, and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction of OH with organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to be dominant after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of

  8. Identifying precursors and aqueous organic aerosol formation pathways during the SOAS campaign

    NASA Astrophysics Data System (ADS)

    Sareen, Neha; Carlton, Annmarie G.; Surratt, Jason D.; Gold, Avram; Lee, Ben; Lopez-Hilfiker, Felipe D.; Mohr, Claudia; Thornton, Joel A.; Zhang, Zhenfa; Lim, Yong B.; Turpin, Barbara J.

    2016-11-01

    Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized, low-volatility organic aerosol and, in some cases, light-absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, and health. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented, forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols), leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify additional precursors and products that may be atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere into water at Brent, Alabama, during the 2013 Southern Oxidant and Aerosol Study (SOAS). Hydroxyl (OH⚫) radical oxidation experiments were conducted with the aqueous mixtures collected from SOAS to better understand the formation of SOA through gas-phase followed by aqueous-phase chemistry. Total aqueous-phase organic carbon concentrations for these mixtures ranged from 92 to 179 µM-C, relevant for cloud and fog waters. Aqueous OH-reactive compounds were primarily observed as odd ions in the positive ion mode by electrospray ionization mass spectrometry (ESI-MS). Ultra high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) spectra and tandem MS (MS-MS) fragmentation of these ions were consistent with the presence of carbonyls and tetrols. Products were observed in the negative ion mode and included pyruvate and oxalate, which were confirmed by ion chromatography. Pyruvate and oxalate have been found in the particle phase in many locations (as salts and complexes). Thus

  9. Simulating the SOA formation of isoprene from partitioning and aerosol phase reactions in the presence of inorganics

    NASA Astrophysics Data System (ADS)

    Beardsley, Ross L.; Jang, Myoseon

    2016-05-01

    The secondary organic aerosol (SOA) produced by the photooxidation of isoprene with and without inorganic seed is simulated using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model. Recent work has found the SOA formation of isoprene to be sensitive to both aerosol acidity ([H+], mol L-1) and aerosol liquid water content (LWC) with the presence of either leading to significant aerosol phase organic mass generation and large growth in SOA yields (YSOA). Classical partitioning models alone are insufficient to predict isoprene SOA formation due to the high volatility of photooxidation products and sensitivity of their mass yields to variations in inorganic aerosol composition. UNIPAR utilizes the chemical structures provided by a near-explicit chemical mechanism to estimate the thermodynamic properties of the gas phase products, which are lumped based on their calculated vapor pressure (eight groups) and aerosol phase reactivity (six groups). UNIPAR then determines the SOA formation of each lumping group from both partitioning and aerosol phase reactions (oligomerization, acid-catalyzed reactions and organosulfate formation) assuming a single homogeneously mixed organic-inorganic phase as a function of inorganic composition and VOC / NOx (VOC - volatile organic compound). The model is validated using isoprene photooxidation experiments performed in the dual, outdoor University of Florida Atmospheric PHotochemical Outdoor Reactor (UF APHOR) chambers. UNIPAR is able to predict the experimental SOA formation of isoprene without seed, with H2SO4 seed gradually titrated by ammonia, and with the acidic seed generated by SO2 oxidation. Oligomeric mass is predicted to account for more than 65 % of the total organic mass formed in all cases and over 85 % in the presence of strongly acidic seed. The model is run to determine the sensitivity of YSOA to [H+], LWC and VOC / NOx, and it is determined that the SOA formation of isoprene is most strongly related to [H

  10. Simulating the SOA formation of isoprene from partitioning and aerosol phase reactions in the presence of inorganics

    NASA Astrophysics Data System (ADS)

    Beardsley, R. L.; Jang, M.

    2015-11-01

    The secondary organic aerosol (SOA) produced by the photooxidation of isoprene with and without inorganic seed is simulated using the Unified Partitioning Aerosol Phase Reaction (UNIPAR) model. Recent work has found the SOA formation of isoprene to be sensitive to both aerosol acidity ([H+]) and aerosol liquid water content (LWC) with the presence of either leading to significant aerosol phase organic mass generation and large growth in SOA yields (YSOA). Classical partitioning models alone are insufficient to predict isoprene SOA formation due to the high volatility of the photooxidation products and the sensitivity of their mass yields to variations in inorganic aerosol composition. UNIPAR utilizes the chemical structures provided by a near-explicit chemical mechanism to estimate the thermodynamic properties of the gas phase products, which are lumped based on their calculated vapor pressure (8 groups) and aerosol phase reactivity (6 groups). UNIPAR then determines the SOA formation of each lumping group from both partitioning and aerosol phase reactions (oligomerization, acid catalyzed reactions, and organosulfate formation) assuming a single homogeneously mixed organic-inorganic phase as a function of inorganic composition and VOC / NOx. The model is validated using isoprene photooxidation experiments performed in the dual, outdoor UF APHOR chambers. UNIPAR is able to predict the experimental SOA formation of isoprene without seed, with H2SO4 seed gradually titrated by ammonia, and with the acidic seed generated by SO2 oxidation. Oligomeric mass is predicted to account for more than 65 % of the total OM formed in all cases and over 85 % in the presence of strongly acidic seed. The model is run to determine the sensitivity of YSOA to [H+], LWC, and VOC / NOx, and it is determined that the SOA formation of isoprene is most strongly related to [H+] but is dynamically related to all three parameters. For VOC / NOx > 10, with increasing NOx both experimental and

  11. A comparison of secondary organic aerosol (SOA) yields and composition from ozonolysis of monoterpenes at varying concentrations of NO2

    NASA Astrophysics Data System (ADS)

    Draper, D. C.; Farmer, D. K.; Desyaterik, Y.; Fry, J. L.

    2015-05-01

    The effect of NO2 on secondary organic aerosol (SOA) formation from ozonolysis of α-pinene, β-pinene, Δ3-carene, and limonene was investigated using a dark flow-through reaction chamber. SOA mass yields were calculated for each monoterpene from ozonolysis with varying NO2 concentrations. Kinetics modeling of the first generation gas-phase chemistry suggests that differences in observed aerosol yields for different NO2 concentrations are consistent with NO3 formation and subsequent competition between O3 and NO3 to oxidize each monoterpene. α-pinene was the only monoterpene studied that showed a systematic decrease in both aerosol number concentration and mass concentration with increasing [NO2]. β-pinene and Δ3-carene produced fewer particles at higher [NO2], but both retained moderate mass yields. Limonene exhibited both higher number concentrations and greater mass concentrations at higher [NO2]. SOA from each experiment was collected and analyzed by HPLC-ESI-MS, enabling comparisons between product distributions for each system. In general, the systems influenced by NO3 oxidation contained more high molecular weight products (MW >400 amu), suggesting the importance of oligomerization mechanisms in NO3-initiated SOA formation. α-pinene, which showed anomalously low aerosol mass yields in the presence of NO2, showed no increase in these oligomer peaks, suggesting that lack of oligomer formation is a likely cause of α-pinene's near 0% yields with NO3. Through direct comparisons of mixed-oxidant systems, this work suggests that NO3 is likely to dominate nighttime oxidation pathways in most regions with both biogenic and anthropogenic influences. Therefore, accurately constraining SOA yields from NO3 oxidation, which vary substantially with the VOC precursor, is essential in predicting nighttime aerosol production.

  12. Secondary Organic Aerosol (SOA) Formation from Hydroxyl Radical Oxidation and Ozonolysis of Monoterpenes

    NASA Astrophysics Data System (ADS)

    Zhao, Defeng; Kaminski, Martin; Schlag, Patrick; Fuchs, Hendrik; Acir, Ismail-Hakki; Bohn, Birger; Haeseler, Rolf; Kiendler-Scharr, Astrid; Rohrer, Franz; Tillmann, Ralf; Wang, Mingjin; Wegner, Robert; Wahner, Andreas; Mentel, Thomas

    2014-05-01

    Hydroxyl radical (OH) oxidation and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. The pure OH oxidation of monoterpenes, an important biogenic VOC class, has seldom been investigated. In order to elucidate the importance of the reaction pathyways of the OH oxidation and ozonolysis and their roles in particle formation and growth, we investigated the particle formation of several common monoterpenes (alpha-pinene, beta-pinene, and limonene) in the large atmosphere simulation chamber SAPHIR in Juelich, Germany. The experiments were conducted for both OH dominant and pure ozonolysis case (in the presence of CO as OH scavenger) at ambient relevant conditions (low OA, low VOC and low NOx concentration). OH and ozone (O3) concentrations were measured so that the oxidation rates of OH and O3 with precursors were quantified. The particle formation and growth, aerosol yield, multi-generation reaction process and aerosol composition were analyzed. Pure ozonolysis generated a large amount of particles indicating ozonolysis plays an important role in particle formation as well as OH oxidation. In individual experiments, particle growth rates did not necessarily correlate with OH or O3 oxidation rates. However, comparing the growth rates at similar OH or O3 oxidation rates shows that generally, OH oxidation and ozonolysis have similar efficiency in particle growth. Multi-generation products are shown to be important in the OH oxidation experiment based on aerosol yield "growth curve" (Ng et al., 2006). The reaction process of OH oxidation experiments was analyzed as a function of OH dose to elucidate the role of functionalization and fragmentation. A novel analysis was developed to link the particle formation with the reaction with OH, which was also used to examine the role of functionalization and fragmentation in the particle formation by OH oxidation. These analyses show

  13. Modeling Gas-Particle Partitioning of SOA: Effects of Aerosol Physical State and RH

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Seinfeld, J.

    2011-12-01

    Aged tropospheric aerosol particles contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. In liquid aerosol particles non-ideal mixing of all species determines whether the condensed phase undergoes liquid-liquid phase separation or whether it is stable in a single mixed phase, and whether it contains solid salts in equilibrium with their saturated solution. The extended thermodynamic model AIOMFAC is able to predict such phase states by representing the variety of organic components using functional groups within a group-contribution concept. The number and composition of different condensed phases impacts the diversity of reaction media for multiphase chemistry and the gas-particle partitioning of semivolatile species. Recent studies show that under certain conditions biogenic and other organic-rich particles can be present in a highly viscous, semisolid or amorphous solid physical state, with consequences regarding reaction kinetics and mass transfer limitations. We present results of new gas-particle partitioning computations for aerosol chamber data using a model based on AIOMFAC activity coefficients and state-of-the-art vapor pressure estimation methods. Different environmental conditions in terms of temperature, relative humidity (RH), salt content, amount of precursor VOCs, and physical state of the particles are considered. We show how modifications of absorptive and adsorptive gas-particle mass transfer affects the total aerosol mass in the calculations and how the results of these modeling approaches compare to data of aerosol chamber experiments, such as alpha-pinene oxidation SOA. For a condensed phase in a mixed liquid state containing ammonium sulfate, the model predicts liquid-liquid phase separation up to high RH in case of, on average, moderately hydrophilic organic compounds, such as first generation oxidation products of alpha-pinene. The computations also reveal that treating liquid phases as ideal

  14. Land cover maps, BVOC emissions, and SOA burden in a global aerosol-climate model

    NASA Astrophysics Data System (ADS)

    Stanelle, Tanja; Henrot, Alexandra; Bey, Isaelle

    2015-04-01

    It has been reported that different land cover representations influence the emission of biogenic volatile organic compounds (BVOC) (e.g. Guenther et al., 2006). But the land cover forcing used in model simulations is quite uncertain (e.g. Jung et al., 2006). As a consequence the simulated emission of BVOCs depends on the applied land cover map. To test the sensitivity of global and regional estimates of BVOC emissions on the applied land cover map we applied 3 different land cover maps into our global aerosol-climate model ECHAM6-HAM2.2. We found a high sensitivity for tropical regions. BVOCs are a very prominent precursor for the production of Secondary Organic Aerosols (SOA). Therefore the sensitivity of BVOC emissions on land cover maps impacts the SOA burden in the atmosphere. With our model system we are able to quantify that impact. References: Guenther et al. (2006), Estimates of global terrestrial isoprene emissions using MEGAN, Atmos. Chem. Phys., 6, 3181-3210, doi:10.5194/acp-6-3181-2006. Jung et al. (2006), Exploiting synergies of global land cover products for carbon cycle modeling, Rem. Sens. Environm., 101, 534-553, doi:10.1016/j.rse.2006.01.020.

  15. simpleGAMMA - a reduced model of secondary organic aerosol formation in the aqueous aerosol phase (aaSOA)

    NASA Astrophysics Data System (ADS)

    Woo, J. L.; McNeill, V. F.

    2015-01-01

    There is increasing evidence that the uptake and aqueous processing of water-soluble volatile organic compounds (VOCs) by wet aerosols or cloud droplets is an important source of secondary organic aerosol (SOA). We recently developed GAMMA (Gas-Aerosol Model for Mechanism Analysis), a zero-dimensional kinetic model that couples gas-phase and detailed aqueous-phase atmospheric chemistry for speciated prediction of SOA and organosulfate formation in cloudwater or aqueous aerosols. Results from GAMMA simulations of SOA formation in aerosol water (McNeill et al., 2012) indicate that it is dominated by two pathways: isoprene epoxydiol (IEPOX) uptake followed by ring-opening chemistry (under low-NOx conditions) and glyoxal uptake. This suggested that it is possible to model the majority of aqueous aerosol phase SOA mass using a highly simplified reaction scheme. We have therefore developed a reduced version of GAMMA, simpleGAMMA. Close agreement in predicted aaSOA mass is observed between simpleGAMMA and GAMMA under all conditions tested (between pH 1-4 and RH 40-80%) after 12 h of simulation. simpleGAMMA is computationally efficient and suitable for coupling with larger-scale atmospheric chemistry models.

  16. Identification and Characterization of Biogenic SOA Component in Ambient Aerosols Based on Aerosol Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Jimenez, J.; Allan, J. D.; Kiendler-Scharr, A.; Tian, J.; Canagaratna, M. R.; Williams, B.; Worsnop, D. R.; Coe, H.; Goldstein, A.; Mentel, T. F.

    2008-12-01

    Recently studies have shown that multivariate factor analysis of the highly time-resolved mass spectral data obtained with an Aerodyne Aerosol Mass Spectrometer (AMS) may allow the classification and simplification of complex organic aerosol (OA) mixtures into components that are chemically meaningful and can be related to different sources and transformation processes. Two factor analysis techniques, including the Multiple Component Analysis (MCA) method (Zhang et al., 2007) and the Positive Matrix Factorization (PMF) method (Paatero and Tapper, 1994), were applied to a Quadrupole-AMS dataset acquired from Chebogue Pt., Nova Scotia in summer 2004. Multiple OA components were determined, including a hydrocarbon-like OA (HOA) component similar in mass spectra to the hydrocarbon substances observed at urban locations and two oxygenated OA (OA) components that show different fragmentation patterns and oxygen-to-carbon ratios in their mass spectra. The HOA component correlates with inert primary emission tracers (e.g., EC and CO) and likely represents diluted POA transported from urban locations. The highly oxygenated component (OOA-I) correlates well with sulfate and shows a mass spectrum resembling that of fulvic acid - a model compound representative for highly processed/oxidized organics in the environment. The less oxygenated OA component (OOA-II) reveals a mass spectral pattern that compares well with those of the biogenic SOA produced from the mixture of VOCs emitted by spruce, pine and birch trees during exposure to ozone and UV-photolysis in the Jülich plant chamber. In addition, the time series of OOA-II correlates with biogenic SOA tracer compounds determined by the thermal desorption aerosol GC/MS-FID (TAG) instrument. Furthermore, the time-resolved size distributions of OOA components, their correlations with parallel gas and aerosol measurements, and backtrajectory analysis of air masses all support the association of OOA-II to biogenic sources. Finally

  17. Simulation of aromatic SOA formation using the lumping model integrated with explicit gas-phase kinetic mechanisms and aerosol-phase reactions

    NASA Astrophysics Data System (ADS)

    Im, Y.; Jang, M.; Beardsley, R. L.

    2013-03-01

    The Unified Partitioning-Aerosol phase Reaction (UNIPAR) model has been developed to predict the secondary organic aerosol (SOA) formation through multiphase reactions. An explicit gas-kinetic model was employed to express gas-phase oxidation of aromatic hydrocarbons. Gas-phase products are grouped based on volatility (6 levels) and reactivity (5 levels) and used to construct the stoichiometric coefficients (αi,j) matrix, the set of parameters used to describe the concentrations of organic compounds in multiphase. Weighting of the αi,j matrix as a function of NOx improved the evaluation of NOx effects on SOA. The total amount of organic matter (OMT) is predicted by two modules in the UNIPAR model: OMP by a partitioning process and OMAR by aerosol-phase reactions. OMP is estimated using the SOA partitioning model that has been used in a regional air quality model (CMAQ 5.0.1). OMAR predicts multiphase reactions of organic compounds, such as oligomerization, acid-catalyzed reactions, and organosulfate (OS) formation. The model was evaluated with the SOA data produced from the photooxidation of toluene and 1,3,5-trimethylbenzene using an outdoor reactor (UF-APHOR chamber). The model reasonably simulates SOA formation under various aerosol acidities, NOx concentrations, humidities and temperatures. Furthermore, the OS fraction in the SOA predicted by the model was in good agreement with the experimentally measured OS fraction.

  18. Organic Aerosol Formation in the Humid, Photochemically-Active Southeastern US: SOAS Experiments and Simulations

    NASA Astrophysics Data System (ADS)

    Sareen, N.; Lim, Y. B.; Carlton, A. G.; Turpin, B. J.

    2013-12-01

    Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized low volatility organic aerosol and, in some cases, light absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, health, and the environment. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols) leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify other precursors that are atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere at Brent, Alabama during the Southern Oxidant and Aerosol Study (SOAS). Four mist chambers in parallel collected ambient gases in a DI water medium at 20-25 LPM with a 4 hr collection time. Total organic carbon (TOC) values in daily composited samples were 64-180 μM. Aqueous OH radical oxidation experiments were conducted with these mixtures in a newly designed cuvette chamber to understand the formation of SOA through gas followed by aqueous chemistry. OH radicals (3.5E-2 μM [OH] s-1) were formed in-situ in the chamber, continuously by H2O2 photolysis. Precursors and products of these aqueous OH experiments were characterized using ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. ESI-MS results from a June 12th, 2013 sample showed precursors to be primarily odd, positive mode ions, indicative of the presence of non-nitrogen containing alcohols, aldehydes, organic peroxides, or epoxides. Products were seen in the negative mode and included organic acid ions like pyruvate

  19. Is dry deposition of semi-volatile organic gases a significant loss of secondary organic aerosols (SOA)?

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Aumont, B.; Knote, C. J.; Lee-Taylor, J. M.; Madronich, S.

    2013-12-01

    Dry deposition removal of semi-volatile organic compounds from the atmosphere and its impact on organic aerosol mass is currently under-explored and not well represented in chemistry-climate models, especially for the many complex partly oxidized organics involved in particle formation. The main reason for this omission is that current models use simplified SOA mechanisms that lump precursors and their products into volatility bins, therefore losing information on important properties of individual molecules (or groups) that are needed to calculate dry deposition. In this study, we apply the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate SOA formation and estimate the influence of dry deposition of gas-phase organics on SOA concentrations downwind of an urban area (Mexico City), as well as over a pine forest. SOA precursors considered here include short- and long-chain alkanes (C3-25), alkenes, light aromatics, isoprene and monoterpenes. We show that dry deposition of oxidized gases is not an efficient sink for anthropogenic SOA, as it removes <5% of SOA within the city's boundary layer and ~15% downwind. The effect on biogenic SOA is however significantly larger. We discuss reasons for these differences, and investigate separately the impacts on short and long-chain species. We show that the dry deposition is competing with the uptake of gases to the aerosol phase. In the absence of this condensation, ~50% of the regionally produced mass downwind of Mexico City would have been dry-deposited. However, because dry deposition of submicron aerosols is slow, condensation onto particles protects organic gases from deposition and therefore increases their atmospheric burden and lifetime. We use the explicit GECKO-A model to build an empirical parameterization for use in 3D models. Removal (dry and wet) of organic vapors depends on their solubility, and required Henry's law solubility coefficients were estimated for

  20. Simulation of aromatic SOA formation using the lumping model integrated with explicit gas-phase kinetic mechanisms and aerosol-phase reactions

    NASA Astrophysics Data System (ADS)

    Im, Y.; Jang, M.; Beardsley, R. L.

    2014-04-01

    The Unified Partitioning-Aerosol phase Reaction (UNIPAR) model has been developed to predict the secondary organic aerosol (SOA) formation through multiphase reactions. The model was evaluated with aromatic SOA data produced from the photooxidation of toluene and 1,3,5-trimethylbenzene (135-TMB) under various concentrations of NOx and SO2 using an outdoor reactor (University of Florida Atmospheric PHotochemical Outdoor Reactor (UF-APHOR) chamber). When inorganic species (sulfate, ammonium and water) are present in aerosol, the prediction of both toluene SOA and 135-TMB SOA, in which the oxygen-to-carbon (O : C) ratio is lower than 0.62, are approached under the assumption of a complete organic/electrolyte-phase separation below a certain relative humidity. An explicit gas-kinetic model was employed to express gas-phase oxidation of aromatic hydrocarbons. Gas-phase products are grouped based on their volatility (6 levels) and reactivity (5 levels) and exploited to construct the stoichiometric coefficient (αi,j) matrix, the set of parameters used to describe the concentrations of organic compounds in multiphase. Weighting of the αi,j matrix as a function of NOx improved the evaluation of NOx effects on aromatic SOA. The total amount of organic matter (OMT) is predicted by two modules in the UNIPAR model: OMP by a partitioning process and OMAR by aerosol-phase reactions. The OMAR module predicts multiphase reactions of organic compounds, such as oligomerization, acid-catalyzed reactions, and organosulfate (OS) formation. The model reasonably simulates SOA formation under various aerosol acidities, NOx concentrations, humidities and temperatures. Furthermore, the OS fractions in the SOA predicted by the model were in good agreement with the experimentally measured OS fractions.

  1. Secondary Organic Aerosol Formation and Aging in a Flow Reactor in the Forested Southeast US during SOAS

    NASA Astrophysics Data System (ADS)

    Hu, W.; Palm, B. B.; Hacker, L.; Campuzano Jost, P.; Day, D. A.; de Sá, S. S.; Ayres, B. R.; Draper, D.; Fry, J.; Ortega, A. M.; Kiendler-Scharr, A.; Pajunoja, A.; Virtanen, A.; Krechmer, J.; Canagaratna, M. R.; Thompson, S.; Yatavelli, R. L. N.; Stark, H.; Worsnop, D. R.; Martin, S. T.; Farmer, D.; Brown, S. S.; Jimenez, J. L.

    2015-12-01

    A major field campaign (Southern Oxidant and Aerosol Study, SOAS) was conducted in summer 2013 in a forested area in Centreville Supersite, AL (SEARCH network) in the southeast U.S. To investigate secondary organic aerosol (SOA) formation from biogenic volatile organic compounds (BVOCs), 3 oxidation flow reactors (OFR) were used to expose ambient air to oxidants and their output was analyzed by state-of-the-art gas and aerosol instruments including a High-Resolution Aerosol Mass Spectrometer (HR-AMS), a HR Proton-Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-TOFMS), and Two HR-TOF Chemical Ionization Mass Spectrometers (HRToF-CIMS). Ambient air was exposed 24/7 to variable concentrations of each of the 3 main atmospheric oxidants (OH, NO3 radicals and O3) to investigate the oxidation of BVOCs (including isoprene derived epoxydiols, IEPOX) and SOA formation and aging. Effective OH exposures up to 1×1013 molec cm-3 s were achieved, equivalent to over a month of aging in the atmosphere. Multiple oxidation products from isoprene and monoterpenes including small gas-phase acids were observed in OH OFR. High SOA formation of up to 12 μg m-3 above ambient concentrations of 5 μg m-3 was observed under intermediate OH exposures, while very high OH exposures led to destruction of ~30% of ambient OA, indicating shifting contributions of functionalization vs. fragmentation, consistent with results from urban and terpene-dominated environments. The highest SOA enhancements were 3-4 times higher than ambient OA. More SOA is typically formed during nighttime when terpenes are higher and photochemistry is absent, and less during daytime when isoprene is higher, although the IEPOX pathway is suppressed in the OFR. SOA is also observed after exposure of ambient air to O3 or NO3, although the amounts and oxidation levels were lower than for OH. Formation of organic nitrates in the NO3 reaction will also be discussed.A major field campaign (Southern Oxidant and Aerosol

  2. Modeling the formation of secondary organic aerosol (SOA). 2. The predicted effects of relative humidity on aerosol formation in the alpha-pinene-, beta-pinene-, sabinene-, delta 3-carene-, and cyclohexene-ozone systems.

    PubMed

    Seinfeld, J H; Erdakos, G B; Asher, W E; Pankow, J F

    2001-05-01

    Atmospheric oxidation of volatile organic compounds can lead to the formation of secondary organic aerosol (SOA) through the gas/particle (G/P) partitioning of the oxidation products. Since water is ubiquitous in the atmosphere, the extent of the partitioning for any individual organic product depends not only on the amounts and properties of the partitioning organic compounds, but also on the amount of water present. Predicting the effects of water on the atmospheric G/P distributions of organic compounds is, therefore, central to understanding SOA formation. The goals of the current work are to gain understanding of how increases in RH affect (1) overall SOA yields, (2) water uptake by SOA, (3) the behaviors of individual oxidation products, and (4) the fundamental physical properties of the SOA phase that govern the G/P distribution of each of the oxidation products. Part 1 of this series considered SOA formation from five parent hydrocarbons in the absence of water. This paper predicts how adding RH to those systems uniformly increases both the amount of condensed organic mass and the amount of liquid water in the SOA phase. The presence of inorganic components is not considered. The effect of increasing RH is predicted to be stronger for SOA produced from cyclohexene as compared to SOA produced from four monoterpenes. This is likely a result of the greater general degree of oxidation (and hydrophilicity) of the cyclohexene products. Good agreement was obtained between predicted SOA yields and laboratory SOA yield data actually obtained in the presence of water. As RH increases, the compounds that play the largest roles in changing both the organic and water masses in the SOA phase are those with vapor pressures that are intermediate between those of essentially nonvolatile and highly volatile species. RH-driven changes in the compound-dependent G/P partitioning coefficient Kp result from changes in both the average molecular weight MWom of the absorbing

  3. Influence of dry deposition of semi-volatile organic compounds (VOC) on secondary organic aerosol (SOA) formation in the Mexico City plume

    NASA Astrophysics Data System (ADS)

    Hodzic, Alma; Madronich, Sasha; Aumont, Bernard; Lee-Taylor, Julia; Karl, Thomas

    2013-04-01

    The dry deposition removal of organic compounds from the atmosphere and its impact on organic aerosol mass is currently unexplored and unaccounted for in chemistry-climate models. The main reason for this omission is that current models use simplified SOA mechanisms that lump precursors and their products into volatility bins, therefore losing information on other important properties of individual molecules (or groups) that are needed to calculate dry deposition. In this study, we apply the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate SOA formation and estimate the influence of dry deposition of VOCs on SOA concentrations downwind of Mexico City. SOA precursors considered here include short- and long-chain alkanes (C3-25), alkenes, and light aromatics. The results suggest that 90% of SOA produced in Mexico City originates from the oxidation and partitioning of long-chain (C>12) alkanes, while the regionally exported SOA is almost equally produced from long-chain alkanes and from shorter alkanes and light aromatics. We show that dry deposition of oxidized gases is not an efficient sink for SOA, as it removes <5% of SOA within the city's boundary layer and ~15% downwind. We discuss reasons for this limited influence, and investigate separately the impacts on short and long-chain species. We show that the dry deposition is competing with the uptake of gases to the aerosol phase, and because dry deposition of submicron aerosols is slow, condensation onto particles protects organic gases from deposition and therefore increases their atmospheric burden and lifetime. In the absence of this condensation, ~50% of the regionally produced mass would have been dry-deposited.

  4. Secondary Organic Aerosol Formation in the Captive Aerosol Growth and Evolution (CAGE) Chambers during the Southern Oxidant and Aerosol Study (SOAS) in Centreville, AL

    NASA Astrophysics Data System (ADS)

    Leong, Y.; Karakurt Cevik, B.; Hernandez, C.; Griffin, R. J.; Taylor, N.; Matus, J.; Collins, D. R.

    2013-12-01

    Secondary organic aerosol (SOA) represents a large portion of sub-micron particulate matter on a global scale. The composition of SOA and its formation processes are heavily influenced by anthropogenic and biogenic activity. Volatile organic compounds (VOCs) that are emitted naturally from forests or from human activity serve as precursors to SOA formation. Biogenic SOA (BSOA) is formed from biogenic VOCs and is prevalent in forested regions like the Southeastern United States. The formation and enhancement of BSOA under anthropogenic influences such as nitrogen oxides (NOx), sulfur dioxide (SO2), and oxygen radicals are still not well understood. The lack of information on anthropogenic BSOA enhancement and the reversibility of SOA formation could explain the underprediction of SOA in current models. To address some of these gaps in knowledge, this study was conducted as part of the Southern Oxidant and Aerosol Study (SOAS) in Centreville, AL during the summer of 2013. SOA growth experiments were conducted in two Captive Aerosol Growth and Evolution (CAGE) outdoor chambers located at the SEARCH site. Ambient trace gas concentrations were maintained in these chambers using semi-permeable gas-exchange membranes, while studying the growth of injected monodisperse seed aerosol. The control chamber was operated under ambient conditions; the relative humidity and oxidant and NOx levels were perturbed in the second chamber. This design allows experiments to capture the natural BSOA formation processes in the southeastern atmosphere and to study the influence of anthropogenic activity on aerosol chemistry. Chamber experiments were periodically monitored with physical and chemical instrumentation including a scanning mobility particle sizer (SMPS), a cloud condensation nuclei counter (CCNC), a humidified tandem differential mobility analyzer (H-TDMA), and an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The CAGE experiments focused on SOA

  5. SOA YIELDS AND ORGANIC PRODUCT DISTRIBUTION FROM NATURAL HYDROCARBON/NOX IRRADIATIONS

    EPA Science Inventory

    Secondary organic aerosol (SOA) typically comprises one-quarter to one-third of the ambient aerosol mass in summertime urban atmospheres. In tropospheric environments, the main precursors of SOA come from aromatic and natural hydrocarbons. Recent work by various investigators...

  6. Development of new parameterizations for SOA production from SVOC and IVOC oxidation

    NASA Astrophysics Data System (ADS)

    Lemaire, Vincent; Coll, Isabelle; Camredon, Marie; Aumont, Bernard; Siour, Guillaume

    2014-05-01

    Recent experimental studies have demonstrated the partially volatile pattern of primary organic aerosol (POA) that is actually associated with organic species of so-called intermediate volatility (IVOCs), and by semi-volatile (SVOCs) species. Indeed, 50% to 75% of the total emitted mass of POA may be present in the atmospheric gas phase in accordance with the thermodynamic properties of its components (Shrivastava et al., 2006). During the processing of the emission plume, this gaseous material will then undergo photochemical oxidation, enhancing the production of secondary organic aerosol (SOA) (Robinson et al., 2007; Hodzic et al., 2010; Lee-Taylor et al., 2011). Considering POA as non volatile in Chemistry Transport Models (CTMs) could thus lead to an underestimation of SOA and an overestimation of POA (Aksoyoglu et al., 2011) and bias the temporal formation of the organic aerosol (Kroll et al., 2007; Presto et al., 2012). However, very rare experimental data exist on the fate of these species and their aerosol yield, but all existing studies have shown a significant SOA production (Presto et al., 2009; Miracolo et al., 2010; Lambe et al., 2012). Our works aims at including and testing in the CHIMERE CTM new parameterizations of SOA formation from the oxidation of IVOCs and SVOCs, arising from explicit 0D-model experiments. Our approach is based on the works of Aumont et al., (2013) who used the GECKO-A tool (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) to generate the explicit chemistry and gas-particle partitioning of superior alkanes and their oxidation products. Using this explicit scheme, Aumont et al., (2013) indeed produced 0D simulations of the oxidation of given SVOCs and IVOCs under different initial conditions of organic aerosol mass. We first focused on the chemistry of n-hexadecane. From the 0D-experiments, we tested the influence of the number of first generation surrogate species and the number of generation taken

  7. Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2-Methyl-3-Buten-2-ol (MBO) in the Atmosphere

    PubMed Central

    2012-01-01

    2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C5H12O6S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM2.5) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM2.5 collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA. PMID:22849588

  8. Organosulfates as tracers for secondary organic aerosol (SOA) formation from 2-methyl-3-buten-2-ol (MBO) in the atmosphere.

    PubMed

    Zhang, Haofei; Worton, David R; Lewandowski, Michael; Ortega, John; Rubitschun, Caitlin L; Park, Jeong-Hoo; Kristensen, Kasper; Campuzano-Jost, Pedro; Day, Douglas A; Jimenez, Jose L; Jaoui, Mohammed; Offenberg, John H; Kleindienst, Tadeusz E; Gilman, Jessica; Kuster, William C; de Gouw, Joost; Park, Changhyoun; Schade, Gunnar W; Frossard, Amanda A; Russell, Lynn; Kaser, Lisa; Jud, Werner; Hansel, Armin; Cappellin, Luca; Karl, Thomas; Glasius, Marianne; Guenther, Alex; Goldstein, Allen H; Seinfeld, John H; Gold, Avram; Kamens, Richard M; Surratt, Jason D

    2012-09-04

    2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C(5)H(12)O(6)S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM(2.5)) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM(2.5) collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA.

  9. Fundamental Heterogeneous Reaction Chemistry Related to Secondary Organic Aerosols (SOA) in the Atmosphere

    NASA Astrophysics Data System (ADS)

    Akimoto, H.

    2016-11-01

    Typical reaction pathways of formation of dicarboxylic acids, larger multifunctional compounds, oligomers, and organosulfur and organonitrogen compounds in secondary organic aerosols (SOA), revealed by laboratory experimental studies are reviewed with a short introduction to field observations. In most of the reactions forming these compounds, glyoxal, methyl glyoxal and related difunctional carbonyl compounds play an important role as precursors, and so their formation pathways in the gas phase are discussed first. A substantial discussion is then presented for the OH-initiated aqueous phase radical oxidation reactions of glyoxal and other carbonyls which form dicarboxylic acids, larger multifunctional compounds and oligomers, and aqueous-phase non-radical reactions which form oligomers, organosulfates and organonitrogen compounds. Finally, the heterogeneous oxidation reaction of gaseous O3, OH and NO3 with liquid and solid organic aerosols at the air-particle interface is discussed relating to the aging of SOA in the atmosphere.

  10. Simulation of semi-explicit mechanisms of SOA formation from glyoxal in aerosol in a 3-D model

    NASA Astrophysics Data System (ADS)

    Knote, C.; Hodzic, A.; Jimenez, J. L.; Volkamer, R.; Orlando, J. J.; Baidar, S.; Brioude, J.; Fast, J.; Gentner, D. R.; Goldstein, A. H.; Hayes, P. L.; Knighton, W. B.; Oetjen, H.; Setyan, A.; Stark, H.; Thalman, R.; Tyndall, G.; Washenfelder, R.; Waxman, E.; Zhang, Q.

    2014-06-01

    New pathways to form secondary organic aerosol (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of the proposed precursors. It has both anthropogenic and biogenic sources, and readily partitions into the aqueous phase of cloud droplets and deliquesced particles where it undergoes both reversible and irreversible chemistry. In this work we extend the regional scale chemistry transport model WRF-Chem to include detailed gas-phase chemistry of glyoxal formation as well as a state-of-the-science module describing its partitioning and reactions in the aerosol aqueous-phase. A comparison of several proposed mechanisms is performed to quantify the relative importance of different formation pathways and their regional variability. The CARES/CalNex campaigns over California in summer 2010 are used as case studies to evaluate the model against observations. A month-long simulation over the continental United States (US) enables us to extend our results to the continental scale. In all simulations over California, the Los Angeles (LA) basin was found to be the hot spot for SOA formation from glyoxal, which contributes between 1% and 15% of the model SOA depending on the mechanism used. Our results indicate that a mechanism based only on a reactive (surface limited) uptake coefficient leads to higher SOA yields from glyoxal compared to a more detailed description that considers aerosol phase state and chemical composition. In the more detailed simulations, surface uptake is found to give the highest SOA mass yields compared to a volume process and reversible formation. We find that the yields of the latter are limited by the availability of glyoxal in aerosol water, which is in turn controlled by an increase in the Henry's law constant depending on salt concentrations ("salting-in"). A time dependence in this increase prevents substantial partitioning of glyoxal into aerosol water at high salt concentrations. If this limitation is removed, volume

  11. Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Tuet, Wing Y.; Chen, Yunle; Xu, Lu; Fok, Shierly; Gao, Dong; Weber, Rodney J.; Ng, Nga L.

    2017-01-01

    Particulate matter (PM), of which a significant fraction is comprised of secondary organic aerosols (SOA), has received considerable attention due to its health implications. In this study, the water-soluble oxidative potential (OPWS) of SOA generated from the photooxidation of biogenic and anthropogenic hydrocarbon precursors (isoprene, α-pinene, β-caryophyllene, pentadecane, m-xylene, and naphthalene) under different reaction conditions (RO2+ HO2 vs. RO2+ NO dominant, dry vs. humid) was characterized using dithiothreitol (DTT) consumption. The measured intrinsic OPWS-DTT values ranged from 9 to 205 pmol min-1 µg-1 and were highly dependent on the specific hydrocarbon precursor, with naphthalene and isoprene SOA generating the highest and lowest OPWS-DTT values, respectively. Humidity and RO2 fate affected OPWS-DTT in a hydrocarbon-specific manner, with naphthalene SOA exhibiting the most pronounced effects, likely due to the formation of nitroaromatics. Together, these results suggest that precursor identity may be more influential than reaction condition in determining SOA oxidative potential, demonstrating the importance of sources, such as incomplete combustion, to aerosol toxicity. In the context of other PM sources, all SOA systems, with the exception of naphthalene SOA, were less DTT active than ambient sources related to incomplete combustion, including diesel and gasoline combustion as well as biomass burning. Finally, naphthalene SOA was as DTT active as biomass burning aerosol, which was found to be the most DTT-active OA source in a previous ambient study. These results highlight a need to consider SOA contributions (particularly from anthropogenic hydrocarbons) to health effects in the context of hydrocarbon emissions, SOA yields, and other PM sources.

  12. Constraining the properties of hydrocarbon oxidation products via SOA studies at high loadings

    NASA Astrophysics Data System (ADS)

    Hunter, J. F.; Carrasquillo, A. J.; Daumit, K. E.; Franklin, J. P.; Boulanger, K.; Cross, E. S.; Worsnop, D. R.; Kroll, J. H.

    2013-12-01

    The oxidation processes that lead to the formation of secondary organic aerosol (SOA) generate products with a spectrum of vapor pressures. In accordance with absorptive partitioning theory, only a fraction of these components will condense under typical experimental and atmospheric conditions at low to medium organic aerosol concentration (Coa). The more volatile products may go on to form additional aerosol or other oxidation products by serving as precursors in further oxidation chemistry. They may also serve as sinks for airborne organic carbon if they are lost to environmental surfaces prior to reaction. As Coa is increased, more volatile oxidation products will partition to the condensed phase, where they can be measured using conventional aerosol techniques. In the limit of very high Coa, the aerosol yield plateaus somewhere at or below an organic carbon yield of 100%. At a carbon yield of 100%, all of the carbon from the precursor is found in the condensed phase, with yields below 100% indicating that some carbon is still in the gas phase. This limit gives the yield of condensable carbon for a given precursor, and thereby the branching between pathways yielding condensable versus strictly gas-phase products. Experiments have been performed in which the Coa is systematically increased in order to approach this limit for various precursors. The precursors have been chosen across a variety of parent vapor pressures and structures, allowing the influence of these properties on the limiting yield to be assessed. The influence of ';trapping,' wherein products that are primarily condensed see their overall reaction rate decreased is also discussed. The primary effect of trapping on these experiments is that as Coa is increased, more volatile components are trapped in the condensed phase, leading to overall less oxidized and younger generation aerosol. The chemistry of the organic aerosol is evaluated using aerosol mass spectrometry, enabling the oxygen to carbon

  13. simpleGAMMA v1.0 - a reduced model of secondary organic aerosol formation in the aqueous aerosol phase (aaSOA)

    NASA Astrophysics Data System (ADS)

    Woo, J. L.; McNeill, V. F.

    2015-06-01

    There is increasing evidence that the uptake and aqueous processing of water-soluble volatile organic compounds (VOCs) by wet aerosols or cloud droplets is an important source of secondary organic aerosol (SOA). We recently developed GAMMA (Gas-Aerosol Model for Mechanism Analysis), a zero-dimensional kinetic model that couples gas-phase and detailed aqueous-phase atmospheric chemistry for speciated prediction of SOA and organosulfate formation in cloud water or aqueous aerosols. Results from GAMMA simulations of SOA formation in aerosol water (aaSOA) (McNeill et al., 2012) indicate that it is dominated by two pathways: isoprene epoxydiol (IEPOX) uptake followed by ring-opening chemistry (under low-NOx conditions) and glyoxal uptake. This suggested that it is possible to model the majority of aaSOA mass using a highly simplified reaction scheme. We have therefore developed a reduced version of GAMMA, simpleGAMMA. Close agreement in predicted aaSOA mass is observed between simpleGAMMA and GAMMA under all conditions tested (between pH 1-4 and RH 40-80 %) after 12 h of simulation. simpleGAMMA is computationally efficient and suitable for coupling with larger-scale atmospheric chemistry models or analyzing ambient measurement data.

  14. Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

    NASA Astrophysics Data System (ADS)

    Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

    2011-12-01

    Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the

  15. Global Transformation and Fate of Secondary Organic Aerosols: Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions

    NASA Astrophysics Data System (ADS)

    Shrivastava, M. B.; Easter, R. C.; Liu, X.; Zelenyuk, A.; Singh, B.; Zhang, K.; Ma, P. L.; Chand, D.; Ghan, S. J.; Jimenez, J. L.; Zhang, Q.; Fast, J. D.; Rasch, P. J.; Tiitta, P.

    2014-12-01

    Secondary organic aerosols (SOA) are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semi-volatile versus non-volatile SOA treatments (based on some of the latest experimental findings) and also investigate the effects of gas-phase fragmentation reactions. For semi-volatile SOA treatments, fragmentation reactions decrease simulated SOA burden from 7.5 Tg to 1.8 Tg. For the non-volatile SOA treatment (with fragmentation), the burden is 3.1 Tg. Larger differences between non-volatile and semi-volatile SOA (upto a factor of 5) correspond to continental outflow over the oceans. Compared to a global dataset of surface Aerosol Mass Spectrometer measurements and the US IMPROVE network measurements, the non-volatile SOA with fragmentation treatment (FragNVSOA) agrees best at rural locations. Urban SOA is under-predicted but this may be due to the coarse model resolution. Our revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the N. American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is due to treating SOA precursor gases from biomass burning, and long-range transport of biomass burning OA at elevated levels (also supported by satellite data), which undergoes less wet removal compared to the surface OA sources in the standard CAM5. Although the total simulated OA from biomass burning agrees better with aircraft measurements, recent field observations typically report lower SOA formation, suggesting that constraining the POA-SOA split from biomass burning should be the focus of future studies. The non-volatile and semi-volatile configurations predict the direct radiative forcing of SOA as -0.5 W m-2 and -0.26 W m-2 respectively, at top of the atmosphere, which are higher than previously estimated by most models, but in reasonable agreement with

  16. Elucidating the Chemical Complexity of Organic Aerosol Constituents Measured During the Southeastern Oxidant and Aerosol Study (SOAS)

    NASA Astrophysics Data System (ADS)

    Yee, L.; Isaacman, G. A.; Spielman, S. R.; Worton, D. R.; Zhang, H.; Kreisberg, N. M.; Wilson, K. R.; Hering, S. V.; Goldstein, A. H.

    2013-12-01

    Thousands of volatile organic compounds are uniquely created in the atmosphere, many of which undergo chemical transformations that result in more highly-oxidized and often lower vapor pressure species. These species can contribute to secondary organic aerosol, a complex mixture of organic compounds that is still not chemically well-resolved. Organic aerosol collected on filters taken during the Southeastern Oxidant and Aerosol Study (SOAS) constitute hundreds of unique chemical compounds. Some of these include known anthropogenic and biogenic tracers characterized using standardized analytical techniques (e.g. GC-MS, UPLC, LC-MS), but the majority of the chemical diversity has yet to be explored. By employing analytical techniques involving sample derivatization and comprehensive two-dimensional gas chromatography (GC x GC) with high-resolution-time-of-flight mass spectrometry (HR-ToF-MS), we elucidate the chemical complexity of the organic aerosol matrix along the volatility and polarity grids. Further, by utilizing both electron impact (EI) and novel soft vacuum ultraviolet (VUV) ionization mass spectrometry, a greater fraction of the organic mass is fully speciated. The GC x GC-HR-ToF-MS with EI/VUV technique efficiently provides an unprecedented level of speciation for complex ambient samples. We present an extensive chemical characterization and quantification of organic species that goes beyond typical atmospheric tracers in the SOAS samples. We further demonstrate that complex organic mixtures can be chemically deconvoluted by elucidation of chemical formulae, volatility, functionality, and polarity. These parameters provide insight into the sources (anthropogenic vs. biogenic), chemical processes (oxidation pathways), and environmental factors (temperature, humidity), controlling organic aerosol growth in the Southeastern United States.

  17. Transitions from functionalization to fragmentation reactions of laboratory secondary organic aerosol (SOA) generated from the OH oxidation of alkane precursors.

    PubMed

    Lambe, Andrew T; Onasch, Timothy B; Croasdale, David R; Wright, Justin P; Martin, Alexander T; Franklin, Jonathan P; Massoli, Paola; Kroll, Jesse H; Canagaratna, Manjula R; Brune, William H; Worsnop, Douglas R; Davidovits, Paul

    2012-05-15

    Functionalization (oxygen addition) and fragmentation (carbon loss) reactions governing secondary organic aerosol (SOA) formation from the OH oxidation of alkane precursors were studied in a flow reactor in the absence of NO(x). SOA precursors were n-decane (n-C10), n-pentadecane (n-C15), n-heptadecane (n-C17), tricyclo[5.2.1.0(2,6)]decane (JP-10), and vapors of diesel fuel and Southern Louisiana crude oil. Aerosol mass spectra were measured with a high-resolution time-of-flight aerosol mass spectrometer, from which normalized SOA yields, hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios, and C(x)H(y)+, C(x)H(y)O+, and C(x)H(y)O(2)+ ion abundances were extracted as a function of OH exposure. Normalized SOA yield curves exhibited an increase followed by a decrease as a function of OH exposure, with maximum yields at O/C ratios ranging from 0.29 to 0.74. The decrease in SOA yield correlates with an increase in oxygen content and decrease in carbon content, consistent with transitions from functionalization to fragmentation. For a subset of alkane precursors (n-C10, n-C15, and JP-10), maximum SOA yields were estimated to be 0.39, 0.69, and 1.1. In addition, maximum SOA yields correspond with a maximum in the C(x)H(y)O+ relative abundance. Measured correlations between OH exposure, O/C ratio, and H/C ratio may enable identification of alkane precursor contributions to ambient SOA.

  18. Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2-Methyl-3-Buten-2 ol (MBO) in the Atmosphere

    EPA Science Inventory

    2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was exa...

  19. Secondary Organic Aerosol Formation and Aging in a Flow Reactor in the Forested Southeast US during SOAS

    NASA Astrophysics Data System (ADS)

    Hu, W.; Palm, B. B.; Hacker, L.; Campuzano Jost, P.; Day, D. A.; Simoes de Sa, S.; Fry, J.; Ayres, B. R.; Draper, D. C.; Ortega, A. M.; Kiendler-Scharr, A.; Panujoka, A.; Virtanen, A.; Miettinen, P.; Krechmer, J.; Canagaratna, M. R.; Thompson, S.; Yatavelli, L. R.; Stark, H.; Worsnop, D. R.; Lechner, M.; Martin, S. T.; Farmer, D.; Brown, S. S.; Jimenez, J. L.

    2013-12-01

    A major field campaign (Southern Oxidant and Aerosol Study, SOAS) was conducted in summer 2013 in a forested area (Centreville Supersite) in the southeast U.S. To investigate secondary organic aerosol (SOA) formation from biogenic volatile organic compounds (BVOCs), 3 flow reactors (potential aerosol mass, PAM) were used to expose ambient air to oxidants and their output was analyzed by state-of-art gas and aerosol instruments including a High-Resolution Aerosol Mass Spectrometer (HR-AMS), a High-Resolution Proton-Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-TOFMS), and for the first time, two different High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometers (HRToF-CIMS), and an SMPS. Ambient air was exposed 24/7 to variable concentrations of each of the 3 main atmospheric oxidants (OH, O3 and NO3) to investigate SOA formation and aging. The OH exposure was estimated by 3 different methods (empirical parameterization, carbon monoxide consumption, and chemical box model). Effective OH exposures up to 7e12 molec cm-3 s were achieved, which is equivalent to over a month of aging in the atmosphere. High SOA formation of up to 12 μg m-3 above ambient concentrations of 5 μg m-3 was observed under intermediate OH exposures, while very high OH exposures led to destruction of ambient OA by ≈ 30%, indicating shifting contributions of functionalization vs. fragmentation, which is similar to previous results from urban and terpene-dominated environments. The highest SOA enhancements were 3-4 times higher than the ambient OA. More SOA is typically formed during nighttime when terpenes are higher and lower during daytime when isoprene is higher. SOA formation is also observed after exposure of ambient air to O3 or NO3, although the amount and oxidation was lower than for OH exposure. Formation of organic nitrates in the NO3 reaction will be discussed. High SOA formation (above 40 μg m-3) and a large number of CIMS ions, indicating many different

  20. Potential Aerosol Mass (PAM) flow reactor measurements of SOA formation in a Ponderosa Pine forest in the southern Rocky Mountains during BEACHON-RoMBAS

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Ortega, A. M.; Campuzano Jost, P.; Day, D. A.; Kaser, L.; Karl, T.; Jud, W.; Hansel, A.; Fry, J.; Brown, S. S.; Zarzana, K. J.; Dube, W. P.; Wagner, N.; Draper, D.; Brune, W. H.; Jimenez, J. L.

    2012-12-01

    A Potential Aerosol Mass (PAM) photooxidation flow reactor was used in combination with an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer to characterize biogenic secondary organic aerosol (SOA) formation in a terpene-dominated forest during the July-August 2011 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS) field campaign at the U.S. Forest Service Manitou Forest Observatory, Colorado, as well as in corresponding laboratory experiments. In the PAM reactor, a chosen oxidant (OH, O3, or NO3) was generated and controlled over a range of values up to 10,000 times ambient levels. High oxidant concentrations accelerated the gas-phase, heterogeneous, and possibly aqueous oxidative aging of volatile organic compounds (VOCs), inorganic gases, and existing aerosol, which led to repartitioning into the aerosol phase. PAM oxidative processing represented from a few hours up to ~20 days of equivalent atmospheric aging during the ~3 minute reactor residence time. During BEACHON-RoMBAS, PAM photooxidation enhanced SOA at intermediate OH exposure (1-10 equivalent days) but resulted in net loss of OA at long OH exposure (10-20 equivalent days), demonstrating the competing effects of functionalization vs. fragmentation (and possibly photolysis) as aging increased. PAM oxidation also resulted in f44 vs. f43 and Van Krevelen diagram (H/C vs. O/C) slopes similar to ambient oxidation, suggesting the PAM reactor employs oxidation pathways similar to ambient air. Single precursor aerosol yields were measured using the PAM reactor in the laboratory as a function of organic aerosol concentration and reacted hydrocarbon amounts. When applying the laboratory PAM yields with complete consumption of the most abundant VOCs measured at the forest site (monoterpenes, sesquiterpenes, MBO, and toluene), a simple model underpredicted the amount of SOA formed in the PAM reactor in the

  1. Examining the Effects of Anthropogenic Emissions on Isoprene-Derived Secondary Organic Aerosol Formation During the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee, Ground Site

    EPA Science Inventory

    A suite of offline and real-time gas- and particle-phase measurements was deployed atLook Rock, Tennessee (TN), during the 2013 Southern Oxidant and Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formatio...

  2. Indoor transient SOA formation from ozone + α-pinene reactions: Impacts of air exchange and initial product concentrations, and comparison to limonene ozonolysis

    NASA Astrophysics Data System (ADS)

    Youssefi, Somayeh; Waring, Michael S.

    2015-07-01

    The ozonolysis of reactive organic gases (ROG), e.g. terpenes, generates secondary organic aerosol (SOA) indoors. The SOA formation strength of such reactions is parameterized by the aerosol mass fraction (AMF), a.k.a. SOA yield, which is the mass ratio of generated SOA to oxidized ROG. AMFs vary in magnitude both among and for individual ROGs. Here, we quantified dynamic SOA formation from the ozonolysis of α-pinene with 'transient AMFs,' which describe SOA formation due to pulse emission of a ROG in an indoor space with air exchange, as is common when consumer products are intermittently used in ventilated buildings. We performed 19 experiments at low, moderate, and high (0.30, 0.52, and 0.94 h-1, respectively) air exchange rates (AER) at varying concentrations of initial reactants. Transient AMFs as a function of peak SOA concentrations ranged from 0.071 to 0.25, and they tended to increase as the AER and product of the initial reactant concentrations increased. Compared to our similar research on limonene ozonolysis (Youssefi and Waring, 2014), for which formation strength was driven by secondary ozone reactions, the AER impact for α-pinene was opposite in direction and weaker, while the initial reactant product impact was in the same direction but stronger for α-pinene than for limonene. Linear fits of AMFs for α-pinene ozonolysis as a function of the AER and initial reactant concentrations are provided so that future indoor models can predict SOA formation strength.

  3. Influence of humidity, temperature, and radicals on the formation and thermal properties of secondary organic aerosol (SOA) from ozonolysis of β-pinene.

    PubMed

    Emanuelsson, Eva U; Watne, Ågot K; Lutz, Anna; Ljungström, Evert; Hallquist, Mattias

    2013-10-10

    The influence of water and radicals on SOAs produced by β-pinene ozonolysis was investigated at 298 and 288 K using a laminar flow reactor. A volatility tandem differential mobility analyzer (VTDMA) was used to measure the evaporation of the SOA, enabling the parametrization of its volatility properties. The parameters extracted included the temperature at which 50% of the aerosol had evaporated (T(VFR0.5)) and the slope factor (S(VFR)). An increase in S(VFR) indicates a broader distribution of vapor pressures for the aerosol constituents. Reducing the reaction temperature increased S(VFR) and decreased T(VFR0.5) under humid conditions but had less effect on T(VFR0.5) under dry conditions. In general, higher water concentrations gave lower T(VFR0.5) values, more negative S(VFR) values, and a reduction in total SOA production. The radical conditions were changed by introducing OH scavengers to generate systems with and without OH radicals and with different [HO2]/[RO2] ratios. The presence of a scavenger and lower [HO2]/[RO2] ratio reduced SOA production. Observed changes in S(VFR) values could be linked to the more complex chemistry that occurs in the absence of a scavenger and indicated that additional HO2 chemistry gives products with a wider range of vapor pressures. Updates to existing ozonolysis mechanisms with routes that describe the observed responses to water and radical conditions for monoterpenes with endocyclic and exocyclic double bonds are discussed.

  4. [Numerical modeling analysis of secondary organic aerosol (SOA) combined with the ground-based measurements in the Pearl River Delta region].

    PubMed

    Guo, Xiao-Shuang; Situ, Shu-Ping; Wang, Xue-Mei; Ding, Xiang; Wang, Xin-Ming; Yan, Cai-Qing; Li, Xiao-Ying; Zheng, Mei

    2014-05-01

    Two simulations were conducted with different secondary organic aerosol (SOA) methods-VBS (volatile basis set) approach and SORGAM (secondary organic aerosol model) , which have been coupled in the WRF/Chem (weather research and forecasting model with chemistry) model. Ground-based observation data from 18th to 25th November 2008 were used to examine the model performance of SOA in the Pearl River Delta(PRD)region. The results showed that VBS approach could better reproduce the temporal variation and magnitude of SOA compared with SORGAM, and the mean absolute deviation and correlation coefficient between the observed and the simulated data using VBS approach were -4.88 microg m-3 and 0.91, respectively, while they were -5.32 microg.m-3 and 0. 18 with SORGAM. This is mainly because the VBS approach considers SOA precursors with a wider volatility range and the process of chemical aging in SOA formation. Spatiotemporal distribution of SOA in the PRD from the VBS simulation was also analyzed. The results indicated that the SOA has a significant diurnal variation, and the maximal SOA concentration occurred at noon and in the early afternoon. Because of the transport and the considerable spatial distribution of O3 , the SOA concentrations were different in different PRD cities, and the highest concentration of SOA was observed in the downwind area, including Zhongshan, Zhuhai and Jiangmen.

  5. Experimental determination of the partitioning coefficient of β-pinene oxidation products in SOAs.

    PubMed

    Hohaus, Thorsten; Gensch, Iulia; Kimmel, Joel; Worsnop, Douglas R; Kiendler-Scharr, Astrid

    2015-06-14

    The composition of secondary organic aerosols (SOAs) formed by β-pinene ozonolysis was experimentally investigated in the Juelich aerosol chamber. Partitioning of oxidation products between gas and particles was measured through concurrent concentration measurements in both phases. Partitioning coefficients (Kp) of 2.23 × 10(-5) ± 3.20 × 10(-6) m(3) μg(-1) for nopinone, 4.86 × 10(-4) ± 1.80 × 10(-4) m(3) μg(-1) for apoverbenone, 6.84 × 10(-4) ± 1.52 × 10(-4) m(3) μg(-1) for oxonopinone and 2.00 × 10(-3) ± 1.13 × 10(-3) m(3) μg(-1) for hydroxynopinone were derived, showing higher values for more oxygenated species. The observed Kp values were compared with values predicted using two different semi-empirical approaches. Both methods led to an underestimation of the partitioning coefficients with systematic differences between the methods. Assuming that the deviation between the experiment and the model is due to non-ideality of the mixed solution in particles, activity coefficients of 4.82 × 10(-2) for nopinone, 2.17 × 10(-3) for apoverbenone, 3.09 × 10(-1) for oxonopinone and 7.74 × 10(-1) for hydroxynopinone would result using the vapour pressure estimation technique that leads to higher Kp. We discuss that such large non-ideality for nopinone could arise due to particle phase processes lowering the effective nopinone vapour pressure such as diol- or dimer formation. The observed high partitioning coefficients compared to modelled results imply an underestimation of SOA mass by applying equilibrium conditions.

  6. Aqueous Secondary Organic Aerosol (aqSOA) Formation By Radical Reactions: Model Studies Comparing the Role of OH Versus Organic Radicals

    NASA Astrophysics Data System (ADS)

    Ervens, B.; Renard, P.; Reed Harris, A.; Vaida, V.; Monod, A.

    2014-12-01

    Chemical reactions in the aqueous phase are thought to significantly contribute to ambient aerosol mass under specific conditions. Results from many laboratory studies suggest that these reactions are efficiently initiated by the OH radical and lead to high molecular weight compounds (oligomers). Recent laboratory experiments have shown that methyl vinyl ketone (MVK) can form oligomers in high yield in aqueous solutions similar to aerosol water. Additional experiments have shown that the direct photolysis of pyruvic acid can generate organic radicals that initiate similar oligomer products upon oxidation of MVK (Renard et al., submitted). Sources of the OH radical in the aerosol aqueous phase include the direct uptake from the gas phase, Fenton reactions and, to a smaller extent, direct photolyses of hydrogen peroxide and nitrate. Recent model studies imply that under many conditions, aqSOA formation might be oxidant-limited since these OH(aq) sources are not sufficient to provide a continuous OH supply. This limitation can be (partially) removed if additional radical sources in the multiphase system are considered. Exemplary, we include the direct photolysis of aqueous pyruvic acid as a proxy for possible other radical sources. Model results will be shown and consequences for aqSOA formation and processing under ambient conditions will be discussed.

  7. Formation and evolution of molecular products in α-pinene secondary organic aerosol.

    PubMed

    Zhang, Xuan; McVay, Renee C; Huang, Dan D; Dalleska, Nathan F; Aumont, Bernard; Flagan, Richard C; Seinfeld, John H

    2015-11-17

    Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58-72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA.

  8. Formation and evolution of molecular products in α-pinene secondary organic aerosol

    PubMed Central

    Zhang, Xuan; McVay, Renee C.; Huang, Dan D.; Dalleska, Nathan F.; Aumont, Bernard; Flagan, Richard C.; Seinfeld, John H.

    2015-01-01

    Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58–72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA. PMID:26578760

  9. Secondary organic aerosol (SOA) derived from isoprene epoxydiols: Insights into formation, aging and distribution over the continental US from the DC3 and SEAC4RS campaigns

    NASA Astrophysics Data System (ADS)

    Campuzano Jost, P.; Palm, B. B.; Day, D. A.; Hu, W.; Ortega, A. M.; Jimenez, J. L.; Liao, J.; Froyd, K. D.; Pollack, I. B.; Peischl, J.; Ryerson, T. B.; St Clair, J. M.; Crounse, J.; Wennberg, P. O.; Mikoviny, T.; Wisthaler, A.; Ziemba, L. D.; Anderson, B. E.

    2014-12-01

    Isoprene-derived SOA formation has been studied extensively in the laboratory. However, it is still unclear to what extent isoprene contributes to the overall SOA burden over the southeastern US, an area with both strong isoprene emissions as well as large discrepancies between modeled and observed aerosol optical depth. For the low-NO isoprene oxidation pathway, the key gas-phase intermediate is believed to be isoprene epoxide (IEPOX), which can be incorporated into the aerosol phase by either sulfate ester formation (IEPOX sulfate) or direct hydrolysis. As first suggested by Robinson et al, the SOA formed by this mechanism (IEPOX-SOA) has a characteristic fragmentation pattern when analyzed by an Aerodyne Aerosol Mass Spectrometer (AMS) with enhanced relative abundances of the C5H6O+ ion (fC5H6O). Based on data from previous ground campaigns and chamber studies, we have developed a empirical method to quantify IEPOX-SOA and have applied it to the data from the DC3 and SEAC4RS aircraft campaigns that sampled the SE US during the Spring of 2012 and the Summer of 2013. We used Positive Matrix Factorization (PMF) to extract IEPOX-SOA factors that show good correlation with inside or downwind of high isoprene emitting areas and in general agree well with the IEPOX-SOA mass predicted by the empirical expression. According to this analysis, the empirical method performs well regardless of (at times very strong) BBOA or urban OA influences. On average 17% of SOA in the SE US boundary layer was IEPOX-SOA. Overall, the highest concentrations of IEPOX-SOA were typically found around 1-2 km AGL, several hours downwind of the isoprene source areas with high gas-phase IEPOX present. IEPOX-SOA was also detected up to altitudes of 6 km, with a clear trend towards more aged aerosol at altitude, likely a combination of chemical aging and physical airmass mixing. The unique instrument package aboard the NASA-DC8 allows us to examine the influence of multiple factors (aerosol

  10. Aqueous-phase oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Product identification from methyl jasmonate and methyl salicylate oxidation

    NASA Astrophysics Data System (ADS)

    Hansel, Amie K.; Ehrenhauser, Franz S.; Richards-Henderson, Nicole K.; Anastasio, Cort; Valsaraj, Kalliat T.

    2015-02-01

    Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.

  11. Linking Load, Fuel, and Emission Controls to Photochemical Production of Secondary Organic Aerosol from a Diesel Engine.

    PubMed

    Jathar, Shantanu H; Friedman, Beth; Galang, Abril A; Link, Michael F; Brophy, Patrick; Volckens, John; Eluri, Sailaja; Farmer, Delphine K

    2017-02-07

    Diesel engines are important sources of fine particle pollution in urban environments, but their contribution to the atmospheric formation of secondary organic aerosol (SOA) is not well constrained. We investigated direct emissions of primary organic aerosol (POA) and photochemical production of SOA from a diesel engine using an oxidation flow reactor (OFR). In less than a day of simulated atmospheric aging, SOA production exceeded POA emissions by an order of magnitude or more. Efficient combustion at higher engine loads coupled to the removal of SOA precursors and particle emissions by aftertreatment systems reduced POA emission factors by an order of magnitude and SOA production factors by factors of 2-10. The only exception was that the retrofitted aftertreatment did not reduce SOA production at idle loads where exhaust temperatures were low enough to limit removal of SOA precursors in the oxidation catalyst. Use of biodiesel resulted in nearly identical POA and SOA compared to diesel. The effective SOA yield of diesel exhaust was similar to that of unburned diesel fuel. While OFRs can help study the multiday evolution, at low particle concentrations OFRs may not allow for complete gas/particle partitioning and bias the potential of precursors to form SOA.

  12. Experimental determination of partition coefficient for β-pinene ozonolysis products in SOA

    NASA Astrophysics Data System (ADS)

    Gensch, Iulia; Hohaus, Thorsten; Kimmel, Joel; Jayne, John T.; Worsnop, Douglas R.; Kiendler-Scharr, Astrid

    2013-04-01

    In the present study, simultaneous measurement of β-pinene ozonolysis products in the gas phase by Proton Transfer Reaction - Time of Flight Mass Spectrometry (PTR-ToFMS) and particle phase by using an Aerosol Collection Module coupled to a Gas Chromatograph - Mass Spectrometer (ACM-GC-MS) were employed to determine the equilibrium partitioning coefficient (Kp) of several semi-volatile organic species. Mean Kp values of 6.7 10-5 ± 2.5 10-5 for nopinone, 4.8 10-4 ± 1.7 10-4 for apoverbenone, 7.0 10-4 ± 1.7 10-4 for oxonopinone and 1.9 10-3 ± 1.1 10-3 for hydroxynopinone were obtained. The results were compared with calculations arising from studies on the gas-particle partitioning, based on the Pankow absorption model. The experimental partition coefficients are two to three orders of magnitudes higher than the calculated values, leading to the conclusion that the amount of semi-volatile organic compounds in secondary organic aerosol (SOA) is currently underestimated by the theory, thus impacting on the modeling of the organic matter in the atmosphere.

  13. Cloud Condensation Nuclei Activity, Droplet Growth Kinetics and Hygroscopicity of Biogenic and Anthropogenic Secondary Organic Aerosol (SOA)

    NASA Astrophysics Data System (ADS)

    Zhao, Defeng; Buchholz, Angela; Kortner, Birthe; Schlag, Patrick; Rubach, Florian; Hendrik, Fucks; Kiendler-Scharr, Astrid; Tillmann, Ralf; Wahner, Andreas; Hallquist, Mattias; Flores, Michel; Rudich, Yinon; Glasius, Marianne; Kourtchev, Ivan; Kalberer, Markus; Mentel, Thomas

    2015-04-01

    Recent field data and model analysis show that secondary organic aerosol (SOA) formation is enhanced under anthropogenic influences (de Gouw et al. 2005, Spracklen et al. 2011). The interaction of biogenic VOCs (BVOCs) with anthropogenic emissions such as anthropogenic VOCs (AVOCs) could change the particle formation yields and the aerosol properties, as was recently demonstrated (Emanuelsson et al., 2013; Flores et al., 2014). However, the effect of the interaction of BVOCs with AVOCs on cloud condensation nuclei (CCN) activity and hygroscopicity of SOA remains elusive. Characterizing such changes is necessary in order to assess the indirect radiative forcing of biogenic aerosols that form under anthropogenic influence. In this study, we investigated the influence of AVOCs on CCN activation and hygroscopic growth of BSOA. SOA was formed from photooxidation of monoterpenes and aromatics as representatives of BVOCs and AVOCs, respectively. The hygroscopicity and CCN activation of BSOA were studied and compared with that of anthropogenic SOA (ASOA) and the mixture of ASOA and BSOA (ABSOA). We found that ASOA had a significantly higher hygroscopicity than BSOA at similar OH dose, which is attributed to a higher oxidation level of ASOA. While the ASOA fraction had an enhancing effect on the hygroscopicity of ABSOA compared to BSOA, the hygroscopicity of ABSOA cannot be explained by a linear combination of the pure ASOA and BSOA systems, indicating potentially additional non-linear effects such as oligomerization. However, in contrast to hygroscopicity, ASOA showed similar CCN activity as BSOA, in spite of its higher oxidation level. The ASOA fraction did not enhance the CCN activity of ABSOA. The discrepancy between hygroscopicity and CCN activity is discussed. In addition, BSOA, ABSOA and ASOA formed similar droplet size with ammonium sulfate in CCN at a given supersaturation, indicating none of these aerosols had a delay in the water uptake in the supersaturated

  14. Characterization of particulate products for aging of ethylbenzene secondary organic aerosol in the presence of ammonium sulfate seed aerosol.

    PubMed

    Huang, Mingqiang; Zhang, Jiahui; Cai, Shunyou; Liao, Yingmin; Zhao, Weixiong; Hu, Changjin; Gu, Xuejun; Fang, Li; Zhang, Weijun

    2016-09-01

    Aging of secondary organic aerosol (SOA) particles formed from OH- initiated oxidation of ethylbenzene in the presence of high mass (100-300μg/m(3)) concentrations of (NH4)2SO4 seed aerosol was investigated in a home-made smog chamber in this study. The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with a Fuzzy C-Means (FCM) clustering algorithm. Experimental results showed that nitrophenol, ethyl-nitrophenol, 2,4-dinitrophenol, methyl glyoxylic acid, 5-ethyl-6-oxo-2,4-hexadienoic acid, 2-ethyl-2,4-hexadiendioic acid, 2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid, 1H-imidazole, hydrated N-glyoxal substituted 1H-imidazole, hydrated glyoxal dimer substituted imidazole, 1H-imidazole-2-carbaldehyde, N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight (HMW) components were the predominant products in the aged particles. Compared to the previous aromatic SOA aging studies, imidazole compounds, which can absorb solar radiation effectively, were newly detected in aged ethylbenzene SOA in the presence of high concentrations of (NH4)2SO4 seed aerosol. These findings provide new information for discussing aromatic SOA aging mechanisms.

  15. Secondary Organic Aerosol Production from Cloud Processing of Glycolaldehyde

    NASA Astrophysics Data System (ADS)

    Perri, M. J.; Seitzinger, S.; Turpin, B. J.

    2008-12-01

    Organic particulate matter (PM) formed in the atmosphere (secondary organic aerosol; SOA) is a substantial yet poorly understood contributor to atmospheric PM. Cloud processing is a newly recognized SOA formation pathway. This study investigates the potential for aqueous glycolaldehyde oxidation to produce low volatility products that are retained in the particle phase upon cloud droplet evaporation, increasing PM concentrations aloft. To our knowledge, this is the first confirmation that aqueous oxidation of glycolaldehyde via the hydroxyl radical forms glyoxal and glycolic acid, as previously assumed. Subsequent reactions form formic acid, glyoxylic acid, and oxalic acid as expected. Unexpected products include malonic acid, succinic acid, and higher molecular weight compounds, including oligomers. Predictions of aerosol yields based on these bulk aqueous experiments are presented. Due to (1) the large source strength of glycolaldehyde from precursors such as isoprene and ethene, (2) its water solubility, and (3) the aqueous formation of low volatility products, we predict that cloud processing of glycolaldehyde is an important source of SOA and that incorporation of this SOA formation pathway in chemical transport models will help explain the current under- prediction of organic PM concentrations.

  16. Secondary organic aerosol production from diesel vehicle exhaust: impact of aftertreatment, fuel chemistry and driving cycle

    NASA Astrophysics Data System (ADS)

    Gordon, T. D.; Presto, A. A.; Nguyen, N. T.; Robertson, W. H.; Na, K.; Sahay, K. N.; Zhang, M.; Maddox, C.; Rieger, P.; Chattopadhyay, S.; Maldonado, H.; Maricq, M. M.; Robinson, A. L.

    2014-05-01

    Environmental chamber ("smog chamber") experiments were conducted to investigate secondary organic aerosol (SOA) production from dilute emissions from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel vehicles (HDDVs) under urban-like conditions. Some of the vehicles were equipped with emission control aftertreatment devices, including diesel particulate filters (DPFs), selective catalytic reduction (SCR) and diesel oxidation catalysts (DOCs). Experiments were also performed with different fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur diesel) and driving cycles (Unified Cycle,~Urban Dynamometer Driving Schedule, and creep + idle). During normal operation, vehicles with a catalyzed DPF emitted very little primary particulate matter (PM). Furthermore, photooxidation of dilute emissions from these vehicles produced essentially no SOA (below detection limit). However, significant primary PM emissions and SOA production were measured during active DPF regeneration experiments. Nevertheless, under reasonable assumptions about DPF regeneration frequency, the contribution of regeneration emissions to the total vehicle emissions is negligible, reducing PM trapping efficiency by less than 2%. Therefore, catalyzed DPFs appear to be very effective in reducing both primary PM emissions and SOA production from diesel vehicles. For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the smog chamber - with the emissions from some vehicles generating twice as much SOA as primary organic aerosol after 3 h of oxidation at typical urban VOC / NOx ratios (3 : 1). Comprehensive organic gas speciation was performed on these emissions, but less than half of the measured SOA could be explained by traditional (speciated) SOA precursors. The remainder presumably originates from the large fraction (~30%) of the nonmethane organic gas emissions that could not be speciated using traditional one-dimensional gas chromatography. The

  17. Improving the simulation of organic aerosols from anthropogenic and burning sources: a simplified SOA formation mechanism and the impact of trash burning

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Wiedinmyer, C.; Jimenez, J. L.

    2011-12-01

    Organic aerosols (OA) are an major component of fine aerosols, but their sources are poorly understood. We present results of two methods to improve OA predictions in anthropogenic pollution and biomass-burning impacted regions. (1) An empirical parameterization for secondary organic aerosol (SOA) formation in polluted air and biomass burning smoke is implemented into community chemistry-transport models (WRF/Chem and CHIMERE) and tested in this work, towards the goal of a computationally inexpensive method to calculate pollution and biomass burning SOA. This approach is based on the observed proportionality of SOA concentrations to excess CO and photochemical age of the airmass, as described in Hodzic and Jimenez (GMDD, 2011). The oxygen to carbon ratio in organic aerosols is also parameterizated vs. photochemical aged based on the ambient observations, and is used to estimate the aerosol hygroscopicity and CCN activity. The predicted SOA is assessed against observations from the Mexico City metropolitan area during the MILAGRO 2006 field experiment, and compared to previous model results using the more complex volatility basis approach (VBS) of Robinson et al.. The results suggest that the simplified approach reproduces the observed average SOA mass within 30% in the urban area and downwind, and gives better results than the original VBS. In addition to being much less computationally expensive than VBS-type methods, the empirical approach can also be used in regions where the emissions of SOA precursors are not yet available. (2) The contribution of trash burning emissions to primary and secondary organic aerosols in Mexico City are estimated, using a recently-developed emission inventory. Submicron antimony (Sb) is used as a garbage-burning tracer following the results of Christian et al. (ACP 2010), which allows evaluation of the emissions inventory. Results suggests that trash burning may be an appreciable source of organic aerosols in the Mexico City

  18. Online Measurements and Modeling of Isoprene Photo-oxidation Products: Insights from the Laboratory and SOAS Field Campaign

    NASA Astrophysics Data System (ADS)

    D'Ambro, E.; Lopez-Hilfiker, F.; Mohr, C.; Gaston, C.; Lee, B. H.; Liu, J.; Lutz, A.; Hallquist, M.; Shilling, J.; Gold, A.; Zhang, Z.; Surratt, J. D.; Thornton, J. A.; Schobesberger, S.

    2015-12-01

    Isoprene, the most abundant non-methane volatile organic compound emitted globally, has the potential to produce large quantities of secondary organic aerosol (SOA) with implications for climate, air quality, and human health. However, much remains unknown about the mechanisms and processes that lead to isoprene derived SOA. We present measurements and modeling of a suite of newly detected compounds from isoprene oxidation from laboratory studies at the Pacific Northwest National Laboratory (PNNL) as well as in the atmosphere from the Southern Oxidant and Aerosol Study (SOAS) field campaign. Measurements were made with a high resolution time of flight chemical ionization mass spectrometer utilizing iodide adduct ionization coupled to the Filter Inlet for Gas and AEROsol (FIGAERO) for the simultaneous sampling of the gas and aerosol phases. In the PNNL chamber, isoprene photo-oxidation with dry neutral seed and IEPOX multiphase chemistry on aqueous particles was investigated at a variety of atmospherically relevant conditions. Isoprene photo-oxidation under high HO2 produced unexpectedly substantial SOA at a yield similar to but from a distinctly different mechanism than that from IEPOX uptake. The high HO2 chemistry also resulted in di hydroxy di hydroperoxides as a dominant component of the aerosol. By utilizing the same instrument and ion chemistry during both field and chamber experiments, together with an MCM-based model, we assess the degree to which the different mechanisms are operable in the atmosphere and relevant aerosol chemical and physical properties of the SOA such as volatility and oligomer content.

  19. Effects of inorganic seed aerosols on the particulate products of aged 1,3,5-trimethylbenzene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Huang, Mingqiang; Hao, Liqing; Cai, Shunyou; Gu, Xuejun; Zhang, Weixiong; Hu, Changjin; Wang, Zhenya; Fang, Li; Zhang, Weijun

    2017-03-01

    Inorganic aerosols such as (NH4)2SO4, NaNO3 and CaCl2 are commonly present in the Chinese urban atmosphere. They could significantly affect the formation and aging of ambient secondary organic aerosols (SOA), but the underlying mechanisms remain unknown. In this work we studied SOA formation from the photooxidation reaction of 1,3,5-trimethylbenzene (135-TMB) with 100 μg/m3 of the above three types of inorganic aerosols as seeds in a laboratory chamber. We focused on the aging products of SOA particles by exposing them to high levels of oxidizing hydroxyl radicals (OH). The particulate products of SOA were measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) and Fuzzy C-Means (FCM) were applied to organic mass spectra for clustering. In the presence of (NH4)2SO4 seeds, 4-methyl-1H-imidazole, 4-methyl-imidazole-2-acetaldehyde and other imidazole derivative compounds formed from reactions of NH4+ with methylglyoxal were detected as new aged products. We also observed aromatic nitrogen-containing organic compounds as the major aged products in the presence of NaNO3 seeds as a consequence of reaction with OH and NO2 radicals, which were generated by UV irradiation of acidic aqueous nitrate, inducing nitration reactions with phenolic compounds. As CaCl2 has the strongest hygroscopic properties of the three salt particles tested, the greater water content on the surface of the aerosol may facilitate the condensing of more gas-phase organic acid products to the hygroscopic CaCl2 seeds, forming H+ ions that catalyze the heterogeneous reaction of aldehydes, products of photooxidation of 135-TMB, and forming high-molecular-weight (HMW) compounds. These results provide new insight into the aromatic SOA aging mechanisms.

  20. In-Situ Measurements of Aerosol Optical and Hygroscopic Properties at the Look Rock Site during SOAS 2013

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zimmermann, K.; Bertram, T. H.; Corrigan, A. L.; Guzman, J. M.; Russell, L. M.; Budisulistiorini, S.; Li, X.; Surratt, J. D.; Hicks, W.; Bairai, S. T.; Cappa, C. D.

    2013-12-01

    One of the main goals of the Southern Oxidant and Aerosol Study (SOAS) is to characterize the climate-relevant properties of aerosols over the southeastern United States at the interface of biogenic and anthropogenic emissions. As part of the SOAS campaign, the UCD cavity ringdown/photoacoustic spectrometer was deployed to make in-situ measurements of aerosol light extinction, absorption and sub-saturated hygroscopicity at the Look Rock site (LRK) in the Great Smoky Mountains National Park, TN from June 1 to July 15, 2013. The site is influenced by substantial biogenic emissions with varying impacts from anthropogenic pollutants, allowing for direct examination of the optical and hygroscopic properties of anthropogenic-influenced biogenic secondary organic aerosols (SOA). During the experiment period, the average dry aerosol extinction (Bext), absorption (Babs) coefficients and single scattering albedo (SSA) at 532 nm were 30.3 × 16.5 Mm-1, 1.12 × 0.78 Mm-1 and 0.96 × 0.06. The Babs at 532 nm was well correlated (r2 = 0.79) with the refractory black carbon (rBC) number concentration determined by a single particle soot spectrometer (SP2). The absorption by black carbon (BC), brown carbon (BrC) and the absorption enhancement due to the 'lensing' effect were quantified by comparing the Babs of ambient and thermo-denuded aerosols at 405 nm and 532 nm. The optical sub-saturated hygroscopic growth factor was derived from extinction and particle size distribution measurements at dry and elevated relative humidity. In addition, to explore the extent to which ammonia mediated chemistry leads to BrC formation, as suggested in recent laboratory studies(1,2), we performed an NH3 perturbation experiment in-situ for 1 week during the study, in which ambient aerosols were exposed to approximately 100 ppb NH3 with a residence time of ~ 3hr. The broader implications of these observational data at LRK will be discussed in the context of the concurrent gas and aerosol chemical

  1. Secondary organic aerosol production from diesel vehicle exhaust: impact of aftertreatment, fuel chemistry and driving cycle

    NASA Astrophysics Data System (ADS)

    Gordon, T. D.; Presto, A. A.; Nguyen, N. T.; Robertson, W. H.; Na, K.; Sahay, K. N.; Zhang, M.; Maddox, C.; Rieger, P.; Chattopadhyay, S.; Maldonado, H.; Maricq, M. M.; Robinson, A. L.

    2013-09-01

    Environmental chamber ("smog chamber") experiments were conducted to investigate secondary organic aerosol (SOA) production from dilute emissions from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel vehicles (HDDVs) under urban-like conditions. Some of the vehicles were equipped with emission control aftertreatment devices including diesel particulate filters (DPF), selective catalytic reduction (SCR) and diesel oxidation catalysts (DOC). Experiments were also performed with different fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur diesel) and driving cycles (Unified Cycle, Urban Dynamometer Driving Schedule, and creep+idle). During normal operation, vehicles with a catalyzed DPF emitted very little primary particulate matter (PM). Furthermore, photo-oxidation of dilute emissions from these vehicles produced essentially no SOA (below detection limit). However, significant primary PM emissions and SOA production were measured during active DPF regeneration experiments. Nevertheless, under reasonable assumptions about DPF regeneration frequency, the contribution of regeneration emissions to the total vehicle emissions is negligible, reducing PM trapping efficiency by less than 2%. Therefore, catalyzed DPFs appear to be very effective in reducing both primary and secondary fine particulate matter from diesel vehicles. For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the smog chamber - with the emissions from some vehicles generating twice as much SOA as primary organic aerosol after three hours of oxidation at typical urban VOC : NOx ratios (3:1). Comprehensive organic gas speciation was performed on these emissions, but less than half of the measured SOA could be explained by traditional (speciated) SOA precursors. The remainder presumably originates from the large fraction (~30%) of the non-methane organic gas emissions that could not be speciated using traditional one-dimensional gas

  2. A Comparison of Parameterizations of Secondary Organic Aerosol Production: Global Budget and Spatiotemporal Variability

    NASA Astrophysics Data System (ADS)

    Liu, J.; Chen, Z.; Horowitz, L. W.; Carlton, A. M. G.; Fan, S.; Cheng, Y.; Ervens, B.; Fu, T. M.; He, C.; Tao, S.

    2014-12-01

    Secondary organic aerosols (SOA) have a profound influence on air quality and climate, but large uncertainties exist in modeling SOA on the global scale. In this study, five SOA parameterization schemes, including a two-product model (TPM), volatility basis-set (VBS) and three cloud SOA schemes (Ervens et al. (2008, 2014), Fu et al. (2008) , and He et al. (2013)), are implemented into the global chemical transport model (MOZART-4). For each scheme, model simulations are conducted with identical boundary and initial conditions. The VBS scheme produces the highest global annual SOA production (close to 35 Tg·y-1), followed by three cloud schemes (26-30 Tg·y-1) and TPM (23 Tg·y-1). Though sharing a similar partitioning theory to the TPM scheme, the VBS approach simulates the chemical aging of multiple generations of VOCs oxidation products, resulting in a much larger SOA source, particularly from aromatic species, over Europe, the Middle East and Eastern America. The formation of SOA in VBS, which represents the net partitioning of semi-volatile organic compounds from vapor to condensed phase, is highly sensitivity to the aging and wet removal processes of vapor-phase organic compounds. The production of SOA from cloud processes (SOAcld) is constrained by the coincidence of liquid cloud water and water-soluble organic compounds. Therefore, all cloud schemes resolve a fairly similar spatial pattern over the tropical and the mid-latitude continents. The spatiotemporal diversity among SOA parameterizations is largely driven by differences in precursor inputs. Therefore, a deeper understanding of the evolution, wet removal, and phase partitioning of semi-volatile organic compounds, particularly above remote land and oceanic areas, is critical to better constrain the global-scale distribution and related climate forcing of secondary organic aerosols.

  3. Reactive oxidation products promote secondary organic aerosol formation from green leaf volatiles

    NASA Astrophysics Data System (ADS)

    Hamilton, J. F.; Lewis, A. C.; Carey, T. J.; Wenger, J. C.; Garcia, E. Borrás. I.; Muñoz, A.

    2009-02-01

    Green leaf volatiles (GLVs) are an important group of chemicals released by vegetation which have emission fluxes that can be significantly increased when plants are damaged or stressed. A series of simulation chamber experiments has been conducted at the European Photoreactor in Valencia, Spain, to investigate secondary organic aerosol (SOA) formation from the atmospheric oxidation of the major GLVs cis-3-hexenylacetate and cis-3-hexen-1-ol. Liquid chromatography-ion trap mass spectrometry was used to identify chemical species present in the SOA. Cis-3-hexen-1-ol proved to be a more efficient SOA precursor due to the high reactivity of its first generation oxidation product, 3-hydroxypropanal, which can hydrate and undergo further reactions with other aldehydes resulting in SOA dominated by higher molecular weight oligomers. The lower SOA yields produced from cis-3-hexenylacetate are attributed to the acetate functionality, which inhibits oligomer formation in the particle phase. Based on observed SOA yields and best estimates of global emissions, these compounds may be calculated to be a substantial unidentified global source of SOA, contributing 1-5 TgC yr-1, equivalent to around a third of that predicted from isoprene. Molecular characterization of the SOA, combined with organic mechanistic information, has provided evidence that the formation of organic aerosols from GLVs is closely related to the reactivity of their first generation atmospheric oxidation products, and indicates that this may be a simple parameter that could be used in assessing the aerosol formation potential for other unstudied organic compounds in the atmosphere.

  4. Reactive oxidation products promote secondary organic aerosol formation from green leaf volatiles

    NASA Astrophysics Data System (ADS)

    Hamilton, J. F.; Lewis, A. C.; Carey, T. J.; Wenger, J. C.; Garcia, E. Borrás. I.; Muñoz, A.

    2009-06-01

    Green leaf volatiles (GLVs) are an important group of chemicals released by vegetation which have emission fluxes that can be significantly increased when plants are damaged or stressed. A series of simulation chamber experiments has been conducted at the European Photoreactor in Valencia, Spain, to investigate secondary organic aerosol (SOA) formation from the atmospheric oxidation of the major GLVs cis-3-hexenylacetate and cis-3-hexen-1-ol. Liquid chromatography-ion trap mass spectrometry was used to identify chemical species present in the SOA. Cis-3-hexen-1-ol proved to be a more efficient SOA precursor due to the high reactivity of its first generation oxidation product, 3-hydroxypropanal, which can hydrate and undergo further reactions with other aldehydes resulting in SOA dominated by higher molecular weight oligomers. The lower SOA yields produced from cis-3-hexenylacetate are attributed to the acetate functionality, which inhibits oligomer formation in the particle phase. Based on observed SOA yields and best estimates of global emissions, these compounds may be calculated to be a substantial unidentified global source of SOA, contributing 1-5 TgC yr-1, equivalent to around a third of that predicted from isoprene. Molecular characterization of the SOA, combined with organic mechanistic information, has provided evidence that the formation of organic aerosols from GLVs is closely related to the reactivity of their first generation atmospheric oxidation products, and indicates that this may be a simple parameter that could be used in assessing the aerosol formation potential for other unstudied organic compounds in the atmosphere.

  5. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    NASA Astrophysics Data System (ADS)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2015-09-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool which explicitly represents SOA formation and gas/wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas/wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up to 0.35 yield unit due to the loss of organic vapors to chamber walls.

  6. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    NASA Astrophysics Data System (ADS)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas-wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas-wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  7. Examining the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol formation during the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee ground site

    NASA Astrophysics Data System (ADS)

    Budisulistiorini, S. H.; Li, X.; Bairai, S. T.; Renfro, J.; Liu, Y.; Liu, Y. J.; McKinney, K. A.; Martin, S. T.; McNeill, V. F.; Pye, H. O. T.; Nenes, A.; Neff, M. E.; Stone, E. A.; Mueller, S.; Knote, C.; Shaw, S. L.; Zhang, Z.; Gold, A.; Surratt, J. D.

    2015-08-01

    A suite of offline and real-time gas- and particle-phase measurements was deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant and Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formation. High- and low-time-resolution PM2.5 samples were collected for analysis of known tracer compounds in isoprene-derived SOA by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography/diode array detection-electrospray ionization-high-resolution quadrupole time-of-flight mass spectrometry (UPLC/DAD-ESI-HR-QTOFMS). Source apportionment of the organic aerosol (OA) was determined by positive matrix factorization (PMF) analysis of mass spectrometric data acquired on an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Campaign average mass concentrations of the sum of quantified isoprene-derived SOA tracers contributed to ~ 9 % (up to 28 %) of the total OA mass, with isoprene-epoxydiol (IEPOX) chemistry accounting for ~ 97 % of the quantified tracers. PMF analysis resolved a factor with a profile similar to the IEPOX-OA factor resolved in an Atlanta study and was therefore designated IEPOX-OA. This factor was strongly correlated (r2 > 0.7) with 2-methyltetrols, C5-alkene triols, IEPOX-derived organosulfates, and dimers of organosulfates, confirming the role of IEPOX chemistry as the source. On average, IEPOX-derived SOA tracer mass was ~ 26 % (up to 49 %) of the IEPOX-OA factor mass, which accounted for 32 % of the total OA. A low-volatility oxygenated organic aerosol (LV-OOA) and an oxidized factor with a profile similar to 91Fac observed in areas where emissions are biogenic-dominated were also resolved by PMF analysis, whereas no primary organic aerosol (POA) sources could be resolved. These findings were consistent with low levels of primary pollutants, such as nitric oxide (NO ~ 0.03 ppb), carbon monoxide (CO ~ 116 ppb), and black

  8. Secondary organic aerosol production from aqueous photooxidation of glycolaldehyde: Laboratory experiments

    NASA Astrophysics Data System (ADS)

    Perri, Mark J.; Seitzinger, Sybil; Turpin, Barbara J.

    Organic particulate matter (PM) formed in the atmosphere (secondary organic aerosol; SOA) is a substantial yet poorly understood contributor to atmospheric PM. Aqueous photooxidation in clouds, fogs and aerosols is a newly recognized SOA formation pathway. This study investigates the potential for aqueous glycolaldehyde oxidation to produce low volatility products that contribute SOA mass. To our knowledge, this is the first confirmation that aqueous oxidation of glycolaldehyde via the hydroxyl radical forms glyoxal and glycolic acid, as previously assumed. Subsequent reactions form formic acid, glyoxylic acid, and oxalic acid as expected. Unexpected products include malonic acid, succinic acid, and higher molecular weight compounds, including oligomers. Due to (1) the large source strength of glycolaldehyde from precursors such as isoprene and ethene, (2) its water solubility, and (3) the aqueous formation of low volatility products (organic acids and oligomers), we predict that aqueous photooxidation of glycolaldehyde and other aldehydes in cloud, fog, and aerosol water is an important source of SOA and that incorporation of this SOA formation pathway in chemical transport models will help explain the current under-prediction of organic PM concentrations.

  9. Kinetics, products, and mechanisms of secondary organic aerosol formation.

    PubMed

    Ziemann, Paul J; Atkinson, Roger

    2012-10-07

    Secondary organic aerosol (SOA) is formed in the atmosphere when volatile organic compounds (VOCs) emitted from anthropogenic and biogenic sources are oxidized by reactions with OH radicals, O(3), NO(3) radicals, or Cl atoms to form less volatile products that subsequently partition into aerosol particles. Once in particles, these organic compounds can undergo heterogenous/multiphase reactions to form more highly oxidized or oligomeric products. SOA comprises a large fraction of atmospheric aerosol mass and can have significant effects on atmospheric chemistry, visibility, human health, and climate. Previous articles have reviewed the kinetics, products, and mechanisms of atmospheric VOC reactions and the general chemistry and physics involved in SOA formation. In this article we present a detailed review of VOC and heterogeneous/multiphase chemistry as they apply to SOA formation, with a focus on the effects of VOC molecular structure on the kinetics of initial reactions with the major atmospheric oxidants, the subsequent reactions of alkyl, alkyl peroxy, and alkoxy radical intermediates, and the composition of the resulting products. Structural features of reactants and products discussed include compound carbon number; linear, branched, and cyclic configurations; the presence of C[double bond, length as m-dash]C bonds and aromatic rings; and functional groups such as carbonyl, hydroxyl, ester, hydroxperoxy, carboxyl, peroxycarboxyl, nitrate, and peroxynitrate. The intention of this review is to provide atmospheric chemists with sufficient information to understand the dominant pathways by which the major classes of atmospheric VOCs react to form SOA products, and the further reactions of these products in particles. This will allow reasonable predictions to be made, based on molecular structure, about the kinetics, products, and mechanisms of VOC and heterogeneous/multiphase reactions, including the effects of important variables such as VOC, oxidant, and NO

  10. Investigation of the Correlation between Odd Oxygen and Secondary Organic Aerosol in Mexico City and Houston

    EPA Science Inventory

    Many recent models underpredict secondary organic aerosol (SOA) particulate matter(PM) concentrations in polluted regions, indicating serious deficiencies in the models' chemical mechanisms and/or missing SOA precursors. Since tropospheric photochemical ozone production is much b...

  11. High-time resolved measurements of biogenic and anthropogenic secondary organic aerosol precursors and products in urban air

    NASA Astrophysics Data System (ADS)

    Flores, Rosa M.; Doskey, Paul V.

    2016-04-01

    Volatile organic compounds (VOCs), which are present in the atmosphere entirely in the gas phase are directly emitted by biogenic (~1089 Tg yr-1) and anthropogenic sources (~185 Tg yr-1). However, the sources and molecular speciation of intermediate VOCs (IVOCs), which are for the most part also present almost entirely in the gas phase, are not well characterized. The VOCs and IVOCs participate in reactions that form ozone and semivolatile OC (SVOC) that partition into the aerosol phase. Formation and evolution of secondary organic aerosol (SOA) are part of a complex dynamic process that depends on the molecular speciation and concentration of VOCs, IVOCs, primary organic aerosol (POA), and the level of oxidants (NO3, OH, O3). The current lack of understanding of OA properties and their impact on radiative forcing, ecosystems, and human health is partly due to limitations of models to predict SOA production on local, regional, and global scales. More accurate forecasting of SOA production requires high-temporal resolution measurement and molecular characterization of SOA precursors and products. For the subject study, the IVOCs and aerosol-phase organic matter were collected using the high-volume sampling technique and were analyzed by multidimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-ToFMS). The IVOCs included terpenes, terpenoids, n-alkanes, branched alkanes, isoprenoids, alkylbenzenes, cycloalkylbenzenes, PAH, alkyl PAH, and an unresolved complex mixture (UCM). Diurnal variations of OA species containing multiple oxygenated functionalities and selected SOA tracers of isorprene, α-pinene, toluene, cyclohexene, and n-dodecane oxidation were also quantified. The data for SOA precursor and oxidation products presented here will be useful for evaluating the ability of molecular-specific SOA models to forecast SOA production in and downwind of urban areas.

  12. Multiday production of condensing organic aerosol mass in urban and forest outflow

    DOE PAGES

    Lee-Taylor, J.; Hodzic, A.; Madronich, S.; ...

    2014-07-03

    Secondary organic aerosol (SOA) production in air masses containing either anthropogenic or biogenic (terpene-dominated) emissions is investigated using the explicit gas-phase chemical mechanism generator GECKO-A. Simulations show several-fold increases in SOA mass continuing for several days in the urban outflow, even as the initial air parcel is diluted into the regional atmosphere. The SOA mass increase in the forest outflow is more modest (∼50%) and of shorter duration (1–2 days). The production in the urban outflow stems from continuing oxidation of gas-phase precursors which persist in equilibrium with the particle phase, and can be attributed to multigenerational reaction products ofmore » both aromatics and alkanes. In particular we find large contributions from substituted maleic anhydrides and multi-substituted peroxide-bicyclic alkenes. The results show that the predicted production is a robust feature of our model even under changing atmospheric conditions, and contradict the notion that SOA undergoes little mass production beyond a short initial formation period. The results imply that anthropogenic aerosol precursors could influence the chemical and radiative characteristics of the atmosphere over an extremely wide region, and that SOA measurements near precursor sources may routinely underestimate this influence.« less

  13. Multiday production of condensing organic aerosol mass in urban and forest outflow

    NASA Astrophysics Data System (ADS)

    Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.; Camredon, M.; Valorso, R.

    2014-07-01

    Secondary organic aerosol (SOA) production in air masses containing either anthropogenic or biogenic (terpene-dominated) emissions is investigated using the explicit gas-phase chemical mechanism generator GECKO-A. Simulations show several-fold increases in SOA mass continuing for several days in the urban outflow, even as the initial air parcel is diluted into the regional atmosphere. The SOA mass increase in the forest outflow is more modest (∼50%) and of shorter duration (1-2 days). The production in the urban outflow stems from continuing oxidation of gas-phase precursors which persist in equilibrium with the particle phase, and can be attributed to multigenerational reaction products of both aromatics and alkanes. In particular we find large contributions from substituted maleic anhydrides and multi-substituted peroxide-bicyclic alkenes. The results show that the predicted production is a robust feature of our model even under changing atmospheric conditions, and contradict the notion that SOA undergoes little mass production beyond a short initial formation period. The results imply that anthropogenic aerosol precursors could influence the chemical and radiative characteristics of the atmosphere over an extremely wide region, and that SOA measurements near precursor sources may routinely underestimate this influence.

  14. Multiday production of condensing organic aerosol mass in urban and forest outflow

    NASA Astrophysics Data System (ADS)

    Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.; Camredon, M.; Valorso, R.

    2015-01-01

    Secondary organic aerosol (SOA) production in air masses containing either anthropogenic or biogenic (terpene-dominated) emissions is investigated using the explicit gas-phase chemical mechanism generator GECKO-A. Simulations show several-fold increases in SOA mass continuing for multiple days in the urban outflow, even as the initial air parcel is diluted into the regional atmosphere. The SOA mass increase in the forest outflow is more modest (~50%) and of shorter duration (1-2 days). The multiday production in the urban outflow stems from continuing oxidation of gas-phase precursors which persist in equilibrium with the particle phase, and can be attributed to multigenerational reaction products of both aromatics and alkanes, especially those with relatively low carbon numbers (C4-15). In particular we find large contributions from substituted maleic anhydrides and multi-substituted peroxide-bicyclic alkenes. The results show that the predicted production is a robust feature of our model even under changing atmospheric conditions and different vapor pressure schemes, and contradict the notion that SOA undergoes little mass production beyond a short initial formation period. The results imply that anthropogenic aerosol precursors could influence the chemical and radiative characteristics of the atmosphere over an extremely wide region, and that SOA measurements near precursor sources may routinely underestimate this influence.

  15. Multiday production of condensing organic aerosol mass in urban and forest outflow

    DOE PAGES

    Lee-Taylor, J.; Hodzic, A.; Madronich, S.; ...

    2015-01-16

    Secondary organic aerosol (SOA) production in air masses containing either anthropogenic or biogenic (terpene-dominated) emissions is investigated using the explicit gas-phase chemical mechanism generator GECKO-A. Simulations show several-fold increases in SOA mass continuing for multiple days in the urban outflow, even as the initial air parcel is diluted into the regional atmosphere. The SOA mass increase in the forest outflow is more modest (~50%) and of shorter duration (1–2 days). The multiday production in the urban outflow stems from continuing oxidation of gas-phase precursors which persist in equilibrium with the particle phase, and can be attributed to multigenerational reaction productsmore » of both aromatics and alkanes, especially those with relatively low carbon numbers (C4–15). In particular we find large contributions from substituted maleic anhydrides and multi-substituted peroxide-bicyclic alkenes. The results show that the predicted production is a robust feature of our model even under changing atmospheric conditions and different vapor pressure schemes, and contradict the notion that SOA undergoes little mass production beyond a short initial formation period. The results imply that anthropogenic aerosol precursors could influence the chemical and radiative characteristics of the atmosphere over an extremely wide region, and that SOA measurements near precursor sources may routinely underestimate this influence.« less

  16. Modeling SOA formation from the oxidation of intermediate volatility n-alkanes

    NASA Astrophysics Data System (ADS)

    Aumont, B.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J.; Madronich, S.

    2012-08-01

    The chemical mechanism leading to SOA formation and ageing is expected to be a multigenerational process, i.e. a successive formation of organic compounds with higher oxidation degree and lower vapor pressure. This process is here investigated with the explicit oxidation model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere). Gas phase oxidation schemes are generated for the C8-C24 series of n-alkanes. Simulations are conducted to explore the time evolution of organic compounds and the behavior of secondary organic aerosol (SOA) formation for various preexisting organic aerosol concentration (COA). As expected, simulation results show that (i) SOA yield increases with the carbon chain length of the parent hydrocarbon, (ii) SOA yield decreases with decreasing COA, (iii) SOA production rates increase with increasing COA and (iv) the number of oxidation steps (i.e. generations) needed to describe SOA formation and evolution grows when COA decreases. The simulated oxidative trajectories are examined in a two dimensional space defined by the mean carbon oxidation state and the volatility. Most SOA contributors are not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA) but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA), suggesting that OOA may underestimate SOA. Results show that the model is unable to produce highly oxygenated aerosols (OOA) with large yields. The limitations of the model are discussed.

  17. Modeling SOA formation from the oxidation of intermediate volatility n-alkanes

    NASA Astrophysics Data System (ADS)

    Aumont, B.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J.; Madronich, S.

    2012-06-01

    The chemical mechanism leading to SOA formation and ageing is expected to be a multigenerational process, i.e. a successive formation of organic compounds with higher oxidation degree and lower vapor pressure. This process is here investigated with the explicit oxidation model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere). Gas phase oxidation schemes are generated for the C8-C24 series of n-alkanes. Simulations are conducted to explore the time evolution of organic compounds and the behavior of secondary organic aerosol (SOA) formation for various preexisting organic aerosol concentration (COA). As expected, simulation results show that (i) SOA yield increases with the carbon chain length of the parent hydrocarbon, (ii) SOA yield decreases with decreasing COA, (iii) SOA production rates increase with increasing COA and (iv) the number of oxidation steps (i.e. generations) needed to describe SOA formation and evolution grows when COA decreases. The simulated oxidative trajectories are examined in a two dimensional space defined by the mean carbon oxidation state and the volatility. Most SOA contributors are not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA) but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA), suggesting that OOA may underestimate SOA. Results show that the model is unable to produce highly oxygenated aerosols (OOA) with large yields. The limitations of the model are discussed.

  18. The use of a housecleaning product in an indoor environment leading to oxygenated polar compounds and SOA formation: Gas and particulate phase chemical characterization

    NASA Astrophysics Data System (ADS)

    Rossignol, S.; Rio, C.; Ustache, A.; Fable, S.; Nicolle, J.; Même, A.; D'Anna, B.; Nicolas, M.; Leoz, E.; Chiappini, L.

    2013-08-01

    This work investigates Secondary Organic Aerosol (SOA) formed by limonene ozonolysis using a housecleaning product in indoor environment. This study combines simulation chamber ozonolysis experiments and field studies in an experimental house allowing different scenarios of housecleaning product use in real conditions. Chemical speciation has been performed using a new method based on simultaneous sampling of both gas and particulate phases on sorbent tubes and filters. This method allowed the identification and quantification of about 35 products in the gas and particulate phases. Among them, products known to be specific from limonene ozonolysis such as limononaldehyde, ketolimonene and ketolimonic acid have been detected. Some other compounds such as 2-methylbutanoic acid had never been detected in previous limonene ozonolysis studies. Some compounds like levulinic acid had already been detected but their formation remained unexplained. Potential reaction pathways are proposed in this study for these compounds. For each experiment, chemical data are coupled together with physical characterization of formed particles: mass and size and number distribution evolution which allowed the observation of new particles formation (about 87,000 particle cm-3). The chemical speciation associated to aerosol size distribution results confirmed that limonene emitted by the housecleaning product was responsible for SOA formation. To our knowledge, this work provides the most comprehensive analytical study of detected compounds in a single experiment for limonene ozonolysis in both gaseous and particulate phases in real indoor environment.

  19. Submicron aerosol organic functional groups, ions, and water content at the Centreville SEARCH site (Alabama), during SOAS campaign

    NASA Astrophysics Data System (ADS)

    Ruggeri, G.; Ergin, G.; Modini, R. L.; Takahama, S.

    2013-12-01

    The SOAS campaign was conducted from June 1 to July 15 of 2013 in order to understand the relationship between biogenic and anthropogenic emissions in the South East US1,2. In this study, the organic and inorganic composition of submicron aerosol in the Centreville SEARCH site was measured by Fourier Transform Infrared Spectroscopy (FTIR) and the Ambient Ion Monitor (AIM; URG Corporation), whereas the aerosol water content was measured with a Dry Ambient Aerosol Size Spectrometer (DAASS)3. Organic functional group analysis was performed on PM1 aerosol selected by cyclone and collected on teflon filters with a time resolution of 4-12 hours, using one inlet heated to 50 °C and the other operated either at ambient temperature or 70 °C 4. The AIM measured both condensed and gas phase composition with a time resolution of 1 hour, providing partitioning behavior of inorganic species such as NH3/NH4+, HNO3/NO3-. These measurements collectively permit calculation of pure-component vapor pressures of candidate organic compounds and activity coefficients of interacting components in the condensed phase, using models such as SIMPOL.15, E-AIM6, and AIOMFAC7. From these results, the water content of the aerosol is predicted, and a comparison between modeled and measured partitioning of inorganic compounds and water vapor are discussed, in addition to organic aerosol volatility prediction based on functional group analysis. [1]- Goldstein, A.H., et al., Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States. Proceedings of the National Academy of Sciences of the United States of America, 2009. 106(22), 8835-8840. [2]- Carlton, A.G., Turpin, B.J., 2013. Particle partitioning potential of organic compounds is highest in the Eastern US and driven by anthropogenic water. Atmospheric Chemistry and Physics Discussions 13, 12743-12770. [3]- Khlystov, A., Stanier, C.O., Takahama, S., Pandis, S.N., 2005. Water content of ambient

  20. Molecular distributions and isotopic compositions of marine aerosols over the western North Atlantic: Dicarboxylic acids, ketoacids, α-dicarbonyls (glyoxal and methylglyoxal), fatty acids, sugars, and SOA tracers

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Ono, K.; Tachibana, E.; Quinn, P.; Bates, T. S.

    2013-12-01

    Marine aerosols were collected over the western North Atlantic from off the coast of Boston to Bermuda during the WACS (Western Atlantic Climate Study) cruise of R/V Ronald H. Brown in August 2012 using a high volume air sampler and pre-combusted quartz fiber filters. Aerosol filter samples (n=5) were analyzed for OC/EC, major inorganic ions, low molecular weight dicarboxylic acids and various secondary organic aerosol (SOA) tracers using carbon analyzer, ion chromatograph, GC/FID and GC/MS, respectively. Homologous series (C2-C12) of dicarboxylic acids (31-335 ng m-3) were detected with a predominance of oxalic acid. Total carbon and nitrogen and their stable isotope ratios were determined as well as stable carbon isotopic compositions of individual diacids using IRMS. Diacids were found to be the most abundant compound class followed by monoterpene-SOA tracers > isoprene-SOA tracers > sugar compounds > ketoacids > fatty alcohols > fatty acids > α-dicarbonyls > aromatic acids > n-alkanes. The concentrations of these compounds were higher in the coastal site and decreased in the open ocean. However, diacids stayed relatively high even in the remote ocean. Interestingly, contributions of oxalic acid to total aerosol carbon increased from the coast (2.3%) to the remote ocean (5.6%) during long-range atmospheric transport. Stable carbon isotopic composition of oxalic acid increased from the coast (-17.5‰) to open ocean (-12.4‰), suggesting that photochemical aging of organic aerosols occurred during the atmospheric transport over the ocean. Stable carbon isotope ratios of bulk aerosol carbon also increased from the coast near Boston to the open ocean near Bermuda.

  1. Evaluation of a quantitative structure-property relationship (QSPR) for predicting mid-visible refractive index of secondary organic aerosol (SOA).

    PubMed

    Redmond, Haley; Thompson, Jonathan E

    2011-04-21

    In this work we describe and evaluate a simple scheme by which the refractive index (λ = 589 nm) of non-absorbing components common to secondary organic aerosols (SOA) may be predicted from molecular formula and density (g cm(-3)). The QSPR approach described is based on three parameters linked to refractive index-molecular polarizability, the ratio of mass density to molecular weight, and degree of unsaturation. After computing these quantities for a training set of 111 compounds common to atmospheric aerosols, multi-linear regression analysis was conducted to establish a quantitative relationship between the parameters and accepted value of refractive index. The resulting quantitative relationship can often estimate refractive index to ±0.01 when averaged across a variety of compound classes. A notable exception is for alcohols for which the model consistently underestimates refractive index. Homogenous internal mixtures can conceivably be addressed through use of either the volume or mole fraction mixing rules commonly used in the aerosol community. Predicted refractive indices reconstructed from chemical composition data presented in the literature generally agree with previous reports of SOA refractive index. Additionally, the predicted refractive indices lie near measured values we report for λ = 532 nm for SOA generated from vapors of α-pinene (R.I. 1.49-1.51) and toluene (R.I. 1.49-1.50). We envision the QSPR method may find use in reconstructing optical scattering of organic aerosols if mass composition data is known. Alternatively, the method described could be incorporated into in models of organic aerosol formation/phase partitioning to better constrain organic aerosol optical properties.

  2. High-Resolution Mass Spectrometry and Molecular Characterization of Aqueous Photochemistry Products of Common Types of Secondary Organic Aerosols

    SciTech Connect

    Romonosky, Dian E.; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey

    2015-03-19

    A significant fraction of atmospheric organic compounds is predominantly found in condensed phases, such as aerosol particles and cloud droplets. Many of these compounds are photolabile and can degrade through direct photolysis or indirect photooxidation processes on time scales that are comparable to the typical lifetimes of aqueous droplets (hours) and particles (days). This paper presents a systematic investigation of the molecular level composition and the extent of aqueous photochemical processing in different types of secondary organic aerosol (SOA) from biogenic and anthropogenic precursors including α-pinene, β-pinene, β-myrcene, d- limonene, α-humulene, 1,3,5-trimethylbenzene, and guaiacol, oxidized by ozone (to simulate a remote atmosphere) or by OH in the presence of NOx (to simulate an urban atmosphere). Chamber- and flow tube-generated SOA samples were collected, extracted in a methanol/water solution, and photolyzed for 1 h under identical irradiation conditions. In these experiments, the irradiation was equivalent to about 3-8 h of exposure to the sun in its zenith. The molecular level composition of the dissolved SOA was probed before and after photolysis with direct-infusion electrospray ionization high-resolution mass spectrometry (ESI-HR-MS). The mass spectra of unphotolyzed SOA generated by ozone oxidation of monoterpenes showed qualitatively similar features, and contained largely overlapping subsets of identified compounds. The mass spectra of OH/NOx generated SOA had more unique visual appearance, and indicated a lower extent of products overlap. Furthermore, the fraction of nitrogen containing species (organonitrates and nitroaromatics) was highly sensitive to the SOA precursor. These observations suggest that attribution of high-resolution mass spectra in field SOA samples to specific SOA precursors should be more straightforward under OH/NOx oxidation conditions compared to the ozone driven oxidation. Comparison of the SOA constituents

  3. SOA formation from partitioning and heterogeneous reactions: model study in the presence of inorganic species.

    PubMed

    Jang, Myoseon; Czoschke, Nadine M; Northcross, Amanda L; Cao, Gang; Shaof, David

    2006-05-01

    A predictive model for secondary organic aerosol (SOA) formation by both partitioning and heterogeneous reactions was developed for SOA created from ozonolysis of alpha-pinene in the presence of preexisting inorganic seed aerosols. SOA was created in a 2 m3 polytetrafluoroethylene film indoor chamber under darkness. Extensive sets of SOA experiments were conducted varying humidity, inorganic seed compositions comprising of ammonium sulfate and sulfuric acid, and amounts of inorganic seed mass. SOA mass was decoupled into partitioning (OM(P)) and heterogeneous aerosol production (OM(H)). The reaction rate constant for OM(H) production was subdivided into three categories (fast, medium, and slow) to consider different reactivity of organic products for the particle phase heterogeneous reactions. The influence of particle acidity on reaction rates was treated in a previous semiempirical model. Model OM(H) was developed with medium and strong acidic seed aerosols, and then extrapolated to OM(H) in weak acidic conditions, which are more relevant to atmospheric aerosols. To demonstrate the effects of preexisting glyoxal derivatives (e.g., glyoxal hydrate and dimer) on OM(H), SOA was created with a seed mixture comprising of aqueous glyoxal and inorganic species. Our results show that heterogeneous SOA formation was also influenced by preexisting reactive glyoxal derivatives.

  4. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: Explicit modeling of SOA formation from alkane and alkene oxidation

    SciTech Connect

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-08

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. Furthermore, this work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  5. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: Explicit modeling of SOA formation from alkane and alkene oxidation

    DOE PAGES

    La, Y. S.; Camredon, M.; Ziemann, P. J.; ...

    2016-02-08

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chambermore » experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. Furthermore, this work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.« less

  6. Influence of Aerosol Acidity on the Formation of Secondary Organic Aerosol from Biogenic Precursor Hydrocarbons

    EPA Science Inventory

    Secondary organic aerosol (SOA) formation and dynamics may be important factors for the role of aerosols in adverse health effects, visibility and climate change. Formation of SOA occurs when a parent volatile organic compound is oxidized to create products that form in a conden...

  7. Identification of oxidized organic atmospheric species during the Southern Oxidant and Aerosol Study (SOAS) using a novel Ion Mobility Time-of-Flight Chemical Ionization Mass Spectrometer (IMS-ToF-CIMS)

    NASA Astrophysics Data System (ADS)

    Krechmer, J.; Canagaratna, M.; Kimmel, J.; Junninen, H.; Knochenmuss, R.; Cubison, M.; Massoli, P.; Stark, H.; Jayne, J. T.; Surratt, J. D.; Jimenez, J. L.; Worsnop, D. R.

    2013-12-01

    We present results from the field deployment of a novel Ion Mobility Time-of-flight Chemical Ionization Mass Spectrometer (CI-IMS-TOF) during the Southern Oxidant and Aerosol Study (SOAS). IMS-TOF is a 2-dimensional analysis method, which separates gas-phase ions by mobility prior to determination of mass-to-charge ratio by mass spectrometry. Ion mobility is a unique physical property that is determined by the collisional cross section of an ion. Because mobility depends on size and shape, the IMS measurement is able to resolve isomers and isobaric compounds. Additionally, trends in IMS-TOF data space can be used to identify relationships between ions, such as common functionality or polymeric series. During SOAS we interfaced the IMS-TOF to a nitrate ion (NO3-) chemical ionization source that enables the selective ionization of highly oxidized gas phase species (those having a high O:C ratio) through clustering with the reagent ion. Highly oxidized products of terpenes and isoprene are important secondary organic aerosol precursors (SOA) that play an uncertain but important role in particle-phase chemistry. We present several case studies of atmospheric events during SOAS that exhibited elevated concentrations of sulfuric acid and/or organics. These events exhibited a rise in particle number and provide an opportunity to examine the role that organic species may have in local atmospheric new particle formation events. We also present the results from the field deployment and subsequent laboratory studies utilizing a Potential Aerosol Mass (PAM) flow reactor as the inlet for the CI-IMS-TOF. The reactor draws in ambient air and exposes it to high concentrations of the OH radical, created by photolysis O3 in the presence of water. The highly oxidized products are then sampled directly by the CI-IMS-TOF. We performed several experiments including placing pine and deciduous plants directly in front of the reactor opening and observed large increases in the number and

  8. Temperature Effects on Secondary Organic Aerosol (SOA) from the Dark Ozonolysis and Photo-Oxidation of Isoprene.

    PubMed

    Clark, Christopher H; Kacarab, Mary; Nakao, Shunsuke; Asa-Awuku, Akua; Sato, Kei; Cocker, David R

    2016-06-07

    Isoprene is globally the most ubiquitous nonmethane hydrocarbon. The biogenic emission is found in abundance and has a propensity for SOA formation in diverse climates. It is important to characterize isoprene SOA formation with varying reaction temperature. In this work, the effect of temperature on SOA formation, physical properties, and chemical nature is probed. Three experimental systems are probed for temperature effects on SOA formation from isoprene, NO + H2O2 photo-oxidation, H2O2 only photo-oxidation, and dark ozonolysis. These experiments show that isoprene readily forms SOA in unseeded chamber experiments, even during dark ozonolysis, and also reveal that temperature affects SOA yield, volatility, and density formed from isoprene. As temperature increases SOA yield is shown to generally decrease, particle density is shown to be stable (or increase slightly), and formed SOA is shown to be less volatile. Chemical characterization is shown to have a complex trend with both temperature and oxidant, but extensive chemical speciation are provided.

  9. Hygroscopicity of dicarbonyl-amine secondary organic aerosol products investigated with HTDMA

    NASA Astrophysics Data System (ADS)

    Hawkins, L. N.; de Haan, D. O.

    2010-12-01

    Recent studies have shown the importance of amine-dicarbonyl chemistry as a secondary organic aerosol (SOA) formation pathway, producing imines, imidazoles, and N-containing oligomers. Preliminary work in our group has suggested that some of these products may be surface active. Therefore, the presence of these products may result in important changes to submicron particle hygroscopicity that affect aerosol scattering and cloud condensation nuclei (CCN) activity, especially in regions with significant amine-containing particles. To investigate their hygroscopicity, we have designed a hygroscopicity tandem differential mobility analyzer (HTDMA) system around a 300 L Teflon chamber that allows for longer humidification times needed for some organic aerosol components that are only slightly hygroscopic. This modification provides a range of residence times from 2.5 minutes up to 1 hour, unlike previously published systems that vary from 2-30 seconds. Using the modified hygroscopicity tandem differential mobility analyzer (HTDMA), we have measured the hygroscopic growth factor (HGF) of SOA formed from reactions of glyoxal (and methylglyoxal) with methylamine, ammonium sulfate, and several amino acids. Changes to inorganic aerosol HGF in response to the presence of SOA products are also investigated.

  10. High-resolution mass spectrometry and molecular characterization of aqueous photochemistry products of common types of secondary organic aerosols.

    PubMed

    Romonosky, Dian E; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A

    2015-03-19

    This work presents a systematic investigation of the molecular level composition and the extent of aqueous photochemical processing in different types of secondary organic aerosol (SOA) from biogenic and anthropogenic precursors including α-pinene, β-pinene, β-myrcene, d-limonene, α-humulene, 1,3,5-trimethylbenzene, and guaiacol, oxidized by ozone (to simulate a remote atmosphere) or by OH in the presence of NOx (to simulate an urban atmosphere). Chamber- and flow-tube-generated SOA samples were collected, extracted in a methanol/water solution, and photolyzed for 1 h under identical irradiation conditions. In these experiments, the irradiation was equivalent to about 3-8 h of exposure to the sun in its zenith. The molecular level composition of the dissolved SOA was probed before and after photolysis with direct-infusion electrospray ionization high-resolution mass spectrometry (ESI-HR-MS). The mass spectra of unphotolyzed SOA generated by ozone oxidation of monoterpenes showed qualitatively similar features and contained largely overlapping subsets of identified compounds. The mass spectra of OH/NOx-generated SOA had more unique visual appearance and indicated a lower extent of product overlap. Furthermore, the fraction of nitrogen-containing species (organonitrates and nitroaromatics) was highly sensitive to the SOA precursor. These observations suggest that attribution of high-resolution mass spectra in field SOA samples to specific SOA precursors should be more straightforward under OH/NOx oxidation conditions compared to the ozone-driven oxidation. Comparison of the SOA constituents before and after photolysis showed the tendency to reduce the average number of atoms in the SOA compounds without a significant effect on the overall O/C and H/C ratios. SOA prepared by OH/NOx photooxidation of 1,3,5-trimethylbenzene and guaiacol were more resilient to photolysis despite being the most light-absorbing. The composition of SOA prepared by ozonolysis of

  11. Secondary Organic Aerosol Formation by Molecular-Weight Building Reactions of Biogenic Oxidation Products

    NASA Astrophysics Data System (ADS)

    Barsanti, K.; Guenther, A.; Matsunaga, S.; Smith, J.

    2006-12-01

    Understanding the chemical composition of atmospheric organic aerosols (OA) remains one of the significant challenges to accurately representing OA in air quality and climate models. Meeting this challenge will require further understanding of secondary organic aerosols (SOA), of which biogenic emissions are thought to be major precursors. Of recent interest is the significance of higher-molecular weight (MW) compounds (i.e., "oligomers"). Theoretical, laboratory, and field study results suggest that relatively volatile oxidation products may contribute to SOA formation through multi-phase MW- building reactions. The significance of such reactions for biogenic SOA formation, including for newly considered precursors such as isoprene, is explored in this work. Theoretical and field studies are employed to: 1) identify MW-building reactions that may contribute to SOA formation in the atmosphere, 2) identify MW-building reaction products in ambient samples, and 3) parameterize atmospheric SOA formation by MW-building reactions of biogenic oxidation products. Likely reactions of biogenic oxidation products include ester, amide, and peroxyhemiacetal formation. Each of the proposed reactions involves known oxidation productions of biogenic precursors (e.g., carboxylic acids and aldehydes) reacting with one another and/or other atmospheric constituents (e.g., sulfuric acid and ammonia) to form higher-MW/lower-volatility products that can condense to form SOA. It has been suggested that products of MW-building reactions can revert to the parent reactants during sampling and analysis. Thus, relatively volatile compounds detected in ambient particle samples in fact may be decomposition products of higher-MW products. The contribution of relatively volatile biogenic oxidation products to SOA via ester, amide, and peroxyhemiacetal formation, as determined by studies based on fundamental thermodynamics and gas/particle partitioning theory, will be discussed; in addition to

  12. Kinetics, Mechanism, and Secondary Organic Aerosol Yield of Aqueous Phase Photo-oxidation of α-Pinene Oxidation Products.

    PubMed

    Aljawhary, Dana; Zhao, Ran; Lee, Alex K Y; Wang, Chen; Abbatt, Jonathan P D

    2016-03-10

    Formation of secondary organic aerosol (SOA) involves atmospheric oxidation of volatile organic compounds (VOCs), the majority of which are emitted from biogenic sources. Oxidation can occur not only in the gas-phase but also in atmospheric aqueous phases such as cloudwater and aerosol liquid water. This study explores for the first time the aqueous-phase OH oxidation chemistry of oxidation products of α-pinene, a major biogenic VOC species emitted to the atmosphere. The kinetics, reaction mechanisms, and formation of SOA compounds in the aqueous phase of two model compounds, cis-pinonic acid (PIN) and tricarballylic acid (TCA), were investigated in the laboratory; TCA was used as a surrogate for 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA), a known α-pinene oxidation product. Aerosol time-of-flight chemical ionization mass spectrometry (Aerosol-ToF-CIMS) was used to follow the kinetics and reaction mechanisms at the molecular level. Room-temperature second-order rate constants of PIN and TCA were determined to be 3.3 (± 0.5) × 10(9) and 3.1 (± 0.2) × 10(8) M(-1) s(-1), respectively, from which were estimated their condensed-phase atmospheric lifetimes. Aerosol-ToF-CIMS detected a large number of products leading to detailed reaction mechanisms for PIN and MBTCA. By monitoring the particle size distribution after drying, the amount of SOA material remaining in the particle phase was determined. An aqueous SOA yield of 40 to 60% was determined for PIN OH oxidation. Although recent laboratory studies have focused primarily on aqueous-phase processing of isoprene-related compounds, we demonstrate that aqueous formation of SOA materials also occurs from monoterpene oxidation products, thus representing an additional source of biogenically driven aerosol formation.

  13. Critical factors determining the variation in SOA yields from terpene ozonolysis: a combined experimental and computational study.

    PubMed

    Donahue, Neil M; Hartz, Kara E Huff; Chuong, Bao; Presto, Albert A; Stanier, Charles O; Rosenhørn, Thomas; Robinson, Allen L; Pandis, Spyros N

    2005-01-01

    A substantial fraction of the total ultrafine particulate mass is comprised of organic compounds. Of this fraction, a significant subfraction is secondary organic aerosol (SOA), meaning that the compounds are a by-product of chemistry in the atmosphere. However, our understanding of the kinetics and mechanisms leading to and following SOA formation is in its infancy. We lack a clear description of critical phenomena; we often don't know the key, rate limiting steps in SOA formation mechanisms. We know almost nothing about aerosol yields past the first generation of oxidation products. Most importantly, we know very little about the derivatives in these mechanisms; we do not understand how changing conditions, be they precursor levels, oxidant concentrations, co-reagent concentrations (i.e., the VOC/NOx ratio) or temperature will influence the yields of SOA. In this paper we explore the connections between fundamental details of physical chemistry and the multitude of steps associated with SOA formation, including the initial gas-phase reaction mechanisms leading to condensible products, the phase partitioning itself, and the continued oxidation of the condensed-phase organic products. We show that SOA yields in the alpha-pinene + ozone are highly sensitive to NOx, and that SOA yields from beta-caryophylene + ozone appear to increase with continued ozone exposure, even as aerosol hygroscopicity increases as well. We suggest that SOA yields are likely to increase substantially through several generations of oxidative processing of the semi-volatile products.

  14. Oxygenated products of sesquiterpenes in secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    van Eijck, A.; Kampf, C.; Hoffmann, T.

    2012-04-01

    Secondary organic aerosol (SOA) has a huge impact on air quality and climate change. It influences the Earth radiative budget through absorbing, scattering and reflecting radiation as well as the formation of clouds because the particulates can act as cloud condensation nuclei (CCN). Furthermore, it plays an important role for human health. SOA is formed from gaseous precursors which get oxidized by ozone, OH- and NO3-radicals in the atmosphere. Due to their low vapor pressure these degradation products can nucleate to form new particles or they can condense on existing aerosol particles. Despite the major progress in research during the last few years the actual chemical composition as well as the contribution of various volatile organic compounds (VOCs) to the formation of secondary organic aerosol is still partially unknown. Recent studies indicate that sesquiterpenes play an important role in the formation of SOA because of the low volatility of their oxygenated products (Lee et al., 2006). Their emission is estimated to be about 14,8 Tg per year (Henze et al., 2008), however, these emission rates remain highly uncertain due to the lack of quantitative emission rate measurements. In addition, the knowledge about the actual atmospheric degradation mechanism and the main oxidation products of sesquiterpenes is quite limited. β-Caryophyllene, α-humulene, α-farnesene and β-farnesene are the most abundant sequiterpenes in many sesquiterpene emission profiles. But also aromadendren, α-bergamotene and δ-cadinene and germacrene-D can contribute significantly to some emission profiles (Duhl et al., 2008). To determine the major oxygenated products of sesquiterpenes in SOA, reaction chamber experiments with different sesquiterpenes and ozone were performed in a 100 L reaction chamber. To measure the time dependent formation of initial oxidation products, an APCI-IT-MS was directly connected to the reaction chamber. After 2 hours the APCI-IT-MS was replaced by a

  15. Secondary organic aerosol from polycyclic aromatic hydrocarbons in Southeast Texas

    NASA Astrophysics Data System (ADS)

    Zhang, Hongliang; Ying, Qi

    2012-08-01

    Recent chamber studies show that low-volatility gas phase precursors such as polycyclic aromatic hydrocarbons (PAHs) can be a significant source of secondary organic aerosol (SOA). In this work, formation of SOA from the photo-oxidation products of PAHs is added to the SOA modeling framework of the Community Multiscale Air Quality (CMAQ) model to determine the regional distribution of SOA products from PAHs (PAH-SOA) and the contributions from sources in Southeast Texas during the Texas Air Quality Study 2006 (TexAQS 2006). Results show that PAHs released from anthropogenic sources can produce SOA mass as much as 10% of that from the traditional light aromatics or approximately 4% of total anthropogenic SOA. In areas under the influence of wildfire emissions, the amount of PAH-SOA can be as much as 50% of the SOA from light aromatics. A source-oriented modeling framework is adopted to determine the major sources of PAH-SOA by tracking the emitted PAHs and their oxidation products in the gas and aerosol phases from different sources separately. Among the eight sources (vehicles, solvent utilization, residential wood, industries, natural gas combustion, coal combustion, wildfire and other sources) that are tracked in the model, wildfire, vehicles, solvent and industries are the major sources of PAH-SOA. Coal and natural gas combustion appear to be less important in terms of their contributions to PAH-SOA.

  16. Sources, properties, aging, and anthropogenic influences on OA and SOA over the Southeast US and the Amazon during SOAS, DC3, SEAC4RS, and GoAmazon

    NASA Astrophysics Data System (ADS)

    Jimenez, J. L.; Campuzano Jost, P.; Hu, W.; Palm, B. B.; Thompson, S.; Krechmer, J.; Day, D. A.; Stark, H.; Peng, Z.; Ortega, A. M.; Isaacman, G. A.; Goldstein, A. H.; Holzinger, R.; de Sá, S. S.; Martin, S. T.; Alexander, M. L.; Guenther, A. B.; Canagaratna, M. R.; Massoli, P.; Kimmel, J.; Jayne, J. T.; Worsnop, D. R.; Brune, W. H.; Lee-Taylor, J. M.; Hodzic, A.; Madronich, S.; Offenberg, J. H.; Ferreira De Brito, J.; Artaxo, P.; Manzi, A. O.

    2014-12-01

    The SE US and the Amazon have large sources of biogenic VOCs and varying anthropogenic pollution impact, and often poor aerosol model performance. Recent results on the sources, properties, aging, and impact of anthropogenic pollution on OA and secondary OA (SOA) over these regions will be presented. SOA from IEPOX accounts for 14-17% of the OA on average over the SE US and extending up to 6 km. Higher IEPOX-SOA correlates with airmasses of high isoprene, IEPOX, sulfate, acidity, and lower NO. The IEPOX organosulfate accounts for ~10% of IEPOX-SOA over the SE US. The AMS ion C5H6O+ is shown to be a good marker of IEPOX-SOA, while total m/z 82 (as in ACSM) suffers larger interferences. The sinks of IEPOX-SOA via both OH oxidation and evaporation are slow. The low-volatility of IEPOX-SOA contrasts with the small semivolatile molecules that have so far been identified as its components, suggesting the importance of oligomerization. Urban SOA is estimated to account for 25% of the OA in the SE US using either the GEOS-Chem model or the measured 14C (using recent results that urban SOA (POA) is 30% (50%) non-fossil, mainly due to cooking emissions). An oxidation flow reactor (OFR) is used to investigate SOA formation by OH, O3, and NO3 in-situ. Largest SOA formation is always observed at night when monoterpenes (MT) are largest, and is underpredicted by SOA models that use MT as precursors but ignore partially-oxidized products. Closure results from models (VBS and GECKO-A) that account for the whole oxidation chain will be presented. The partitioning of organic acids is found to proceed rapidly in response to temperature changes, in contrast with recent reports of very slow equilibration. The agreement with absorptive partitioning theory is reasonable for most species, except small acids that may be formed by thermal decomposition during analysis. Partitioning data from four instruments is compared, with reasonable agreement in many cases including the rapid response

  17. Effect of Hydrophilic Organic Seed Aerosols on Secondary Organic Aerosol Formation from Ozonolysis of α-Pinene

    SciTech Connect

    Song, Chen; Zaveri, Rahul A.; Shilling, John E.; Alexander, M. L.; Newburn, Matthew K.

    2011-07-26

    Gas-particle partitioning theory is widely used in atmospheric models to predict organic aerosol loadings. This theory predicts that secondary organic aerosol (SOA) yield of an oxidized VOC product will increase as the mass loading of preexisting organic aerosol increases. In a previous study, we showed that the presence of model hydrophobic primary organic aerosol (POA) had no detectable effect on the secondary organic aerosol (SOA) yields from ozonolysis of {alpha}-pinene, suggesting that the condensing SOA compounds form a separate phase from the preexisting POA. However, non-polar, hydrophobic POA may gradually become polar and hydrophilic as it undergoes oxidative aging while POA formed from biomass burning is already somewhat polar and hydrophilic. In this study, we investigate the effects of model hydrophilic POA such as fulvic acid, adipic acid and citric acid on the gas-particle partitioning of SOA from {alpha}-pinene ozonolysis. The results show that only citric acid seed significantly enhances the absorption of {alpha}-pinene SOA into the particle-phase. The other two POA seed particles have negligible effect on the {alpha}-pinene SOA yields, suggesting that {alpha}-pinene SOA forms a well-mixed organic aerosol phase with citric acid while a separate phase with adipic acid and fulvic acid. This finding highlights the need to improve the thermodynamics treatment of organics in current aerosol models that simply lump all hydrophilic organic species into a single phase, thereby potentially introducing an erroneous sensitivity of SOA mass to emitted POA.

  18. The MODIS Aerosol Algorithm, Products and Validation

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Kaufman, Y. J.; Tanre, D.; Mattoo, S.; Chu, D. A.; Martins, J. V.; Li, R.-R.; Ichoku, C.; Levy, R. C.; Kleidman, R. G.

    2003-01-01

    The MODerate resolution Imaging Spectroradiometer (MODIS) aboard both NASA's Terra and Aqua satellites is making near global daily observations of the earth in a wide spectral range. These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode and several derived parameters including reflected spectral solar flux at top of atmosphere. Over ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 microns to 2.13 microns. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral aerosol flux, mass concentration and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of AERONET data gleaned from 133 AERONET stations. 8000 MODIS aerosol retrievals colocated with AERONET measurements confirm that one-standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of delta tauapproximately equal to plus or minus 0.03 plus or minus 0.05 tau over ocean and delta tay equal to plus or minus 0.05 plus or minus 0.15 tau over land. 271 MODIS aerosol retrievals co-located with AERONET inversions at island and coastal sites suggest that one-standard deviation of MODIS effective radius retrievals falls within delta r_eff approximately equal to 0.11 microns. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.

  19. Multi-Sensor Aerosol Products Sampling System

    NASA Technical Reports Server (NTRS)

    Petrenko, M.; Ichoku, C.; Leptoukh, G.

    2011-01-01

    Global and local properties of atmospheric aerosols have been extensively observed and measured using both spaceborne and ground-based instruments, especially during the last decade. Unique properties retrieved by the different instruments contribute to an unprecedented availability of the most complete set of complimentary aerosol measurements ever acquired. However, some of these measurements remain underutilized, largely due to the complexities involved in analyzing them synergistically. To characterize the inconsistencies and bridge the gap that exists between the sensors, we have established a Multi-sensor Aerosol Products Sampling System (MAPSS), which consistently samples and generates the spatial statistics (mean, standard deviation, direction and rate of spatial variation, and spatial correlation coefficient) of aerosol products from multiple spacebome sensors, including MODIS (on Terra and Aqua), MISR, OMI, POLDER, CALIOP, and SeaWiFS. Samples of satellite aerosol products are extracted over Aerosol Robotic Network (AERONET) locations as well as over other locations of interest such as those with available ground-based aerosol observations. In this way, MAPSS enables a direct cross-characterization and data integration between Level-2 aerosol observations from multiple sensors. In addition, the available well-characterized co-located ground-based data provides the basis for the integrated validation of these products. This paper explains the sampling methodology and concepts used in MAPSS, and demonstrates specific examples of using MAPSS for an integrated analysis of multiple aerosol products.

  20. SOA Formation from Aqueous Processing of BVOCs in the Southeastern United States during SOAS

    NASA Astrophysics Data System (ADS)

    Skog, K.; Keutsch, F. N.

    2013-12-01

    Secondary organic aerosol (SOA) contributes to climate change and adversely affects human health, but the formation of SOA is poorly understood. Recent studies have shown that aqueous processing of water soluble compounds like glyoxal and glycolaldehyde can help close the gap in our understanding of SOA formation. During June and July of 2013, a comprehensive suite of instruments were deployed at the Southern Oxidant and Aerosol Study (SOAS) Centreville, AL ground site measuring oxidants, glyoxal and glycolaldehyde as well as their precursors, anthropogenic influence, aerosol properties and meteorology. Results from a zero-dimensional gas phase photochemical model and a zero-dimensional aqueous SOA model will be compared to the observations. Analysis will focus on the modeled contribution of glyoxal and glycolaldehyde in the context of closing the aqueous SOA budget.

  1. How will SOA change in the future?: SOA IN THE FUTURE

    SciTech Connect

    Lin, Guangxing; Penner, Joyce E.; Zhou, Cheng

    2016-02-17

    Secondary organic aerosol (SOA) plays a significant role in the Earth system by altering its radiative balance. Here we use an Earth system model coupled with an explicit SOA formation module to estimate the response of SOA concentrations to changes in climate, anthropogenic emissions, and human land use in the future. We find that climate change is the major driver for SOA change under the representative concentration pathways for the 8.5 future scenario. Climate change increases isoprene emission rate by 18% with the effect of temperature increases outweighing that of the CO2 inhibition effect. Annual mean global SOA mass is increased by 25% as a result of climate change. However, anthropogenic emissions and land use change decrease SOA. The net effect is that future global SOA burden in 2100 is nearly the same as that of the present day. The SOA concentrations over the Northern Hemisphere are predicted to decline in the future due to the control of sulfur emissions.

  2. Identification of significant precursor gases of secondary organic aerosols from residential wood combustion

    NASA Astrophysics Data System (ADS)

    Bruns, Emily A.; El Haddad, Imad; Slowik, Jay G.; Kilic, Dogushan; Klein, Felix; Baltensperger, Urs; Prévôt, André S. H.

    2016-06-01

    Organic gases undergoing conversion to form secondary organic aerosol (SOA) during atmospheric aging are largely unidentified, particularly in regions influenced by anthropogenic emissions. SOA dominates the atmospheric organic aerosol burden and this knowledge gap contributes to uncertainties in aerosol effects on climate and human health. Here we characterize primary and aged emissions from residential wood combustion using high resolution mass spectrometry to identify SOA precursors. We determine that SOA precursors traditionally included in models account for only ~3–27% of the observed SOA, whereas for the first time we explain ~84–116% of the SOA by inclusion of non-traditional precursors. Although hundreds of organic gases are emitted during wood combustion, SOA is dominated by the aging products of only 22 compounds. In some cases, oxidation products of phenol, naphthalene and benzene alone comprise up to ~80% of the observed SOA. Identifying the main precursors responsible for SOA formation enables improved model parameterizations and SOA mitigation strategies in regions impacted by residential wood combustion, more productive targets for ambient monitoring programs and future laboratories studies, and links between direct emissions and SOA impacts on climate and health in these regions.

  3. Identification of significant precursor gases of secondary organic aerosols from residential wood combustion

    PubMed Central

    Bruns, Emily A.; El Haddad, Imad; Slowik, Jay G.; Kilic, Dogushan; Klein, Felix; Baltensperger, Urs; Prévôt, André S. H.

    2016-01-01

    Organic gases undergoing conversion to form secondary organic aerosol (SOA) during atmospheric aging are largely unidentified, particularly in regions influenced by anthropogenic emissions. SOA dominates the atmospheric organic aerosol burden and this knowledge gap contributes to uncertainties in aerosol effects on climate and human health. Here we characterize primary and aged emissions from residential wood combustion using high resolution mass spectrometry to identify SOA precursors. We determine that SOA precursors traditionally included in models account for only ~3–27% of the observed SOA, whereas for the first time we explain ~84–116% of the SOA by inclusion of non-traditional precursors. Although hundreds of organic gases are emitted during wood combustion, SOA is dominated by the aging products of only 22 compounds. In some cases, oxidation products of phenol, naphthalene and benzene alone comprise up to ~80% of the observed SOA. Identifying the main precursors responsible for SOA formation enables improved model parameterizations and SOA mitigation strategies in regions impacted by residential wood combustion, more productive targets for ambient monitoring programs and future laboratories studies, and links between direct emissions and SOA impacts on climate and health in these regions. PMID:27312480

  4. Primary gas- and particle-phase emissions and secondary organic aerosol production from gasoline and diesel off-road engines.

    PubMed

    Gordon, Timothy D; Tkacik, Daniel S; Presto, Albert A; Zhang, Mang; Jathar, Shantanu H; Nguyen, Ngoc T; Massetti, John; Truong, Tin; Cicero-Fernandez, Pablo; Maddox, Christine; Rieger, Paul; Chattopadhyay, Sulekha; Maldonado, Hector; Maricq, M Matti; Robinson, Allen L

    2013-12-17

    Dilution and smog chamber experiments were performed to characterize the primary emissions and secondary organic aerosol (SOA) formation from gasoline and diesel small off-road engines (SOREs). These engines are high emitters of primary gas- and particle-phase pollutants relative to their fuel consumption. Two- and 4-stroke gasoline SOREs emit much more (up to 3 orders of magnitude more) nonmethane organic gases (NMOGs), primary PM and organic carbon than newer on-road gasoline vehicles (per kg of fuel burned). The primary emissions from a diesel transportation refrigeration unit were similar to those of older, uncontrolled diesel engines used in on-road vehicles (e.g., premodel year 2007 heavy-duty diesel trucks). Two-strokes emitted the largest fractional (and absolute) amount of SOA precursors compared to diesel and 4-stroke gasoline SOREs; however, 35-80% of the NMOG emissions from the engines could not be speciated using traditional gas chromatography or high-performance liquid chromatography. After 3 h of photo-oxidation in a smog chamber, dilute emissions from both 2- and 4-stroke gasoline SOREs produced large amounts of semivolatile SOA. The effective SOA yield (defined as the ratio of SOA mass to estimated mass of reacted precursors) was 2-4% for 2- and 4-stroke SOREs, which is comparable to yields from dilute exhaust from older passenger cars and unburned gasoline. This suggests that much of the SOA production was due to unburned fuel and/or lubrication oil. The total PM contribution of different mobile source categories to the ambient PM burden was calculated by combining primary emission, SOA production and fuel consumption data. Relative to their fuel consumption, SOREs are disproportionately high total PM sources; however, the vastly greater fuel consumption of on-road vehicles renders them (on-road vehicles) the dominant mobile source of ambient PM in the Los Angeles area.

  5. Modeling regional secondary organic aerosol using the Master Chemical Mechanism

    NASA Astrophysics Data System (ADS)

    Li, Jingyi; Cleveland, Meredith; Ziemba, Luke D.; Griffin, Robert J.; Barsanti, Kelley C.; Pankow, James F.; Ying, Qi

    2015-02-01

    A modified near-explicit Master Chemical Mechanism (MCM, version 3.2) with 5727 species and 16,930 reactions and an equilibrium partitioning module was incorporated into the Community Air Quality Model (CMAQ) to predict the regional concentrations of secondary organic aerosol (SOA) from volatile organic compounds (VOCs) in the eastern United States (US). In addition to the semi-volatile SOA from equilibrium partitioning, reactive surface uptake processes were used to simulate SOA formation due to isoprene epoxydiol, glyoxal and methylglyoxal. The CMAQ-MCM-SOA model was applied to simulate SOA formation during a two-week episode from August 28 to September 7, 2006. The southeastern US has the highest SOA, with a maximum episode-averaged concentration of ∼12 μg m-3. Primary organic aerosol (POA) and SOA concentrations predicted by CMAQ-MCM-SOA agree well with AMS-derived hydrocarbon-like organic aerosol (HOA) and oxygenated organic aerosol (OOA) urban concentrations at the Moody Tower at the University of Houston. Predicted molecular properties of SOA (O/C, H/C, N/C and OM/OC ratios) at the site are similar to those reported in other urban areas, and O/C values agree with measured O/C at the same site. Isoprene epoxydiol is predicted to be the largest contributor to total SOA concentration in the southeast US, followed by methylglyoxal and glyoxal. The semi-volatile SOA components are dominated by products from β-caryophyllene oxidation, but the major species and their concentrations are sensitive to errors in saturation vapor pressure estimation. A uniform decrease of saturation vapor pressure by a factor of 100 for all condensable compounds can lead to a 150% increase in total SOA. A sensitivity simulation with UNIFAC-calculated activity coefficients (ignoring phase separation and water molecule partitioning into the organic phase) led to a 10% change in the predicted semi-volatile SOA concentrations.

  6. Investigation of the formation of benzoyl peroxide, benzoic anhydride, and other potential aerosol products from gas-phase reactions of benzoylperoxy radicals

    NASA Astrophysics Data System (ADS)

    Strollo, Christen M.; Ziemann, Paul J.

    2016-04-01

    The secondary organic aerosol (SOA) products of the reaction of benzaldehyde with Cl atoms and with OH radicals in air in the absence of NOx were investigated in an environmental chamber in order to better understand the possible role of organic peroxy radical self-reactions in SOA formation. SOA products and authentic standards were analyzed using mass spectrometry and liquid chromatography, and results show that the yields of benzoyl peroxide (C6H5C(O)OO(O)CC6H5) and benzoic anhydride (C6H5C(O)O(O)CC6H5), two potential products from the gas-phase self-reaction of benzoylperoxy radicals (C6H5C(O)OO·), were less than 0.1%. This is in contrast to results of recent studies that have shown that the gas-phase self-reactions of β-nitrooxyperoxy radicals formed from reactions of isoprene with NO3 radicals form dialkyl peroxides that contribute significantly to gas-phase and SOA products. Such reactions have also been proposed to explain the gas-phase formation of extremely low volatility dimers from autooxidation of terpenes. The results obtained here indicate that, at least for benzoylperoxy radicals, the self-reactions form only benzoyloxy radicals. Analyses of SOA composition and volatility were inconclusive, but it appears that the SOA may consist primarily of oligomers formed through heterogeneous/multiphase reactions possibly involving some combination of phenol, benzaldehyde, benzoic acid, and peroxybenzoic acid.

  7. Analysis of reversibility and reaction products of glyoxal uptake onto ammonium sulfate aerosol

    NASA Astrophysics Data System (ADS)

    Galloway, M. M.; Chhabra, P. S.; Chan, A. W.; Surratt, J. D.; Kwan, A. J.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H.; Keutsch, F. N.

    2009-04-01

    Glyoxal, the smallest alpha-dicarbonyl, is an oxidation product of both biogenic and anthropogenic volatile organic compounds (Fu et al. JGR 113, D15303, 2008). Despite its low molecular weight, its role in secondary organic aerosol (SOA) formation has gained interest and a recent study suggested that it accounts for more than 15% of SOA in Mexico City (Volkamer et al. GRL 34, L19807, 2007). Despite numerous previous studies, questions remain regarding the processes controlling glyoxal uptake onto aerosol, including the role of acid catalysis, degree of reversibility, and identity of aerosol phase reaction products. We present results of chamber aerosol studies (Galloway et al. ACPD 8, 20799, 2008) and laboratory studies of bulk samples aimed at improving the understanding of these processes, in particular formation of oligomers and organosulfates of glyoxal, as well as the formation of imidazoles (carbon-nitrogen containing heterocyclic aromatic compounds) under dark and irradiated conditions. The relevance of these classes of reaction products extends beyond glyoxal, as evidence of oligomers and organosulfates other than those of glyoxal have been found in ambient aerosol (Surratt et al. JPCA 112, 8345, 2008; Denkenberger et al. Environ. Sci. Technol. 41, 5439, 2007). Experiments in which a chamber air mass was diluted after equilibration of glyoxal uptake onto ammonium sulfate seed aerosol (relative humidity 60% and glyoxal mixing ratios of 25-200 ppbv) shows that under these conditions uptake is reversible. The most important condensed phase products are hydrated oligomers of glyoxal, which are also formed reversibly under these conditions. Our studies show that organosulfates were not formed under dark conditions for neutral or acidified aerosol; similarly, Minerath et al. have recently shown that formation of a different class of organosulfates (alkyl sulfates) also proceeds very slowly even under acidic conditions (Environ. Sci. Technol. 42, 4410, 2008). The

  8. Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species

    NASA Astrophysics Data System (ADS)

    Wyche, K. P.; Ryan, A. C.; Hewitt, C. N.; Alfarra, M. R.; McFiggans, G.; Carr, T.; Monks, P. S.; Smallbone, K. L.; Capes, G.; Hamilton, J. F.; Pugh, T. A. M.; MacKenzie, A. R.

    2014-12-01

    Silver birch (Betula pendula) and three Southeast Asian tropical plant species (Ficus cyathistipula, Ficus benjamina and Caryota millis) from the pantropical fig and palm genera were grown in a purpose-built and environment-controlled whole-tree chamber. The volatile organic compounds emitted from these trees were characterised and fed into a linked photochemical reaction chamber where they underwent photo-oxidation under a range of controlled conditions (relative humidity or RH ~65-89%, volatile organic compound-to-NOx or VOC / NOx ~3-9 and NOx ~2 ppbV). Both the gas phase and the aerosol phase of the reaction chamber were monitored in detail using a comprehensive suite of on-line and off-line chemical and physical measurement techniques. Silver birch was found to be a high monoterpene and sesquiterpene but low isoprene emitter, and its emissions were observed to produce measurable amounts of secondary organic aerosol (SOA) via both nucleation and condensation onto pre-existing seed aerosol (YSOA 26-39%). In contrast, all three tropical species were found to be high isoprene emitters with trace emissions of monoterpenes and sesquiterpenes. In tropical plant experiments without seed aerosol there was no measurable SOA nucleation, but aerosol mass was shown to increase when seed aerosol was present. Although principally isoprene emitting, the aerosol mass produced from tropical fig was mostly consistent (i.e. in 78 out of 120 aerosol mass calculations using plausible parameter sets of various precursor specific yields) with condensation of photo-oxidation products of the minor volatile organic compounds (VOCs) co-emitted; no significant aerosol yield from condensation of isoprene oxidation products was required in the interpretations of the experimental results. This finding is in line with previous reports of organic aerosol loadings consistent with production from minor biogenic VOCs co-emitted with isoprene in principally isoprene-emitting landscapes in Southeast

  9. Secondary organic aerosol formation from photo-oxidation of unburned fuel: experimental results and implications for aerosol formation from combustion emissions.

    PubMed

    Jathar, Shantanu H; Miracolo, Marissa A; Tkacik, Daniel S; Donahue, Neil M; Adams, Peter J; Robinson, Allen L

    2013-11-19

    We conducted photo-oxidation experiments in a smog chamber to investigate secondary organic aerosol (SOA) formation from eleven different unburned fuels: commercial gasoline, three types of jet fuel, and seven different diesel fuels. The goals were to investigate the influence of fuel composition on SOA formation and to compare SOA production from unburned fuel to that from diluted exhaust. The trends in SOA production were largely consistent with differences in carbon number and molecular structure of the fuel, i.e., fuels with higher carbon numbers and/or more aromatics formed more SOA than fuels with lower carbon numbers and/or substituted alkanes. However, SOA production from different diesel fuels did not depend strongly on aromatic content, highlighting the important contribution of large alkanes to SOA formation from mixtures of high carbon number (lower volatility) precursors. In comparison to diesels, SOA production from higher volatility fuels such as gasoline appeared to be more sensitive to aromatic content. On the basis of a comparison of SOA mass yields (SOA mass formed per mass of fuel reacted) and SOA composition (as measured by an aerosol mass spectrometer) from unburned fuels and diluted exhaust, unburned fuels may be reasonable surrogates for emissions from uncontrolled engines but not for emissions from engines with after treatment devices such as catalytic converters.

  10. Optical Properties of Polymers Relevant to Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Marrero-Ortiz, W.; Gomez-Hernandez, M. E.; Xu, W.; Guo, S.; Zhang, R.

    2014-12-01

    Atmospheric aerosols play a critical role in climate directly by scattering and absorbing solar radiation and indirectly by modifying the cloud formation. Currently, the direct and indirect effects of aerosols represent the largest uncertainty in climate predictions models. Some aerosols are directly emitted, but the majority are formed in the atmosphere by the oxidation of gaseous precursors. However, the formation of aerosols at the molecular level is not fully characterized. Certain category of secondary organic aerosols (SOA), which represent a significant fraction of the total aerosol burden, can be light-absorbing, also known as brown carbon. However, the overall contribution of SOA to the brown carbon and the related climate forcing is poorly understood. Such incomplete understanding is due in part to the chemical complexity of SOA and the lack of knowledge regarding SOA formation, transformation, and optical properties. Based on previous laboratory experiments, field measurements, and modeling studies, it has been suggested that the polymers and oligomers play an important role in the SOA formation. Atmospheric polymers could be produced by the hydration or heterogeneous reactions of epoxides and small α-dicarbonyls. Their aqueous chemistry products have been shown to give light-absorbing and high molecular weight oligomeric species, which increase the SOA mass production and alter the direct and indirect effect of aerosols. In this paper, the aerosol chemistry of small α-dicarbonyl compounds with amines is investigated and the associated optical properties are measured using spectroscopic techniques. The differences between primary, secondary and tertiary amines with glyoxal and methylglyoxal are evaluated in terms of SOA browning efficiency. Atmospheric implications of our present work for understanding the formation of light-absorbing SOA will be presented, particularly in terms of the product distribution of light-absorbing SOA formed by aqueous phase

  11. Experimental determination of the partitioning coefficient and volatility of important BVOC oxidation products using the Aerosol Collection Module (ACM) coupled to a PTR-ToF-MS

    NASA Astrophysics Data System (ADS)

    Gkatzelis, G.; Hohaus, T.; Tillmann, R.; Schmitt, S. H.; Yu, Z.; Schlag, P.; Wegener, R.; Kaminski, M.; Kiendler-Scharr, A.

    2015-12-01

    Atmospheric aerosol can alter the Earth's radiative budget and global climate but can also affect human health. A dominant contributor to the submicrometer particulate matter (PM) is organic aerosol (OA). OA can be either directly emitted through e.g. combustion processes (primary OA) or formed through the oxidation of organic gases (secondary organic aerosol, SOA). A detailed understanding of SOA formation is of importance as it constitutes a major contribution to the total OA. The partitioning between the gas and particle phase as well as the volatility of individual components of SOA is yet poorly understood adding uncertainties and thus complicating climate modelling. In this work, a new experimental methodology was used for compound-specific analysis of organic aerosol. The Aerosol Collection Module (ACM) is a newly developed instrument that deploys an aerodynamic lens to separate the gas and particle phase of an aerosol. The particle phase is directed to a cooled sampling surface. After collection particles are thermally desorbed and transferred to a detector for further analysis. In the present work, the ACM was coupled to a Proton Transfer Reaction-Time of Flight-Mass Spectrometer (PTR-ToF-MS) to detect and quantify organic compounds partitioning between the gas and particle phase. This experimental approach was used in a set of experiments at the atmosphere simulation chamber SAPHIR to investigate SOA formation. Ozone oxidation with subsequent photochemical aging of β-pinene, limonene and real plant emissions from Pinus sylvestris (Scots pine) were studied. Simultaneous measurement of the gas and particle phase using the ACM-PTR-ToF-MS allows to report partitioning coefficients of important BVOC oxidation products. Additionally, volatility trends and changes of the SOA with photochemical aging are investigated and compared for all systems studied.

  12. Secondary organic aerosol from ozone-initiated reactions with terpene-rich household products

    NASA Astrophysics Data System (ADS)

    Coleman, Beverly K.; Lunden, Melissa M.; Destaillats, Hugo; Nazaroff, William W.

    We analyzed secondary organic aerosol (SOA) data from a series of small-chamber experiments in which terpene-rich vapors from household products were combined with ozone under conditions analogous to product use indoors. Reagents were introduced into a continuously ventilated 198 L chamber at steady rates. Consistently, at the time of ozone introduction, nucleation occurred exhibiting similar behavior to atmospheric events. The initial nucleation burst and growth was followed by a period in which approximately stable particle levels were established, reflecting a balance between new particle formation, condensational growth, and removal by ventilation. Airborne particles were measured with a scanning mobility particle sizer (SMPS, 10-400 nm) in every experiment and with an optical particle counter (OPC, 0.1-2.0 μm) in a subset. Parameters for a three-mode lognormal fit to the size distribution at steady state were determined for each experiment. Increasing the supply ozone level increased the steady-state mass concentration and yield of SOA from each product tested. Decreasing the air-exchange rate increased the yield. The steady-state fine-particle mass concentration (PM 1.1) ranged from 10 to >300 μg m -3 and yields ranged from 5% to 37%. Steady-state nucleation rates and SOA mass formation rates were ˜10 cm -3 s -1 and ˜10 μg m -3 min -1, respectively.

  13. Secondary organic aerosol from ozone-initiated reactions with terpene-rich household products

    SciTech Connect

    Coleman, Beverly; Coleman, Beverly K.; Lunden, Melissa M.; Destaillats, Hugo; Nazaroff, William W.

    2008-01-01

    We analyzed secondary organic aerosol (SOA) data from a series of small-chamber experiments in which terpene-rich vapors from household products were combined with ozone under conditions analogous to product use indoors. Reagents were introduced into a continuously ventilated 198 L chamber at steady rates. Consistently, at the time of ozone introduction, nucleation occurred exhibiting behavior similar to atmospheric events. The initial nucleation burst and growth was followed by a period in which approximately stable particle levels were established reflecting a balance between new particle formation, condensational growth, and removal by ventilation. Airborne particles were measured with a scanning mobility particle sizer (SMPS, 10 to 400 nm) in every experiment and with an optical particle counter (OPC, 0.1 to 2.0 ?m) in a subset. Parameters for a three-mode lognormal fit to the size distribution at steady state were determined for each experiment. Increasing the supply ozone level increased the steady-state mass concentration and yield of SOA from each product tested. Decreasing the air-exchange rate increased the yield. The steady-state fine-particle mass concentration (PM1.1) ranged from 10 to> 300 mu g m-3 and yields ranged from 5percent to 37percent. Steady-state nucleation rates and SOA mass formation rates were on the order of 10 cm-3 s-1 and 10 mu g m-3 min-1, respectively.

  14. Laboratory studies of oxidation of primary emissions: Oxidation of organic molecular markers and secondary organic aerosol production

    NASA Astrophysics Data System (ADS)

    Weitkamp, Emily A.

    vehicle markers. Aerosol composition is a key influence on reaction rate constants, perhaps more significant than external influences. Alkenoic acid concentrations in the meat grease particles appear to influence cholesterol oxidation rates. Also, the reaction rate constants for new motor oil were faster than those of the more viscous used motor oil. The measured reaction rate constants were used to oxidize source profiles that were subsequently run in the Chemical Mass Balance (CMB) model. Oxidizing the molecular markers in the meat-cooking profile led to unrealistically high meat-cooking aerosol contributions to the total organic carbon (OC), often more than 100%. This suggests that there is either unaccounted for sources of meat-cooking molecular markers in the ambient samples, or there is some property of atmospheric aerosols that significantly inhibits reaction that was not captured in this study. Oxidation of motor vehicle profiles led to both higher estimates of total vehicle OC and a quadrupling of gasoline OC, while the diesel contribution changed very little. The increase in gasoline OC changes gasoline vehicle emissions from a relatively minor source to a major one. Thus, oxidation of molecular markers can have a significant impact on receptor model predictions. The second objective was to investigate SOA formation from the photo-oxidation of whole diesel exhaust. Diluted exhaust from a diesel engine was photo-oxidized in a smog chamber to investigate SOA production. Photochemical oxidation rapidly produced significant SOA, almost doubling the organic aerosol contribution of primary emissions after several hours of processing. Less than 10% of the SOA mass could be explained using a SOA model and the measured oxidation of known precursors, such as light aromatics. However, the ultimate yield of SOA is uncertain because it is sensitive to treatment of particle and vapor losses to the chamber walls. Aerosol Mass Spectrometer (AMS) mass spectra reveal that the

  15. Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species

    NASA Astrophysics Data System (ADS)

    Wyche, K. P.; Ryan, A. C.; Hewitt, C. N.; Alfarra, M. R.; McFiggans, G.; Carr, T.; Monks, P. S.; Smallbone, K. L.; Capes, G.; Hamilton, J. F.; Pugh, T. A. M.; MacKenzie, A. R.

    2014-06-01

    Silver birch (Betula pendula) and three Southeast Asian tropical plant species (Ficus cyathistipula, Ficus benjamina and Caryota millis) from the pantropical fig and palm genera were grown in a purpose-built and environment-controlled whole-tree chamber. The volatile organic compounds emitted from these trees were characterised and fed into a linked photochemical reaction chamber where they underwent photooxidation under a range of controlled conditions (RH ∼65-89%, VOC/NOx ∼3-9 and NOx ∼2 ppbV). Both the gas phase and the aerosol phase of the reaction chamber were monitored in detail using a comprehensive suite of on-line and off-line, chemical and physical measurement techniques. Silver birch was found to be a high monoterpene and sesquiterpene, but low isoprene emitter, and its emissions were observed to produce measureable amounts of SOA via both nucleation and condensation onto pre-existing seed aerosol (YSOA 26-39%). In contrast, all three tropical species were found to be high isoprene emitters with trace emissions of monoterpenes and sesquiterpenes. In tropical plant experiments without seed aerosol there was no measurable SOA nucleation, but aerosol mass was shown to increase when seed aerosol was present. Although principally isoprene emitting, the aerosol mass produced from tropical fig was mostly consistent (i.e., in 78 out of 120 aerosol mass calculations using plausible parameter sets of various precursor specific yields) with condensation of photooxidation products of the minor VOCs co-emitted; no significant aerosol yield from condensation of isoprene oxidation products was required in the interpretations of the experimental results. This finding is in line with previous reports of organic aerosol loadings consistent with production from minor biogenic VOCs co-emitted with isoprene in principally-isoprene emitting landscapes in Southeast Asia. Moreover, in general the amount of aerosol mass produced from the emissions of the principally

  16. Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

    PubMed

    Shiraiwa, Manabu; Yee, Lindsay D; Schilling, Katherine A; Loza, Christine L; Craven, Jill S; Zuend, Andreas; Ziemann, Paul J; Seinfeld, John H

    2013-07-16

    Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

  17. Aqueous-phase mechanism for secondary organic aerosol ...

    EPA Pesticide Factsheets

    Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA), but the mechanism and yields are uncertain. Aerosol is prevailingly aqueous under the humid conditions typical of isoprene-emitting regions. Here we develop an aqueous-phase mechanism for isoprene SOA formation coupled to a detailed gas-phase isoprene oxidation scheme. The mechanism is based on aerosol reactive uptake coefficients (γ) for water-soluble isoprene oxidation products, including sensitivity to aerosol acidity and nucleophile concentrations. We apply this mechanism to simulation of aircraft (SEAC4RS) and ground-based (SOAS) observations over the southeast US in summer 2013 using the GEOS-Chem chemical transport model. Emissions of nitrogen oxides (NOx  ≡  NO + NO2) over the southeast US are such that the peroxy radicals produced from isoprene oxidation (ISOPO2) react significantly with both NO (high-NOx pathway) and HO2 (low-NOx pathway), leading to different suites of isoprene SOA precursors. We find a mean SOA mass yield of 3.3 % from isoprene oxidation, consistent with the observed relationship of total fine organic aerosol (OA) and formaldehyde (a product of isoprene oxidation). Isoprene SOA production is mainly contributed by two immediate gas-phase precursors, isoprene epoxydiols (IEPOX, 58 % of isoprene SOA) from the low-NOx pathway and glyoxal (28 %) from both low- and high-NOx pathways. This speciation is consistent with observati

  18. [Study on transformation mechanism of SOA from biogenic VOC under UV-B condition].

    PubMed

    Li, Ying-Ying; Li, Xiang; Chen, Jian-Min

    2011-12-01

    A laboratory study was carried out to investigate the biogenic volatile organic compounds (BVOC) in a lab-made glass chamber. The secondary organic aerosol (SOA) products can be detected under the UV photooxidation of BVOC. Pelargonium x Citrenella was chosen as the target plant in this research because it can release a large amount of BVOCs. The predominant 7 alkene and ketol compounds were detected by using solid phase microextraction (SPME) sampling and gas chromatography/mass spectrometry (GC/MS) analysis. The photochemical experiment indicated that these BVOC can be rapidly oxidized into SOA under UV-B irradiation. A tandem differential mobility analyzer (TDMA) was used to measure the size distribution and the hygroscopicity of the SOA. The particle diameter was in the range of 50 nm to 320 nm. The high hygroscopicity of SOA was also obtained and the size increased from 1.05 to 1.11 during the wet experiment.

  19. Aerosol Best Estimate Value-Added Product

    SciTech Connect

    Flynn, C; Turner, D; Koontz, A; Chand, D; Sivaraman, C

    2012-07-19

    The objective of the Aerosol Best Estimate (AEROSOLBE) value-added product (VAP) is to provide vertical profiles of aerosol extinction, single scatter albedo, asymmetry parameter, and Angstroem exponents for the atmospheric column above the Central Facility at the ARM Southern Great Plains (SGP) site. We expect that AEROSOLBE will provide nearly continuous estimates of aerosol optical properties under a range of conditions (clear, broken clouds, overcast clouds, etc.). The primary requirement of this VAP was to provide an aerosol data set as continuous as possible in both time and height for the Broadband Heating Rate Profile (BBHRP) VAP in order to provide a structure for the comprehensive assessment of our ability to model atmospheric radiative transfer for all conditions. Even though BBHRP has been completed, AEROSOLBE results are very valuable for environmental, atmospheric, and climate research.

  20. SOA Formation form the NO3 radicals Chemistry of Isoprene, Monoterpenes, Sesquiterpenes, Biogenic Oxygenated Compounds, and Aromatics

    NASA Astrophysics Data System (ADS)

    Kleindienst, T. E.; Jaoui, M.; Docherty, K.; Corse, E.; Offenberg, J. H.; Lewandowski, M.

    2011-12-01

    Volatile organic compounds (VOCs) are oxidized in the atmosphere primarily by hydroxyl radicals (OH) during daylight hours but also by nitrate radicals (NO3) during overnight, photochemically inactive periods. While reactions with OH have received considerable attention with regard to gas-phase reaction products and secondary organic aerosol (SOA) formation, less is known about the mechanisms and products resulting from nighttime NO3 reactions despite their potential for SOA formation. To date, there have been limited studies on the chemical characteristics of aerosol reaction products formed from VOCs oxidation with NO3, and few SOA reaction products have been identified. Nighttime reactions have nevertheless been incorporated into some air quality models despite the limited information available and substantial uncertainties which still exist. The National Exposure Research Laboratory of the U.S. Environmental Protection Agency recently undertook an integrated laboratory research effort to better understand the contribution of NO3 reactions to nighttime SOA formation. Isoprene, methacrolein, a-pinene, b-pinene, d-limonene, b-caryophyllene, farnesene, a-humulene, 2-methyl-3-buten-2-ol, toluene, m-xylene, and naphthalene were reacted with NO3 under a wide range of conditions in a series of separate photochemical reaction chamber experiments. These hydrocarbons are thought to contribute to ambient SOA formation. NO3 was formed through thermal decomposition of N2O5. The yield, physical characteristics, and composition of SOA formed in each experiment was analyzed by a suite of instruments including a scanning mobility particle sizer, a Sunset Labs semi continuous EC-OC monitor, a volatility differential mobility analyzer, a direct insertion probe-mass spectrometer, a high resolution time-of-flight aerosol mass spectrometer, and a gas-chromatography-mass spectrometer. To understand the relative contributions of nighttime versus daytime VOCs reactions, a similar

  1. Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

    NASA Astrophysics Data System (ADS)

    Valorso, R.; Aumont, B.; Camredon, M.; Raventos-Duran, T.; Mouchel-Vallon, C.; Ng, N. L.; Seinfeld, J. H.; Lee-Taylor, J.; Madronich, S.

    2011-07-01

    The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 on average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

  2. Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation

    NASA Astrophysics Data System (ADS)

    Valorso, R.; Aumont, B.; Camredon, M.; Raventos-Duran, T.; Mouchel-Vallon, C.; Ng, N. L.; Seinfeld, J. H.; Lee-Taylor, J.; Madronich, S.

    2011-03-01

    The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pvap) were estimated with three commonly used structure activity relationships. The values of Pvap were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pvap range between a factor of 5 to 200 in average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NOx conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pvap estimation method.

  3. Examining the role of NOx and acidity on organic aerosol formation through predictions of key isoprene aerosol species in the United States

    EPA Science Inventory

    Isoprene is a significant contributor to organic aerosol in the Southeastern United States. Later generation isoprene products, specifically isoprene epoxydiols (IEPOX) and methacryloylperoxynitrate (MPAN), have been identified as SOA precursors. The contribution of each pathway ...

  4. Exposure of BALB/c Mice to Diesel Engine Exhaust Origin Secondary Organic Aerosol (DE-SOA) during the Developmental Stages Impairs the Social Behavior in Adult Life of the Males.

    PubMed

    Win-Shwe, Tin-Tin; Kyi-Tha-Thu, Chaw; Moe, Yadanar; Fujitani, Yuji; Tsukahara, Shinji; Hirano, Seishiro

    2015-01-01

    Secondary organic aerosol (SOA) is a component of particulate matter (PM) 2.5 and formed in the atmosphere by oxidation of volatile organic compounds. Recently, we have reported that inhalation exposure to diesel engine exhaust (DE) originated SOA (DE-SOA) affect novel object recognition ability and impair maternal behavior in adult mice. However, it is not clear whether early life exposure to SOA during the developmental stages affect social behavior in adult life or not. In the present study, to investigate the effects of early life exposure to DE-SOA during the gestational and lactation stages on the social behavior in the adult life, BALB/c mice were exposed to clean air (control), DE, DE-SOA and gas without any PM in the inhalation chambers from gestational day 14 to postnatal day 21 for 5 h a day and 5 days per week. Then adult mice were examined for changes in their social behavior at the age of 13 week by a sociability and social novelty preference, social interaction with a juvenile mouse and light-dark transition test, hypothalamic mRNA expression levels of social behavior-related genes, estrogen receptor-alpha and oxytocin receptor as well as of the oxidative stress marker gene, heme oxygenase (HO)-1 by real-time RT-PCR method. In addition, hypothalamic level of neuronal excitatory marker, glutamate was determined by ELISA method. We observed that sociability and social novelty preference as well as social interaction were remarkably impaired, expression levels of estrogen receptor-alpha, oxytocin receptor mRNAs were significantly decreased, expression levels of HO-1 mRNAs and glutamate levels were significantly increased in adult male mice exposed to DE-SOA compared to the control ones. Findings of this study indicate early life exposure of BALB/c mice to DE-SOA may affect their late-onset hypothalamic expression of social behavior related genes, trigger neurotoxicity and impair social behavior in the males.

  5. Exposure of BALB/c Mice to Diesel Engine Exhaust Origin Secondary Organic Aerosol (DE-SOA) during the Developmental Stages Impairs the Social Behavior in Adult Life of the Males

    PubMed Central

    Win-Shwe, Tin-Tin; Kyi-Tha-Thu, Chaw; Moe, Yadanar; Fujitani, Yuji; Tsukahara, Shinji; Hirano, Seishiro

    2016-01-01

    Secondary organic aerosol (SOA) is a component of particulate matter (PM) 2.5 and formed in the atmosphere by oxidation of volatile organic compounds. Recently, we have reported that inhalation exposure to diesel engine exhaust (DE) originated SOA (DE-SOA) affect novel object recognition ability and impair maternal behavior in adult mice. However, it is not clear whether early life exposure to SOA during the developmental stages affect social behavior in adult life or not. In the present study, to investigate the effects of early life exposure to DE-SOA during the gestational and lactation stages on the social behavior in the adult life, BALB/c mice were exposed to clean air (control), DE, DE-SOA and gas without any PM in the inhalation chambers from gestational day 14 to postnatal day 21 for 5 h a day and 5 days per week. Then adult mice were examined for changes in their social behavior at the age of 13 week by a sociability and social novelty preference, social interaction with a juvenile mouse and light-dark transition test, hypothalamic mRNA expression levels of social behavior-related genes, estrogen receptor-alpha and oxytocin receptor as well as of the oxidative stress marker gene, heme oxygenase (HO)-1 by real-time RT-PCR method. In addition, hypothalamic level of neuronal excitatory marker, glutamate was determined by ELISA method. We observed that sociability and social novelty preference as well as social interaction were remarkably impaired, expression levels of estrogen receptor-alpha, oxytocin receptor mRNAs were significantly decreased, expression levels of HO-1 mRNAs and glutamate levels were significantly increased in adult male mice exposed to DE-SOA compared to the control ones. Findings of this study indicate early life exposure of BALB/c mice to DE-SOA may affect their late-onset hypothalamic expression of social behavior related genes, trigger neurotoxicity and impair social behavior in the males. PMID:26834549

  6. High-NOx Photooxidation of n-Dodecane: Temperature Dependence of SOA Formation.

    PubMed

    Lamkaddam, Houssni; Gratien, Aline; Pangui, Edouard; Cazaunau, Mathieu; Picquet-Varrault, Bénédicte; Doussin, Jean-François

    2017-01-03

    The temperature and concentration dependence of secondary organic aerosol (SOA) yields has been investigated for the first time for the photooxidation of n-dodecane (C12H26) in the presence of NOx in the CESAM chamber (French acronym for "Chamber for Atmospheric Multiphase Experimental Simulation"). Experiments were performed with and without seed aerosol between 283 and 304.5 K. In order to quantify the SOA yields, a new parametrization is proposed to account for organic vapor loss to the chamber walls. Deposition processes were found to impact the aerosol yields by a factor from 1.3 to 1.8 between the lowest and the highest value. As with other photooxidation systems, experiments performed without seed and at low concentration of oxidant showed a lower SOA yield than other seeded experiments. Temperature did not significantly influence SOA formation in this study. This unforeseen behavior indicates that the SOA is dominated by sufficiently low volatility products for which a change in their partitioning due to temperature would not significantly affect the condensed quantities.

  7. oVOC production from tropospheric alkyne oxidation and contribution to aerosol formation and growth

    NASA Astrophysics Data System (ADS)

    Goodall, Iain

    2013-04-01

    Ethyne (C2H2) is one of the simplest volatile organic compounds (VOC) and is predominantly emitted via anthropogenic processes and reacts with nitrogen oxides (NOx) in the presence of sunlight to form tropospheric ozone (O3). The dominant oxidation product of ethyne is the dicarbonyl species glyoxal (CHOCHO), which is thought to be a significant contributor to secondary organic aerosol (SOA) formation via irreversible oligomerisation reactions upon the surface of hydrated aerosol particulates and within cloud droplets. A series of chamber experiments were performed at the EUPHORE facility (Valencia, Spain) to study the atmospheric oxidation of ethyne, to determine oxidation product yields and to monitor SOA formation and growth by dicarbonyl oligomerisation. A Proton Transfer Reaction-Time of Flight- Mass Spectrometer (PTR-ToF-MS) was deployed by the University of Leicester to monitor precursor decay and the subsequent evolution of any gas-phase oxidised volatile organic compounds (oVOC). This was further complemented by a Broadband Cavity Enhanced Absorption Spectrometer (BBCEAS) for specific dicarbonyl and NO2 measurements. Aqueous extracts of chamber SOA were taken from filters collected during the experiments and subsequently analysed offline. The work explores the yields of low molecular weight products of ethyne oxidation for light and dark reactions, with varying levels of NOx and OH. Novel experiments were performed under atmospherically relevant conditions utilising natural lighting rather than artificial lighting. Reaction yields have been assessed with the aim of contributing to the ethyne and glyoxal mechanisms in the Master Chemical Mechanism (MCM; http://mcm.leeds.ac.uk/MCM), and have been compared with previously reported values determined from experiments performed under artificial lighting conditions.

  8. Formation of brown carbon via reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic precursors

    NASA Astrophysics Data System (ADS)

    Updyke, Katelyn M.; Nguyen, Tran B.; Nizkorodov, Sergey A.

    2012-12-01

    Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, α-pinene, limonene, α-cedrene, α-humulene, farnesene, pine leaf essential oils, cedar leaf essential oils) and anthropogenic (tetradecane, 1,3,5-trimethylbenzene, naphthalene) precursors were exposed to humid air containing approximately 100 ppb of gaseous ammonia (NH3). Reactions of SOA compounds with NH3 resulted in production of light-absorbing "brown carbon" compounds, with the extent of browning ranging from no observable change (isoprene SOA) to visible change in color (limonene SOA). The aqueous phase reactions with dissolved ammonium (NH4+) salts, such as ammonium sulfate, were equally efficient in producing brown carbon. Wavelength-dependent mass absorption coefficients (MAC) of the aged SOA were quantified by extracting known amounts of SOA material in methanol and recording its UV/Vis absorption spectra. For a given precursor, the OH-generated SOA had systematically lower MAC compared to the O3-generated SOA. The highest MAC values, for brown carbon from SOA resulting from O3 oxidation of limonene and sesquiterpenes, were comparable to MAC values for biomass burning particles but considerably smaller than MAC values for black carbon aerosols. The NH3/NH4+ + SOA brown carbon aerosol may contribute to aerosol optical density in regions with elevated concentrations of NH3 or ammonium sulfate and high photochemical activity.

  9. Limited Effect of Anthropogenic Nitrogen Oxides on Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Unger, N.; Hodzic, A.; Knote, C. J.; Tilmes, S.; Emmons, L. K.; Lamarque, J. F.; Yu, P.

    2014-12-01

    Globally secondary organic aerosol (SOA) is mostly formed from biogenic vegetation emissions and as such is regarded as natural aerosol that cannot be reduced by emission control legislation. However, recent research implies that human activities facilitate SOA formation by affecting the amount of precursor emission, the chemical processing and the partitioning into the aerosol phase. Among the multiple human influences, nitrogen oxides (NO + NO2 = NOx) have been assumed to play a critical role in the chemical formation of low volatile compounds. The goal of this study is to improve the SOA scheme in the global NCAR Community Atmospheric Model version 4 with chemistry (CAM4-Chem) by implementing an updated 4-product Volatility Basis Set (VBS) scheme, and apply it to investigate the impact of anthropogenic NOx on SOA. We first compare three different SOA parameterizations: a 2-product model and the updated VBS model both with and without a SOA aging parameterization. Secondly we evaluate predicted organic aerosol amounts against surface measurement from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network and Aerosol Mass Spectrometer (AMS) measurements from 13 aircraft-based field campaigns. We then perform sensitivity experiments to examine how the SOA loading responds to a 50% reduction in anthropogenic NOx in different regions. We find limited SOA reductions of -2.3%, -5.6% and -4.0% for global, southeastern U.S. and Amazon NOx perturbations, respectively. To investigate the chemical processes in more detail, we also use a simplified box model with the same gas-phase chemistry and gas-aerosol partitioning mechanism as in CAM4-Chem to examine the SOA yields dependence on initial precursor emissions and background NOx level. The fact that SOA formation is almost unaffected by changes in NOx can be largely attributed to buffering in chemical pathways (low- versus high-NOx pathways, OH versus NO3-initiated oxidation) and to offsetting

  10. ORACLE (v1.0): module to simulate the organic aerosol composition and evolution in the atmosphere

    NASA Astrophysics Data System (ADS)

    Tsimpidi, A. P.; Karydis, V. A.; Pozzer, A.; Pandis, S. N.; Lelieveld, J.

    2014-12-01

    A computationally efficient module to describe organic aerosol (OA) partitioning and chemical aging has been developed and implemented into the EMAC atmospheric chemistry-climate model. The model simulates the formation of secondary organic aerosol (SOA) from semivolatile (SVOCs), intermediate-volatility (IVOCs), and volatile organic compounds (VOCs). It distinguishes SVOCs from biomass burning and all other combustion sources using two surrogate species for each source category with an effective saturation concentration at 298 K of C* = 0.1 and 10 μg m-3. Two additional surrogate species with C* = 103 and 105 μg m-3 are used for the IVOCs emitted by the above source categories. Gas-phase photochemical reactions that change the volatility of the organics are taken into account. The oxidation products (SOA-sv, SOA-iv, and SOA-v) of each group of precursors (SVOCs, IVOCs, and VOCs) are simulated separately to keep track of their origin. ORACLE efficiently describes the OA composition and evolution in the atmosphere and can be used to (i) estimate the relative contributions of SOA and primary organic aerosol (POA) to total OA, (ii) determine how SOA concentrations are affected by biogenic and anthropogenic emissions, and (iii) evaluate the effects of photochemical aging and long-range transport on the OA budget. We estimate that the global average near-surface OA concentration is 1.5 μg m-3 and consists of 7% POA from fuel combustion, 11% POA from biomass burning, 2% SOA-sv from fuel combustion, 3% SOA-sv from biomass burning, 15% SOA-iv from fuel combustion, 28% SOA-iv from biomass burning, 19% biogenic SOA-v, and 15% anthropogenic SOA-v. The modeled tropospheric burden of OA components is 0.23 Tg POA, 0.16 Tg SOA-sv, 1.41 Tg SOA-iv, and 1.2 Tg SOA-v.

  11. Lessons Learned About Organic Aerosol Formation in the Southeast U.S. Using Observations and Modeling

    EPA Science Inventory

    Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA). In this work, modeling of isoprene SOA via heterogeneous uptake is explored and compared to observations from the Southern Oxidant and Aerosol Study (SOAS).

  12. Morphology of Mixed Primary and Secondary Organic Particles and the Adsorption of Spectator Organic Gases during Aerosol Formation

    SciTech Connect

    Vaden, Timothy D.; Song, Chen; Zaveri, Rahul A.; Imre, D.; Zelenyuk, Alla

    2010-04-13

    Traditional semi-empirical secondary organic aerosol (SOA) models assume that SOA mixes well with primary organic aerosols (POA), which significantly enhances the modeled SOA yields. These models further assume that the organic compounds in the gas phase do no condense on SOA as it forms. These assumptions were challenged through a detailed experimental investigation of the compositions and morphologies of SOA particles formed during ozonolysis of α-pinene in the presence of dioctyl phthalate (DOP) particles and DOP gas phase component using a single particle mass spectrometer. Ultraviolet (UV) laser depth-profiling experiments were used to characterize different types of mixed SOA/DOP particles: those formed by condensation of the oxidized α-pinene products on size-selected DOP particles and by condensation of DOP on size-selected α-pinene SOA particles. The results of these measurements conclusively show that the hydrophilic SOA and hydrophobic DOP do not mix, but instead form distinct phases. An examination of homogeneously-nucleated SOA particles formed in the presence of DOP shows them to be encapsulated by a thin DOP layer. Thus SOA can adsorb gas-phase DOP even though it has an extremely low vapor pressure (1.3×10-7 Torr), which has significant implications for SOA formation and fate in the atmosphere, where numerous organic compounds with various volatilities are present.

  13. Silicon production in an aerosol reactor

    NASA Technical Reports Server (NTRS)

    Wu, J. J.; Flagan, R. C.

    1986-01-01

    An aerosol reactor system was developed in which large particles of silicon can be grown by silane pyrolysis. To grow particles to sizes larger than one micron, vapor deposition must be used to grow a relatively small number of seed particles. Suppression of nucleation is achieved by limiting the rate of gas phase chemical reactions such that the condensible products of the gas phase chemical reactions diffuse to the surface of the seed particles as rapidly as they are produced. This prevents high degrees of supersaturation and runaway nucleation during the growth process. Particles on the order of 10 microns were grown repeatedly with the present aersol reactor. The nucleation controlled aerosol reactor is, therefore, a suitable system for the production of powders that can readily be separated from the gas by aerodynamic means.

  14. Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; Rubach, F.; Kleist, E.; Wildt, J.; Mentel, Th. F.; Carrasquillo, A. J.; Daumit, K. E.; Hunter, J. F.; Kroll, J. H.; Worsnop, D. R.; Thornton, J. A.

    2015-07-01

    We measured a large suite of gas- and particle-phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas and particle phases, the latter being detected by temperature-programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO-HR-ToF-CIMS are highly correlated with, and explain at least 25-50 % of, the organic aerosol mass measured by an Aerodyne aerosol mass spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from high molecular weight organics and/or oligomers (i.e., multi-phase accretion reaction products). Approximately 50 % of the HR-ToF-CIMS particle-phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption-temperature-based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas-particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the conversion of

  15. Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; Rubach, F.; Kleist, E.; Wildt, J.; Mentel, Th. F.; Carrasquillo, A.; Daumit, K.; Hunter, J.; Kroll, J. H.; Worsnop, D.; Thornton, J. A.

    2015-02-01

    We measured a large suite of gas and particle phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas and particle phases, the latter being detected upon temperature programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO HR-ToF-CIMS are highly correlated with, and explain at least 25-50% of, the organic aerosol mass measured by an Aerodyne Aerosol Mass Spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from large molecular weight organics and/or oligomers (i.e. multi-phase accretion reaction products). Approximately 50% of the HR-ToF-CIMS particle phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption temperature based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas-particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the conversion of

  16. Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

    DOE PAGES

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; ...

    2015-02-18

    We measured a large suite of gas and particle phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gasmore » and particle phases, the latter being detected upon temperature programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO HR-ToF-CIMS are highly correlated with, and explain at least 25–50% of, the organic aerosol mass measured by an Aerodyne Aerosol Mass Spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from large molecular weight organics and/or oligomers (i.e. multi-phase accretion reaction products). Approximately 50% of the HR-ToF-CIMS particle phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption temperature based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas–particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the

  17. Phase partitioning and volatility of secondary organic aerosol components formed from α-pinene ozonolysis and OH oxidation: the importance of accretion products and other low volatility compounds

    DOE PAGES

    Lopez-Hilfiker, F. D.; Mohr, C.; Ehn, M.; ...

    2015-07-16

    We measured a large suite of gas- and particle-phase multi-functional organic compounds with a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. The instrument was deployed on environmental simulation chambers to study monoterpene oxidation as a secondary organic aerosol (SOA) source. We focus here on results from experiments utilizing an ionization method most selective towards acids (acetate negative ion proton transfer), but our conclusions are based on more general physical and chemical properties of the SOA. Hundreds of compounds were observed in both gas andmore » particle phases, the latter being detected by temperature-programmed thermal desorption of collected particles. Particulate organic compounds detected by the FIGAERO–HR-ToF-CIMS are highly correlated with, and explain at least 25–50 % of, the organic aerosol mass measured by an Aerodyne aerosol mass spectrometer (AMS). Reproducible multi-modal structures in the thermograms for individual compounds of a given elemental composition reveal a significant SOA mass contribution from high molecular weight organics and/or oligomers (i.e., multi-phase accretion reaction products). Approximately 50 % of the HR-ToF-CIMS particle-phase mass is associated with compounds having effective vapor pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. The relative importance of these accretion-type and other extremely low volatility products appears to vary with photochemical conditions. We present a desorption-temperature-based framework for apportionment of thermogram signals into volatility bins. The volatility-based apportionment greatly improves agreement between measured and modeled gas-particle partitioning for select major and minor components of the SOA, consistent with thermal decomposition during desorption causing the

  18. Modeling SOA formation from alkanes and alkenes in chamber experiments: effect of gas/wall partitioning of organic vapors.

    NASA Astrophysics Data System (ADS)

    Stéphanie La, Yuyi; Camredon, Marie; Ziemann, Paul; Ouzebidour, Farida; Valorso, Richard; Madronich, Sasha; Lee-Taylor, Julia; Hodzic, Alma; Aumont, Bernard

    2014-05-01

    Oxidation products of Intermediate Volatility Organic Compounds (IVOC) are expected to be the major precursors of secondary organic aerosols (SOA). Laboratory experiments were conducted this last decade in the Riverside APRC chamber to study IVOC oxidative mechanisms and SOA formation processes for a large set of linear, branched and cyclic aliphatic hydrocarbons (Ziemann, 2011). This dataset are used here to assess the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) (Aumont et al., 2005). The simulated SOA yields agree with the general trends observed in the chamber experiments. They are (i) increasing with the increasing carbon number; (ii) decreasing with increasing methyl branch number; and (iii) increasing for cyclic compounds compared to their corresponding linear analogues. However, simulated SOA yields are systematically overestimated regardless of the precursors, suggesting missing processes in the model. In this study, we assess whether gas-to-wall partitioning of organic vapors can explain these model/observation mismatches (Matsunaga and Ziemann, 2010). First results show that GECKO-A outputs better match the observations when wall uptake of organic vapors is taken into account. Effects of gas/wall partitioning on SOA yields and composition will be presented. Preliminary results suggest that wall uptake is a major process influencing SOA production in the Teflon chambers. References Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach. Atmos.Chem.Phys., 5, 2497-2517 (2005). P. J. Ziemann: Effects of molecular structure on the chemistry of aerosol formation from the OH-radical-initiated oxidation of alkanes and alkenes, Int. Rev.Phys.Chem., 30:2, 161-195 (2011). Matsunaga, A., Ziemann, P. J.: Gas-wall partitioning of organic compounds in a Teflon film

  19. Gas phase emissions from cooking processes and their secondary aerosol production potential

    NASA Astrophysics Data System (ADS)

    Klein, Felix; Platt, Stephen; Bruns, Emily; Termime-roussel, Brice; Detournay, Anais; Mohr, Claudia; Crippa, Monica; Slowik, Jay; Marchand, Nicolas; Baltensperger, Urs; Prevot, Andre; El Haddad, Imad

    2014-05-01

    Long before the industrial evolution and the era of fossil fuels, high concentrations of aerosol particles were alluded to in heavily populated areas, including ancient Rome and medieval London. Recent radiocarbon measurements (14C) conducted in modern megacities came as a surprise: carbonaceous aerosol (mainly organic aerosol, OA), a predominant fraction of particulate matter (PM), remains overwhelmingly non-fossil despite extensive fossil fuel combustion. Such particles are directly emitted (primary OA, POA) or formed in-situ in the atmosphere (secondary OA, SOA) via photochemical reactions of volatile organic compounds (VOCs). Urban levels of non-fossil OA greatly exceed the levels measured in pristine environments strongly impacted by biogenic emissions, suggesting a contribution from unidentified anthropogenic non-fossil sources to urban OA. Positive matrix factorization (PMF) techniques applied to ambient aerosol mass spectrometer (AMS, Aerodyne) data identify primary cooking emissions (COA) as one of the main sources of primary non-fossil OA in major cities like London (Allan et al., 2010), New York (Sun et al., 2011) and Beijing (Huang et al., 2010). Cooking processes can also emit VOCs that can act as SOA precursors, potentially explaining in part the high levels of oxygenated OA (OOA) identified by the AMS in urban areas. However, at present, the chemical nature of these VOCs and their secondary aerosol production potential (SAPP) remain virtually unknown. The approach adopted here involves laboratory quantification of PM and VOC emission factors from the main primary COA emitting processes and their SAPP. Primary emissions from deep-fat frying, vegetable boiling, vegetable frying and meat cooking for different oils, meats and vegetables were analysed under controlled conditions after ~100 times dilution. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a high resolution proton transfer time-of-flight mass spectrometer (PTR

  20. Defense mechanisms of the respiratory system and aerosol production systems.

    PubMed

    Zarogoulidis, Paul; Darwiche, Kaid; Yarmus, Lonny; Spyratos, Dionysios; Secen, Nevena; Hohenforst-Schmidt, Wolfgang; Katsikogiannis, Nikolaos; Huang, Haidong; Gschwendtner, Andreas; Zarogoulidis, Konstantinos

    2014-03-01

    Aerosolized therapies have been used in everyday clinical practice for decades. Experimentation with different delivery systems have led to the creation of aerosolized insulin, antibiotics, gene therapy and chemotherapy. Several of these therapies are already clinically available while others are being investigated in active clinical trials. The main factors affecting the efficiency and safety of the aerosolized therapies are the production of the aerosol, distribution/deposition of the aerosol throughout the lung parenchyma, respiratory defense mechanisms and tissue/pharmaceutical molecule interactions. Current methods of aerosol production and distribution will be presented along with an overview of the respiratory defense mechanisms. In addition, methods of aerosol evaluation in conjunction with a future perspective of the potential development of aerosol therapies will be presented.

  1. SOA multiday growth: Model artifact or reality?

    NASA Astrophysics Data System (ADS)

    Lee-Taylor, J. M.; Madronich, S.; Aumont, B.; Hodzic, A.; Camredon, M.; Valorso, R.

    2013-12-01

    Simulations of SOA gas-particle partitioning with the explicit gas-phase chemical mechanism generator GECKO-A show significant SOA mass growth continuing for several days, even as the initial air parcel is diluted into the regional atmosphere. This result is a robust feature of our model and occurs with both anthropogenic and biogenic precursors. The growth originates from continuing oxidation of gas-phase precursors which persist in equilibrium with the particle phase. This result implies that sources of aerosol precursors could influence the chemical and radiative characteristics of the atmosphere over a wider region than previously imagined, and that SOA measurements near precursor sources may routinely underestimate this influence. It highlights the need to better understand the sink terms in the SOA budget.

  2. SOA from BVOCs in the Southeastern United States

    EPA Science Inventory

    Biogenic hydrocarbons contribute to organic aerosol in the southeast United States. In this work, we represent aerosol formation from the oxidation of isoprene and monoterpenes in CMAQ and compare to data from the Southeast Oxidants and Aerosol Study (SOAS). Sensitivity simulatio...

  3. Role of Aerosol Liquid Water in Secondary Organic Aerosol Formation from Volatile Organic Compounds.

    PubMed

    Faust, Jennifer A; Wong, Jenny P S; Lee, Alex K Y; Abbatt, Jonathan P D

    2017-02-07

    A key mechanism for atmospheric secondary organic aerosol (SOA) formation occurs when oxidation products of volatile organic compounds condense onto pre-existing particles. Here, we examine effects of aerosol liquid water (ALW) on relative SOA yield and composition from α-pinene ozonolysis and the photooxidation of toluene and acetylene by OH. Reactions were conducted in a room-temperature flow tube under low-NOx conditions in the presence of equivalent loadings of deliquesced (∼20 μg m(-3) ALW) or effloresced (∼0.2 μg m(-3) ALW) ammonium sulfate seeds at exactly the same relative humidity (RH = 70%) and state of wall conditioning. We found 13% and 19% enhancements in relative SOA yield for the α-pinene and toluene systems, respectively, when seeds were deliquesced rather than effloresced. The relative yield doubled in the acetylene system, and this enhancement was partially reversible upon drying the prepared SOA, which reduced the yield by 40% within a time scale of seconds. We attribute the high relative yield of acetylene SOA on deliquesced seeds to aqueous partitioning and particle-phase reactions of the photooxidation product glyoxal. The observed range of relative yields for α-pinene, toluene, and acetylene SOA on deliquesced and effloresced seeds suggests that ALW plays a complicated, system-dependent role in SOA formation.

  4. Secondary organic aerosol (trans)formation through aqueous phase guaiacol photonitration: chemical characterization of the products

    NASA Astrophysics Data System (ADS)

    Grgić, Irena; Kitanovski, Zoran; Kroflič, Ana; Čusak, Alen

    2014-05-01

    One of the largest primary sources of organic aerosol in the atmosphere is biomass burning (BB) (Laskin et al. 2009); in Europe its contribution to annual mean of PM10 is between 3 and 14 % (Maenhaut et al. 2012). During the process of wood burning many different products are formed via thermal degradation of wood lignin. Hardwood burning produces mainly syringol (2,6-dimetoxyphenol) derivatives, while softwood burning exclusively guaiacol (2-methoxyphenol) and its derivatives. Taking into account physical properties of methoxyphenols only, their concentrations in atmospheric waters might be underestimated. So, their aqueous phase reactions can be an additional source of SOA, especially in regions under significant influence of wood combustion. An important class of compounds formed during physical and chemical aging of the primary BBA in the atmosphere is nitrocatechols, known as strong absorbers of UV and Vis light (Claeys et al. 2012). Very recently, methyl-nitrocatechols were proposed as suitable markers for highly oxidized secondary BBA (Iinuma et al. 2010, Kitanovski et al. 2012). In the present work, the formation of SOA through aqueous phase photooxidation and nitration of guaiacol was examined. The key objective was to chemically characterize the main low-volatility products and further to check their possible presence in the urban atmospheric aerosols. The aqueous phase reactions were performed in a thermostated reactor under simulated sunlight in the presence of H2O2 and nitrite. Guaiacol reaction products were first concentrated by solid-phase extraction (SPE) and then subjected to semi-preparative liquid chromatography.The main product compounds were fractionated and isolated as pure solids and their structure was further elucidated by using nuclear magnetic resonance spectroscopy (1H, 13C and 2D NMR) and direct infusion negative ion electro-spray ionization tandem mass spectrometry (( )ESI-MS/MS). The main photonitration products of guaiacol (4

  5. Monoterpene oxidation products and organosulfates in aerosols during BEARPEX 2007 and 2009

    NASA Astrophysics Data System (ADS)

    Glasius, Marianne; Kristensen, Kasper; Worton, David R.; Goldstein, Allen H.

    2010-05-01

    Organosulfate esters of oxidation products of monoterpenes and isoprene have been identified in aerosols from both laboratory and field studies. While the exact route of formation of organosulfates is still ambiguous, these compounds pose an interesting coupling between anthropogenic emissions and biogenic oxidation products in secondary organic aerosols (SOA). We present measurements of monoterpene oxidation products, organosulfates and nitroxy organosulfates in aerosols collected during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) in California during late summer 2007 and summer 2009. The study site was located in a Ponderosa pine plantation affected by regional transport of air pollutants. Particles (PM2.5) were collected as one night-time and two daytime samples per day using a high volume sampler. After extraction of filters, polar organic compounds were analysed by HPLC coupled through an electrospray inlet to a quadrupole time-of-flight mass spectrometer (qTOF-MS). Standards of adipic, cis-pinic and pinonic acids were used for quantification, while camphor sulphonic acid was used as a surrogate standard for organosulfate compounds. Organosulfate esters can be identified from their MS-fragments (HSO4- and SO3-) and the isotopic pattern of sulphur. Concentrations of adipic acid and the terpene oxidation products cis-pinic acid and pinonic acid (from α- and β-pinene) were quantified. The relative concentrations between samples of terpenylic acid, diterpenylic acid and 2-hydroxyterpenylic acid were also investigated. Organosulfate esters and nitroxy organosulfate esters of α-pinene, β-pinene, limonene and isoprene, as well as their oxidation products, were identified based on their molecular mass and fragmentation patterns. Concentrations of some nitroxy organosulfate esters generally increased during night compared to day-time. Their formation thus seems to be related to reactions involving nitrate radicals at night-time.

  6. Coherent Evaluation of Aerosol Data Products from Multiple Satellite Sensors

    NASA Technical Reports Server (NTRS)

    Ichoku, Charles

    2011-01-01

    Aerosol retrieval from satellite has practically become routine, especially during the last decade. However, there is often disagreement between similar aerosol parameters retrieved from different sensors, thereby leaving users confused as to which sensors to trust for answering important science questions about the distribution, properties, and impacts of aerosols. As long as there is no consensus, and the inconsistencies are not well characterized and understood, there will be no way of developing reliable model inputs and climate data records from satellite aerosol measurements. Fortunately, the Aerosol Robotic Network (AERONET) is providing well-calibrated globally representative ground-based aerosol measurements corresponding to the satellite-retrieved products. Through a recently developed web-based Multi-sensor Aerosol Products Sampling System (MAPSS), we are utilizing the advantages offered by collocated AERONET and satellite products to characterize and evaluate aerosol retrieval from multiple sensors. Indeed, MAPSS and its companion statistical tool AeroStat are facilitating detailed comparative uncertainty analysis of satellite aerosol measurements from Terra-MODIS, Aqua-MODIS, Terra-MISR, Aura-OMI, Parasol-POLDER, and Calipso-CALIOP. In this presentation, we will describe the strategy of the MAPSS system, its potential advantages for the aerosol community, and the preliminary results of an integrated comparative uncertainly analysis of aerosol products from multiple satellite sensors.

  7. Intermediate Volatility Organic Compound Emissions from On-Road Diesel Vehicles: Chemical Composition, Emission Factors, and Estimated Secondary Organic Aerosol Production.

    PubMed

    Zhao, Yunliang; Nguyen, Ngoc T; Presto, Albert A; Hennigan, Christopher J; May, Andrew A; Robinson, Allen L

    2015-10-06

    Emissions of intermediate-volatility organic compounds (IVOCs) from five on-road diesel vehicles and one off-road diesel engine were characterized during dynamometer testing. The testing evaluated the effects of driving cycles, fuel composition and exhaust aftertreatment devices. On average, more than 90% of the IVOC emissions were not identified on a molecular basis, instead appearing as an unresolved complex mixture (UCM) during gas-chromatography mass-spectrometry analysis. Fuel-based emissions factors (EFs) of total IVOCs (speciated + unspeciated) depend strongly on aftertreatment technology and driving cycle. Total-IVOC emissions from vehicles equipped with catalyzed diesel particulate filters (DPF) are substantially lower (factor of 7 to 28, depending on driving cycle) than from vehicles without any exhaust aftertreatment. Total-IVOC emissions from creep and idle operations are substantially higher than emissions from high-speed operations. Although the magnitude of the total-IVOC emissions can vary widely, there is little variation in the IVOC composition across the set of tests. The new emissions data are combined with published yield data to investigate secondary organic aerosol (SOA) formation. SOA production from unspeciated IVOCs is estimated using surrogate compounds, which are assigned based on gas-chromatograph retention time and mass spectral signature of the IVOC UCM. IVOCs contribute the vast majority of the SOA formed from exhaust from on-road diesel vehicles. The estimated SOA production is greater than predictions by previous studies and substantially higher than primary organic aerosol. Catalyzed DPFs substantially reduce SOA formation potential of diesel exhaust, except at low speed operations.

  8. Production flux of sea spray aerosol

    NASA Astrophysics Data System (ADS)

    de Leeuw, Gerrit; Andreas, Edgar L.; Anguelova, Magdalena D.; Fairall, C. W.; Lewis, Ernie R.; O'Dowd, Colin; Schulz, Michael; Schwartz, Stephen E.

    2011-05-01

    Knowledge of the size- and composition-dependent production flux of primary sea spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea spray drops. This review examines recent research pertinent to SSA production flux, which deals mainly with production of particles with r80 (equilibrium radius at 80% relative humidity) less than 1 μm and as small as 0.01 μm. Production of sea spray particles and its dependence on controlling factors has been investigated in laboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that water-insoluble organic matter contributes substantially to the composition of SSA particles with r80 < 0.25 μm and, in locations with high biological activity, can be the dominant constituent. Order-of-magnitude variation remains in estimates of the size-dependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities such as the volume flux of air bubbles to the surface that are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.

  9. Mass spectra deconvolution of low, medium, and high volatility biogenic secondary organic aerosol.

    PubMed

    Kostenidou, Evangelia; Lee, Byong-Hyoek; Engelhart, Gabriella J; Pierce, Jeffrey R; Pandis, Spyros N

    2009-07-01

    Secondary organic aerosol (SOA) consists of compounds with a wide range of volatilities and its ambient concentration is sensitive to this volatility distribution. Recent field studies have shown that the typical mass spectrum of ambient oxygenated organic aerosol (OOA) as measured by the Aerodyne Aerosol Mass Spectrometer (AMS) is quite different from the SOA mass spectra reported in smog chamber experiments. Part of this discrepancy is due to the dependence of SOA composition on the organic aerosol concentration. High precursor concentrations lead to higher concentrations of the more volatile species in the produced SOA while at lower concentrations the less volatile compounds dominate the SOA composition. alpha-Pinene, beta-pinene, d-limonene, and beta-caryophyllene ozonolysis experiments were performed at moderate concentration levels. Using a thermodenuder the more volatile SOA species were removed achieving even lower SOA concentration. The less volatile fraction was then chemically characterized by an AMS. The signal fraction of m/z44, and thus the concentration of C02+, is significantly higher for the less volatile SOA. High NO(x) conditions result in less oxidized SOA than low NO(x) conditions, while increasing relative humidity levels results in more oxidized products for limonene but has little effect on alpha-and beta-pinene SOA. Combining a smog chamber with a thermodenuder model employing the volatility basis-set framework, the AMS SOA mass spectrum for each experiment and for each precursor is deconvoluted into low, medium, and high volatility component mass spectra. The spectrum of the surrogate component with the lower volatility is quite similar to that of ambient OOA.

  10. Effect of Ammonia on Glyoxal SOA in Inorganic Aqueous Seed Particles

    NASA Astrophysics Data System (ADS)

    Waxman, E.; Volkamer, R. M.; Laskin, A.; Laskin, J.; Koenig, T. K.; Baltensperger, U.; Dommen, J.; Prevot, A. S.; Slowik, J.; Maxut, A.; Noziere, B.; Wang, S.; Yu, J.

    2014-12-01

    Glyoxal (C2H2O2) is a ubiquitous small molecule that is observed in the terrestrial biogenic, urban, marine and arctic atmosphere. It forms secondary organic aerosol (SOA) as a result of multiphase chemical reactions in water. The rate of these reactions is controlled by the effective Henry's law partitioning coefficient (Heff) which is enhanced in the presence of inorganic salts by up to 3 orders of magnitude (Kampf et al., 2013, ES&T). Aerosol particles are among the most concentrated salt solutions on Earth and the SOA formation rate in aerosol water is strongly modified by this 'salting-in' mechanism. We have studied the effect of gas-phase ammonia on the rate of SOA formation in real particles composed of different inorganic salts (sulfate, nitrate, chloride). A series of simulation chamber experiments were conducted at the Paul Scherrer Institut in Switzerland during Summer 2013. The SOA formation rate in experiments with added gas-phase ammonia (NH3) was found to be greatly accelerated compared to experiments without added NH3. Product analysis of particles included online HR-ToF-AMS and offline nano-DESI and LC-MS. We find that imidazole-like oligomer compounds dominate the observed products, rather than high-O/C oligomers containing solely C, H, and O. We further employed isotopically labelled di-substituted 13C glyoxal experiments in order to unambiguously link product formation to glyoxal (and separate it from chamber wall contamination). We present a molecular perspective on the reaction pathways and evaluate the effect of environmental parameters (RH, particle pH, seed chemical composition) on the formation of these imidazole-like oligomer compounds. The implications for SOA formation from photosensitized oxidation chemistry is discussed.

  11. Production Flux of Sea-Spray Aerosol

    NASA Astrophysics Data System (ADS)

    de Leeuw, G.; Andreas, E. L.; Anguelova, M. D.; Fairall, C. W.; Lewis, E. R.; O'Dowd, C.; Schulz, M.; Schwartz, S. E.

    2010-12-01

    Knowledge of the size- and composition-dependent production flux of primary sea-spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea-spray drops. This review examines recent research pertinent to SSA production flux with emphasis on particles with r80 (equilibrium radius at 80% relative humidity) less than 1 µm and as small as 0.01 µm. Production of sea-spray particles and its dependence on controlling factors has been investigated in laboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics, and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that water-insoluble organic matter contributes substantially to the composition of SSA particles with r80 < 0.25 µm and in locations with high biological activity can be the dominant constituent. Order-of-magnitude variation remains in estimates of the size-dependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities, such as the volume flux of air bubbles to the surface, that are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.

  12. Aerosol Production from the Great Lakes Surface

    NASA Astrophysics Data System (ADS)

    Slade, J. H.; Mwaniki, G.; Bertman, S. B.; Vanreken, T. M.; Shepson, P. B.

    2009-12-01

    It is well understood that oceans generate airborne particulate matter from mechanical processes such as sea spray and bubble bursting. These particles are primarily composed of salts and other nonvolatile inorganic material; however, the organic mass fraction can vary by location and the extent of biological activity. The size distributions of aerosols in these environments depend greatly on relative humidity with diameters ranging from typically several hundred nanometers to several micrometers. There has been much less discussion of particle formation from fresh water ecosystems, a hub for organic activity, and thus a more likely medium for organic aerosol production. We investigated particle formation over the Great Lakes during the summer of 2009 as a part of the Community Atmosphere-Biosphere Interactions Experiments (CABINEX) at the University of Michigan Biological Station (UMBS) in Pellston, MI. With a scanning mobility particle sizer (SMPS) aboard Purdue University’s Airborne Laboratory for Atmospheric Research (ALAR) for size-distribution analysis of accumulation-mode aerosol, we conducted vertical profiles above Lake Michigan and the UMBS deciduous forest, and transects across the peninsula between Lakes Michigan and Huron to study particle formation, transport, and deposition. Preliminary results reveal a well-mixed troposphere above the forest with a mode ~0.1 μm, while in several cases, the total particle concentration over Lake Michigan is an order of magnitude greater than over the forest. There is a consistent bimodal distribution of particle sizes over Lake Michigan the lowest of which is centered at ~0.025 μm, suggesting the possibility of new particle formation. This mode is consistent with the presence of breaking waves on the lake’s surface, and this mode and the vertical structure depend greatly on wind speed. We present here evidence for new particle production from breaking waves on fresh water lakes, and discuss the results

  13. To what extent can biogenic SOA be controlled?

    PubMed

    Carlton, Annmarie G; Pinder, Robert W; Bhave, Prakash V; Pouliot, George A

    2010-05-01

    The implicit assumption that biogenic secondary organic aerosol (SOA) is natural and can not be controlled hinders effective air quality management. Anthropogenic pollution facilitates transformation of naturally emitted volatile organic compounds (VOCs) to the particle phase, enhancing the ambient concentrations of biogenic secondary organic aerosol (SOA). It is therefore conceivable that some portion of ambient biogenic SOA can be removed by controlling emissions of anthropogenic pollutants. Direct measurement of the controllable fraction of biogenic SOA is not possible, but can be estimated through 3-dimensional photochemical air quality modeling. To examine this in detail, 22 CMAQ model simulations were conducted over the continental U.S. (August 15 to September 4, 2003). The relative contributions of five emitted pollution classes (i.e., NO(x), NH(3), SO(x), reactive non methane carbon (RNMC) and primary carbonaceous particulate matter (PCM)) on biogenic SOA were estimated by removing anthropogenic emissions of these pollutants, one at a time and all together. Model results demonstrate a strong influence of anthropogenic emissions on predicted biogenic SOA concentrations, suggesting more than 50% of biogenic SOA in the eastern U.S. can be controlled. Because biogenic SOA is substantially enhanced by controllable emissions, classification of SOA as biogenic or anthropogenic based solely on VOC origin is not sufficient to describe the controllable fraction.

  14. Investigations of BVOC-SOA-cloud-climate feedbacks via interactive biogenic emissions using NorESM

    NASA Astrophysics Data System (ADS)

    Alterskjær, Kari; Egill Kristjansson, Jon; Grini, Alf; Iversen, Trond; Kirkevåg, Alf; Olivié, Dirk; Schulz, Michael; Seland, Øyvind

    2016-04-01

    Climate feedbacks represent a large source of uncertainty in future climate projections. One such feedback involves a change in emissions of biogenic volatile organic compounds (BVOCs) under global warming and a subsequent change in cloud radiative effects. Parts of the atmospheric BVOCs will oxidize in the atmosphere, which may reduce their volatility enough to form secondary organic aerosols (SOA). A changed SOA load will affect cloud radiative properties through aerosol-cloud interactions (ACI) and therefore act to reduce or enhance the temperature change resulting from greenhouse gases alone. In order to study this effect, a development version of the Norwegian Earth System Model (NorESM) has been extended to include explicit atmospheric particle nucleation and a treatment of SOA based on work by Risto Makkonen and collaborators. Biogenic sources of monoterpene and isoprene are interactively calculated by the Model of Emissions of Gases and Aerosols from Nature (MEGAN), version 2.1, incorporated into the Community Land Model, version 4.5. Monoterpene and isoprene are oxidized by O3, OH and NO3 to form SOA with a yield of 15 % and 5 % respectively. It is assumed that 50 % of the product from monoterpene ozonolysis is of low enough volatility to nucleate new particles. The remaining oxidized BVOCs condensate onto preexisting particles. The model improvements include three new tracers to account for both SOA and the BVOCs. This allows for transport of both SOA and precursor gases, making it possible for SOA to form above the surface layer of the model. The new SOA treatment also changes the size distribution of most model aerosols due to condensation. Preliminary results from 6-year simulations with prescribed sea surface temperatures show that the present day emissions of both isoprene (435.9 Tg/yr) and monoterpenes (121.4 Tg/yr) are within the range found in other studies. The resulting SOA production is on the order of 77 Tg/yr, also within the range found by

  15. Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid and methylglyoxal

    NASA Astrophysics Data System (ADS)

    Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

    2012-01-01

    Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 μM-10 mM) was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

  16. VOC species and emission inventory from vehicles and their SOA formation potentials estimation in Shanghai, China

    NASA Astrophysics Data System (ADS)

    Huang, C.; Wang, H. L.; Li, L.; Wang, Q.; Lu, Q.; de Gouw, J. A.; Zhou, M.; Jing, S. A.; Lu, J.; Chen, C. H.

    2015-10-01

    Volatile organic compound (VOC) species from vehicle exhausts and gas evaporation were investigated by chassis dynamometer and on-road measurements of nine gasoline vehicles, seven diesel vehicles, five motorcycles, and four gas evaporation samples. The secondary organic aerosol (SOA) mass yields of gasoline, diesel, motorcycle exhausts, and gas evaporation were estimated based on the mixing ratio of measured C2-C12 VOC species and inferred carbon number distributions. High aromatic contents were measured in gasoline exhausts and contributed comparatively more SOA yield. A vehicular emission inventory was compiled based on a local survey of on-road traffic in Shanghai and real-world measurements of vehicle emission factors from previous studies in the cities of China. The inventory-based vehicular organic aerosol (OA) productions to total CO emissions were compared with the observed OA to CO concentrations (ΔOA / ΔCO) in the urban atmosphere. The results indicate that vehicles dominate the primary organic aerosol (POA) emissions and OA production, which contributed about 40 and 60 % of OA mass in the urban atmosphere of Shanghai. Diesel vehicles, which accounted for less than 20 % of vehicle kilometers of travel (VKT), contribute more than 90 % of vehicular POA emissions and 80-90 % of OA mass derived by vehicles in urban Shanghai. Gasoline exhaust could be an important source of SOA formation. Tightening the limit of aromatic content in gasoline fuel will be helpful to reduce its SOA contribution. Intermediate-volatile organic compounds (IVOCs) in vehicle exhausts greatly contribute to SOA formation in the urban atmosphere of China. However, more experiments need to be conducted to determine the contributions of IVOCs to OA pollution in China.

  17. Aircraft observations of water-soluble dicarboxylic acids in the aerosols over China

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Lin; Kawamura, Kimitaka; Qing Fu, Ping; Boreddy, Suresh K. R.; Watanabe, Tomomi; Hatakeyama, Shiro; Takami, Akinori; Wang, Wei

    2016-05-01

    Vertical profiles of dicarboxylic acids, related organic compounds and secondary organic aerosol (SOA) tracer compounds in particle phase have not yet been simultaneously explored in East Asia, although there is growing evidence that aqueous-phase oxidation of volatile organic compounds may be responsible for the elevated organic aerosols (OA) in the troposphere. Here, we found consistently good correlation of oxalic acid, the most abundant individual organic compounds in aerosols globally, with its precursors as well as biogenic-derived SOA compounds in Chinese tropospheric aerosols by aircraft measurements. Anthropogenically derived dicarboxylic acids (i.e., C5 and C6 diacids) at high altitudes were 4-20 times higher than those from surface measurements and even occasionally dominant over oxalic acid at altitudes higher than 2 km, which is in contrast to the predominance of oxalic acid previously reported globally including the tropospheric and surface aerosols. This indicates an enhancement of tropospheric SOA formation from anthropogenic precursors. Furthermore, oxalic acid-to-sulfate ratio maximized at altitudes of ˜ 2 km, explaining aqueous-phase SOA production that was supported by good correlations with predicted liquid water content, organic carbon and biogenic SOA tracers. These results demonstrate that elevated oxalic acid and related SOA compounds from both the anthropogenic and biogenic sources may substantially contribute to tropospheric OA burden over polluted regions of China, implying aerosol-associated climate effects and intercontinental transport.

  18. Aqueous-phase mechanism for secondary organic aerosol formation from isoprene: application to the southeast United States and co-benefit of SO2 emission controls

    NASA Astrophysics Data System (ADS)

    Marais, E. A.; Jacob, D. J.; Jimenez, J. L.; Campuzano-Jost, P.; Day, D. A.; Hu, W.; Krechmer, J.; Zhu, L.; Kim, P. S.; Miller, C. C.; Fisher, J. A.; Travis, K.; Yu, K.; Hanisco, T. F.; Wolfe, G. M.; Arkinson, H. L.; Pye, H. O. T.; Froyd, K. D.; Liao, J.; McNeill, V. F.

    2016-02-01

    Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA), but the mechanism and yields are uncertain. Aerosol is prevailingly aqueous under the humid conditions typical of isoprene-emitting regions. Here we develop an aqueous-phase mechanism for isoprene SOA formation coupled to a detailed gas-phase isoprene oxidation scheme. The mechanism is based on aerosol reactive uptake coefficients (γ) for water-soluble isoprene oxidation products, including sensitivity to aerosol acidity and nucleophile concentrations. We apply this mechanism to simulation of aircraft (SEAC4RS) and ground-based (SOAS) observations over the southeast US in summer 2013 using the GEOS-Chem chemical transport model. Emissions of nitrogen oxides (NOx ≡ NO + NO2) over the southeast US are such that the peroxy radicals produced from isoprene oxidation (ISOPO2) react significantly with both NO (high-NOx pathway) and HO2 (low-NOx pathway), leading to different suites of isoprene SOA precursors. We find a mean SOA mass yield of 3.3 % from isoprene oxidation, consistent with the observed relationship of total fine organic aerosol (OA) and formaldehyde (a product of isoprene oxidation). Isoprene SOA production is mainly contributed by two immediate gas-phase precursors, isoprene epoxydiols (IEPOX, 58 % of isoprene SOA) from the low-NOx pathway and glyoxal (28 %) from both low- and high-NOx pathways. This speciation is consistent with observations of IEPOX SOA from SOAS and SEAC4RS. Observations show a strong relationship between IEPOX SOA and sulfate aerosol that we explain as due to the effect of sulfate on aerosol acidity and volume. Isoprene SOA concentrations increase as NOx emissions decrease (favoring the low-NOx pathway for isoprene oxidation), but decrease more strongly as SO2 emissions decrease (due to the effect of sulfate on aerosol acidity and volume). The US Environmental Protection Agency (EPA) projects 2013-2025 decreases in anthropogenic emissions of

  19. Contribution of carbonyl photochemistry to aging of atmospheric secondary organic aerosol.

    PubMed

    Mang, Stephen A; Henricksen, Dana K; Bateman, Adam P; Andersen, Mads P Sulbaek; Blake, Donald R; Nizkorodov, Sergey A

    2008-09-11

    The photodegradation of secondary organic aerosol (SOA) material by actinic UV radiation was investigated. SOA was generated via the dark reaction of ozone and d-limonene, collected onto quartz-fiber filters, and exposed to wavelength-tunable radiation. Photochemical production of CO was monitored in situ by infrared cavity ring-down spectroscopy. A number of additional gas-phase products of SOA photodegradation were observed by gas chromatography, including methane, ethene, acetaldehyde, acetone, methanol, and 1-butene. The absorption spectrum of SOA material collected onto CaF2 windows was measured and compared with the photolysis action spectrum for the release of CO, a marker for Norrish type-I photocleavage of carbonyls. Both spectra had a band at approximately 300 nm corresponding to the overlapping n --> pi* transitions in nonconjugated carbonyls. The effective extinction coefficient of freshly prepared SOA was estimated to be on the order of 15 L mol(-1) cm(-1) at 300 nm, implying one carbonyl group in every SOA constituent. The absorption by the SOA material slowly increased in the visible and near-UV during storage of SOA in open air in the dark, presumably as a result of condensation reactions that increased the degree of conjugation in the SOA constituents. These observations suggest that photolysis of carbonyl functional groups represents a significant sink for monoterpene SOA compounds in the troposphere, with an estimated lifetime of several hours over the continental United States.

  20. Formation and chemical aging of secondary organic aerosol during the β-caryophyllene oxidation

    NASA Astrophysics Data System (ADS)

    Tasoglou, A.; Pandis, S. N.

    2015-06-01

    The secondary organic aerosol (SOA) production during the oxidation of β-caryophyllene by ozone (O3) and hydroxyl radicals (OH) and the subsequent chemical aging of the products during reactions with OH were investigated. Experiments were conducted with ozone and with hydroxyl radicals at low NOx (zero added NOx) and at high NOx (hundreds of parts per billion). The SOA mass yield at 10 μg m-3 of organic aerosol was 27% for the ozonolysis, 20% for the reaction with OH at low NOx, and 38% at high NOx under dry conditions, 20 °C, and ozone excess. Parameterizations of the fresh SOA yields have been developed. The average fresh SOA atomic O : C ratio varied from 0.24 to 0.34 depending on the oxidant and the NOx level, while the H : C ratio was close to 1.5 for all systems examined. An average density of 1.06 ± 0.1 μg m-3 of the β-caryophyllene SOA was estimated. The exposure to UV light had no effect on the β-caryophyllene SOA concentration and aerosol mass spectrometer (AMS) measurements. The chemical aging of the β-caryophyllene SOA produced was studied by exposing the fresh SOA to high concentrations (107 molecules cm-3) of OH for several hours. These additional reactions increased the SOA concentration by 15-40% and O : C by approximately 25%. A limited number of experiments suggested that there was a significant impact of the relative humidity on the chemical aging of the SOA. The evaporation rates of β-caryophyllene SOA were quantified by using a thermodenuder allowing us to estimate the corresponding volatility distributions and effective vaporization enthalpies.

  1. The MODIS Aerosol Algorithm, Products, Validation and Applications

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Kaufman, Y. J.; Tanre, D.

    2003-01-01

    The MODerate resolution Imaging Spectroradiometer (MODIS) currently aboard both the Terra and Aqua satellites produces a suite of products designed to characterize global aerosol distribution, optical thickness and particle size. Never before has a space-borne instrument been able to provide such detailed information, complementing field and modeling efforts to produce a comprehensive picture of aerosol characteristics. The three years of Terra-MODIS data have been validated by comparing with co-located AERONET observations of aerosol optical thickness and derivations of aerosol size parameters. Some 8000 comparison points located at 133 AERONET sites around the globe show that the MODIS aerosol optical thickness retrievals are accurate to within the pre-launch expectations. MODIS-derived size parameters are also compared with AERONET retrievals and found to agree well for fine-mode dominated aerosol regimes. Aerosol regimes dominated by dust aerosol are less accurate, attributed to what is thought to be nonsphericity. Errors due to nonsphericity will be reduced by introducing a new set of empirical phase functions, derived without any assumptions of particle shape. The major innovation that MODIS bring to the field of remote sensing of aerosol is the measure of particle size and the separation of finemode and coarsemode dominated aerosol regimes. Particle size can separate finemode man-made aerosols created during combustion, from larger natural aerosols originating from salt spray or wind erosion. This separation allows for the calculation of aerosol radiative effect and the estimation of the man-made aerosol radiative forcing. MODIS can also be used in regional studies of aerosol-cloud interaction that affect the global radiative and hydrological cycles.

  2. Chamber studies of SOA formation from aromatic hydrocarbons: observation of limited glyoxal uptake

    NASA Astrophysics Data System (ADS)

    Nakao, S.; Liu, Y.; Tang, P.; Chen, C.-L.; Zhang, J.; Cocker, D. R., III

    2012-05-01

    This study evaluates the significance of glyoxal acting as an intermediate species leading to secondary organic aerosol (SOA) formation from aromatic hydrocarbon photooxidation under humid conditions. Rapid SOA formation from glyoxal uptake onto aqueous (NH4)2SO4 seed particles is observed in agreement with previous studies; however, glyoxal did not partition significantly to SOA (with or without aqueous seed) during aromatic hydrocarbon photooxidation within an environmental chamber (RH less than 80%). Rather, glyoxal influences SOA formation by raising hydroxyl (OH) radical concentrations. Four experimental approaches supporting this conclusion are presented in this paper: (1) increased SOA formation and decreased SOA volatility in the toluene + NOx photooxidation system with additional glyoxal was reproduced by matching OH radical concentrations through H2O2 addition; (2) glyoxal addition to SOA seed formed from toluene + NOx photooxidation did not increase SOA volume under dark; (3) SOA formation from toluene + NOx photooxidation with and without deliquesced (NH4)2SO4 seed resulted in similar SOA growth, consistent with a minor contribution from glyoxal uptake onto deliquesced seed and organic coatings; and (4) the fraction of a C4H9+ fragment (observed by Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer, HR-ToF-AMS) in SOA from 2-tert-butylphenol (BP) oxidation was unchanged in the presence of additional glyoxal despite enhanced SOA formation. This study suggests that glyoxal uptake onto aerosol during the oxidation of aromatic hydrocarbons is more limited than previously thought.

  3. Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior

    SciTech Connect

    Ansari, A.S.; Pandis, S.N.

    2000-01-01

    The hygroscopic nature of atmospheric aerosol has generally been associated with its inorganic fraction. In this study, a group contribution method is used to predict the water absorption of secondary organic aerosol (SOA). Compared against growth measurements of mixed inorganic-organic particles, this method appears to provide a first-order approximation in predicting SOA water absorption. The growth of common SOA species is predicted to be significantly less than common atmospheric inorganic salts such as (NH{sub 4}){sub 2}SO{sub 4} and NaCl. Using this group contribution method as a tool in predicting SOA water absorption, an integrated modeling approach is developed combining available SOA and inorganic aerosol models to predict overall aerosol behavior. The effect of SOA on water absorption and nitrate partitioning between the gas and aerosol phases is determined. On average, it appears that SOA accounts for approximately 7% of total aerosol water and increases aerosol nitrate concentrations by approximately 10%. At high relative humidity and low SOA mass fractions, the role of SOA in nitrate partitioning and its contribution to total aerosol water is negligible. However, the water absorption of SOA appears to be less sensitive to changes in relative humidity than that of inorganic species, and thus at low relative humidity and high SOA mass fraction concentrations, SOA is predicted to account for approximately 20% of total aerosol water and a 50% increase in aerosol nitrate concentrations. These findings could improve the results of modeling studies where aerosol nitrate has often been underpredicted.

  4. Global transformation and fate of SOA: Implications of low-volatility SOA and gas-phase fragmentation reactions

    NASA Astrophysics Data System (ADS)

    Shrivastava, Manish; Easter, Richard C.; Liu, Xiaohong; Zelenyuk, Alla; Singh, Balwinder; Zhang, Kai; Ma, Po-Lun; Chand, Duli; Ghan, Steven; Jimenez, Jose L.; Zhang, Qi; Fast, Jerome; Rasch, Philip J.; Tiitta, Petri

    2015-05-01

    Secondary organic aerosols (SOA) are large contributors to fine-particle loadings and radiative forcing but are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semivolatile versus nonvolatile SOA treatments (based on some of the latest experimental findings) and to investigate the effects of gas-phase fragmentation reactions. The new treatments also track SOA from biomass burning and biofuel, fossil fuel, and biogenic sources. For semivolatile SOA treatments, fragmentation reactions decrease the simulated annual global SOA burden from 7.5 Tg to 1.8 Tg. For the nonvolatile SOA treatment with fragmentation, the burden is 3.1 Tg. Larger differences between nonvolatile and semivolatile SOA (up to a factor of 5) exist in areas of continental outflow over the oceans. According to comparisons with observations from global surface Aerosol Mass Spectrometer measurements and the U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network measurements, the FragNVSOA treatment, which treats SOA as nonvolatile and includes gas-phase fragmentation reactions, agrees best at rural locations. Urban SOA is underpredicted, but this may be due to the coarse model resolution. All three revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the North American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is mainly due to the oxidation of SOA precursor gases from biomass burning, not included in standard CAM5, and long-range transport of biomass burning OA at high altitudes. The revised model configurations that include fragmentation (both semivolatile and nonvolatile SOA) show much better agreement with MODerate resolution Imaging Spectrometers (MODIS) aerosol optical depth data over regions dominated by biomass burning during the summer

  5. Atmospheric oxidation of 1,3-butadiene: characterization of gas and aerosol reaction products and implications for PM2.5

    NASA Astrophysics Data System (ADS)

    Jaoui, M.; Lewandowski, M.; Docherty, K.; Offenberg, J. H.; Kleindienst, T. E.

    2014-12-01

    Secondary organic aerosol (SOA) was generated by irradiating 1,3-butadiene (13BD) in the presence of H2O2 or NOx. Experiments were conducted in a smog chamber operated in either flow or batch mode. A filter/denuder sampling system was used for simultaneously collecting gas- and particle-phase products. The chemical composition of the gas phase and SOA was analyzed using derivative-based methods (BSTFA, BSTFA + PFBHA, or DNPH) followed by gas chromatography-mass spectrometry (GC-MS) or high-performance liquid chromatography (HPLC) analysis of the derivative compounds. The analysis showed the occurrence of more than 60 oxygenated organic compounds in the gas and particle phases, of which 31 organic monomers were tentatively identified. The major identified products include glyceric acid, d-threitol, erythritol, d-threonic acid, meso-threonic acid, erythrose, malic acid, tartaric acid, and carbonyls including glycolaldehyde, glyoxal, acrolein, malonaldehyde, glyceraldehyde, and peroxyacryloyl nitrate (APAN). Some of these were detected in ambient PM2.5 samples, and could potentially serve as organic markers of 13BD. Furthermore, a series of oligoesters were detected and found to be produced through chemical reactions occurring in the aerosol phase between compounds bearing alcoholic groups and compounds bearing acidic groups. SOA was analyzed for organic mass to organic carbon (OM /OC) ratio, effective enthalpy of vaporization (Δ Hvapeff), and aerosol yield. The average OM /OC ratio and SOA density were 2.7 ± 0.09 and 1.2 ± 0.05, respectively. The average Δ Hvapeff was -26.08 ± 1.46 kJ mol-1, a value lower than that of isoprene SOA. The average laboratory SOA yield measured in this study at aerosol mass concentrations between 22.5 and 140.2 μg m-3 was 0.025 ± 0.011, a value consistent with the literature (0.021-0.178). While the focus of this study has been examination of the particle-phase measurements, the gas-phase photooxidation products have also been

  6. Evidence for ambient dark aqueous SOA formation in the Po Valley, Italy

    NASA Astrophysics Data System (ADS)

    Sullivan, Amy P.; Hodas, Natasha; Turpin, Barbara J.; Skog, Kate; Keutsch, Frank N.; Gilardoni, Stefania; Paglione, Marco; Rinaldi, Matteo; Decesari, Stefano; Facchini, Maria Cristina; Poulain, Laurent; Herrmann, Hartmut; Wiedensohler, Alfred; Nemitz, Eiko; Twigg, Marsailidh M.; Collett, Jeffrey L., Jr.

    2016-07-01

    Laboratory experiments suggest that water-soluble products from the gas-phase oxidation of volatile organic compounds can partition into atmospheric waters where they are further oxidized to form low volatility products, providing an alternative route for oxidation in addition to further oxidation in the gas phase. These products can remain in the particle phase after water evaporation, forming what is termed as aqueous secondary organic aerosol (aqSOA). However, few studies have attempted to observe ambient aqSOA. Therefore, a suite of measurements, including near-real-time WSOC (water-soluble organic carbon), inorganic anions/cations, organic acids, and gas-phase glyoxal, were made during the PEGASOS (Pan-European Gas-AeroSOls-climate interaction Study) 2012 campaign in the Po Valley, Italy, to search for evidence of aqSOA. Our analysis focused on four periods: Period A on 19-21 June, Period B on 30 June and 1-2 July, Period C on 3-5 July, and Period D on 6-7 July to represent the first (Period A) and second (Periods B, C, and D) halves of the study. These periods were picked to cover varying levels of WSOC and aerosol liquid water. In addition, back trajectory analysis suggested all sites sampled similar air masses on a given day. The data collected during both periods were divided into times of increasing relative humidity (RH) and decreasing RH, with the aim of diminishing the influence of dilution and mixing on SOA concentrations and other measured variables. Evidence for local aqSOA formation was only observed during Period A. When this occurred, there was a correlation of WSOC with organic aerosol (R2 = 0.84), aerosol liquid water (R2 = 0.65), RH (R2 = 0.39), and aerosol nitrate (R2 = 0.66). Additionally, this was only observed during times of increasing RH, which coincided with dark conditions. Comparisons of WSOC with oxygenated organic aerosol (OOA) factors, determined from application of positive matrix factorization analysis on the aerosol mass

  7. Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation

    NASA Astrophysics Data System (ADS)

    Dommen, J.; Metzger, A.; Duplissy, J.; Kalberer, M.; Alfarra, M. R.; Gascho, A.; Weingartner, E.; Prevot, A. S. H.; Verheggen, B.; Baltensperger, U.

    2006-07-01

    Compounds assigned to be oxidation products of isoprene (2-methyl-1,3-butadiene) have recently been observed in ambient aerosols, suggesting that isoprene might play an important role in secondary organic aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidation of isoprene and NOx in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high molecular weight compounds over the course of 15-hour experiments. Concurrently, the volatility of the SOA decreased markedly as observed by a tandem differential mobility analyzer. The volume fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same experiments. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was observed.

  8. Secondary organic aerosols over oceans via oxidation of isoprene and monoterpenes from Arctic to Antarctic.

    PubMed

    Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; He, Quan-Fu; Zhang, Pengfei

    2013-01-01

    Isoprene and monoterpenes are important precursors of secondary organic aerosols (SOA) in continents. However, their contributions to aerosols over oceans are still inconclusive. Here we analyzed SOA tracers from isoprene and monoterpenes in aerosol samples collected over oceans during the Chinese Arctic and Antarctic Research Expeditions. Combined with literature reports elsewhere, we found that the dominant tracers are the oxidation products of isoprene. The concentrations of tracers varied considerably. The mean average values were approximately one order of magnitude higher in the Northern Hemisphere than in the Southern Hemisphere. High values were generally observed in coastal regions. This phenomenon was ascribed to the outflow influence from continental sources. High levels of isoprene could emit from oceans and consequently have a significant impact on marine SOA as inferred from isoprene SOA during phytoplankton blooms, which may abruptly increase up to 95 ng/m³ in the boundary layer over remote oceans.

  9. Secondary organic aerosol formation initiated by α-terpineol ozonolysis in indoor air.

    PubMed

    Yang, Y; Waring, M S

    2016-12-01

    Secondary organic aerosol (SOA) owing to reactive organic gas (ROG) ozonolysis can be an important indoor particle source. However, SOA formation owing to ozonolysis of α-terpineol, which is emitted by consumer product usage and reacts strongly with ozone, has not been systematically quantified. Therefore, we conducted 21 experiments to investigate the SOA formation initiated by α-terpineol ozonolysis for high (0.84 h(-1) ), moderate (0.61 h(-1) ), and low (0.36 h(-1) ) air exchange rates (AER), which is the frequency with which indoor is replaced by outdoor air. α-Terpineol concentrations of 6.39 to 226 ppb were combined with high ozone (~25 ppm) to ensure rapid and complete ozonolysis. No reactants were replenished, so SOA peaked quickly and then decreased due to AER and surface losses, and peak SOA ranged from 2.03 to 281 μg/m(3) at unit density. SOA mass formation was parameterized with the aerosol mass fraction (AMF), a.k.a. the SOA yield, and AMFs ranged from 0.056 to 0.24. The AMFs strongly and positively correlated with reacted α-terpineol, whereas they weakly and negatively correlated with higher AERs. One-product, two-product, and volatility basis set (VBS) models were fit to the AMF data. Predictive modeling demonstrated that α-terpineol ozonolysis could meaningfully form SOA in indoor air.

  10. Updated aerosol module and its application to simulate secondary organic aerosols during IMPACT campaign May 2008

    NASA Astrophysics Data System (ADS)

    Li, Y. P.; Elbern, H.; Lu, K. D.; Friese, E.; Kiendler-Scharr, A.; Mentel, Th. F.; Wang, X. S.; Wahner, A.; Zhang, Y. H.

    2013-07-01

    The formation of Secondary organic aerosol (SOA) was simulated with the Secondary ORGanic Aerosol Model (SORGAM) by a classical gas-particle partitioning concept, using the two-product model approach, which is widely used in chemical transport models. In this study, we extensively updated SORGAM including three major modifications: firstly, we derived temperature dependence functions of the SOA yields for aromatics and biogenic VOCs (volatile organic compounds), based on recent chamber studies within a sophisticated mathematic optimization framework; secondly, we implemented the SOA formation pathways from photo oxidation (OH initiated) of isoprene; thirdly, we implemented the SOA formation channel from NO3-initiated oxidation of reactive biogenic hydrocarbons (isoprene and monoterpenes). The temperature dependence functions of the SOA yields were validated against available chamber experiments, and the updated SORGAM with temperature dependence functions was evaluated with the chamber data. Good performance was found with the normalized mean error of less than 30%. Moreover, the whole updated SORGAM module was validated against ambient SOA observations represented by the summed oxygenated organic aerosol (OOA) concentrations abstracted from aerosol mass spectrometer (AMS) measurements at a rural site near Rotterdam, the Netherlands, performed during the IMPACT campaign in May 2008. In this case, we embedded both the original and the updated SORGAM module into the EURopean Air pollution and Dispersion-Inverse Model (EURAD-IM), which showed general good agreements with the observed meteorological parameters and several secondary products such as O3, sulfate and nitrate. With the updated SORGAM module, the EURAD-IM model also captured the observed SOA concentrations reasonably well especially those during nighttime. In contrast, the EURAD-IM model before update underestimated the observations by a factor of up to 5. The large improvements of the modeled SOA

  11. Equilibration timescale of atmospheric secondary organic aerosol partitioning

    NASA Astrophysics Data System (ADS)

    Shiraiwa, Manabu; Seinfeld, John H.

    2012-12-01

    Secondary organic aerosol (SOA) formed from partitioning of oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs) accounts for a substantial portion of atmospheric particulate matter. In describing SOA formation, it is generally assumed that VOC oxidation products rapidly adopt gas-aerosol equilibrium. Here we estimate the equilibration timescale, τeq, of SOA gas-particle partitioning using a state-of-the-art kinetic flux model. τeq is found to be of order seconds to minutes for partitioning of relatively high volatility organic compounds into liquid particles, thereby adhering to equilibrium gas-particle partitioning. However, τeq increases to hours or days for organic aerosol associated with semi-solid particles, low volatility, large particle size, and low mass loadings. Instantaneous equilibrium partitioning may lead to substantial overestimation of particle mass concentration and underestimation of gas-phase concentration.

  12. Modeling global organic aerosol formation and growth

    NASA Astrophysics Data System (ADS)

    Tsimpidi, Alexandra; Karydis, Vlasios; Pandis, Spyros; Lelieveld, Jos

    2014-05-01

    A computationally efficient framework for the description of organic aerosol (OA)-gas partitioning and chemical aging has been developed and implemented into the EMAC atmospheric chemistry-climate model. This model simulates the formation of primary (POA) and secondary organic aerosols (SOA) from semi-volatile (SVOC), intermediate-volatile (IVOC) and volatile organic compounds (VOC). POA are divided in two groups with saturation concentrations at 298 K 0.1, 10, 1000, 100000 µg m-3: OA from fossil fuel combustion and biomass burning. The first 2 surrogate species from each group represent the SVOC while the other surrogate species represent the IVOC. Photochemical reactions that change the volatility of the organics in the gas phase are taken into account. The oxidation products from each group of precursors (SVOC, IVOC, and VOC) are lumped into an additional set of oxidized surrogate species (S-SOA, I-SOA, and V-SOA, respectively) in order to track their source of origin. This model is used to i) estimate the relative contributions of SOA and POA to total OA, ii) determine how SOA concentrations are affected by biogenic and anthropogenic emissions, and iii) evaluate the effect of photochemical aging and long-range transport on OA budget over specific regions.

  13. Morphology of mixed primary and secondary organic particles and the adsorption of spectator organic gases during aerosol formation

    PubMed Central

    Vaden, Timothy D.; Song, Chen; Zaveri, Rahul A.; Imre, Dan; Zelenyuk, Alla

    2010-01-01

    Primary organic aerosol (POA) and associated vapors can play an important role in determining the formation and properties of secondary organic aerosol (SOA). If SOA and POA are miscible, POA will significantly enhance SOA formation and some POA vapor will incorporate into SOA particles. When the two are not miscible, condensation of SOA on POA particles forms particles with complex morphology. In addition, POA vapor can adsorb to the surface of SOA particles increasing their mass and affecting their evaporation rates. To gain insight into SOA/POA interactions we present a detailed experimental investigation of the morphologies of SOA particles formed during ozonolysis of α-pinene in the presence of dioctyl phthalate (DOP) particles, serving as a simplified model of hydrophobic POA, using a single-particle mass spectrometer. Ultraviolet laser depth-profiling experiments were used to characterize two different types of mixed SOA/DOP particles: those formed by condensation of the oxidized α-pinene products on size-selected DOP particles and by condensation of DOP on size-selected α-pinene SOA particles. The results show that the hydrophilic SOA and hydrophobic DOP do not mix but instead form layered phases. In addition, an examination of homogeneously nucleated SOA particles formed in the presence of DOP vapor shows them to have an adsorbed DOP coating layer that is ∼4 nm thick and carries 12% of the particles mass. These results may have implications for SOA formation and behavior in the atmosphere, where numerous organic compounds with various volatilities and different polarities are present. PMID:20194795

  14. Secondary Organic Aerosol Formation from 2-Methyl-3-Buten-2-ol Photooxidation: Evidence of Acid-Catalyzed Reactive Uptake of Epoxides

    SciTech Connect

    Zhang, Haofei; Zhang, Zhenfa; Cui, Tianqu; Lin, Ying-Hsuan; Bhathela, Neil A.; Ortega, John; Worton, David; Goldstein, Allen H.; Guenther, Alex B.; Jimenez, Jose L.; Gold, Avram; Surratt, Jason D.

    2014-04-08

    Secondary organic aerosol (SOA) formation from 2-methyl-3-buten-2-ol (MBO) photooxidation has recently been observed in both field and laboratory studies. Similar to isoprene, MBO-derived SOA increases with elevated aerosol acidity in the absence of nitric oxide; therefore, an epoxide intermediate, (3,3-dimethyloxiran-2-yl)methanol (MBO epoxide) was synthesized and tentatively proposed here to explain this enhancement. In the present study, the potential of the synthetic MBO epoxide to form SOA via reactive uptake was systematically examined. SOA was observed only in the presence of acidic aerosols. Major SOA constituents, 2,3-dihydroxyisopentanol (DHIP) and MBO-derived organosulfate isomers, were chemically characterized in both laboratory-generated SOA and in ambient fine aerosols collected from the BEACHON-RoMBAS field campaign during summer 2011, where MBO emissions are substantial. Our results support epoxides as potential products of MBO photooxidation leading to formation of atmospheric SOA and suggest that reactive uptake of epoxides may generally explain acid enhancement of SOA observed from other biogenic hydrocarbons.

  15. Evidence for ambient dark aqueous SOA formation in the Po Valley, Italy

    NASA Astrophysics Data System (ADS)

    Sullivan, A. P.; Hodas, N.; Turpin, B. J.; Skog, K.; Keutsch, F. N.; Gilardoni, S.; Paglione, M.; Rinaldi, M.; Decesari, S.; Facchini, M. C.; Poulain, L.; Herrmann, H.; Wiedensohler, A.; Nemitz, E.; Twigg, M. M.; Collett, J. L., Jr.

    2015-12-01

    Laboratory experiments suggest that water-soluble products from the gas-phase oxidation of volatile organic compounds can partition into atmospheric waters where they are further oxidized to form low volatility products, providing an alternative route for oxidation in addition to further oxidation in the gas-phase. These products can remain in the particle phase after water evaporation forming what is termed as aqueous secondary organic aerosol (aqSOA). However, few studies have attempted to observe ambient aqSOA. Therefore, a suite of measurements, including near real-time WSOC (water-soluble organic carbon), inorganic anions/cations, organic acids, and gas-phase glyoxal, were made during the PEGASOS (Pan-European Gas-AeroSols-climate interaction Study) 2012 campaign in the Po Valley, Italy to search for evidence of aqSOA. Our analysis focused on two specific periods: Period A on 19-21 June and Period B on 3-5 July to represent the first and second halves of the study, respectively. The large scale circulation was predominately from the west in both periods. Plus back trajectory analysis suggested all sites sampled similar air masses during both periods allowing for comparison of Periods A and B. The data collected during both periods were divided into times of increasing relative humidity (RH) and decreasing RH with the aim of diminishing the influence of dilution and mixing on SOA concentrations and other measured variables. Evidence for local aqSOA formation was only observed during Period A. When this occurred, there was a correlation of WSOC with organic aerosol (R2 = 0.86), aerosol liquid water (R2 = 0.69), RH (R2 = 0.45), and aerosol nitrate (R2 = 0.71). Additionally, this was only observed during times of increasing RH, which coincided with dark conditions. Comparisons of WSOC with oxygenated organic aerosol (OOA) factors determined from application of positive matrix factorization analysis on the aerosol mass spectrometer observations of the submicron non

  16. Effect of Humidity on the Composition of Isoprene Photooxidation Secondary Organic Aerosol

    SciTech Connect

    Nguyen, Tran B.; Roach, Patrick J.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Serguei

    2011-07-18

    The effect of relative humidity (RH) on the composition and concentrations of gas-phase products and secondary organic aerosol (SOA) generated from the photooxidation of isoprene under high-NOx conditions was investigated. The yields of most gas-phase products were the same regardless of initial water vapor concentration with exception of hydroxyacetone and glycolaldehyde, which were considerably affected by RH. A significant change was observed in the SOA composition, with many unique condensed-phase products formed under humid (90% RH) vs. dry (<2% RH) conditions, without any observable effect on the rate and extent of the SOA mass growth.

  17. Atmospheric oxidation of 1,3-butadiene: characterization of gas and aerosol reaction products and implication for PM2.5

    NASA Astrophysics Data System (ADS)

    Jaoui, M.; Lewandowski, M.; Docherty, K.; Offenberg, J. H.; Kleindienst, T. E.

    2014-06-01

    Secondary organic aerosol (SOA) was generated by irradiating 1,3-butadiene (13BD) in the presence of H2O2 or NOx. Experiments were conducted in a smog chamber operated in either flow or batch mode. A filter/denuder sampling system was used for simultaneously collecting gas- and particle-phase products. The chemical composition of the gas phase and SOA was analyzed using derivative-based methods (BSTFA, BSTFA + PFBHA, or DNPH) followed by gas chromatography-mass spectrometry (GC-MS) or high-performance liquid chromatography (HPLC) analysis of the derivative compounds. The analysis showed the occurrence of more than 60 oxygenated organic compounds in the gas and particle phases, of which 31 organic monomers were tentatively identified. The major identified products include glyceric acid, d-threitol, erythritol, d-threonic acid, meso-threonic acid, erythrose, malic acid, tartaric acid, and carbonyls including glycolaldehyde, glyoxal, acrolein, malonaldehyde, glyceraldehyde, and peroxyacryloyl nitrate (APAN). Some of these were detected in ambient PM2.5 samples and could potentially serve as organic markers of 1,3-butadiene (13BD). Furthermore, a series of oligoesters were detected and found to be produced from esterification reactions among compounds bearing alcoholic groups and compounds bearing acidic groups. Time profiles are provided for selected compounds. SOA was analyzed for organic mass to organic carbon (OM / OC) ratio, effective enthalpy of vaporization (ΔHvapeff), and aerosol yield. The average OM / OC ratio and SOA density were 2.7 ± 0.09 and 1.2 ± 0.05, respectively. The average ΔHvapeff was 26.1 ± 1.5 kJ mol-1, a value lower than that of isoprene SOA. The average laboratory SOA yield measured in this study at aerosol mass concentrations between 22.5 and 140.2 μg m-3 was 0.025 ± 0.011, a value consistent with the literature (0.021-0.178). While the focus of this study has been examination of the particle-phase measurements, the gas

  18. EVIDENCE FOR ORGANOSULFATES IN SECONDARY ORGANIC AEROSOL

    EPA Science Inventory

    Recent work has shown that particle-phase reactions contribute to the formation of secondary organic aerosol (SOA), with enhancements of SOA yields in the presence of acidic seed aerosol. In this study, the chemical composition of SOA from the photooxidations of α-pinene and isop...

  19. Formation of Organic Tracers for Isoprene SOA under Acidic Conditions

    EPA Science Inventory

    The chemical compositions of a series of secondary organic aerosol (SOA) samples, formed by irradiating mixtures of isoprene and NO in a smog chamber in the absence or presence of acidic aerosols, were analyzed using derivatization-based GC-MS methods. In addition to the known is...

  20. Modeling Organic Aerosols during MILAGRO: Application of the CHIMERE Model and Importance of Biogenic Secondary Organic Aerosols

    SciTech Connect

    Hodzic, Alma; Jimenez, Jose L.; Madronich, Sasha; Aiken, Allison; Bessagnet, Bertrand; Curci, Gabriele; Fast, Jerome D.; Lamarque, J.-F.; Onasch, Timothy B.; Roux, Gregory; Schauer, James J.; Stone, Elizabeth A.

    2009-09-22

    The meso-scale chemistry-transport model CHIMERE is used to assess our understanding of major sources and formation processes leading to a fairly large amount of organic aerosols [OA, including primary OA (POA) and secondary OA (SOA)] observed in Mexico City during the MILAGRO field project (March 2006). Chemical analyses of submicron aerosols from aerosol mass spectrometers (AMS) indicate that organic particles found in the Mexico City basin have a large fraction of oxygenated organic species (OOA), which have strong correspondence with SOA, and that their production actively continues downwind of the city. The SOA formation is modeled here by the first-generation oxidation of anthropogenic (i.e., aromatics, alkanes) and biogenic (i.e., monoterpenes and isoprene) precursors and their partitioning into both organic and aqueous phases. The near-surface model evaluation shows that predicted OA correlates reasonably well with measurements during the campaign, however it remains a factor of 2 lower than the measured total OA. Fairly good agreement is found between predicted and observed POA within the city suggesting that anthropogenic and biomass burning emissions are reasonably captured. Consistent with previous studies in Mexico City, large discrepancies are encountered for SOA species, with a factor of 5-10 model underestimate. When only anthropogenic SOA precursors were considered, the model was able to reproduce within a factor of two the sharp increase in SOA concentrations during the late morning at both urban and near-urban locations. However, predicted SOA concentrations were unrealistically low when photochemistry was not active, especially overnight. These nighttime discrepancies were not significantly reduced when greatly enhanced partitioning to the aerosol phase was assumed. Model sensitivity results suggest that observed nighttime SOA concentrations are strongly influenced by the regional background (~2µg/m3) from biogenic origin, which is transported

  1. MODIS 3km Aerosol Product: Algorithm and Global Perspective

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Mattoo, S.; Levy, R. C.; Munchak, L.

    2013-01-01

    After more than a decade of producing a nominal 10 km aerosol product based on the dark target method, the MODIS aerosol team will be releasing a nominal 3 km product as part of their Collection 6 release. The new product differs from the original 10 km product only in the manner in which reflectance pixels are ingested, organized and selected by the aerosol algorithm. Overall, the 3 km product closely mirrors the 10 km product. However, the finer resolution product is able to retrieve over ocean closer to islands and coastlines, and is better able to resolve fine aerosol features such as smoke plumes over both ocean and land. In some situations, it provides retrievals over entire regions that the 10 km product barely samples. In situations traditionally difficult for the dark target algorithm, such as over bright or urban surfaces the 3 km product introduces isolated spikes of artificially high aerosol optical depth (AOD) that the 10 km algorithm avoids. Over land, globally, the 3 km product appears to be 0.01 to 0.02 higher than the 10 km product, while over ocean, the 3 km algorithm is retrieving a proportionally greater number of very low aerosol loading situations. Based on collocations with ground-based observations for only six months, expected errors associated with the 3 km land product are determined to be greater than for the 10 km product: 0.05 0.25 AOD. Over ocean, the suggestion is for expected errors to be the same as the 10 km product: 0.03 0.05 AOD. The advantage of the product is on the local scale, which will require continued evaluation not addressed here. Nevertheless, the new 3 km product is expected to provide important information complementary to existing satellite-derived products and become an important tool for the aerosol community.

  2. Unspeciated Organic Emissions From Combustion Sources And Their Influence On The Secondary Organic Aerosol Budget In The United States

    NASA Astrophysics Data System (ADS)

    Jathar, S.; Gordon, T.; Hennigan, C. J.; Pye, H. O.; Donahue, N. M.; Adams, P. J.; Robinson, A. L.

    2012-12-01

    Combustion sources are a major source of organic emissions and therefore a potentially important source for secondary organic aerosol (SOA) formation in the atmosphere. Although speciated organic emissions from combustion sources are considered in models to form SOA, a large fraction of the organics are unspeciated. In this work, we analyze data from numerous smog chamber experiments, which photo-oxidized dilute emissions from different combustion sources (on-road gasoline vehicles, aircraft, on-road diesel vehicles, wood burning and open biomass burning), to determine the contribution that unspeciated emissions make to SOA formation. An SOA model based on speciated organics is able to explain, on average, 8-31% of the SOA measured in the experiments. We hypothesize that the remainder results from the gas-phase oxidation of unspeciated emissions, which account on average for 25-75% of the non-methane organic gas (NMOG) emissions. Using the SOA data, we develop, for the first time, source-specific parameterizations to model SOA from unspeciated emissions; all sources seem to have median SOA yields similar to large n-alkanes (C12+). To assess the influence of unspeciated emissions on SOA formation regionally, we use the parameterization to predict SOA production in the United States. Using emissions data collected during the smog chamber experiments and data available in literature, we build a gross inventory for unspeciated emissions in the United States. We discover that unspeciated organics might be included in the current generation of SOA models but misallocated in terms of its SOA potential. The top six combustion sources (on- and off-road gasoline, on- and off-road diesel, open biomass and wood burning) emit 2.61 Tg yr-1 of unspeciated emissions (20% of US anthropogenic VOC emissions from combustion sources) and are estimated to form a minimum of 0.68 Tg yr-1 of SOA; the estimate is a third of the biogenic SOA produced in the US. We predict that accounting for

  3. Atmospheric reactivity of hydroxyl radicals with guaiacol (2-methoxyphenol), a biomass burning emitted compound: Secondary organic aerosol formation and gas-phase oxidation products

    NASA Astrophysics Data System (ADS)

    Lauraguais, Amélie; Coeur-Tourneur, Cécile; Cassez, Andy; Deboudt, Karine; Fourmentin, Marc; Choël, Marie

    2014-04-01

    Methoxyphenols are low molecular weight semi-volatile polar aromatic compounds produced from the pyrolysis of wood lignin. The reaction of guaiacol (2-methoxyphenol) with hydroxyl radicals has been studied in the LPCA simulation chamber at (294 ± 2) K, atmospheric pressure, low relative humidity (RH < 1%) and under high-NOx conditions using CH3ONO as OH source. The aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer); the SOA yields were in the range from 0.003 to 0.87 and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. Transmission (TEM) and Scanning (SEM) Electron Microscopy observations were performed to characterize the physical state of SOA produced from the OH reaction with guaiacol; they display both liquid and solid particles (in an amorphous state). GC-FID (Gas Chromatography - Flame Ionization Detection) and GC-MS (Gas Chromatography - Mass Spectrometry) analysis show the formation of nitroguaiacol isomers as main oxidation products in the gas- and aerosol-phases. In the gas-phase, the formation yields were (10 ± 2) % for 4-nitroguaiacol (1-hydroxy-2-methoxy-4-nitrobenzene; 4-NG) and (6 ± 2) % for 3- or 6-nitroguaiacol (1-hydroxy-2-methoxy-3-nitrobenzene or 1-hydroxy-2-methoxy-6-nitrobenzene; 3/6-NG; the standards are not commercially available so both isomers cannot be distinguished) whereas in SOA their yield were much lower (≤0.1%). To our knowledge, this work represents the first identification of nitroguaiacols as gaseous oxidation products of the OH reaction with guaiacol. As the reactivity of nitroguaiacols with atmospheric oxidants is probably low, we suggest using them as biomass burning emission gas tracers. The atmospheric implications of the guaiacol + OH reaction are also discussed.

  4. Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Shiraiwa, M.; Yee, L. D.; Schilling, K.; Loza, C. L.; Craven, J. S.; Zuend, A.; Ziemann, P. J.; Seinfeld, J.

    2013-12-01

    Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosol (SOA). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multi-generation gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a mid-experiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. The results of the current work have a number of implications for SOA models. While the dynamics of an aerosol size distribution reflects the mechanism of growth, we demonstrate here that it provides a key constraint in interpreting laboratory and ambient SOA formation. This work, although carried out specifically for the long chain alkane, dodecane, is expected to be widely applicable to other major classes of SOA precursors. SOA consists of a myriad of organic compounds containing various functional groups, which can generally undergo heterogeneous/multiphase reactions forming low-volatility products such as oligomers and other high molecular mass compounds. If particle-phase chemistry is indeed

  5. Illuminating the Atmospheric Oxidation Mechanisms, SOA Formation Pathways and Radical Yields of the Monoterpene Myrcene

    NASA Astrophysics Data System (ADS)

    Wyche, Kevin; Carr, Timo; Monks, Paul; Ellis, Andrew; Alfarra, Rami; McFiggans, Gordon; Hamilton, Jacqueline; Ward, Martyn; Boss, William; Camredon, Marie

    2010-05-01

    Biogenic Volatile Organic Compounds (BVOCs) are ubiquitous in the global troposphere, being emitted primarily from terrestrial plant life in significant quantities. Indeed, it is estimated that the total annual emission rate of all (non-methane) BVOCs is roughly ten times that of all anthropogenic volatile organic compounds (Guenther et al., 1995). With the exception of methane, the most dominant species of BVOC, in terms of emission strength, reactivity and their impact upon the atmosphere, are terpenes. Terpenes are a subdivision of BVOCs, composed primarily of hemiterpenes (C5), monoterpenes (C10), sesquiterpenes (C15) and diterpenes (C20). Under troposheric conditions terpenes react via complex and extensive gas phase oxidation pathways, have strong photochemical ozone creation potentials, constitute a significant radical source and are known to generate secondary organic aerosol (SOA) in high yields. At present there exists a certain lack of understanding regarding the oxidation mechanisms of certain terpenes and their role in SOA and radical formation. Consequently, as part of the NERC funded Aerosol Coupling in the Earth's System (ACES) and Total RAdical Production from the OZonolysis of alkenes (TRAPOZ) projects, a comprehensive series of simulation chamber experiments were conducted at the University of Manchester aerosol chamber facility, and at the EUropean PHOto REactor (EUPHORE) in order to investigate the gas phase degradation mechanisms, and SOA and radical formation potentials of a number of atmospherically significant terpenes. Both simulation chambers were highly instrumented during all experiments such that detailed and concomitant gas and aerosol phase measurements were made across a range of conditions. The work presented here describes the findings obtained from both photooxidation and ozonolysis experiments involving the common, but less well studied, aliphatic monoterpene, myrcene. The data presented include NOx and ozone measurements and

  6. Recent Improvements to CALIOP Level 3 Aerosol Profile Product for Global 3-D Aerosol Extinction Characterization

    NASA Astrophysics Data System (ADS)

    Tackett, J. L.; Getzewich, B. J.; Winker, D. M.; Vaughan, M. A.

    2015-12-01

    With nine years of retrievals, the CALIOP level 3 aerosol profile product provides an unprecedented synopsis of aerosol extinction in three dimensions and the potential to quantify changes in aerosol distributions over time. The CALIOP level 3 aerosol profile product, initially released as a beta product in 2011, reports monthly averages of quality-screened aerosol extinction profiles on a uniform latitude/longitude grid for different cloud-cover scenarios, called "sky conditions". This presentation demonstrates improvements to the second version of the product which will be released in September 2015. The largest improvements are the new sky condition definitions which parse the atmosphere into "cloud-free" views accessible to passive remote sensors, "all-sky" views accessible to active remote sensors and "cloudy-sky" views for opaque and transparent clouds which were previously inaccessible to passive remote sensors. Taken together, the new sky conditions comprehensively summarize CALIOP aerosol extinction profiles for a broad range of scientific queries. In addition to dust-only extinction profiles, the new version will include polluted-dust and smoke-only extinction averages. A new method is adopted for averaging dust-only extinction profiles to reduce high biases which exist in the beta version of the level 3 aerosol profile product. This presentation justifies the new averaging methodology and demonstrates vertical profiles of dust and smoke extinction over Africa during the biomass burning season. Another crucial advancement demonstrated in this presentation is a new approach for computing monthly mean aerosol optical depth which removes low biases reported in the beta version - a scenario unique to lidar datasets.

  7. Review of Urban Secondary Organic Aerosol Formation from Gasoline and Diesel Motor Vehicle Emissions.

    PubMed

    Gentner, Drew R; Jathar, Shantanu H; Gordon, Timothy D; Bahreini, Roya; Day, Douglas A; El Haddad, Imad; Hayes, Patrick L; Pieber, Simone M; Platt, Stephen M; de Gouw, Joost; Goldstein, Allen H; Harley, Robert A; Jimenez, Jose L; Prévôt, André S H; Robinson, Allen L

    2017-02-07

    Secondary organic aerosol (SOA) is formed from the atmospheric oxidation of gas-phase organic compounds leading to the formation of particle mass. Gasoline- and diesel-powered motor vehicles, both on/off-road, are important sources of SOA precursors. They emit complex mixtures of gas-phase organic compounds that vary in volatility and molecular structure-factors that influence their contributions to urban SOA. However, the relative importance of each vehicle type with respect to SOA formation remains unclear due to conflicting evidence from recent laboratory, field, and modeling studies. Both are likely important, with evolving contributions that vary with location and over short time scales. This review summarizes evidence, research needs, and discrepancies between top-down and bottom-up approaches used to estimate SOA from motor vehicles, focusing on inconsistencies between molecular-level understanding and regional observations. The effect of emission controls (e.g., exhaust aftertreatment technologies, fuel formulation) on SOA precursor emissions needs comprehensive evaluation, especially with international perspective given heterogeneity in regulations and technology penetration. Novel studies are needed to identify and quantify "missing" emissions that appear to contribute substantially to SOA production, especially in gasoline vehicles with the most advanced aftertreatment. Initial evidence suggests catalyzed diesel particulate filters greatly reduce emissions of SOA precursors along with primary aerosol.

  8. Sensitivity analysis of simulated SOA loadings using a variance-based statistical approach: SENSITIVITY ANALYSIS OF SOA

    SciTech Connect

    Shrivastava, Manish; Zhao, Chun; Easter, Richard C.; Qian, Yun; Zelenyuk, Alla; Fast, Jerome D.; Liu, Ying; Zhang, Qi; Guenther, Alex

    2016-04-08

    We investigate the sensitivity of secondary organic aerosol (SOA) loadings simulated by a regional chemical transport model to 7 selected tunable model parameters: 4 involving emissions of anthropogenic and biogenic volatile organic compounds, anthropogenic semi-volatile and intermediate volatility organics (SIVOCs), and NOx, 2 involving dry deposition of SOA precursor gases, and one involving particle-phase transformation of SOA to low volatility. We adopt a quasi-Monte Carlo sampling approach to effectively sample the high-dimensional parameter space, and perform a 250 member ensemble of simulations using a regional model, accounting for some of the latest advances in SOA treatments based on our recent work. We then conduct a variance-based sensitivity analysis using the generalized linear model method to study the responses of simulated SOA loadings to the tunable parameters. Analysis of SOA variance from all 250 simulations shows that the volatility transformation parameter, which controls whether particle-phase transformation of SOA from semi-volatile SOA to non-volatile is on or off, is the dominant contributor to variance of simulated surface-level daytime SOA (65% domain average contribution). We also split the simulations into 2 subsets of 125 each, depending on whether the volatility transformation is turned on/off. For each subset, the SOA variances are dominated by the parameters involving biogenic VOC and anthropogenic SIVOC emissions. Furthermore, biogenic VOC emissions have a larger contribution to SOA variance when the SOA transformation to non-volatile is on, while anthropogenic SIVOC emissions have a larger contribution when the transformation is off. NOx contributes less than 4.3% to SOA variance, and this low contribution is mainly attributed to dominance of intermediate to high NOx conditions throughout the simulated domain. The two parameters related to dry deposition of SOA precursor gases also have very low contributions to SOA variance

  9. Toxicity of aerosols of sodium reaction products.

    PubMed

    Zwicker, G M; Allen, M D; Stevens, D L

    1979-01-01

    Sodium is used as the heat transfer medium in several new energy technologies such as liquid-metal fast-breeder reactors and solar-thermal collection systems. Because sodium burns in air and reacts violently with water, the potential exists for an airborne release of sodium combustion products and subsequent human exposure. To help evaluate the potential short-term hazard from an accidental sodium fire, male juvenile or adult Wistar rats were exposed to sodium aerosols for 2 hours to determine the dose at which 50 percent of the animals were affected (ED50) for each age group. The estimated ED50 of 510 microgram/l for adults was not significantly different from the estimated ED50 of 489 microgram/l for juveniles. The incidence of acute laryngitis, attributed to exposure, was three times higher for juvenile rats than for adults, and the degree of severity of this lesion was significantly (P less than 0.05) higher for juveniles.

  10. Observational constraints on glyoxal production from isoprene oxidation and its contribution to organic aerosol over the Southeast United States

    NASA Astrophysics Data System (ADS)

    Li, Jingyi; Mao, Jingqiu; Min, Kyung-Eun; Washenfelder, Rebecca A.; Brown, Steven S.; Kaiser, Jennifer; Keutsch, Frank N.; Volkamer, Rainer; Wolfe, Glenn M.; Hanisco, Thomas F.; Pollack, Ilana B.; Ryerson, Thomas B.; Graus, Martin; Gilman, Jessica B.; Lerner, Brian M.; Warneke, Carsten; Gouw, Joost A.; Middlebrook, Ann M.; Liao, Jin; Welti, André; Henderson, Barron H.; McNeill, V. Faye; Hall, Samuel R.; Ullmann, Kirk; Donner, Leo J.; Paulot, Fabien; Horowitz, Larry W.

    2016-08-01

    We use a 0-D photochemical box model and a 3-D global chemistry-climate model, combined with observations from the NOAA Southeast Nexus (SENEX) aircraft campaign, to understand the sources and sinks of glyoxal over the Southeast United States. Box model simulations suggest a large difference in glyoxal production among three isoprene oxidation mechanisms (AM3ST, AM3B, and Master Chemical Mechanism (MCM) v3.3.1). These mechanisms are then implemented into a 3-D global chemistry-climate model. Comparison with field observations shows that the average vertical profile of glyoxal is best reproduced by AM3ST with an effective reactive uptake coefficient γglyx of 2 × 10-3 and AM3B without heterogeneous loss of glyoxal. The two mechanisms lead to 0-0.8 µg m-3 secondary organic aerosol (SOA) from glyoxal in the boundary layer of the Southeast U.S. in summer. We consider this to be the lower limit for the contribution of glyoxal to SOA, as other sources of glyoxal other than isoprene are not included in our model. In addition, we find that AM3B shows better agreement on both formaldehyde and the correlation between glyoxal and formaldehyde (RGF = [GLYX]/[HCHO]), resulting from the suppression of δ-isoprene peroxy radicals. We also find that MCM v3.3.1 may underestimate glyoxal production from isoprene oxidation, in part due to an underestimated yield from the reaction of isoprene epoxydiol (IEPOX) peroxy radicals with HO2. Our work highlights that the gas-phase production of glyoxal represents a large uncertainty in quantifying its contribution to SOA.

  11. ORACLE: a module for the description of ORganic Aerosol Composition and Evolution in the atmosphere

    NASA Astrophysics Data System (ADS)

    Tsimpidi, A. P.; Karydis, V. A.; Pozzer, A.; Pandis, S. N.; Lelieveld, J.

    2014-08-01

    A computationally efficient module for the description of organic aerosol (OA) partitioning and chemical aging has been developed and implemented into the EMAC atmospheric chemistry-climate model. The model simulates the formation of secondary organic aerosol (SOA) from semi-volatile (SVOCs), intermediate-volatility (IVOCs) and volatile organic compounds (VOCs). The model distinguishes SVOCs from biomass burning and all other combustion sources using two surrogate species for each source category with an effective saturation concentration at 298 K of C* = 0.1 and 10 μg m-3. Two additional surrogate species with C* = 103 and 105 μg m-3 are used for the IVOCs emitted by the above two source categories. Gas-phase photochemical reactions that change the volatility of the organics are taken into account. The oxidation products (SOA-sv, SOA-iv, and SOA-v) of each group of precursors (SVOCs, IVOCs, and VOCs) are simulated separately in the module to keep track of their origin. ORACLE efficiently describes the OA composition and evolution in the atmosphere and can be used to (i) estimate the relative contributions of SOA and primary organic aerosol (POA) to total OA, (ii) determine how SOA concentrations are affected by biogenic and anthropogenic emissions, and (iii) evaluate the effects of photochemical aging and long-range transport on the OA budget. Here we estimate that the predicted domain-average global surface OA concentration is 1.5 μg m-3 and consists of 7% POA from fuel combustion, 11% POA from biomass burning, 2% SOA-sv from fuel combustion, 3% SOA-sv from biomass burning, 15% SOA-iv from fuel combustion, 28% SOA-iv from biomass burning, 19% biogenic SOA-v, and 15% anthropogenic SOA-v. The tropospheric burden of OA components is predicted to be 0.23 Tg POA, 0.16 Tg SOA-sv, 1.41 Tg SOA-iv, and 1.2 Tg SOA-v.

  12. Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

    SciTech Connect

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew E.; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-14

    The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  13. Cloud condensation nuclei activity of isoprene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Engelhart, Gabriella J.; Moore, Richard H.; Nenes, Athanasios; Pandis, Spyros N.

    2011-01-01

    This work explores the cloud condensation nuclei (CCN) activity of isoprene secondary organic aerosol (SOA), likely a significant source of global organic particulate matter and CCN, produced from the oxidation with OH from HONO/HOOH photolysis in a temperature-controlled SOA chamber. CCN concentrations, activation diameter, and droplet growth kinetic information were monitored as a function of supersaturation (from 0.3% to 1.5%) for several hours using a cylindrical continuous-flow streamwise thermal gradient CCN counter connected to a scanning mobility particle sizer. The initial SOA concentrations ranged from 2 to 30 μg m-3 and presented CCN activity similar to monoterpene SOA with an activation diameter of 35 nm for 1.5% supersaturation and 72 nm for 0.6% supersaturation. The CCN activity improved slightly in some experiments as the SOA aged chemically and did not depend significantly on the level of NOx during the SOA production. The measured activation diameters correspond to a hygroscopicity parameter κ value of 0.12, similar to κ values of 0.1 ± 0.04 reported for monoterpene SOA. Analysis of the water-soluble carbon extracted from filter samples of the SOA suggest that it has a κ of 0.2-0.3 implying an average molar mass between 90 and 150 g mol-1 (assuming a zero and 5% surface tension reduction with respect to water, respectively). These findings are consistent with known oxidation products of isoprene. Using threshold droplet growth analysis, the CCN activation kinetics of isoprene SOA was determined to be similar to pure ammonium sulfate aerosol.

  14. An amorphous solid state of biogenic secondary organic aerosol particles.

    PubMed

    Virtanen, Annele; Joutsensaari, Jorma; Koop, Thomas; Kannosto, Jonna; Yli-Pirilä, Pasi; Leskinen, Jani; Mäkelä, Jyrki M; Holopainen, Jarmo K; Pöschl, Ulrich; Kulmala, Markku; Worsnop, Douglas R; Laaksonen, Ari

    2010-10-14

    Secondary organic aerosol (SOA) particles are formed in the atmosphere from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs). On a global scale, biogenic VOCs account for about 90% of VOC emissions and of SOA formation (90 billion kilograms of carbon per year). SOA particles can scatter radiation and act as cloud condensation or ice nuclei, and thereby influence the Earth's radiation balance and climate. They consist of a myriad of different compounds with varying physicochemical properties, and little information is available on the phase state of SOA particles. Gas-particle partitioning models usually assume that SOA particles are liquid, but here we present experimental evidence that they can be solid under ambient conditions. We investigated biogenic SOA particles formed from oxidation products of VOCs in plant chamber experiments and in boreal forests within a few hours after atmospheric nucleation events. On the basis of observed particle bouncing in an aerosol impactor and of electron microscopy we conclude that biogenic SOA particles can adopt an amorphous solid-most probably glassy-state. This amorphous solid state should provoke a rethinking of SOA processes because it may influence the partitioning of semi-volatile compounds, reduce the rate of heterogeneous chemical reactions, affect the particles' ability to accommodate water and act as cloud condensation or ice nuclei, and change the atmospheric lifetime of the particles. Thus, the results of this study challenge traditional views of the kinetics and thermodynamics of SOA formation and transformation in the atmosphere and their implications for air quality and climate.

  15. Consideration of HOMs in α- and β-pinene SOA model

    NASA Astrophysics Data System (ADS)

    Gatzsche, Kathrin; Iinuma, Yoshiteru; Mutzel, Anke; Berndt, Torsten; Wolke, Ralf

    2016-04-01

    Secondary organic aerosol (SOA) is the major burden of the atmospheric organic particulate matter with 140 - 910 TgC yr-1 (Hallquist et al., 2009). SOA particles are formed via the oxidation of volatile organic carbons (VOCs), where the volatility of the VOCs is lowered due to the increase in their functionalization as well as their binding ability. Therefore, gaseous compounds can either nucleate to form new particles or condense on existing particles. The framework of SOA formation under natural conditions is very complex, because there are a multitude of gas-phase precursors, atmospheric degradation processes and products after oxidation. A lacking understanding about chemical and physical processes associated with SOA formation makes modeling of SOA processes difficult, leading to discrepancy between measured and modeled global SOA burdens. The present study utilizes a parcel model SPACCIM (SPectral Aerosol Cloud Chemistry Interaction Model, Wolke et al., 2005) that couples a multiphase chemical model with a microphysical model. For SOA modeling a further development of SPACCIM was necessary. Therefore, two components are added (i) a gas-phase chemistry mechanism for the VOC oxidation and (ii) a partitioning approach for the gas-to-particle phase transfer. An aggregated gas-phase chemistry mechanism for α- and β-pinene was adapted from Chen and Griffin (2005). For the phase transfer an absorptive partitioning approach (Pankow, 1994) and a kinetic approach (Zaveri et al., 2014) are implemented. Whereby the kinetic approach serves some advantages. The organic aerosol can be resolved in different size sections, whereby the particle radius is involved in the partitioning equations. The phase state of the organic material and the reactivity of the organic compounds in the particle-phase directly influence the modeled SOA yields. Recently, highly oxidized multifunctional organic compounds (HOMs) were found in the gas phase from lab and field studies. They are also

  16. Secondary organic aerosol production from aqueous reactions of atmospheric phenols with an organic triplet excited state.

    PubMed

    Smith, Jeremy D; Sio, Vicky; Yu, Lu; Zhang, Qi; Anastasio, Cort

    2014-01-21

    Condensed-phase chemistry plays a significant role in the formation and evolution of atmospheric organic aerosols. Past studies of the aqueous photoformation of secondary organic aerosol (SOA) have largely focused on hydroxyl radical oxidation, but here we show that triplet excited states of organic compounds ((3)C*) can also be important aqueous oxidants. We studied the aqueous photoreactions of three phenols (phenol, guaiacol, and syringol) with the aromatic carbonyl 3,4-dimethoxybenzaldehyde (DMB); all of these species are emitted by biomass burning. Under simulated sunlight, DMB forms a triplet excited state that rapidly oxidizes phenols to form low-volatility SOA. Rate constants for these reactions are fast and increase with decreasing pH and increasing methoxy substitution of the phenols. Mass yields of aqueous SOA are near 100% for all three phenols. For typical ambient conditions in areas with biomass combustion, the aqueous oxidation of phenols by (3)C* is faster than by hydroxyl radical, although rates depend strongly on pH, oxidant concentrations, and the identity of the phenol. Our results suggest that (3)C* can be the dominant aqueous oxidant of phenols in areas impacted by biomass combustion and that this is a significant pathway for forming SOA.

  17. Assessing the oxidative potential of isoprene-derived epoxides and secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Kramer, Amanda J.; Rattanavaraha, Weruka; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.; Lin, Ying-Hsuan

    2016-04-01

    Fine particulate matter (PM2.5) is known to contribute to adverse health effects, such as asthma, cardiopulmonary disease, and lung cancer. Secondary organic aerosol (SOA) is a major component of PM2.5 and can be enhanced by atmospheric oxidation of biogenic volatile organic compounds in the presence of anthropogenic pollutants, such as nitrogen oxides (NOx) and sulfur dioxide. However, whether biogenic SOA contributes to adverse health effects remains unclear. The objective of this study was to assess the potential of isoprene-derived epoxides and SOA for generating reactive oxygen species (ROS) in light of the recent recognition that atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol is a major contributor to the global SOA burden. The dithiothreitol (DTT) assay was used to characterize the ROS generation by the isoprene-derived epoxides, trans-β-isoprene epoxydiol (trans-β-IEPOX) and methacrylic acid epoxide (MAE), and their hydrolysis products, the 2-methyltetrol diastereomers (2-MT), 2-methylglyceric acid (2-MG), their organosulfate derivatives, as well as an isoprene-derived hydroxyhydroperoxide (ISOPOOH). In addition, ROS generation potential was evaluated for total SOA produced from photooxidation of isoprene and methacrolein (MACR) as well as from the reactive uptake of trans-β-IEPOX and MAE onto acidified sulfate aerosol. The high-NOx regime, which yields 2-MG-, MAE- and MACR-derived SOA has a higher ROS generation potential than the low-NOx regime, which yields 2-MT, IEPOX- and isoprene-derived SOA. ISOPOOH has an ROS generation potential similar to 1,4-naphthoquinone (1,4-NQ), suggesting a significant contribution of aerosol-phase organic peroxides to PM oxidative potential. MAE- and MACR-derived SOA show equal or greater ROS generation potential than reported in studies on diesel exhaust PM, highlighting the importance of a comprehensive investigation of the toxicity of isoprene-derived SOA.

  18. Multi-tiered S-SOA, Parameter-Driven New Islamic Syariah Products of Holistic Islamic Banking System (HiCORE): Virtual Banking Environment

    NASA Astrophysics Data System (ADS)

    Halimah, B. Z.; Azlina, A.; Sembok, T. M.; Sufian, I.; Sharul Azman, M. N.; Azuraliza, A. B.; Zulaiha, A. O.; Nazlia, O.; Salwani, A.; Sanep, A.; Hailani, M. T.; Zaher, M. Z.; Azizah, J.; Nor Faezah, M. Y.; Choo, W. O.; Abdullah, Chew; Sopian, B.

    The Holistic Islamic Banking System (HiCORE), a banking system suitable for virtual banking environment, created based on universityindustry collaboration initiative between Universiti Kebangsaan Malaysia (UKM) and Fuziq Software Sdn Bhd. HiCORE was modeled on a multitiered Simple - Services Oriented Architecture (S-SOA), using the parameterbased semantic approach. HiCORE's existence is timely as the financial world is looking for a new approach to creating banking and financial products that are interest free or based on the Islamic Syariah principles and jurisprudence. An interest free banking system has currently caught the interest of bankers and financiers all over the world. HiCORE's Parameter-based module houses the Customer-information file (CIF), Deposit and Financing components. The Parameter based module represents the third tier of the multi-tiered Simple SOA approach. This paper highlights the multi-tiered parameter- driven approach to the creation of new Islamiic products based on the 'dalil' (Quran), 'syarat' (rules) and 'rukun' (procedures) as required by the syariah principles and jurisprudence reflected by the semantic ontology embedded in the parameter module of the system.

  19. Characterizing the Amount and Chemistry of Biogenic SOA Formation from Pine Forest Air Using a Flow Reactor

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Ortega, A. M.; Campuzano Jost, P.; Day, D. A.; Fry, J.; Zarzana, K. J.; Draper, D. C.; Brown, S. S.; Kaser, L.; Karl, T.; Jud, W.; Hansel, A.; Hodzic, A.; Dube, W. P.; Wagner, N. L.; Brune, W. H.; Jimenez, J. L.

    2013-12-01

    The amount and chemistry of biogenic secondary organic aerosol (SOA) formation was characterized as a function of oxidant exposure using a Potential Aerosol Mass (PAM) oxidative flow reactor, sampling air in a terpene- and MBO-dominated pine forest during the 2011 BEACHON-RoMBAS field campaign at the U.S. Forest Service Manitou Forest Experimental Observatory in the Colorado Rocky Mountains. In the reactor, a chosen oxidant (OH, O3, or NO3) was generated and stepped over a range of values up to 10,000 times ambient levels, accelerating the gas-phase and heterogeneous oxidative aging of volatile organic compounds (VOCs), inorganic gases, and preexisting aerosol. The resulting SOA formation was measured using an Aerodyne HR-ToF-AMS, a TSI SMPS and a PTR-TOF-MS. Oxidative processing in the flow reactor was equivalent to a few hours up to ~20 days of atmospheric aging during the ~4-min reactor residence time. During BEACHON-RoMBAS, OH oxidation led to a net production of up to several μg/m3 of SOA at intermediate exposures (1-10 equivalent days) but resulted in net loss of OA mass (up to ~30%) at higher OH exposures (10-20 equivalent days), demonstrating the competing effects of functionalization/condensation vs. fragmentation/evaporation reactions as OH exposure increased. O3 and NO3 oxidation led to smaller (up to 0.5 μg/m3) SOA production, and loss of SOA mass due to fragmentation reactions was not observed. OH oxidation resulted in f44 vs. f43 and Van Krevelen diagram (H:C vs. O:C) slopes similar to ambient oxidation, suggesting the flow reactor oxidation pathways are similar to those in ambient air. Organic nitrate SOA production was observed from NO3 radical oxidation only. New particle formation was observed from OH oxidation, but not O3 or NO3 oxidation under our experimental conditions. An enhancement of SOA production under the influence of anthropogenic pollution (Denver) was also observed. High-resolution AMS measurements showed that the O:C and H

  20. Global transformation and fate of SOA: Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions

    SciTech Connect

    Shrivastava, ManishKumar B.; Easter, Richard C.; Liu, Xiaohong; Zelenyuk, Alla; Singh, Balwinder; Zhang, Kai; Ma, Po-Lun; Chand, Duli; Ghan, Steven J.; Jiminez, J. L.; Zhang, Qibin; Fast, Jerome D.; Rasch, Philip J.; Tiitta, P.

    2015-05-16

    Secondary organic aerosols (SOA) are large contributors to fine particle loadings and radiative forcing, but are often represented crudely in global models. We have implemented three new detailed SOA treatments within the Community Atmosphere Model version 5 (CAM5) that allow us to compare the semi-volatile versus non-volatile SOA treatments (based on some of the latest experimental findings) and also investigate the effects of gas-phase fragmentation reactions. For semi-volatile SOA treatments, fragmentation reactions decrease simulated SOA burden from 7.5 Tg to 1.8 Tg. For the non-volatile SOA treatment with fragmentation, the burden is 3.1 Tg. Larger differences between non-volatile and semi-volatile SOA (upto a factor of 5) correspond to continental outflow over the oceans. Compared to a global dataset of surface Aerosol Mass Spectrometer measurements and the US IMPROVE network measurements, the non-volatile SOA with fragmentation treatment (FragNVSOA) agrees best at rural locations. Urban SOA is under-predicted but this may be due to the coarse model resolution. All our three revised treatments show much better agreement with aircraft measurements of organic aerosols (OA) over the N. American Arctic and sub-Arctic in spring and summer, compared to the standard CAM5 formulation. This is due to treating SOA precursor gases from biomass burning, and long-range transport of biomass burning OA at elevated levels. The revised model configuration that include fragmentation (both semi-volatile and non-volatile SOA) show much better agreement with MODIS AOD data over regions dominated by biomass burning during the summer, and predict biomass burning as the largest global source of OA followed by biogenic and anthropogenic sources. The non-volatile and semi-volatile configuration predict the direct radiative forcing of SOA as -0.5 W m-2 and -0.26 W m-2 respectively, at top of the atmosphere, which are higher than previously estimated by most models, but in reasonable

  1. In vitro exposure to isoprene-derived secondary organic aerosol by direct deposition and its effects on COX-2 and IL-8 gene expression

    NASA Astrophysics Data System (ADS)

    Arashiro, Maiko; Lin, Ying-Hsuan; Sexton, Kenneth G.; Zhang, Zhenfa; Jaspers, Ilona; Fry, Rebecca C.; Vizuete, William G.; Gold, Avram; Surratt, Jason D.

    2016-11-01

    Atmospheric oxidation of isoprene, the most abundant non-methane hydrocarbon emitted into Earth's atmosphere primarily from terrestrial vegetation, is now recognized as a major contributor to the global secondary organic aerosol (SOA) burden. Anthropogenic pollutants significantly enhance isoprene SOA formation through acid-catalyzed heterogeneous chemistry of epoxide products. Since isoprene SOA formation as a source of fine aerosol is a relatively recent discovery, research is lacking on evaluating its potential adverse effects on human health. The objective of this study was to examine the effect of isoprene-derived SOA on inflammation-associated gene expression in human lung cells using a direct deposition exposure method. We assessed altered expression of inflammation-related genes in human bronchial epithelial cells (BEAS-2B) exposed to isoprene-derived SOA generated in an outdoor chamber facility. Measurements of gene expression of known inflammatory biomarkers interleukin 8 (IL-8) and cyclooxygenase 2 (COX-2) in exposed cells, together with complementary chemical measurements, showed that a dose of 0.067 µg cm-2 of SOA from isoprene photooxidation leads to statistically significant increases in IL-8 and COX-2 mRNA levels. Resuspension exposures using aerosol filter extracts corroborated these findings, supporting the conclusion that isoprene-derived SOA constituents induce the observed changes in mRNA levels. The present study is an attempt to examine the early biological responses of isoprene SOA exposure in human lung cells.

  2. Limited effect of anthropogenic nitrogen oxides on secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Unger, N.; Hodzic, A.; Emmons, L.; Knote, C.; Tilmes, S.; Lamarque, J.-F.; Yu, P.

    2015-12-01

    Globally, secondary organic aerosol (SOA) is mostly formed from emissions of biogenic volatile organic compounds (VOCs) by vegetation, but it can be modified by human activities as demonstrated in recent research. Specifically, nitrogen oxides (NOx = NO + NO2) have been shown to play a critical role in the chemical formation of low volatility compounds. We have updated the SOA scheme in the global NCAR (National Center for Atmospheric Research) Community Atmospheric Model version 4 with chemistry (CAM4-chem) by implementing a 4-product volatility basis set (VBS) scheme, including NOx-dependent SOA yields and aging parameterizations. Small differences are found for the no-aging VBS and 2-product schemes; large increases in SOA production and the SOA-to-OA ratio are found for the aging scheme. The predicted organic aerosol amounts capture both the magnitude and distribution of US surface annual mean measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network by 50 %, and the simulated vertical profiles are within a factor of 2 compared to aerosol mass spectrometer (AMS) measurements from 13 aircraft-based field campaigns across different regions and seasons. We then perform sensitivity experiments to examine how the SOA loading responds to a 50 % reduction in anthropogenic nitric oxide (NO) emissions in different regions. We find limited SOA reductions of 0.9-5.6, 6.4-12.0 and 0.9-2.8 % for global, southeast US and Amazon NOx perturbations, respectively. The fact that SOA formation is almost unaffected by changes in NOx can be largely attributed to a limited shift in chemical regime, to buffering in chemical pathways (low- and high-NOx pathways, O3 versus NO3-initiated oxidation) and to offsetting tendencies in the biogenic versus anthropogenic SOA responses.

  3. Limited effect of anthropogenic nitrogen oxides on secondary organic aerosol formation

    DOE PAGES

    Zheng, Y.; Unger, N.; Hodzic, A.; ...

    2015-12-08

    Globally, secondary organic aerosol (SOA) is mostly formed from emissions of biogenic volatile organic compounds (VOCs) by vegetation, but it can be modified by human activities as demonstrated in recent research. Specifically, nitrogen oxides (NOx = NO + NO2) have been shown to play a critical role in the chemical formation of low volatility compounds. We have updated the SOA scheme in the global NCAR (National Center for Atmospheric Research) Community Atmospheric Model version 4 with chemistry (CAM4-chem) by implementing a 4-product volatility basis set (VBS) scheme, including NOx-dependent SOA yields and aging parameterizations. Small differences are found for themore » no-aging VBS and 2-product schemes; large increases in SOA production and the SOA-to-OA ratio are found for the aging scheme. The predicted organic aerosol amounts capture both the magnitude and distribution of US surface annual mean measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network by 50 %, and the simulated vertical profiles are within a factor of 2 compared to aerosol mass spectrometer (AMS) measurements from 13 aircraft-based field campaigns across different regions and seasons. We then perform sensitivity experiments to examine how the SOA loading responds to a 50 % reduction in anthropogenic nitric oxide (NO) emissions in different regions. We find limited SOA reductions of 0.9–5.6, 6.4–12.0 and 0.9–2.8 % for global, southeast US and Amazon NOx perturbations, respectively. The fact that SOA formation is almost unaffected by changes in NOx can be largely attributed to a limited shift in chemical regime, to buffering in chemical pathways (low- and high-NOx pathways, O3 versus NO3-initiated oxidation) and to offsetting tendencies in the biogenic versus anthropogenic SOA responses.« less

  4. Can scooter emissions dominate urban organic aerosol?

    NASA Astrophysics Data System (ADS)

    El Haddad, Imad; Platt, Stephen; Huang, Ru-Jin; Zardini, Alessandro; Clairotte, Micheal; Pieber, Simone; Pfaffenberger, Lisa; Fuller, Steve; Hellebust, Stig; Temime-Roussel, Brice; Slowik, Jay; Chirico, Roberto; Kalberer, Markus; Marchand, Nicolas; Dommen, Josef; Astorga, Covadonga; Baltensperger, Urs; Prevot, Andre

    2014-05-01

    In urban areas, where the health impact of pollutants increases due to higher population density, traffic is a major source of ambient organic aerosol (OA). A significant fraction of OA from traffic is secondary, produced via the reaction of exhaust volatile organic compounds (VOCs) with atmospheric oxidants. Secondary OA (SOA) has not been systematically assessed for different vehicles and driving conditions and thus its relative importance compared to directly emitted, primary OA (POA) is unknown, hindering the design of effective vehicle emissions regulations. 2-stroke (2S) scooters are inexpensive and convenient and as such a popular means of transportation globally, particularly in Asia. European regulations for scooters are less stringent than for other vehicles and thus primary particulate emissions and SOA precursor VOCs from 2S engines are estimated to be much higher. Assessing the effects of scooters on public health requires consideration of both POA, and SOA production. Here, we quantify POA emission factors and potential SOA EFs from 2S scooters, and the effect of using aromatic free fuel instead of standard gasoline thereon. During the tests, Euro 1 and Euro 2 2S scooters were run in idle or simulated low power conditions. Emissions from a Euro 2 2S scooter were also sampled during regulatory driving cycles on a chassis dynamometer. Vehicle exhaust was introduced into smog chambers, where POA emission and SOA production were quantified using a high-resolution time-of-flight aerosol mass spectrometer. A high resolution proton transfer time-of-flight mass spectrometer was used to investigate volatile organic compounds and a suite of instruments was utilized to quantify CO, CO2, O3, NOX and total hydrocarbons. We show that the oxidation of VOCs in the exhaust emissions of 2S scooters produce significant SOA, exceeding by up to an order of magnitude POA emissions. By monitoring the decay of VOC precursors, we show that SOA formation from 2S scooter

  5. Simulations of organic aerosol concentrations in Mexico City using the WRF-CHEM model during the MCMA-2006/MILAGRO campaign

    NASA Astrophysics Data System (ADS)

    Li, G.; Zavala, M.; Lei, W.; Tsimpidi, A. P.; Karydis, V. A.; Pandis, S. N.; Molina, L. T.

    2010-12-01

    Organic aerosol concentrations are simulated using the WRF-CHEM model in Mexico City during the period from 24 to 29 March in association with the MILAGRO-2006 campaign. Two approaches are employed to predict the variation and spatial distribution of the organic aerosol concentrations: (1) a traditional 2-product secondary organic aerosol (SOA) model with non-volatile primary organic aerosols (POA); (2) a non-traditional SOA model including the volatility basis-set modeling method in which primary organic components are assumed to be semi-volatile and photochemically reactive and are distributed in logarithmically spaced volatility bins. The MCMA 2006 official emission inventory is used in simulations and the POA emissions are modified and distributed by volatility based on dilution experiments for the non-traditional SOA model. The model results are compared to the Aerosol Mass Spectrometry (AMS) observations analyzed using the Positive Matrix Factorization (PMF) technique at an urban background site (T0) and a suburban background site (T1) in Mexico City. The traditional SOA model frequently underestimates the observed POA concentrations during rush hours and overestimates the observations in the rest of the time in the city. The model also substantially underestimates the observed SOA concentrations, particularly during daytime, and only produces 21% and 25% of the observed SOA mass in the suburban and urban area, respectively. The non-traditional SOA model performs well in simulating the POA variation, but still overestimates during daytime in the urban area. The SOA simulations are significantly improved in the non-traditional SOA model compared to the traditional SOA model and the SOA production is increased by more than 100% in the city. However, the underestimation during daytime is still salient in the urban area and the non-traditional model also fails to reproduce the high level of SOA concentrations in the suburban area. In the non-traditional SOA model

  6. Constraining uncertainties in particle-wall deposition correction during SOA formation in chamber experiments

    NASA Astrophysics Data System (ADS)

    Nah, Theodora; McVay, Renee C.; Pierce, Jeffrey R.; Seinfeld, John H.; Ng, Nga L.

    2017-02-01

    The effect of vapor-wall deposition on secondary organic aerosol (SOA) formation has gained significant attention; however, uncertainties in experimentally derived SOA mass yields due to uncertainties in particle-wall deposition remain. Different approaches have been used to correct for particle-wall deposition in SOA formation studies, each having its own set of assumptions in determining the particle-wall loss rate. In volatile and intermediate-volatility organic compound (VOC and IVOC) systems in which SOA formation is governed by kinetically limited growth, the effect of vapor-wall deposition on SOA mass yields can be constrained by using high surface area concentrations of seed aerosol to promote the condensation of SOA-forming vapors onto seed aerosol instead of the chamber walls. However, under such high seed aerosol levels, the presence of significant coagulation may complicate the particle-wall deposition correction. Here, we present a model framework that accounts for coagulation in chamber studies in which high seed aerosol surface area concentrations are used. For the α-pinene ozonolysis system, we find that after accounting for coagulation, SOA mass yields remain approximately constant when high seed aerosol surface area concentrations ( ≥ 8000 µm2 cm-3) are used, consistent with our prior study (Nah et al., 2016) showing that α-pinene ozonolysis SOA formation is governed by quasi-equilibrium growth. In addition, we systematically assess the uncertainties in the calculated SOA mass concentrations and yields between four different particle-wall loss correction methods over the series of α-pinene ozonolysis experiments. At low seed aerosol surface area concentrations (< 3000 µm2 cm-3), the SOA mass yields at peak SOA growth obtained from the particle-wall loss correction methods agree within 14 %. However, at high seed aerosol surface area concentrations ( ≥ 8000 µm2 cm-3), the SOA mass yields at peak SOA growth obtained from different particle

  7. Silicon production in an aerosol reactor

    NASA Technical Reports Server (NTRS)

    Wu, J. J.; Alam, M. K.; Johnson, B. E.; Flagan, R. C.

    1984-01-01

    An aerosol reactor for the growth of large silicon particles by silane pyrolysis was shown to demonstrate the following properties: (1) generate seed particles by pyrolysis of a small amount of silane; (2) mix seed aerosol with primary silane flow, limiting number concentration such that the amount of silane is sufficient to grow the desired size of particles from the seed; and (3) react the silane at a rate which is controlled such that the seed particles scavenge the condensible vapors rapidly enough to inhibit further nucleation.

  8. Determination of isoprene and alpha-/beta-pinene oxidation products in boreal forest aerosols from Hyytiälä, Finland: diel variations and possible link with particle formation events.

    PubMed

    Kourtchev, I; Ruuskanen, T M; Keronen, P; Sogacheva, L; Dal Maso, M; Reissell, A; Chi, X; Vermeylen, R; Kulmala, M; Maenhaut, W; Claeys, M

    2008-01-01

    Biogenic volatile organic compounds (VOCs), such as isoprene and alpha-/beta-pinene, are photo-oxidized in the atmosphere to non-volatile species resulting in secondary organic aerosol (SOA). The goal of this study was to examine time trends and diel variations of oxidation products of isoprene and alpha-/beta-pinene in order to investigate whether they are linked with meteorological parameters or trace gases. Separate day-night aerosol samples (PM(1)) were collected in a Scots pine dominated forest in southern Finland during 28 July-11 August 2005 and analyzed with gas chromatography/mass spectrometry (GC/MS). In addition, inorganic trace gases (SO(2), CO, NO(x), and O(3)), meteorological parameters, and the particle number concentration were monitored. The median total concentration of terpenoic acids (i.e., pinic acid, norpinic acid, and two novel compounds, 3-hydroxyglutaric acid and 2-hydroxy-4-isopropyladipic acid) was 65 ng m(-3), while that of isoprene oxidation products (i.e., 2-methyltetrols and C(5) alkene triols) was 17.2 ng m(-3). The 2-methyltetrols exhibited day/night variations with maxima during day-time, while alpha-/beta-pinene oxidation products did not show any diel variation. The sampling period was marked by a relatively high condensation sink, caused by pre-existing aerosol particles, and no nucleation events. In general, the concentration trends of the SOA compounds reflected those of the inorganic trace gases, meteorological parameters, and condensation sink. Both the isoprene and alpha-/beta-pinene SOA products were strongly influenced by SO(2), which is consistent with earlier reports that acidity plays a role in SOA formation. The results support previous proposals that oxygenated VOCs contribute to particle growth processes above boreal forest.

  9. SOA formation from the photooxidation of α-pinene: systematic exploration of the simulation of chamber data

    NASA Astrophysics Data System (ADS)

    McVay, Renee C.; Zhang, Xuan; Aumont, Bernard; Valorso, Richard; Camredon, Marie; La, Yuyi S.; Wennberg, Paul O.; Seinfeld, John H.

    2016-03-01

    Chemical mechanisms play an important role in simulating the atmospheric chemistry of volatile organic compound oxidation. Comparison of mechanism simulations with laboratory chamber data tests our level of understanding of the prevailing chemistry as well as the dynamic processes occurring in the chamber itself. α-Pinene photooxidation is a well-studied system experimentally, for which detailed chemical mechanisms have been formulated. Here, we present the results of simulating low-NO α-pinene photooxidation experiments conducted in the Caltech chamber with the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) under varying concentrations of seed particles and OH levels. Unexpectedly, experiments conducted at low and high OH levels yield the same secondary organic aerosol (SOA) growth, whereas GECKO-A predicts greater SOA growth under high OH levels. SOA formation in the chamber is a result of a competition among the rates of gas-phase oxidation to low-volatility products, wall deposition of these products, and condensation into the aerosol phase. Various processes - such as photolysis of condensed-phase products, particle-phase dimerization, and peroxy radical autoxidation - are explored to rationalize the observations. In order to explain the observed similar SOA growth at different OH levels, we conclude that vapor wall loss in the Caltech chamber is likely of order 10-5 s-1, consistent with previous experimental measurements in that chamber. We find that GECKO-A tends to overpredict the contribution to SOA of later-generation oxidation products under high-OH conditions. Moreover, we propose that autoxidation may alternatively resolve some or all of the measurement-model discrepancy, but this hypothesis cannot be confirmed until more explicit mechanisms are established for α-pinene autoxidation. The key role of the interplay among oxidation rate, product volatility, and vapor-wall deposition in chamber experiments is

  10. Chemical insights, explicit chemistry and yields of secondary organic aerosol from methylglyoxal and glyoxal

    NASA Astrophysics Data System (ADS)

    Lim, Y. B.; Tan, Y.; Turpin, B. J.

    2013-02-01

    Atmospherically abundant, volatile water soluble organic compounds formed through gas phase chemistry (e.g., glyoxal (C2), methylglyoxal (C3) and acetic acid) have great potential to form secondary organic aerosol (SOA) via aqueous chemistry in clouds, fogs and wet aerosols. This paper (1) provides chemical insights into aqueous-phase OH radical-initiated reactions leading to SOA formation from methylglyoxal and (2) uses this and a previously published glyoxal mechanism (Lim et al., 2010) to provide SOA yields for use in chemical transport models. Detailed reaction mechanisms including peroxy radical chemistry and a full kinetic model for aqueous photochemistry of acetic acid and methylglyoxal are developed and validated by comparing simulations with the experimental results from previous studies (Tan et al., 2010, 2012). This new methylglyoxal model is then combined with the previous glyoxal model (Lim et al., 2010), and is used to simulate the profiles of products and to estimate SOA yields. At cloud relevant concentrations (∼ 10-6-∼ 10-3 M; Munger et al., 1995) of glyoxal and methylglyoxal, the major photooxidation products are oxalic acid and pyruvic acid, and simulated SOA yields (by mass) are ∼ 120% for glyoxal and ∼ 80% for methylglyoxal. Oligomerization of unreacted aldehydes during droplet evaporation could enhance yields. In wet aerosols, where total dissolved organics are present at much higher concentrations (∼ 10 M), the major products are oligomers formed via organic radical-radical reactions, and simulated SOA yields (by mass) are ∼ 90% for both glyoxal and methylglyoxal.

  11. Organic Aerosol Component (OACOMP) Value-Added Product Report

    SciTech Connect

    Fast, J; Zhang, Q; Tilp, A; Shippert, T; Parworth, C; Mei, F

    2013-08-23

    Significantly improved returns in their aerosol chemistry data can be achieved via the development of a value-added product (VAP) of deriving OA components, called Organic Aerosol Components (OACOMP). OACOMP is primarily based on multivariate analysis of the measured organic mass spectral matrix. The key outputs of OACOMP are the concentration time series and the mass spectra of OA factors that are associated with distinct sources, formation and evolution processes, and physicochemical properties.

  12. Production of Highly Charged Pharmaceutical Aerosols Using a New Aerosol Induction Charger

    PubMed Central

    Golshahi, Laleh; Longest, P. Worth; Holbrook, Landon; Snead, Jessica; Hindle, Michael

    2015-01-01

    Purpose Properly charged particles can be used for effective lung targeting of pharmaceutical aerosols. The objective of this study was to characterize the performance of a new induction charger that operates with a mesh nebulizer for the production of highly charged submicrometer aerosols to bypass the mouth-throat and deliver clinically relevant doses of medications to the lungs. Methods Variables of interest included combinations of model drug (i.e. albuterol sulfate) and charging excipient (NaCl) as well as strength of the charging field (1–5 kV/cm). Aerosol charge and size were measured using a modified electrical low pressure impactor system combined with high performance liquid chromatography. Results At the approximate mass median aerodynamic diameter (MMAD) of the aerosol (~ 0.4 μm), the induction charge on the particles was an order of magnitude above the field and diffusion charge limit. The nebulization rate was 439.3 ± 42.9 μl/min, which with a 0.1 % w/v solution delivered 419.5 ± 34.2 μg of medication per minute. A new correlation was developed to predict particle charge produced by the induction charger. Conclusions The combination of the aerosol induction charger and predictive correlations will allow for the practical generation and control of charged submicrometer aerosols for targeting deposition within the lungs. PMID:25823649

  13. Comparing secondary organic aerosol formation in two U.S. cities

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-12-01

    Secondary organic aerosols (SOAs) form from the oxidation of volatile organic compounds (VOCs) in the atmosphere, and the composition and abundance of SOAs determine their effects on air quality, human health, and the planetary radiation budget. To investigate how the production of SOAs varies with location, Zhang et al. conducted a parallel set of experiments in Los Angeles, Calif., and Atlanta, Ga. Both cities see a large amount of volatile organic compounds thrown into the air because of anthropogenic emissions, largely stemming from vehicles. Atlanta, unlike Los Angeles, also sees a large amount of biogenic emissions from vegetation in the region.

  14. Modeling the Role of Alkanes, Polycyclic Aromatic Hydrocarbons, and Their Oligomers in Secondary Organic Aerosol Formation

    EPA Science Inventory

    A computationally efficient method to treat secondary organic aerosol (SOA) from various length and structure alkanes as well as SOA from polycyclic aromatic hydrocarbons (PAHs) is implemented in the Community Multiscale Air Quality (CMAQ) model to predict aerosol concentrations ...

  15. Model analysis of secondary organic aerosol formation by glyoxal in laboratory studies: the case for photoenhanced chemistry.

    PubMed

    Sumner, Andrew J; Woo, Joseph L; McNeill, V Faye

    2014-10-21

    The reactive uptake of glyoxal by atmospheric aerosols is believed to be a significant source of secondary organic aerosol (SOA). Several recent laboratory studies have been performed with the goal of characterizing this process, but questions remain regarding the effects of photochemistry on SOA growth. We applied GAMMA (McNeill et al. Environ. Sci. Technol. 2012, 46, 8075-8081), a photochemical box model with coupled gas-phase and detailed aqueous aerosol-phase chemistry, to simulate aerosol chamber studies of SOA formation by the uptake of glyoxal by wet aerosol under dark and irradiated conditions (Kroll et al. J. Geophys. Res. 2005, 110 (D23), 1-10; Volkamer et al. Atmos. Chem. Phys. 2009, 9, 1907-1928; Galloway et al. Atmos. Chem. Phys. 2009, 9, 3331- 306 3345 and Geophys. Res. Lett. 2011, 38, L17811). We find close agreement between simulated SOA growth and the results of experiments conducted under dark conditions using values of the effective Henry's Law constant of 1.3-5.5 × 10(7) M atm(-1). While irradiated conditions led to the production of some organic acids, organosulfates, and other oxidation products via well-established photochemical mechanisms, these additional product species contribute negligible aerosol mass compared to the dark uptake of glyoxal. Simulated results for irradiated experiments therefore fell short of the reported SOA mass yield by up to 92%. This suggests a significant light-dependent SOA formation mechanism that is not currently accounted for by known bulk photochemistry, consistent with recent laboratory observations of SOA production via photosensitizer chemistry.

  16. MISR Aerosol Product Attributes and Statistical Comparisons with MODIS

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph A.; Nelson, David L.; Garay, Michael J.; Levy, Robert C.; Bull, Michael A.; Diner, David J.; Martonchik, John V.; Paradise, Susan R.; Hansen, Earl G.; Remer, Lorraine A.

    2009-01-01

    In this paper, Multi-angle Imaging SpectroRadiometer (MISR) aerosol product attributes are described, including geometry and algorithm performance flags. Actual retrieval coverage is mapped and explained in detail using representative global monthly data. Statistical comparisons are made with coincident aerosol optical depth (AOD) and Angstrom exponent (ANG) retrieval results from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The relationship between these results and the ones previously obtained for MISR and MODIS individually, based on comparisons with coincident ground-truth observations, is established. For the data examined, MISR and MODIS each obtain successful aerosol retrievals about 15% of the time, and coincident MISR-MODIS aerosol retrievals are obtained for about 6%-7% of the total overlap region. Cloud avoidance, glint and oblique-Sun exclusions, and other algorithm physical limitations account for these results. For both MISR and MODIS, successful retrievals are obtained for over 75% of locations where attempts are made. Where coincident AOD retrievals are obtained over ocean, the MISR-MODIS correlation coefficient is about 0.9; over land, the correlation coefficient is about 0.7. Differences are traced to specific known algorithm issues or conditions. Over-ocean ANG comparisons yield a correlation of 0.67, showing consistency in distinguishing aerosol air masses dominated by coarse-mode versus fine-mode particles. Sampling considerations imply that care must be taken when assessing monthly global aerosol direct radiative forcing and AOD trends with these products, but they can be used directly for many other applications, such as regional AOD gradient and aerosol air mass type mapping and aerosol transport model validation. Users are urged to take seriously the published product data-quality statements.

  17. Modeling the influence of alkane molecular structure on secondary organic aerosol formation.

    PubMed

    Aumont, Bernard; Camredon, Marie; Mouchel-Vallon, Camille; La, Stéphanie; Ouzebidour, Farida; Valorso, Richard; Lee-Taylor, Julia; Madronich, Sasha

    2013-01-01

    Secondary Organic Aerosols (SOA) production and ageing is a multigenerational oxidation process involving the formation of successive organic compounds with higher oxidation degree and lower vapor pressure. Intermediate Volatility Organic Compounds (IVOC) emitted to the atmosphere are expected to be a substantial source of SOA. These emitted IVOC constitute a complex mixture including linear, branched and cyclic alkanes. The explicit gas-phase oxidation mechanisms are here generated for various linear and branched C10-C22 alkanes using the GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) and SOA formation is investigated for various homologous series. Simulation results show that both the size and the branching of the carbon skeleton are dominant factors driving the SOA yield. However, branching appears to be of secondary importance for the particle oxidation state and composition. The effect of alkane molecular structure on SOA yields appears to be consistent with recent laboratory observations. The simulated SOA composition shows, however, an unexpected major contribution from multifunctional organic nitrates. Most SOA contributors simulated for the oxidation of the various homologous series are far too reduced to be categorized as highly oxygenated organic aerosols (OOA). On a carbon basis, the OOA yields never exceeded 10% regardless of carbon chain length, molecular structure or ageing time. This version of the model appears clearly unable to explain a large production of OOA from alkane precursors.

  18. Unspeciated organic emissions from combustion sources and their influence on the secondary organic aerosol budget in the United States.

    PubMed

    Jathar, Shantanu H; Gordon, Timothy D; Hennigan, Christopher J; Pye, Havala O T; Pouliot, George; Adams, Peter J; Donahue, Neil M; Robinson, Allen L

    2014-07-22

    Secondary organic aerosol (SOA) formed from the atmospheric oxidation of nonmethane organic gases (NMOG) is a major contributor to atmospheric aerosol mass. Emissions and smog chamber experiments were performed to investigate SOA formation from gasoline vehicles, diesel vehicles, and biomass burning. About 10-20% of NMOG emissions from these major combustion sources are not routinely speciated and therefore are currently misclassified in emission inventories and chemical transport models. The smog chamber data demonstrate that this misclassification biases model predictions of SOA production low because the unspeciated NMOG produce more SOA per unit mass than the speciated NMOG. We present new source-specific SOA yield parameterizations for these unspeciated emissions. These parameterizations and associated source profiles are designed for implementation in chemical transport models. Box model calculations using these new parameterizations predict that NMOG emissions from the top six combustion sources form 0.7 Tg y(-1) of first-generation SOA in the United States, almost 90% of which is from biomass burning and gasoline vehicles. About 85% of this SOA comes from unspeciated NMOG, demonstrating that chemical transport models need improved treatment of combustion emissions to accurately predict ambient SOA concentrations.

  19. A New Stratospheric Aerosol Product from CALIPSO Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Kar, J.; Vaughan, M.; Trepte, C. R.; Winker, D. M.; Vernier, J. P.; Pitts, M. C.; Young, S. A.; Liu, Z.; Lucker, P.; Tackett, J. L.; Omar, A. H.

    2014-12-01

    Stratospheric aerosols are derived from precursor SO2 and OCS gases transported from the lower troposphere. Volcanic injections can also enhance aerosol loadings far above background levels. The latter can exert a significant influence on the Earth's radiation budget for major and even minor eruptions. Careful measurements are needed, therefore, to monitor the distribution and evolution of stratospheric aerosols for climate related studies. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission has been acquiring profile measurements of clouds and aerosols since 2006, leading to major advances in our understanding of tropospheric aerosol and cloud properties and the processes that control them. The CALIPSO products have also enabled new insights into polar stratospheric clouds and stratospheric aerosols. Vernier et al (2009,JGR,114,D00H10) reported on the construction of a modified CALIPSO lidar product that corrected minor artifacts with the original lidar calibration that affected stratospheric aerosol investigations. A significantly improved CALIPSO Lidar Version 4 Level 1 product has been recently released addressing these calibration issues and has resulted in enhanced signal levels and a highly stable record over the span of the mission. Based on this product, a new 3D gridded stratospheric CALIPSO data product is under development and being targeted for release in 2015. A key emphasis of this new product is to bridge the measurement gap between the SAGE II and SAGE III data record (1984-2005) and the start of measurements from the new SAGE III instrument to be deployed on the International Space Station in 2016. The primary parameters delivered in the CALIPSO stratospheric data products will be attenuated scattering ratio and aerosol extinction profiles, both averaged over one month intervals and binned into an equal angle grid of constant latitude and longitude with a vertical resolution of 900m. We will present the overall

  20. Multi-generational oxidation model to simulate secondary organic aerosol in a 3-D air quality model

    NASA Astrophysics Data System (ADS)

    Jathar, S. H.; Cappa, C. D.; Wexler, A. S.; Seinfeld, J. H.; Kleeman, M. J.

    2015-08-01

    Multi-generational gas-phase oxidation of organic vapors can influence the abundance, composition and properties of secondary organic aerosol (SOA). Only recently have SOA models been developed that explicitly represent multi-generational SOA formation. In this work, we integrated the statistical oxidation model (SOM) into SAPRC-11 to simulate the multi-generational oxidation and gas/particle partitioning of SOA in the regional UCD/CIT (University of California, Davis/California Institute of Technology) air quality model. In the SOM, evolution of organic vapors by reaction with the hydroxyl radical is defined by (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 organic molecule. These SOM parameter values were fit to laboratory smog chamber data for each precursor/compound class. SOM was installed in the UCD/CIT model, which simulated air quality over 2-week periods in the South Coast Air Basin of California and the eastern United States. For the regions and episodes tested, the two-product SOA model and SOM produce similar SOA concentrations but a modestly different SOA chemical composition. Predictions of the oxygen-to-carbon ratio qualitatively agree with those measured globally using aerosol mass spectrometers. Overall, the implementation of the SOM in a 3-D model provides a comprehensive framework to simulate the atmospheric evolution of organic aerosol.

  1. Susceptibility of stored-product psocids to aerosol insecticides.

    PubMed

    Opit, George P; Arthur, Frank H; Throne, James E; Payton, Mark E

    2012-01-01

    The efficacies of commercial methoprene and esfenvalerate aerosols for control of stored-product psocid pests were evaluated in simulated field studies. The efficacies of methoprene, esfenvalerate EC, the carrier Isopar-M™, and a combination of methoprene and esfenvalerate aerosols for control of Liposcelis decolor (Pearman) (Psocoptera: Liposcelididae) and Liposcelis entomophila (Enderlein) nymphs were assessed, and the effects of direct and indirect exposure of Liposcelis bostrychophila Badonnel, L. decolor, and Liposcelis paeta Pearman adults to esfenvalerate EC aerosol were evaluated. The greatest nymphal mortality attained was 76%, indicating that the four aerosols tested were ineffective against L. decolor and L. entomophila nymphs. In the direct and indirect exposure studies, the greatest adult mortalities attained for the three psocid species were 62 and 32%, respectively. Based on these data, esfenvalerate aerosol is ineffective for control of L. bostrychophila, L. decolor, L. entomophila, and L. paeta psocid species. This study shows that methoprene, esfenvalerate EC, and a combination of methoprene and esfenvalerate aerosols were ineffective against the four psocid species tested when applied at rates that are usually effective against other stored-product insect pests.

  2. Susceptibility of Stored-Product Psocids to Aerosol Insecticides

    PubMed Central

    Opit, George P.; Arthur, Frank H.; Throne, James E.; Payton, Mark E.

    2012-01-01

    The efficacies of commercial methoprene and esfenvalerate aerosols for control of stored-product psocid pests were evaluated in simulated field studies. The efficacies of methoprene, esfenvalerate EC, the carrier Isopar-M™, and a combination of methoprene and esfenvalerate aerosols for control of Liposcelis decolor (Pearman) (Psocoptera: Liposcelididae) and Liposcelis entomophila (Enderlein) nymphs were assessed, and the effects of direct and indirect exposure of Liposcelis bostrychophila Badonnel, L. decolor, and Liposcelis paeta Pearman adults to esfenvalerate EC aerosol were evaluated. The greatest nymphal mortality attained was 76%, indicating that the four aerosols tested were ineffective against L. decolor and L. entomophila nymphs. In the direct and indirect exposure studies, the greatest adult mortalities attained for the three psocid species were 62 and 32%, respectively. Based on these data, esfenvalerate aerosol is ineffective for control of L. bostrychophila, L. decolor, L. entomophila, and L. paeta psocid species. This study shows that methoprene, esfenvalerate EC, and a combination of methoprene and esfenvalerate aerosols were ineffective against the four psocid species tested when applied at rates that are usually effective against other stored-product insect pests. PMID:23463916

  3. Effect of Vapor Pressure Scheme on Multiday Evolution of SOA in an Explicit Model

    NASA Astrophysics Data System (ADS)

    Lee-Taylor, J.; Madronich, S.; Aumont, B.; Camredon, M.; Emmons, L. K.; Tyndall, G. S.; Valorso, R.

    2011-12-01

    Recent modeling of the evolution of Secondary Organic Aerosol (SOA) has led to the critically important prediction that SOA mass continues to increase for several days after emission of primary pollutants. This growth of organic aerosol in dispersing plumes originating from urban point sources has direct implications for regional aerosol radiative forcing. We investigate the robustness of predicted SOA mass growth downwind of Mexico City in the model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), by assessing its sensitivity to the choice of vapor pressure prediction scheme. We also explore the implications for multi-day SOA mass growth of glassification / solidification of SOA constituents during aging. Finally we use output from the MOZART-4 chemical transport model to evaluate our results in the regional and global context.

  4. Organic aerosol formation from biogenic compounds over the Ponderosa pine forest in Colorado

    NASA Astrophysics Data System (ADS)

    Roux, Alma Hodzic; Lee-Taylor, Julia; Cui, Yuyan; Madronich, Sasha

    2013-05-01

    The secondary organic aerosol (SOA) formation and regional growth from biogenic precursors is of particular interest given their abundance in the atmosphere, and has been investigated during the Rocky Mountain Biogenic Aerosol field Study in 2011 in the pine forest canopy (dominated by terpene emissions) using both WRF/Chem 4km simulations and the GECKO-A explicit chemistry box-model runs. We have quantified the relative contribution of different biogenic precursors to SOA levels that were measured by the aerosol mass spectrometer at the site, and investigated the relative contribution of OH, O3 and NO3 chemistry to the formed SOA mass during day-and nighttime. Although, the local production and mass concentrations of submicron organic aerosols at the site seem relatively modest ˜1-2 ug/m3, we show that the optically active regional mass is increased as the SOA formation continues for several days in the background forest air. We investigate whether the simplified SOA parameterizations used in 3D models can capture this growth. In addition, preliminary comparisons of the number concentrations and the composition of ultrafine particles (8 - 30nm) from WRF/Chem simulations and TD-CIMS measurements are also discussed, and the contribution of organic aerosols to CCN formation is quantified.

  5. Light absorption coefficient measurement of SOA using a UV-Visible spectrometer connected with an integrating sphere

    NASA Astrophysics Data System (ADS)

    Zhong, Min; Jang, Myoseon

    2011-08-01

    A method for measuring an aerosol light absorption coefficient ( B a) has been developed using a conventional UV-visible spectrometer equipped with an integrating sphere covering a wide range of wavelengths (280-800 nm). The feasibility of the proposed method was evaluated in both the transmittance mode (TUV-IS) and the reflective mode (RUV-IS) using the reference aerosol known for the cross-sectional area. The aerosol was collected on a conventional filter and measured for B a values. The resulting RUV-IS method was applied to measure light absorption of secondary organic aerosol (SOA). SOA was produced through photooxidation of different precursor hydrocarbons such as toluene, d-limonene and α-pinene in the presence of NO x (60-70 ppb) and inorganic seed aerosol using a 2-m 3 indoor Teflon film chamber. Of the three precursor hydrocarbons, the B a value of toluene SOA (0.574 m 2 g -1 at 350 nm) was the highest compared with B a values for α-pinene SOA (0.029 m 2 g -1) and d-limonene SOA (0.038 m 2 g -1). When d-limonene SOA or toluene SOA was internally mixed with neutral [(NH 4) 2SO 4] or acidic inorganic seed (NH 4HSO 4:H 2SO 4 = 1:1 by mole), the SOA showed 2-3 times greater B a values at 350 nm than the SOA with no seed. Aerosol aging with a light source for this study reduced B a values of SOA (e.g., on average 10% for toluene SOA and 30% for d-limonene SOA within 4 h). Overall, weak absorption appeared for chamber-generated SOA over wavelengths ranging from 280 to 550 nm, which fall into the sunlight spectrum.

  6. Simulations of organic aerosol concentrations in Mexico City using the WRF-CHEM model during the MCMA-2006/MILAGRO campaign

    NASA Astrophysics Data System (ADS)

    Li, G.; Zavala, M.; Lei, W.; Tsimpidi, A. P.; Karydis, V. A.; Pandis, S. N.; Canagaratna, M. R.; Molina, L. T.

    2011-04-01

    Organic aerosol concentrations are simulated using the WRF-CHEM model in Mexico City during the period from 24 to 29 March in association with the MILAGRO-2006 campaign. Two approaches are employed to predict the variation and spatial distribution of the organic aerosol concentrations: (1) a traditional 2-product secondary organic aerosol (SOA) model with non-volatile primary organic aerosols (POA); (2) a non-traditional SOA model including the volatility basis-set modeling method in which primary organic components are assumed to be semi-volatile and photochemically reactive and are distributed in logarithmically spaced volatility bins. The MCMA (Mexico City Metropolitan Area) 2006 official emission inventory is used in simulations and the POA emissions are modified and distributed by volatility based on dilution experiments for the non-traditional SOA model. The model results are compared to the Aerosol Mass Spectrometry (AMS) observations analyzed using the Positive Matrix Factorization (PMF) technique at an urban background site (T0) and a suburban background site (T1) in Mexico City. The traditional SOA model frequently underestimates the observed POA concentrations during rush hours and overestimates the observations in the rest of the time in the city. The model also substantially underestimates the observed SOA concentrations, particularly during daytime, and only produces 21% and 25% of the observed SOA mass in the suburban and urban area, respectively. The non-traditional SOA model performs well in simulating the POA variation, but still overestimates during daytime in the urban area. The SOA simulations are significantly improved in the non-traditional SOA model compared to the traditional SOA model and the SOA production is increased by more than 100% in the city. However, the underestimation during daytime is still salient in the urban area and the non-traditional model also fails to reproduce the high level of SOA concentrations in the suburban area

  7. Differences in BVOC oxidation and SOA formation above and below the forest canopy

    NASA Astrophysics Data System (ADS)

    Schulze, Benjamin C.; Wallace, Henry W.; Flynn, James H.; Lefer, Barry L.; Erickson, Matt H.; Jobson, B. Tom; Dusanter, Sebastien; Griffith, Stephen M.; Hansen, Robert F.; Stevens, Philip S.; VanReken, Timothy; Griffin, Robert J.

    2017-02-01

    Gas-phase biogenic volatile organic compounds (BVOCs) are oxidized in the troposphere to produce secondary pollutants such as ozone (O3), organic nitrates (RONO2), and secondary organic aerosol (SOA). Two coupled zero-dimensional models have been used to investigate differences in oxidation and SOA production from isoprene and α-pinene, especially with respect to the nitrate radical (NO3), above and below a forest canopy in rural Michigan. In both modeled environments (above and below the canopy), NO3 mixing ratios are relatively small (< 0.5 pptv); however, daytime (08:00-20:00 LT) mixing ratios below the canopy are 2 to 3 times larger than those above. As a result of this difference, NO3 contributes 12 % of total daytime α-pinene oxidation below the canopy while only contributing 4 % above. Increasing background pollutant levels to simulate a more polluted suburban or peri-urban forest environment increases the average contribution of NO3 to daytime below-canopy α-pinene oxidation to 32 %. Gas-phase RONO2 produced through NO3 oxidation undergoes net transport upward from the below-canopy environment during the day, and this transport contributes up to 30 % of total NO3-derived RONO2 production above the canopy in the morning (˜ 07:00). Modeled SOA mass loadings above and below the canopy ultimately differ by less than 0.5 µg m-3, and extremely low-volatility organic compounds dominate SOA composition. Lower temperatures below the canopy cause increased partitioning of semi-volatile gas-phase products to the particle phase and up to 35 % larger SOA mass loadings of these products relative to above the canopy in the model. Including transport between above- and below-canopy environments increases above-canopy NO3-derived α-pinene RONO2 SOA mass by as much as 45 %, suggesting that below-canopy chemical processes substantially influence above-canopy SOA mass loadings, especially with regard to monoterpene-derived RONO2.

  8. Secondary Organic Aerosol Produced from Aqueous Reactions of Phenols in Fog Drops and Deliquesced Particles

    NASA Astrophysics Data System (ADS)

    Smith, J.; Anastasio, C.

    2014-12-01

    The formation and evolution of secondary organic aerosol (SOA) in atmospheric condensed phases (i.e., aqueous SOA) can proceed rapidly, but relatively little is known of the important aqueous SOA precursors or their reaction pathways. In our work we are studying the aqueous SOA formed from reactions of phenols (phenol, guaiacol, and syringol), benzene-diols (catechol, resorcinol, and hydroquinone), and phenolic carbonyls (e.g., vanillin and syringaldehyde). These species are potentially important aqueous SOA precursors because they are released in large quantities from biomass burning, have high Henry's Law constants (KH = 103 -109 M-1 atm-1) and are rapidly oxidized. To evaluate the importance of aqueous reactions of phenols as a source of SOA, we first quantified the kinetics and SOA mass yields for 11 phenols reacting via direct photodegradation, hydroxyl radical (•OH), and with an excited organic triplet state (3C*). In the second step, which is the focus of this work, we use these laboratory results in a simple model of fog chemistry using conditions during a previously reported heavy biomass burning event in Bakersfield, CA. Our calculations indicate that under aqueous aerosol conditions (i.e., a liquid water content of 100 μg m-3) the rate of aqueous SOA production (RSOA(aq)) from phenols is similar to the rate in the gas phase. In contrast, under fog/cloud conditions the aqueous RSOA from phenols is 10 times higher than the rate in the gas phase. In both of these cases aqueous RSOA is dominated by the oxidation of phenols by 3C*, followed by direct photodegradation of phenolic carbonyls, and then •OH oxidation. Our results suggest that aqueous oxidation of phenols is a significant source of SOA during fog events and also during times when deliquesced aerosols are present.

  9. Importance of Aqueous-phase Secondary Organic Aerosol Formation from Aromatics in an Atmospheric Hydrocarbon Mixture

    NASA Astrophysics Data System (ADS)

    Parikh, H. M.; Carlton, A. G.; Vizuete, W.; Zhang, H.; Zhou, Y.; Chen, E.; Kamens, R. M.

    2010-12-01

    Two new secondary organic aerosol (SOA) modeling frameworks are developed, one based on an aromatic gas and particle-phase kinetic mechanism and another based on a parameterized SOA model used in conjunction with an underlying gas-phase mechanism, both of which simulate SOA formation through partitioning to two stable liquid phases: one hydrophilic containing particle aqueous-phase and the other hydrophobic comprising mainly organic components. The models were evaluated against outdoor smog chamber experiments with different combinations of initial toluene, o-xylene, p-xylene, toluene and xylene mixtures, NOx, non-SOA-forming hydrocarbon mixture, initial seed type, and humidity. Aerosol data for experiments with either ammonium sulfate or initial background seed particles, in the presence of an atmospheric hydrocarbon mixture, NOx and in sunlight under a dry atmosphere (RH = 6 to 10%) show reduced SOA formation when compared to experiments with similar initial gas and particle concentrations at higher relative humidities (RH = 40 to 90%). Both frameworks simulated reasonable fits to the total observed SOA concentrations under all conditions. For both dry and wet experiments with low initial seed, semi-volatile product partitioning in particle organic-phase is mass-transfer limited and is modeled using a dynamic gas-particle partitioning algorithm with accommodation coefficient as the primary pseudo-transport parameter. Further, the modeled SOA product distributions for both frameworks clearly show the importance of the contribution of aqueous-phase SOA particularly under conditions of low initial seed concentrations and high-humidity. For both models, under these conditions, aqueous-phase SOA from uptake of glyoxal, methylglyoxal and related polar products to particle water phase dominates as compared to the partitioning of semi-volatiles to particle organic phase. Interestingly, both the kinetic and parameterized SOA frameworks simulate similar amounts of aqueous

  10. The water up-take of semisolid SOA particles

    NASA Astrophysics Data System (ADS)

    Pajunoja, A.; Lambe, A. T.; Hakala, J. P.; Rastak, N.; Hao, L.; Paramonov, M.; Hong, J.; Laaksonen, A. J.; Kulmala, M. T.; Massoli, P.; Onasch, T. B.; Donahue, N. M.; Riipinen, I.; Davidovits, P.; Worsnop, D. R.; Petäjä, T.; Virtanen, A.

    2014-12-01

    The dependence of aerosol particle hygroscopicity on particle composition is often represented with the single parameter k commonly used in global models to describe the hygroscopic properties of atmospheric aerosol particles. From the theoretical formulation of k the same value is expected for ideal solutes in both the sub- and supersaturated regimes as typically calculated from hygroscopicity tandem differential mobility analyser (HTDMA) and cloud condensation nuclei counter (CCNc) measurements respectively (i.e. k HGF and kCCN). Yet, a number of recent studies conducted on SOA indicate that the two measurements yield different k values (k HGF < kCCN). There are several studies discussing the behaviour but the underlying reasons are unresolved. To investigate this in more detailed, CCNc and HTDMA measurements were conducted to determine the effects of chemical composition, oxidation level, the phase state and RH on the associated water uptake properties of biogenic SOA particles formed from isoprene, a-pinene, and longifolene precursors. Pure SOA particles by OH and/or O3 oxidation of the gas-phase precursors were formed in a PAM (Potential Aerosol Mass) flow tube reactor. Hygroscopic growth factors (HGF) were measured by Hygroscopicity Tandem Differential Mobility Analyser (HTDMA) at RH range of 50-~95% and CCN activation by CCN counter. To investigate the physical phase of the particles the particle bounced fraction (BF) using an Aerosol Bounce Instrument (ABI) was also measured. SOA oxidation state and composition was measured by a c-ToF-AMS. Based on the measurements we suggest that at subsaturation conditions semi solid SOA particles take up water mostly via surface adsorption resulting a large discrepancy between the kHGF and kCCN values. By calculating the aerosol direct radiative effect (Wm-2) using our results we also show that ambiguity about the κ values has important implications for quantifying the climate effects of SOA in atmospheric models.

  11. Enhanced Light Scattering of Secondary Organic Aerosols by Multiphase Reactions.

    PubMed

    Li, Kun; Li, Junling; Liggio, John; Wang, Weigang; Ge, Maofa; Liu, Qifan; Guo, Yucong; Tong, Shengrui; Li, Jiangjun; Peng, Chao; Jing, Bo; Wang, Dong; Fu, Pingqing

    2017-02-07

    Secondary organic aerosol (SOA) plays a pivotal role in visibility and radiative forcing, both of which are intrinsically linked to the refractive index (RI). While previous studies have focused on the RI of SOA from traditional formation processes, the effect of multiphase reactions on the RI has not been considered. Here, we investigate the effects of multiphase processes on the RI and light-extinction of m-xylene-derived SOA, a common type of anthropogenic SOA. We find that multiphase reactions in the presence of liquid water lead to the formation of oligomers from intermediate products such as glyoxal and methylglyoxal, resulting in a large enhancement in the RI and light-scattering of this SOA. These reactions will result in increases in light-scattering efficiency and direct radiative forcing of approximately 20%-90%. These findings improve our understanding of SOA optical properties and have significant implications for evaluating the impacts of SOA on the rapid formation of regional haze, global radiative balance, and climate change.

  12. Organic Aerosol Component (OACOMP) Value-Added Product

    SciTech Connect

    Fast, J; Zhang, Q; tilp, A; Shippert, T; Parworth, C; Mei, F

    2013-08-23

    Organic aerosol (OA, i.e., the organic fraction of particles) accounts for 10–90% of the fine aerosol mass globally and is a key determinant of aerosol radiative forcing. But atmospheric OA is poorly characterized and its life cycle insufficiently represented in models. As a result, current models are unable to simulate OA concentrations and properties accurately. This deficiency represents a large source of uncertainty in quantification of aerosol effects and prediction of future climate change. Evaluation and development of aerosol models require data products generated from field observations. Real-time, quantitative data acquired with aerosol mass spectrometers (AMS) (Canagaratna et al. 2007) are critical to this need. The AMS determines size-resolved concentrations of non-refractory (NR) species in submicrometer particles (PM1) with fast time resolution suitable for both ground-based and aircraft deployments. The high-resolution AMS (HR-AMS), which is equipped with a high mass resolution time-of-flight mass spectrometer, can be used to determine the elemental composition and oxidation degrees of OA (DeCarlo et al. 2006).

  13. Secondary organic aerosol formation during the photooxidation of toluene: NOx dependence of chemical composition.

    PubMed

    Sato, Kei; Hatakeyama, Shiro; Imamura, Takashi

    2007-10-04

    The photooxidation of toluene is a potential source of secondary organic aerosol (SOA) in urban air, but only a small portion of the compounds present in SOA have been identified. In this study, we analyzed the chemical compositions of SOA produced by photoirradiation of the toluene/NOx/air system in laboratory chamber experiments by a combination of liquid chromatography-mass spectrometry, hybrid high-performance liquid chromatography-mass spectrometry, and iodometry-spectrophotometry. The dependence of the chemical composition on the initial NOx concentration was examined at initial NO concentrations ([NO]0) of 0.2 and 1 ppmv. Fifteen semivolatile products, including aromatic and ring-cleavage compounds, were quantified. However, the quantified products comprised only a small portion ( approximately 1 wt %) of the total aerosol mass. The total SOA yield ( approximately 13 wt %), the ratio of organic peroxides to total SOA mass ( approximately 17 wt %), and the density of SOA ( approximately 1.4 g cm-3) were independent of the NOx level, suggesting that the reaction mechanisms of the formation of major SOA products at [NO]0 = 0.2 and 1 ppmv are essentially the same. The negative-ion mass spectra of SOA samples showed that ion signals attributed to hemiacetal oligomers and/or decomposition products of peroxy hemiacetal oligomers were detected in the range of mass-to-charge ratios (m/z) between 200 and 500. The highest signals were detected at m/z = 155 and 177, and these were tentatively assigned to C7 unsaturated oxacyclic oxocarboxylic acids and C7 unsaturated oxacyclic dicarboxylic acids, respectively. We conclude that the major chemical components of the aerosol are hemiacetal and peroxy hemiacetal oligomers and low-molecular-weight dicarboxylic acids.

  14. [Numerical simulation study of SOA in Pearl River Delta region].

    PubMed

    Cheng, Yan-li; Li, Tian-tian; Bai, Yu-hua; Li, Jin-long; Liu, Zhao-rong; Wang, Xue-song

    2009-12-01

    Secondary organic aerosols (SOA) is an important component of the atmospheric particle pollution, thus, determining the status and sources of SOA pollution is the premise of deeply understanding the occurrence, development law and the influence factors of the atmospheric particle pollution. Based on the pollution sources and meteorological data of Pearl River Delta region, the study used the two-dimensional model coupled with SOA module to stimulate the status and source of SOA pollution in regional scale. The results show: the generation of SOA presents obvious characteristics of photochemical reaction, and the high concentration appears at about 14:00; SOA concentration is high in some areas of Guangshou and Dongguan with large pollution source-emission, and it is also high in some areas of Zhongshan, Zhuhai and Jiangmen which are at downwind position of Guangzhou and Dongguan. Contribution ratios of several main pollution sources to SOA are: biogenic sources 72.6%, mobile sources 30.7%, point sources 12%, solvent and oil paint sources 12%, surface sources less than 5% respectively.

  15. Synthesis and Analysis of Putative Terpene Oxidation Products and the Secondary Organic Aerosol Particles that Form from Them

    NASA Astrophysics Data System (ADS)

    Ebben, C. J.; Strick, B. F.; Upshur, M.; Shrestha, M.; Velarde, L.; Lu, Z.; Wang, H.; Xiao, D.; Batista, V. S.; Martin, S. T.; Thomson, R. J.; Geiger, F. M.

    2013-12-01

    The terpenes isoprene and α-pinene are abundant volatile organic compounds (VOCs) that are emitted by trees and oxidized in the atmosphere. However, the chemical processes involved in the formation of secondary organic aerosol (SOA) particles from VOCs are not well understood. In this work, we use a combined synthetic, analytical, and theoretical approach to gain a molecular level understanding of the chemistry involved in the formation of SOA particles from VOC precursors. To this end, we have synthesized putative products of isoprene and α-pinene oxidation and the oligomers that form from them. Specifically, we have focused on the epoxide and 2-methyltetraols that form from isoprene oxidation by hydroxyl radicals, as well as products of α-pinene ozonolysis. In our analysis, we utilize a spectroscopic technique called sum frequency generation (SFG). SFG is a coherent, surface-specific, vibrational spectroscopy that uses infrared and visible laser light fields, overlapped spatially and temporally at a surface, to probe vibrational transitions within molecules. Our use of this technique allows us to assess the chemical identity of aerosol-forming components at their surfaces, where interactions with the gas phase occur. The spectral responses from these compounds are compared to those of synthetic isoprene- and α-pinene-derived aerosol particles, as well as natural aerosol particles collected in tropical and boreal forests to begin to predict the constituents that may be present at the surfaces of these particles. In addition, isotope editing is utilized to gain a better understanding of α-pinene. The rigidity of this molecule makes it difficult to understand spectroscopically. The combination of synthesis with deuterium labeling, theory, and broadband and high-resolution SFG spectroscopy in the C-H and C-D stretching regions allow us to determine the orientation of this important molecule on a surface, which could have implications for its reactivity in the

  16. SOA: A Quality Attribute Perspective

    DTIC Science & Technology

    2011-06-23

    JMS) – CORBA … • Infrastructure services available to service providers and/or service consumers to perform common tasks or satisfy QoS requirements...Services is one technology for SOA implementation SOA and Quality Attributes SOA WS* Web Services CORBA REST Services and POX Key Class Realization

  17. Measurements of Oxidized Organic Compounds during SOAS 2013 using nitrate ion chemical ionization coupled with High Resolution Time-of-Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Massoli, P.; Stark, H.; Cnagaratna, M.; Junninen, H.; Hakala, J. P.; Mauldin, R.; Ehn, M.; Sipila, M.; Krechmer, J.; Kimmel, J.; Jimenez, J. L.; Jayne, J. T.; Worsnop, D. R.

    2013-12-01

    We present ambient measurements of gaseous organic compounds by means of a High Resolution Time-of-Flight Chemical Ionization Mass Spectrometry (HR-ToF-CIMS) using nitrate ion (NO3-) chemistry. This technique allows to selectively detect oxidized gas-phase species, e.g., oxidized organic molecules and sulfuric acid via clustering with NO3- and its high order clusters. The capability of making such measurements is important because both sulfuric acid and organic gas molecules have a recognized key role in new particle formation (NPF) processes and likely have an important role in particulate phase chemistry and formation of secondary organic aerosols (SOA). The HR-ToF-CIMS was deployed during the Southern Oxidant and Aerosol Study (SOAS) at the forest supersite in Centreville, AL, from June 1 to July 15, 2013. The main goal of the SOAS campaign was to investigate the composition and sources of SOA in the Southeast US, where emissions are mainly represented by biogenic volatile organic compounds (BVOC) emissions and in less extent by anthropogenic emissions (AVOC). During SOAS, the HR-ToF-CIMS detected a range of organic ions that based on previous literature could be identified as oxidation products of both isoprene and terpenes. The isoprene products were 5 to 10 times more abundant than the terpene products. The isoprene-related molecules showed a diurnal cycle with a day time peak, typically after 1500 local time, while the terpene products were higher at night (between 2000 and 0600 local time). These results are consistent with the diurnal trends of primary BVOC emissions from other co-located instruments. The ambient data are also compared to laboratory measurements where oxidized organic vapors are produced using a Potential Aerosol Mass (PAM) flow reactor by the OH oxidation of biogenic gas-phase precursors (isoprene, a-pinene) over multiple days of equivalent atmospheric exposure.

  18. VIIRS Aerosol Products During the SEAC4RS Field Experiment

    NASA Astrophysics Data System (ADS)

    Remer, L. A.; Munchak, L. A.; Huang, J.; Martins, J. V.; Espinosa, R.; Orozco, D.

    2014-12-01

    The Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field experiment that took place during August and September 2013 offered an in depth portrait of the aerosol system over much of the continental United States. Heavily instrumented aircraft, including the NASA DC-8 sampled a wide variety of aerosol types including transported Saharan dust, both fresh and aged smoke from western wildfires, urban pollution plumes and also biogenic aerosol produced by the "green volcano" in the vegetated Ozarks. Complementing these aircraft measurements was an enhanced array of AERONET stations sprinkled across the country and also concentrated in a mesoscale array near the home base of Houston Texas. This rich collection of suborbital aerosol information permits a more comprehensive evaluation of the VIIRS aerosol product that includes validation of the products across the mesoscale and choices of case studies in which we can delve deeper into the VIIRS retrieval to test algorithm assumptions. We will compare VIIRS retrievals during SEAC4RS with MODIS retrievals, with AERONET observations and retrievals, and with measurements and retrievals from the Polar Imaging Nephelometer (PI-Neph) that flew aboard the NASA DC-8.

  19. Dimers and organosulfates derived from biogenic oxidation products in aerosols during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) in California 2007 and 2009 (Invited)

    NASA Astrophysics Data System (ADS)

    Glasius, M.; Worton, D. R.; Kristensen, K.; Nguyen, Q.; Surratt, J.; Enggrob, K. L.; Bouvier-Brown, N. C.; Farmer, D.; Docherty, K. S.; Platt, S.; Bilde, M.; Nøjgaard, J. K.; Seinfeld, J.; Jimenez, J. L.; Goldstein, A.

    2010-12-01

    Oxidation products of biogenic volatile organic compounds, such as monoterpenes and isoprene, contribute to biogenic secondary organic aerosol (BSOA). The organosulfate derivatives of these compounds are formed through heterogeneous reactions involving sulphur compounds, with a considerable contribution from anthropogenic sources. Organosulfate derivatives of biogenic oxidation products thus belong to a new group of anthropogenic enhanced biogenic SOA (ABSOA). The Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) during summers of 2007 and 2009 provided an excellent platform at Blodgett Forest, California (a ponderosa pine plantation) for studying ABSOA. Typically, polluted air masses were transported upslope from the California Central Valley during day, while night conditions were influenced by downslope transport of air masses, low local atmospheric mixing and formation of a shallow boundary layer. We collected particle samples (PM2.5) as one nighttime and two daytime samples per day. After extraction of filters in polar organic solvents (i.e. acetonitrile or methanol), organic aerosol constituents were analyzed by HPLC coupled through an electrospray inlet to a quadrupole time-of-flight mass spectrometer (qTOF-MS). Organosulfates and nitrooxy organosulfates derived from oxidation products of α-pinene, β-pinene, limonene and isoprene were identified based on their molecular mass and MS fragmentation patterns. Measurements by High Resolution Time of Flight Aerosol Mass Spectrometry (HR-ToF-AMS) show high mass loadings of nitrate in the night and morning samples with highest levels of the nitrooxy organosulfates with MW 295 and MW 297. This may indicate that elevated levels of nitrate and nitrooxy organosulfates are formed in the same polluted air mass, probably through nitrate radical reactions. Terpenylic acid, diterpenylic acid acetate, and methylbutane tricarboxylic acid were found at concentrations comparable to pinic acid. A dimer of

  20. Unspeciated organic emissions from combustion sources and their influence on the secondary organic aerosol budget in the United States

    EPA Science Inventory

    Secondary organic aerosol (SOA) formed from the atmospheric oxidation of nonmethane organic gases (NMOG) is a major contributor to atmospheric aerosol mass. Emissions and smog chamber experiments were performed to investigate SOA formation from gasoline vehicles, diesel vehicles,...

  1. Snow and Ice Mask for the MODIS Aerosol Products

    NASA Technical Reports Server (NTRS)

    Li, Rong-Rong; Remer, Lorraine; Kaufman, Yoram J.; Mattoo, Shana; Gao, Bo-Cai; Vermote, Eric

    2005-01-01

    The atmospheric products have been derived operationally from multichannel imaging data collected with the Moderate Resolution Imaging SpectroRadiometers (MODIS) on board the NASA Terra and Aqua spacecrafts. Preliminary validations of the products were previously reported. Through analysis of more extensive time-series of MODIS aerosol products (Collection 4), we have found that the aerosol products over land areas are slightly contaminated by snow and ice during the springtime snow-melting season. We have developed an empirical technique using MODIS near-IR channels centered near 0.86 and 1.24 pm and a thermal emission channel near 11 pm to mask out these snow-contaminated pixels over land. Improved aerosol retrievals over land have been obtained. Sample results from application of the technique to MODIS data acquired over North America, northern Europe, and northeastern Asia are presented. The technique has been implemented into the MODIS Collection 5 operational algorithm for retrieving aerosols over land from MODIS data.

  2. Volatility of methylglyoxal cloud SOA formed through OH radical oxidation and droplet evaporation

    NASA Astrophysics Data System (ADS)

    Ortiz-Montalvo, Diana L.; Schwier, Allison N.; Lim, Yong B.; McNeill, V. Faye; Turpin, Barbara J.

    2016-04-01

    The volatility of secondary organic aerosol (SOA) formed through cloud processing (aqueous hydroxyl radical (radOH) oxidation and droplet evaporation) of methylglyoxal (MGly) was studied. Effective vapor pressure and effective enthalpy of vaporization (ΔHvap,eff) were determined using 1) droplets containing MGly and its oxidation products, 2) a Vibrating Orifice Aerosol Generator (VOAG) system, and 3) Temperature Programmed Desorption Aerosol-Chemical Ionization Mass Spectrometry (TPD Aerosol-CIMS). Simulated in-cloud MGly oxidation (for 10-30 min) produces an organic mixture of higher and lower volatility components with an overall effective vapor pressure of (4 ± 7) × 10-7 atm at pH 3. The effective vapor pressure decreases by a factor of 2 with addition of ammonium hydroxide (pH 7). The fraction of organic material remaining in the particle-phase after drying was smaller than for similar experiments with glycolaldehyde and glyoxal SOA. The ΔHvap,eff of pyruvic acid and oxalic acid + methylglyoxal in the mixture (from TPD Aerosol-CIMS) were smaller than the theoretical enthalpies of the pure compounds and smaller than that estimated for the entire precursor/product mix after droplet evaporation. After 10-30 min of aqueous oxidation (one cloud cycle) the majority of the MGly + radOH precursor/product mix (even neutralized) will volatilize during droplet evaporation; neutralization and at least 80 min of oxidation at 10-12 M radOH (or >12 h at 10-14 M) is needed before low volatility ammonium oxalate exceeds pyruvate.

  3. Aerosol optical depth over complex topography: comparison of AVHRR, MERIS and MODIS aerosol products

    NASA Astrophysics Data System (ADS)

    Riffler, Michael; Popp, Christoph; Hauser, Adrian; Wunderle, Stefan

    Aerosols are a key component in the Earth's atmosphere, influencing the radiation budget due to scattering and absorption of solar and terrestrial radiation and changing cloud physics by serving as cloud condensation nuclei. Furthermore, dispersed particles alter visibility and affect human health. Remote sensing techniques are a common means to monitor aerosol variability on large spatial scales. The accuracy of these retrievals is highest over surfaces with well known spectral properties and low reflectance (e.g. oceans). The retrieval over brighter and heterogeneous land surfaces is more demanding, since temporally unstable surface reflectance and a reduced aerosol signal may result in larger errors. Regions with highly complex topography, like the Alps, can exhibit even larger errors, basically due to directional effects caused by the topography, temporal snow coverage, and usually higher cloud amount. Ground validation of remote sensing aerosol products is generally performed using sun photometer measurements from the AErosol RObotic NETwork (AERONET). However, the lack of such sites in the central parts of the Alps renders validation difficult. To study the potential of aerosol remote sensing in regions with complex topography, namely in the Alps, we make use of an unusual situation on one of the major trans-alpine traffic routes in June 2006: A fatal rock fall caused the nearly one month closure of the Gotthard route in the Central Swiss Reuss Valley. Large parts of the traffic were redirected to the San Bernardino route (eastern Switzerland), which had a large impact on the local traffic amount, and thereby on air quality. Herein we compare the performance of three different sensors (AVHRR, MERIS, MODIS) in detecting this obvious change in the aerosol optical depth of the two alpine valleys in summer 2006. First results from AVHRR show a clear reduction (47%) of the aerosol optical depth along the Gotthard route compared to the five year monthly mean (2003

  4. The STAR Grants Contribution to the SOAS Campaign

    EPA Science Inventory

    The Southern Oxidant and Aerosol Study (SOAS) is a community-led field campaign that was part of the Southeast Atmosphere Study (SAS). As one of the largest field studies in decades to characterize air quality in the Southeastern United States, SAS is a collaborative project invo...

  5. SOA governance in healthcare organisations.

    PubMed

    Koumaditis, Konstantinos; Themistocleous, Marinos; Vassilakopoulos, Georgios

    2013-01-01

    Service Oriented Architecture (SOA) is increasingly adopted by many sectors, including healthcare. Due to the nature of healthcare systems there is a need to increase SOA adoption success rates as the non integrated nature of healthcare systems is responsible for medical errors that cause the loss of tens of thousands patients per year. Following our previous research [1] we propose that SOA governance is a critical success factor for SOA success in healthcare. Literature reports multiple SOA governance models that have limitations and they are confusing. In addition to this, there is a lack of healthcare specific SOA governance models. This highlights a literature void and thus the purpose of this paper is to proposed a healthcare specific SOA governance framework.

  6. Complex refractive indices in the near-ultraviolet spectral region of biogenic secondary organic aerosol aged with ammonia

    SciTech Connect

    Flores, J. M.; Washenfelder, Rebecca; Adler, Gabriela; Lee, H-J; Segev, Lior; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey; Brown, Steven; Rudich, Yinon

    2014-05-14

    Atmospheric absorption by brown carbon aerosol may play an important role in global radiative forcing. Brown carbon arises from both primary and secondary sources, but the mechanisms and reactions for the latter are highly uncertain. One proposed mechanism is the reaction of ammonia or amino acids with carbonyl products in secondary organic aerosol (SOA). We generated SOA in situ by reacting biogenic alkenes (α-pinene, limonene, and α-humulene) with excess ozone, humidifying the resulting aerosol, and reacting the humidified aerosol with gaseous ammonia. We determined the complex refractive indices (RI) in the 360 – 420 nm range for these aerosols using broadband cavity enhanced spectroscopy (BBCES). The average real part (n) of the measured spectral range of the NH3-aged α-pinene SOA increased from n = 1.50 (±0.01) for the unreacted SOA to n = 1.57 (± 0.01) after a 1.5h exposure to 1.9 ppm NH3; whereas,the imaginary component (k) remained below k < 0.001 (± 0.002). For the limonene and α-humulene SOA the real part did not change significantly, and we observed a small change in the imaginary component of the RI. The imaginary component increased from k = 0.0 to an average k= 0.029 (± 0.021) for α-humulene SOA, and from k < 0.001 (± 0.002) to an average k = 0.032 (±0.019) for limonene SOA after a 1.5 h exposure to 1.3 and 1.9 ppm of NH3, respectively. Collected filter samples of the aged and unreacted α-pinene SOA and limonene SOA were analyzed off-line with nanospray desorption electrospray ionization high resolution mass spectrometry (nano-DESI/HR-MS), and in-situ with a Time-of-Fligh Aerosol Mass Spectrometer, confirming that the SOA reacted and that various nitrogen-containing reaction products formed. If we assume that NH3 aging reactions scale linearly with time and concentration, then a 1.5 h reaction with 1 ppm NH3 in the laboratory is equivalent to 24 h reaction with 63 ppbv NH3, indicating that the observed aerosol absorption will be limited

  7. Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation

    NASA Astrophysics Data System (ADS)

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; George, Katheryn M.; Anastasio, Cort; Laskin, Julia; Dillner, Ann M.; Zhang, Qi

    2016-04-01

    Organic aerosol is formed and transformed in atmospheric aqueous phases (e.g., cloud and fog droplets and deliquesced airborne particles containing small amounts of water) through a multitude of chemical reactions. Understanding these reactions is important for a predictive understanding of atmospheric aging of aerosols and their impacts on climate, air quality, and human health. In this study, we investigate the chemical evolution of aqueous secondary organic aerosol (aqSOA) formed during reactions of phenolic compounds with two oxidants - the triplet excited state of an aromatic carbonyl (3C∗) and hydroxyl radical (OH). Changes in the molecular composition of aqSOA as a function of aging time are characterized using an offline nanospray desorption electrospray ionization mass spectrometer (nano-DESI MS) whereas the real-time evolution of SOA mass, elemental ratios, and average carbon oxidation state (OSC) are monitored using an online aerosol mass spectrometer (AMS). Our results indicate that oligomerization is an important aqueous reaction pathway for phenols, especially during the initial stage of photooxidation equivalent to ˜ 2 h irradiation under midday winter solstice sunlight in Northern California. At later reaction times functionalization (i.e., adding polar oxygenated functional groups to the molecule) and fragmentation (i.e., breaking of covalent bonds) become more important processes, forming a large variety of functionalized aromatic and open-ring products with higher OSC values. Fragmentation reactions eventually dominate the photochemical evolution of phenolic aqSOA, forming a large number of highly oxygenated ring-opening molecules with carbon numbers (nC) below 6. The average nC of phenolic aqSOA decreases while average OSC increases over the course of photochemical aging. In addition, the saturation vapor pressures (C∗) of dozens of the most abundant phenolic aqSOA molecules are estimated. A wide range of C∗ values is observed

  8. Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation

    NASA Astrophysics Data System (ADS)

    Yu, L.; Smith, J.; Laskin, A.; George, K. M.; Anastasio, C.; Laskin, J.; Dillner, A. M.; Zhang, Q.

    2015-10-01

    Organic aerosol is formed and transformed in atmospheric aqueous phases (e.g., cloud and fog droplets and deliquesced airborne particles containing small amounts of water) through a multitude of chemical reactions. Understanding these reactions is important for a predictive understanding of atmospheric aging of aerosols and their impacts on climate, air quality, and human health. In this study, we investigate the chemical evolution of aqueous secondary organic aerosol (aqSOA) formed during reactions of phenolic compounds with two oxidants - the triplet excited state of an aromatic carbonyl (3C*) and hydroxyl radical (•OH). Changes in the molecular composition of aqSOA as a function of aging time are characterized using an offline nanospray desorption electrospray ionization mass spectrometer (nano-DESI MS) whereas the real-time evolution of SOA mass, elemental ratios, and average carbon oxidation state (OSC) are monitored using an online aerosol mass spectrometer (AMS). Our results indicate that oligomerization is an important aqueous reaction pathway for phenols, especially during the initial stage of photooxidation equivalent to ∼ 2 h irradiation under midday, winter solstice sunlight in northern California. At later reaction times functionalization (i.e., adding polar oxygenated functional groups to the molecule) and fragmentation (i.e., breaking of covalent bonds) become more important processes, forming a large variety of functionalized aromatic and open-ring products with higher OSC values. Fragmentation reactions eventually dominate the photochemical evolution of phenolic aqSOA, forming a large number of highly oxygenated open-ring molecules with carbon numbers (nC) below 6. The average nC of phenolic aqSOA decreases while average OSC increases over the course of photochemical aging. In addition, the saturation vapor pressures C*) of dozens of the most abundant phenolic aqSOA molecules are estimated. A wide range of C* values is observed

  9. Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation

    DOE PAGES

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; ...

    2016-04-13

    Organic aerosol is formed and transformed in atmospheric aqueous phases (e.g., cloud and fog droplets and deliquesced airborne particles containing small amounts of water) through a multitude of chemical reactions. Understanding these reactions is important for a predictive understanding of atmospheric aging of aerosols and their impacts on climate, air quality, and human health. In this study, we investigate the chemical evolution of aqueous secondary organic aerosol (aqSOA) formed during reactions of phenolic compounds with two oxidants – the triplet excited state of an aromatic carbonyl (3C∗) and hydroxyl radical (•OH). Changes in the molecular composition of aqSOA as amore » function of aging time are characterized using an offline nanospray desorption electrospray ionization mass spectrometer (nano-DESI MS) whereas the real-time evolution of SOA mass, elemental ratios, and average carbon oxidation state (OSC) are monitored using an online aerosol mass spectrometer (AMS). Our results indicate that oligomerization is an important aqueous reaction pathway for phenols, especially during the initial stage of photooxidation equivalent to  ∼  2 h irradiation under midday winter solstice sunlight in Northern California. At later reaction times functionalization (i.e., adding polar oxygenated functional groups to the molecule) and fragmentation (i.e., breaking of covalent bonds) become more important processes, forming a large variety of functionalized aromatic and open-ring products with higher OSC values. Fragmentation reactions eventually dominate the photochemical evolution of phenolic aqSOA, forming a large number of highly oxygenated ring-opening molecules with carbon numbers (nC) below 6. The average nC of phenolic aqSOA decreases while average OSC increases over the course of photochemical aging. In addition, the saturation vapor pressures (C∗) of dozens of the most abundant phenolic aqSOA molecules are estimated. A wide range of C∗ values

  10. Optical properties and aging of light-absorbing secondary organic aerosol

    DOE PAGES

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; ...

    2016-10-14

    The light-absorbing organic aerosol (OA) commonly referred to as “brown carbon” (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorptionmore » of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

  11. Optical properties and aging of light-absorbing secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-01

    The light-absorbing organic aerosol (OA) commonly referred to as "brown carbon" (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  12. Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Chan, A. W. H.; Chan, M. N.; Surratt, J. D.; Chhabra, P. S.; Loza, C. L.; Crounse, J. D.; Yee, L. D.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

    2010-08-01

    Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated aldehyde) under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO2) formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios (3-8), the SOA yields from isoprene high-NOx photooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

  13. Role of aldehyde chemistry and NOx concentrations in secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Chan, A. W. H.; Chan, M. N.; Surratt, J. D.; Chhabra, P. S.; Loza, C. L.; Crounse, J. D.; Yee, L. D.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

    2010-04-01

    Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA) via methacrolein (a C4-unsaturated aldehyde) under urban high-NOx conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as the important intermediate to isoprene and methacrolein SOA in this NOx regime. Here we show that as a result of this chemistry, NO2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NOx effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under high-NO2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO2) formation is structurally unfavorable. At atmospherically relevant NO2/NO ratios, the SOA yields from isoprene high-NOxphotooxidation are 3 times greater than previously measured at lower NO2/NO ratios. At sufficiently high NO2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO2 can exceed that from RO2+HO2 reactions under the same inorganic seed conditions, making RO2+NO2 an important channel for SOA formation.

  14. Impacts of Oil and Gas Exploration Activities on SOA formation in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Bahreini, R.; Vu, K. K. T.; Dingle, J. H.; Apel, E. C.; Blake, N. J.; Campos, T. L.; Cantrell, C. A.; Flocke, F. M.; Fried, A.; Herndon, S. C.; Hills, A. J.; Hornbrook, R. S.; Huey, L. G.; Kaser, L.; Mauldin, L.; Meinardi, S.; Montzka, D.; Nowak, J. B.; Richter, D.; Roscioli, J. R.; Schroeder, J.; Shertz, S.; Stell, M. H.; Tanner, D.; Tyndall, G. S.; Walega, J.; Weibring, P.; Weinheimer, A. J.

    2015-12-01

    Oil and gas exploration activities (O&G) in Wattenberg Field, located north of the Denver Metropolitan area, have expanded in the last few years. Although VOC emissions and the potential for ozone formation in the area from these sources have been studied previously, no information is available on the impact on secondary organic aerosol (SOA) formation. During the Front Range Air Pollution and Photochemistry Experiment (FRAPPE), airborne measurements of trace gases and aerosol composition were made in the northern Front Range during July-August 2014. We present analyses on evolution of organic aerosol (OA) and their precursors in order to assess the impact of urban vs. O&G emissions on SOA formation. Significant contribution of SOA to total OA was observed in pure urban and urban plumes mixed with O&G emissions. Under an OH-exposure of 2.8×1011 molecule cm-3 s, enhancement ratios of OA relative to carbon monoxide (ΔOA/ΔCO) increased by factors of ~3.6-5.4; however, (ΔSOA/ΔCO)urban+O&G was 87% higher than (ΔSOA/ΔCO)urban. Predicted ΔSOA/ΔCO values from the oxidation of C7-C11 alkanes, C6-C9 aromatics, and biogenics were about a factor of 10-15 too small compared to the measurements. Predicated alkane-derived SOA contributed to 38% (16%) of anthropogenic ΔSOA/ΔCO values in urban+O&G- (urban-) influenced air masses.

  15. Aerosol from Organic Nitrogen in the Southeast United States

    EPA Science Inventory

    Biogenic volatile organic compounds (BVOCs) contribute significantly to organic aerosol in the southeastern United States. During the Southern Oxidant and Aerosol Study (SOAS), a portion of ambient organic aerosol was attributed to isoprene oxidation and organic nitrogen from BVO...

  16. Aerosols

    Atmospheric Science Data Center

    2013-04-17

    ... article title:  Aerosols over Central and Eastern Europe     View Larger Image ... last weeks of March 2003, widespread aerosol pollution over Europe was detected by several satellite-borne instruments. The Multi-angle ...

  17. SOA formation from the photooxidation of α-pinene: systematic exploration of the simulation of chamber data

    NASA Astrophysics Data System (ADS)

    McVay, R. C.; Zhang, X.; Aumont, B.; Valorso, R.; Camredon, M.; La, Y. S.; Wennberg, P. O.; Seinfeld, J. H.

    2015-11-01

    Chemical mechanisms play an important role in simulating the atmospheric chemistry of volatile organic compound oxidation. Comparison of mechanism simulations with laboratory chamber data tests our level of understanding of the prevailing chemistry as well as the dynamic processes occurring in the chamber itself. α-pinene photooxidation is a well-studied system experimentally, for which detailed chemical mechanisms have been formulated. Here, we present the results of simulating low-NO α-pinene photooxidation experiments conducted in the Caltech chamber with the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) under varying concentrations of seed particles and OH levels. Unexpectedly, experiments conducted at low and high OH levels yield the same SOA growth, whereas GECKO-A predicts greater SOA growth under high OH levels. SOA formation in the chamber is a result of a competition among the rates of gas-phase oxidation to low volatility products, wall deposition of these products, and condensation into the aerosol phase. Various processes, such as photolysis of condensed-phase products, particle-phase dimerization, and peroxy radical autoxidation, are explored to rationalize the observations. In order to explain the observed similar SOA growth under different OH levels, we conclude that vapor wall loss in the Caltech chamber is likely of order 10-5 s-1, consistent with previous experimental measurements in that chamber. We find that GECKO-A tends to overpredict the contribution to SOA of later-generation oxidation products under high OH conditions. The key role of the interplay among oxidation rate, product volatility, and vapor-wall deposition in chamber experiments is illustrated.

  18. Implications of Low Volatility SOA and Gas-Phase Fragmentation Reactions on SOA Loadings and their Spatial and Temporal Evolution in the Atmosphere

    SciTech Connect

    Shrivastava, ManishKumar B.; Zelenyuk, Alla; Imre, Dan; Easter, Richard C.; Beranek, Josef; Zaveri, Rahul A.; Fast, Jerome D.

    2013-04-27

    Recent laboratory and field measurements by a number of groups show that secondary organic aerosol (SOA) evaporates orders of magnitude slower than traditional models assume. In addition, chemical transport models using volatility basis set (VBS) SOA schemes neglect gas-phase fragmentation reactions, which are known to be extremely important. In this work, we present modeling studies to investigate the implications of non-evaporating SOA and gas-phase fragmentation reactions. Using the 3-D chemical transport model, WRF-Chem, we show that previous parameterizations, which neglect fragmentation during multi-generational gas-phase chemistry of semi-volatile/inter-mediate volatility organics ("aging SIVOC"), significantly over-predict SOA as compared to aircraft measurements downwind of Mexico City. In sharp contrast, the revised models, which include gas-phase fragmentation, show much better agreement with measurements downwind of Mexico City. We also demonstrate complex differences in spatial SOA distributions when we transform SOA to non-volatile secondary organic aerosol (NVSOA) to account for experimental observations. Using a simple box model, we show that for same amount of SOA precursors, earlier models that do not employ multi-generation gas-phase chemistry of precursors ("non-aging SIVOC"), produce orders of magnitude lower SOA than "aging SIVOC" parameterizations both with and without fragmentation. In addition, traditional absorptive partitioning models predict almost complete SOA evaporation at farther downwind locations for both "non-aging SIVOC" and "aging SIVOC" with fragmentation. In contrast, in our revised approach, SOA transformed to NVSOA implies significantly higher background concentrations as it remains in particle phase even under highly dilute conditions. This work has significant implications on understanding the role of multi-generational chemistry and NVSOA formation on SOA evolution in the atmosphere.

  19. Enhanced secondary organic aerosols during fog episodes over typical location in Indo-Gangetic region

    NASA Astrophysics Data System (ADS)

    Kaul, D. S.; Tripathi, S. N.; Gupta, T.

    2011-12-01

    This study examines the reason of enhanced SOA yield during foggy days and hypothesizes likely production of SOA through aqueous phase chemistry during fog episodes. PM1 samples were collected from January 16, 2010 to February 20, 2010 at Kanpur to study the secondary organic aerosol (SOA) production during clear and foggy days. Of the 180 samples collected, 56 were from foggy days. Micro-Pulse Lidar Network (MPLNET), a part of National Aeronautic Space Administration (NASA), was used for identification of fog duration. Organic Carbon (OC), Elemental Carbon (EC) and water soluble organic carbon analysis were carried out by a EC-OC analyzer and a TOC analyzer, respectively. Trace gases and solar flux measurement were carried out by gas analyzers and a pyranometer (a part of NASA), respectively to identify the photo-chemical activity. Meteorological data were measured by atmospheric weather station. SOA was estimated during foggy and clear days using tracer method. Enhanced SOA was observed during foggy days, production of SOA was highest in the afternoon and lower during morning and evening. Peak of OC/EC ratio during foggy days occurred earlier indicating role of aqueous phase chemistry in addition to gas-particle portioning which is the prevalent mechanism of SOA production during clear days. The possible contribution of biomass burning to SOA which could otherwise confound the SOA estimate during foggy days was also examined by biomass tracer, potassium ion. The influence of biomass to SOA during foggy days was found to be negligible. This is so because organic carbon from biomass origin is highly hygroscopic and is scavenged by the fog droplets. The lesser average concentration of water soluble organic carbon during foggy days support the scavenging and removal of the biomass originated organic carbon. Evaporation of individual fog and subsequent increase of OC/EC ratio further supported the aqueous phase production of SOA. The temperature and relative humidity

  20. Secondary organic aerosol formation from photochemical aging of light-duty gasoline vehicle exhausts in a smog chamber

    NASA Astrophysics Data System (ADS)

    Liu, T.; Wang, X.; Deng, W.; Hu, Q.; Ding, X.; Zhang, Y.; He, Q.; Zhang, Z.; Lü, S.; Bi, X.; Chen, J.; Yu, J.

    2015-08-01

    In China, a rapid increase in passenger vehicles has led to the growing concern of vehicle exhaust as an important source of anthropogenic secondary organic aerosol (SOA) in megacities hard hit by haze. In this study, the SOA formation of emissions from two idling light-duty gasoline vehicles (LDGVs) (Euro 1 and Euro 4) operated in China was investigated in a 30 m3 smog chamber. Five photo-oxidation experiments were carried out at 25 °C with relative humidity at around 50 %. After aging at an OH exposure of 5 × 106 molecules cm-3 h, the formed SOA was 12-259 times as high as primary organic aerosol (POA). The SOA production factors (PF) were 0.001-0.044 g kg-1 fuel, comparable with those from the previous studies at comparable OH exposure. This quite lower OH exposure than that in typical atmospheric conditions might however lead to the underestimation of the SOA formation potential from LDGVs. Effective SOA yields in this study were well fit by a one-product gas-particle partitioning model but quite lower than those of a previous study investigating SOA formation from three idling passenger vehicles (Euro 2-4). Traditional single-ring aromatic precursors and naphthalene could explain 51-90 % of the formed SOA. Unspeciated species such as branched and cyclic alkanes might be the possible precursors for the unexplained SOA. A high-resolution time-of-flight aerosol mass spectrometer was used to characterize the chemical composition of SOA. The relationship between f43 (ratio of m/z 43, mostly C2H3O+, to the total signal in mass spectrum) and f44 (mostly CO2+) of the gasoline vehicle exhaust SOA is similar to the ambient semi-volatile oxygenated organic aerosol (SV-OOA). We plot the O : C and H : C molar ratios of SOA in a Van Krevelen diagram. The slopes of ΔH : C / ΔO : C ranged from -0.59 to -0.36, suggesting that the oxidation chemistry in these experiments was a combination of carboxylic acid and alcohol/peroxide formation.

  1. Secondary organic aerosol formation from photochemical aging of light-duty gasoline vehicle exhausts in a smog chamber

    NASA Astrophysics Data System (ADS)

    Liu, T.; Wang, X.; Deng, W.; Hu, Q.; Ding, X.; Zhang, Y.; He, Q.; Zhang, Z.; Lü, S.; Bi, X.; Chen, J.; Yu, J.

    2015-04-01

    In China, fast increase in passenger vehicles has procured the growing concern about vehicle exhausts as an important source of anthropogenic secondary organic aerosols (SOA) in megacities hard-hit by haze. However, there are still no chamber simulation studies in China on SOA formation from vehicle exhausts. In this study, the SOA formation of emissions from two idling light-duty gasoline vehicles (LDGVs) (Euro 1 and Euro 4) in China was investigated in a 30 m3 smog chamber. Five photo-oxidation experiments were carried out at 25 °C with the relative humidity around 50%. After aging at an OH exposure of 5 × 106 molecules cm-3 h, the formed SOA was 12-259 times as high as primary OA (POA). The SOA production factors (PF) were 0.001-0.044 g kg-1 fuel, comparable with those from the previous studies at the quite similar OH exposure. This quite lower OH exposure than that in typical atmospheric condition might however lead to the underestimation of the SOA formation potential from LDGVs. Effective SOA yield data in this study were well fit by a one-product gas-particle partitioning model and quite lower than those of a previous study investigating SOA formation form three idling passenger vehicles (Euro 2-Euro 4). Traditional single-ring aromatic precursors and naphthalene could explain 51-90% of the formed SOA. Unspeciated species such as branched and cyclic alkanes might be the possible precursors for the unexplained SOA. A high-resolution time-of-flight aerosol mass spectrometer was used to characterize the chemical composition of SOA. The relationship between f43 (ratio of m/z 43, mostly C2H3O+, to the total signal in mass spectrum) and f44 (mostly CO2+) of the gasoline vehicle exhaust SOA is similar to the ambient semi-volatile oxygenated organic aerosol (SV-OOA). We plot the O : C and H : C molar ratios of SOA in a Van Krevelen diagram. The slopes of ΔH : C/ΔO : C ranged from -0.59 to -0.36, suggesting that the oxidation chemistry in these experiments was a

  2. Multi-generational oxidation model to simulate secondary organic aerosol in a 3-D air quality model

    NASA Astrophysics Data System (ADS)

    Jathar, S. H.; Cappa, C. D.; Wexler, A. S.; Seinfeld, J. H.; Kleeman, M. J.

    2015-02-01

    Multi-generational gas-phase oxidation of organic vapors can influence the abundance, composition and properties of secondary organic aerosol (SOA). Only recently have SOA models been developed that explicitly represent multi-generational SOA formation. In this work, we integrated the statistical oxidation model (SOM) into SAPRC-11 to simulate the multi-generational oxidation and gas/particle partitioning of SOA in the regional UCD/CIT air quality model. In SOM, evolution of organic vapors by reaction with the hydroxyl radical is defined by (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 organic molecule. These SOM parameter values were fit to laboratory "smog chamber" data for each precursor/compound class. The UCD/CIT model was used to simulate air quality over two-week periods in the South Coast Air Basin of California and the eastern United States. For the regions and episodes tested, the traditional two-product SOA model and SOM produce similar SOA concentrations but a modestly different SOA chemical composition. Predictions of the oxygen-to-carbon ratio qualitatively agree with those measured globally using aerosol mass spectrometers. Overall, the implementation of the SOM in a 3-D model provides a comprehensive framework to simulate the atmospheric evolution of OA.

  3. A Study of Cloud Processing of Organic Aerosols Using Models and CHAPS Data

    SciTech Connect

    Ervens, Barbara

    2012-01-17

    The main theme of our work has been the identification of parameters that mostly affect the formation and modification of aerosol particles and their interaction with water vapor. Our detailed process model studies led to simplifications/parameterizations of these effects that bridge detailed aerosol information from laboratory and field studies and the need for computationally efficient expressions in complex atmospheric models. One focus of our studies has been organic aerosol mass that is formed in the atmosphere by physical and/or chemical processes (secondary organic aerosol, SOA) and represents a large fraction of atmospheric particulate matter. Most current models only describe SOA formation by condensation of low volatility (or semivolatile) gas phase products and neglect processes in the aqueous phase of particles or cloud droplets that differently affect aerosol size and vertical distribution and chemical composition (hygroscopicity). We developed and applied models of aqueous phase SOA formation in cloud droplets and aerosol particles (aqSOA). Placing our model results into the context of laboratory, model and field studies suggests a potentially significant contribution of aqSOA to the global organic mass loading. The second focus of our work has been the analysis of ambient data of particles that might act as cloud condensation nuclei (CCN) at different locations and emission scenarios. Our model studies showed that the description of particle chemical composition and mixing state can often be greatly simplified, in particular in aged aerosol. While over the past years many CCN studies have been successful performed by using such simplified composition/mixing state assumptions, much more uncertainty exists in aerosol-cloud interactions in cold clouds (ice or mixed-phase). Therefore we extended our parcel model that describes warm cloud formation by ice microphysics and explored microphysical parameters that determine the phase state and lifetime of

  4. Secondary organic aerosol formation from fossil fuel sources contribute majority of summertime organic mass at Bakersfield

    NASA Astrophysics Data System (ADS)

    Liu, Shang; Ahlm, Lars; Day, Douglas A.; Russell, Lynn M.; Zhao, Yunliang; Gentner, Drew R.; Weber, Robin J.; Goldstein, Allen H.; Jaoui, Mohammed; Offenberg, John H.; Kleindienst, Tadeusz E.; Rubitschun, Caitlin; Surratt, Jason D.; Sheesley, Rebecca J.; Scheller, Scott

    2012-12-01

    Secondary organic aerosols (SOA), known to form in the atmosphere from oxidation of volatile organic compounds (VOCs) emitted by anthropogenic and biogenic sources, are a poorly understood but substantial component of atmospheric particles. In this study, we examined the chemical and physical properties of SOA at Bakersfield, California, a site influenced by anthropogenic and terrestrial biogenic emissions. Factor analysis was applied to the infrared and mass spectra of fine particles to identify sources and atmospheric processing that contributed to the organic mass (OM). We found that OM accounted for 56% of submicron particle mass, with SOA components contributing 80% to 90% of OM from 15 May to 29 June 2010. SOA formed from alkane and aromatic compounds, the two major classes of vehicle-emitted hydrocarbons, accounted for 65% OM (72% SOA). The alkane and aromatic SOA components were associated with 200 nm to 500 nm accumulation mode particles, likely from condensation of daytime photochemical products of VOCs. In contrast, biogenic SOA likely formed from condensation of secondary organic vapors, produced from NO3radical oxidation reactions during nighttime hours, on 400 nm to 700 nm sized primary particles, and accounted for less than 10% OM. Local petroleum operation emissions contributed 13% to the OM, and the moderate O/C (0.2) of this factor suggested it was largely of secondary origin. Approximately 10% of organic aerosols in submicron particles were identified as either vegetative detritus (10%) or cooking activities (7%), from Fourier transform infrared spectroscopic and aerosol mass spectrometry measurements, respectively. While the mass spectra of several linearly independent SOA components were nearly identical and external source markers were needed to separate them, each component had distinct infrared spectrum, likely associated with the source-specific VOCs from which they formed.

  5. Formation of Low Volatility Organic Compounds and Secondary Organic Aerosol from Isoprene Hydroxyhydroperoxide Low-NO Oxidation.

    PubMed

    Krechmer, Jordan E; Coggon, Matthew M; Massoli, Paola; Nguyen, Tran B; Crounse, John D; Hu, Weiwei; Day, Douglas A; Tyndall, Geoffrey S; Henze, Daven K; Rivera-Rios, Jean C; Nowak, John B; Kimmel, Joel R; Mauldin, Roy L; Stark, Harald; Jayne, John T; Sipilä, Mikko; Junninen, Heikki; Clair, Jason M St; Zhang, Xuan; Feiner, Philip A; Zhang, Li; Miller, David O; Brune, William H; Keutsch, Frank N; Wennberg, Paul O; Seinfeld, John H; Worsnop, Douglas R; Jimenez, Jose L; Canagaratna, Manjula R

    2015-09-01

    Gas-phase low volatility organic compounds (LVOC), produced from oxidation of isoprene 4-hydroxy-3-hydroperoxide (4,3-ISOPOOH) under low-NO conditions, were observed during the FIXCIT chamber study. Decreases in LVOC directly correspond to appearance and growth in secondary organic aerosol (SOA) of consistent elemental composition, indicating that LVOC condense (at OA below 1 μg m(-3)). This represents the first simultaneous measurement of condensing low volatility species from isoprene oxidation in both the gas and particle phases. The SOA formation in this study is separate from previously described isoprene epoxydiol (IEPOX) uptake. Assigning all condensing LVOC signals to 4,3-ISOPOOH oxidation in the chamber study implies a wall-loss corrected non-IEPOX SOA mass yield of ∼4%. By contrast to monoterpene oxidation, in which extremely low volatility VOC (ELVOC) constitute the organic aerosol, in the isoprene system LVOC with saturation concentrations from 10(-2) to 10 μg m(-3) are the main constituents. These LVOC may be important for the growth of nanoparticles in environments with low OA concentrations. LVOC observed in the chamber were also observed in the atmosphere during SOAS-2013 in the Southeastern United States, with the expected diurnal cycle. This previously uncharacterized aerosol formation pathway could account for ∼5.0 Tg yr(-1) of SOA production, or 3.3% of global SOA.

  6. Secondary Organic Aerosol Formation from Ambient Air in an Oxidation Flow Reactor at GoAmazon2014/5

    NASA Astrophysics Data System (ADS)

    Palm, Brett B.; de Sa, Suzane S.; Campuzano-Jost, Pedro; Day, Douglas A.; Hu, Weiwei; Seco, Roger; Park, Jeong-Hoo; Guenther, Alex; Kim, Saewung; Brito, Joel; Wurm, Florian; Artaxo, Paulo; Yee, Lindsay; Isaacman-VanWertz, Gabrial; Goldstein, Allen; Newburn, Matt K.; Lizabeth Alexander, M.; Martin, Scot T.; Brune, William H.; Jimenez, Jose L.

    2016-04-01

    During GoAmazon2014/5, ambient air was exposed to controlled concentrations of OH or O3 in situ using an oxidation flow reactor (OFR). Oxidation ranged from hours-several weeks of aging. Oxidized air was sampled by several instruments (e.g., HR-AMS, ACSM, PTR-TOF-MS, SMPS, CCN) at both the T3 site (IOP1: Feb 1-Mar 31, 2014, and IOP2: Aug 15-Oct 15, 2014) and T2 site (between IOPs and into 2nd IOP). The oxidation of ambient air in the OFR led to substantial and variable secondary organic aerosol (SOA) formation from any SOA-precursor gases, known and unknown, that entered the OFR. In general, more SOA was produced during the nighttime than daytime, suggesting that SOA-precursor gases were found in relatively higher concentrations at night. Similarly, more SOA was formed in the dry season (IOP2) than wet season (IOP1). The maximum amount of SOA produced during nighttime from OH oxidation ranged from less than 1 μg/m3 on some nights to greater than 10 μg/m3 on other nights. O3 oxidation of ambient air also led to SOA formation, although several times less than from OH oxidation. The amount of SOA formation sometimes, but not always, correlated with measured gas-phase biogenic and/or anthropogenic SOA precursors (e.g., SV-TAG sesquiterpenes, PTR-TOFMS aromatics, isoprene, and monoterpenes). The SOA mass formed in the OFR from OH oxidation was up to an order of magnitude larger than could be explained from aerosol yields of measured primary VOCs. This along with measurements from previous campaigns suggests that most SOA was formed from intermediate S/IVOC sources (e.g., VOC oxidation products, evaporated POA, or direct emissions). To verify the SOA yields of VOCs under OFR experimental conditions, atmospherically-relevant concentrations of several VOCs were added individually into ambient air in the OFR and oxidized by OH or O3. SOA yields in the OFR were similar to published chamber yields. Preliminary PMF factor analysis showed production of secondary factors in

  7. Source contributions to organic aerosol in the eastern United States

    NASA Astrophysics Data System (ADS)

    Lane, Timothy Edward

    Organic aerosols (OA) and elemental carbon (EC) are important components of atmospheric particulate matter (PM), potentially posing health hazards and contributing to global climate change. Secondary organic aerosol (SOA) is formed when condensable products from the oxidation of volatile organic compounds (VOCs) in the gas phase partition into the aerosol phase. Implementation of effective control strategies for organic PM2.5 (organic particles with diameters less than 2.5 mum) requires the quantification of the contribution of each source to the ambient OA and EC concentrations. The overall goal of this work is to determine which sources contribute the most to the organic aerosol concentrations across the eastern US. First, a source-resolved model is developed to predict the contribution of eight different sources to primary organic aerosol concentrations. Primary organic aerosol (OA) and elemental carbon (EC) concentrations are tracked for eight different sources: gasoline vehicles, non-road diesel vehicles, on-road diesel vehicles, biomass burning, wood burning, natural gas combustion, road dust, and all other sources. The results of the source-resolved model are compared to the results of chemical mass balance (CMB) models for Pittsburgh and multiple urban/rural sites from the Southeastern Aerosol Research and Characterization (SEARCH) network. Significant discrepancies exist between the source-resolved model and the CMB model predictions for several of the sources. There is strong evidence that the organic PM emissions from natural gas combustion are overestimated. Other similarities and discrepancies between the source-resolved model and the CMB model for primary OA and EC are discussed along with problems in the current emission inventory for certain sources. Next, the importance of isoprene as a source of SOA is determined using PMCAMx to predict the isoprene SOA concentration across the eastern US. Isoprene, the most abundant non-methane hydrocarbon

  8. The Collection 6 MODIS aerosol products over land and ocean

    NASA Astrophysics Data System (ADS)

    Levy, R. C.; Mattoo, S.; Munchak, L. A.; Remer, L. A.; Sayer, A. M.; Hsu, N. C.

    2013-01-01

    The twin Moderate Imaging resolution Spectroradiometer (MODIS) sensors have been flying on Terra since 2000 and Aqua since 2002, creating an incredible dataset of global Earth observations. Here, we introduce the Collection 6 (C6) algorithm to retrieve aerosol optical depth (AOD) and aerosol size parameters from MODIS-observed spectral reflectance. While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there is significant impact on the products and their interpretation. The C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties (1) over ocean (dark in visible and near-IR wavelengths), (2) over vegetated/dark-soiled land (dark in the visible) and (3) over desert/arid land (bright in the visible). Here, we focus on the changes to both "dark target" algorithms (#1 and #2; DT-ocean and DT-land). Affecting both DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, and relaxed the solar zenith angle limit (up to ≤ 84°) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season/location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. All together, the changes to the DT algorithms result in reduced global AOD (by 0.02) over ocean and increased AOD (by 0.01) over land, along with some changes in spatial coverage. Preliminary validation shows that compared to surface-based sunphotometer data, the C6 DT-products should compare at least as well as those from C5. However, at the same time as we

  9. The Collection 6 'dark-target' MODIS Aerosol Products

    NASA Technical Reports Server (NTRS)

    Levy, Robert C.; Mattoo, Shana; Munchak, Leigh A.; Kleidman, Richard G.; Patadia, Falguni; Gupta, Pawan; Remer, Lorraine

    2013-01-01

    Aerosol retrieval algorithms are applied to Moderate resolution Imaging Spectroradiometer (MODIS) sensors on both Terra and Aqua, creating two streams of decade-plus aerosol information. Products of aerosol optical depth (AOD) and aerosol size are used for many applications, but the primary concern is that these global products are comprehensive and consistent enough for use in climate studies. One of our major customers is the international modeling comparison study known as AEROCOM, which relies on the MODIS data as a benchmark. In order to keep up with the needs of AEROCOM and other MODIS data users, while utilizing new science and tools, we have improved the algorithms and products. The code, and the associated products, will be known as Collection 6 (C6). While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. In its entirety, the C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties over different surfaces: These include the dark-target DT algorithms to retrieve over (1) ocean and (2) vegetated-dark-soiled land, plus the (3) Deep Blue (DB) algorithm, originally developed to retrieve over desert-arid land. Focusing on the two DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to 84) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such as topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and

  10. Secondary organic aerosol formation exceeds primary particulate matter emissions for light-duty gasoline vehicles

    NASA Astrophysics Data System (ADS)

    Gordon, T. D.; Presto, A. A.; May, A. A.; Nguyen, N. T.; Lipsky, E. M.; Donahue, N. M.; Gutierrez, A.; Zhang, M.; Maddox, C.; Rieger, P.; Chattopadhyay, S.; Maldonado, H.; Maricq, M. M.; Robinson, A. L.

    2014-05-01

    The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter (PM) after 3 h of oxidation inside the chamber at typical atmospheric oxidant levels (and 5 times the amount of SOA as primary PM after 5 × 106 molecules cm-3 h of OH exposure). Therefore, the contribution of light-duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3-7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photooxidizing exhaust from newer (LEV2) vehicles was a factor of 3 lower than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions (a factor of 11-15) in nonmethane organic gas emissions. These data suggest that a complex and nonlinear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the timescale of these experiments, the mixture of organic vapors

  11. Organic nitrate aerosol formation via NO3 + BVOC in the Southeastern US

    NASA Astrophysics Data System (ADS)

    Ayres, B. R.; Allen, H. M.; Draper, D. C.; Brown, S. S.; Wild, R. J.; Jimenez, J. L.; Day, D. A.; Campuzano-Jost, P.; Hu, W.; de Gouw, J.; Koss, A.; Cohen, R. C.; Duffey, K. C.; Romer, P.; Baumann, K.; Edgerton, E.; Takahama, S.; Thornton, J. A.; Lee, B. H.; Lopez-Hilfiker, F. D.; Mohr, C.; Goldstein, A. H.; Olson, K.; Fry, J. L.

    2015-06-01

    Gas- and aerosol-phase measurements of oxidants, biogenic volatile organic compounds (BVOC) and organic nitrates made during the Southern Oxidant and Aerosol Study (SOAS campaign, Summer 2013) in central Alabama show that nitrate radical (NO3) reaction with monoterpenes leads to significant secondary aerosol formation. Cumulative losses of NO3 to terpenes are calculated and correlated to gas and aerosol organic nitrate concentrations made during the campaign. Correlation of NO3 radical consumption to organic nitrate aerosol as measured by Aerosol Mass Spectrometry (AMS) and Thermal Dissociation - Laser Induced Fluorescence (TD-LIF) suggests a range of molar yield of aerosol phase monoterpene nitrates of 23-44 %. Compounds observed via chemical ionization mass spectrometry (CIMS) are correlated to predicted nitrate loss to terpenes and show C10H17NO5, likely a hydroperoxy nitrate, is a major nitrate oxidized terpene product being incorporated into aerosols. The comparable isoprene product C5H9NO5 was observed to contribute less than 0.5 % of the total organic nitrate in the aerosol-phase and correlations show that it is principally a gas-phase product from nitrate oxidation of isoprene. Organic nitrates comprise between 30 and 45 % of the NOy budget during SOAS. Inorganic nitrates were also monitored and showed that during incidents of increased coarse-mode mineral dust, HNO3 uptake produced nitrate aerosol mass loading comparable to that of organic nitrate produced via NO3 + BVOC.

  12. Organic nitrate aerosol formation via NO3 + biogenic volatile organic compounds in the southeastern United States

    NASA Astrophysics Data System (ADS)

    Ayres, B. R.; Allen, H. M.; Draper, D. C.; Brown, S. S.; Wild, R. J.; Jimenez, J. L.; Day, D. A.; Campuzano-Jost, P.; Hu, W.; de Gouw, J.; Koss, A.; Cohen, R. C.; Duffey, K. C.; Romer, P.; Baumann, K.; Edgerton, E.; Takahama, S.; Thornton, J. A.; Lee, B. H.; Lopez-Hilfiker, F. D.; Mohr, C.; Wennberg, P. O.; Nguyen, T. B.; Teng, A.; Goldstein, A. H.; Olson, K.; Fry, J. L.

    2015-12-01

    Gas- and aerosol-phase measurements of oxidants, biogenic volatile organic compounds (BVOCs) and organic nitrates made during the Southern Oxidant and Aerosol Study (SOAS campaign, Summer 2013) in central Alabama show that a nitrate radical (NO3) reaction with monoterpenes leads to significant secondary aerosol formation. Cumulative losses of NO3 to terpenes are correlated with increase in gas- and aerosol-organic nitrate concentrations made during the campaign. Correlation of NO3 radical consumption to organic nitrate aerosol formation as measured by aerosol mass spectrometry and thermal dissociation laser-induced fluorescence suggests a molar yield of aerosol-phase monoterpene nitrates of 23-44 %. Compounds observed via chemical ionization mass spectrometry (CIMS) are correlated to predicted nitrate loss to BVOCs and show C10H17NO5, likely a hydroperoxy nitrate, is a major nitrate-oxidized terpene product being incorporated into aerosols. The comparable isoprene product C5H9NO5 was observed to contribute less than 1 % of the total organic nitrate in the aerosol phase and correlations show that it is principally a gas-phase product from nitrate oxidation of isoprene. Organic nitrates comprise between 30 and 45 % of the NOy budget during SOAS. Inorganic nitrates were also monitored and showed that during incidents of increased coarse-mode mineral dust, HNO3 uptake produced nitrate aerosol mass loading at a rate comparable to that of organic nitrate produced via NO3 + BVOCs.

  13. The Collection 6 MODIS aerosol products over land and ocean

    NASA Astrophysics Data System (ADS)

    Levy, R. C.; Mattoo, S.; Munchak, L. A.; Remer, L. A.; Sayer, A. M.; Patadia, F.; Hsu, N. C.

    2013-11-01

    The twin Moderate resolution Imaging Spectroradiometer (MODIS) sensors have been flying on Terra since 2000 and Aqua since 2002, creating an extensive data set of global Earth observations. Here, we introduce the Collection 6 (C6) algorithm to retrieve aerosol optical depth (AOD) and aerosol size parameters from MODIS-observed spectral reflectance. While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. The C6 aerosol data set will be created from three separate retrieval algorithms that operate over different surface types. These are the two "Dark Target" (DT) algorithms for retrieving (1) over ocean (dark in visible and longer wavelengths) and (2) over vegetated/dark-soiled land (dark in the visible), plus the "Deep Blue" (DB) algorithm developed originally for retrieving (3) over desert/arid land (bright in the visible). Here, we focus on DT-ocean and DT-land (#1 and #2). We have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to ≤ 84°) to increase poleward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season/location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence on the surface reflectance, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. At the same time, we quantified how "upstream" changes to instrument calibration, land/sea masking and cloud masking will also impact the statistics of global AOD, and affect Terra and Aqua differently. For Aqua, all changes will result in reduced

  14. Oligomer and SOA formation through aqueous phase photooxidation of methacrolein and methyl vinyl ketone

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Siekmann, Frank; Renard, Pascal; El Zein, Atallah; Salque, Guillaume; El Haddad, Imad; Temime-Roussel, Brice; Voisin, Didier; Thissen, Roland; Monod, Anne

    2012-03-01

    This work investigates the ability of methacrolein (MACR) and methyl vinyl ketone (MVK) (the two main gas phase atmospheric oxidation products of isoprene) to form oligomers and secondary organic aerosol (SOA) upon aqueous phase OH-oxidation and subsequent water evaporation. For the two precursors, electrospray mass spectrometry (in infusion and coupled to liquid chromatography) analysis of the reacting solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1400 Da. More than 11 series of oligomers were found. For MVK, the intensity and masses of oligomers became increasingly important as MVK initial concentrations increased from 0.2 to 20 mM. For both precursors, the oligomers were responsible for the SOA formation during nebulization experiments. The evaluated SOA mass yield ranged from 3.9 to 9.9% for MVK. These yields were time dependent and were in good agreement with the range (1.6-11.7%) obtained for MACR under the same conditions by El Haddad et al. (2009).

  15. Secondary Organic Aerosol formation from the gas-phase ozonolysis of 3-methylcatechol and 4-methylcatechol

    NASA Astrophysics Data System (ADS)

    Coeur-Tourneur, Cécile; Foulon, Valentine; Laréal, Michel; Cassez, Andy; Zhao, Weixiong

    2010-05-01

    Secondary Organic Aerosol (SOA) formation during the ozonolysis of 3-methylcatechol (3-methyl-1,2-dihydroxybenzene) and 4-methylcatechol (3-methyl-1,2-dihydroxybenzene) was investigated using a simulation chamber (8 m3) at atmospheric pressure, room temperature (294 ± 2 K) and low relative humidity (5-10%). The initial mixing ratios were as follows (in ppb): 3-methylcatechol (194-1059), 4-methylcatechol (204-1188) and ozone (93-531). The ozone and methylcatechol concentrations were followed by UV photometry and GC-FID (Gas Chromatography - Flame ionization detector), respectively and the aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted methylcatechol concentrations assuming a particle density of 1.4 g cm-3. The aerosol formation yield increases as the initial methylcatechol concentration increases, and leads to aerosol yields ranging from 32% to 67% and from 30% to 64% for 3-methylcatechol and 4-methylcatechol, respectively. Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. These data are comparable to those published in a recent study on secondary organic aerosol formation from catechol ozonolysis. To our knowledge, this work represents the first investigation of SOA formation from the ozone reaction with methylcatechols.

  16. Determination of aerosol yields from 3-methylcatechol and 4-methylcatechol ozonolysis in a simulation chamber

    NASA Astrophysics Data System (ADS)

    Coeur-Tourneur, Cécile; Foulon, Valentine; Laréal, Michel

    2010-02-01

    Secondary Organic Aerosol (SOA) formation during the ozonolysis of 3-methylcatechol (3-methyl-1,2-dihydroxybenzene) and 4-methylcatechol (3-methyl-1,2-dihydroxybenzene) was investigated using a simulation chamber (8 m 3) at atmospheric pressure, room temperature (294 ± 2 K) and low relative humidity (5-10%). The initial mixing ratios were as follows (in ppb): 3-methylcatechol (194-1059), 4-methylcatechol (204-1188) and ozone (93-531). The ozone and methylcatechol concentrations were followed by UV photometry and GC-FID (Gas chromatography-Flame ionization detector), respectively and the aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (M o) to the total reacted methylcatechol concentrations assuming a particle density of 1.4 g cm -3. The aerosol formation yield increases as the initial methylcatechol concentration increases, and leads to aerosol yields ranging from 32% to 67% and from 30% to 64% for 3-methylcatechol and 4-methylcatechol, respectively. Y is a strong function of M o and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. These data are comparable to those published in a recent study on secondary organic aerosol formation from catechol ozonolysis. To our knowledge, this work represents the first investigation of SOA formation from the ozone reaction with methylcatechols.

  17. Aqueous SOA formation from radical oligomerization of methyl vinyl ketone (MVK) and methacrolein (MACR)

    NASA Astrophysics Data System (ADS)

    Renard, P.; Siekmann, F.; Ravier, S.; Temime-Roussel, B.; Clément, J.; Ervens, B.; Monod, A.

    2013-12-01

    It is now accepted that one of the important pathways of secondary organic aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the chemical mechanisms leading to macromolecules are still not well understood. It was recently shown that oligomer production by OH radical oxidation in the aerosol aqueous phase from α-dicarbonyl precursors, such as methylglyoxal and glyoxal, is irreversible and fast. We have investigated the aqueous phase photooxidation of MACR and MVK, which are biogenic organic compounds derived from isoprene. Aqueous phase photooxidation of MVK and MACR was investigated in a photoreactor using photolysis of H2O2 as OH radical source. Electrospray high resolution mass spectrometry analysis of the solutions brought clear evidence for the formation of oligomer systems having a mass range of up to 1800 Da within less than 15 minutes of reaction. Highest oligomer formation rates were obtained under conditions of low dissolved oxygen, highest temperature (T = 298 K) and highest precursor initial concentrations ([MVK]0 = 20 mM). A radical mechanism of oligomerization is proposed to explain the formation of the high molecular weight products. Furthermore, we quantified the total amount of carbon present in oligomers. Kinetic parameters of the proposed oligomerization mechanism are constrained by means of a box model that is able to reproduce the temporal evolution of intermediates and products as observed in the laboratory experiments. Additional model simulations for atmospherically-relevant conditions will be presented that show the extent to which these radical processes contribute to SOA formation in the atmospheric multiphase system as compared to other aqueous phase as well as traditional SOA sources. MVK time profile (as measured by UV Spectroscopy) and mass spectra (obtained using UPLC-ESI-MS for the retention time range 0-5 min in the positive mode) at 5, 10 and 50 min of reaction (MVK 20 mM, 25° C, under

  18. A Study on the Aqueous Formation of Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Sinclair, K.; Tsigaridis, K.

    2013-12-01

    The effect aerosols have on radiative forcing in the atmosphere is recognized as one of the largest uncertainties in the radiation budget. About 80% of organic aerosol mass in the atmosphere is estimated to be created though secondary processes. Recently, the aqueous formation of secondary organic aerosols (SOA) has become recognized as important when considering the source, transformation and radiative impacts of SOA. This work focuses on implementing a mechanism for aqueous SOA formation that can be used in atmospheric chemistry and models of all scales, from box to global. A box model containing a simplified chemical mechanism for the aqueous production of precursors of aqueous SOA (Myriokefalitakis et al. (2011) is coupled to gas-phase chemistry which uses the carbon bond mechanism (CBM) IV is presented. The model implements aqueous chemistry of soluble gases, both in-cloud and aerosol water, including organic compounds such as glyoxal and methylglyoxal, which have been shown as potentially significant sources for dissolved secondary organic aerosols. This mechanism implements aqueous phase mass transfer and molecular dissociation. The model's performance is evaluated against previous box model studies from the literature. A comparison is conducted between the detailed GAMMA model (McNeill et al., 2012), which is constrained with chamber experiments and the one developed here. The model output under different atmospheric conditions is explored and differences and sensitivities are assessed. The objective of this work is to create a robust framework for simulating aqueous phase formation of SOA and maximizing the computational efficiency of the model, while maintaining accuracy, in order to later use the exact mechanism in global climate simulations.

  19. Quality Screening Algorithms Implemented in the New CALIPSO Level 3 Aerosol Profile Product

    NASA Astrophysics Data System (ADS)

    Tackett, J. L.; Winker, D. M.; Getzewich, B. J.; Vaughan, M.

    2012-12-01

    Global observations of aerosol extinction profiles can improve the ability of climate models to properly account for aerosol radiative forcing in Earth's atmosphere. In response to this need, a new CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) level 3 aerosol profile product has been released which for the first time provides monthly, globally gridded and quality-screened aerosol extinction profiles within the troposphere for the entire 6-year mission. Level 3 aerosol extinction profiles are aggregated from CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar extinction retrievals reported in the CALIPSO level 2 aerosol profile product onto an equal-angle grid after quality screening algorithms are applied to reduce occurrences of failed retrievals, misclassified aerosol, surface contamination, and spurious outliers. Implementation of these quality screening algorithms is a substantial value to aerosol modeling groups who desire high confidence datasets without having to independently develop quality screening metrics. Furthermore, quality screening is paramount to understand the scientific content of the resultant CALIPSO level 3 aerosol profile product since classification and retrieval errors in level 2 aerosol data may lead to misinterpretation of the distribution and optical properties of aerosol in the troposphere. This presentation summarizes the averaging and quality screening algorithms implemented in the CALIPSO level 3 aerosol profile product, provides rationale for their implementation, and discusses averaging and filtering differences unique to CALIPSO data compared to level 3 products aggregated from passive satellite measurements. Examples are given that illustrate the benefits of quality screening and the dangers of improper screening CALIPSO level 2 aerosol extinction data. Sensitivity study results are presented to highlight the impact of quality screening on final level 3 statistics. Since overlying cloud

  20. Assessing the impact of anthropogenic pollution on isoprene-derived secondary organic aerosol formation in PM2.5 collected from the Birmingham, Alabama, ground site during the 2013 Southern Oxidant and Aerosol Study

    NASA Astrophysics Data System (ADS)

    Rattanavaraha, Weruka; Chu, Kevin; Hapsari Budisulistiorini, Sri; Riva, Matthieu; Lin, Ying-Hsuan; Edgerton, Eric S.; Baumann, Karsten; Shaw, Stephanie L.; Guo, Hongyu; King, Laura; Weber, Rodney J.; Neff, Miranda E.; Stone, Elizabeth A.; Offenberg, John H.; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.

    2016-04-01

    In the southeastern US, substantial emissions of isoprene from deciduous trees undergo atmospheric oxidation to form secondary organic aerosol (SOA) that contributes to fine particulate matter (PM2.5). Laboratory studies have revealed that anthropogenic pollutants, such as sulfur dioxide (SO2), oxides of nitrogen (NOx), and aerosol acidity, can enhance SOA formation from the hydroxyl radical (OH)-initiated oxidation of isoprene; however, the mechanisms by which specific pollutants enhance isoprene SOA in ambient PM2.5 remain unclear. As one aspect of an investigation to examine how anthropogenic pollutants influence isoprene-derived SOA formation, high-volume PM2.5 filter samples were collected at the Birmingham, Alabama (BHM), ground site during the 2013 Southern Oxidant and Aerosol Study (SOAS). Sample extracts were analyzed by gas chromatography-electron ionization-mass spectrometry (GC/EI-MS) with prior trimethylsilylation and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS) to identify known isoprene SOA tracers. Tracers quantified using both surrogate and authentic standards were compared with collocated gas- and particle-phase data as well as meteorological data provided by the Southeastern Aerosol Research and Characterization (SEARCH) network to assess the impact of anthropogenic pollution on isoprene-derived SOA formation. Results of this study reveal that isoprene-derived SOA tracers contribute a substantial mass fraction of organic matter (OM) ( ˜ 7 to ˜ 20 %). Isoprene-derived SOA tracers correlated with sulfate (SO42-) (r2 = 0.34, n = 117) but not with NOx. Moderate correlations between methacrylic acid epoxide and hydroxymethyl-methyl-α-lactone (together abbreviated MAE/HMML)-derived SOA tracers with nitrate radical production (P[NO3]) (r2 = 0.57, n = 40) were observed during nighttime, suggesting a potential role of the NO3 radical in

  1. Secondary Organic Aerosol Formation from Ultra-Low Super Ultra-Low and Partial Zero Emission Vehicle Exhaust

    NASA Astrophysics Data System (ADS)

    Robinson, A. L.; Zhao, Y.; Lambe, A. T.; Saleh, R.; Saliba, G.; Maldonado, H.; Sardar, S.; Frodin, B.; Drozd, G.; Goldstein, A. H.; Kroll, J. H.; Cross, E. S.; Franklin, J. P.

    2015-12-01

    Secondary organic aerosol (SOA) is the dominant component of organic aerosol in many urban areas during the summertime. On-road light duty gasoline vehicles (LDGV) have been indicated as a major source of SOA precursors. Emissions of the SOA-forming non methane hydrocarbons (NMHCs) from on-road LDGV have been substantially reduced along with more stringent emission standards, leading to reduced potential for SOA formation. However, recent smog chamber measurements reported that the reductions in SOA formation were less than those in NMHC emissions, indicating that newer, low emitting vehicles may emit a more efficient of SOA precursors. Vehicles that meet the ultra-low, super ultra-low and partial zero emission standards have substantially lower NMHC emissions than vehicles tested in past studies. To better understand the effects of more stringent emission controls on the SOA formation, we conducted experiments 13 vehicles recruited from the Southern California vehicle fleet (five ultra-low emission vehicles, four super ultra-low emission vehicles and four partial zero emission vehicles) at the California Air Resources Board Haagen-Smit Laboratory. In addition, we investigated several vehicles compliant with older emission standards have also been investigated here to bridge the previous studies. Dilute vehicle exhaust were photo-oxidized in a smog chamber with the VOC-to-NOx ratio adjusted to simulate the photochemistry in urban air. Application of literature data from single-ring aromatic compounds cannot explain the observed SOA during chamber experiments. The average ratios between estimated and measured SOA for vehicles under different emission standards ranged from 0.04 to 0.71. Comprehensive measurements of SOA precursor emissions were made, including NMHCs, intermediate volatility and semi-volatile organic compounds. This study presents results of SOA production from these low emitting vehicles and compares the results with recently published data. This

  2. SOA formation from naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene photooxidation

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Li; Kacarab, Mary; Tang, Ping; Cocker, David R.

    2016-04-01

    The SOA yield and chemical characteristics of SOA formation from naphthalene and two methyl substituted naphthalenes, 1-methylnaphthalene and 2-methylnaphthalene, were studied for high NOx, low NOx, and ultra-low NOx conditions. The SOA yields are high compared to previous studies for all three PAHs precursors: 1-methylnaphthalene > 2-methylnaphthalene ∼ naphthalene for all atmospheric conditions studied. The SOA yields range from 0.03 to 0.60 for naphthalene, 0.21-1.52 for 1-methylnaphthalene, and 0.34-0.55 for 2-methylnaphthalene under high NOx with HONO (initial PAH:NO ratio = 0.03-0.17) conditions. The SOA yield ranges from 0.04 to 0.31 for naphthalene, 0.14-0.72 for 1-methylnaphthalene, and 0.06-0.49 for 2-methylnaphthalene under low NOx (initial PAH:NO ratio = 0.54-2.20) conditions. SOA yields were substantially greater than 1.0 under H2O2 (ultra low NOx) and low NOx + H2O2 conditions for all three PAH precursors. The system reactivity influenced by OH radicals, NOx levels, initial PAH/NO ratios, NO2/NO ratios, and all impacted the SOA formation from the PAH precursors. Fractal-like SOA is observed for the methylnaphthalene isomers during high NOx photooxidation experiments, implying that researchers studying SOA formation from this precursor must carefully account for particle shape or effective density. A m/z 104 (C7H4O+,104.026) peak, consistent with SOA products phthalic acid from earlier studies, was observed as a potential marker of PAH oxidation during HR-ToF-AMS analysis.

  3. Integrating phase and composition of secondary organic aerosol from the ozonolysis of α-pinene

    PubMed Central

    Kidd, Carla; Perraud, Véronique; Wingen, Lisa M.; Finlayson-Pitts, Barbara J.

    2014-01-01

    Airborne particles are important for public health, visibility, and climate. Predicting their concentrations, effects, and responses to control strategies requires accurate models of their formation and growth in air. This is challenging, as a large fraction is formed by complex reactions of volatile organic compounds, generating secondary organic aerosol (SOA), which grows to sizes important for visibility, climate, and deposition in the lung. Growth of SOA is particularly sensitive to the phase/viscosity of the particles and remains poorly understood. We report studies using a custom-designed impactor with a germanium crystal as the impaction surface to study SOA formed from the ozonolysis of α-pinene at relative humidities (RHs) up to 87% at 297 ± 2 K (which corresponds to a maximum RH of 70–86% inside the impactor). The impaction patterns provide insight into changes in phase/viscosity as a function of RH. Attenuated total reflectance-Fourier transform infrared spectroscopy and aerosol mass spectrometry provide simultaneous information on composition changes with RH. The results show that as the RH at which the SOA is formed increases, there is a decrease in viscosity, accompanied by an increasing contribution from carboxylic acids and a decreasing contribution from higher molecular mass products. In contrast, SOA that is formed dry and subsequently humidified remains solid to high RH. The results of these studies have significant implications for modeling the growth, aging, and ultimately, lifetime of SOA in the atmosphere. PMID:24821796

  4. Effect of Pellet Boiler Exhaust on Secondary Organic Aerosol Formation from α-Pinene.

    PubMed

    Kari, Eetu; Hao, Liqing; Yli-Pirilä, Pasi; Leskinen, Ari; Kortelainen, Miika; Grigonyte, Julija; Worsnop, Douglas R; Jokiniemi, Jorma; Sippula, Olli; Faiola, Celia L; Virtanen, Annele

    2017-02-07

    Interactions between anthropogenic and biogenic emissions, and implications for aerosol production, have raised particular scientific interest. Despite active research in this area, real anthropogenic emission sources have not been exploited for anthropogenic-biogenic interaction studies until now. This work examines these interactions using α-pinene and pellet boiler emissions as a model test system. The impact of pellet boiler emissions on secondary organic aerosol (SOA) formation from α-pinene photo-oxidation was studied under atmospherically relevant conditions in an environmental chamber. The aim of this study was to identify which of the major pellet exhaust components (including high nitrogen oxide (NOx), primary particles, or a combination of the two) affected SOA formation from α-pinene. Results demonstrated that high NOx concentrations emitted by the pellet boiler reduced SOA yields from α-pinene, whereas the chemical properties of the primary particles emitted by the pellet boiler had no effect on observed SOA yields. The maximum SOA yield of α-pinene in the presence of pellet boiler exhaust (under high-NOx conditions) was 18.7% and in the absence of pellet boiler exhaust (under low-NOx conditions) was 34.1%. The reduced SOA yield under high-NOx conditions was caused by changes in gas-phase chemistry that led to the formation of organonitrate compounds.

  5. Effect of SO2 concentration on SOA formation in a photorreactor from a mixture of anthropogenic hydrocarbons and HONO

    NASA Astrophysics Data System (ADS)

    García Vivanco, Marta; Santiago, Manuel; García Diego, Cristina; Borrás, Esther; Ródenas, Milagros; Martínez-Tarifa, Adela

    2010-05-01

    Sulfur dioxide (SO2) is an important urban atmospheric pollutant, mainly produced by the combustion of fossil fuels containing sulfur. In the atmosphere, SO2 can react with OH radicals to form sulfuric acid, which can condense to form acidic aerosol. Sulfuric acid particles act as an acid catalyst for some heterogeneous carbonyl reactions like hydration, polymerization or acetals formation, which may lead to a large increase on SOA mass. In order to evaluate the effect of the SO2 concentration on SOA formation, 3 experiments were performed during the campaign carried out by CIEMAT on the EUPHORE facility (CEAM, Valencia, Spain) during June- July 2008. The objective of the campaign was to evaluate the effect of different experimental conditions on SOA formation from the photooxidation of some anthropogenic and biogenic VOCs using HONO as oxidant. Experiment on 6/17/08 was selected as base case (no SO2 was introduced) and experiments 6/26/08 and 7/1/08 were selected as high SO2 (2600 ug/m3) and low SO2 (60 ug/m3) concentration experiments respectively. In the three experiments a mixture of toluene, 1,3,5-TMB (trimethylbenzene), o-xylene and octane was selected as the parent VOCs. Single and coupled to mass spectroscopy gas cromatography (GC and GC/MS), as well as high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR) were used to measure the initial VOCs and oxidant concentrations decay and the formation of gas phase oxidation products through the experiments. Aerosol size distribution and concentration were measured with SMPS (scanning mobility particle sizer) and TEOM (tapered element oscillating monitor) respectively. In addition, analysis of the organic and inorganic aerosol content was also performed via filter sampling followed by GC/MS and ionic chromatography (for organic and inrganic content respectively). Comparing the filters collected in the three experiments, clearly the largest mass aerosol formation is observed

  6. Fungal spores overwhelm biogenic organic aerosols in a midlatitudinal forest

    NASA Astrophysics Data System (ADS)

    Zhu, Chunmao; Kawamura, Kimitaka; Fukuda, Yasuro; Mochida, Michihiro; Iwamoto, Yoko

    2016-06-01

    Both primary biological aerosol particles (PBAPs) and oxidation products of biogenic volatile organic compounds (BVOCs) contribute significantly to organic aerosols (OAs) in forested regions. However, little is known about their relative importance in diurnal timescales. Here, we report biomarkers of PBAP and secondary organic aerosols (SOAs) for their diurnal variability in a temperate coniferous forest in Wakayama, Japan. Tracers of fungal spores, trehalose, arabitol and mannitol, showed significantly higher levels in nighttime than daytime (p < 0.05), resulting from the nocturnal sporulation under near-saturated relative humidity. On the contrary, BVOC oxidation products showed higher levels in daytime than nighttime, indicating substantial photochemical SOA formation. Using tracer-based methods, we estimated that fungal spores account for 45 % of organic carbon (OC) in nighttime and 22 % in daytime, whereas BVOC oxidation products account for 15 and 19 %, respectively. To our knowledge, we present for the first time highly time-resolved results that fungal spores overwhelmed BVOC oxidation products in contributing to OA especially in nighttime. This study emphasizes the importance of both PBAPs and SOAs in forming forest organic aerosols.

  7. Oil Sands Operations in Alberta, Canada: A large source of secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S. M.; Hayden, K.; Taha, Y. M.; Stroud, C.; Darlington, A. L.; Drollette, B.; Gordon, M.; Lee, P.; Liu, P.; Leithead, A.; Moussa, S.; Wang, D.; O'Brien, J.; Mittermeier, R. L.; Brook, J.; Lu, G.; Staebler, R. M.; Han, Y.; Tokarek, T. W.; Osthoff, H. D.; Makar, P.; Zhang, J.; Plata, D.; Gentner, D. R.

    2015-12-01

    Little is known of the reaction products of emissions to the atmosphere from extraction of oil from unconventional sources in the oil sands (OS) region of Alberta, Canada. This study examines these reaction products, and in particular, the extent to which they form secondary organic aerosol (SOA), which can significantly contribute to regional particulate matter formation. An aircraft measurement campaign was conducted over the Athabasca oil sands region between August 13 and September 7, 2013. A broad suite of measurements were made during 22 flights, including organic aerosol mass and composition with a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and organic aerosol gas-phase precursors by Proton Transfer Reaction (PTR) and off-line gas chromatography mass spectrometry. Large concentrations of organic aerosol were measured downwind of the OS region, which we show to be entirely secondary in nature. Laboratory experiments demonstrated that bitumen (the mined product) contains semi-volatile vapours in the C12-C18 range that will be emitted at ambient temperatures. When oxidized, these vapours form SOA with highly similar HR-ToF-AMS spectra to the SOA measured in the flights. Box modelling of the OS plume evolution indicated that the measured levels of traditional volatile organic compounds (VOCs) are not capable of accounting for the amount of SOA formed in OS plumes. This discrepancy is only reconciled in the model by including bitumen vapours along with their oxidation and condensation into the model. The concentration of bitumen vapours required to produce SOA matching observations is similar to that of traditional VOC precursors of SOA. It was further estimated that the cumulative SOA mass formation approximately 100 km downwind of the OS during these flights, and under these meteorological conditions was up to 82 tonnes/day. The combination of airborne measurements, laboratory experiments and box modelling indicated that semi

  8. Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene.

    PubMed

    Hao, Li-qing; Wang, Zhen-ya; Huang, Ming-qiang; Fang, Li; Zhang, Wei-jun

    2007-01-01

    Hydroxyl radical (.OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols (SOA). It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride>sodium silicate and ammonium nitrate>ammonium sulfate.

  9. SOA formation by biogenic and carbonyl compounds: data evaluation and application.

    PubMed

    Ervens, Barbara; Kreidenweis, Sonia M

    2007-06-01

    The organic fraction of atmospheric aerosols affects the physical and chemical properties of the particles and their role in the climate system. Current models greatly underpredict secondary organic aerosol (SOA) mass. Based on a compilation of literature studies that address SOA formation, we discuss different parameters that affect the SOA formation efficiency of biogenic compounds (alpha-pinene, isoprene) and aliphatic aldehydes (glyoxal, hexanal, octanal, hexadienal). Applying a simple model, we find that the estimated SOA mass after one week of aerosol processing under typical atmospheric conditions is increased by a few microg m(-3) (low NO(x) conditions). Acid-catalyzed reactions can create > 50% more SOA mass than processes under neutral conditions; however, other parameters such as the concentration ratio of organics/NO(x), relative humidity, and absorbing mass are more significant. The assumption of irreversible SOA formation not limited by equilibrium in the particle phase or by depletion of the precursor leads to unrealistically high SOA masses for some of the assumptions we made (surface vs volume controlled processes).

  10. Resistance of Aerosolized Bacterial Viruses to Four Germicidal Products

    PubMed Central

    Turgeon, Nathalie; Michel, Kevin; Ha, Thi-Lan; Robine, Enric; Moineau, Sylvain; Duchaine, Caroline

    2016-01-01

    Viral diseases can spread through a variety of routes including aerosols. Yet, limited data are available on the efficacy of aerosolized chemicals to reduce viral loads in the air. Bacteriophages (phages) are often used as surrogates for hazardous viruses in aerosol studies because they are inexpensive, easy to handle, and safe for laboratory workers. Moreover, several of these bacterial viruses display physical characteristics similar to pathogenic human and animal viruses, like morphological size, type of nucleic acids, capsid morphology, and the presence of an envelope. In this study, the efficacy of four chemicals was evaluated on four airborne phages at two different relative humidity levels. Non-tailed bacteriophages MS2 (single-stranded RNA), ϕ6 (double-stranded RNA, enveloped), PR772 (double-stranded DNA), and ϕX174 (single-stranded DNA) were first aerosolized in a 55L rotative environmental chamber at 19°C with 25% and 50% relative humidity. Then, hydrogen peroxide, Eugenol (phenylpropene used in commercial perfumes and flavorings), Mist® (automobile disinfectant containing Triethylene glycol), and Pledge® (multisurface disinfectant containing Isopropanol, n-Alkyl Dimethyl Benzyl Amonium Chlorides, and n-Alkyl Dimethyl Ethylbenzyl Ammonium Chloride) were nebulized with the phages using a separate nebulizer. Aerosols were maintained in suspension during 10 minutes, 1 hour, and 2 hours. Viral aerosols were sampled using an SKC BioSampler and samples were analyzed using qPCR and plaque assays. The resistance levels of the four phages varied depending on the relative humidity (RH) and germicidal products tested. Phage MS2 was the most stable airborne virus under the environmental conditions tested while phage PR772 was the least stable. Pledge® and Eugenol reduced the infectivity of all airborne phages tested. At 25% RH, Pledge® and Eugenol were more effective at reducing infectivity of RNA phages ϕ6 and MS2. At 50% RH, Pledge® was the most effective

  11. Sensitivity analysis of simulated SOA loadings using a variance-based statistical approach

    NASA Astrophysics Data System (ADS)

    Shrivastava, Manish; Zhao, Chun; Easter, Richard C.; Qian, Yun; Zelenyuk, Alla; Fast, Jerome D.; Liu, Ying; Zhang, Qi; Guenther, Alex

    2016-06-01

    We investigate the sensitivity of secondary organic aerosol (SOA) loadings simulated by a regional chemical transport model to seven selected model parameters using a modified volatility basis-set (VBS) approach: four involving emissions of anthropogenic and biogenic volatile organic compounds, anthropogenic semivolatile and intermediate volatility organics (SIVOCs), and NOx; two involving dry deposition of SOA precursor gases, and one involving particle-phase transformation of SOA to low volatility. We adopt a quasi-Monte Carlo sampling approach to effectively sample the high-dimensional parameter space, and perform a 250 member ensemble of simulations using a regional model, accounting for some of the latest advances in SOA treatments based on our recent work. We then conduct a variance-based sensitivity analysis using the generalized linear model method to study the responses of simulated SOA loadings to the model parameters. Analysis of SOA variance from all 250 simulations shows that the volatility transformation parameter, which controls whether or not SOA that starts as semivolatile is rapidly transformed to nonvolatile SOA by particle-phase processes such as oligomerization and/or accretion, is the dominant contributor to variance of simulated surface-level daytime SOA (65% domain average contribution). We also split the simulations into two subsets of 125 each, depending on whether the volatility transformation is turned on/off. For each subset, the SOA variances are dominated by the parameters involving biogenic VOC and anthropogenic SIVOC emissions. Furthermore, biogenic VOC emissions have a larger contribution to SOA variance when the SOA transformation to nonvolatile is on, while anthropogenic SIVOC emissions have a larger contribution when the transformation is off. NOx contributes less than 4.3% to SOA variance, and this low contribution is mainly attributed to dominance of intermediate to high NOx conditions throughout the simulated domain. However

  12. MISR Global Aerosol Product Assessment by Comparison with AERONET

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph A.; Gaitley, Barbara J.; Garay, Michael J.; Diner, David J.; Eck, Thomas F.; Smirnov, Alexander; Holben, Brent N.

    2010-01-01

    A statistical approach is used to assess the quality of the MISR Version 22 (V22) aerosol products. Aerosol Optical Depth (AOD) retrieval results are improved relative to the early post- launch values reported by Kahn et al. [2005a], varying with particle type category. Overall, about 70% to 75% of MISR AOD retrievals fall within 0.05 or 20% AOD of the paired validation data, and about 50% to 55% are within 0.03 or 10% AOD, except at sites where dust, or mixed dust and smoke, are commonly found. Retrieved particle microphysical properties amount to categorical values, such as three groupings in size: "small," "medium," and "large." For particle size, ground-based AERONET sun photometer Angstrom Exponents are used to assess statistically the corresponding MISR values, which are interpreted in terms of retrieved size categories. Coincident Single-Scattering Albedo (SSA) and fraction AOD spherical data are too limited for statistical validation. V22 distinguishes two or three size bins, depending on aerosol type, and about two bins in SSA (absorbing vs. non-absorbing), as well as spherical vs. non-spherical particles, under good retrieval conditions. Particle type sensitivity varies considerably with conditions, and is diminished for mid-visible AOD below about 0.15 or 0.2. Based on these results, specific algorithm upgrades are proposed, and are being investigated by the MISR team for possible implementation in future versions of the product.

  13. Understanding sources of organic aerosol during CalNex-2010 using the CMAQ-VBS

    DOE PAGES

    Woody, Matthew C.; Baker, Kirk R.; Hayes, Patrick L.; ...

    2016-03-29

    Community Multiscale Air Quality (CMAQ) model simulations utilizing the traditional organic aerosol (OA) treatment (CMAQ-AE6) and a volatility basis set (VBS) treatment for OA (CMAQ-VBS) were evaluated against measurements collected at routine monitoring networks (Chemical Speciation Network (CSN) and Interagency Monitoring of Protected Visual Environments (IMPROVE)) and those collected during the 2010 California at the Nexus of Air Quality and Climate Change (CalNex) field campaign to examine important sources of OA in southern California. Traditionally, CMAQ treats primary organic aerosol (POA) as nonvolatile and uses a two-product framework to represent secondary organic aerosol (SOA) formation. CMAQ-VBS instead treats POA asmore » semivolatile and lumps OA using volatility bins spaced an order of magnitude apart. The CMAQ-VBS approach underpredicted organic carbon (OC) at IMPROVE and CSN sites to a greater degree than CMAQ-AE6 due to the semivolatile POA treatment. However, comparisons to aerosol mass spectrometer (AMS) measurements collected at Pasadena, CA, indicated that CMAQ-VBS better represented the diurnal profile and primary/secondary split of OA. CMAQ-VBS SOA underpredicted the average measured AMS oxygenated organic aerosol (OOA, a surrogate for SOA) concentration by a factor of 5.2, representing a considerable improvement to CMAQ-AE6 SOA predictions (factor of 24 lower than AMS). We use two new methods, one based on species ratios (SOA/ΔCO and SOA/Ox) and another on a simplified SOA parameterization, to apportion the SOA underprediction for CMAQ-VBS to slow photochemical oxidation (estimated as 1.5 ×  lower than observed at Pasadena using −log(NOx : NOy)), low intrinsic SOA formation efficiency (low by 1.6 to 2 ×  for Pasadena), and low emissions or excessive dispersion for the Pasadena site (estimated to be 1.6 to 2.3 ×  too low/excessive). The first and third factors are common to CMAQ-AE6, while the intrinsic SOA formation

  14. Understanding sources of organic aerosol during CalNex-2010 using the CMAQ-VBS

    NASA Astrophysics Data System (ADS)

    Woody, Matthew C.; Baker, Kirk R.; Hayes, Patrick L.; Jimenez, Jose L.; Koo, Bonyoung; Pye, Havala O. T.

    2016-03-01

    Community Multiscale Air Quality (CMAQ) model simulations utilizing the traditional organic aerosol (OA) treatment (CMAQ-AE6) and a volatility basis set (VBS) treatment for OA (CMAQ-VBS) were evaluated against measurements collected at routine monitoring networks (Chemical Speciation Network (CSN) and Interagency Monitoring of Protected Visual Environments (IMPROVE)) and those collected during the 2010 California at the Nexus of Air Quality and Climate Change (CalNex) field campaign to examine important sources of OA in southern California. Traditionally, CMAQ treats primary organic aerosol (POA) as nonvolatile and uses a two-product framework to represent secondary organic aerosol (SOA) formation. CMAQ-VBS instead treats POA as semivolatile and lumps OA using volatility bins spaced an order of magnitude apart. The CMAQ-VBS approach underpredicted organic carbon (OC) at IMPROVE and CSN sites to a greater degree than CMAQ-AE6 due to the semivolatile POA treatment. However, comparisons to aerosol mass spectrometer (AMS) measurements collected at Pasadena, CA, indicated that CMAQ-VBS better represented the diurnal profile and primary/secondary split of OA. CMAQ-VBS SOA underpredicted the average measured AMS oxygenated organic aerosol (OOA, a surrogate for SOA) concentration by a factor of 5.2, representing a considerable improvement to CMAQ-AE6 SOA predictions (factor of 24 lower than AMS). We use two new methods, one based on species ratios (SOA/ΔCO and SOA/Ox) and another on a simplified SOA parameterization, to apportion the SOA underprediction for CMAQ-VBS to slow photochemical oxidation (estimated as 1.5 × lower than observed at Pasadena using -log(NOx : NOy)), low intrinsic SOA formation efficiency (low by 1.6 to 2 × for Pasadena), and low emissions or excessive dispersion for the Pasadena site (estimated to be 1.6 to 2.3 × too low/excessive). The first and third factors are common to CMAQ-AE6, while the intrinsic SOA formation efficiency for that model is

  15. On the mixing and evaporation of secondary organic aerosol components.

    PubMed

    Loza, Christine L; Coggon, Matthew M; Nguyen, Tran B; Zuend, Andreas; Flagan, Richard C; Seinfeld, John H

    2013-06-18

    The physical state and chemical composition of an organic aerosol affect its degree of mixing and its interactions with condensing species. We present here a laboratory chamber procedure for studying the effect of the mixing of organic aerosol components on particle evaporation. The procedure is applied to the formation of secondary organic aerosol (SOA) from α-pinene and toluene photooxidation. SOA evaporation is induced by heating the chamber aerosol from room temperature (25 °C) to 42 °C over 7 h and detected by a shift in the peak diameter of the SOA size distribution. With this protocol, α-pinene SOA is found to be more volatile than toluene SOA. When SOA is formed from the two precursors sequentially, the evaporation behavior of the SOA most closely resembles that of SOA from the second parent hydrocarbon, suggesting that the structure of the mixed SOA resembles a core of SOA from the initial precursor coated by a layer of SOA from the second precursor. Such a core-and-shell configuration of the organic aerosol phases implies limited mixing of the SOA from the two precursors on the time scale of the experiments, consistent with a high viscosity of at least one of the phases.

  16. Characterization of secondary organic aerosol generated from ozonolysis of α-pinene mixtures

    NASA Astrophysics Data System (ADS)

    Amin, Hardik S.; Hatfield, Meagan L.; Huff Hartz, Kara E.

    2013-03-01

    In the atmosphere, multiple volatile organic compounds (VOCs) co-exist, and they can be oxidized concurrently and generate secondary organic aerosol (SOA). In this work, SOA is formed by the oxidation (in presence of excess ozone) of mixtures containing α-pinene and other VOCs. The VOC mixtures were made so their composition approached a commercially-available α-pinene-based essential oil, Siberian fir needle oil. The SOA products were sampled using filters, solvent extracted and analyzed by gas chromatography/mass spectrometry with trimethylsilyl derivatization. The individual product yields for SOA generated from α-pinene changed upon the addition of other VOCs. An increase in concentration of non-reactive VOCs (bornyl acetate, camphene, and borneol) lead to a decrease in individual product yields of characteristic α-pinene SOA products. Although these experiments were carried out under higher VOC and ozone concentrations in comparison to the atmosphere, this work suggests that the role of non-reactive VOCs should be explored in SOA products formation.

  17. Organic Aerosol Formation Photoenhanced by the Formation of Secondary Photo-sensitizers in ageing Aerosols

    NASA Astrophysics Data System (ADS)

    Aregahegn, Kifle; Nozière, Barbara; George, Christian

    2013-04-01

    Humankind is facing a changing environment possibly due to anthropogenic stress on the atmosphere. In this context, aerosols play a key role by affecting the radiative climate forcing, hydrological cycle, and by their adverse effect on health. The role of organic compounds in these processes is however still poorly understood because of their massive chemical complexity and numerous transformations. This is particularly true for Secondary Organic Aerosol (SOA), which are produced in the atmosphere by organic gases. Traditionally, the driving forces for SOA growth is believed to be the partitioning onto aerosol seeds of condensable gases, either emitted primarily or resulting from the gas phase oxidation of organic gases. However, even the most up-to-date models based on such mechanisms can not account for the SOA mass observed in the atmosphere, suggesting the existence of other, yet unknown formation processes. The present study shows experimental evidence that particulate phase chemistry produces photo-sensitizers that lead to photo-induced formation and growth of secondary organic aerosol in the near UV and the presence of volatile organic compounds (VOC) such as terpenes. By means of an aerosol flow tube reactor equipped with Scanning Mobility Particle Sizer (SMPS) having Kr-85 source aerosol neutralizer, Differential Mobility Analyser (DMA) and Condensation Particle Sizer (CPC), we identified that traces of the aerosol phase product of glyoxal chemistry as is explained in Gallway et al., and Yu et al., namely imidazole-2-carboxaldehyde (IC) is a strong photo-sensitizer when irradiated by near-UV in the presence of volatile organic compounds such as terpenes. Furthermore, the influence of pH, type and concentration of VOCs, composition of seed particles, relative humidity and irradiation intensity on particle growth were studied. This novel photo-sensitizer contributed to more than 30% of SOA growth in 19min irradiation time in the presence of terpenes in the

  18. A Combined Kinetic and Volatility Basis Set Approach to Model Secondary Organic Aerosol from Toluene and Diesel Exhaust/Meat Cooking Mixtures

    NASA Astrophysics Data System (ADS)

    Parikh, H. M.; Carlton, A. G.; Zhang, H.; Kamens, R.; Vizuete, W.

    2011-12-01

    Secondary organic aerosol (SOA) is simulated for 6 outdoor smog chamber experiments using a SOA model based on a kinetic chemical mechanism in conjunction with a volatility basis set (VBS) approach. The experiments include toluene, a non-SOA-forming hydrocarbon mixture, diesel exhaust or meat cooking emissions and NOx, and are performed under varying conditions of relative humidity. SOA formation from toluene is modeled using a condensed kinetic aromatic mechanism that includes partitioning of lumped semi-volatile products in particle organic-phase and incorporates particle aqueous-phase chemistry to describe uptake of glyoxal and methylglyoxal. Modeling using the kinetic mechanism alone, along with primary organic aerosol (POA) from diesel exhaust (DE) /meat cooking (MC) fails to simulate the rapid SOA formation at the beginning hours of the experiments. Inclusion of a VBS approach with the kinetic mechanism to characterize the emissions and chemistry of complex mixture of intermediate volatility organic compounds (IVOCs) from DE/MC, substantially improves SOA predictions when compared with observed data. The VBS model includes photochemical aging of IVOCs and evaporation of POA after dilution. The relative contribution of SOA mass from DE/MC is as high as 95% in the morning, but substantially decreases after mid-afternoon. For high humidity experiments, aqueous-phase SOA fraction dominates the total SOA mass at the end of the day (approximately 50%). In summary, the combined kinetic and VBS approach provides a new and improved framework to semi-explicitly model SOA from VOC precursors in conjunction with a VBS approach that can be used on complex emission mixtures comprised with hundreds of individual chemical species.

  19. CCN activity of aliphatic amine secondary aerosol

    NASA Astrophysics Data System (ADS)

    Tang, X.; Price, D.; Praske, E.; Vu, D.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-01-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3), contains less volatile compounds than the primary aliphatic amine (BA) aerosol. TMA + N2O5 form semi-volatile organics in low RH conditions that have κ ~ 0.20, indicative of slightly soluble organic material. As RH increases, several inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. Higher CCN activity (κ > 0.3) was also observed for humid BA+N2O5 aerosols compared with dry aerosol (κ ~ 0.2), as a result of the formation of inorganic salts such as NH4NO3 and butylamine nitrate (C4H11N · HNO3). Compared with TMA, BA+N2O5 reactions produce more volatile aerosols. The BA+N2O5 aerosol products under humid experiments were found to be very sensitive to the temperature within the stream-wise continuous flow thermal gradient CCN counter. The CCN counter, when set above a 21 °C temperature difference, evaporates BA+N2O5 aerosol formed at RH ≥ 30%; κ ranges from 0.4 to 0.7 and is dependent on the instrument supersaturation (ss) settings. The aerosol behaves non-ideally, hence simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems κ ranges from 0.2 < κ < 0.7. This work indicates that

  20. Effect of Hydrophobic Primary Organic Aerosols on Secondary Organic Aerosol Formation from Ozonolysis of α-Pinene

    SciTech Connect

    Song, Chen; Zaveri, Rahul A.; Alexander, M. Lizabeth; Thornton, Joel A.; Madronich, Sasha; Ortega, John V.; Zelenyuk, Alla; Yu, Xiao-Ying; Laskin, Alexander; Maughan, A. D.

    2007-10-16

    Semi-empirical secondary organic aerosol (SOA) models typically assume a well-mixed organic aerosol phase even in the presence of hydrophobic primary organic aerosols (POA). This assumption significantly enhances the modeled SOA yields as additional organic mass is made available to absorb greater amounts of oxidized secondary organic gases than otherwise. We investigate the applicability of this critical assumption by measuring SOA yields from ozonolysis of α-pinene (a major biogenic SOA precursor) in a smog chamber in the absence and in the presence of dioctyl phthalate (DOP) and lubricating oil seed aerosol. These particles serve as surrogates for urban hydrophobic POA. The results show that these POA did not enhance the SOA yields. If these results are found to apply to other biogenic SOA precursors, then the semi-empirical models used in many global models would predict significantly less biogenic SOA mass and display reduced sensitivity to anthropogenic POA emissions than previously thought.

  1. A merged aerosol dataset based on MODIS and MISR Aerosol Optical Depth products

    NASA Astrophysics Data System (ADS)

    Singh, Manoj K.; Gautam, Ritesh; Venkatachalam, Parvatham

    2016-05-01

    Aerosol Optical Depth (AOD) products available from MODIS and MISR observations are widely used for aerosol characterization, and global/environmental change studies. These products are based on different retrieval-algorithms, resolutions, sampling, and cloud-screening schemes, which have led to global/regional biases. Thus a merged product is desirable which bridges this gap by utilizing strengths from each of the sensors. In view of this, we have developed a "merged" AOD product based on MODIS and MISR AOD datasets, using Bayesian principles which takes error distributions from ground-based AOD measurements (from AERONET). Our methodology and resulting dataset are especially relevant in the scenario of combining multi-sensor retrievals for satellite-based climate data records; particularly for long-term studies involving AOD. Specifically for MISR AOD product, we also developed a methodology to produce a gap-filled dataset, using geostatistical methods (e.g. Kriging), taking advantage of available MODIS data. Merged and spatially-complete AOD datasets are inter-compared with other satellite products and with AERONET data at three stations- Kanpur, Jaipur and Gandhi College, in the Indo-Gangetic Plains. The RMSE of merged AOD (0.08-0.09) is lower than MISR (0.11-0.20) and MODIS (0.15-0.27). It is found that merged AOD has higher correlation with AERONET data (r within 0.92-0.95), compared to MISR (0.74-0.86) and MODIS (0.69-0.84) data. In terms of Expected Error, the accuracy of valid merged AOD is found to be superior as percent of merged AOD within error envelope are larger (71-92%), compared to MISR (43-61%) and MODIS (50-70%).

  2. Impact of NOx and OH on secondary organic aerosol formation from β-pinene photooxidation

    NASA Astrophysics Data System (ADS)

    Sarrafzadeh, Mehrnaz; Wildt, Jürgen; Pullinen, Iida; Springer, Monika; Kleist, Einhard; Tillmann, Ralf; Schmitt, Sebastian H.; Wu, Cheng; Mentel, Thomas F.; Zhao, Defeng; Hastie, Donald R.; Kiendler-Scharr, Astrid

    2016-09-01

    In this study, the NOx dependence of secondary organic aerosol (SOA) formation from photooxidation of the biogenic volatile organic compound (BVOC) β-pinene was comprehensively investigated in the Jülich Plant Atmosphere Chamber. Consistent with the results of previous NOx studies we found increases of SOA yields with increasing [NOx] at low-NOx conditions ([NOx]0 < 30 ppb, [BVOC]0 / [NOx]0 > 10 ppbC ppb-1). Furthermore, increasing [NOx] at high-NOx conditions ([NOx]0 > 30 ppb, [BVOC]0 / [NOx]0 ˜ 10 to ˜ 2.6 ppbC ppb-1) suppressed the SOA yield. The increase of SOA yield at low-NOx conditions was attributed to an increase of OH concentration, most probably by OH recycling in NO + HO2 → NO2 + OH reaction. Separate measurements without NOx addition but with different OH primary production rates confirmed the OH dependence of SOA yields. After removing the effect of OH concentration on SOA mass growth by keeping the OH concentration constant, SOA yields only decreased with increasing [NOx]. Measuring the NOx dependence of SOA yields at lower [NO] / [NO2] ratio showed less pronounced increase in both OH concentration and SOA yield. This result was consistent with our assumption of OH recycling by NO and to SOA yields being dependent on OH concentrations. Our results furthermore indicated that NOx dependencies vary for different NOx compositions. A substantial fraction of the NOx-induced decrease of SOA yields at high-NOx conditions was caused by NOx-induced suppression of new particle formation (NPF), which subsequently limits the particle surface where low volatiles condense. This was shown by probing the NOx dependence of SOA formation in the presence of seed particles. After eliminating the effect of NOx-induced suppression of NPF and NOx-induced changes of OH concentrations, the remaining effect of NOx on the SOA yield from β-pinene photooxidation was moderate. Compared to β-pinene, the SOA formation from α-pinene photooxidation was only suppressed by

  3. Secondary organic aerosol formation from the irradiation of simulated automobile exhaust.

    PubMed

    Kleindienst, T E; Corse, E W; Li, W; McIver, C D; Conver, T S; Edney, E O; Driscoll, D J; Speer, R E; Weathers, W S; Tejada, S B

    2002-03-01

    A laboratory study was conducted to evaluate the potential for secondary organic aerosol formation from emissions from automotive exhaust. The goal was to determine to what extent photochemical oxidation products of these hydrocarbons contribute to secondary organic aerosol (SOA) and how well their formation is described by recently developed models for SOA formation. The quality of a surrogate was tested by comparing its reactivity with that from irradiations of authentic automobile exhaust. Experiments for secondary particle formation using the surrogate were conducted in a fixed volume reactor operated in a dynamic mode. The mass concentration of the aerosol was determined from measurements of organic carbon collected on quartz filters and was corrected for the presence of hydrogen, nitrogen, and oxygen atoms in the organic species. A functional group analysis of the aerosol made by Fourier transform infrared (FTIR) spectroscopy indicated

  4. Classification of Dust Days by Satellite Remotely Sensed Aerosol Products

    NASA Technical Reports Server (NTRS)

    Sorek-Hammer, M.; Cohen, A.; Levy, Robert C.; Ziv, B.; Broday, D. M.

    2013-01-01

    Considerable progress in satellite remote sensing (SRS) of dust particles has been seen in the last decade. From an environmental health perspective, such an event detection, after linking it to ground particulate matter (PM) concentrations, can proxy acute exposure to respirable particles of certain properties (i.e. size, composition, and toxicity). Being affected considerably by atmospheric dust, previous studies in the Eastern Mediterranean, and in Israel in particular, have focused on mechanistic and synoptic prediction, classification, and characterization of dust events. In particular, a scheme for identifying dust days (DD) in Israel based on ground PM10 (particulate matter of size smaller than 10 nm) measurements has been suggested, which has been validated by compositional analysis. This scheme requires information regarding ground PM10 levels, which is naturally limited in places with sparse ground-monitoring coverage. In such cases, SRS may be an efficient and cost-effective alternative to ground measurements. This work demonstrates a new model for identifying DD and non-DD (NDD) over Israel based on an integration of aerosol products from different satellite platforms (Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI)). Analysis of ground-monitoring data from 2007 to 2008 in southern Israel revealed 67 DD, with more than 88 percent occurring during winter and spring. A Classification and Regression Tree (CART) model that was applied to a database containing ground monitoring (the dependent variable) and SRS aerosol product (the independent variables) records revealed an optimal set of binary variables for the identification of DD. These variables are combinations of the following primary variables: the calendar month, ground-level relative humidity (RH), the aerosol optical depth (AOD) from MODIS, and the aerosol absorbing index (AAI) from OMI. A logistic regression that uses these variables, coded as binary

  5. Phase, composition and growth mechanism for secondary organic aerosol from the ozonolysis of α-cedrene

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Wingen, L. M.; Perraud, V.; Finlayson-Pitts, B. J.

    2015-12-01

    Sesquiterpenes are an important class of biogenic volatile organic compounds (BVOCs) and have a high secondary organic aerosol (SOA) forming potential. However, SOA formation from sesquiterpene oxidation has received less attention compared to other BVOCs such as monoterpenes, and the underlying mechanisms remain poorly understood. In this work, we present a comprehensive experimental investigation of the ozonolysis of α-cedrene both in a glass flow reactor (27-44 s reaction times) and in static Teflon chambers (30-60 min reaction times). The SOA was collected by impaction or filters, followed by analysis using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and electrospray ionization mass spectrometry (ESI-MS), or measured on line using direct analysis in real time (DART-MS) and aerosol mass spectrometry (AMS). The slow evaporation of 2-ethylhexyl nitrate that was incorporated into the SOA during its formation and growth gives an estimated diffusion coefficient of 3 × 10-15 cm2 s-1 and shows that SOA is a highly viscous semi-solid. Possible structures of four newly observed low molecular weight (MW ≤ 300 Da) reaction products with higher oxygen content than those previously reported were identified. High molecular weight (HMW) products formed in the early stages of the oxidation have structures consistent with aldol condensation products, peroxyhemiacetals, and esters. The size-dependent distributions of HMW products in the SOA, as well as the effects of stabilized Criegee intermediate (SCI) scavengers on HMW products and particle formation, confirm that HMW products and reactions of Criegee intermediates play a crucial role in early stages of particle formation. Our studies provide new insights into mechanisms of SOA formation and growth in α-cedrene ozonolysis and the important role of sesquiterpenes in new particle formation as suggested by field measurements.

  6. Phase, composition, and growth mechanism for secondary organic aerosol from the ozonolysis of α-cedrene

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Wingen, Lisa M.; Perraud, Véronique; Finlayson-Pitts, Barbara J.

    2016-03-01

    Sesquiterpenes are an important class of biogenic volatile organic compounds (BVOCs) and have a high secondary organic aerosol (SOA) forming potential. However, SOA formation from sesquiterpene oxidation has received less attention compared to other BVOCs such as monoterpenes, and the underlying mechanisms remain poorly understood. In this work, we present a comprehensive experimental investigation of the ozonolysis of α-cedrene both in a glass flow reactor (27-44 s reaction times) and in static Teflon chambers (30-60 min reaction times). The SOA was collected by impaction or filters, followed by analysis using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and electrospray ionization mass spectrometry (ESI-MS), or measured online using direct analysis in real-time mass spectrometry (DART-MS) and aerosol mass spectrometry (AMS). The slow evaporation of 2-ethylhexyl nitrate that was incorporated into the SOA during its formation and growth gives an estimated diffusion coefficient of 3 × 10-15 cm2 s-1 and shows that SOA is a highly viscous semisolid. Possible structures of four newly observed low molecular weight (MW ≤ 300 Da) reaction products with higher oxygen content than those previously reported were identified. High molecular weight (HMW) products formed in the early stages of the oxidation have structures consistent with aldol condensation products, peroxyhemiacetals, and esters. The size-dependent distributions of HMW products in the SOA, as well as the effects of stabilized Criegee intermediate (SCI) scavengers on HMW products and particle formation, confirm that HMW products and reactions of SCI play a crucial role in early stages of particle formation. Our studies provide new insights into mechanisms of SOA formation and growth in α-cedrene ozonolysis and the important role of sesquiterpenes in new particle formation as suggested by field measurements.

  7. CONTRIBUTIONS OF TOLUENE AND Α -PINENE TO SOA FORMED IN AN IRRADIATED TOLUENE/Α-PINENE/NOX/AIR MIXTURE: COMPARISON OF RESULTS USING 14C CONTENT AND SOA ORGANIC TRACER METHODS

    EPA Science Inventory

    An organic tracer method, recently proposed for estimating individual contributions of toluene and α-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydro...

  8. Emissions of biogenic volatile organic compounds and subsequent formation of secondary organic aerosols in a Larix kaempferi forest

    NASA Astrophysics Data System (ADS)

    Mochizuki, T.; Miyazaki, Y.; Ono, K.; Wada, R.; Takahashi, Y.; Saigusa, N.; Kawamura, K.; Tani, A.

    2015-04-01

    We conducted simultaneous measurements of concentrations and above-canopy fluxes of isoprene and α-pinene, along with their oxidation products in aerosols in a Larix kaempferi (Japanese larch) forest in summer 2012. Vertical profiles of isoprene showed the maximum concentration near the forest floor with a peak around noon, whereas oxidation products of isoprene, i.e., methacrolein (MACR) and methyl vinyl ketone (MVK), showed higher concentrations near the canopy level of the forest. The vertical profile suggests large emissions of isoprene near the forest floor, likely due to Dryopteris crassirhizoma (a fern species), and the subsequent reaction within the canopy. The concentrations of α-pinene also showed highest values near the forest floor with maximums in the early morning and late afternoon. The vertical profiles of α-pinene suggest its large emissions from soil and litter in addition to emissions from L. kaempferi leaves at the forest site. Isoprene and its oxidation products in aerosols exhibited similar diurnal variations within the forest canopy, providing evidence for secondary organic aerosol (SOA) formation via oxidation of isoprene most likely emitted from the forest floor. Although high abundance of α-pinene was observed in the morning, its oxidation products in aerosols showed peaks in daytime, due to a time lag between the emission and atmospheric reactions of α-pinene to form SOA. Positive matrix factorization (PMF) analysis indicated that anthropogenic influence is the most important factor contributing to the elevated concentrations of molecular oxidation products of isoprene- (> 64%) and α-pinene-derived SOA (> 57%). The combination of the measured fluxes and vertical profiles of biogenic volatile organic compounds (BVOCs) suggests that the inflow of anthropogenic precursors/aerosols likely enhanced the formation of both isoprene- and α-pinene-SOA within the forest canopy even when the BVOC flux was relatively low. This study highlights

  9. Quantification of furandiones in ambient aerosol

    NASA Astrophysics Data System (ADS)

    Al-Naiema, Ibrahim M.; Roppo, Hannah M.; Stone, Elizabeth A.

    2017-03-01

    Furandiones are products of the photooxidation of anthropogenic volatile organic compounds (VOC), like toluene, and contribute to secondary organic aerosol (SOA). Because few molecular tracers of anthropogenic SOA are used to assess this source in ambient aerosol, developing a quantification method for furandiones holds a great importance. In this study, we developed a direct and highly sensitive gas chromatography-mass spectrometry method for the quantitative analysis of furandiones in fine particulate matter that is mainly free from interference by structurally-related dicarboxylic acids. Our application of this method in Iowa City, IA provides the first ambient measurements of four furandiones: 2,5-furandione, 3-methyl-2,5-furandione, dihydro-2,5-furandione, and dihydro-3-methyl-2,5-furandione. Furandiones were detected in all collected samples with a daily average concentration of 9.1 ± 3.8 ng m-3. The developed method allows for the accurate measurement of the furandiones concentrations in ambient aerosol, which will support future evaluation of these compounds as tracers for anthropogenic SOA and assessment of their potential health impacts.

  10. Secondary Organic Aerosol Formation from the Photooxidation of Naphthalene

    NASA Astrophysics Data System (ADS)

    Zhou, S.; Chen, Y.; Wenger, J.

    2009-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants that are released into the atmosphere as a by-product of combustion processes. The gas-phase PAHs can be chemically transformed via reaction with the hydroxyl radical to produce a range of oxidised organic compounds and other pollutants such as ozone and secondary organic aerosol (SOA). Epidemiological studies have established that exposure to this type of air pollution is associated with damaging effects on the respiratory and cardiovascular systems, and can lead to asthma, oxidative stress, health deterioration and even death. The major anthropogenic source of SOA in urban areas is believed to be aromatic hydrocarbons, which are present in automobile fuels and are used as solvents. As a result, research is currently being performed on the characterisation of SOA produced from aromatic hydrocarbons such as toluene, the xylenes and trimethylbenzenes. However, significant amounts of PAHs are also released into urban areas from automobile emissions and the combustion of fossil fuels for home heating. Naphthalene is regularly cited as the most abundant PAH in polluted urban air, with typical ambient air concentrations of 0.05 - 0.20 parts per billion (ppbV) in European cities, comparable to the xylenes. Since naphthalene reacts in an analogous manner to monocyclic aromatic compounds then it is also expected to make a significant contribution to ambient SOA. However, the yield and chemical composition of SOA produced from the atmospheric degradation of naphthalene is not well known. In this presentation, the effects of NOx level and relative humidity on the SOA formation from the phootooixdation of naphthalene will be presented. A series of experiments has been performed in a large atmospheric simulation chamber equipped with a gas chromatograph and analyzers for monitoring nitrogen oxides (NOx) and ozone. SOA formation from the photooxidation of naphthalene was measured using a scanning mobility

  11. Local and distant source contributions to secondary organic aerosol in the Beijing urban area in summer

    NASA Astrophysics Data System (ADS)

    Lin, Jian; An, Junling; Qu, Yu; Chen, Yong; Li, Ying; Tang, Yujia; Wang, Feng; Xiang, Weiling

    2016-01-01

    Quantification of local and distant source contributions to particulate matter is a key issue to improving air quality in large urban areas, but few studies have focused on secondary organic aerosol (SOA) source contributions in a large area, especially in China. In this study, we extended the Comprehensive Air Quality Model with Extensions (CAMX) version 5.4, replacing the two-product approach by the volatility basis-set (VBS) approach, with updated SOA yields based on smog chamber studies. The modules related to the computationally efficient particulate source apportionment technology (PSAT) used in CAMX v5.4 were extended based on the volatility basis set (VBS) approach. The updated version of the CAMX model was then used to calculate the local and distant source contributions to SOA in Beijing for the first time. The results indicated that the VBS approach substantially improved hourly, daily, and monthly SOA simulations, compared with the two-product approach and the observations. In August 2007, the local source contributions to anthropogenic and biogenic SOA in Beijing were 23.8% and 16.6%, respectively; distant sources dominated for both anthropogenic and biogenic SOA in Beijing: Northern Hebei, Middle Hebei, Northeast China, Inner Mongolia, Shandong, and Tianjin (including Xianghe) contributed 5.1%-18.2% to anthropogenic SOA in Beijing; whereas, Inner Mongolia, Northern Hebei, and Northeast China contributed 12.2%, 18.6%, and 10.1%, respectively, to biogenic SOA in Beijing. Additionally, other areas outside China respectively contributed 5.3% and 10.8% to anthropogenic and biogenic SOA in Beijing: this could be related to strong summer monsoon.

  12. SOA formation potential of emissions from soil and leaf litter.

    PubMed

    Faiola, Celia L; Vanderschelden, Graham S; Wen, Miao; Elloy, Farah C; Cobos, Douglas R; Watts, Richard J; Jobson, B Thomas; Vanreken, Timothy M

    2014-01-21

    Soil and leaf litter are significant global sources of small oxidized volatile organic compounds, VOCs (e.g., methanol and acetaldehyde). They may also be significant sources of larger VOCs that could act as precursors to secondary organic aerosol (SOA) formation. To investigate this, soil and leaf litter samples were collected from the University of Idaho Experimental Forest and transported to the laboratory. There, the VOC emissions were characterized and used to drive SOA formation via dark, ozone-initiated reactions. Monoterpenes dominated the emission profile with emission rates as high as 228 μg-C m(-2) h(-1). The composition of the SOA produced was similar to biogenic SOA formed from oxidation of ponderosa pine emissions and α-pinene. Measured soil and litter monoterpene emission rates were compared with modeled canopy emissions. Results suggest surface soil and litter monoterpene emissions could range from 12 to 136% of canopy emissions in spring and fall. Thus, emissions from leaf litter may potentially extend the biogenic emissions season, contributing to significant organic aerosol formation in the spring and fall when reduced solar radiation and temperatures reduce emissions from living vegetation.

  13. Toward a Coherent Detailed Evaluation of Aerosol Data Products from Multiple Satellite Sensors

    NASA Technical Reports Server (NTRS)

    Ichoku, Charles; Petrenko, Maksym; Leptoukh, Gregory

    2011-01-01

    Atmospheric aerosols represent one of the greatest uncertainties in climate research. Although satellite-based aerosol retrieval has practically become routine, especially during the last decade, there is often disagreement between similar aerosol parameters retrieved from different sensors, leaving users confused as to which sensors to trust for answering important science questions about the distribution, properties, and impacts of aerosols. As long as there is no consensus and the inconsistencies are not well characterized and understood, there will be no way of developing reliable climate data records from satellite aerosol measurements. Fortunately, the most globally representative well-calibrated ground-based aerosol measurements corresponding to the satellite-retrieved products are available from the Aerosol Robotic Network (AERONET). To adequately utilize the advantages offered by this vital resource, an online Multi-sensor Aerosol Products Sampling System (MAPSS) was recently developed. The aim of MAPSS is to facilitate detailed comparative analysis of satellite aerosol measurements from different sensors (Terra-MODIS, Aqua-MODIS, TerraMISR, Aura-OMI, Parasol-POLDER, and Calipso-CALIOP) based on the collocation of these data products over AERONET stations. In this presentation, we will describe the strategy of the MASS system, its potential advantages for the aerosol community, and the preliminary results of an integrated comparative uncertainly analysis of aerosol products from multiple satellite sensors.

  14. The Multi-Sensor Aerosol Products Sampling System (MAPSS) for Integrated Analysis of Satellite Retrieval Uncertainties

    NASA Technical Reports Server (NTRS)

    Ichoku, Charles; Petrenko, Maksym; Leptoukh, Gregory

    2010-01-01

    Among the known atmospheric constituents, aerosols represent the greatest uncertainty in climate research. Although satellite-based aerosol retrieval has practically become routine, especially during the last decade, there is often disagreement between similar aerosol parameters retrieved from different sensors, leaving users confused as to which sensors to trust for answering important science questions about the distribution, properties, and impacts of aerosols. As long as there is no consensus and the inconsistencies are not well characterized and understood ', there will be no way of developing reliable climate data records from satellite aerosol measurements. Fortunately, the most globally representative well-calibrated ground-based aerosol measurements corresponding to the satellite-retrieved products are available from the Aerosol Robotic Network (AERONET). To adequately utilize the advantages offered by this vital resource,., an online Multi-sensor Aerosol Products Sampling System (MAPSS) was recently developed. The aim of MAPSS is to facilitate detailed comparative analysis of satellite aerosol measurements from different sensors (Terra-MODIS, Aqua-MODIS, Terra-MISR, Aura-OMI, Parasol-POLDER, and Calipso-CALIOP) based on the collocation of these data products over AERONET stations. In this presentation, we will describe the strategy of the MAPSS system, its potential advantages for the aerosol community, and the preliminary results of an integrated comparative uncertainty analysis of aerosol products from multiple satellite sensors.

  15. Secondary organic aerosol formation exceeds primary particulate matter emissions for light-duty gasoline vehicles

    NASA Astrophysics Data System (ADS)

    Gordon, T. D.; Presto, A. A.; May, A. A.; Nguyen, N. T.; Lipsky, E. M.; Donahue, N. M.; Gutierrez, A.; Zhang, M.; Maddox, C.; Rieger, P.; Chattopadhyay, S.; Maldonado, H.; Maricq, M. M.; Robinson, A. L.

    2013-09-01

    The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter after three hours of oxidation inside the chamber at typical atmospheric oxidant levels. Therefore, the contribution of light duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3-7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photo-oxidizing exhaust from newer (LEV1 and LEV2) vehicles was only modestly lower (38%) than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions in non-methane organic gas emissions. These data suggest that a complex and non-linear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the time scale of these experiments, the mixture of organic vapors emitted by newer vehicles appear to be more efficient (higher yielding) in producing SOA than

  16. Seasonal variations of biogenic secondary organic aerosol tracers in Cape Hedo, Okinawa

    NASA Astrophysics Data System (ADS)

    Zhu, Chunmao; Kawamura, Kimitaka; Fu, Pingqing

    2016-04-01

    Secondary organic aerosol (SOA) substantially contributes to particulate organic matter affecting the regional and global air quality and the climate. Total suspended particle (TSP) samples were collected in October 2009 to February 2012 on a weekly basis at Cape Hedo, Okinawa, Japan in the western North Pacific Rim, an outflow region of Asian aerosols and precursors. The TSP samples were analyzed for SOA tracers derived from biogenic volatile organic compounds (BVOCs). Total isoprene-SOA tracers showed a maximum in summer (2.12 ± 2.02 ng m-3) and minimum in winter (1.16 ± 0.92 ng m-3). This seasonality is mainly controlled by isoprene emission from the local subtropical forest, followed by regional scale emission of isoprene from the surrounding seas and long-range transported air masses. Total monoterpene-SOA tracers peaked in March (3.38 ± 2.03 ng m-3) followed by October (2.95 ± 1.62 ng m-3). In contrast, sesquiterpene-SOA tracer, β-caryophyllinic acid, showed winter maximum (1.63 ± 1.18 ng m-3) and summer minimum (0.20 ± 0.46 ng m-3). The variations of the monoterpene- and sesquiterpene-SOA tracers are likely related to the continental outflow of oxidation products of BVOC. Using a tracer-based method, we estimated the total biogenic SOC of 0.25-157 ng m-3 (mean 35.8 ng m-3) that accounts for 0.01-9.8% (mean 2.7%) of aerosol organic carbon. Our study suggests that SOA formation in the western North Pacific Rim is involved with not only local but also regional emissions followed by long-range atmospheric transport.

  17. Limited effect of anthropogenic nitrogen oxides on Secondary Organic Aerosol formation

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Unger, N.; Hodzic, A.; Emmons, L.; Knote, C.; Tilmes, S.; Lamarque, J.-F.; Yu, P.

    2015-08-01

    Globally, secondary organic aerosol (SOA) is mostly formed from emissions of biogenic volatile organic compounds (VOCs) by vegetation, but can be modified by human activities as demonstrated in recent research. Specifically, nitrogen oxides (NOx = NO + NO2) have been shown to play a critical role in the chemical formation of low volatility compounds. We have updated the SOA scheme in the global NCAR Community Atmospheric Model version 4 with chemistry (CAM4-chem) by implementing a 4-product Volatility Basis Set (VBS) scheme, including NOx-dependent SOA yields and aging parameterizations. The predicted organic aerosol amounts capture both the magnitude and distribution of US surface annual mean measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network by 50 %, and the simulated vertical profiles are within a factor of two compared to Aerosol Mass Spectrometer (AMS) measurements from 13 aircraft-based field campaigns across different region and seasons. We then perform sensitivity experiments to examine how the SOA loading responds to a 50 % reduction in anthropogenic nitric oxide (NO) emissions in different regions. We find limited SOA reductions of 0.9 to 5.6, 6.4 to 12.0 and 0.9 to 2.8 % for global, the southeast US and the Amazon NOx perturbations, respectively. The fact that SOA formation is almost unaffected by changes in NOx can be largely attributed to buffering in chemical pathways (low- and high-NOx pathways, O3 versus NO3-initiated oxidation) and to offsetting tendencies in the biogenic versus anthropogenic SOA responses.

  18. Limited effect of anthropogenic nitrogen oxides on Secondary Organic Aerosol formation

    DOE PAGES

    Zheng, Y.; Unger, N.; Hodzic, A.; ...

    2015-08-28

    Globally, secondary organic aerosol (SOA) is mostly formed from emissions of biogenic volatile organic compounds (VOCs) by vegetation, but can be modified by human activities as demonstrated in recent research. Specifically, nitrogen oxides (NOx = NO + NO2) have been shown to play a critical role in the chemical formation of low volatility compounds. We have updated the SOA scheme in the global NCAR Community Atmospheric Model version 4 with chemistry (CAM4-chem) by implementing a 4-product Volatility Basis Set (VBS) scheme, including NOx-dependent SOA yields and aging parameterizations. The predicted organic aerosol amounts capture both the magnitude and distribution ofmore » US surface annual mean measurements from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network by 50 %, and the simulated vertical profiles are within a factor of two compared to Aerosol Mass Spectrometer (AMS) measurements from 13 aircraft-based field campaigns across different region and seasons. We then perform sensitivity experiments to examine how the SOA loading responds to a 50 % reduction in anthropogenic nitric oxide (NO) emissions in different regions. We find limited SOA reductions of 0.9 to 5.6, 6.4 to 12.0 and 0.9 to 2.8 % for global, the southeast US and the Amazon NOx perturbations, respectively. The fact that SOA formation is almost unaffected by changes in NOx can be largely attributed to buffering in chemical pathways (low- and high-NOx pathways, O3 versus NO3-initiated oxidation) and to offsetting tendencies in the biogenic versus anthropogenic SOA responses.« less

  19. Aerosol and gas re-distribution by shallow cumulus clouds: An investigation using airborne measurements

    NASA Astrophysics Data System (ADS)

    Wonaschuetz, Anna; Sorooshian, Armin; Ervens, Barbara; Chuang, Patrick Y.; Feingold, Graham; Murphy, Shane M.; de Gouw, Joost; Warneke, Carsten; Jonsson, Haflidi H.

    2012-09-01

    Aircraft measurements during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) are used to examine the influence of shallow cumulus clouds on vertical profiles of aerosol chemical composition, size distributions, and secondary aerosol precursor gases. The data show signatures of convective transport of particles, gases and moisture from near the surface to higher altitudes, and of aqueous-phase production of aerosol mass (sulfate and organics) in cloud droplets and aerosol water. In cloudy conditions, the average aerosol volume concentration at an altitude of 2850 m, above typical cloud top levels, was found to be 34% of that at 450 m; for clear conditions, the same ratio was 13%. Both organic and sulfate mass fractions were on average constant with altitude (around 50%); however, the ratio of oxalate to organic mass increased with altitude (from 1% at 450 m to almost 9% at 3450 m), indicative of the influence of in-cloud production on the vertical abundance and characteristics of secondary organic aerosol (SOA) mass. A new metric termed "residual cloud fraction" is introduced as a way of quantifying the "cloud processing history" of an air parcel. Results of a parcel model simulating aqueous phase production of sulfate and organics reproduce observed trends and point at a potentially important role of SOA production, especially oligomers, in deliquesced aerosols. The observations emphasize the importance of shallow cumulus clouds in altering the vertical distribution of aerosol properties that influence both their direct and indirect effect on climate.

  20. Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

    NASA Astrophysics Data System (ADS)

    Tang, X.; Price, D.; Praske, E.; Vu, D. N.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-06-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 < κ < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol, whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. The contributions of semivolatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems.

  1. Model Representation of Secondary Organic Aerosol in CMAQ v4.7

    EPA Science Inventory

    Numerous scientific upgrades to the representation of secondary organic aerosol (SOA) are incorporated into the Community Multiscale Air Quality (CMAQ) modeling system. Additions include several recently identified SOA precursors: benzene, isoprene, and sesquiterpenes; and pathwa...

  2. Impacts of oxidation aging on secondary organic aerosol formation, particle growth rate, cloud condensation nuclei abundance, and aerosol climate forcing

    NASA Astrophysics Data System (ADS)

    Yu, F.; Luo, G.

    2014-12-01

    Particle composition measurements indicate that organic aerosol (OA) makes up ~20-90% of submicron particulate mass and secondary OA (SOA) accounts for a large fraction (~ 72 ±21%) of these OA masses at many locations around the globe. The volatility changes of secondary organic gases (SOG) associated with oxidation aging as well as the contribution of highly oxidized low volatile SOG (LV-SOG) to the condensational growth of secondary particles have been found to be important in laboratory and field measurements but are poorly represented in global models. A novel scheme to extend the widely used two-product SOA formation model, by adding a third product arising from the oxidation aging (i.e., LV-SOG) and considering the dynamic transfer of mass from higher to lower volatile products, has been developed and implemented into a global chemical transport model (GEOS-Chem) and a community atmosphere model (CESM-CAM5). The scheme requires only minor changes to the existing two-product SOA formation model and is computationally efficient. With the oxidation rate constrained by laboratory measurements, we show that the new scheme predicts a much higher SOA mass concentrations, improving the agreement with aerosol mass spectrometer SOA measurements. The kinetic condensation of LV-SOG on ultrafine particles, simulated by a size-resolved (sectional) advanced particle microphysics (APM) model incorporated into in GEOS-Chem and CAM5, increases the particle growth rate substantially and improves the agreement of simulated cloud condensation nuclei (CCN) concentrations with observations. Based on GEOS-Chem-APM simulations, the new SOA formation scheme increases global mean low troposphere SOA mass concentration by ~130% and CCN abundance by ~ 15%, and optical depth of secondary particles and coated black carbon and primary organic carbon particles by ~10%. As a result, aerosol radiative cooling effect (direct + first indirect) is enhanced by -0.9 W/m2, with large spatial

  3. Effects of chemical aging on global secondary organic aerosol using the volatility basis set approach

    NASA Astrophysics Data System (ADS)

    Jo, D. S.; Park, R. J.; Kim, M. J.; Spracklen, D. V.

    2013-12-01

    A global 3-D chemical transport model (GEOS-Chem) is used with the volatility basis set (VBS) approach to examine the effects of chemical aging on global secondary organic aerosol (SOA) concentrations and budgets. We present full-year simulations and their comparisons with the global aerosol mass spectrometer (AMS) dataset, the Interagency Monitoring of Protected Visual Environments (IMPROVE) dataset from the United States, the European Monitoring and Evaluation Programme (EMEP) dataset from Europe, and water-soluble organic carbon observation data collected over East Asia. Using different chemical aging constants, we find that the model results with 4 × 10-11 cm3 molecule-1 s-1 are in better agreement with all observations relative to the model results with other aging constants, without aging, and with the two-product approach. The model simulations are improved when chemical aging is considered, especially for rural regions. However, the simulations still underestimate observed oxygenated organic aerosol (OOA) in urban areas. Two sensitivity simulations including semi-volatile primary organic aerosol (POA) were conducted. We find that including semi-volatile POA improves the model in terms of the hydrogen-like organic aerosol (HOA) to OOA ratio. However, the total OA concentrations are not improved. The total SOA production is considerably increased by 53%, from 26.0 to 39.9 Tg yr-1, after considering chemical aging, remaining lower than top-down estimates of SOA production. Direct radiative forcing (DRF) increases by -0.07 W m-2 due to the chemical aging of SOA, which is comparable to the mean DRF (-0.13 W m-2) of OA from the AeroCom multi-model study. This result indicates considerable global and, more importantly, regional climate implications. For example, the regional DRF change due to chemical aging of SOA in the eastern US is -0.29 W m-2, which is 4 times greater in magnitude than the global mean value.

  4. Production of satellite-derived aerosol climate data records: current status of the ESA Aerosol_cci project

    NASA Astrophysics Data System (ADS)

    de Leeuw, Gerrit; Holzer-Popp, Thomas; Pinnock, Simon

    2015-04-01

    and the Aerosol_cci team Within the ESA Climate Change Initiative (CCI) project Aerosol_cci (Phase 1: 2010 -2014; Phase 2: 2014-2017) intensive work has been conducted to improve algorithms for the retrieval of aerosol information from European sensors ATSR (3 algorithms), PARASOL, MERIS (3 algorithms), synergetic AATSR/SCIAMACHY, OMI and GOMOS. Whereas OMI and GOMOS were used to derive absorbing aerosol index and stratospheric extinction profiles, respectively, Aerosol Optical Depth (AOD) and Ångström coefficient were retrieved from the other sensors. The cooperation between the project partners, including both the retrieval teams and independent validation teams, has resulted in a strong improvement of most algorithms. In particular the AATSR retrieved AOD is qualitatively similar to that from MODIS, usually taken as the standard, MISR and SeaWiFS. This conclusion has been reached form several different ways of validation of the L2 and L3 products, using AERONET sun photometer data as the common ground-truth for the application of both 'traditional' statistical techniques and a 'scoring' technique using spatial and temporal correlations. Quantitatively, the limited AATSR swath width of 500km results in a smaller amount of data. Nevertheless, the assimilation of AATSR-retrieved AOD, together with MODIS data, contributes to improving the in the ECMWF climate model results. In addition to the multi-spectral AOD, and thus the Ångström Exponent, also a per-pixel uncertainty is provided and validated. By the end of Aerosol_cci Phase 1 the ATSR algorithms have been applied to both ATSR-2 and AATSR resulting in an AOD time series of 17 years. In phase 2 this work is continued with a focus on the further improvement of the ATSR algorithms as well as those for the other instruments and algorithms, mentioned above, which in phase 1 were considered less mature. The first efforts are on the further characterization of the uncertainties and on better understanding of the

  5. Development of a Carbon Number Polarity Grid SOA Model with the use of Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere

    NASA Astrophysics Data System (ADS)

    Chung, S. H.; Lee-Taylor, J.; Asher, W.; Hodzic, A.; Madronich, S.; Aumont, B.; Pankow, J. F.; Barsanti, K. C.

    2012-12-01

    A major weakness in current air quality and climate models is the ability to simulate secondary organic aerosol (SOA) levels and physiochemical properties accurately. A new approach to model SOA formation is the carbon number (nc) polarity grid (CNPG) framework. The CNPG framework makes use of a nc vs. polarity grid for representing relevant organic compounds and their time-dependent concentrations. The nc vs polarity grid is well suited for modeling SOA because nc together with some suitable measure of total molecular polarity provides the minimum yet sufficient formation for estimating the parameters required to calculate partitioning coefficients. Furthermore, CNPG allows consideration of the effects of variation in the activity coefficients of the partitioning compounds, variation in the mean molecular weight of the absorbing organic phase, water uptake, and the possibility of phase separation in the organic aerosol phase. In this work, we use the GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) chemistry mechanism to produce the chemical structures of SOA precursor oxidization products and their time-dependent concentrations. The SIMPOL group contribution method is used to calculate the enthalpy of vaporization ΔHvap for each product. The total molecular polarity is then calculated as ΔHvap,diff, the difference between each compound's ΔHvap and that of its carbon-number equivalent straight-chain hydrocarbon. The gas- and particle-phase concentrations of each compound are mapped onto the nc vs polarity grid as a function of time to evaluate the time evolution of SOA-relevant oxidation products and to help guide lumping strategies for reducing complexity. In addition to using ΔHvap,diff, use of other measures of polarity will also be explored. Initial SOA precursor studies include toluene (C7) + n-heptadecane (C17) and α-pinene, under atmospherically relevant conditions. Results will be discussed in the context of the

  6. Secondary organic aerosol formation initiated from reactions between ozone and surface-sorbed squalene

    NASA Astrophysics Data System (ADS)

    Wang, Chunyi; Waring, Michael S.

    2014-02-01

    Previous research has shown that ozone reactions on surface-sorbed D-limonene can promote gas phase secondary organic aerosol (SOA) formation indoors. In this work, we conducted 13 steady state chamber experiments to measure the SOA formation entirely initiated by ozone reactions with squalene sorbed to glass, at chamber ozone of 57-500 ppb for two relative humidity (RH) conditions of 21% and 51%, in the absence of seed particles. Squalene is a nonvolatile compound that is a component of human skin oil and prevalent on indoor surfaces and in settled dust due to desquamation. The size distributions, mass and number secondary emission rates (SER), aerosol mass fractions (AMF), and aerosol number fractions (ANF) of formed SOA were quantified. The surface AMF and ANF are defined as the change in SOA mass or number formed, respectively, per ozone mass consumed by ozone-squalene reactions. All experiments but one exhibited nucleation and mass formation. Mass formation was relatively small in magnitude and increased with ozone, most notably for the RH = 51% experiments. The surface AMF was a function of the chamber aerosol concentration, and a multi-product model was fit using the 'volatility basis set' framework. Number formation was relatively strong at low ozone and low RH conditions. Though we cannot extrapolate our results because experiments were conducted at high air exchange rates, we speculate that this process may enhance particle number more than mass concentrations indoors.

  7. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2013-05-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 μg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but the ratio of the ensemble spread to mean does not change significantly.

  8. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2012-12-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 μg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but the ratio of the ensemble spread to mean does not change significantly.

  9. Uncertainties in SOA simulations due to meteorological uncertainties in Mexico City during MILAGRO-2006 field campaign

    NASA Astrophysics Data System (ADS)

    Bei, N.; Li, G.; Molina, L. T.

    2012-07-01

    The purpose of the present study is to investigate the uncertainties in simulating secondary organic aerosol (SOA) in Mexico City metropolitan area (MCMA) due to meteorological initial uncertainties using the WRF-CHEM model through ensemble simulations. The simulated periods (24 and 29 March 2006) represent two typical meteorological episodes ("Convection-South" and "Convection-North", respectively) in the Mexico City basin during the MILAGRO-2006 field campaign. The organic aerosols are simulated using a non-traditional SOA model including the volatility basis-set modeling method and the contributions from glyoxal and methylglyoxal. Model results demonstrate that uncertainties in meteorological initial conditions have significant impacts on SOA simulations, including the peak time concentrations, the horizontal distributions, and the temporal variations. The ensemble spread of the simulated peak SOA at T0 can reach up to 4.0 µg m-3 during the daytime, which is around 35% of the ensemble mean. Both the basin wide wind speed and the convergence area affect the magnitude and the location of the simulated SOA concentrations inside the Mexico City basin. The wind speed, especially during the previous midnight and the following early morning, influences the magnitude of the peak SOA concentration through ventilation. The surface horizontal convergence zone generally determines the area with high SOA concentrations. The magnitude of the ensemble spreads may vary with different meteorological episodes but has same significance compared to the ensemble mean.

  10. Chemical Characterization of Secondary Organic Aerosol Formed from Atmospheric Aqueous-phase Reactions of Phenolic Compounds

    NASA Astrophysics Data System (ADS)

    Yu, L.; Smith, J.; Anastasio, C.; Zhang, Q.

    2012-12-01

    Phenolic compounds, which are released in significant amounts from biomass burning, may undergo fast aqueous-phase reactions to form secondary organic aerosol (SOA) in the atmosphere. Understanding the aqueous-phase reaction mechanisms of these compounds and the composition of their reaction products is thus important for constraining SOA sources and predicting organic aerosol properties in models. In this study, we investigate the aqueous-phase reactions of three phenols (phenol, guaiacol and syringol) with two oxidants - excited triplet states (3C*) of non-phenolic aromatic carbonyls and hydroxyl radical (OH). By employing four analytical methods including high-resolution aerosol mass spectrometry, total organic carbon analysis, ion chromatography, and liquid chromatography-mass spectrometry, we thoroughly characterize the chemical compositions of the low volatility reaction products of phenols and propose formation mechanisms based on this information. Our results indicate that phenolic SOA is highly oxygenated, with O/C ratios in the range of 0.83-1.03, and that the SOA of phenol is usually more oxidized than those of guaiacol and syringol. Among the three precursors, syringol generates the largest fraction of higher molecular weight (MW) products. For the same precursor, the SOA formed via reaction with 3C* is less oxidized than that formed via reaction with OH. In addition, oxidation by 3C* enhances the formation of higher MW species, including phenolic dimers, higher oligomers and hydroxylated products, compared to reactions initiated by OH, which appear to favor the formation of organic acids. However, our results indicate that the yields of small organic acids (e.g., formate, acetate, oxalate, and malate) are low for both reaction pathways, together accounting for less than 5% of total SOA mass.

  11. Atmospheric Oxidation of 1,3-Butadiene: Characterization of gas and aerosol reaction products and implication for PM2.5

    EPA Science Inventory

    Secondary organic aerosol (SOA) was generated by irradiating 1,3-butadiene (13BD) in the presence of H2O2 or NOx. Experiments were conducted in a smog chamber operated in either flow or batch mode. A filter/denuder sampling system was used for simultaneously collecting gas and pa...

  12. Formation of secondary aerosols from gasoline vehicle exhaust when mixing with SO2

    NASA Astrophysics Data System (ADS)

    Liu, T.; Wang, X.; Hu, Q.; Deng, W.; Zhang, Y.; Ding, X.; Fu, X.; Bernard, F.; Zhang, Z.; Lü, S.; He, Q.; Bi, X.; Chen, J.; Sun, Y.; Yu, J.; Peng, P.; Sheng, G.; Fu, J.

    2016-01-01

    Sulfur dioxide (SO2) can enhance the formation of secondary aerosols from biogenic volatile organic compounds (VOCs), but its influence on secondary aerosol formation from anthropogenic VOCs, particularly complex mixtures like vehicle exhaust, remains uncertain. Gasoline vehicle exhaust (GVE) and SO2, a typical pollutant from coal burning, are directly co-introduced into a smog chamber, in this study, to investigate the formation of secondary organic aerosols (SOA) and sulfate aerosols through photooxidation. New particle formation was enhanced, while substantial sulfate was formed through the oxidation of SO2 in the presence of high concentration of SO2. Homogenous oxidation by OH radicals contributed a negligible fraction to the conversion of SO2 to sulfate, and instead the oxidation by stabilized Criegee intermediates (sCIs), formed from alkenes in the exhaust reacting with ozone, dominated the conversion of SO2. After 5 h of photochemical aging, GVE's SOA production factor revealed an increase by 60-200 % in the presence of high concentration of SO2. The increase could principally be attributed to acid-catalyzed SOA formation as evidenced by the strong positive linear correlation (R2 = 0.97) between the SOA production factor and in situ particle acidity calculated by the AIM-II model. A high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) resolved OA's relatively lower oxygen-to-carbon (O : C) (0.44 ± 0.02) and higher hydrogen-to-carbon (H : C) (1.40 ± 0.03) molar ratios for the GVE / SO2 mixture, with a significantly lower estimated average carbon oxidation state (OSc) of -0.51 ± 0.06 than -0.19 ± 0.08 for GVE alone. The relative higher mass loading of OA in the experiments with SO2 might be a significant explanation for the lower SOA oxidation degree.

  13. Formation of secondary aerosols from gasoline vehicle exhausts when mixing with SO2

    NASA Astrophysics Data System (ADS)

    Liu, T.; Wang, X.; Hu, Q.; Deng, W.; Zhang, Y.; Ding, X.; Fu, X.; Bernard, F.; Zhang, Z.; Lü, S.; He, Q.; Bi, X.; Chen, J.; Sun, Y.; Yu, J.; Peng, P.; Sheng, G.; Fu, J.

    2015-09-01

    Sulfur dioxide (SO2) can enhance the formation of secondary aerosols from biogenic volatile organic compounds (VOCs), but its influence on secondary aerosol formation from anthropogenic VOCs, particularly complex mixtures like vehicle exhausts, is still poorly understood. Here we directly co-introduced gasoline vehicles exhausts (GVE) and SO2, a typical pollutant from coal burning, into a smog chamber to investigate the formation of secondary organic aerosols (SOA) and sulfate aerosols through photooxidation. In the presence of high concentration of SO2, new particle formation was enhanced while substantial sulfate was formed through the oxidation of SO2. The homogenous oxidation by OH radicals contributed a negligible fraction to the conversion of SO2 to sulfate, and instead the oxidation by stabilized Criegee intermediates (sCIs), formed from alkenes in the exhaust reacting with ozone, dominated the conversion of SO2. After 5 h of photochemical aging, GVE's SOA production factor revealed an increase by 60-200 % in the presence of high concentration of SO2. This increase could largely be attributed to acid-catalyzed SOA formation, which was evidenced by the strong positive linear correlation (R2 = 0.97) between the SOA production factor and in-situ particle acidity calculated by AIM-II model. A high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) resolved OA's relatively lower oxygen-to-carbon (O : C) and higher hydrogen-to-carbon (H : C) molar ratios for the GVE/SO2 mixture, with a much lower estimated average carbon oxidation state (OSc) of -0.51 ± 0.06 than that of -0.19 ± 0.08 for GVE alone. The relative higher mass loading of OA in the experiments with SO2 might be the major reason for the lower oxidation degree of SOA.

  14. Contributions of toluene and alpha-pinene to SOA formed in an irradiated toluene/alpha-pinene/NO(x)/ air mixture: comparison of results using 14C content and SOA organic tracer methods.

    PubMed

    Offenberg, John H; Lewis, Charles W; Lewandowski, Michael; Jaoui, Mohammed; Kleindienst, Tadeusz E; Edney, Edward O

    2007-06-01

    An organic tracer method, recently proposed for estimating individual contributions of toluene and alpha-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, alpha-pinene, was irradiated in air in the presence of NO(x) to form SOA. The contributions of toluene and alpha-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct 14C content method. In the study, SOA to SOC ratios of 2.07 +/- 0.08 and 1.41 +/- 0.04 were measured for toluene and (alpha-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 microg m(-3) for toluene and 198 microg m(-)3 for alpha-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the 14C values of 182 and 230 microg m(-3) measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor.

  15. Resolution and Content Improvements to MISR Aerosol and Land Surface Products

    NASA Astrophysics Data System (ADS)

    Garay, M. J.; Bull, M. A.; Diner, D. J.; Hansen, E. G.; Kalashnikova, O. V.

    2015-12-01

    Since early 2000, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite has been providing operational Level 2 (swath-based) aerosol optical depth (AOD) and particle property retrievals at 17.6 km spatial resolution and atmospherically corrected land surface products at 1.1 km resolution. The performance of the aerosol product has been validated against ground-based Aerosol Robotic Network (AERONET) observations, model comparisons, and climatological assessments. This product has played a major role in studies of the impacts of aerosols on climate and air quality. The surface product has found a variety of uses, particularly at regional scales for assessing vegetation and land surface change. A major development effort has led to the release of an update to the operational (Version 22) MISR Level 2 aerosol and land surface retrieval products, which has been in production since December 2007. The new release is designated Version 23. The resolution of the aerosol product has been increased to 4.4 km, allowing more detailed characterization of aerosol spatial variability, especially near local sources and in urban areas. The product content has been simplified and updated to include more robust measures of retrieval uncertainty and other fields to benefit users. The land surface product has also been updated to incorporate the Version 23 aerosol product as input and to improve spatial coverage, particularly over mountainous terrain and snow/ice-covered surfaces. We will describe the major upgrades incorporated in Version 23 and present validation of the aerosol product against both the standard AERONET historical database, as well as high spatial density AERONET-DRAGON deployments. Comparisons will also be shown relative to the Version 22 aerosol and land surface products. Applications enabled by these product updates will be discussed.

  16. Formation of Secondary Organic Aerosol from Non-traditional Intermediate Volatility Organic Compounds

    NASA Astrophysics Data System (ADS)

    Donahue, N. M.; Presto, A. A.; Robinson, A. L.; Kroll, J. H.; Worsnop, D. R.

    2009-04-01

    Secondary organic aerosol (SOA) formation from 'traditional' precursors such as monoterpenes and alkylbenzenes has received substantial attention for the past decade. These traditional sources have relatively high emissions into the atmosphere, but they are also relatively volatile. As a consequence, the oxidation products from those precursors must be more than one million times less volatile in order to form SOA. We have recently begun to investigate the role of 'nontraditional' SOA precursors with much lower volatility than the traditional precursors. These intermediate volatility organic compounds (IVOC) are typically co-emitted with traditional primary organic aerosol (POA) sources at elevated temperatures, including biomass burning and internal combustion processes. While their emissions are much lower than the traditional precursors, the volatility reduction required of the reaction products is much less drastic, making high-yield SOA formation much more likely. Here we describe the formation of SOA from two precursors in the CMU environmental chamber - heptadecane and pentacosane - under high- and low-NOx conditions. Analysis of the resulting SOA with a high-resolution aerosol mass spectrometer coupled to a thermodenuder allows us to asses the oxidation state and volatility distribution of the condensible products, revealing a high degree of oxidation under high-NOx conditions where most of the organics remain in the vapor phase for at least 2 generations of oxidation chemistry, but a lower (though progressive) degree of oxidation under other conditions. These results will be place in context using a two-dimensional volatility basis set that incorporates both the volatility distribution and oxidation state of complex organic mixtures.

  17. Two MODIS Aerosol Products Over Ocean on the Terra and Aqua CERES SSF Datasets

    NASA Technical Reports Server (NTRS)

    Ignatov, Alexander; Minnis, Patrick; Loeb, Norman; Wielicki, Bruce; Miller, Walter; Sun-Mack, Sunny; Tanre, Didier; Remer, Lorraine; Laszlo, Istvan; Geier, Erika

    2004-01-01

    Over ocean, two aerosol products are reported on the Terra and Aqua CERES SSFs. Both are derived from MODIS, but using different sampling and aerosol algorithms. This study briefly summarizes these products, and compares using 2 weeks of global Terra data from 15-21 December 2000, and 1-7 June 2001.

  18. Appearance of strong absorbers and fluorophores in limonene-O3 secondary organic aerosol due to NH4+-mediated chemical aging over long time scales

    NASA Astrophysics Data System (ADS)

    Bones, David L.; Henricksen, Dana K.; Mang, Stephen A.; Gonsior, Michael; Bateman, Adam P.; Nguyen, Tran B.; Cooper, William J.; Nizkorodov, Sergey A.

    2010-03-01

    This study investigated long-term chemical aging of model biogenic secondary organic aerosol (SOA) prepared from the ozonolysis of terpenes. Techniques including electrospray ionization mass spectrometry (ESI-MS), UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, NMR, and three-dimensional fluorescence were used to probe the changes in chemical composition of SOA collected by impaction on substrates and also of aqueous extracts of SOA. The addition of ammonium ions or amino acids to limonene SOA reproducibly produced orange-colored species that strongly absorbed visible radiation and fluoresced at UV and visible wavelengths. Simultaneous addition of H2SO4 to the SOA aqueous extracts inhibited this color transformation. These observations suggest the existence of aging processes leading to heavily conjugated molecules containing organic nitrogen. The presence of nitrogen in the chromophores was confirmed by the dependence of the absorption and fluorescence spectra on the amino acids added. In contrast to the strong change in the absorption and fluorescence spectra, there was no significant change in the ESI-MS, FTIR, and NMR spectra, suggesting that the chromophores were minor species in the aged SOA. Aqueous extracts of aged limonene + NH4+ SOA were characterized by an effective base-e absorption coefficient of ˜3 L g-1 cm-1 at 500 nm. Assuming particulate matter concentrations typical of polluted rural air gives an upper limit of 0.2 M m-1 for the aerosol absorption coefficient due to the aged limonene oxidation products. Biogenic SOA can therefore become weakly absorbing if they undergo aging in the presence of NH4+-containing aerosol.

  19. Tracking Changes in Absorptivity, Stiffness, and Organic Chemical Composition in Laboratory Generated HULIS SOA using Atomic Force Microscopy and X-ray Microscopy

    NASA Astrophysics Data System (ADS)

    Hawkins, L. N.; Lemire, A.; Kong, W.

    2014-12-01

    Light absorbing organic compounds are among the many products of aqueous phase secondary organic aerosol formation. Once formed, these compounds can alter the optical and material properties of SOA in ways that impact their ability to scatter and absorb solar radiation, deliquesce and evaporate quickly during cloud cycling, and react with gas phase species such as oxidants. To quantify these effects, we have characterized the changes in UV-visible absorption, stiffness, and particle shape that occur when aqueous SOA is exposed to repeated wet-dry cycles and photooxidation. Material properties were measured with Atomic Force Microscopy of atomized laboratory generated SOA; this material was created by combining glyoxal, methylglyoxal, or glycolaldehyde with ammonium sulfate, glycine, or methylamine in solution and either spray drying or evaporating the bulk solution. In addition to optical and material properties, changes in organic functional groups were tracked using scanning transmission x-ray microscopy (STXM) of the near carbon edge x-ray absorption fine structure (NEXAFS). Photooxidation experiments of the same aqueous SOA revealed concomitant changes in the organic functional groups and light absorption spectra, along with measurable changes in particle stiffness.

  20. Assessment of 10-Year Global Record of Aerosol Products from the OMI Near-UV Algorithm

    NASA Astrophysics Data System (ADS)

    Ahn, C.; Torres, O.; Jethva, H. T.

    2014-12-01

    Global observations of aerosol properties from space are critical for understanding climate change and air quality applications. The Ozone Monitoring Instrument (OMI) onboard the EOS-Aura satellite provides information on aerosol optical properties by making use of the large sensitivity to aerosol absorption and dark surface albedo in the UV spectral region. These unique features enable us to retrieve both aerosol extinction optical depth (AOD) and single scattering albedo (SSA) successfully from radiance measurements at 354 and 388 nm by the OMI near UV aerosol algorithm (OMAERUV). Recent improvements to algorithms in conjunction with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Atmospheric Infrared Sounder (AIRS) carbon monoxide data also reduce uncertainties due to aerosol layer heights and types significantly in retrieved products. We present validation results of OMI AOD against space and time collocated Aerosol Robotic Network (AERONET) measured AOD values over multiple stations representing major aerosol episodes and regimes. We also compare the OMI SSA against the inversion made by AERONET as well as an independent network of ground-based radiometer called SKYNET in Japan, China, South-East Asia, India, and Europe. The outcome of the evaluation analysis indicates that in spite of the "row anomaly" problem, affecting the sensor since mid-2007, the long-term aerosol record shows remarkable sensor stability. The OMAERUV 10-year global aerosol record is publicly available at the NASA data service center web site (http://disc.sci.gsfc.nasa.gov/Aura/data-holdings/OMI/omaeruv_v003.shtml).

  1. SOA formation from the atmospheric oxidation of 2-methyl-3-buten-2-ol and its implications for PM2.5

    NASA Astrophysics Data System (ADS)

    Jaoui, M.; Kleindienst, T. E.; Offenberg, J. H.; Lewandowski, M.; Lonneman, W. A.

    2012-02-01

    The formation of secondary organic aerosol (SOA) generated by irradiating 2-methyl-3-buten-2-ol (MBO) in the presence and/or absence of NOx, H2O2, and/or SO2 was examined. Experiments were conducted in smog chambers operated in either dynamic or static mode. A filter/denuder sampling system was used for simultaneously collecting gas- and particle-phase products. The structural characterization of gas and particulate products was investigated using BSTFA, BSTFA + PFBHA, and DNPH derivatization techniques followed by GC-MS and liquid chromatography analysis. This analysis showed the occurrence of more than 68 oxygenated organic compounds in the gas and particle phases, 28 of which were tentatively identified. The major components observed include 2,3-dihydroxyisopentanol (DHIP), 2-hydroxy-2-oxoisopentanol, 2,3-dihydroxy-3-methylbutanal, 2,3-dihydroxy-2-methylsuccinic acid, 2-hydroxy-2-methylpropanedioic acid, acetone, glyoxal, methylglyoxal, glycolaldehyde, and formaldehyde. Most of these oxygenated compounds were detected for the first time in this study. While measurements of the gas-phase photooxidation products have been made, the focus of this work has been an examination of the particle phase. SOA from some experiments was analyzed for the organic mass to organic carbon ratio (OM/OC), the effective enthalpy of vaporization (ΔHvapeff), and the aerosol yield. Additionally, aerosol size, volume, and number concentrations were measured by a Scanning Mobility Particle Sizer coupled to a Condensation Particle Counter system. The OM/OC ratio was 2.1 in the MBO/H2O2 system. The ΔHvapeff was 41 kJ mol-1, a value similar to that of isoprene SOA. The laboratory SOA yield measured in this study was 0.7% in MBO/H2O2 for an aerosol mass of 33 μg m-3. Secondary organic aerosol was found to be negligible under conditions with oxides of nitrogen (NOx) present. Time profiles and proposed reaction schemes are provided for selected compounds. The contribution of SOA products

  2. How important are glassy SOA ice nuclei for the formation of cirrus clouds?

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Penner, J. E.; Lin, G.; Liu, X.; Wang, M.

    2014-12-01

    Extremely low ice numbers (i.e. 5 - 100 / L) have been observed in the tropical troposphere layer (TTL) in a variety of field campaigns. Various mechanisms have been proposed to explain these low numbers, including the effect of glassy secondary organic aerosol acting as heterogeneous ice nuclei (IN). In this study, we explored these effects using the CAM5.3 model. SOA fields were provided by an offline version of the University of Michigan-IMPACT model, which has a detailed process-based mechanism that describes aerosol microphysics and SOA formation through both gas phase and multiphase reactions. The transition criterion of SOA to glassy heterogeneous IN follows the parameterization developed by Wang et al. 2012. With this parameterization, glassy SOA IN form mainly when the temperature (T) is lower than 210K. In the default CAM5.3 set-up in which only the fraction of Aitken mode sulfate aerosols with diameter larger than 100nm participate in the ice nucleation (Liu and Penner 2005 parameterization), glassy SOA IN are shown to decrease the ice number (Ni) by suppressing some of the homogeneous freezing at low temperatures thereby leading to an improved representation of the relationship between Ni and T compared to the observations summarized by Kramer et al. 2009. However, when we allow the total number of the Aitken mode sulfate particles to participate in homogeneous freezing, glassy SOA IN have only a small impact on the relationship between Ni and T. If the subgrid updraft velocity is decreased to 0.1 m/s (compared to 0.2 m/s in the default set-up), there is a large decrease of Ni, since homogeneous freezing is more easily suppressed by glassy SOA IN at these updrafts. We also present the effects of glassy SOA IN using an alternative ice nucleation scheme (Barahona and Nenes, 2009).

  3. Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles.

    PubMed

    Russell, Lynn M; Bahadur, Ranjit; Ziemann, Paul J

    2011-03-01

    Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third of organic mass (OM), and some of which is secondary organic aerosol (SOA) from gas-phase precursors. The majority of the OM consists of alkane, carboxylic acid, hydroxyl, and carbonyl groups. The organic functional groups formed from combustion and vegetation emissions are similar to the secondary products identified in chamber studies. The near absence of carbonyl groups in the observed SOA associated with combustion is consistent with alkane rather than aromatic precursors, and the absence of organonitrate groups can be explained by their hydrolysis in humid ambient conditions. The remote forest observations have ratios of carboxylic acid, organic hydroxyl, and nonacid carbonyl groups similar to those observed for isoprene and monoterpene chamber studies, but in biogenic aerosols transported downwind of urban areas the formation of esters replaces the acid and hydroxyl groups and leaves only nonacid carbonyl groups. The carbonyl groups in SOA associated with vegetation emissions provides striking evidence for the mechanism of esterification as the pathway for possible oligomerization reactions in the atmosphere. Forest fires include biogenic emissions that produce SOA with organic components similar to isoprene and monoterpene chamber studies, also resulting in nonacid carbonyl groups in SOA.

  4. Modelling the formation and composition of secondary organic aerosol from α- and β-pinene ozonolysis using MCM v3

    NASA Astrophysics Data System (ADS)

    Jenkin, M. E.

    2004-05-01

    The formation and detailed composition of secondary organic aerosol (SOA) from the gas phase ozonolysis of α- and β-pinene has been simulated using the Master Chemical Mechanism version 3 (MCM v3), coupled with a representation of gas-to-aerosol transfer of semivolatile and involatile oxygenated products. A kinetics representation, based on equilibrium absorptive partitioning of ca. 200 semivolatile products, was found to provide an acceptable description of the final mass concentrations observed in a number of reported laboratory and chamber experiments, provided partitioning coefficients were increased by about two orders of magnitude over those defined on the basis of estimated vapour pressures. This adjustment is believed to be due, at least partially, to the effect of condensed phase association reactions of the partitioning products. Even with this adjustment, the simulated initial formation of SOA was delayed relative to that observed, implying the requirement for the formation of species of much lower volatility to initiate SOA formation. The inclusion of a simplified representation of the formation and gas-to-aerosol transfer of involatile dimers of 22 bi- and multifunctional carboxylic acids (in addition to the absorptive partitioning mechanism) allowed a much improved description of SOA formation for a wide range of conditions. The simulated SOA composition recreates certain features of the product distributions observed in a number of experimental studies, but implies an important role for multifunctional products containing hydroperoxy groups (i.e. hydroperoxides). This is particularly the case for experiments in which 2-butanol is used to scavenge OH radicals, because [HO2]/[RO2] ratios are elevated in such systems. The optimized mechanism is used to calculate SOA yields from α- and β-pinene ozonolysis in the presence and absence of OH scavengers, and as a function of temperature.

  5. Modelling the formation and composition of secondary organic aerosol from α- and β-pinene ozonolysis using MCM v3

    NASA Astrophysics Data System (ADS)

    Jenkin, M. E.

    2004-09-01

    The formation and detailed composition of secondary organic aerosol (SOA) from the gas phase ozonolysis of α- and β-pinene has been simulated using the Master Chemical Mechanism version 3 (MCM v3), coupled with a representation of gas-to-aerosol transfer of semivolatile and involatile oxygenated products. A kinetics representation, based on equilibrium absorptive partitioning of ca. 200 semivolatile products, was found to provide an acceptable description of the final mass concentrations observed in a number of reported laboratory and chamber experiments, provided partitioning coefficients were increased by about two orders of magnitude over those defined on the basis of estimated vapour pressures. This adjustment is believed to be due, at least partially, to the effect of condensed phase association reactions of the partitioning products. Even with this adjustment, the simulated initial formation of SOA was delayed relative to that observed, implying the requirement for the formation of species of much lower volatility to initiate SOA formation. The inclusion of a simplified representation of the formation and gas-to-aerosol transfer of involatile dimers of 22 bi- and multifunctional carboxylic acids (in addition to the absorptive partitioning mechanism) allowed a much improved description of SOA formation for a wide range of conditions. The simulated SOA composition recreates certain features of the product distributions observed in a number of experimental studies, but implies an important role for multifunctional products containing hydroperoxy groups (i.e. hydroperoxides). This is particularly the case for experiments in which 2-butanol is used to scavenge OH radicals, because [HO2]/[RO2] ratios are elevated in such systems. The optimized mechanism is used to calculate SOA yields from α- and β-pinene ozonolysis in the presence and absence of OH scavengers, and as a function of temperature.

  6. Influence of anthropogenic aerosol deposition on the relationship between oceanic productivity and warming

    NASA Astrophysics Data System (ADS)

    Wang, Rong; Balkanski, Yves; Bopp, Laurent; Aumont, Olivier; Boucher, Olivier; Ciais, Philippe; Gehlen, Marion; Peñuelas, Josep; Ethé, Christian; Hauglustaine, Didier; Li, Bengang; Liu, Junfeng; Zhou, Feng; Tao, Shu

    2015-12-01

    Satellite data and models suggest that oceanic productivity is reduced in response to less nutrient supply under warming. In contrast, anthropogenic aerosols provide nutrients and exert a fertilizing effect, but its contribution to evolution of oceanic productivity is unknown. We simulate the response of oceanic biogeochemistry to anthropogenic aerosols deposition under varying climate from 1850 to 2010. We find a positive response of observed chlorophyll to deposition of anthropogenic aerosols. Our results suggest that anthropogenic aerosols reduce the sensitivity of oceanic productivity to warming from -15.2 ± 1.8 to -13.3 ± 1.6 Pg C yr-1 °C-1 in global stratified oceans during 1948-2007. The reducing percentage over the North Atlantic, North Pacific, and Indian Oceans reaches 40, 24, and 25%, respectively. We hypothesize that inevitable reduction of aerosol emissions in response to higher air quality standards in the future might accelerate the decline of oceanic productivity per unit warming.

  7. Soot aggregate restructuring due to coatings of secondary organic aerosol derived from aromatic precursors.

    PubMed

    Schnitzler, Elijah G; Dutt, Ashneil; Charbonneau, André M; Olfert, Jason S; Jäger, Wolfgang

    2014-12-16

    Restructuring of monodisperse soot aggregates due to coatings of secondary organic aerosol (SOA) derived from hydroxyl radical-initiated oxidation of toluene, p-xylene, ethylbenzene, and benzene was investigated in a series of photo-oxidation (smog) chamber experiments. Soot aggregates were generated by combustion of ethylene using a McKenna burner, treated by denuding, size-selected by a differential mobility analyzer, and injected into a smog chamber, where they were exposed to low vapor pressure products of aromatic hydrocarbon oxidation, which formed SOA coatings. Aggregate restructuring began once a threshold coating mass was reached, and the degree of the subsequent restructuring increased with mass growth factor. Although significantly compacted, fully processed aggregates were not spherical, with a mass-mobility exponent of 2.78, so additional SOA was required to fill indentations between collapsed branches of the restructured aggregates before the dynamic shape factor of coated particles approached 1. Trends in diameter growth factor, effective density, and dynamic shape factor with increasing mass growth factor indicate distinct stages in soot aggregate processing by SOA coatings. The final degree and coating mass dependence of soot restructuring were found to be the same for SOA coatings from all four aromatic precursors, indicating that the surface tensions of the SOA coatings are similar.

  8. EFFECT OF ACIDITY ON SECONDARY ORGANIC AEROSOL FORMATION FROM ISOPRENE

    EPA Science Inventory

    The effect of particle-phase acidity on secondary organic aerosol (SOA) formation from isoprene is investigated in a laboratory chamber study, in which the acidity of the inorganic seed aerosol was controlled systematically. The observed enhancement in SOA mass concentration is c...

  9. Secondary organic aerosol formation of primary, secondary and tertiary Amines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Amines have been widely identified in ambient aerosol in both urban and rural environments and they are potential precursors for formation of nitrogen-containing secondary organic aerosols (SOA). However, the role of amines in SOA formation has not been well studied. In this wrok, we use UC-Riversid...

  10. Sources, Properties, Aging, and Anthropogenic Influences on OA and SOA over the Southeast US and the Amazon duing SOAS, DC3, SEAC4RS, and GoAmazon

    EPA Science Inventory

    The SE US and the Amazon have large sources of biogenic VOCs, varying anthropogenic pollution impacts, and often poor organic aerosol (OA) model performance. Recent results on the sources, properties, aging, and impact of anthropogenic pollution on OA and secondary OA (SOA) over ...

  11. A qualitative comparison of secondary organic aerosol yields and composition from ozonolysis of monoterpenes at varying concentrations of NO2

    NASA Astrophysics Data System (ADS)

    Draper, D. C.; Farmer, D. K.; Desyaterik, Y.; Fry, J. L.

    2015-11-01

    The effect of NO2 on secondary organic aerosol (SOA) formation from ozonolysis of α-pinene, β-pinene, Δ3-carene, and limonene was investigated using a dark flow-through reaction chamber. SOA mass yields were calculated for each monoterpene from ozonolysis with varying NO2 concentrations. Kinetics modeling of the first-generation gas-phase chemistry suggests that differences in observed aerosol yields for different NO2 concentrations are consistent with NO3 formation and subsequent competition between O3 and NO3 to oxidize each monoterpene. α-Pinene was the only monoterpene studied that showed a systematic decrease in both aerosol number concentration and mass concentration with increasing [NO2]. β-Pinene and Δ3-carene produced fewer particles at higher [NO2], but both retained moderate mass yields. Limonene exhibited both higher number concentrations and greater mass concentrations at higher [NO2]. SOA from each experiment was collected and analyzed by HPLC-ESI-MS, enabling comparisons between product distributions for each system. In general, the systems influenced by NO3 oxidation contained more high molecular weight products (MW > 400 amu), suggesting the importance of oligomerization mechanisms in NO3-initiated SOA formation. α-Pinene, which showed anomalously low aerosol mass yields in the presence of NO2, showed no increase in these oligomer peaks, suggesting that lack of oligomer formation is a likely cause of α-pinene's near 0 % yields with NO3. Through direct comparisons of mixed-oxidant systems, this work suggests that NO3 is likely to dominate nighttime oxidation pathways in most regions with both biogenic and anthropogenic influences. Therefore, accurately constraining SOA yields from NO3 oxidation, which vary substantially with the volatile organic compound precursor, is essential in predicting nighttime aerosol production.

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

    NASA Astrophysics Data System (ADS)

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; Day, Douglas A.; Kaser, Lisa; Jud, Werner; Karl, Thomas; Hansel, Armin; Hunter, James F.; Cross, Eben S.; Kroll, Jesse H.; Peng, Zhe; Brune, William H.; Jimenez, Jose L.

    2016-03-01

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen-Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed for semicontinuous 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 timescales 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 3 µg m-3 when LVOC fate corrected) compared to daytime (average 0.9 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 local time. 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 OFR254-70), 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

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

    DOE PAGES

    Palm, Brett B.; Campuzano-Jost, Pedro; Ortega, Amber M.; ...

    2016-03-08

    An oxidation flow reactor (OFR) is a vessel inside which the concentration of a chosen oxidant can be increased for the purpose of studying SOA formation and aging by that oxidant. During the BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen–Rocky Mountain Biogenic Aerosol Study) field campaign, ambient pine forest air was oxidized by OH radicals in an OFR to measure the amount of SOA that could be formed from the real mix of ambient SOA precursor gases, and how that amount changed with time as precursors changed. High OH concentrations and short residence times allowed formore » semicontinuous 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 timescales 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 3 µg m−3 when LVOC fate corrected) compared to daytime (average 0.9 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 local time. 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 OFR254-70), 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

  14. Uptake of Ambient Organic Gases to Acidic Sulfate Aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Li, S.

    2009-05-01

    The formation of secondary organic aerosols (SOA) in the atmosphere has been an area of significant interest due to its climatic relevance, its effects on air quality and human health. Due largely to the underestimation of SOA by regional and global models, there has been an increasing number of studies focusing on alternate pathways leading to SOA. In this regard, recent work has shown that heterogeneous and liquid phase reactions, often leading to oligomeric material, may be a route to SOA via products of biogenic and anthropogenic origin. Although oligomer formation in chamber studies has been frequently observed, the applicability of these experiments to ambient conditions, and thus the overall importance of oligomerization reactions remain unclear. In the present study, ambient air is drawn into a Teflon smog chamber and exposed to acidic sulfate aerosols which have been formed in situ via the reaction of SO3 with water vapor. The aerosol composition is measured with a High Resolution Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS), and particle size distributions are monitored with a scanning mobility particle sizer (SMPS). The use of ambient air and relatively low inorganic particle loading potentially provides clearer insight into the importance of heterogeneous reactions. Results of experiments, with a range of sulfate loadings show that there are several competing processes occurring on different timescales. A significant uptake of ambient organic gases to the particles is observed immediately followed by a slow shift towards higher m/z over a period of several hours indicating that higher molecular weight products (possibly oligomers) are being formed through a reactive process. The results suggest that heterogeneous reactions can occur with ambient organic gases, even in the presence of ammonia, which may have significant implications to the ambient atmosphere where particles may be neutralized after their formation.

  15. Photolytic processing of secondary organic aerosols dissolved in cloud droplets.

    PubMed

    Bateman, Adam P; Nizkorodov, Sergey A; Laskin, Julia; Laskin, Alexander

    2011-07-14

    The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ∼0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest