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Sample records for aged secondary organic

  1. Molecular transformations accompanying the aging of laboratory secondary organic aerosol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aging of fresh secondary organic aerosol, generated by alpha-pinene ozonolysis in a flow tube reactor, was studied by passing it through a second reaction chamber where hydroxyl radicals were generated. Two types of experiments were performed: plug injection experiments where the particle mass a...

  2. Photochemical aging of light-absorbing secondary organic aerosol material.

    PubMed

    Sareen, Neha; Moussa, Samar G; McNeill, V Faye

    2013-04-11

    Dark reactions of methylglyoxal with NH4(+) in aqueous aerosols yield light-absorbing and surface-active products that can influence the physical properties of the particles. Little is known about how the product mixture and its optical properties will change due to photolysis as well as oxidative aging by O3 and OH in the atmosphere. Here, we report the results of kinetics and product studies of the photochemical aging of aerosols formed by atomizing aqueous solutions of methylglyoxal and ammonium sulfate. Experiments were performed using aerosol flow tube reactors coupled with an aerosol chemical ionization mass spectrometer (Aerosol-CIMS) for monitoring gas- and particle-phase compositions. Particles were also impacted onto quartz windows in order to assess changes in their UV-visible absorption upon oxidation. Photooxidation of the aerosols leads to the formation of small, volatile organic acids including formic acid, acetic acid, and glyoxylic acid. The atmospheric lifetime of these species during the daytime is predicted to be on the order of minutes, with photolysis being an important mechanism of degradation. The lifetime with respect to O3 oxidation was observed to be on the order of hours. O3 oxidation also leads to a net increase in light absorption by the particles due to the formation of additional carbonyl compounds. Our results are consistent with field observations of high brown carbon absorption in the early morning. PMID:23506538

  3. Characterization of Highly Oxidized Molecules in Fresh and Aged Biogenic Secondary Organic Aerosol.

    PubMed

    Tu, Peijun; Hall, Wiley A; Johnston, Murray V

    2016-04-19

    In this work, highly oxidized multifunctional molecules (HOMs) in fresh and aged secondary organic aerosol (SOA) derived from biogenic precursors are characterized with high-resolution mass spectrometry. Fresh SOA was generated by mixing ozone with a biogenic precursor (β-pinene, limonene, α-pinene) in a flow tube reactor. Aging was performed by passing the fresh SOA through a photochemical reactor where it reacted with hydroxyl radicals. Although these aerosols were as a whole not highly oxidized, molecular analysis identified a significant number of HOMs embedded within it. HOMs in fresh SOA consisted mostly of monomers and dimers, which is consistent with condensation of extremely low-volatility organic compounds (ELVOCs) that have been detected in the gas phase in previous studies and linked to SOA particle formation. Aging caused an increase in the average number of carbon atoms per molecule of the HOMs, which is consistent with particle phase oxidation of (less oxidized) oligomers already existing in fresh SOA. HOMs having different combinations of oxygen-to-carbon ratio, hydrogen-to-carbon ratio and average carbon oxidation state are discussed and compared to low volatility oxygenated organic aerosol (LVOOA), which has been identified in ambient aerosol based on average elemental composition but not fully understood at a molecular level. For the biogenic precursors and experimental conditions studied, HOMs in fresh biogenic SOA have molecular formulas more closely resembling LVOOA than HOMs in aged SOA, suggesting that aging of biogenic SOA is not a good surrogate for ambient LVOOA. PMID:27000653

  4. Formation and aging of secondary organic aerosol from toluene: changes in chemical composition, volatility, and hygroscopicity

    DOE PAGESBeta

    Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K. M.; Nenes, A.; Donahue, N. M.; Pandis, S. N.

    2015-07-24

    Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OSc), and mass yield. The OA oxidation state generally increased duringmore » photo-oxidation, and the final OA OSc ranged from -0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.« less

  5. Effects of Chemical Aging on Global Secondary Organic Aerosol using the Volatility Basis Set Approach

    NASA Astrophysics Data System (ADS)

    Park, R.; Jo, D.; Kim, M.; Spracklen, D. V.; Hodzic, A.

    2014-12-01

    Organic aerosol (OA) constitutes significant mass fractions (20-90%) of total dry fine aerosols in the atmosphere. However, global models of OA have shown large discrepancies when compared to the observations because of the limited capability to simulate secondary OA (SOA). For reducing the discrepancies between observations and models, recent studies have shown that chemical aging reactions in the atmosphere are important because they can lead to decreases in organic volatility, resulting in increase of SOA mass yields. To efficiently simulate chemical aging of SOA in the atmosphere, we implemented the volatility basis set approach in a global 3-D chemical transport model (GEOS-Chem). We present full-year simulations and their comparisons with multiple observations - global aerosol mass spectrometer dataset, the Interagency Monitoring of Protected Visual Environments from the United States, the European Monitoring and Evaluation Programme dataset and water-soluble organic carbon observation data collected over East Asia. Using different input parameters in the model, we also explore the uncertainty of the SOA simulation for which we use an observational constraint to find the optimized values with which the model reduces the discrepancy from the observations. Finally, we estimate the effect of OA on climate using our best simulation results.

  6. Modeling the formation and aging of secondary organic aerosols during CalNex 2010

    NASA Astrophysics Data System (ADS)

    Hayes, P. L.; Ortega, A. M.; Ahmadov, R.; McKeen, S. A.; Washenfelder, R. A.; Alvarez, S.; Rappenglueck, B.; Holloway, J. S.; Gilman, J. B.; Kuster, W. C.; De Gouw, J. A.; Zotter, P.; Prevot, A. S.; Kleindienst, T. E.; Offenberg, J. H.; Jimenez, J. L.

    2012-12-01

    Several traditional and recently proposed models are applied to predict the concentrations and properties of secondary organic aerosols (SOA) and organic gases at the Pasadena ground site during the CalNex campaign. The models are constrained with and compared against results from available observations. The CalNex campaign and specifically the Pasadena ground site featured a large and sophisticated suite of aerosol and gas phase instrumentation, and thus, it provides a unique opportunity to test SOA models under conditions of strong urban emissions at a range of low photochemical ages. The oxidation of volatile organic compounds (VOCs) using an updated traditional model cannot explain the observed ambient SOA, and under-predicts the measurements by a factor of ~40. Similarly, after accounting for the multi-generation oxidation of VOCs using a volatility basis set (VBS) approach as described by Tsimpidi et al. (2010), SOA is still under-predicted by a factor of ~8. For SOA formed from VOCs (V-SOA) the dominant precursors are aromatics (xylenes, toluene, and trimethylbenzenes). The model SOA formed from the oxidation of primary semivolatile and intermediate volatility organic compounds (P-S/IVOCs, producing SI-SOA) is also predicted using the parameterizations of Robinson et al. (2007) and Grieshop et al. (2009), and the properties of V-SOA + SI-SOA are compared against the measured O:C and volatility. We also compare the results of the different models against fossil/non-fossil carbon measurements as well as tracers of different SOA precursors. Potential Aerosol Mass (PAM) measurements of the SOA forming potential of the Pasadena air masses are also compared against that predicted by the models. The PAM analysis allows for model/measurement comparisons of SOA properties over a range of photochemical ages spanning almost two weeks. Using the V-SOA model, at low photochemical ages (< 1 day) the modeled PAM V-SOA is less than the measured PAM SOA, similar to the

  7. 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

  8. Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

    SciTech Connect

    Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

    2013-05-10

    Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

  9. Secondary organic aerosols - formation and ageing studies in the SAPHIR chamber

    NASA Astrophysics Data System (ADS)

    Spindler, Christian; Müller, Lars; Trimborn, Achim; Mentel, Thomas; Hoffmann, Thorsten

    2010-05-01

    Secondary organic aerosol (SOA) formation from oxidation products of biogenic volatile organic compounds (BVOC) constitutes an important coupling between vegetation, atmospheric chemistry, and climate change. Such secondary organic aerosol components play an important role in particle formation in Boreal regions ((Laaksonen et al., 2008)), where biogenic secondary organic aerosols contribute to an overall negative radiative forcing, thus a negative feed back between vegetation and climate warming (Spracklen et al., 2008). Within the EUCAARI project we investigated SOA formation from mixtures of monoterpenes (and sesquiterpenes) as emitted typically from Boreal tree species in Southern Finland. The experiments were performed in the large photochemical reactor SAPHIR in Juelich at natural light and oxidant levels. Oxidation of the BVOC mixtures and SOA formation was induced by OH radicals and O3. The SOA was formed on the first day and then aged for another day. The resulting SOA was characterized by HR-ToF-AMS, APCI-MS, and filter samples with subsequent H-NMR, GC-MS and HPLC-MS analysis. The chemical evolution of the SOA is characterized by a fast increase of the O/C ratio during the formation process on the first day, stable O/C ratio during night, and a distinctive increase of O/C ratio at the second day. The increase of the O/C ratio on the second day is highly correlated to the OH dose and is accompanied by condensational growth of the particles. We will present simultaneous factor analysis of AMS times series (PMF, Ulbrich et al., 2009 ) and direct measurements of individual chemical species. We found that four factors were needed to represent the time evolution of the SOA composition (in the mass spectra) if oxidation by OH plays a mayor role. Corresponding to these factors we observed individual, representative molecules with very similar time behaviour. The correlation between tracers and AMS factors is astonishingly good as the molecular tracers

  10. Oxidative Aging and Secondary Organic Aerosol Formation from Simulated Wildfire Emissions

    NASA Astrophysics Data System (ADS)

    Hennigan, C. J.; Miracolo, M. A.; Engelhart, G. J.; May, A. A.; Wold, C. E.; Hao, W. M.; Lee, T.; Sullivan, A. P.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Collett, J. L.; Kreidenweis, S. M.; Robinson, A. L.

    2010-12-01

    Wildfires are a significant fraction of global biomass burning and a major source of trace gas and particle emissions in the atmosphere. Understanding the air quality and climate implications of wildfires is difficult since the emissions undergo complex transformations due to aging processes during transport away from the source. As part of the third Fire Lab at Missoula Experiment (FLAME III), we investigated the oxidative aging of smoke from combustion of 12 different types of vegetation commonly burned in North American wildfires. In these photochemical chamber experiments, we quantified the evolution of reactive trace gases and particles, with a focus on the chemistry contributing to changes in the organic aerosol (OA) concentration. Factors such as precursor VOC concentrations, oxidant exposure, and the role of NOx were considered. The results illustrate the complex and variable nature of biomass burning emissions, since none of these factors alone account for the wide range of OA enhancements that were observed. For example, in some experiments, a net decrease of up to 30% in the OA concentration was observed, while in others, the OA concentration increased by a factor of three over the course of aging due to secondary OA (SOA) production. Despite this variability, all experiments showed significant physical (e.g., changes in aerosol volatility) and chemical (e.g., changes in oxidation) transformations in the OA due to oxidation. Overall, the results demonstrate that traditional definitions of POA and SOA continue to blur in many systems, and that processes like partitioning and heterogeneous chemistry can have the most significant effect on the evolution of biomass burning aerosol.

  11. Evolution of the complex refractive index in the UV spectral region in ageing secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Flores, J. M.; Zhao, D. F.; Segev, L.; Schlag, P.; Kiendler-Scharr, A.; Fuchs, H.; Watne, Å. K.; Bluvshtein, N.; Mentel, Th. F.; Hallquist, M.; Rudich, Y.

    2014-06-01

    The chemical and physical properties of secondary organic aerosol (SOA) formed by the photochemical degradation of biogenic and anthropogenic volatile organic compounds (VOC) are as yet still poorly constrained. The evolution of the complex refractive index (RI) of SOA, formed from purely biogenic VOC and mixtures of biogenic and anthropogenic VOC, was studied over a diurnal cycle in the SAPHIR photochemical outdoor chamber in Jülich, Germany. The correlation of RI with SOA chemical and physical properties such as oxidation level and volatility was examined. The RI was retrieved by a newly developed broadband cavity-enhanced spectrometer for aerosol optical extinction measurements in the UV spectral region (360 to 420 nm). Chemical composition and volatility of the particles were monitored by a high-resolution time-of-flight aerosol mass spectrometer, and a volatility tandem differential mobility analyzer. SOA was formed by ozonolysis of either (i) a mixture of biogenic VOC (α-pinene and limonene), (ii) biogenic VOC mixture with subsequent addition of an anthropogenic VOC (p-xylene-d10), or (iii) a mixture of biogenic and anthropogenic VOC. The SOA aged by ozone/OH reactions up to 29.5 h was found to be non-absorbing in all cases. The SOA with p-xylene-d10 showed an increase of the scattering component of the RI correlated with an increase of the O / C ratio and with an increase in the SOA density. There was a greater increase in the scattering component of the RI when the SOA was produced from the mixture of biogenic VOCs and anthropogenic VOC than from the sequential addition of the VOCs after approximately the same ageing time. The increase of the scattering component was inversely correlated with the SOA volatility. Two RI retrievals determined for the pure biogenic SOA showed a constant RI for up to 5 h of ageing. Mass spectral characterization shows the three types of the SOA formed in this study have a significant amount of semivolatile components. The

  12. OH-Radical initiated ageing of biogenic secondary organic aerosols - A detailed chemical analysis

    NASA Astrophysics Data System (ADS)

    Müller, L.; Reinnig, M.-C.; Mentel, Th. F.; Tillmann, R.; Schlosser, E.; Wahner, A.; Saathoff, H.; Donahue, N. M.; Hoffmann, T.

    2009-04-01

    The chemical ageing[1] of secondary organic aerosol (SOA) was investigated in two series of experiments using on-line mass spectrometry and off-line high performance liquid chromatography mass spectrometry (HPLC-MS). In a set of photochemical experiments, performed in the large outdoor reaction chamber SAPHIR (Jülich, Germany), SOA was generated from a boreal mixture including mono- and sesquiterpenes (α-pinene, β-pinene, Δ3-carene, limonene, caryophyllene). During a long time experiment (30h) the generated SOA was exposed to OH-radicals and the chemical composition was analyzed on-line using atmospheric pressure ionization mass spectrometry (API-MS). The on-line method provides highly time resolved chemical information and therefore a direct insight into the temporal changes of SOA-composition. In parallel, filter samples analysed by HPLC-MS allow the enrichment of trace compounds and finally an unambiguous identification of individual substances. In addition, filter samples allow a direct comparison to samples from field studies. The ageing experiments showed a clear change in SOA composition. The compounds observed can be divided into two groups: A group of first generation SOA-compounds, generated by the OH oxidation of the terpenes and a group of second generation compounds, generated by the reaction of OH with SOA compounds. Among the second generation products, especially a tricarboxylic acid (3-methyl-1,2,3-butanetricarboxylic acid, m/z 203)[2] was observed to be a good marker compound for BSOA ageing. A further set of experiments was carried out in another large aerosol chamber facility, the AIDA chamber of the Research Centre Karlsruhe. In this dark chamber, the experiments focused on the OH-induced ageing of α-pinene SOA and the influence of temperature. The results clearly show that the tricarboxylic acid is a distinctive marker for OH radical induced BSOA ageing and identify cis-pinonic acid as its precursor. To connect the results of the

  13. Photochemical aging of secondary organic aerosols generated from the photooxidation of polycyclic aromatic hydrocarbons in the gas-phase.

    PubMed

    Riva, Matthieu; Robinson, Ellis S; Perraudin, Emilie; Donahue, Neil M; Villenave, Eric

    2015-05-01

    Aging processes of secondary organic aerosol (SOA) may be a source of oxygenated organic aerosols; however, the chemical processes involved remain unclear. In this study, we investigate photochemical aging of SOA produced by the gas-phase oxidation of naphthalene by hydroxyl radicals and acenaphthylene by ozone. We monitored the SOA composition using a high-resolution time-of-flight aerosol mass spectrometer. We initiated SOA aging with UV photolysis alone and with OH radicals in the presence or absence of light and at different NOx levels. For naphthalene, the organic composition of the particulate phase seems to be dominated by highly oxidized compounds such as carboxylic acids, and aging data may be consistent with diffusion limitations. For acenaphthylene, the fate of oxidized products and the moderately oxidized aerosol seem to indicate that functionalization reactions might be the main aging process were initiated by the cumulative effect of light and OH radicals. PMID:25856309

  14. Investigation of a Particle into Liquid Sampler to Study the Formation & Ageing of Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Pereira, K. L.; Hamilton, J. F.; Rickard, A. R.; Bloss, W. J.; Alam, M. S.; Camredon, M.; Munoz, A.; Vazquez, M.; Rodenas, M.; Vera, T.; Borrás, E.

    2012-12-01

    The atmospheric oxidation of Volatile Organic Compounds (VOCs) in the presence of NOx results in the formation of tropospheric ozone and Secondary Organic Aerosol (SOA) [Hallquist et al., 2009]. Whilst SOA is known to affect both climate and human health, the VOC oxidation pathways leading to SOA formation are poorly understood [Solomon et al., 2007]. This is in part due to the vast number and the low concentration of SOA species present in the ambient atmosphere. It has been estimated as many as 10,000 to 100,000 VOCs have been detected in the atmosphere, all of which can undergo photo-chemical oxidation and contribute to SOA formation [Goldstein and Galbally, 2007]. Atmospheric simulation chambers such as the EUropean PHOtoREactor (EUPHORE) in Valencia, Spain, are often used to study SOA formation from a single VOC precursor under controlled conditions. SOA composition and formation can be studied using online techniques such as Aerosol Mass Spectrometry (AMS), which provide high time resolution but limited structural information [Zhang et al., 2007]. Offline techniques, such as collection onto filters, extraction and subsequent analysis, provide detailed SOA composition but only usually one or two samples per experiment. In this work we report time resolved SOA composition analysis using a Particle into Liquid Sampler (PILS) followed by Liquid Chromatography Ion-Trap Mass Spectrometry (LC-IT-MS/MS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS/MS). Experiments were performed at EUPHORE investigating the formation and composition of Methyl Chavicol SOA. Methyl Chavicol (also known as Estragole) was identified as the highest floral emission from an oil palm plantation in Malaysian Borneo and has also been observed in US pine forests [Bouvier-Brown et al., 2009; Misztal et al., 2010]. Previous studies indicate a high SOA yield from Methyl Chavicol at around 40 % [Lee et al., 2006], however currently there have been very few literature

  15. Effect of Relative Humidity and Temperature on Photochemical Aging of Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Nizkorodov, S.; Brady, M. V.; Hinks, M. L.; Lignell, H.; Bertram, A. K.; Song, M.; Laskin, A.; Laskin, J.; Lin, P.

    2014-12-01

    The viscosity of secondary organic aerosol material (SOM) is known to depend sensitively on both temperature and relative humidity (RH). This work investigates the effect of these two important environmental variables on photochemical processes occurring inside model SOM. The experiments are designed to test the hypothesis that an increased SOM viscosity, resulting from either lower temperatures or decreased RH, should slow down the rates of photochemical processes in the organic matrix by constraining molecular motion inside the matrix. Photolysis of a probe molecule, 2,4-dinitrophenol, dispersed in SOM made produced through oxidation of alpha-pinene and limonene by ozone is investigated with absorption spectroscopy methods under controlled humidity and temperature. Viscosity of SOM is directly measured using "bead-mobility" technique and "poke-flow" techniques. Finally, the products of 2,4-dinitrophenol are analyzed by liquid chromatography high resolution mass spectrometry methods. The experiments suggest that the presence of water strongly affects photodegradation rates of organic compounds contained in the SOM matrix. Given the paramount role of photochemistry in driving the chemical reactions in the environment, these results will have significant implications for predicting lifetimes of photolabile atmospheric organic compounds trapped in organic particles.

  16. Effect of Slow Aging Reactions on Optical Properties of Secondary Organic Aerosol Prepared by Oxidation of Selected Monoterpenes

    NASA Astrophysics Data System (ADS)

    Nizkorodov, S. A.; Bones, D. L.; Henricksen, D. K.; Mang, S. A.; Bateman, A. P.; Pan, X.; Nguyen, T. B.; Gonsior, M.; Cooper, W.; Laskin, J.; Laskin, A.

    2009-05-01

    Organic particulate matter (PM) has a major impact on atmospheric chemistry, climate, and human health. Secondary organic aerosol (SOA) accounts for a rather significant fraction of organic PM; this includes SOA produced by oxidation of biogenically emitted monoterpenes. Once such SOA is formed, it is believed to undergo slow aging processes, which may have large effects on the physical and chemical properties of the particles. This presentation focuses on the effect of slow chemical aging on optical properties of SOA formed from the ozone-induced oxidation of limonene, myrcene, and other selected monoterpenes. Several complementary techniques including high resolution electrospray ionization mass spectrometry, FTIR spectroscopy, UV/vis spectroscopy, NMR spectroscopy, 3D-fluorescence spectroscopy, and photodissociation spectroscopy are used to probe the aging-induced changes in physical properties and chemical composition of laboratory generated SOA. Limonene SOA appears to undergo a dramatic change in its absorption spectrum on a time scale of hours; it develops strong visible bands in the 400-500 nm region, and becomes fluorescent. This transformation is catalyzed by ammonium sulfate and certain amino acids. This rather unusual aging process can potentially contribute to the formation of brown carbon in biogenic SOA.

  17. 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. PMID:27593289

  18. Photochemical Aging of α-pinene and β-pinene Secondary Organic Aerosol formed from Nitrate Radical Oxidation.

    PubMed

    Nah, Theodora; Sanchez, Javier; Boyd, Christopher M; Ng, Nga Lee

    2016-01-01

    The nitrate radical (NO3) is the dominant nighttime oxidant in most urban and rural environments and reacts rapidly with biogenic volatile organic compounds to form secondary organic aerosol (SOA) and organic nitrates (ON). Here, we study the formation of SOA and ON from the NO3 oxidation of two monoterpenes (α-pinene and β-pinene) and investigate how they evolve during photochemical aging. High SOA mass loadings are produced in the NO3+β-pinene reaction, during which we detected 41 highly oxygenated gas- and particle-phase ON possessing 4 to 9 oxygen atoms. The fraction of particle-phase ON in the β-pinene SOA remains fairly constant during photochemical aging. In contrast to the NO3+β-pinene reaction, low SOA mass loadings are produced during the NO3+α-pinene reaction, during which only 5 highly oxygenated gas- and particle-phase ON are detected. The majority of the particle-phase ON evaporates from the α-pinene SOA during photochemical aging, thus exhibiting a drastically different behavior from that of β-pinene SOA. Our results indicate that nighttime ON formed by NO3+monoterpene chemistry can serve as either permanent or temporary NOx sinks depending on the monoterpene precursor. PMID:26618657

  19. Aging of secondary organic aerosol from small aromatic VOCs. Changes in chemical composition, mass yield, volatility and hygroscopicity

    DOE PAGESBeta

    Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K.; Nenes, A.; Donahue, N. M.; Pandis, S. N.

    2014-12-12

    Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form and transform SOA from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx. The effects of chemical aging on organic aerosol (OA) composition, mass yield, volatility and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state OSC) and mass yield. The OA oxidation state generally increased during photo-oxidation, and the final OA OSmore » C ranged from -0.29 to 0.45 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.« less

  20. Parameterization of thermal properties of aging secondary organic aerosol produced by photo-oxidation of selected terpene mixtures.

    PubMed

    Emanuelsson, Eva U; Mentel, Thomas F; Watne, Agot K; Spindler, Christian; Bohn, Birger; Brauers, Theo; Dorn, Hans-Peter; Hallquist, Asa M; Häseler, Rolf; Kiendler-Scharr, Astrid; Müller, Klaus-Peter; Pleijel, Håkan; Rohrer, Franz; Rubach, Florian; Schlosser, Eric; Tillmann, Ralf; Hallquist, Mattias

    2014-06-01

    Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth's radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine TVFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. TVFR0.5 increased by 0.3±0.1% (ca. 1 K), while the steepness increased by 0.9±0.3% per hour of 1×10(6) cm(-3) OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH. PMID:24810838

  1. Photochemical age of air pollutants, ozone, and secondary organic aerosol in transboundary air observed on Fukue Island, Nagasaki, Japan

    NASA Astrophysics Data System (ADS)

    Irei, Satoshi; Takami, Akinori; Sadanaga, Yasuhiro; Nozoe, Susumu; Yonemura, Seiichiro; Bandow, Hiroshi; Yokouchi, Yoko

    2016-04-01

    To better understand the secondary air pollution in transboundary air over westernmost Japan, ground-based field measurements of the chemical composition of fine particulate matter ( ≤ 1 µm), mixing ratios of trace gas species (CO, O3, NOx, NOy, i-pentane, toluene, and ethyne), and meteorological elements were conducted with a suite of instrumentation. The CO mixing ratio dependence on wind direction showed that there was no significant influence from primary emission sources near the monitoring site, indicating long- and/or mid-range transport of the measured chemical species. Despite the considerably different atmospheric lifetimes of NOy and CO, these mixing ratios were correlated (r2 = 0.67). The photochemical age of the pollutants, t[OH] (the reaction time × the mean concentration of OH radical during the atmospheric transport), was calculated from both the NOx / NOy concentration ratio (NOx / NOy clock) and the toluene / ethyne concentration ratio (hydrocarbon clock). It was found that the toluene / ethyne concentration ratio was significantly influenced by dilution with background air containing 0.16 ppbv of ethyne, causing significant bias in the estimation of t[OH]. In contrast, the influence of the reaction of NOx with O3, a potentially biasing reaction channel on [NOx] / [NOy], was small. The t[OH] values obtained with the NOx / NOy clock ranged from 2.9 × 105 to 1.3 × 108 h molecule cm-3 and were compared with the fractional contribution of the m/z 44 signal to the total signal in the organic aerosol mass spectra (f44, a quantitative oxidation indicator of carboxylic acids) and O3 mixing ratio. The comparison of t[OH] with f44 showed evidence for a systematic increase of f44 as t[OH] increased, an indication of secondary organic aerosol (SOA) formation. To a first approximation, the f44 increase rate was (1.05 ± 0.03) × 10-9 × [OH] h-1, which is comparable to the background-corrected increase rate observed during the New England Air Quality

  2. Terpenylic acid and nine-carbon multifunctional compounds formed during the aging of β-pinene ozonolysis secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Sato, Kei; Jia, Tianyu; Tanabe, Kiyoshi; Morino, Yu; Kajii, Yoshizumi; Imamura, Takashi

    2016-04-01

    Recent field and laboratory studies suggest that forest aerosol particles contain more highly functionalized organic molecules than pinonic acid, a traditional molecular maker of secondary organic aerosol (SOA) particles. To investigate the reaction mechanisms during the aging of biogenic SOAs, the gases and particles formed from the ozonolysis of β- and α-pinene were exposed to OH radicals in a laboratory chamber. The particle samples were collected before and after OH exposure for analysis by liquid chromatography-negative electrospray ionization time-of-flight mass spectrometry. Pinic acid and terpenylic acid were abundant products in both β- and α-pinene ozonolysis SOA particles. Terpenylic acid and products with m/z 201.08 present in β-pinene SOA particles increased upon exposing SOA to OH radicals, whereas 3-methyl-1,2,3-butanetricarboxylic acid present in α-pinene SOA particles increased upon exposing SOA to OH radicals. The products with m/z 201.08 were suggested to be C9H14O5 compounds. Similar C9H14O5 compounds and terpenylic acid were also detected in SOA particles formed from the photooxidation of nopinone, a major first-generation product of β-pinene ozonolysis. The OH-initiated oxidation of nopinone will contribute to the formation of terpenylic acid and C9H14O5 compounds during the aging of β-pinene SOA. A formation mechanism for terpenylic acid via gas-phase diaterpenylic acid formation followed by self-dehydration in the condensed phase was suggested.

  3. Evolution of the complex refractive index in the near UV spectral region in ageing secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Flores, J. M.; Zhao, D. F.; Segev, L.; Schlag, P.; Kiendler-Scharr, A.; Fuchs, H.; Watne, Å. K.; Bluvshtein, N.; Mentel, Th. F.; Hallquist, M.; Rudich, Y.

    2014-02-01

    The chemical and physical properties of secondary organic aerosol (SOA) formed by the photochemical degradation of biogenic and anthropogenic volatile organic compounds (VOC) are yet poorly constrained. The evolution of the complex refractive index (RI) of SOA, formed from purely biogenic VOC and mixtures of biogenic and anthropogenic VOC was studied over a diurnal cycle in the SAPHIR photochemical outdoor chamber in Jülich, Germany. The correlation of RI with SOA chemical and physical properties such as oxidation level and volatility was examined. The RI was retrieved by a newly developed broadband cavity enhanced spectrometer for aerosol optical extinction measurements in the near UV spectral region (360 to 420 nm). Chemical composition and volatility of the particles were monitored by a high resolution time of flight aerosol mass spectrometer, and a volatility tandem differential mobility analyzer. SOA was formed by ozonolysis of either (i) a mixture of biogenic VOC (α-pinene and limonene), (ii) biogenic VOC mixture with subsequent addition of an anthropogenic VOC (p-xylene-d10), or (iii) a mixture of biogenic and anthropogenic VOC. The SOA aged by ozone / OH reactions up to 29.5 h was found to be non-absorbing in all cases. The SOA with p-xylene-d10 showed an increase of the scattering component of the RI correlated with an increase of the O / C ratio and with an increase in the SOA density. There was a greater increase in the scattering component of the RI when the SOA was produced from the mixture of biogenic VOCs and anthropogenic VOC than from the sequential addition of the VOCs after the approximate same ageing time. The increase of the scattering component was inversely correlated with the SOA volatility. Two RI retrievals determined for the pure biogenic SOA showed a constant RI for up to 5 h of ageing. Mass spectral characterization shows the three types of the SOA formed in this study have significant amount of semivolatile components. The influence

  4. 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

  5. Slow aging in Secondary Organic Aerosol observed by Liquid Chromatography coupled with High-Resolution Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bones, D. L.; Bateman, A. P.; Nguyen, T. B.; Laskin, J.; Laskin, A.; Nizkorodov, S.

    2009-12-01

    This study investigated long term changes in the chemical composition of model biogenic secondary organic aerosol (SOA) prepared via ozonolysis of the terpene limonene. This SOA has been observed to turn brown when exposed to NH4+. Our hypothesis is that the chromophoric compounds responsible for this color change are suspected to be imidazole-like or pyridinium-like compounds. These compounds are only present in small relative amounts, hence standard mass spectrometry is insufficient to unambiguously detect these compounds. However, a combination of HPLC and high resolution electrospray ionization mass spectrometry allows assignments of chemical formulae to individual peaks. These and other experiments confirm the presence of N-containing compounds in treated SOA. We are in the process of determining the exact identity of these species by MS/MS methods. LC-MS can also provide information about the polarity of the compounds in SOA. Most compounds in limonene-O3 SOA are polar and are detected at short retention times; peaks suggesting trimeric species appear at longer retention times in the case of fresh SOA, but at shorter times with the bulk of the components for aged SOA. Limonene SOA has been shown to be composed of monomers, dimers, trimers and larger oligomers. The appearance of trimers in specific regions of the chromatogram suggests these species are genuine SOA components and not an artifact of electrospray ionization. Changes in biogenic SOA over time are important because of the propensity of SOA to affect direct and indirect radiative forcing.

  6. 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

  7. Modeling the formamtion and aging of secondary organic aerosols in Los Angeles during CalNex 2010

    EPA Science Inventory

    Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of A...

  8. 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

  9. 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.

  10. Modeling the formation and aging of secondary organic aerosols in Los Angeles during CalNex 2010

    NASA Astrophysics Data System (ADS)

    Hayes, P. L.; Carlton, A. G.; Baker, K. R.; Ahmadov, R.; Washenfelder, R. A.; Alvarez, S.; Rappenglück, B.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Zotter, P.; Prévôt, A. S. H.; Szidat, S.; Kleindienst, T. E.; Offenberg, J. H.; Jimenez, J. L.

    2014-12-01

    Four different parameterizations for the formation and evolution of secondary organic aerosol (SOA) are evaluated using a 0-D box model representing the Los Angeles Metropolitan Region during the CalNex 2010 field campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model-measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model/measurement agreement for mass concentration. When comparing the three parameterizations, the Grieshop et al. (2009) parameterization more accurately reproduces both the SOA mass concentration and oxygen-to-carbon ratio inside the urban area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the observed SOA concentrations in Pasadena. All the parameterizations over-predict urban SOA formation at long

  11. Modeling the formation and aging of secondary organic aerosols in Los Angeles during CalNex 2010

    DOE PAGESBeta

    Hayes, P. L.; Carlton, A. G.; Baker, K. R.; Ahmadov, R.; Washenfelder, R. A.; Alvarez, S.; Rappenglück, B.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; et al

    2014-12-20

    Four different parameterizations for the formation and evolution of secondary organic aerosol (SOA) are evaluated using a 0-D box model representing the Los Angeles Metropolitan Region during the CalNex 2010 field campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generationmore » oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model-measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model/measurement agreement for mass concentration. When comparing the three parameterizations, the Grieshop et al. (2009) parameterization more accurately reproduces both the SOA mass concentration and oxygen-to-carbon ratio inside the urban area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the observed SOA concentrations in Pasadena. All the parameterizations over-predict urban SOA formation at long

  12. 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

  13. Modeling the formation and aging of secondary organic aerosols in Los Angeles during CalNex 2010

    DOE PAGESBeta

    Hayes, P. L.; Carlton, A. G.; Baker, K. R.; Ahmadov, R.; Washenfelder, R. A.; Alvarez, S.; Rappenglück, B.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; et al

    2015-05-26

    Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle- and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA that formed only from the oxidationmore » of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model–measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate-volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model–measurement agreement for mass concentration. The results from the three parameterizations show large differences (e.g., a factor of 3 in SOA mass) and are not well constrained, underscoring the current uncertainties in this area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the

  14. Modeling the formation and aging of secondary organic aerosols in Los Angeles during CalNex 2010

    NASA Astrophysics Data System (ADS)

    Hayes, P. L.; Carlton, A. G.; Baker, K. R.; Ahmadov, R.; Washenfelder, R. A.; Alvarez, S.; Rappengluck, B.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Zotter, P.; Prevot, A. S. H.; Szidat, S.; Kleindienst, T. E.; Offenberg, J. H.; Ma, P. K.; Jimenez, J. L.

    2015-05-01

    Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle- and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA that formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model-measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate-volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model-measurement agreement for mass concentration. The results from the three parameterizations show large differences (e.g., a factor of 3 in SOA mass) and are not well constrained, underscoring the current uncertainties in this area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the observed

  15. Aging of secondary organic aerosol generated from the ozonolysis of α-pinene: effects of ozone, light and temperature

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Formenti, P.; Picquet-Varrault, B.; Camredon, M.; Pangui, E.; Zapf, P.; Katrib, Y.; Giorio, C.; Tapparo, A.; Temime-Roussel, B.; Monod, A.; Aumont, B.; Doussin, J. F.

    2014-09-01

    A series of experiments was conducted in the CESAM simulation chamber to investigate the evolution of the physical and chemical properties of secondary organic aerosol (SOA) during different forcing. The present experiments represent a first attempt to comprehensively investigate the influence of oxidative processing, photochemistry, and diurnal temperature cycling upon SOA properties. SOA generated from the ozonolysis of α-pinene were exposed to (1) elevated ozone concentrations, (2) light (under controlled temperature conditions), or (3) light and heat (6 °C light-induced temperature increase), and the resultant changes in SOA optical properties (i.e. absorption and scattering), hygroscopicity and chemical composition were measured using a suite of instrumentation interfaced to the CESAM chamber. The complex refractive index (CRI) was derived from integrated nephelometer measurements at 525 nm wavelength, using Mie scattering calculations and measured number size distributions. The particle size growth factor (GF) was measured with a hygroscopic tandem differential mobility analyzer (H-TDMA). An aerosol mass spectrometer (AMS) was used for the determination of the f44 / f43 and O : C ratio of the particles bulk. No change in SOA size or chemical composition was observed during O3 and light exposure at constant temperature; in addition, GF and CRI of the SOA remained constant with forcing. By contrast, illumination of the SOA in the absence of temperature control led to an increase in the real part of the CRI from 1.35 (±0.03) to 1.49 (±0.03), an increase of the GF from 1.04 (±0.02) to 1.14 (±0.02) and an increase of the f44 / f43 ratio from 1.73 (±0.03) to 2.23 (±0.03). These surprising results suggest that SOA properties may be governed more by local temperature fluctuations than by oxidative processing and photochemistry.

  16. Aging of secondary organic aerosol generated from the ozonolysis of α-pinene: effects of ozone, light and temperature

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Formenti, P.; Picquet-Varrault, B.; Camredon, M.; Pangui, E.; Zapf, P.; Katrib, Y.; Giorio, C.; Tapparo, A.; Temime-Roussel, B.; Monod, A.; Aumont, B.; Doussin, J. F.

    2015-01-01

    A series of experiments was conducted in the CESAM (French acronym for Experimental Multiphasic Atmospheric Simulation Chamber) simulation chamber to investigate the evolution of the physical and chemical properties of secondary organic aerosols (SOAs) during different forcings. The present experiments represent a first attempt to comprehensively investigate the influence of oxidative processing, photochemistry, and diurnal temperature cycling upon SOA properties. SOAs generated from the ozonolysis of α-pinene were exposed under dry conditions (< 1% relative humidity) to (1) elevated ozone concentrations, (2) light (under controlled temperature conditions) or (3) light and heat (6 °C light-induced temperature increase), and the resultant changes in SOA optical properties (i.e. absorption and scattering), hygroscopicity and chemical composition were measured using a suite of instrumentation interfaced to the CESAM chamber. The complex refractive index (CRI) was derived from integrated nephelometer measurements of 525 nm wavelength, using Mie scattering calculations and measured number size distributions. The particle size growth factor (GF) was measured with a hygroscopic tandem differential mobility analyzer (H-TDMA). An aerosol mass spectrometer (AMS) was used for the determination of the f44 / f43 and O : C ratio of the particles bulk. No change in SOA size or chemical composition was observed during O3 and light exposure at constant temperature; in addition, GF and CRI of the SOA remained constant with forcing. On the contrary, illumination of SOAs in the absence of temperature control led to an increase in the real part of the CRI from 1.35 (±0.03) to 1.49 (±0.03), an increase of the GF from 1.04 (±0.02) to 1.14 (±0.02) and an increase of the f44 / f43 ratio from 1.73 (±0.03) to 2.23 (±0.03). The simulation of the experiments using the master chemical mechanism (MCM) and the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere

  17. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    NASA Astrophysics Data System (ADS)

    Ortega, A. M.; Hayes, P. L.; Peng, Z.; Palm, B. B.; Hu, W.; Day, D. A.; Li, R.; Cubison, M. J.; Brune, W. H.; Graus, M.; Warneke, C.; Gilman, J. B.; Kuster, W. C.; de Gouw, J. A.; Jimenez, J. L.

    2015-08-01

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An Oxidation Flow Reactor (OFR) was deployed to study SOA formation in real-time during the CalNex campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent atmospheric aging from hours up to several weeks in 3 min of processing. OH radical concentration was continuously stepped, obtaining measurements of real-time SOA formation and oxidation at multiple equivalent ages from 0.8 days-6.4 weeks. Enhancement of OA from aging showed a maximum net SOA production between 0.8-6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry, and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived VOC correlation, indicates the importance of relatively reactive (τOH ∼ 0.3 day) SOA precursors in the LA-Basin. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ∼ -0.65). Oxidation state of carbon (OSC) in reactor SOA increased steeply with age and remained elevated (OSC ∼ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and also extends to higher ages where OA loss dominates. The mass added at low

  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. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    DOE PAGESBeta

    Ortega, Amber M.; Hayes, Patrick L.; Peng, Zhe; Palm, Brett B.; Hu, Weiwei; Day, Douglas A.; Li, Rui; Cubison, Michael J.; Brune, William H.; Graus, Martin; et al

    2016-06-15

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient andmore » reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days–6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8–6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive (τOH ~ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ~ –0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OSC ~ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and

  20. Real-time measurements of secondary organic aerosol formation and aging from ambient air in an oxidation flow reactor in the Los Angeles area

    NASA Astrophysics Data System (ADS)

    Ortega, Amber M.; Hayes, Patrick L.; Peng, Zhe; Palm, Brett B.; Hu, Weiwei; Day, Douglas A.; Li, Rui; Cubison, Michael J.; Brune, William H.; Graus, Martin; Warneke, Carsten; Gilman, Jessica B.; Kuster, William C.; de Gouw, Joost; Gutiérrez-Montes, Cándido; Jimenez, Jose L.

    2016-06-01

    Field studies in polluted areas over the last decade have observed large formation of secondary organic aerosol (SOA) that is often poorly captured by models. The study of SOA formation using ambient data is often confounded by the effects of advection, vertical mixing, emissions, and variable degrees of photochemical aging. An oxidation flow reactor (OFR) was deployed to study SOA formation in real-time during the California Research at the Nexus of Air Quality and Climate Change (CalNex) campaign in Pasadena, CA, in 2010. A high-resolution aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS) alternated sampling ambient and reactor-aged air. The reactor produced OH concentrations up to 4 orders of magnitude higher than in ambient air. OH radical concentration was continuously stepped, achieving equivalent atmospheric aging of 0.8 days-6.4 weeks in 3 min of processing every 2 h. Enhancement of organic aerosol (OA) from aging showed a maximum net SOA production between 0.8-6 days of aging with net OA mass loss beyond 2 weeks. Reactor SOA mass peaked at night, in the absence of ambient photochemistry and correlated with trimethylbenzene concentrations. Reactor SOA formation was inversely correlated with ambient SOA and Ox, which along with the short-lived volatile organic compound correlation, indicates the importance of very reactive (τOH ˜ 0.3 day) SOA precursors (most likely semivolatile and intermediate volatility species, S/IVOCs) in the Greater Los Angeles Area. Evolution of the elemental composition in the reactor was similar to trends observed in the atmosphere (O : C vs. H : C slope ˜ -0.65). Oxidation state of carbon (OSc) in reactor SOA increased steeply with age and remained elevated (OSC ˜ 2) at the highest photochemical ages probed. The ratio of OA in the reactor output to excess CO (ΔCO, ambient CO above regional background) vs. photochemical age is similar to previous studies at low to moderate ages and also extends to

  1. Aging and Work Organizations.

    ERIC Educational Resources Information Center

    Schrank, Harris T.; Waring, Joan M.

    Business firms are an integral part of the age stratification structure of society. Although the age structures of people and roles within the organization are dynamic, these structures yield a fairly stable strata in which norms exist to suggest the various roles expected of certain persons. Those in roles with greater financial rewards, power,…

  2. Aging and Aged in Organized Crime.

    ERIC Educational Resources Information Center

    Amir, Menachem

    1989-01-01

    Examines problems of the aged in organized crime, basing discussion on organized crime bosses over age 60 operating in Italy, the United States, and Israel. Looks at problems stemming from normative system in organized crime, role of the aged, intergenerational problems, fears of the aged, excuses and justifications, standards of life, and…

  3. THE ROLE OF NITRATE RADICALS (NO3) IN AEROSOL LIFE CYCLE: SECONDARY ORGANIC AEROSOL FORMATION AND AGING OF ATMOSPHERIC ORGANIC AEROSOLS

    EPA Science Inventory

    This study will provide an extensive data set on SOA formation from nitrate oxidation pathway and the multigenerational chemistry involving both photochemical and dark aging. Yield parameters (e.g., Odum 2 product model, 2D volatility basis set) can be directly obtained fro...

  4. Photochemical Aging of α-pinene and β-pinene Secondary Organic Aerosol formed from Nitrate Radical Oxidation: New Insights into the Formation and Fates of Highly Oxygenated Gas- and Particle-phase Organic Nitrates

    NASA Astrophysics Data System (ADS)

    Nah, T.; Sanchez, J.; Boyd, C.; Ng, N. L.

    2015-12-01

    The nitrate radical (NO3), one of the most important oxidants in the nocturnal atmosphere, can react rapidly with a variety of biogenic volatile organic compounds (BVOCs) to form high mass concentrations of secondary organic aerosol (SOA) and organic nitrates (ON). Despite its critical importance in aerosol formation, the mechanisms and products from the NO3 oxidation of BVOCs have been largely unexplored, and the fates of their SOA and ON after formation are not well characterized. In this work, we studied the formation of SOA and ON from the NO3 oxidation of α-pinene and β-pinene and investigated for the first time how they evolve during dark and photochemical aging through a series of chamber experiments performed at the Georgia Tech Environmental Chamber (GTEC) facility. The α-pinene and β-pinene SOA are characterized using real-time gas- and particle-phase measurements, which are used to propose mechanisms for SOA and organic nitrate formation and aging. Highly oxygenated gas- and particle-phase ON (containing as many as 9 oxygen atoms) are detected during the NO3 reaction. In addition, the β-pinene SOA and α-pinene SOA exhibited drastically different behavior during photochemical aging. Our results indicate that nighttime ON formed by NO3+monoterpene chemistry can serve as either NOx reservoirs or sinks depending on the monoterpene precursor. Results from this study provide fundamental data for evaluating the contributions of NO3+monoterpene reactions to ambient OA measured in the Southeastern U.S.

  5. Simulating secondary organic aerosol in a regional air quality model using the statistical oxidation model - Part 1: Assessing the influence of constrained multi-generational ageing

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Multi-generational oxidation of volatile organic compound (VOC) oxidation products can significantly alter the mass, chemical composition and properties of secondary organic aerosol (SOA) compared to calculations that consider only the first few generations of oxidation reactions. However, the most commonly used state-of-the-science schemes in 3-D regional or global models that account for multi-generational oxidation (1) consider only functionalization reactions but do not consider fragmentation reactions, (2) have not been constrained to experimental data and (3) are added on top of existing parameterizations. The incomplete description of multi-generational oxidation in these models has the potential to bias source apportionment and control calculations for SOA. In this work, we used the statistical oxidation model (SOM) of Cappa and Wilson (2012), constrained by experimental laboratory chamber data, to evaluate the regional implications of multi-generational oxidation considering both functionalization and fragmentation reactions. SOM was implemented into the regional University of California at Davis / California Institute of Technology (UCD/CIT) air quality model and applied to air quality episodes in California and the eastern USA. The mass, composition and properties of SOA predicted using SOM were compared to SOA predictions generated by a traditional two-product model to fully investigate the impact of explicit and self-consistent accounting of multi-generational oxidation.Results show that SOA mass concentrations predicted by the UCD/CIT-SOM model are very similar to those predicted by a two-product model when both models use parameters that are derived from the same chamber data. Since the two-product model does not explicitly resolve multi-generational oxidation reactions, this finding suggests that the chamber data used to parameterize the models captures the majority of the SOA mass formation from multi-generational oxidation under the conditions

  6. 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...

  7. Chemistry of secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Yee, Lindsay Diana

    The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed. Three methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position. The photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the

  8. Aqueous phase processing of secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Tritscher, T.; Praplan, A. P.; Decarlo, P. F.; Temime-Roussel, B.; Quivet, E.; Marchand, N.; Dommen, J.; Baltensperger, U.; Monod, A.

    2011-07-01

    The aging of secondary organic aerosol (SOA) by photooxidation in the aqueous phase was experimentally investigated. To simulate multiphase processes, the following experiments were sequentially performed in a smog chamber and in an aqueous phase photoreactor: (1) Gas-phase photooxidation of three different volatile organic compounds (VOC): isoprene, α-pinene, and 1,3,5-trimethylbenzene (TMB) in the presence of NOx, leading to the formation of SOA which was subjected to on-line physical and chemical analysis; (2) particle-to-liquid transfer of water soluble species of SOA using filter sampling and aqueous extraction; (3) aqueous-phase photooxidation of the obtained water extracts; and (4) nebulization of the solutions for a repetition of the on-line characterization. SOA concentrations in the chamber measured with a scanning mobility particle sizer (SMPS) were higher than 200 μg m-3, as the experiments were conducted under high initial concentrations of volatile organic compounds (VOC) and NOx. The aging of SOA through aqueous phase processing was investigated by measuring the physical and chemical properties of the particles online before and after processing using a high resolution time-of-flight aerosol mass spectrometer (AMS) and a hygroscopicity tandem differential mobility analyzer (H-TDMA). It was shown that, after aqueous phase processing, the particles were significantly more hygroscopic, and contained more fragmentation ions at m/z = 44 and less ions at m/z = 43, thus showing a significant impact on SOA aging for the three different precursors. Additionally, the particles were analyzed with a thermal desorption atmospheric pressure ionization aerosol mass spectrometer (TD-API-AMS). Comparing the smog chamber SOA composition and non processed nebulized aqueous extracts with this technique revealed that sampling, extraction and/or nebulization did not significantly impact the chemical composition of SOA formed from isoprene and α-pinene, whereas it

  9. Organic Horticulture in the Secondary School

    ERIC Educational Resources Information Center

    Marrocco, Aldo

    2009-01-01

    This report is based on five years experience working with primary and secondary school teachers in Italy to develop organic farming as an activity for students. The tasks involved were intended to develop our students' environmental awareness, allow them to produce food organically and show that market gardening could be a productive hobby. In…

  10. Constraining Predicted Secondary Organic Aerosol Formation and Processing Using Real-Time Observations of Aging Urban Emissions in an Oxidation Flow Reactor

    NASA Astrophysics Data System (ADS)

    Ortega, A. M.; Palm, B. B.; Hayes, P. L.; Day, D. A.; Cubison, M.; Brune, W. H.; Hu, W.; Graus, M.; Warneke, C.; Gilman, J.; De Gouw, J. A.; Jimenez, J. L.

    2014-12-01

    To investigate atmospheric processing of urban emissions, we deployed an oxidation flow reactor with measurements of size-resolved chemical composition of submicron aerosol during CalNex-LA, a field study investigating air quality and climate change at a receptor site in the Los Angeles Basin. The reactor produces OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent atmospheric aging of hours to ~2 weeks in 5 minutes of processing. The OH exposure (OHexp) was stepped every 20 min to survey the effects of a range of oxidation exposures on gases and aerosols. This approach is a valuable tool for in-situ evaluation of changes in organic aerosol (OA) concentration and composition due to photochemical processing over a range of ambient atmospheric conditions and composition. Combined with collocated gas-phase measurements of volatile organic compounds, this novel approach enables the comparison of measured SOA to predicted SOA formation from a prescribed set of precursors. Results from CalNex-LA show enhancements of OA and inorganic aerosol from gas-phase precursors. The OA mass enhancement from aging was highest at night and correlated with trimethylbenzene, indicating the importance of relatively short-lived VOC (OH lifetime of ~12 hrs or less) as SOA precursors in the LA Basin. Maximum net SOA production is observed between 3-6 days of aging and decreases at higher exposures. Aging in the reactor shows similar behavior to atmospheric processing; the elemental composition of ambient and reactor measurements follow similar slopes when plotted in a Van Krevelen diagram. Additionally, for air processed in the reactor, oxygen-to-carbon ratios (O/C) of aerosol extended over a larger range compared to ambient aerosol observed in the LA Basin. While reactor aging always increases O/C, often beyond maximum observed ambient levels, a transition from net OA production to destruction occurs at intermediate OHexp, suggesting a transition

  11. Secondary infertility and the aging male, overview

    PubMed Central

    Al–Hawsawi, Khalid; Motair, Wael; Bawa, Abdallah Makhloof

    2014-01-01

    Introduction Old men preparing themselves for marriage late in their lives might face infertility. Infertility in this group of men should be considered from a wider perspective, as they face any age–related health troubles that include, but are not limited to, androgen deficiency and psychological disorders that impede early conception. This review aims to shed light on the proper approach to this minority of secondarily infertile men. Material and methods A comprehensive electronic English literature search was conducted, using various medical websites and books, for the factors that cause infertility in senior fathers. The physiology of geriatric males, together with their common comorbidities, were discussed. Results Old men presenting with secondary infertility should be approached differently. Aging, itself, has a significant impact on male sexual function, sperm parameters, and fertility; all of which contribute to poor fecundability, decreased fertilizing capacity, increased time to pregnancy, increased rate of DNA damage, high abortion rates and increased prevalence of fetal developmental failures. The complexity and the unknowns of the aging male physiology, together with the interaction of obstinate diseases the patient might have, make the issue very difficult to tackle. Conclusions Management should include the conventional way of treating young sufferers and further target the underlying causes, if known, along with the provision of geriatric, psychologic, and andrologic support. PMID:25140235

  12. Organosulfate Formation in Biogenic Secondary Organic Aerosol

    EPA Science Inventory

    Organosulfates of isoprene, α-pinene, and β-pinene have recently been identified in both laboratory-generated and ambient secondary organic aerosol (SOA). In this study, the mechanism and ubiquity of organosulfate formation in biogenic SOA is investigated by a comprehensive seri...

  13. 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...

  14. THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS

    EPA Science Inventory

    Volume concentrations of steady-state secondary organic aerosol (SOA) were measured in several hydrocarbon/NOx irradiation experiments. These measurements were used to estimate the thermal behavior of the particles that may be formed in the atmosphere. These laborator...

  15. Evaluation of one-dimensional and two-dimensional volatility basis sets in simulating the aging of secondary organic aerosol with smog-chamber experiments.

    PubMed

    Zhao, Bin; Wang, Shuxiao; Donahue, Neil M; Chuang, Wayne; Hildebrandt Ruiz, Lea; Ng, Nga L; Wang, Yangjun; Hao, Jiming

    2015-02-17

    We evaluate the one-dimensional volatility basis set (1D-VBS) and two-dimensional volatility basis set (2D-VBS) in simulating the aging of SOA derived from toluene and α-pinene against smog-chamber experiments. If we simulate the first-generation products with empirical chamber fits and the subsequent aging chemistry with a 1D-VBS or a 2D-VBS, the models mostly overestimate the SOA concentrations in the toluene oxidation experiments. This is because the empirical chamber fits include both first-generation oxidation and aging; simulating aging in addition to this results in double counting of the initial aging effects. If the first-generation oxidation is treated explicitly, the base-case 2D-VBS underestimates the SOA concentrations and O:C increase of the toluene oxidation experiments; it generally underestimates the SOA concentrations and overestimates the O:C increase of the α-pinene experiments. With the first-generation oxidation treated explicitly, we could modify the 2D-VBS configuration individually for toluene and α-pinene to achieve good model-measurement agreement. However, we are unable to simulate the oxidation of both toluene and α-pinene with the same 2D-VBS configuration. We suggest that future models should implement parallel layers for anthropogenic (aromatic) and biogenic precursors, and that more modeling studies and laboratory research be done to optimize the "best-guess" parameters for each layer. PMID:25581402

  16. Ultraviolet Absorption by Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.

  17. Evolved gas analysis of secondary organic aerosols

    SciTech Connect

    Grosjean, D.; Williams, E.L. II; Grosjean, E. ); Novakov, T. )

    1994-11-01

    Secondary organic aerosols have been characterized by evolved gas analysis (EGA). Hydrocarbons selected as aerosol precursors were representative of anthropogenic emissions (cyclohexene, cyclopentene, 1-decene and 1-dodecene, n-dodecane, o-xylene, and 1,3,5-trimethylbenzene) and of biogenic emissions (the terpenes [alpha]-pinene, [beta]-pinene and d-limonene and the sesquiterpene trans-caryophyllene). Also analyzed by EGA were samples of secondary, primary (highway tunnel), and ambient (urban) aerosols before and after exposure to ozone and other photochemical oxidants. The major features of the EGA thermograms (amount of CO[sub 2] evolved as a function of temperature) are described. The usefulness and limitations of EGA data for source apportionment of atmospheric particulate carbon are briefly discussed. 28 refs., 7 figs., 4 tabs.

  18. 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

  19. Secondary Forest Age and Tropical Forest Biomass Estimation Using TM

    NASA Technical Reports Server (NTRS)

    Nelson, R. F.; Kimes, D. S.; Salas, W. A.; Routhier, M.

    1999-01-01

    The age of secondary forests in the Amazon will become more critical with respect to the estimation of biomass and carbon budgets as tropical forest conversion continues. Multitemporal Thematic Mapper data were used to develop land cover histories for a 33,000 Square kM area near Ariquemes, Rondonia over a 7 year period from 1989-1995. The age of the secondary forest, a surrogate for the amount of biomass (or carbon) stored above-ground, was found to be unimportant in terms of biomass budget error rates in a forested TM scene which had undergone a 20% conversion to nonforest/agricultural cover types. In such a situation, the 80% of the scene still covered by primary forest accounted for over 98% of the scene biomass. The difference between secondary forest biomass estimates developed with and without age information were inconsequential relative to the estimate of biomass for the entire scene. However, in futuristic scenarios where all of the primary forest has been converted to agriculture and secondary forest (55% and 42% respectively), the ability to age secondary forest becomes critical. Depending on biomass accumulation rate assumptions, scene biomass budget errors on the order of -10% to +30% are likely if the age of the secondary forests are not taken into account. Single-date TM imagery cannot be used to accurately age secondary forests into single-year classes. A neural network utilizing TM band 2 and three TM spectral-texture measures (bands 3 and 5) predicted secondary forest age over a range of 0-7 years with an RMSE of 1.59 years and an R(Squared) (sub actual vs predicted) = 0.37. A proposal is made, based on a literature review, to use satellite imagery to identify general secondary forest age groups which, within group, exhibit relatively constant biomass accumulation rates.

  20. Industrial age to information age organizations: Changing business ethic

    SciTech Connect

    Stinson, J.E.

    1994-12-31

    In this paper, we argue that Informatoin age organizations both allow and require a higher level of moral development on the part of the members of the organizations. We describe industrial age and information age organization structure charactreistics and identify moral values consistent with each structure.

  1. Quantifying water diffusion in secondary organic material

    NASA Astrophysics Data System (ADS)

    Price, Hannah; Murray, Benjamin; Mattsson, Johan; O'Sullivan, Daniel; Wilson, Theodore; Zhang, Yue; Martin, Scot

    2014-05-01

    Recent research suggests that some secondary organic aerosol (SOA) is highly viscous under certain atmospheric conditions. This may have important consequences for equilibration timescales, SOA growth, heterogeneous chemistry and ice nucleation. In order to quantify these effects, knowledge of the diffusion coefficients of relevant gas species within aerosol particles is vital. In this work, a Raman isotope tracer method is used to quantify water diffusion coefficients over a range of atmospherically relevant humidity and temperature conditions. D2O is observed as it diffuses from the gas phase into a disk of aqueous solution, without the disk changing in size or viscosity. An analytical solution of Fick's second law is then used with a fitting procedure to determine water diffusion coefficients in reference materials for method validation. The technique is then extended to compounds of atmospheric relevance and α-pinene secondary organic material. We produce water diffusion coefficients from 20 to 80 % RH at 23.5° C for sucrose, levoglucosan, M5AS and MgSO4. For levoglucosan we show that under conditions where a particle bounces, water diffusion in aqueous solutions can be fast (a fraction of a second for a 100 nm radius). For sucrose solutions, we also show that the Stokes-Einstein relation breaks down at high viscosity and cannot be used to predict water diffusion timescales with accuracy. In addition, we also quantify water diffusion coefficients in α-pinene SOM from 20-80% RH and over temperatures from 6 to -30° C. Our results suggest that, at 6° C, water diffusion in α-pinene SOA is not kinetically limited on the second timescale, even at 20% RH. As temperatures decrease, however, diffusion slows and may become an increasingly limiting factor for atmospheric processes. A parameterization for the diffusion coefficient of water in α-pinene secondary organic material, as a function of relative humidity and temperature, is presented. The implications for

  2. Innate lymphoid cells in secondary lymphoid organs.

    PubMed

    Bar-Ephraïm, Yotam E; Mebius, Reina E

    2016-05-01

    The family of innate lymphoid cells (ILCs) has attracted attention in recent years as its members are important regulators of immunity, while they can also cause pathology. In both mouse and man, ILCs were initially discovered in developing lymph nodes as lymphoid tissue inducer (LTi) cells. These cells form the prototypic members of the ILC family and play a central role in the formation of secondary lymphoid organs (SLOs). In the absence of LTi cells, lymph nodes (LN) and Peyer's Patches (PP) fail to form in mice, although the splenic white pulp can develop normally. Besides LTi cells, the ILC family encompasses helper-like ILCs with functional distinctions as seen by T-helper cells, as well as cytotoxic natural killer (NK) cells. ILCs are still present in adult SLOs where they have been shown to play a role in lymphoid tissue regeneration. Furthermore, ILCs were implicated to interact with adaptive lymphocytes and influence the adaptive immune response. Here, we review the recent literature on the role of ILCs in secondary lymphoid tissue from the formation of SLOs to mature SLOs in adults, during homeostasis and pathology. PMID:27088915

  3. GAP junctional communication in brain secondary organizers.

    PubMed

    Bosone, Camilla; Andreu, Abraham; Echevarria, Diego

    2016-06-01

    Gap junctions (GJs) are integral membrane proteins that enable the direct cytoplasmic exchange of ions and low molecular weight metabolites between adjacent cells. They are formed by the apposition of two connexons belonging to adjacent cells. Each connexon is formed by six proteins, named connexins (Cxs). Current evidence suggests that gap junctions play an important part in ensuring normal embryo development. Mutations in connexin genes have been linked to a variety of human diseases, although the precise role and the cell biological mechanisms of their action remain almost unknown. Among the big family of Cxs, several are expressed in nervous tissue but just a few are expressed in the anterior neural tube of vertebrates. Many efforts have been made to elucidate the molecular bases of Cxs cell biology and how they influence the morphogenetic signal activity produced by brain signaling centers. These centers, orchestrated by transcription factors and morphogenes determine the axial patterning of the mammalian brain during its specification and regionalization. The present review revisits the findings of GJ composed by Cx43 and Cx36 in neural tube patterning and discuss Cx43 putative enrollment in the control of Fgf8 signal activity coming from the well known secondary organizer, the isthmic organizer. PMID:27273333

  4. Characterizing the formation of secondary organic aerosols

    SciTech Connect

    Lunden, Melissa; Black, Douglas; Brown, Nancy

    2004-02-01

    Organic aerosol is an important fraction of the fine particulate matter present in the atmosphere. This organic aerosol comes from a variety of sources; primary organic aerosol emitted directly from combustion process, and secondary aerosol formed in the atmosphere from condensable vapors. This secondary organic aerosol (SOA) can result from both anthropogenic and biogenic sources. In rural areas of the United States, organic aerosols can be a significant part of the aerosol load in the atmosphere. However, the extent to which gas-phase biogenic emissions contribute to this organic load is poorly understood. Such an understanding is crucial to properly apportion the effect of anthropogenic emissions in these rural areas that are sometimes dominated by biogenic sources. To help gain insight on the effect of biogenic emissions on particle concentrations in rural areas, we have been conducting a field measurement program at the University of California Blodgett Forest Research Facility. The field location includes has been used to acquire an extensive suite of measurements resulting in a rich data set, containing a combination of aerosol, organic, and nitrogenous species concentration and meteorological data with a long time record. The field location was established in 1997 by Allen Goldstein, a professor in the Department of Environmental Science, Policy and Management at the University of California at Berkeley to study interactions between the biosphere and the atmosphere. The Goldstein group focuses on measurements of concentrations and whole ecosystem biosphere-atmosphere fluxes for volatile organic compounds (VOC's), oxygenated volatile organic compounds (OVOC's), ozone, carbon dioxide, water vapor, and energy. Another important collaborator at the Blodgett field location is Ronald Cohen, a professor in the Chemistry Department at the University of California at Berkeley. At the Blodgett field location, his group his group performs measurements of the

  5. Photochemical Aging of Organic Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Nizkorodov, S. A.; Bateman, A. P.; Dailo, M.; Do, T.; Mang, S. A.; Pan, X.; Underwood, J. S.; Walser, M. L.

    2007-05-01

    Secondary Organic Aerosol (SOA) particles are produced in the atmosphere as a result of oxidation of volatile organic compounds (VOC). Primary Organic Aerosol (POA) particles are directly emitted in the atmosphere by their sources. This research focuses on the mechanisms of direct photochemical processes taking place in model SOA and POA particles, the role of such processes in aging of organic aerosol particles, and the effect of photochemistry on particles' physicochemical properties. To address these questions, artificial SOA and POA particles are investigated with several laboratory-based approaches relying on cavity ring-down spectroscopy and mass-spectrometry. SOA particles generated by dark oxidation of d-Limonene, alpha-Pinene, and beta-Pinene by ozone are all found to absorb radiation in the tropospheric actinic window. The UV absorption photolyzes SOA constituents resulting in a release of small VOC molecules back in the gas-phase, and considerable change in SOA chemical composition. For terpenes featuring a terminal double bond, the main SOA photolysis products are invariably found to be formaldehyde and formic acid. Similar observations are obtained for products of ozonolysis of thin films of unsaturated fatty acids and self-assembled monolayers of unsaturated alkenes. For the case of fatty acids, a very detailed mechanism of ozonolysis and subsequent photolysis is proposed. The photolytic activity is primarily attributed to organic peroxides and aldehydes. These results convincingly demonstrate that photochemical processes occurring inside SOA and POA particles age the particles on time scales that are shorter than typical lifetimes of aerosol particles in the atmosphere.

  6. CARES Helps Explain Secondary Organic Aerosols

    SciTech Connect

    Zaveri, Rahul

    2014-03-28

    What happens when urban man-made pollution mixes with what we think of as pristine forest air? To know more about what this interaction means for the climate, the Carbonaceous Aerosol and Radiative Effects Study, or CARES, field campaign was designed in 2010. The sampling strategy during CARES was coordinated with CalNex 2010, another major field campaign that was planned in California in 2010 by the California Air Resources Board (CARB), the National Oceanic and Atmospheric Administration (NOAA), and the California Energy Commission (CEC). "We found two things. When urban pollution mixes with forest pollutions we get more secondary organic aerosols," said Rahul Zaveri, FCSD scientist and project lead on CARES. "SOAs are thought to be formed primarily from forest emissions but only when they interact with urban emissions. The data is saying that there will be climate cooling over the central California valley because of these interactions." Knowledge gained from detailed analyses of data gathered during the CARES campaign, together with laboratory experiments, is being used to improve existing climate models.

  7. CARES Helps Explain Secondary Organic Aerosols

    ScienceCinema

    Zaveri, Rahul

    2014-06-02

    What happens when urban man-made pollution mixes with what we think of as pristine forest air? To know more about what this interaction means for the climate, the Carbonaceous Aerosol and Radiative Effects Study, or CARES, field campaign was designed in 2010. The sampling strategy during CARES was coordinated with CalNex 2010, another major field campaign that was planned in California in 2010 by the California Air Resources Board (CARB), the National Oceanic and Atmospheric Administration (NOAA), and the California Energy Commission (CEC). "We found two things. When urban pollution mixes with forest pollutions we get more secondary organic aerosols," said Rahul Zaveri, FCSD scientist and project lead on CARES. "SOAs are thought to be formed primarily from forest emissions but only when they interact with urban emissions. The data is saying that there will be climate cooling over the central California valley because of these interactions." Knowledge gained from detailed analyses of data gathered during the CARES campaign, together with laboratory experiments, is being used to improve existing climate models.

  8. Redox activity of naphthalene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    McWhinney, R. D.; Zhou, S.; Abbatt, J. P. D.

    2013-04-01

    Chamber secondary organic aerosol (SOA) from low-NOx photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox active, consuming DTT at an average rate of 118 ± 14 pmol per minute per μg of SOA material. Measured particle-phase masses of the major previously identified redox active products, 1,2- and 1,4-naphthoquinone, accounted for only 21 ± 3% of the observed redox cycling activity. The redox-active 5-hydroxy-1,4-naphthoquinone was identified as a new minor product of naphthalene oxidation, and including this species in redox activity predictions increased the predicted DTT reactivity to 30 ± 5% of observations. Similar attempts to predict redox behaviour of oxidised two-stroke engine exhaust particles by measuring 1,2-naphthoquinone, 1,4-naphthoquinone and 9,10-phenanthrenequinone predicted DTT decay rates only 4.9 ± 2.5% of those observed. Together, these results suggest that there are substantial unidentified redox-active SOA constituents beyond the small quinones that may be important toxic components of these particles. A gas-to-SOA particle partitioning coefficient was calculated to be (7.0 ± 2.5) × 10-4 m3 μg-1 for 1,4-naphthoquinone at 25 °C. This value suggests that under typical warm conditions, 1,4-naphthoquinone is unlikely to contribute strongly to redox behaviour of ambient particles, although further work is needed to determine the potential impact under conditions such as low temperatures where partitioning to the particle is more favourable. As well, higher order oxidation products that likely account for a substantial fraction of the redox cycling capability of the naphthalene SOA are likely to partition much more strongly to the particle phase.

  9. Secondary organic aerosol from biogenic volatile organic compound mixtures

    NASA Astrophysics Data System (ADS)

    Hatfield, Meagan L.; Huff Hartz, Kara E.

    2011-04-01

    The secondary organic aerosol (SOA) yields from the ozonolysis of a Siberian fir needle oil (SFNO), a Canadian fir needle oil (CFNO), and several SOA precursor mixtures containing reactive and non-reactive volatile organic compounds (VOCs) were investigated. The use of precursor mixtures more completely describes the atmosphere where many VOCs exist. The addition of non-reactive VOCs such as bornyl acetate, camphene, and borneol had very little to no effect on SOA yields. The oxidation of VOC mixtures with VOC mass percentages similar to the SFNO produced SOA yields that became more similar to the SOA yield from SFNO as the complexity and concentration of VOCs within the mixture became more similar to overall SFNO composition. The SOA yield produced by the oxidation of CFNO was within the error of the SOA yield produced by the oxidation of SFNO at a similar VOC concentration. The SOA yields from SFNO were modeled using the volatility basis set (VBS), which predicts the SOA yields for a given mass concentration of mixtures containing similar VOCs.

  10. Graphic Organizers Applied to Higher-Level Secondary Mathematics.

    ERIC Educational Resources Information Center

    Ives, Bob; Hoy, Cheri

    2003-01-01

    This article provides a rationale for using graphic organizers based on the fact that students with language disorders often struggle with traditional instruction that places large demands on language skills. Effective features of graphic organizers are identified and examples of direct instruction in secondary algebra using graphic organizers are…

  11. Cluster analysis on mass spectra of biogenic secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Spindler, C.; Kiendler-Scharr, A.; Kleist, E.; Mensah, A.; Mentel, T.; Tillmann, R.; Wildt, J.

    2009-04-01

    Biogenic secondary organic aerosols (BSOA) are of high importance in the atmosphere. The formation of SOA from the volatile organic compound (VOC) emissions of selected trees was investigated in the JPAC (Jülich Plant Aerosol Chamber) facility. The VOC (mainly monoterpenes) were transferred into a reaction chamber where vapors were photo-chemically oxidized and formed BSOA. The aerosol was characterized by aerosol mass spectrometry (Aerodyne Quadrupol-AMS). Inside the AMS, flash-vaporization of the aerosol particles and electron impact ionization of the evaporated molecules cause a high fragmentation of the organic compounds. Here, we present a classification of the aerosol mass spectra via cluster analysis. Average mass spectra are produced by combination of related single mass spectra to so-called clusters. The mass spectra were similar due to the similarity of the precursor substances. However, we can show that there are differences in the BSOA mass spectra of different tree species. Furthermore we can distinguish the influence of the precursor chemistry and chemical aging. BSOA formed from plants exposed to stress can be distinguished from BSOA formed under non stressed conditions. Significance and limitations of the clustering method for very similar mass spectra will be demonstrated and discussed.

  12. New Particle Formation and Secondary Organic Aerosol in Beijing

    NASA Astrophysics Data System (ADS)

    Hu, M.; Yue, D.; Guo, S.; Hu, W.; Huang, X.; He, L.; Wiedensohler, A.; Zheng, J.; Zhang, R.

    2011-12-01

    Air pollution in Beijing has been a major concern due to being a mega-city and green Olympic Games requirements. Both long term and intensive field measurements have been conducted at an Urban Air Quality Monitoring Station in the campus of Peking University since 2004. Aerosol characteristics vary seasonally depending on meteorological conditions and source emissions. Secondary compositions of SNA (sum of sulfate, nitrate, and ammonium) and SOA (secondary organic aerosol) become major fraction of fine particles, which may enhance aerosol impacts on visibility and climate change. The transformation processes of new particle formation (NPF) and secondary organic aerosol have been focused on. It was found that gaseous sulfuric acid, ammonia, and organic compounds are important precursors to NPF events in Beijing and H2SO4-NH3-H2O ternary nucleation is one of the important mechanisms. The contributions of condensation and neutralization of sulfuric acid, coagulation, and organics to the growth of the new particles are estimated as 45%, 34%, and 21%, respectively. Tracer-based method to estimate biogenic and anthropogenic SOA was established by using gas chromatography-mass spectrometry. Secondary organic tracers derived from biogenic (isoprene, α-pinene, β-caryophyllene) and anthropogenic (toluene) contributed 32% at urban site and 35% at rural site, respectively. Other source apportionment techniques were also used to estimate secondary organic aerosols, including EC tracer method, water soluble organic carbon content, chemical mass balance model, and AMS-PMF method.

  13. Experimental Determination of Chemical Diffusion within Secondary Organic Aerosol Particles

    SciTech Connect

    Abramson, Evan H.; Imre, D.; Beranek, Josef; Wilson, Jacqueline; Zelenyuk, Alla

    2013-02-28

    Formation, properties, transformations, and temporal evolution of secondary organic aerosols (SOA) particles strongly depend on particle phase. Recent experimental evidence from a number of groups indicates that SOA is in a semi-solid phase, the viscosity of which remained unknown. We find that when SOA is made in the presence of vapors of volatile hydrophobic molecules the SOA particles absorb and trap them. Here, we illustrate that it is possible to measure the evaporation rate of these molecules that is determined by their diffusion in SOA, which is then used to calculate a reasonably accurate value for the SOA viscosity. We use pyrene as a tracer molecule and a-pinene SOA as an illustrative case. It takes ~24 hours for half the pyrene to evaporate to yield a viscosity of 10^8 Pa s for a-pinene. This viscosity is consistent with measurements of particle bounce and evaporation rates. We show that viscosity of 10^8 Pa s implies coalescence times of minutes, consistent with the findings that SOA particles are spherical. Similar measurements on aged SOA particles doped with pyrene yield a viscosity of 10^9 Pa s, indicating that hardening occurs with time, which is consistent with observed decrease in water uptake and evaporation rate with aging.

  14. Distant Secondary Craters and Age Constraints on Young Martian Terrains

    NASA Technical Reports Server (NTRS)

    McEwen, A.; Preblich, B.; Turtle, E.; Studer, D.; Artemieva, N.; Golombek, M.; Hurst, M.; Kirk, R.; Burr, D.

    2005-01-01

    Are small (less than approx. 1 km diameter) craters on Mars and the Moon dominated by primary impacts, by secondary impacts of much larger primary craters, or are both primaries and secondaries significant? This question is critical to age constraints for young terrains and for older terrains covering small areas, where only small craters are superimposed on the unit. If the martian rayed crater Zunil is representative of large impact events on Mars, then the density of secondaries should exceed the density of primaries at diameters a factor of 1000 smaller than that of the largest contributing primary crater. On the basis of morphology and depth/diameter measurements, most small craters on Mars could be secondaries. Two additional observations (discussed below) suggest that the production functions of Hartmann and Neukum predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications.

  15. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, Haijie; Arangio, Andrea M.; Lakey, Pascale S. J.; Berkemeier, Thomas; Liu, Fobang; Kampf, Christopher J.; Brune, William H.; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-02-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is ˜ 0.1 % upon extraction with pure water and increases to ˜ 1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Upon extraction of SOA samples from OH photooxidation of isoprene, we also detected OH yields of around ˜ 0.1 %, which increases upon addition of Fe2+. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical H2O2 Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  16. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, H.; Arangio, A. M.; Lakey, P. S. J.; Berkemeier, T.; Liu, F.; Kampf, C. J.; Pöschl, U.; Shiraiwa, M.

    2015-11-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is ~ 0.1 % upon extraction with pure water and increases to ~ 1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical H2O2 Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  17. Hydroxyl radicals from secondary organic aerosol decomposition in water

    NASA Astrophysics Data System (ADS)

    Tong, Haijie; Arangio, Andrea M.; Lakey, Pascale S. J.; Berkemeier, Thomas; Liu, Fobang; Kampf, Christopher. J.; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-04-01

    We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, and limonene) is ~ 0.1% upon extraction with pure water, and which increases to ~ 1.5% in the presence of iron ions due to Fenton-like reactions. Our findings imply that the chemical reactivity and aging of SOA particles is strongly enhanced upon interaction with water and iron. In cloud droplets under dark conditions, SOA decomposition can compete with the classical hydrogen peroxide Fenton reaction as the source of OH radicals. Also in the human respiratory tract, the inhalation and deposition of SOA particles may lead to a substantial release of OH radicals, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols.

  18. Incompatible Ages for Clearwing Butterflies Based on Alternative Secondary Calibrations.

    PubMed

    Garzón-Orduña, Ivonne J; Silva-Brandão, Karina L; Willmott, Keith R; Freitas, André V L; Brower, Andrew V Z

    2015-09-01

    The recent publication of a time-tree for the plant family Solanaceae (nightshades) provides the opportunity to use independent calibrations to test divergence times previously inferred for the diverse Neotropical butterfly tribe Ithomiini. Ithomiini includes clades that are obligate herbivores of Solanaceae, with some genera feeding on only one genus. We used 8 calibrations extracted from the plant tree in a new relaxed molecular-clock analysis to produce an alternative temporal framework for the diversification of ithomiines. We compared the resulting age estimates to: (i) a time-tree obtained using 7 secondary calibrations from the Nymphalidae tree of Wahlberg et al. (2009), and (ii) Wahlberg et al.'s (2009) original age estimates for the same clades. We found that Bayesian clock estimates were rather sensitive to a variety of analytical parameters, including taxon sampling. Regardless of this sensitivity however, ithomiine divergence times calibrated with the ages of nightshades were always on average half the age of previous estimates. Younger dates for ithomiine clades appear to fit better with factors long suggested to have promoted diversification of the group such as the uplifting of the Andes, in the case of montane genera. Alternatively, if ithomiines are as old as previous estimates suggest, the recent ages inferred for the diversification of Solanaceae seem likely to be seriously underestimated. Our study exemplifies the difficulty of testing hypotheses of divergence times and of choosing between alternative dating scenarios, and shows that age estimates based on seemingly plausible calibrations may be grossly incongruent. PMID:26012872

  19. Organic cathode for a secondary battery

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V. (Inventor); Distefano, Salvador (Inventor); Williams, Roger M. (Inventor); Bankston, Clyde P. (Inventor)

    1989-01-01

    A liquid catholyte for a battery based on liquid metal such as sodium anode and a solid, ceramic separator such as beta alumina (BASE) comprises a mixture of a Group I-III metal salt such as sodium tetrachloroaluminate and a minor amount of an organic carbonitrile depolarizer having at least one adjacent ethylenic band such as 1 to 40 percent by weight of tetracyanoethylene. The tetracyanoethylene forms an adduct with the molten metal salt.

  20. Aqueous phase processing of secondary organic aerosol from isoprene photooxidation

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Monod, A.; Tritscher, T.; Praplan, A. P.; DeCarlo, P. F.; Temime-Roussel, B.; Quivet, E.; Marchand, N.; Dommen, J.; Baltensperger, U.

    2012-07-01

    Transport of reactive air masses into humid and wet areas is highly frequent in the atmosphere, making the study of aqueous phase processing of secondary organic aerosol (SOA) very relevant. We have investigated the aqueous phase processing of SOA generated from gas-phase photooxidation of isoprene using a smog chamber. The SOA collected on filters was extracted by water and subsequently oxidized in the aqueous phase either by H2O2 under dark conditions or by OH radicals in the presence of light, using a photochemical reactor. Online and offline analytical techniques including SMPS, HR-AMS, H-TDMA, TD-API-AMS, were employed for physical and chemical characterization of the chamber SOA and nebulized filter extracts. After aqueous phase processing, the particles were significantly more hygroscopic, and HR-AMS data showed higher signal intensity at m/z 44 and a lower signal intensity at m/z 43, thus showing the impact of aqueous phase processing on SOA aging, in good agreement with a few previous studies. Additional offline measurement techniques (IC-MS, APCI-MS2 and HPLC-APCI-MS) permitted the identification and quantification of sixteen individual chemical compounds before and after aqueous phase processing. Among these compounds, small organic acids (including formic, glyoxylic, glycolic, butyric, oxalic and 2,3-dihydroxymethacrylic acid (i.e. 2-methylglyceric acid)) were detected, and their concentrations significantly increased after aqueous phase processing. In particular, the aqueous phase formation of 2-methylglyceric acid and trihydroxy-3-methylbutanal was correlated with the consumption of 2,3-dihydroxy-2-methyl-propanal, and 2-methylbutane-1,2,3,4-tetrol, respectively, and an aqueous phase mechanism was proposed accordingly. Overall, the aging effect observed here was rather small compared to previous studies, and this limited effect could possibly be explained by the lower liquid phase OH concentrations employed here, and/or the development of oligomers

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

    EPA Science Inventory

    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 chemic...

  2. SAMPLING DURATION DEPENDENCE OF SEMI-CONTINUOUS ORGANIC CARBON MEASUREMENTS ON STEADY STATE SECONDARY ORGANIC AEROSOLS

    EPA Science Inventory

    Semi-continuous organic carbon concentrations were measured through several experiments of statically generated secondary organic aerosol formed by hydrocarbon + NOx irradiations. Repeated, randomized measurements of these steady state aerosols reveal decreases in the observed c...

  3. Summary Statement: Appropriate Medical Care for the Secondary School-Aged Athlete

    PubMed Central

    Almquist, Jon; Valovich McLeod, Tamara C; Cavanna, Angela; Jenkinson, Dave; Lincoln, Andrew E; Loud, Keith; Peterson, Bart C; Portwood, Craig; Reynolds, John; Woods, Thomas S

    2008-01-01

    Objective: To present the recommendations made by the Appropriate Medical Care for Secondary School-Aged Athletes Task Force and to summarize the subsequent monograph developed around 11 consensus points. Data Sources: The MEDLINE, CINAHL, and SportDiscus databases were searched for relevant literature regarding secondary school-aged athletes; health care administration; preparticipation physical examination; facilities; athletic equipment; emergency action planning; environmental conditions; recognition, evaluation, and treatment of injuries; rehabilitation and reconditioning; psychosocial consultation; nutrition; and prevention strategies. Conclusions and Recommendations: Organizations that sponsor athletic programs for secondary school-aged athletes should establish an athletic health care team to ensure that appropriate medical care is provided to all participants. The 11 consensus points provide a framework—one that is supported by the medical literature and case law—for the development of an athletic health care team and for assigning responsibilities to the team, administrators, and staff members of institutions sponsoring secondary school and club-level athletic programs. PMID:18668175

  4. 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...

  5. ORGAN CULTURE OF MID-FACIAL TISSUE AND SECONDARY PALATE

    EPA Science Inventory

    Abstract: Palatal organ culture provides an in vitro model for the study of the formation of the secondary palate, which forms the roof of the mouth in the developing fetus. The protocol describes the steps for culture of the mid-facial region of the fetal mouse or rat. In cult...

  6. EVALUATION OF SECONDARY ORGANIC AEROSOL FORMATION IN WINTER. (R823514)

    EPA Science Inventory

    Three different methods are used to predict secondary organic aerosol (SOA)
    concentrations in the San Joaquin Valley of California during the winter of 1995-1996 [Integrated
    Monitoring Study, (IMS95)]. The first of these methods estimates SOA by using elemental carbon as

  7. Secondary Professional Socialization through Professional Organizations: An Exploratory Study

    ERIC Educational Resources Information Center

    Richards, K. Andrew; Eberline, Andrew D.; Templin, Thomas J.

    2016-01-01

    Secondary professional socialization is a phase of occupational socialization theory that focuses on graduate education in preparation for a career in academia. Due to the need to present and publish research and make professional contacts, professional organizations likely serve an important socializing function during graduate education. The…

  8. The evolution of secondary organization in immune system gene libraries

    SciTech Connect

    Hightower, R.; Forrest, S. . Dept. of Computer Science); Perelson, A.S. )

    1993-01-01

    A binary model of the immune system is used to study the effects of evolution on the genetic encoding for antibody molecules. We report experiments which show that the evolution of immune system genes, simulated by the genetic algorithm, can induce a high degree of genetic organization even though that organization is not explicitly required by the fitness function. This secondary organization is related to the true fitness of an individual, in contrast to the sampled fitness which is the explicit fitness measure used to drive the process of evolution.

  9. The evolution of secondary organization in immune system gene libraries

    SciTech Connect

    Hightower, R.; Forrest, S.; Perelson, A.S.

    1993-02-01

    A binary model of the immune system is used to study the effects of evolution on the genetic encoding for antibody molecules. We report experiments which show that the evolution of immune system genes, simulated by the genetic algorithm, can induce a high degree of genetic organization even though that organization is not explicitly required by the fitness function. This secondary organization is related to the true fitness of an individual, in contrast to the sampled fitness which is the explicit fitness measure used to drive the process of evolution.

  10. A large source of low-volatility secondary organic aerosol.

    PubMed

    Ehn, Mikael; Thornton, Joel A; Kleist, Einhard; Sipilä, Mikko; Junninen, Heikki; Pullinen, Iida; Springer, Monika; Rubach, Florian; Tillmann, Ralf; Lee, Ben; Lopez-Hilfiker, Felipe; Andres, Stefanie; Acir, Ismail-Hakki; Rissanen, Matti; Jokinen, Tuija; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Nieminen, Tuomo; Kurtén, Theo; Nielsen, Lasse B; Jørgensen, Solvejg; Kjaergaard, Henrik G; Canagaratna, Manjula; Maso, Miikka Dal; Berndt, Torsten; Petäjä, Tuukka; Wahner, Andreas; Kerminen, Veli-Matti; Kulmala, Markku; Worsnop, Douglas R; Wildt, Jürgen; Mentel, Thomas F

    2014-02-27

    Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere-aerosol-climate feedback mechanisms, and the air quality and climate effects of biogenic emissions generally. PMID:24572423

  11. A large source of low-volatility secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Ehn, Mikael; Thornton, Joel A.; Kleist, Einhard; Sipilä, Mikko; Junninen, Heikki; Pullinen, Iida; Springer, Monika; Rubach, Florian; Tillmann, Ralf; Lee, Ben; Lopez-Hilfiker, Felipe; Andres, Stefanie; Acir, Ismail-Hakki; Rissanen, Matti; Jokinen, Tuija; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Nieminen, Tuomo; Kurtén, Theo; Nielsen, Lasse B.; Jørgensen, Solvejg; Kjaergaard, Henrik G.; Canagaratna, Manjula; Maso, Miikka Dal; Berndt, Torsten; Petäjä, Tuukka; Wahner, Andreas; Kerminen, Veli-Matti; Kulmala, Markku; Worsnop, Douglas R.; Wildt, Jürgen; Mentel, Thomas F.

    2014-02-01

    Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere-aerosol-climate feedback mechanisms, and the air quality and climate effects of biogenic emissions generally.

  12. Primary to secondary organic aerosol: evolution of organic emissions from mobile combustion sources

    NASA Astrophysics Data System (ADS)

    Presto, A. A.; Gordon, T. D.; Robinson, A. L.

    2013-09-01

    A series of smog chamber experiments were conducted to investigate the transformation of primary organic aerosol (POA) and formation of secondary organic aerosol (SOA) during the photo-oxidation of dilute gasoline and diesel motor vehicle exhaust. In half of the experiments POA was present in the chamber at the onset of photo-oxidation. In these experiments positive matrix factorization (PMF) was used to determine separate POA and SOA factors from aerosol mass spectrometer data. A two-factor solution, with one POA factor and one SOA factor, was sufficient to describe the organic aerosol in all but one experiment. In the other half of the experiments, POA was not present at the onset of photo-oxidation; these experiments are considered "pure SOA" experiments. The POA mass spectrum was similar to the mass spectra of the hydrocarbon-like organic aerosol factor determined from ambient datasets with one exception, a diesel vehicle equipped with a diesel oxidation catalyst. The SOA in all experiments had a constant composition over the course of photo-oxidation, and did not appear to age with continued oxidation. The SOA mass spectra for the various gasoline and diesel vehicles were similar to each other, but markedly different than ambient oxidized organic aerosol factors. Van Krevelen analysis of the POA and SOA factors for gasoline and diesel experiments reveal slopes of -0.68 and -0.43, respectively. This suggests that the oxidation chemistry in these experiments is a combination of carboxylic acid and alcohol/peroxide formation, consistent with ambient oxidation chemistry. These experiments also provide insight to the mixing behavior of the POA and SOA. Analysis of the time series of the POA factor concentration and a basis-set model both indicate that for all but one of the vehicles tested here, the POA and SOA seem to mix and form a single organic aerosol phase.

  13. Organic peroxides gas-particle partitioning and rapid heterogeneous decomposition on secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Li, H.; Chen, Z. M.; Huang, L. B.; Huang, D.

    2015-10-01

    Organic peroxides, important species in the atmosphere, will promote secondary organic aerosols (SOA) aging, affect HOx radicals cycling, and cause adverse health effects. However, the formation, gas-particle partitioning, and evolution of organic peroxides are extremely complicated and still unclear. In this study, we investigate in the laboratory the production and gas-particle partitioning of peroxides from the ozonolysis of α-pinene, which is one of the major biogenic volatile organic compounds in the atmosphere and is an important precursor for SOA at a global scale. We have determined the molar yields of hydrogen peroxide (H2O2), hydroxymethyl hydroperoxide (HMHP), peroxyformic acid (PFA), peroxyacetic acid (PAA) and total peroxides (TPO, including unknown peroxides) and the fraction of peroxides in SOA. Comparing the gas-phase and particle-phase peroxides, we find that gas-particle partitioning coefficients of PFA and PAA are 104 times higher than theoretical prediction, indicating that organic peroxides play a more important role in the SOA formation than expected previously. Here, we give the partitioning coefficients of TPO as (2-3) × 10-4 m3μg-1. Even so, more than 80 % of the peroxides formed in the reaction remain in the gas phase. Water does not affect the total amount of peroxides in either the gas or particle phase, but can change the distribution of gaseous peroxides. About 18 % gaseous peroxides undergo rapid heterogeneous decomposition on SOA particles in the presence of water vapor, resulting in the additional production of H2O2. This process can partially interpret the unexpected high H2O2 yield under wet conditions. Transformation of organic peroxides to H2O2 also saves OH in the atmosphere, helping to improve the understanding of OH cycling.

  14. Organic peroxides' gas-particle partitioning and rapid heterogeneous decomposition on secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Li, Huan; Chen, Zhongming; Huang, Liubin; Huang, Dao

    2016-02-01

    Organic peroxides, important species in the atmosphere, promote secondary organic aerosol (SOA) aging, affect HOx radicals cycling, and cause adverse health effects. However, the formation, gas-particle partitioning, and evolution of organic peroxides are complicated and still unclear. In this study, we investigated in the laboratory the production and gas-particle partitioning of peroxides from the ozonolysis of α-pinene, which is one of the major biogenic volatile organic compounds in the atmosphere and an important precursor for SOA at a global scale. We have determined the molar yields of hydrogen peroxide (H2O2), hydromethyl hydroperoxide (HMHP), peroxyformic acid (PFA), peroxyacetic acid (PAA), and total peroxides (TPOs, including unknown peroxides) and the fraction of peroxides in α-pinene/O3 SOA. Comparing the gas-phase peroxides with the particle-phase peroxides, we find that gas-particle partitioning coefficients of PFA and PAA are 104 times higher than the values from the theoretical prediction, indicating that organic peroxides play a more important role in SOA formation than previously expected. Here, the partitioning coefficients of TPO were determined to be as high as (2-3) × 10-4 m3 µg-1. Even so, more than 80 % of the peroxides formed in the reaction remain in the gas phase. Water changes the distribution of gaseous peroxides, while it does not affect the total amount of peroxides in either the gas or the particle phase. Approx. 18 % of gaseous peroxides undergo rapid heterogeneous decomposition on SOA particles in the presence of water vapor, resulting in the additional production of H2O2. This process can partially explain the unexpectedly high H2O2 yields under wet conditions. Transformation of organic peroxides to H2O2 also preserves OH in the atmosphere, helping to improve the understanding of OH cycling.

  15. Evaluation of secondary organic aerosol formation in winter

    NASA Astrophysics Data System (ADS)

    Strader, Ross; Lurmann, Fred; Pandis, Spyros N.

    Three different methods are used to predict secondary organic aerosol (SOA) concentrations in the San Joaquin Valley of California during the winter of 1995-1996 [Integrated Monitoring Study, (IMS95)]. The first of these methods estimates SOA by using elemental carbon as a tracer of primary organic carbon. The second method relies on a Lagrangian trajectory model that simulates the formation, transport, and deposition of secondary organic aerosol. The model includes a recently developed gas-particle partitioning mechanism. Results from both methods are in good agreement with the chemical speciation of organic aerosol during IMS95 and suggest that most of the OC measured during IMS95 is of primary origin. Under suitable conditions (clear skies, low winds, low mixing heights) as much as 15-20 μg C m -3 of SOA can be produced, mainly due to oxidation of aromatics. The low mixing heights observed during the winter in the area allow accumulation of SOA precursors and the acceleration of SOA formation. Clouds and fog slow down the production of secondary compounds, reducing their concentrations by a factor of two or three from the above maximum levels. In addition, it appears that there is significant diurnal variation of SOA concentration. A strong dependence of SOA concentrations on temperature is observed, along with the existence of an optimal temperature for SOA formation.

  16. Distant Secondary Craters from Lyot Crater, Mars, and Implications for Ages of Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Robbins, S. J.; Hynek, B. M.

    2011-03-01

    We identified thousands of secondary craters in distinct clusters up to 5200 km from their primary crater, Lyot, on Mars. Their properties, relation to Lyot, and broader implications to secondary cratering and planetary ages will be discussed.

  17. Endocidal Regulation of Secondary Metabolites in the Producing Organisms.

    PubMed

    Li, Shiyou; Wang, Ping; Yuan, Wei; Su, Zushang; Bullard, Steven H

    2016-01-01

    Secondary metabolites are defined as organic compounds that are not directly involved in the normal growth, development, and reproduction of an organism. They are widely believed to be responsible for interactions between the producing organism and its environment, with the producer avoiding their toxicities. In our experiments, however, none of the randomly selected 44 species representing different groups of plants and insects can avoid autotoxicity by its endogenous metabolites once made available. We coined the term endocides (endogenous biocides) to describe such metabolites that can poison or inhibit the parent via induced biosynthesis or external applications. Dosage-dependent endocides can selectively induce morphological mutations in the parent organism (e.g., shrubbiness/dwarfism, pleiocotyly, abnormal leaf morphogenesis, disturbed phyllotaxis, fasciated stems, and variegation in plants), inhibit its growth, development, and reproduction and cause death than non-closely related species. The propagule, as well as the organism itself contains or produces adequate endocides to kill itself. PMID:27389069

  18. Endocidal Regulation of Secondary Metabolites in the Producing Organisms

    PubMed Central

    Li, Shiyou; Wang, Ping; Yuan, Wei; Su, Zushang; Bullard, Steven H.

    2016-01-01

    Secondary metabolites are defined as organic compounds that are not directly involved in the normal growth, development, and reproduction of an organism. They are widely believed to be responsible for interactions between the producing organism and its environment, with the producer avoiding their toxicities. In our experiments, however, none of the randomly selected 44 species representing different groups of plants and insects can avoid autotoxicity by its endogenous metabolites once made available. We coined the term endocides (endogenous biocides) to describe such metabolites that can poison or inhibit the parent via induced biosynthesis or external applications. Dosage-dependent endocides can selectively induce morphological mutations in the parent organism (e.g., shrubbiness/dwarfism, pleiocotyly, abnormal leaf morphogenesis, disturbed phyllotaxis, fasciated stems, and variegation in plants), inhibit its growth, development, and reproduction and cause death than non-closely related species. The propagule, as well as the organism itself contains or produces adequate endocides to kill itself. PMID:27389069

  19. Secondary organic aerosol formation from road vehicle emissions

    NASA Astrophysics Data System (ADS)

    Pieber, Simone M.; Platt, Stephen M.; El Haddad, Imad; Zardini, Alessandro A.; Suarez-Bertoa, Ricardo; Slowik, Jay G.; Huang, Ru-Jin; Hellebust, Stig; Temime-Roussel, Brice; Marchand, Nicolas; Drinovec, Luca; Mocnik, Grisa; Baltensperger, Urs; Astorga, Covadogna; Prévôt, André S. H.

    2014-05-01

    Organic aerosol particles (OA) are a major fraction of the submicron particulate matter. OA consists of directly emitted primary (POA) and secondary OA (SOA). SOA is formed in-situ in the atmosphere via the reaction of volatile organic precursors. The partitioning of SOA species depends not only on the exposure to oxidants, but for instance also on temperature, relative humidity (RH), and the absorptive mass chemical composition (presence of inorganics) and concentration. Vehicle exhaust is a known source of POA and likely contributes to SOA formation in urban areas [1;2]. This has recently been estimated by (i) analyzing ambient data from urban areas combined with fuel consumption data [3], (ii) by examining the chemical composition of raw fuels [4], or (iii) smog chamber studies [5, 6]. Contradictory and thus somewhat controversial results in the relative quantity of SOA from diesel vs. gasoline vehicle exhaust were observed. In order to elucidate the impact of variable ambient conditions on the potential SOA formation of vehicle exhaust, and its relation to the emitted gas phase species, we studied SOA formed from the exhaust of passenger cars and trucks as a function of fuel and engine type (gasoline, diesel) at different temperatures (T 22 vs. -7oC) and RH (40 vs. 90%), as well as with different levels of inorganic salt concentrations. The exhaust was sampled at the tailpipe during regulatory driving cycles on chassis dynamometers, diluted (200 - 400x) and introduced into the PSI mobile smog chamber [6], where the emissions were subjected to simulated atmospheric ageing. Particle phase instruments (HR-ToF-AMS, aethalometers, CPC, SMPS) and gas phase instruments (PTR-TOF-MS, CO, CO2, CH4, THC, NH3 and other gases) were used online during the experiments. We found that gasoline emissions, because of cold starts, were generally larger than diesel, especially during cold temperatures driving cycles. Gasoline vehicles also showed the highest SOA formation

  20. The age of astronomy-related organizations

    NASA Astrophysics Data System (ADS)

    Heck, A.

    1999-03-01

    The age of currently active astronomy-related organizations is investigated from comprehensive and up-to-date samples. Results for professional institutions, associations, planetariums, and public observatories are commented, as well as specific distributions for astronomy-related publishers and software producers. Some events had a clear impact on the rate of foundation of astronomy-related organizations, such as World War I and II, the beginning of space exploration and the landing of man on the Moon, but not all of them affected in the same way Western Europe and North America. It is still premature to assess the impact of the end of the Cold War. A category such as the software producers would of course not exist nor prosper without the advent of the computer age and the subsequent electronic networking of the planet. Other aspects are discussed in the paper.

  1. Secondary organic material formed by methylglyoxal in aqueous aerosol mimics

    NASA Astrophysics Data System (ADS)

    Sareen, N.; Schwier, A. N.; Shapiro, E. L.; Mitroo, D.; McNeill, V. F.

    2010-02-01

    We show that methylglyoxal forms light-absorbing secondary organic material in aqueous ammonium sulfate and ammonium nitrate solutions mimicking tropospheric aerosol particles. The kinetics were characterized using UV-Vis spectrophotometry. The results suggest that the bimolecular reaction of methylglyoxal with an ammonium or hydronium ion is the rate-limiting step for the formation of light-absorbing species, with kNH4+II=5×10-6 M-1 min-1 and kH3O+II≤10-3 M-1 min-1. Evidence of aldol condensation products and oligomeric species up to 759 amu was found using chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol-CIMS). Tentative identifications of carbon-nitrogen species and a sulfur-containing compound were also made using Aerosol-CIMS. Aqueous solutions of methylglyoxal, with and without inorganic salts, exhibit significant surface tension depression. These observations add to the growing body of evidence that dicarbonyl compounds may form secondary organic material in the aerosol aqueous phase, and that secondary organic aerosol formation via heterogeneous processes may affect seed aerosol properties.

  2. Formation of halogen-induced secondary organic aerosol (XOA)

    NASA Astrophysics Data System (ADS)

    Kamilli, Katharina; Ofner, Johannes; Zetzsch, Cornelius; Held, Andreas

    2013-04-01

    Reactive halogen species (RHS) are very important due to their potential of stratospheric ozone depletion and surface ozone destruction. RHS seem to interact with precursors of secondary organic aerosol (SOA) similarly to common atmospheric oxidants like OH radicals and ozone. The potential interaction of RHS with preformed SOA has recently been studied (Ofner et al., 2012). Although aerosol formation from reaction of RHS with typical SOA precursors was previously studied (e.g. Cai et al., 2006), no data are available on bromine-induced aerosol formation from organic precursors yet. An aerosol smog-chamber was used to examine the halogen-induced secondary organic aerosol (XOA) formation under atmospheric conditions using simulated sunlight. With a concentration of 10 ppb for the organic precursor, 2 ppb for molecular chlorine, and 10 ppb for molecular bromine, the experimental setup is close to ambient conditions. By combined measurements of the aerosol size distribution, ozone and NOx mixing ratios, as well as the decay of the organic precursor, aerosol yields and aerosol growth rates were determined. The decay of the organic precursor was analyzed by capillary gas chromatography coupled with flame-ionization detection (GC-FID) and the aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS). Additionally, with the decay rate of the precursor and the calculated photolysis rates of molecular halogen species, based on the well-known spectrum of the solar simulator, mechanistic details on the XOA formation pathways can be determined. We observed XOA formation even at very low precursor and RHS concentrations with a diameter mode at 10-20 nm and a number concentration up to 1000000 particles cm-3. While the XOA formation from chlorine is very rapid, the interaction of bromine with the organic precursors is about five times slower. The aerosol yield reached maximum values of 0.01 for the reaction of chlorine with α-pinene and 0.0004 for

  3. Assessment of biogenic secondary organic aerosol in the Himalayas

    NASA Astrophysics Data System (ADS)

    Stone, B. A.; Nguyen, T.; Pradhan, B.; Dangol, P.

    2012-12-01

    Biogenic contributions to secondary organic aerosol (SOA) in the Southeast Asian regional haze were assessed by measurement of particle-phase isoprene, monoterpene, and sesquiterpene photooxidation products in fine particles (PM2.5) at Godavari, Nepal, located in the Himalayas at an elevation of 1600 meters. Organic species were measured in solvent-extracts of filter samples using gas chromatography mass spectrometry (GCMS) and chemical derivatization. Molecular markers for primary aerosol sources—including motor vehicles, biomass burning, and detritus—and SOA tracers were measured. High concentrations of isoprene derivatives, particularly in the late summer months, point to biogenic SOA as a significant source of organic carbon in the Himalayan region. First-generation SOA products from alpha-pinene were detected in all samples, whereas multi-generation products were not, suggesting that monoterpenes were at an early stage of oxidation at Godavari. Biogenic SOA contributions to PM2.5 organic carbon in the 2005 monsoon and post-monsoon season ranged from 2-19% for isoprene, 1-5% for monoterpenes, and 1-4% for sesquiterpenes. Primary and secondary biogenic sources combined accounted for approximately half of observed organic aerosol, suggesting additional aerosol sources and/or precursors are significant in this region.

  4. 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.

  5. 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.

  6. Field Studies for Secondary Organic Aerosol in the Transboundary Air

    NASA Astrophysics Data System (ADS)

    Irei, S.; Takami, A.; Sadanaga, Y.; Nozoe, S.; Hayashi, M.; Hara, K.; Arakaki, T.; Hatakeyama, S.; Miyoshi, T.; Yokouchi, Y.; Bandow, H.

    2014-12-01

    To study formation of secondary organic aerosol (SOA) in the air outflowed from the Chinese continent and its fraction in an urban city located in downwind, we have conducted field studies at two background sites and one urban site in the western Japan: the Cape Hedo Aerosol and Atmospheric Monitoring Station (26.9˚N, 128.3˚E), the Fukue Atmospheric Monitoring Station (32.8˚N, 128.7˚E), and Fukuoka University (33.6˚N, 130.4˚E), respectively. During the studies, stable carbon isotope ratio (δ13C) of low-volatile water-soluble organic carbon (LV-WSOC) was measured in 24 h collected filter samples of total suspended particulate matter. Concentration of fine organic aerosol and the proportion of the signal at m/z 44 (ions from the carboxyl group) in the organic mass spectra (f44) were also measured by Aerodyne aerosol mass spectrometers. Limited to the Fukue site only, mixing ratios of trace gas species, such as aromatic hydrocarbons, NOx, and NOy, were also measured using GC-FID and NOx and NOyanalyzers for estimation of photochemical age (t[OH]). A case study in December 2010 showed that plots of δ13C versus f44 showed systematic variations at Hedo and Fukue. However, their trends were opposite. At Fukue the trend was consistent in the plot of δ13C of LV-WSOC versus t[OH] estimated by the NOx/NOy or the hydrocarbon ratios, indicating influence of SOA. The systematic trends aforementioned qualitatively agreed with a binary mixture model of SOA with background LV-WSOC having the f44 of ~0.06 and the δ13C of -17‰ or higher, implication of some influence of primary emission associated with C4plants. Given that the LV-WSOC at the urban Fukuoka site was a binary mixture, a mass balance for δ13C was constructed below. In the equation, δ13CMix, δ13CLocal, δ13CTrans, and FLocal are δ13C of binary LV-WSOC mixture, δ13C of LV-WSOC from local emission origin, δ13C of LV-WSOC from transboundary pollution origin, and a fraction of LV-WSOC from local emission

  7. Particle Rebound and Phase State of Secondary Organic Material

    NASA Astrophysics Data System (ADS)

    Bateman, A.; Bertram, A. K.; Martin, S. T.

    2014-12-01

    Secondary organic material (SOM) is produced in the atmosphere from the oxidation of volatile organic compounds emitted from anthropogenic and biogenic sources. Aerosol particles, composed in part of SOM, play important roles in climate and air quality by scattering/absorbing radiation and serving as cloud condensation nuclei (CCN). The magnitude of climate-relevant perturbations depends on particle chemical composition, hygroscopic growth, and phase state, among other factors. Herein, the hygroscopic influence on particle rebound and the phase state of particles composed of isoprene, toluene, and α-pinene secondary organic material (SOM) was studied. Particle rebound measurements were obtained from 5 to 95% RH using a three-arm impaction apparatus. The experimentally determined rebound fractions were compared with results from a model of the rebound process that took into account the particle kinetic energy, van der Waals forces, and RH-dependent capillary forces. Comparison of the experimental and modeled indicated particles softened due to water uptake. For low RH values, the model explained the rebound behavior for all studied SOMs. At higher RH values specific to each SOM, however, particle rebound was no longer observed, and the model did not capture this behavior. Calibration experiments using sucrose particles of variable known viscosities showed the transition from non-rebounding to rebounding particles occurred for viscosity values from 100 to 1 Pa s, corresponding to a transition from semisolid to liquid material. The implication of the differing RH-dependent behaviors among the SOMs is that each SOM has a specific and quantitatively different interaction with water. A linear correlation between rebound fraction and hygroscopic growth factor was demonstrated, implying that absorbed water volume is the governing factor of viscosity for the studied classes of SOM. The findings of this study suggest that both the chemical composition and the ambient

  8. 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. PMID:24600999

  9. SECONDARY ORGANIC AEROSOL FORMATION FROM THE IRRADIATION OF SIMULATED AUTOMOBILE EXHAUST

    EPA Science Inventory

    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 (SO...

  10. Photochemical Aging of Organic Aerosols: A Laboratory Study

    NASA Astrophysics Data System (ADS)

    Papanastasiou, Dimitrios K.; Kostenidou, Evangelia; Gkatzelis, Georgios I.; Psichoudaki, Magdalini; Louvaris, Evangelos; Pandis, Spyros N.

    2014-05-01

    Organic aerosols (OA) are either emitted directly (primary OA) or formed (secondary OA) in the atmosphere and consist of an extremely complex mixture of thousands of organic compounds. Although the scientific community has put significant effort, in the past few decades, to understand organic aerosol (OA) formation, evolution and fate in the atmosphere, traditional models often fail to reproduce the ambient OA levels. Secondary organic aerosol (SOA) formed, in traditional laboratory chamber experiments, from the gas phase oxidation of known precursors, such as α-pinene, is semi-volatile and with an O:C ratio of around 0.4. In contrast, OA found in the atmosphere is significantly less volatile, while the O:C ratio often ranges from 0.5 to 1. In conclusion, there is a significant gap of knowledge in our understanding of OA formation and photochemical transformation in the atmosphere. There is increased evidence that homogeneous gas phase aging by OH radicals might be able to explain, at least in part, the significantly higher OA mass loadings observed and also the oxidation state and volatility of OA in the atmosphere. In this study, laboratory chamber experiments were performed to study the role of the continued oxidation of first generation volatile and semi-volatile species by OH radicals in the evolution of the SOA characteristics (mass concentration, volatility, and oxidation state). Ambient air mixtures or freshly formed SOA from α-pinene ozonolysis were used as the source of organic aerosols and semi-volatile species. The initial mixture of organic aerosols and gas phase species (volatile and semi-volatile) was then exposed to atmospheric concentrations of OH radicals to study the aging of aerosols. Experiments were performed with various OH radical sources (H2O2 or HONO) and under various NOx conditions. A suite of instruments was employed to characterize both the gas and the aerosol phase. A Scanning Mobility Particle Sizer (SMPS) and a High

  11. Molecular Markers of Secondary Organic Aerosol in Mumbai, India.

    PubMed

    Fu, Pingqing; Aggarwal, Shankar G; Chen, Jing; Li, Jie; Sun, Yele; Wang, Zifa; Chen, Huansheng; Liao, Hong; Ding, Aijun; Umarji, G S; Patil, R S; Chen, Qi; Kawamura, Kimitaka

    2016-05-01

    Biogenic secondary organic aerosols (SOA) are generally considered to be more abundant in summer than in winter. Here, polar organic marker compounds in urban background aerosols from Mumbai were measured using gas chromatography-mass spectrometry. Surprisingly, we found that concentrations of biogenic SOA tracers at Mumbai were several times lower in summer (8-14 June 2006; wet season; n = 14) than in winter (13-18 February 2007; dry season; n = 10). Although samples from less than 10% of the season are extrapolated to the full season, such seasonality may be explained by the predominance of the southwest summer monsoon, which brings clean marine air masses to Mumbai. While heavy rains are an important contributor to aerosol removal during the monsoon season, meteorological data (relative humidity and T) suggest no heavy rains occurred during our sampling period. However, in winter, high levels of SOA and their day/night differences suggest significant contributions of continental aerosols through long-range transport together with local sources. The winter/summer pattern of SOA loadings was further supported by results from chemical transport models (NAQPMS and GEOS-Chem). Furthermore, our study suggests that monoterpene- and sesquiterpene-derived secondary organic carbon (SOC) were more significant than those of isoprene- and toluene-SOC at Mumbai. PMID:27045808

  12. Primary and Secondary Organic Carbon Downwind of Mexico City

    SciTech Connect

    Yu, Xiao-Ying; Cary, R.; Laulainen, Nels S.

    2009-09-18

    In order to study particulate matter transport and transformation in the Megacity environment, fine particulate carbons were measured simultaneously at two supersites, suburban T1 and rural T2, downwind of Mexico City during the MILAGRO field campaign in March 2006. Organic carbon (OC), element carbon (EC), and total carbon (TC=OC+EC) were determined near real-time by the Sunset semi-continuous field analyzer at both sites. The semi-empirical EC tracer method was used to derive primary organic carbon (POC) and secondary organic carbon (SOC). Diurnal variations of primary and secondary carbons were observed at T1 and T2, which resulted from boundary layer inversion and impacted by local traffic patterns. The majority of organic carbons at T1 and T2 were secondary. The SOC% (SOC%=SOC/TC*100%) at T1 ranged from 1.2 - 100% with an average of 80.7 ± 14.4%. The SOC% at T2 ranged from 12.8 - 100% with an average of 80.1 ± 14.0%. The average EC to PM2.5 percentage (ECPM%=EC/PM2.5*100%)) and OCPM% were 6.0 % and 20.0% over the whole sampling time. The POC to PM percentage (POCPM%) and SOCPM% were 3.7% and 16.3%, respectively. The maximum ECPM% was 21.2%, and the maximum OCPM% was 57.2%. The maximum POCPM% was 12.9%, and the maximum SOC% was 49.7%. The SOC and POC during T1 to T2 transfer favourable meteorological conditions showed similar characteristics, which indicated that transport between the two supersites took place. Strong correlations between EC and carbon monoxide (CO) and odd nitrogens (NO and NOx) were observed at T1. This indicated that EC had proximate sources such as local traffic emissions. The EC/CO ratio derived by linear regression analysis when parameters are in μgC/m3 and μg/m3, respectively, was 0.0045. A strong correlation was also seen between OC and SOC vs. the sum of oxidants such as O3 and NO2 or O3, NO2 and SO2, suggesting the secondary nature of carbons observed at T1.

  13. Primary and secondary organic carbon downwind of Mexico City

    NASA Astrophysics Data System (ADS)

    Yu, X.-Y.; Cary, R. A.; Laulainen, N. S.

    2009-09-01

    In order to study particulate matter transport and transformation in the Megacity environment, fine particulate carbon was measured simultaneously at two supersites, suburban T1 and rural T2, downwind of Mexico City during the MILAGRO field campaign in March 2006. Organic carbon (OC), element carbon (EC), and total carbon (TC=OC+EC) were determined in near real-time using a Sunset semi-continuous OCEC field analyzer. The semi-empirical EC tracer method was used to derive primary organic carbon (POC) and secondary organic carbon (SOC). Diurnal variations of primary and secondary carbon were observed at T1 and T2, which resulted from boundary layer inversion and impacted by local traffic patterns. The majority of organic carbon particles at T1 and T2 were secondary. The SOCTC% (SOC%=SOC/TC×100%) at T1 ranged from 0.5-93.8% with an average of 63.5±17.2%. The SOCTC% at T2 ranged from 9.3-98.1% with an average of 67.4±12.4%. The average EC to PM2.5 percentage (ECPM%=EC/PM2.5×100%) and OCPM% were 6.0% and 20.0% over the whole sampling time at T1. The POC to PM percentage (POCPM%) and SOCPM% were 3.7% and 16.3%, respectively at the same site. The maximum ECPM% was 21.2%, and the maximum OCPM% was 57.2% at T1. The maximum POCPM% was 12.9%, and the maximum SOCPM% was 49.7% at T1. Comparison of SOC and POC at T1 and T2 showed similar characteristics under favorable meteorological conditions, which indicated that transport from T1 towards T2 took place. Strong correlations between EC and carbon monoxide (CO) and odd nitrogen species (NO and NOx) were observed at T1. This indicated that EC had nearby sources, such as local traffic emissions. The EC/CO ratio derived by linear regression analysis, with units of μg C/m3 and μg/m3, respectively, was 0.004 at T1. Correlations were also seen between OC and SOC vs. the sum of oxidants, such as O3 and NO2, suggesting the secondary nature of carbons observed at T1.

  14. Primary and secondary organic carbon downwind of Mexico City

    NASA Astrophysics Data System (ADS)

    Yu, X.-Y.; Cary, R. A.; Laulainen, N. S.

    2009-01-01

    In order to study particulate matter transport and transformation in the Megacity environment, fine particulate carbons were measured simultaneously at two supersites, suburban T1 and rural T2, downwind of Mexico City during the MILAGRO field campaign in March 2006. Organic carbon (OC), element carbon (EC), and total carbon (TC=OC+EC) were determined in near real-time using a Sunset semi-continuous OC/EC field analyzer. The semi-empirical EC tracer method was used to derive primary organic carbon (POC) and secondary organic carbon (SOC). Diurnal variations of primary and secondary carbons were observed at T1 and T2, which resulted from boundary layer inversion and impacted by local traffic patterns. The majority of organic carbon particles at T1 and T2 were secondary. The SOC% (SOC%=SOC/TC×100%) at T1 ranged from 1.2-100% with an average of 80.7±14.4%. The SOC% at T2 ranged from 12.8-100% with an average of 80.1±14.0%. The average EC to PM2.5 percentage (ECPM%=EC/PM2.5×100%) and OCPM% were 6.0% and 20.0% over the whole sampling time at T1. The POC to PM percentage (POCPM%) and SOCPM% were 3.7% and 16.3%, respectively at the same site. The maximum ECPM% was 21.2%, and the maximum OCPM% was 57.2% at T1. The maximum POCPM% was 12.9%, and the maximum SOCPM% was 49.7% at the suburban site. Comparison of SOC and POC at T1 and T2 showed similar characteristics under favorable meteorological conditions, which indicated that transport between the two supersites took place. Strong correlations between EC and carbon monoxide (CO) and odd nitrogen species (NO and NOx) were observed at T1. This indicated that EC had nearby sources, such as local traffic emissions. The EC/CO ratio derived by linear regression analysis, when parameters in μg C/m3 and μg/m3, respectively, was 0.0045 at T1. Correlations were also seen between OC and SOC vs. the sum of oxidants, such as O3 and NO2, suggesting the secondary nature of carbons observed at T1.

  15. Evaporation Kinetics and Phase of Laboratory and Ambient Secondary Organic Aerosol

    SciTech Connect

    Vaden, Timothy D.; Imre, Dan G.; Beranek, Josef; Shrivastava, ManishKumar B.; Zelenyuk, Alla

    2011-02-08

    Field measurements of secondary organic aerosol (SOA) find higher mass loads than predicted by models, sparking intense efforts to find additional SOA sources but leaving the assumption of rapid SOA evaporation unchallenged. We characterized room-temperature evaporation of pure SOA and SOA formed in the presence of spectator organic vapors with and without aging. We find that it takes ~24 hrs for pure SOA particles to evaporate 75% of their mass, which is in sharp contrast to the ~10 minutes timescales predicted by models. The presence of spectator organic vapors and aging dramatically reduces the evaporation, and in some cases nearly stops it. For all cases, SOA evaporation behavior is size independent and does not follow the liquid droplet evaporation kinetics assumed by models.

  16. Nonequilibrium atmospheric secondary organic aerosol formation and growth.

    PubMed

    Perraud, Véronique; Bruns, Emily A; Ezell, Michael J; Johnson, Stanley N; Yu, Yong; Alexander, M Lizabeth; Zelenyuk, Alla; Imre, Dan; Chang, Wayne L; Dabdub, Donald; Pankow, James F; Finlayson-Pitts, Barbara J

    2012-02-21

    Airborne particles play critical roles in air quality, health effects, visibility, and climate. Secondary organic aerosols (SOA) formed from oxidation of organic gases such as α-pinene account for a significant portion of total airborne particle mass. Current atmospheric models typically incorporate the assumption that SOA mass is a liquid into which semivolatile organic compounds undergo instantaneous equilibrium partitioning to grow the particles into the size range important for light scattering and cloud condensation nuclei activity. We report studies of particles from the oxidation of α-pinene by ozone and NO(3) radicals at room temperature. SOA is primarily formed from low-volatility ozonolysis products, with a small contribution from higher volatility organic nitrates from the NO(3) reaction. Contrary to expectations, the particulate nitrate concentration is not consistent with equilibrium partitioning between the gas phase and a liquid particle. Rather the fraction of organic nitrates in the particles is only explained by irreversible, kinetically determined uptake of the nitrates on existing particles, with an uptake coefficient that is 1.6% of that for the ozonolysis products. If the nonequilibrium particle formation and growth observed in this atmospherically important system is a general phenomenon in the atmosphere, aerosol models may need to be reformulated. The reformulation of aerosol models could impact the predicted evolution of SOA in the atmosphere both outdoors and indoors, its role in heterogeneous chemistry, its projected impacts on air quality, visibility, and climate, and hence the development of reliable control strategies. PMID:22308444

  17. Nonequilibrium atmospheric secondary organic aerosol formation and growth

    PubMed Central

    Perraud, Véronique; Bruns, Emily A.; Ezell, Michael J.; Johnson, Stanley N.; Yu, Yong; Alexander, M. Lizabeth; Zelenyuk, Alla; Imre, Dan; Chang, Wayne L.; Dabdub, Donald; Pankow, James F.; Finlayson-Pitts, Barbara J.

    2012-01-01

    Airborne particles play critical roles in air quality, health effects, visibility, and climate. Secondary organic aerosols (SOA) formed from oxidation of organic gases such as α-pinene account for a significant portion of total airborne particle mass. Current atmospheric models typically incorporate the assumption that SOA mass is a liquid into which semivolatile organic compounds undergo instantaneous equilibrium partitioning to grow the particles into the size range important for light scattering and cloud condensation nuclei activity. We report studies of particles from the oxidation of α-pinene by ozone and NO3 radicals at room temperature. SOA is primarily formed from low-volatility ozonolysis products, with a small contribution from higher volatility organic nitrates from the NO3 reaction. Contrary to expectations, the particulate nitrate concentration is not consistent with equilibrium partitioning between the gas phase and a liquid particle. Rather the fraction of organic nitrates in the particles is only explained by irreversible, kinetically determined uptake of the nitrates on existing particles, with an uptake coefficient that is 1.6% of that for the ozonolysis products. If the nonequilibrium particle formation and growth observed in this atmospherically important system is a general phenomenon in the atmosphere, aerosol models may need to be reformulated. The reformulation of aerosol models could impact the predicted evolution of SOA in the atmosphere both outdoors and indoors, its role in heterogeneous chemistry, its projected impacts on air quality, visibility, and climate, and hence the development of reliable control strategies. PMID:22308444

  18. Mechanism for production of secondary organic aerosols and their representation in atmospheric models. Final report

    SciTech Connect

    Seinfeld, J.H.; Flagan, R.C.

    1999-06-07

    This document contains the following: organic aerosol formation from the oxidation of biogenic hydrocarbons; gas/particle partitioning of semivolatile organic compounds to model inorganic, organic, and ambient smog aerosols; and representation of secondary organic aerosol formation in atmospheric models.

  19. Photochemistry of Secondary Organic Aerosol Components in Water and Ice

    NASA Astrophysics Data System (ADS)

    Epstein, S. A.; Tran, V. T.; Lignell, H.; Nizkorodov, S.; Shemesh, D.; Gerber, R.

    2011-12-01

    Secondary organic aerosol (SOA) can nucleate clouds in the atmosphere and may be scavenged by previously formed cloud droplets. Significant concentrations of dissolved organic matter are typically present in cloud droplets, snow, and ice particles, however the photochemical transformations of these organic components in liquid aqueous solutions and in ice are poorly understood. An apparatus was constructed to measure the absorption spectra of frozen aqueous solutions in the presence of ultra-violet (UV) light. We can monitor the disappearance of the original reactant as a function of UV exposure time with UV-Visible spectroscopy and identify products with gas chromatography-mass spectrometry. Initial experiments with methylhydroperoxide, the simplest organic peroxide, which is readily detectable in solid and liquid cloud particles, reveal no change in the absorption spectra between the liquid and frozen solution. With these photolysis experiments, we can establish quantum yields of methylhydroperoxide photodissociation and allow for the comparison between liquid and ice phase chemistry. Additional experiments with pinonic acid, a significant product formed from alpha-pinene ozonolysis, and a mixture of common SOA constituents will allow us to determine quantum yields and reveal important insight in the understanding of the cloud processing of water soluble SOA by sunlight.

  20. Drying-Induced Evaporation of Secondary Organic Aerosol during Summer.

    PubMed

    El-Sayed, Marwa M H; Amenumey, Dziedzorm; Hennigan, Christopher J

    2016-04-01

    This study characterized the effect of drying on the concentration of atmospheric secondary organic aerosol (SOA). Simultaneous measurements of water-soluble organic carbon in the gas (WSOCg) and particle (WSOCp) phases were carried out in Baltimore, MD during the summertime. To investigate the effect of drying on SOA, the WSOCp measurement was alternated through an ambient channel (WSOCp) and a "dried" channel (WSOCp,dry) maintained at ∼35% relative humidity (RH). The average mass ratio between WSOCp,dry and WSOCp was 0.85, showing that significant evaporation of the organic aerosol occurred due to drying. The average amount of evaporated water-soluble organic matter (WSOM = WSOC × 1.95) was 0.6 μg m(-3); however, the maximum evaporated WSOM concentration exceeded 5 μg m(-3), demonstrating the importance of this phenomenon. The systematic difference between ambient and dry channels indicates a significant and persistent source of aqueous SOA formed through reversible uptake processes. The wide-ranging implications of the work are discussed, and include: new insight into atmospheric SOA formation; impacts on particle measurement techniques; a newly identified bias in PM2.5 measurements using the EPA's Federal Reference and Equivalent Methods (FRM and FEM); atmospheric model evaluations; and the challenge in relating ground-based measurements to remote sensing of aerosol properties. PMID:26910726

  1. 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.

  2. Primary and secondary control over age-related changes in physical appearance.

    PubMed

    Thompson, S C; Thomas, C; Rickabaugh, C A; Tantamjarik, P; Otsuki, T; Pan, D; Garcia, B F; Sinar, E

    1998-08-01

    Beliefs about appearance-related changes due to aging were used to test the effects of perceived control and secondary control (acceptance) in a sample of 412 young, early-middle-age, and late-middle-age college-educated adults. Mean difference in aging-related appearance control and hypotheses regarding the adaptiveness of primary and secondary control were examined. Primary control over aging-related appearance was lower in older adults and secondary control was higher. In addition, the results indicated support for the Primacy/Back-Up Model that primary perceived control is important at all levels of actual control. Those with stronger beliefs in their primary control were less distressed. Secondary control served a back-up function in that it was related to less distress only for those who had medium or lower beliefs in primary control. The implications of these findings, that primary control may be advantageous even in low-control circumstances, are discussed. PMID:9728417

  3. The Radiative Forcing from Biogenic Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Scott, C. E.; Forster, P.; Spracklen, D. V.; Carslaw, K. S.; Arnold, S.; Rap, A.

    2012-12-01

    Vegetation emits biogenic volatile organic compounds (BVOCs), such as monoterpenes, isoprene and sesquiterpenes, into the atmosphere. Once emitted, BVOCs rapidly undergo reactions with the hydroxyl radical, ozone and the nitrate radical to yield a range of lower volatility oxidation products. These compounds are of sufficiently low volatility to partition into the aerosol phase, forming secondary organic aerosol (SOA). Increasingly, there are indications that organic compounds, specifically the oxidation products of terpenes, may contribute to the process of new particle formation as well as the growth of existing particles. The formation of SOA can influence the Earth's radiative balance by absorbing and scattering radiation (the direct effect) and by altering the properties of clouds (the indirect effect), via their action as cloud condensation nuclei (CCN). Biogenic SOA formed from the oxidation products of isoprene and monoterpenes has been shown to be CCN active under atmospherically relevant conditions, indicating that complex climate feedbacks may result from the emission of BVOCs. Using a global aerosol microphysics model (GLOMAP), and offline radiative transfer code, we simulate a present day aerosol indirect radiative forcing of between -0.07 and - 0.81 W.m-2, for the emission of BVOCs, due to a simulated increase in the number of particles able to act as CCN. The forcing obtained per emission is not spatially uniform, with monoterpenes in the southern hemisphere being most efficient at inducing a radiative change. We find a strong sensitivity to the treatment of concurrent anthropogenic emissions. In the present day, biogenic secondary organic material is more efficient at perturbing CCN number concentrations, but when anthropogenic emissions from 1750 are included in our simulations, the lower background aerosol concentration results in a more significant radiative response. The largest uncertainty in the forcing obtained however, comes from the

  4. A Study of Elementary and Secondary Teacher Knowledge and Attitudes toward Aging and the Implementation of Aging Education in Taiwan

    ERIC Educational Resources Information Center

    Huang, Chin-Shan

    2012-01-01

    This study surveys elementary and secondary teachers in Taiwan and compares the findings with other studies conducted in America and Japan. The objective is to explore differences among teachers in Taiwan, Japan, and the United States in terms of their knowledge of, and attitudes toward, aging and the implementation of aging education in schools.…

  5. Secondary organic aerosol: a comparison between foggy and nonfoggy days.

    PubMed

    Kaul, D S; Gupta, Tarun; Tripathi, S N; Tare, V; Collett, J L

    2011-09-01

    Carbonaceous species, meteorological parameters, trace gases, and fogwater chemistry were measured during winter in the Indian city of Kanpur to study secondary organic aerosol (SOA) during foggy and clear (nonfoggy) days. Enhanced SOA production was observed during fog episodes. It is hypothesized that aqueous phase chemistry in fog drops is responsible for increasing SOA production. SOA concentrations on foggy days exceeded those on clear days at all times of day; peak foggy day SOA concentrations were observed in the evening vs peak clear day SOA concentrations which occurred in the afternoon. Changes in biomass burning emissions on foggy days were examined because of their potential to confound estimates of SOA production based on analysis of organic to elemental carbon (OC/EC) ratios. No evidence of biomass burning influence on SOA during foggy days was found. Enhanced oxidation of SO(2) to sulfate during foggy days was observed, possibly causing the regional aerosol to become more acidic. No evidence was found in this study, either, for effects of temperature or relative humidity on SOA production. In addition to SOA production, fogs can also play an important role in cleaning the atmosphere of carbonaceous aerosols. Preferential scavenging of water-soluble organic carbon (WSOC) by fog droplets was observed. OC was found to be enriched in smaller droplets, limiting the rate of OC deposition by droplet sedimentation. Lower EC concentrations were observed on foggy days, despite greater stagnation and lower mixing heights, suggesting fog scavenging and removal of EC was active as well. PMID:21790145

  6. Nonequilibrium Atmospheric Secondary Organic Aerosol Formation and Growth

    SciTech Connect

    Perraud, Veronique M.; Bruns, Emily A.; Ezell, Michael J.; Johnson, Stanley N.; Yu, Yong; Alexander, M. L.; Zelenyuk, Alla; Imre, D.; Chang, W. L.; Dabdub, Donald; Pankow, James F.; Finlayson-Pitts, Barbara J.

    2012-02-21

    Airborne particles play a critical role in air quality, human health effects, visibility and climate. Secondary organic aerosols (SOA) account for a significant portion of total airborne particles. They are formed in reactions of organic gases that produce low volatility and semi-volatile organic compounds (SVOCs). Current atmospheric models assume that SOA are liquids into which SVOCs undergo equilibrium partitioning and grow the particles. However a large discrepancy between model predictions and field measurements of SOA is commonly observed. We report here laboratory studies of the oxidation of a-pinene by ozone and nitrate radicals and show that particle composition is actually consistent with a kinetically determined growth mechanism, and not with equilibrium partitioning between the gas phase and liquid particles. If this is indeed a general phenomenon in air, the formulation of atmospheric SOA models will have to be revised to reflect this new paradigm. This will have significant impacts on quantifying the role of SOA in air quality, visibility, and climate.

  7. Social Studies Classroom Activities for Secondary Schools. Schools in an Aging Society.

    ERIC Educational Resources Information Center

    Goranson, Donald G., Ed.

    Designed for secondary students, the 20 lessons in this volume promote education for, with, and about older adults and prepare students to participate in the changing world. Lessons 1-3 explore attitudes about aging through word association, confront the aging process, and examine values regarding time. Lessons 4-6 study aging in different times…

  8. Predicting secondary organic aerosol formation rates in southeast Texas

    NASA Astrophysics Data System (ADS)

    Russell, Matthew; Allen, David T.

    2005-04-01

    Rates of secondary organic aerosol (SOA) formation, due to the reactions of aromatics and monoterpenes, were estimated for southeast Texas by incorporating a modified version of the Statewide Air Pollution Research Center's chemical mechanism (SAPRC99) into the Comprehensive Air Quality Model with extensions (CAMx version 3.10). The model included explicit representation of the reactions of five SOA precursors (α-pinene, β-pinene, sabinene, d-limonene, and Δ3-carene). Reactions of each SOA precursor with O3, OH radical, and NO3 radical were included. The model also included separate reactions for low- and high-SOA-yield aromatic groups with the OH radical. SOA yields in the mechanisms were estimated using compound-specific yield information (ΔSOA/ΔHC) derived from smog chamber experiments conducted by J. R. Odum and colleagues and R. J. Griffin and colleagues. The form of the SOA yield model was based on the work of J. R. Odum and colleagues and is a function of existing organic aerosol concentrations. Existing organic aerosol concentrations were estimated on the basis of ambient measurements of total organic carbon in southeast Texas. The reactions of monoterpenes (predominantly α-pinene and β-pinene) with ozone led to the most regional SOA formation, followed by monoterpenes with the nitrate radical. Aromatic-OH reactions led to less regional SOA formation compared to monoterpenes; however, this formation occurs close to the urban and industrial areas of Houston. In contrast, SOA formation due to the reactions of monoterpenes occurred in the forested areas north of the urban area. The results of this study are in qualitative agreement with estimates of SOA formation based on ambient data from the same time period.

  9. Age-Specificity of Clinical Dengue during Primary and Secondary Infections

    PubMed Central

    Thai, Khoa T. D.; Nishiura, Hiroshi; Hoang, Phuong Lan; Tran, Nga Thanh Thi; Phan, Giao Trong; Le, Hung Quoc; Tran, Binh Quang; Nguyen, Nam Van; de Vries, Peter J.

    2011-01-01

    Background This study aims to estimate the age-specific risks of clinical dengue attack (i.e., the risk of symptomatic dengue among the total number of dengue virus (DENV) infections) during primary and secondary infections. Methods We analyzed two pieces of epidemiological information in Binh Thuan province, southern Vietnam, i.e., age-specific seroprevalence and a community-wide longitudinal study of clinical dengue attack. The latter data set stratified febrile patients with DENV infection by age as well as infection parity. A simple modeling approach was employed to estimate the age-specific risks of clinical dengue attack during primary and secondary infections. Results Using the seroprevalence data, the force of infection was estimated to be 11.7% (95% confidence intervals (CI): 10.8–12.7) per year. Median age (and the 25–75 percentiles) of dengue fever patients during primary and secondary infections were 12 (9–20) and 20 (14–31) years, respectively. The estimated age-specific risk of clinical dengue increases as a function of age for both primary and secondary infections; the estimated proportion of symptomatic patients among the total number of infected individuals was estimated to be <7% for those aged <10 years for both primary and secondary infections, but increased as patients become older, reaching to 8–11% by the age of 20 years. Conclusions/Significance For both primary and secondary infections, higher age at DENV infection was shown to result in higher risk of clinical attack. Age as an important modulator of clinical dengue explains recent increase in dengue notifications in ageing countries in Southeast Asia, and moreover, poses a paradoxical problem of an increase in adult patients resulting from a decline in the force of infection, which may be caused by various factors including time-dependent variations in epidemiological, ecological and demographic dynamics. PMID:21713018

  10. Nitrated Secondary Organic Tracer Compounds in Biomass Burning Smoke

    NASA Astrophysics Data System (ADS)

    Iinuma, Y.; Böge, O.; Gräfe, R.; Herrmann, H.

    2010-12-01

    Natural and human-initiated biomass burning releases large amounts of gases and particles into the atmosphere, impacting climate, environment and affecting public health. Several hundreds of compounds are emitted from biomass burning and these compounds largely originate from the pyrolysis of biopolymers such as lignin, cellulose and hemicellulose. Some of compounds are known to be specific to biomass burning and widely recognized as tracer compounds that can be used to identify the presence of biomass burning PM. Detailed chemical analysis of biomass burning influenced PM samples often reveals the presence compounds that correlated well with levoglucosan, a known biomass burning tracer compound. In particular, nitrated aromatic compounds correlated very well with levoglucosan, indicating that biomass burning as a source for this class of compounds. In the present study, we present evidence for the presence of biomass burning originating secondary organic aerosol (BSOA) compounds in biomass burning influenced ambient PM. These BSOA compounds are typically nitrated aromatic compounds that are produced in the oxidation of precursor compounds in the presence of NOx. The precursor identification was performed from a series of aerosol chamber experiments. m-Cresol, which is emitted from biomass burning at significant levels, is found to be a major precursor compounds for nitrated BSOA compounds found in the ambient PM. We estimate that the total concentrations of these compounds in the ambient PM are comparable to biogenic SOA compounds in winter months, indicating the BSOA contributes important amounts to the regional organic aerosol loading.

  11. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Madronich, S.; Kasibhatla, P. S.; Tyndall, G.; Aumont, B.; Jimenez, J. L.; Lee-Taylor, J.; Orlando, J.

    2015-08-01

    This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOAs). Typically only photolysis of smaller organic molecules (e.g., formaldehyde) for which explicit data exist is included in chemistry-climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemical mechanism generator GECKO-A is used to explicitly model SOA formation from α-pinene, toluene, and C12 and C16 n-alkane reactions with OH at low and high NOx. Simulations are conducted for typical mid-latitude conditions and a solar zenith angle of 45° (permanent daylight). The results show that after 4 days of chemical aging under those conditions (equivalent to 8 days in the summer mid-latitudes), gas-phase photolysis leads to a moderate decrease in SOA yields, i.e., ~15 % (low NOx) to ~45 % (high NOx) for α-pinene, ~15 % for toluene, ~25 % for C12 n-alkane, and ~10 % for C16 n-alkane. The small effect of gas-phase photolysis on low-volatility n-alkanes such as C16 n-alkane is due to the rapid partitioning of early-generation products to the particle phase, where they are protected from gas-phase photolysis. Minor changes are found in the volatility distribution of organic products and in oxygen to carbon ratios. The decrease in SOA mass is increasingly more important after a day of chemical processing, suggesting that most laboratory experiments are likely too short to quantify the effect of gas-phase photolysis on SOA yields. Our results also suggest that many molecules containing chromophores are preferentially partitioned into the particle phase before they can be photolyzed in the gas phase. Given the growing experimental evidence that these molecules can undergo in-particle photolysis, we performed sensitivity simulations using an empirically estimated SOA photolysis rate of JSOA

  12. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Madronich, S.; Kasibhatla, P. S.; Tyndall, G.; Aumont, B.; Jimenez, J. L.; Lee-Taylor, J.; Orlando, J.

    2015-03-01

    This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOA). Typically only photolysis of smaller organic molecules (e.g. formaldehyde) for which explicit data exist is included in chemistry-climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemical mechanism generator GECKO-A is used to explicitly model SOA formation from α-pinene, toluene, and C12 and C16 n-alkane reactions with OH at low- and high-NOx. Simulations are conducted for typical mid-latitude conditions and a solar zenith angle of 45° (permanent daylight). The results show that after four days of chemical aging under those conditions (equivalent to eight days in the summer mid-latitudes), gas-phase photolysis leads to a moderate decrease in SOA yields i.e ~15% (low-NOx) to ~45% (high-NOx) for α-pinene, ~15% for toluene, ~25% for C12-alkane, and ~10% for C16-alkane. The small effect on low volatility n-alkanes such as C16-alkane is due to the rapid partitioning of early-generation products to the particle phase where they are assumed to be protected from gas-phase photolysis. Minor changes are found in the volatility distribution of organic products and in oxygen to carbon ratios. The decrease in SOA mass seems increasingly more important after a day of chemical processing, suggesting that most laboratory experiments are likely too short to quantify the effect of gas-phase photolysis on SOA yields. Our results also suggest that many molecules containing chromophores are preferentially partitioned into the particle phase before they can be photolyzed in the gas-phase. Given the growing experimental evidence that these molecules can undergo in-particle photolysis, we performed sensitivity simulations using an estimated SOA photolysis rate of JSOA=4 x 10-4JNO2. Modeling

  13. 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.

  14. 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.

  15. 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

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

    PubMed

    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

  17. Aging changes in organs - tissue - cells

    MedlinePlus

    ... and tear on the body, or byproducts of metabolism . Other theories view aging as a predetermined process controlled by genes. No single process can explain all the changes of aging. Aging is a complex process that varies as to how it affects ...

  18. The Nuclear Age: A Curriculum Guide for Secondary Schools.

    ERIC Educational Resources Information Center

    Ground Zero, Washington, DC.

    Intended as a starting point for junior and senior high school teachers, this guide contains five lessons that give an overview of the nuclear age and provide the most basic information that students must learn in order to understand the threat of nuclear war. Topics of the lessons include the history of weapons development, how nuclear weapons…

  19. 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,...

  20. Small molecules as tracers in atmospheric secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Yu, Ge

    Secondary organic aerosol (SOA), formed from in-air oxidation of volatile organic compounds, greatly affects human health and climate. Although substantial research has been devoted to SOA formation and evolution, the modeled and lab-generated SOA are still low in mass and degree of oxidation compared to ambient measurements. In order to compensate for these discrepancies, the aqueous processing pathway has been brought to attention. The atmospheric waters serve as aqueous reaction media for dissolved organics to undergo further oxidation, oligomerization, or other functionalization reactions, which decreases the vapor pressure while increasing the oxidation state of carbon atoms. Field evidence for aqueous processing requires the identification of tracer products such as organosulfates. We synthesized the standards for two organosulfates, glycolic acid sulfate and lactic acid sulfate, in order to measure their aerosol-state concentration from five distinct locations via filter samples. The water-extracted filter samples were analyzed by LC-MS. Lactic acid sulfate and glycolic acid sulfate were detected in urban locations in the United States, Mexico City, and Pakistan with varied concentrations, indicating their potential as tracers. We studied the aqueous processing reaction between glyoxal and nitrogen-containing species such as ammonium and amines exclusively by NMR spectrometry. The reaction products formic acid and several imidazoles along with the quantified kinetics were reported. The brown carbon generated from these reactions were quantified optically by UV-Vis spectroscopy. The organic-phase reaction between oxygen molecule and alkenes photosensitized by alpha-dicarbonyls were studied in the same manner. We observed the fast kinetics transferring alkenes to epoxides under simulated sunlight. Statistical estimations indicate a very effective conversion of aerosol-phase alkenes to epoxides, potentially forming organosulfates in a deliquescence event and

  1. Photolytic processing of secondary organic aerosols dissolved in cloud droplets

    SciTech Connect

    Bateman, Adam P; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2011-05-26

    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 hours. 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 reduced by photolysis relative to the monomeric compounds. Direct pH measurements showed that compounds containing carboxylic acids increased upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonylswas 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 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.

  2. 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. PMID:20944744

  3. Single Parents, Working Mothers and the Educational Achievement of Secondary School Age Children.

    ERIC Educational Resources Information Center

    Myers, David E.; And Others

    This paper presents a replication of previous research which estimated a structural equation model relating elementary school age students' achievement to the number of parents and maternal work. The research presented here focuses on secondary school age students, and provides partial support for previous findings in which elementary school age…

  4. Calculating Equilibrium Phase Distribution during the Formation of Secondary Organic Aerosol Using COSMOtherm.

    PubMed

    Wang, Chen; Goss, Kai-Uwe; Lei, Ying Duan; Abbatt, Jonathan P D; Wania, Frank

    2015-07-21

    Challenges in the parametrization of compound distribution between the gas and particle phase contribute significantly to the uncertainty in the prediction of secondary organic aerosol (SOA) formation and are rooted in the complexity and variability of atmospheric condensed matter, which includes water, salts, and a multitude of organic oxidation products, often in two separated phases. Here, we explore the use of the commercial quantum-chemistry-based software COSMOtherm to predict equilibrium partitioning and Setchenow coefficients of a suite of oxidation products of α-pinene ozonolysis in an aerosol that is assumed to separate into an organic-enriched phase and an electrolyte-enriched aqueous phase. The predicted coefficients are used to estimate the phase distribution of the organic compounds, water and ammonium sulfate, the resulting phase composition, and the SOA yield. Four scenarios that differ in terms of organic loading, liquid water content, and chemical aging are compared. The organic compounds partition preferentially to the organic phase rather than the aqueous phase for the studied aerosol scenarios, partially due to the salting-out effect. Extremely low volatile organic compounds are predicted to be the dominant species in the organic aerosols at low loadings and an important component at higher loadings. The highest concentration of oxidation products in the condensed phase is predicted for a scenario assuming the presence of non-phase-separated cloud droplets. Partitioning into an organic aerosol phase composed of the oxidation products is predicted to be similar to partitioning into a phase composed of a single organic surrogate molecule, suggesting that the calculation procedure can be simplified without major loss of accuracy. COSMOtherm is shown to produce results that are comparable to those obtained using group contribution methods. COSMOtherm is likely to have a much larger application domain than those group contribution methods because

  5. 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

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

    PubMed

    Ziemann, Paul J; Atkinson, Roger

    2012-10-01

    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

  7. Formation of secondary organic aerosol from isoprene oxidation over Europe

    NASA Astrophysics Data System (ADS)

    Karl, M.; Tsigaridis, K.; Vignati, E.; Dentener, F.

    2009-01-01

    The role of isoprene as a precursor to secondary organic aerosol (SOA) over Europe is studied with the two-way nested global chemistry transport model TM5. The inclusion of the formation of SOA from isoprene oxidation in our model almost doubles the atmospheric burden of SOA over Europe compared to SOA formation from terpenes and aromatics. The reference simulation, which considers SOA formation from isoprene, terpenes and aromatics, predicts a yearly European production rate of 1.0 Tg SOA yr-1 and an annual averaged atmospheric burden of about 50 Gg SOA over Europe. A fraction of 35% of the SOA produced in the boundary layer over Europe is transported to higher altitudes or to other world regions. Summertime measurements of particulate organic matter (POM) during the extensive EMEP OC/EC campaign 2002/2003 are better reproduced when SOA formation from isoprene is taken into account, reflecting also the strong seasonality of isoprene and other biogenic volatile organic compounds (BVOC) emissions from vegetation. However, during winter, our model strongly underestimates POM, likely caused by missing wood burning in the emission inventories. Uncertainties in the parameterisation of isoprene SOA formation have been investigated. Maximum SOA production is found for irreversible sticking (non-equilibrium partitioning) of condensable vapours on particles, with tropospheric SOA production over Europe increased by a factor of 4 in summer compared to the reference case. Completely neglecting SOA formation from isoprene results in the lowest estimate (0.51 Tg SOA yr-1). The amount and the nature of the absorbing matter are shown to be another key uncertainty when predicting SOA levels. Tropospheric isoprene SOA production over Europe in summer more than doubles when, in addition to pre-existing carbonaceous aerosols, condensation of semi volatile vapours on ammonium and sulphate aerosols is considered. Consequently, smog chamber experiments on SOA formation should be

  8. Formation of secondary organic aerosol from isoprene oxidation over Europe

    NASA Astrophysics Data System (ADS)

    Karl, M.; Tsigaridis, K.; Vignati, E.; Dentener, F.

    2009-09-01

    The role of isoprene as a precursor to secondary organic aerosol (SOA) over Europe is studied with the two-way nested global chemistry transport model TM5. The inclusion of the formation of SOA from isoprene oxidation in our model almost doubles the atmospheric burden of SOA over Europe compared to SOA formation from terpenes and aromatics. The reference simulation, which considers SOA formation from isoprene, terpenes and aromatics, predicts a yearly European production rate of 1.0 Tg SOA yr-1 and an annual averaged atmospheric burden of about 50 Gg SOA over Europe. A fraction of 35% of the SOA produced in the boundary layer over Europe is transported to higher altitudes or to other world regions. Summertime measurements of organic matter (OM) during the extensive EMEP OC/EC campaign 2002/2003 are better reproduced when SOA formation from isoprene is taken into account, reflecting also the strong seasonality of isoprene and other biogenic volatile organic compounds (BVOC) emissions from vegetation. However, during winter, our model strongly underestimates OM, likely caused by missing wood burning in the emission inventories. Uncertainties in the parameterisation of isoprene SOA formation have been investigated. Maximum SOA production is found for irreversible sticking (non-equilibrium partitioning) of condensable vapours on particles, with tropospheric SOA production over Europe increased by a factor of 4 in summer compared to the reference case. Completely neglecting SOA formation from isoprene results in the lowest estimate (0.51 Tg SOA yr-1). The amount and the nature of the absorbing matter are shown to be another key uncertainty when predicting SOA levels. Consequently, smog chamber experiments on SOA formation should be performed with different types of seed aerosols and without seed aerosols in order to derive an improved treatment of the absorption of SOA in the models. Consideration of a number of recent insights in isoprene SOA formation mechanisms

  9. Primary and secondary organic aerosols in urban air masses intercepted at a rural site

    NASA Astrophysics Data System (ADS)

    Liggio, John; Li, Shao-Meng; Vlasenko, Alexander; Sjostedt, Steve; Chang, Rachel; Shantz, Nicole; Abbatt, Jonathan; Slowik, J. G.; Bottenheim, J. W.; Brickell, P. C.; Stroud, C.; Leaitch, W. Richard

    2010-11-01

    Measurements made at a rural site in central Ontario during May-June 2007 are used to investigate the composition of organic aerosol (OA) downwind of an urban region. Observations of aerosol organic carbon and oxygen containing fragments from a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) are combined with toluene to benzene ratios to estimate the relative importance of secondary organic aerosol (SOA) and primary organic aerosol (POA) to the total OA at the site during periods of significant urban influence. We estimate that SOA formed within 1-2 days of the anthropogenic source regions was 40-50% of the measured OA and that POA was 5-16% of the OA. The remaining 35-45% of the OA is assumed to have been present in the aerosol upwind of the source regions prior to entering the study domain as defined by trajectories and estimates of the potential photochemical aging time. The apportionment results were also compared to that of positive matrix factorization analysis. In addition, the measurements of the molar oxygen to carbon ratio (O/C) in the OA demonstrates that SOA becomes progressively more oxygenated with increasing photochemical age and at low total OA mass.

  10. Evaluation of the ability of the EC tracer method to estimate secondary organic carbon

    NASA Astrophysics Data System (ADS)

    Day, Melissa C.; Zhang, Minghui; Pandis, Spyros N.

    2015-07-01

    The elemental carbon (EC) tracer method has often been used to estimate the primary and secondary organic aerosol (OA) fractions using field measurements of organic carbon (OC) and EC. In this observation-based approach, EC is used as a tracer for primary OC (POC), which allows for the estimation of secondary OC (SOC). The accuracy of this approach is evaluated using concentrations generated by PMCAMx, a three-dimensional chemical transport model that simulates the complex processes leading to SOC formation (including evaporation and chemical processing of POC and chemical aging of semivolatile and intermediate volatility organics). The ratio of primary organic to elemental carbon [OC/EC]p is estimated in various locations in the Eastern United States, and is then used to calculate the primary and secondary OC concentrations. To estimate the [OC/EC]p from simulated concentrations, we use both a traditional approach and the high EC edge method, in which only values with the highest EC/OC ratio are used. Both methods perform best on a daily-averaged basis, because of the variability of the [OC/EC]p ratio during the day. The SOC estimated by the EC tracer methods corresponds to the biogenic and anthropogenic SOC formed during the oxidation of volatile organic compounds. On the other hand, the estimated POC corresponds to the sum of the fresh POC, the SOC from oxidation of the evaporated POC and the intermediate volatility organic compounds, and the OC from long-distance transport. With this correspondence, the traditional EC tracer method tends to overpredict primary OC and underpredict secondary OC for the selected urban areas in the eastern United States. The high EC edge method performs better, especially in areas where the primary contribution to OC is smaller. Despite the weaknesses of models like the one used here, the conclusions about the accuracy of observation-based methods like the EC-tracer approach should be relatively robust due to the internal

  11. Elucidating secondary organic aerosol from diesel and gasoline vehicles through detailed characterization of organic carbon emissions

    PubMed Central

    Gentner, Drew R.; Isaacman, Gabriel; Worton, David R.; Chan, Arthur W. H.; Dallmann, Timothy R.; Davis, Laura; Liu, Shang; Day, Douglas A.; Russell, Lynn M.; Wilson, Kevin R.; Weber, Robin; Guha, Abhinav; Harley, Robert A.; Goldstein, Allen H.

    2012-01-01

    Emissions from gasoline and diesel vehicles are predominant anthropogenic sources of reactive gas-phase organic carbon and key precursors to secondary organic aerosol (SOA) in urban areas. Their relative importance for aerosol formation is a controversial issue with implications for air quality control policy and public health. We characterize the chemical composition, mass distribution, and organic aerosol formation potential of emissions from gasoline and diesel vehicles, and find diesel exhaust is seven times more efficient at forming aerosol than gasoline exhaust. However, both sources are important for air quality; depending on a region’s fuel use, diesel is responsible for 65% to 90% of vehicular-derived SOA, with substantial contributions from aromatic and aliphatic hydrocarbons. Including these insights on source characterization and SOA formation will improve regional pollution control policies, fuel regulations, and methodologies for future measurement, laboratory, and modeling studies. PMID:23091031

  12. Secondary organic aerosol formation from biomass burning intermediates: phenol and methoxyphenols

    NASA Astrophysics Data System (ADS)

    Yee, L. D.; Kautzman, K. E.; Loza, C. L.; Schilling, K. A.; Coggon, M. M.; Chhabra, P. S.; Chan, M. N.; Chan, A. W. H.; Hersey, S. P.; Crounse, J. D.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H.

    2013-02-01

    The formation of secondary organic aerosol from oxidation of phenol, guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol), major components of biomass burning, is described. Photooxidation experiments were conducted in the Caltech laboratory chambers under low-NOx (<10 ppb) conditions using H2O2 as the OH source. Secondary organic aerosol (SOA) yields (ratio of mass of SOA formed to mass of primary organic reacted) greater than 25% are observed. Aerosol growth is rapid and linear with the primary organic conversion, consistent with the formation of essentially non-volatile products. Gas- and aerosol-phase oxidation products from the guaiacol system provide insight into the chemical mechanisms responsible for SOA formation. Syringol SOA yields are lower than those of phenol and guaiacol, likely due to novel methoxy group chemistry that leads to early fragmentation in the gas-phase photooxidation. Atomic oxygen to carbon (O:C) ratios calculated from high-resolution-time-of-flight Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS) measurements of the SOA in all three systems are ~0.9, which represent among the highest such ratios achieved in laboratory chamber experiments and are similar to that of aged atmospheric organic aerosol. The global contribution of SOA from intermediate volatility and semivolatile organic compounds has been shown to be substantial (Pye and Seinfeld, 2010). An approach to representing SOA formation from biomass burning emissions in atmospheric models could involve one or more surrogate species for which aerosol formation under well-controlled conditions has been quantified. The present work provides data for such an approach.

  13. Secondary organic aerosol formation from biomass burning intermediates: phenol and methoxyphenols

    NASA Astrophysics Data System (ADS)

    Yee, L. D.; Kautzman, K. E.; Loza, C. L.; Schilling, K. A.; Coggon, M. M.; Chhabra, P. S.; Chan, M. N.; Chan, A. W. H.; Hersey, S. P.; Crounse, J. D.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J. H.

    2013-08-01

    The formation of secondary organic aerosol from oxidation of phenol, guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol), major components of biomass burning, is described. Photooxidation experiments were conducted in the Caltech laboratory chambers under low-NOx (< 10 ppb) conditions using H2O2 as the OH source. Secondary organic aerosol (SOA) yields (ratio of mass of SOA formed to mass of primary organic reacted) greater than 25% are observed. Aerosol growth is rapid and linear with the primary organic conversion, consistent with the formation of essentially non-volatile products. Gas- and aerosol-phase oxidation products from the guaiacol system provide insight into the chemical mechanisms responsible for SOA formation. Syringol SOA yields are lower than those of phenol and guaiacol, likely due to novel methoxy group chemistry that leads to early fragmentation in the gas-phase photooxidation. Atomic oxygen to carbon (O : C) ratios calculated from high-resolution-time-of-flight Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS) measurements of the SOA in all three systems are ~ 0.9, which represent among the highest such ratios achieved in laboratory chamber experiments and are similar to that of aged atmospheric organic aerosol. The global contribution of SOA from intermediate volatility and semivolatile organic compounds has been shown to be substantial (Pye and Seinfeld, 2010). An approach to representing SOA formation from biomass burning emissions in atmospheric models could involve one or more surrogate species for which aerosol formation under well-controlled conditions has been quantified. The present work provides data for such an approach.

  14. Modeling Secondary Organic Aerosol Formation From Emissions of Combustion Sources

    NASA Astrophysics Data System (ADS)

    Jathar, Shantanu Hemant

    Atmospheric aerosols exert a large influence on the Earth's climate and cause adverse public health effects, reduced visibility and material degradation. Secondary organic aerosol (SOA), defined as the aerosol mass arising from the oxidation products of gas-phase organic species, accounts for a significant fraction of the submicron atmospheric aerosol mass. Yet, there are large uncertainties surrounding the sources, atmospheric evolution and properties of SOA. This thesis combines laboratory experiments, extensive data analysis and global modeling to investigate the contribution of semi-volatile and intermediate volatility organic compounds (SVOC and IVOC) from combustion sources to SOA formation. The goals are to quantify the contribution of these emissions to ambient PM and to evaluate and improve models to simulate its formation. To create a database for model development and evaluation, a series of smog chamber experiments were conducted on evaporated fuel, which served as surrogates for real-world combustion emissions. Diesel formed the most SOA followed by conventional jet fuel / jet fuel derived from natural gas, gasoline and jet fuel derived from coal. The variability in SOA formation from actual combustion emissions can be partially explained by the composition of the fuel. Several models were developed and tested along with existing models using SOA data from smog chamber experiments conducted using evaporated fuel (this work, gasoline, fischertropschs, jet fuel, diesels) and published data on dilute combustion emissions (aircraft, on- and off-road gasoline, on- and off-road diesel, wood burning, biomass burning). For all of the SOA data, existing models under-predicted SOA formation if SVOC/IVOC were not included. For the evaporated fuel experiments, when SVOC/IVOC were included predictions using the existing SOA model were brought to within a factor of two of measurements with minor adjustments to model parameterizations. Further, a volatility

  15. Influence of organism age on metal toxicity to Daphnia magna.

    PubMed

    Hoang, Tham C; Klaine, Stephen J

    2007-06-01

    Aquatic organisms living in surface water experience contaminant exposure at different life stages. While some investigators have examined the influence of organism age on the toxicity of pollutants, the general assumption in toxicology has been that young organisms were more sensitive than older organisms. In fact, some standardized toxicity tests call for the use of organisms less than 24 h old. This research characterized the age sensitivity of the water flea Daphnia magna to copper, zinc, selenium, and arsenic. During 21-d toxicity tests, organisms were exposed to a single 12-h pulse of either 70 microg/L Cu, 750 microg/L Zn, 1000 microg/L Se, or 5000 microg/L As at different ages ranging from 3 h to 10 d old. Mortality and reproduction were compiled over 21 d. During the juvenile stage, mortality increased and cumulative reproduction decreased with age, respectively. However, mortality decreased and cumulative reproduction increased with age when organisms became adult. Peak sensitivity occurred in 4-d-old organisms exposed to Cu and Zn, while 2- to 3-d-old organisms were most sensitive to As and Se. Growth of D. magna over 21 d was not affected by the 12-h pulse of Cu, Zn, Se, or As given at any organism age. This indicates the recovery of the organisms after exposure termination. PMID:17571686

  16. A Review of Secondary Health Conditions in Post-Polio Syndrome: Prevalence and Effects of Aging

    PubMed Central

    McNalley, Thomas E.; Yorkston, Kathryn M.; Jensen, Mark P.; Truitt, Anjali R.; Schomer, Katherine G.; Baylor, Carolyn; Molton, Ivan R.

    2014-01-01

    Objective This study seeks to better understand the prevalence and severity of secondary health conditions in individuals with post-polio syndrome (PPS), and the association between these conditions and aging. Design A scoping literature review was conducted searching electronic databases for studies published from 1986 – 2011. The scoping review provided information regarding the prevalence and associations of secondary health conditions in PPS with age or other duration-related variables. Results The findings indicate that: (1) individuals with PPS experience a number of serious secondary health conditions; (2) the most common conditions or symptoms are fatigue, pain, respiratory and sleep complaints, and increased risk of falls; (3) reports of the associations between the frequency or severity of conditions and age-related factors are variable, perhaps because of methodological inconsistencies between studies; and (4) there is a marked lack of longitudinal research examining the natural course of health conditions in people aging with PPS. Conclusions Longitudinal research is needed to understand the course of health conditions and the impact of multiple secondary conditions in people aging with PPS. Efforts are also needed to develop and test the efficacy of interventions to prevent these health secondary conditions or reduce their negative impact. PMID:25122095

  17. Secondary organic aerosol composition from C12 alkanes.

    PubMed

    Schilling Fahnestock, Katherine A; Yee, Lindsay D; Loza, Christine L; Coggon, Matthew M; Schwantes, Rebecca; Zhang, Xuan; Dalleska, Nathan F; Seinfeld, John H

    2015-05-14

    The effects of structure, NOx conditions, relative humidity, and aerosol acidity on the chemical composition of secondary organic aerosol (SOA) are reported for the photooxidation of three C12 alkanes: n-dodecane, cyclododecane, and hexylcyclohexane. Acidity was modified through seed particle composition: NaCl, (NH4)2SO4, and (NH4)2SO4 + H2SO4. Off-line analysis of SOA was carried out by solvent extraction and gas chromatography-mass spectrometry (GC/MS) and direct analysis in real-time mass spectrometry. We report here 750 individual masses of SOA products identified from these three alkane systems and 324 isomers resolved by GC/MS analysis. The chemical compositions for each alkane system provide compelling evidence of particle-phase chemistry, including reactions leading to oligomer formation. Major oligomeric species for alkane SOA are peroxyhemiacetals, hemiacetals, esters, and aldol condensation products. Furans, dihydrofurans, hydroxycarbonyls, and their corresponding imine analogues are important participants in these oligomer-producing reactions. Imines are formed in the particle phase from the reaction of the ammonium sulfate seed aerosol with carbonyl-bearing compounds present in all the SOA systems. Under high-NO conditions, organonitrate products can lead to an increase of aerosol volume concentration by up to a factor of 5 over that in low-NO conditions. Structure was found to play a key role in determining the degree of functionalization and fragmentation of the parent alkane, influencing the mean molecular weight of the SOA produced and the mean atomic O:C ratio. PMID:24814371

  18. 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

  19. Rethinking organic aerosols: semivolatile emissions and photochemical aging.

    PubMed

    Robinson, Allen L; Donahue, Neil M; Shrivastava, Manish K; Weitkamp, Emily A; Sage, Amy M; Grieshop, Andrew P; Lane, Timothy E; Pierce, Jeffrey R; Pandis, Spyros N

    2007-03-01

    Most primary organic-particulate emissions are semivolatile; thus, they partially evaporate with atmospheric dilution, creating substantial amounts of low-volatility gas-phase material. Laboratory experiments show that photo-oxidation of diesel emissions rapidly generates organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors. We attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species. Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations. Controlling organic particulate-matter concentrations will require substantial changes in the approaches that are currently used to measure and regulate emissions. PMID:17332409

  20. Investigation of formation and ageing of biogenic secondary aerosols by soft ionization aerosol mass spectrometry

    NASA Astrophysics Data System (ADS)

    Müller, Lars; Reinnig, Marc-Christopher; Vogel, Alexander; Mentel, Thomas; Tillmann, Ralf; Schlosser, E.; Wahner, Andreas; Donahue, Neil; Saathoff, Harald; Hoffmann, Thorsten

    2010-05-01

    The knowledge of the chemical composition of secondary organic aerosol is one essential key to understand the significance and fate of SOA in the atmosphere. However, the chemical evolution of SOA, from the very first condensing/nucleating molecules to the final oxidation products is still insufficiently understood and object of current research [1-3]. Consequently, the formation and photochemical ageing of secondary organic aerosol (SOA) was investigated in a series of reaction chamber experiments by applying on-line aerosol mass spectrometry (atmospheric pressure chemical ionization mass spectrometry (APCI/MS)) as well as off-line high performance liquid chromatography mass spectrometry (HPLC-MS). In a set of experiments, performed in the large outdoor reaction chamber SAPHIR (Jülich, Germany), SOA was generated from a boreal mixture of biogenic VOCs. During a two-day experiment the generated biogenic SOA was exposed to OH-radicals and the temporal evolution of the chemical composition was characterized. The applied on-line MS method not only provides highly time resolved chemical information (such as an AMS) but also allows molecular identification/quantification of specific marker compounds. Several first and higher generation BSOA products were identified. Among the higher generation products, especially a tricarboxylic acid (3-methyl-1,2,3-butanetricarboxylic acid) [2] was observed as an eye-catching oxidative processing marker. A more detailed investigation of hydroxyl radical induced SOA aging at the AIDA chamber facility in Karlsruhe, again using terpenes as SOA precursors, clearly showed that the formation of the tricarboxylic acid takes place in the gas phase by the reaction of semivolatile first generation products and hydroxyl radicals. Actually, there were no indications for OH induced oxidation of compounds in the condensed phase. The consequences of these results will be discussed in the contribution. 1. Rudich, Y., N.M. Donahue, and T.F. Mentel

  1. Primary sources and secondary formation of organic aerosols in Beijing, China.

    PubMed

    Guo, Song; Hu, Min; Guo, Qingfeng; Zhang, Xin; Zheng, Mei; Zheng, Jun; Chang, Chih Chung; Schauer, James J; Zhang, Renyi

    2012-09-18

    Ambient aerosol samples were collected at an urban site and an upwind rural site of Beijing during the CAREBEIJING-2008 (Campaigns of Air quality REsearch in BEIJING and surrounding region) summer field campaign. Contributions of primary particles and secondary organic aerosols (SOA) were estimated by chemical mass balance (CMB) modeling and tracer-yield method. The apportioned primary and secondary sources explain 73.8% ± 9.7% and 79.6% ± 10.1% of the measured OC at the urban and rural sites, respectively. Secondary organic carbon (SOC) contributes to 32.5 ± 15.9% of the organic carbon (OC) at the urban site, with 17.4 ± 7.6% from toluene, 9.7 ± 5.4% from isoprene, 5.1 ± 2.0% from α-pinene, and 2.3 ± 1.7% from β-caryophyllene. At the rural site, the secondary sources are responsible for 38.4 ± 14.4% of the OC, with the contributions of 17.3 ± 6.9%, 13.9 ± 9.1%, 5.6 ± 1.9%, and 1.7 ± 1.0% from toluene, isoprene, α-pinene, and β-caryophyllene, respectively. Compared with other regions in the world, SOA in Beijing is less aged, but the concentrations are much higher; between the sites, SOA is more aged and affected by regional transport at the urban site. The high SOA loading in Beijing is probably attributed to the high regional SOC background (~2 μg m(-3)). The toluene SOC concentration is high and comparable at the two sites, implying that some anthropogenic components, at least toluene SOA, are widespread in Beijing and represents a major factor in affecting the regional air quality. The aerosol gaseous precursor concentrations and temperature correlate well with SOA, both affecting SOA formation. The significant SOA enhancement with increasing water uptake and acidification indicates that the aqueous-phase reactions are largely responsible SOA formation in Beijing. PMID:22486583

  2. Evaporation Kinetics of Laboratory Generated Secondary Organic Aerosols at Elevated Relative Humidity

    SciTech Connect

    Wilson, Jacqueline M.; Imre, D.; Beranek, Josef; Shrivastava, ManishKumar B.; Zelenyuk, Alla

    2015-01-06

    Secondary organic aerosols (SOA) dominate atmospheric organic aerosols that affect climate, air quality, and health. Recent studies indicate that, contrary to previously held assumptions, at low relative humidity (RH) these particles are semi-solid and evaporate orders of magnitude slower than expected. Elevated relative humidity has the potential to affect significantly formation, properties, and atmospheric evolution of SOA particles. Here we present a study of the effect of RH on the room-temperature evaporation kinetics of SOA particles formed by ozonolysis of α-pinene and limonene. Experiments were carried out on SOA particles generated, evaporated, and aged at 0%, 50% and 90% RH. We find that in all cases evaporation begins with a relatively fast phase, during which 30% to 70% of the particle mass evaporates in 2 hours, followed by a much slower evaporation rate. Evaporation kinetics at 0% and 50% RH are nearly the same, while at 90% RH a slightly larger fraction evaporates. In all cases, aging the particles prior to inducing evaporation reduces the evaporative losses, with aging at elevated RH leading to more significant effect. In all cases, SOA evaporation is nearly size-independent, providing direct evidence that oligomers play a crucial role in determining the evaporation kinetics.

  3. Evaporation kinetics of laboratory-generated secondary organic aerosols at elevated relative humidity.

    PubMed

    Wilson, Jacqueline; Imre, Dan; Beránek, Josef; Shrivastava, Manish; Zelenyuk, Alla

    2015-01-01

    Secondary organic aerosols (SOA) dominate atmospheric organic aerosols that affect climate, air quality, and health. Recent studies indicate that, contrary to previously held assumptions, at low relative humidity (RH) these particles are semisolid and evaporate orders of magnitude slower than expected. Elevated relative humidity has the potential to affect significantly formation, properties, and atmospheric evolution of SOA particles. Here we present a study of the effect of RH on the room-temperature evaporation kinetics of SOA particles formed by ozonolysis of α-pinene and limonene. Experiments were carried out on α-pinene SOA particles generated, evaporated, and aged at <5%, 50 and 90% RH, and on limonene SOA particles at <5% and 90% RH. We find that in all cases evaporation begins with a relatively fast phase, during which 30-70% of the particle mass evaporates in 2 h, followed by a much slower evaporation rate. Evaporation kinetics at <5% and 50% RH are nearly the same, while at 90% RH a slightly larger fraction evaporates. In all cases, aging the particles prior to inducing evaporation reduces the evaporative losses; with aging at elevated RH leading to a more significant effect. In all cases, the observed SOA evaporation is nearly size-independent. PMID:25494490

  4. Organic Tanks Safety Program: Waste aging studies

    SciTech Connect

    Camaioni, D.M.; Samuels, W.D.; Lenihan, B.D.; Clauss, S.A.; Wahl, K.L.; Campbell, J.A.

    1994-11-01

    The underground storage tanks at the Hanford Complex contain wastes generated from many years of plutonium production and recovery processes, and mixed wastes from radiological degradation processes. The chemical changes of the organic materials used in the extraction processes have a direct on several specific safety issues, including potential energy releases from these tanks. This report details the first year`s findings of a study charged with determining how thermal and radiological processes may change the composition of organic compounds disposed to the tank. Their approach relies on literature precedent, experiments with simulated waste, and studies of model reactions. During the past year, efforts have focused on the global reaction kinetics of a simulated waste exposed to {gamma} radiation, the reactions of organic radicals with nitrite ion, and the decomposition reactions of nitro compounds. In experiments with an organic tank non-radioactive simulant, the authors found that gas production is predominantly radiolytically induced. Concurrent with gas generation they observe the disappearance of EDTA, TBP, DBP and hexone. In the absence of radiolysis, the TBP readily saponifies in the basic medium, but decomposition of the other compounds required radiolysis. Key organic intermediates in the model are C-N bonded compounds such as oximes. As discussed in the report, oximes and nitro compounds decompose in strong base to yield aldehydes, ketones and carboxylic acids (from nitriles). Certain aldehydes can react in the absence of radiolysis to form H{sub 2}. Thus, if the pathways are correct, then organic compounds reacting via these pathways are oxidizing to lower energy content. 75 refs.

  5. Primary and secondary gaseous organic carbon in Paris plume during the MEGAPOLI summer experiment

    NASA Astrophysics Data System (ADS)

    Ait-Helal, Warda; Borbon, Agnès.; Colomb, Aurélie; Michoud, Vincent; Afif, Charbel; Fronval, Isabelle; Leonardis, Thierry; Sauvage, Stéphane; Locoge, Nadine

    2010-05-01

    Within the FP7 MEGAPOLI project, an intensive field campaign was conducted in the Greater Paris region during July 2009. The main objective of the campaign was to quantify sources of primary and secondary aerosol and the role of organic gas-phase precursors, in and around a large agglomeration and to describe their evolution in the megacity plume. Observed gaseous organic carbon include a large dataset of primary and secondary VOCs of both anthropogenic and biogenic origin (monofunctionnal and bifunctionnal alkanes, alkenes, aromatics, terpenes, alcohols, aldehydes and ketones). Instruments were simultaneously deployed on ground-based platforms (MILEAGE) at two urban and suburban sites and one mobile platform (the French ATR-42 aircraft). Flights were designed to describe the urban plume ageing by performing several legs at increasing distances from the city centre. Techniques include on-line sampling and analysis by GC-FID and PTR-MS (on-board the aircraft) at high-time resolution and off-line sampling on carbonaceous cartridges and 2.4-DNPH-cartridges at 3-hour-time resolution. These measurements are collocated with other relevant trace gases measurements (O3, CO, NO, NO2, NOy) and meteorological parameters. First, the spatial and temporal variability of VOC from urban to regional scale is discussed regarding environmental conditions (air masses origin, meteorology, chemical regimes and photochemical ageing based on various photochemical clocks) and with respect to their sources. Then, the SOA forming potential of air masses is determined from laboratory determined particle-yields and observed gaseous organic precursors.

  6. Nitrogen Containing Organic Compounds and Oligomers in Secondary Organic Aerosol Formed by Photooxidation of Isoprene

    SciTech Connect

    Nguyen, Tran B.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Serguei

    2011-07-06

    Electrospray ionization high-resolution mass spectrometry (ESI HR-MS) was used to probe molecular structures of oligomers in secondary organic aerosol (SOA) generated in laboratory experiments on isoprene photooxidation at low- and high-NOx conditions. Up to 80-90% of the observed products are oligomers and up to 33% are nitrogen-containing organic compounds (NOC). We observe oligomers with up to 8 monomer units in length. Tandem mass spectrometry (MSn) confirms NOC compounds are organic nitrates and elucidates plausible chemical building blocks contributing to oligomer formation. Most organic nitrates are comprised of methylglyceric acid units. Other important multifunctional C2-C5 monomer units are identified including methylglyoxal, hydroxyacetone, hydroxyacetic acid, glycolaldehyde, and 2-methyltetrols. The majority of the NOC oligomers contain only one nitrate moiety resulting in a low average N:C ratio of 0.019. Average O:C ratios of the detected SOA compounds are 0.54 under the low-NOx conditions and 0.83 under the high-NOx conditions. Our results underscore the importance of isoprene photooxidation as a source of NOC in organic particulate matter.

  7. 2005 Mississippi Curriculum Framework: Secondary Aging Services. (Program CIP: 19.0702 - Adult Development and Aging)

    ERIC Educational Resources Information Center

    Walker, Kathy

    2005-01-01

    Secondary vocational-technical education programs in Mississippi are faced with many challenges resulting from sweeping educational reforms at the national and state levels. Schools and teachers are increasingly being held accountable for providing true learning activities to every student in the classroom. This accountability is measured through…

  8. The role of low volatile organics on secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Kokkola, H.; Yli-Pirilä, P.; Vesterinen, M.; Korhonen, H.; Keskinen, H.; Romakkaniemi, S.; Hao, L.; Kortelainen, A.; Joutsensaari, J.; Worsnop, D. R.; Virtanen, A.; Lehtinen, K. E. J.

    2014-02-01

    Large-scale atmospheric models, which typically describe secondary organic aerosol (SOA) formation based on chamber experiments, tend to systematically underestimate observed organic aerosol burdens. Since SOA constitutes a significant fraction of atmospheric aerosol, this discrepancy translates into an underestimation of SOA contribution to radiative forcing of atmospheric aerosol. Here we show that the underestimation of SOA yields can be partly explained by wall losses of SOA forming compounds during chamber experiments. We present a chamber experiment where α-pinene and ozone are injected into a Teflon chamber. When these two compounds react, we observe rapid formation and growth of new particles. Theoretical analysis of this formation and growth event indicates rapid formation of oxidized volatile organic compounds (OVOC) of very low volatility in the chamber. If these oxidized organic compounds form in the gas phase, their wall losses will have significant implications on their partitioning between the gas and particle phase. Although these OVOCs of very low volatility contribute to the growth of new particles, their mass will almost completely be depleted to the chamber walls during the experiment, while the depletion of OVOCs of higher volatilities is less efficient. According to our model simulations, the volatilities of OVOC contributing to the new particle formation event can be of the order of 10-5 μg m-3.

  9. Enhancement in Secondary Organic Aerosol Formation in the Presence of Preexisting Organic Particle.

    PubMed

    Ye, Jianhuai; Gordon, Catherine A; Chan, Arthur W H

    2016-04-01

    Atmospheric models of secondary organic aerosol (SOA) typically assume organic species form a well-mixed phase. As a result, partitioning of semivolatile oxidation products into the particle phase to form SOA is thought to be enhanced by preexisting organic particles. In this work, the physicochemical properties that govern such enhancement in SOA yield were examined. SOA yields from α-pinene ozonolysis were measured in the presence of a variety of organic seeds which were chosen based on polarity and phase state at room temperature. Yield enhancement was only observed with seeds of medium polarities (tetraethylene glycol and citric acid). Solid hexadecanol seed was observed to enhance SOA yields only in chamber experiments with longer mixing time scales, suggesting that the mixing process for SOA and hexadecanol may be kinetically limited at shorter time scales. Our observations indicate that, in addition to kinetic limitations, intermolecular interactions also play a significant role in determining SOA yields. Here we propose for the first time to use the Hansen solubility framework to determine aerosol miscibility and predict SOA yield enhancement. These results highlight that current models may overestimate SOA formation, and parametrization of intermolecular forces is needed for accurate predictions of SOA formation. PMID:26963686

  10. High-Resolution Mass Spectroscopic Analysis of Secondary Organic Aerosol Generated by Ozonolysis of Isoprene

    SciTech Connect

    Nguyen, Tran B; Bateman, Adam P; Bones, David L; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2010-02-01

    The chemical composition of secondary organic aerosol (SOA) generated from the ozonolysis of isoprene (C5H8) in the presence of an OH scavenger was examined using high-resolution electrospray ionization mass spectrometry (ESI-MS). The chemical composition of SOA is complex, with more than 1000 assigned peaks observed in the positive and negative ion mode spectra. Only a small fraction of peaks corresponds to known products of isoprene oxidation, such as pyruvic acid, glycolic acid, methylglyoxal, etc. The absolute majority of the detected peaks correspond to highly oxidized oligomeric constituents of SOA, with an average O:C molar ratio of ~0.6. The corresponding organic mass (OM) to organic oxygen (OO) ratio is OM/OO ~2.4. Approximately 8% of oxygen atoms in SOA are in the form of peroxides as quantified with an iodide test. Double bond equivalency (DBE) factors, representing the sum of all double bonds and rings, increase by 1 for every 2-3 additional carbon atoms in the molecule. The prevalent oligomer building blocks are therefore carbonyls or carboxylic acids with a C2-C3 skeleton. Kendrick analysis suggests that simple aldehydes, specifically formaldehyde, acetaldehyde, and methylglyoxal can serve as monomeric building blocks in the observed oligomers. The large number of reactive functional groups, especially organic peroxides and carbonyls, suggests that isoprene/O3 SOA should be prone to chemical and photochemical aging.

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

    NASA Astrophysics Data System (ADS)

    Palm, B. B.; Campuzano-Jost, P.; Ortega, A. M.; Day, D. A.; Kaser, L.; Jud, W.; Karl, T.; Hansel, A.; Hunter, J. F.; Cross, E. S.; Kroll, J. H.; Peng, Z.; Brune, W. H.; Jimenez, J. L.

    2015-11-01

    Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative time scales of condensation of low volatility organic compounds (LVOCs) onto particles, condensational loss to the walls, and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 μg m-3 when LVOC fate corrected), with maximum formation observed at 0.4-1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene + p-cymene concentrations, including a substantial increase just after sunrise at 07:00 LT. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than

  12. Cloud processing of organic compounds: Secondary organic aerosol and nitrosamine formation

    NASA Astrophysics Data System (ADS)

    Hutchings, James W., III

    Cloud processing of atmospheric organic compounds has been investigated through field studies, laboratory experiments, and numerical modeling. Observational cloud chemistry studies were performed in northern Arizona and fog studies in central Pennsylvania. At both locations, the cloud and fogs showed low acidity due to neutralization by soil dust components (Arizona) and ammonia (Pennsylvania). The field observations showed substantial concentrations (20-5500 ng•L -1) of volatile organic compounds (VOC) in the cloud droplets. The potential generation of secondary organic aerosol mass through the processing of these anthropogenic VOCs was investigated through laboratory and modeling studies. Under simulated atmospheric conditions, in idealized solutions, benzene, toluene, ethylbenzene, and xylene (BTEX) degraded quickly in the aqueous phase with half lives of approximately three hours. The degradation process yielded less volatile products which would contribute to new aerosol mass upon cloud evaporation. However, when realistic cloud solutions containing natural organic matter were used in the experiments, the reaction kinetics decreased with increasing organic carbon content, resulting in half lives of approximately 7 hours. The secondary organic aerosol (SUA) mass formation potential of cloud processing of BTEX was evaluated. SOA mass formation by cloud processing of BTEX, while strongly dependent on the atmospheric conditions, could contribute up to 9% of the ambient atmospheric aerosol mass, although typically ˜1% appears realistic. Field observations also showed the occurrence of N-nitrosodimethylamine (NDMA), a potent carcinogen, in fogs and clouds (100-340 ng•L -1). Laboratory studies were conducted to investigate the formation of NDMA from nitrous acid and dimethylamine in the homogeneous aqueous phase within cloud droplets. While NDMA was produced in the cloud droplets, the low yields (<1%) observed could not explain observational concentrations

  13. Multiphase processing of organic hydroxynitrates in secondary organic aerosol from the radical-initiated oxidation of multi-olefinic monoterpenes

    NASA Astrophysics Data System (ADS)

    Slade, J. H.; Lee, L. S.; Shepson, P. B.; De Perre, C.

    2015-12-01

    One of the greatest challenges facing atmospheric and climate science is understanding the impacts human activities have on the natural environment and atmospheric chemistry. The production of condensable organic compounds due to interactions between atmospheric oxidants, nitrogenous pollutants, and biogenic volatile organic compounds (BVOCs) emitted from the terrestrial biosphere can contribute significantly to the formation and growth of secondary organic aerosol (SOA). Aerosol particles influence atmospheric radiative transfer, cloud formation, and thus atmospheric temperatures. Due to their solubility in water and adsorptive nature, hydroxylated organic nitrates (HORONO2) may contribute significantly to the formation and chemical aging of SOA, and serve as an important sink for NOx (NO+NO2). We recently observed that a monoterpene β-hydroxy-organic nitrate (C10H17NO4), produced from the OH oxidation of α-pinene in the presence of NOx, undergoes rapid processing in the aerosol phase via an acid-catalyzed and pH-dependent hydrolysis mechanism, potentially impacting SOA growth and molecular composition. Further processing in the aerosol phase via polymerization and formation of organosulfates is expected, yet studies related to product identification and their formation mechanisms are limited. In this presentation, I will discuss recent laboratory-based reaction chamber studies of gas-phase organic nitrate production, SOA formation, and acidity-dependent aerosol-phase processing of organic nitrates produced from the NO3 oxidation of γ-terpinene. This BVOC is a diolefin, which as modeling studies suggest, may be an important nighttime organic nitrate precursor. Gas-phase organic nitrate compounds resulting from NO3 oxidation were qualitatively identified applying I- chemical ionization mass spectrometry (CIMS) and quantified via calibration using synthetic standards generated in our laboratory. Aerosol-phase analysis was carried out employing Fourier transform

  14. Health/Home Economics Classroom Activities for Secondary Schools. Schools in an Aging Society.

    ERIC Educational Resources Information Center

    Connecticut State Dept. of Education, Hartford.

    As the fastest-growing segment of society, older adults can be valuable resources for schools. The intent of this guide is to promote education for, with, and about older adults; to confront stereotypic images; and to present an accurate and balanced view of aging. The manual consists of 21 lesson plans for secondary teachers of health and home…

  15. Age Influences on the Demands and Coping Strategies of Post-Secondary Students.

    ERIC Educational Resources Information Center

    Arthur, Nancy

    This study explored the changing nature of post-secondary students' situational demands and how students of different ages cope with those demands. The study proceeded by tracking episodes of demands and coping throughout an academic year with a sample of 56 students enrolled at the Southern Alberta Institute of Technology (Canada) in 2-year…

  16. Functional Curriculum for Elementary, Middle, and Secondary Age Students with Special Needs. Second Edition

    ERIC Educational Resources Information Center

    Wehman, Paul; Kregel, John

    2004-01-01

    The second edition of Functional Curriculum for Elementary, Middle, and Secondary Age Students with Special Needs has an expanded framework for a functional and longitudinal curriculum for children and adolescents with disabilities and other special needs. These is a stronger demand than ever to provide a curriculum with everyday usefulness and…

  17. Resolving Issues Relevant to the Education of Secondary School Aged Youth with Behavior Disorders.

    ERIC Educational Resources Information Center

    Simpson, Robert G.

    The article provides a format for a workshop in which three issues which must be resolved by educators of secondary aged students with behavior disorders are discussed. The three issues to be addressed are: (1) determination of appropriate curriculum emphasis, (2) parent training/involvement in intervention strategies, and (3) criteria for…

  18. Primary School Attendance and Completion among Lower Secondary School Age Children in Uganda

    ERIC Educational Resources Information Center

    Moyi, Peter

    2013-01-01

    At the World Education Forum in Dakar in 2000, governments pledged to achieve education for all by 2015. However, if current enrollment trends continue, the number of out-of-school children could increase from current levels. Greater focus is needed on lower secondary school age (13-16 years) children. These children are not included estimates of…

  19. Effects of Age, Gender, School Class on Cardiopulmonary Resuscitation Skills of Nigerian Secondary School Students

    ERIC Educational Resources Information Center

    Onyeaso, Adedamola Olutoyin; Onyeaso, Chukwudi Ochi

    2016-01-01

    Background: The need for training of schoolchildren on cardiopulmonary resuscitation (CPR) as potential bystander CPR providers is growing globally but Nigeria is still behind and lacks basic necessary data. Purpose: The purpose of this study was to investigate the effects of age, gender and school class on CPR skills of Nigerian secondary school…

  20. Formation of secondary organic aerosol in the Paris pollution plume and its impact on surrounding regions

    NASA Astrophysics Data System (ADS)

    Zhang, Q. J.; Beekmann, M.; Freney, E.; Sellegri, K.; Pichon, J. M.; Schwarzenboeck, A.; Colomb, A.; Bourrianne, T.; Michoud, V.; Borbon, A.

    2015-12-01

    Secondary pollutants such as ozone, secondary inorganic aerosol, and secondary organic aerosol formed in the plumes of megacities can affect regional air quality. In the framework of the FP7/EU MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) project, an intensive campaign was launched in the greater Paris region in July 2009. The major objective was to quantify different sources of organic aerosol (OA) within a megacity and in its plume. In this study, we use airborne measurements aboard the French ATR-42 aircraft to evaluate the regional chemistry-transport model CHIMERE within and downwind of the Paris region. Two mechanisms of secondary OA (SOA) formation are used, both including SOA formation from oxidation and chemical aging of primary semivolatile and intermediate volatility organic compounds (SI-SOA) in the volatility basis set (VBS) framework. As for SOA formed from traditional VOC (volatile organic compound) precursors (traditional SOA), one applies chemical aging in the VBS framework adopting different SOA yields for high- and low-NOx environments, while another applies a single-step oxidation scheme without chemical aging. Two emission inventories are used for discussion of emission uncertainties. The slopes of the airborne OA levels versus Ox (i.e., O3 + NO2) show SOA formation normalized with respect to photochemical activity and are used for specific evaluation of the OA scheme in the model. The simulated slopes were overestimated slightly by factors of 1.1, 1.7 and 1.3 with respect to those observed for the three airborne measurements, when the most realistic "high-NOx" yields for traditional SOA formation in the VBS scheme are used in the model. In addition, these slopes are relatively stable from one day to another, which suggests that they are characteristic for the given megacity plume environment. The configuration with increased primary

  1. Effect of SO2 and Photolysis on Photooxidized Diesel Fuel Secondary Organic Aerosol Composition

    NASA Astrophysics Data System (ADS)

    MacMillan, A. C.; Blair, S. L.; Lin, P.; Laskin, A.; Laskin, J.; Nizkorodov, S.

    2014-12-01

    Diesel fuel (DSL) and sulfur dioxide (SO2) are important precursors to secondary organic aerosol (SOA) formation. DSL is often co-emitted with SO2 and NO2, thus it is important to understand the possible effects of SO2 on DSL SOA composition. Additionally, DSL SOA composition can be affected by photochemical aging processes such as photolysis. In this study, DSL SOA was first prepared under dry, high-NOx conditions with various concentrations of SO2 by photooxidation in a smog chamber. The SOA was then stripped of excess oxidants and gaseous organics with a denuder train and the resulting particles were photolyzed at various photolysis times in a quartz flow tube. The SOA composition, photochemical aging, properties, and mass concentration, before and after direct photolysis in the flow tube, were examined using several techniques. High-resolution mass spectrometry (HR-MS) was performed on DSL SOA samples to investigate the effect of SO2 on molecular level composition. SOA composition as a function of photolysis time was measured with an aerosol mass spectrometer (AMS). HR-MS results show that organosulfates are produced in DSL SOA. Both AMS and HR-MS results show that photolysis also has an effect on composition; though, this is more apparent in the HR-MS results than in the AMS results. In summary, both the presence of SO2 and solar radiation has an effect on DSL SOA composition.

  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 PAGESBeta

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

    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. Parameterization of the Cloud Nucleating Activity of Fresh, Aged, and Internally-Mixed Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Kreidenweis, S.; Petters, M.; Demott, P.; Prenni, A.; Ziemann, P.

    2006-12-01

    Carbonaceous particle types affect global climate, visibility, and human health, but their primary and secondary sources, sinks, and tropospheric lifetimes are highly uncertain. The size and hygroscopicity of particles, and in particular their activity as cloud condensation nuclei (CCN), plays a large role in determining their atmospheric impacts and lifetimes. However, hygroscopicity is difficult to parameterize for many organic species for which no thermodynamic data exist, and for complex, multicomponent aerosols of undefined composition. We propose a simple method to describe the relationship between dry particle diameter and CCN activity using a single hygroscopicity parameter, κ. We derive values of κ from fitting of experimental CCN-activity data from the literature and from recent experiments, including oxidation-aged organic particles and secondary organic aerosols. Values of κ are between 0.5 and 2 for highly-CCN- active salts such as sodium chloride, between 0.01 and 0.5 for slightly to very hygroscopic organic aerosols such as those produced in biomass burning and as secondary organic aerosols, and 0 for nonhygroscopic components. The hygroscopicity of internal mixtures can be calculated as a volume fraction weighted average of the hygroscopicity parameters of the individual species comprising the mixture. Aging of aerosol, understood as changes in hygroscopicity due to condensation of hydrophilic species, coagulation of aerosol populations, or heterogeneous chemical reactions, are described conveniently by changes in κ. Our studies show that oxidative aging that proceeds by addition of functional groups to the CHx carbon backbone leads to only small changes in κ, and thus the process alone is inefficient at rendering small, initially- hydrophobic primary organic particles capable of being scavenged by cloud-drop nucleation. Other processes, such as coagulation and condensation, control the rate of hydrophobic-to-hydrophilic conversion of primary

  5. Secondary organic aerosol formation and primary organic aerosol oxidation from biomass burning smoke in a flow reactor during FLAME-3

    NASA Astrophysics Data System (ADS)

    Ortega, A. M.; Day, D. A.; Cubison, M. J.; Brune, W. H.; Bon, D.; de Gouw, J. A.; Jimenez, J. L.

    2013-05-01

    We report the physical and chemical effects of photochemically aging dilute biomass-burning smoke. A potential aerosol mass "PAM" flow reactor was used with analysis by a high-resolution aerosol mass spectrometer and a proton-transfer reaction ion-trap mass spectrometer during the FLAME-3 campaign. Hydroxyl (OH) radical concentrations in the reactor reached up to ~ 1000 times average tropospheric levels, producing effective OH exposures equivalent to up to 5 days aging in the atmosphere. VOC observations show aromatics and terpenes decrease with aging, while formic acid and other unidentified oxidation products increase. Unidentified gas-phase oxidation products, previously observed in atmospheric and laboratory measurements, were observed here, including evidence of multiple generations of photochemistry. Substantial new organic aerosol (OA) mass ("net SOA"; secondary OA) was observed from aging biomass-burning smoke, resulting in an total OA average of 1.42 ± 0.36 times the initial primary OA (POA) after oxidation. This study confirms that the net SOA to POA ratio of biomass burning smoke is far lower on average than that observed for urban emissions. Although most fuels were very reproducible, significant differences were observed among the biomasses, with some fuels resulting in a doubling of the OA mass, while for others a very small increase or even a decrease was observed. Net SOA formation in the photochemical reactor increased with OH exposure (OHexp), typically peaking around three days of equivalent atmospheric photochemical age (OHexp ~ 3.9 × 1011 molecules cm-3 s-1), then leveling off at higher exposures. The amount of additional OA mass added from aging is positively correlated with initial POA concentration, but not with the total VOC concentration or the concentration of known SOA precursors. The mass of SOA formed often exceeds the mass of the known VOC precursors, indicating the likely importance of primary semivolatile/intermediate volatility

  6. Composition of Secondary Organic Aerosols Produced by Photo-Oxidation of Biomass Burning Emissions in a Smog Chamber

    NASA Astrophysics Data System (ADS)

    Desyaterik, Y.; Sullivan, A.; Hennigan, C. J.; Robinson, A. L.; Collett, J. L.

    2009-12-01

    Knowledge of the chemical composition of atmospheric organic aerosols (OA) is essential for accurate representation of OA in air quality and climate models. Both the sources of OA and their properties and effects remain poorly understood. In particular, we still know relatively little about the atmospheric formation of secondary organic aerosols (SOA). There is growing interest in the impact of biomass burning emissions on air quality, human health, and radiative forcing. Through a series of experiments, we are working to quantify changes in the chemical composition of wood smoke particles as a result of photochemical aging under well-controlled laboratory conditions. One specific objective of this study is to identify markers for biomass burning SOA and test whether these markers can be used in atmospheric samples to quantify SOA formation from aging of biomass burning emissions. We analyzed SOA generated in a smog chamber by photooxidation of smoke produced by burning oak wood. In order to initiate photochemistry, the chamber was irradiated with UV light. Aqueous extracts of collected aerosol samples were analyzed with Electrospray Ionization Time-of-Flight Mass Spectrometry. The high mass accuracy of these measurements reduces ambiguity in the assignment of elemental compositions for observed ions. Analysis has shown that primary oak smoke aerosol includes products of the thermal decomposition of cellulose (levoglucosan, cyclotene etc.) and lignin (guaiacol and syringol derivatives, mostly aldehydes and alcohols). After 2 hours of aging at typical summertime hydroxyl radical concentrations, the aerosol mass increased 2.5 fold due to the production of secondary organic aerosol. Mass spectra of the secondary organic aerosol formed are dominated by organic nitrates (nitrophenol, nitrocresol, nitrocatechol, and nitroguaiacol) and aromatic acids (benzoic acid, mono and di-hydroxybenzoic acid). Both nitrates and acids most likely are formed due to oxidation of the

  7. Combined volatility and mass spectrometric measurements of biogenic secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Emanuelsson, E.; Buchholz, A.; Hallquist, M.; Kiendler-Scharr, A.; Mentel, T.; Spindler, C.

    2009-04-01

    The volatility of secondary organic aerosol (SOA) from the oxidation of mixtures of biogenic Volatile Organic Compounds (VOC) has been investigated in the SAPHIR facility in Forschungszentrum Jülich, Germany, by using a Volatility Tandem Differential Mobility Analyser (VTDMA). The standard VTDMA setup comprises three main parts: 1) An initial DMA, where a nearly monodisperse size fraction of the aerosol particles is selected (typically 100 or 150 nm), 2) the oven unit, i.e. four ovens in parallel where each oven includes a heating and adsorption section where the evaporation and adsorption of the volatile fraction occurs and 3) a final SMPS (Scanning Mobility Particle Sizer) system where the residual particle number distribution is measured. For this measurement campaign the set-up also contained a Quadrupole Aerosol Mass Spectrometer (Aerodyne QAMS). The temperature of the ovens can be varied between 298 and well above 573 K. In parallel to the final SMPS the AMS was used for chemical composition and density measurements. When the system was dedicated for AMS measurements the initial DMA was bypassed to improve the aerosol concentration. However, the produced SOA has a narrow size distribution still making it possible to follow small changes in the aerosol peak diameter. A general feature of the thermo-denuder system is that a less volatile SOA gives a larger residual particle size distribution compared to more volatile SOA. The experiments conducted were based on photochemical oxidation of selected terpene mixtures. A reference boreal mixture of terpenes, consisting of α-pinene, β-pinene, limonene, ^-3-carene, and ocimene was used as base case. Secondary organic aerosol was formed from the precursor compounds by reaction with O3/H2O/OH in SAPHIR on the first day. The particles were kept in the chamber for up to two further days and were exposed to natural sunlight and OH radicals to initiate close to natural chemical ageing. The VTDMA results show that SOA

  8. Transboundary secondary organic aerosol in western Japan: An observed limitation of the f44 oxidation indicator

    NASA Astrophysics Data System (ADS)

    Irei, Satoshi; Takami, Akinori; Sadanaga, Yasuhiro; Miyoshi, Takao; Arakaki, Takemitsu; Sato, Kei; Kaneyasu, Naoki; Bandow, Hiroshi; Hatakeyama, Shiro

    2015-11-01

    To obtain evidence for secondary organic aerosol formation during the long-range transport of air masses over the East China Sea, we conducted field measurements in March 2012 at the Fukue atmospheric monitoring station, Nagasaki, in western Japan. The relative abundance of m/z 44 in fine organic aerosol (f44) was measured by an Aerodyne aerosol chemical speciation monitor. The stable carbon isotope ratio (δ13C) of low-volatile water-soluble organic carbon (LV-WSOC) in the daily filter samples of total suspended particulate matter was also analyzed using an elemental-analyzer coupled with an isotope ratio mass spectrometer. Additionally, in situ measurements of NOx and NOy were performed using NOx and NOy analyzers. The measurements showed that, unlike the systematic trends observed in a previous field study, a scatter plot for δ13C of LV-WSOC versus f44 indicated a random variation. Comparison of f44 with the estimated photochemical age by the NOx/NOy ratio revealed that the random distribution of f44 values near 0.2 is likely an indication of saturation already. Such f44 values were significantly lower than the observed f44 (∼0.3) at Hedo in the previous study. These findings imply that the saturation point of f44, and the use of f44 as an oxidation indicator, is case dependent.

  9. Laboratory studies on secondary organic aerosol formation from crude oil vapors.

    PubMed

    Li, R; Palm, B B; Borbon, A; Graus, M; Warneke, C; Ortega, A M; Day, D A; Brune, W H; Jimenez, J L; de Gouw, J A

    2013-01-01

    Airborne measurements of aerosol composition and gas phase compounds over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in June 2010 indicated the presence of high concentrations of secondary organic aerosol (SOA) formed from organic compounds of intermediate volatility. In this work, we investigated SOA formation from South Louisiana crude oil vapors reacting with OH in a Potential Aerosol Mass flow reactor. We use the dependence of evaporation time on the saturation concentration (C*) of the SOA precursors to separate the contribution of species of different C* to total SOA formation. This study shows consistent results with those at the DWH oil spill: (1) organic compounds of intermediate volatility with C* = 10(5)-10(6) μg m(-3) contribute the large majority of SOA mass formed, and have much larger SOA yields (0.37 for C* = 10(5) and 0.21 for C* = 10(6) μg m(-3)) than more volatile compounds with C*≥10(7) μg m(-3), (2) the mass spectral signature of SOA formed from oxidation of the less volatile compounds in the reactor shows good agreement with that of SOA formed at DWH oil spill. These results also support the use of flow reactors simulating atmospheric SOA formation and aging. PMID:24088179

  10. Aqueous secondary organic aerosol (SOA) production from the oxidation of phenols by triplet excited state organics

    NASA Astrophysics Data System (ADS)

    Smith, J.; Yu, L.; Zhang, Q.; Anastasio, C.

    2011-12-01

    Recent literature has shown that atmospheric condensed-phase chemistry can play a significant role in the evolution of organic aerosols, including the formation of secondary organic aerosol (SOA). SOA formation from the oxidation of volatile organic compounds (VOCs) in the aqueous phase has largely focused on oxidations involving the hydroxyl radical and other oxidants, such as photochemically created triplet excited states, have not been fully investigated. Phenolic compounds are one of the primary carbon emission classes from biomass and wood combustion and have significant water solubility. Once in the aqueous phase, phenolic compounds can react with the triplet excited states of non-phenolic aromatic carbonyls (NPCs), particle-bound organics that are also emitted in large quantities from wood combustion. The oxidation of phenolic species in the condensed phase by triplet excited states can result in the production of SOA. A main goal of this study was to investigate bulk solution reaction kinetics under atmospherically relevant conditions in order to ascertain how these reactions can impact aqueous-phase SOA production. In our experiments, we studied the reactions of five phenols (phenol, guaiacol, syringol, catechol, and resorcinol) with the triplet state of 3,4-dimethoxybenzaldehyde (34-DMB) during simulated solar radiation. We have characterized the impacts of pH, ionic strength and reactant concentrations on the reaction behavior of this system. In addition, we analyzed the SOA formed using high-resolution aerosol mass spectrometry, ion chromatography, and liquid chromatography-mass spectrometry to infer the reaction mechanisms. Our evidence suggests that under atmospherically relevant conditions, triplet excited states can be the dominant oxidant of phenolics and contribute significantly to the total SOA budget.

  11. 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...

  12. 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 ...

  13. 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...

  14. Secondary Organic Aerosol Formation and Organic Nitrate Yield from NO3 Oxidation of Biogenic Hydrocarbons

    PubMed Central

    2014-01-01

    The secondary organic aerosol (SOA) mass yields from NO3 oxidation of a series of biogenic volatile organic compounds (BVOCs), consisting of five monoterpenes and one sesquiterpene (α-pinene, β-pinene, Δ-3-carene, limonene, sabinene, and β-caryophyllene), were investigated in a series of continuous flow experiments in a 10 m3 indoor Teflon chamber. By making in situ measurements of the nitrate radical and employing a kinetics box model, we generate time-dependent yield curves as a function of reacted BVOC. SOA yields varied dramatically among the different BVOCs, from zero for α-pinene to 38–65% for Δ-3-carene and 86% for β-caryophyllene at mass loading of 10 μg m–3, suggesting that model mechanisms that treat all NO3 + monoterpene reactions equally will lead to errors in predicted SOA depending on each location’s mix of BVOC emissions. In most cases, organonitrate is a dominant component of the aerosol produced, but in the case of α-pinene, little organonitrate and no aerosol is formed. PMID:25229208

  15. Resolving detailed molecular structures in complex organic mixtures and modeling their secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Goodman-Rendall, Kevin A. S.; Zhuang, Yang R.; Amirav, Aviv; Chan, Arthur W. H.

    2016-03-01

    Characterization of unresolved complex mixtures (UCMs) remains an ongoing challenge towards developing detailed and accurate inputs for modeling secondary organic aerosol (SOA) formation. Traditional techniques based on gas chromatography/electron impact-mass spectrometry induce excessive fragmentation, making it difficult to speciate and quantify isomers precisely. The goal of this study is to identify individual organic isomers by gas chromatography/mass spectrometry with supersonic molecular beam (SMB-GC/MS, also known as GC/MS with Cold EI) and to incorporate speciated isomers into an SOA model that accounts for the specific structures elucidated. Two samples containing atmospherically relevant UCMs are analyzed. The relative isomer distributions exhibit remarkably consistent trends across a wide range of carbon numbers. Constitutional isomers of different alkanes are speciated and individually quantified as linear, branched - for the first time by position of branching - multiply branched, or unsaturated - by degree of ring substitution and number of rings. Relative amounts of exact molecular structures are used as input parameters in an SOA box model to study the effects of molecular structures on SOA yields and volatility evolution. Highly substituted cyclic, mono-substituted cyclic, and linear species have the highest SOA yields while branched alkanes formed the least SOA. The rate of functionalization of a representative UCM is found to be in agreement with current volatility basis set (VBS) parameterizations based on detailed knowledge of composition and known oxidation mechanisms, confirming the validity of VBS parameters currently used in air quality models.

  16. Primary to secondary organic aerosol: evolution of organic emissions from mobile combustion sources

    NASA Astrophysics Data System (ADS)

    Presto, A. A.; Gordon, T. D.; Robinson, A. L.

    2014-05-01

    A series of smog chamber experiments were conducted to investigate the transformation of primary organic aerosol (POA) and formation of secondary organic aerosol (SOA) during the photooxidation of dilute exhaust from a fleet of gasoline and diesel motor vehicles and two gas-turbine engines. In experiments where POA was present in the chamber at the onset of photooxidation, positive matrix factorization (PMF) was used to determine separate POA and SOA factors from aerosol mass spectrometer data. A 2-factor solution, with one POA factor and one SOA factor, was sufficient to describe the organic aerosol for gasoline vehicles, diesel vehicles, and one of the gas-turbine engines. Experiments with the second gas-turbine engine required a 3-factor PMF solution with a POA factor and two SOA factors. Results from the PMF analysis were compared to the residual method for determining SOA and POA mass concentrations. The residual method apportioned a larger fraction of the organic aerosol mass as POA because it assumes that all mass at m / z 57 is associated with POA. The POA mass spectrum for the gasoline and diesel vehicles exhibited high abundances of the CnH2n+1 series of ions (m / z 43, 57, etc.) and was similar to the mass spectra of the hydrocarbon-like organic aerosol factor determined from ambient data sets with one exception, a diesel vehicle equipped with a diesel oxidation catalyst. POA mass spectra for the gas-turbine engines are enriched in the CnH2n-1 series of ions (m / z 41, 55, etc.), consistent with the composition of the lubricating oil used in these engines. The SOA formed from the three sources exhibits high abundances of m / z 44 and 43, indicative of mild oxidation. The SOA mass spectra are consistent with less-oxidized ambient SV-OOA (semivolatile oxygenated organic aerosols) and fall within the triangular region of f44 versus f43 defined by ambient measurements. However there is poor absolute agreement between the experimentally derived SOA mass

  17. CCN activity and volatility of β-caryophyllene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Frosch, M.; Bilde, M.; Nenes, A.; Praplan, A. P.; Jurányi, Z.; Dommen, J.; Gysel, M.; Weingartner, E.; Baltensperger, U.

    2013-02-01

    In a series of smog chamber experiments, the cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) generated from ozonolysis of β-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, κCCN, from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with κCCN in the range 0.001-0.16), and in dark experiments with no OH scavenger present, κCCN decreased when particles were sent through the thermodenuder (with a temperature up to 50 °C). SOA was generated under different experimental conditions: In some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived κCCN consistently increased with time after initial injection of β-caryophyllene, showing that chemical ageing increases the CCN activity of β-caryophyllene SOA. κCCN was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol for particles aged for several hours.

  18. Ozonolysis of a series of biogenic organic volatile compounds and secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Bernard, François; Quilgars, Alain; Cazaunau, Mathieu; Grosselin, Benoît.; Daele, Véronique; Mellouki, Abdelwahid; Winterhalter, Richard; Moortgat, Geert K.

    2010-05-01

    Secondary organic aerosols are formed via nucleation of atmospheric organic vapours on pre-existing particles observed in various rural environments where the organic fraction represents the major part of the observed nano-particle (Kavouras and Stephanou, 2002; Kulmala et al., 2004a). However, nucleation of organic vapors appears to be unlikely thermodynamically in relevant atmospheric conditions (Kulmala et al., 2004b). In this work, a systematic study has been conducted to investigate the aerosol formation through the ozonolysis of a series of monotepenes using a newly developed aerosol flow reactor and the ICARE indoor simulation chamber. The nucleation thresholds have been determined for SOA formed through the reaction of ozone with a-Pinene, sabinene, myrcene and limonene in absence of any observable existing particles. The measurements were performed using the flow reactor combined to a particle counter (CPC 3022). Number concentrations of SOA have been measured for different concentration of consumed monoterpenes. The data obtained allow us to estimate the nucleation threshold for a range of 0.2 - 45 ppb of consumed monoterpenes. The nucleation threshold values obtained here (≤ 1 ppb of the consumed monoterpenes) have been found to be lower than the previously reported ones (Berndt et al., 2003; Bonn and Moortgat, 2003; Koch et al., 2000; Lee and Kamens, 2005). The ICARE simulation chamber has been used to study the mechanism of the reaction of ozone with various acyclic terpenes (myrcene, ocimene, linalool and a-farnesene) and to derive the SOA mass formation yield. The time-concentration profiles of reactants and products in gas-phase were obtained using in-situ Fourier Transform Infrared Spectroscopy. In addition, the number and mass concentrations of SOA have been monitored with a Scanning Mobility Particle Sizer. The chemical composition of the SOA formed has been tentatively characterised using Liquid Chromatography - Mass Spectrometry. The results

  19. A Systematic Evaluation of the Extent of Photochemical Processing in Different Types of Secondary Organic Aerosols in the Aqueous Phase

    NASA Astrophysics Data System (ADS)

    Romonosky, D.; Lee, H.; Epstein, S. A.; Nizkorodov, S.; Laskin, J.; Laskin, A.

    2013-12-01

    A significant fraction of atmospheric organic compounds are predominantly found in condensed phases, such as organic phase in aerosol particles or aqueous phase in cloud droplets. The oxidation of VOCs followed by the condensation of products into particles was thought to be the main mechanism of organic aerosol (OA) formation. However, in the last several years, scientists have realized that a large fraction, if not the majority of organic particles, is produced through cloud and fog photochemical processes. Many of these organic compounds are photolabile, and can degrade through direct photolysis or indirect photooxidation processes on time scales that are comparable to the typical lifetimes of droplets (hours) and particles (days). We previously reported that compounds in secondary organic aerosol (SOA) from ozonolysis of d-limonene efficiently photodegrade in both organic (Walser et al., 2007) and aqueous phases (Bateman et al., 2011). Significant photolysis was also observed in an aqueous extract of SOA from high-NOx photooxidation of isoprene (Nguyen et al., 2012). More recent experiments studying the response to irradiation of complex aqueous mixtures (as opposed to solutions of isolated compounds) found surprising resilience to photodegradation in aqueous extracts of SOA prepared by photooxidation of alpha-pinene (Romonosky et al., unpublished). We present a systematic investigation of the extent of photochemical processing in different types of SOA from various biogenic and anthropogenic precursors. Chamber- or flowtube-generated SOA is collected on an inert substrate, extracted in a methanol/water solution (70:30), photolyzed in the aqueous solution, and the extent of change in the molecular level composition of the material is assessed with high-resolution mass spectrometry (HR-MS). The outcome of this study will be improved understanding of the role of condensed-phase photochemistry in chemical aging of aerosol particles and cloud droplets. Bateman et

  20. Formation of secondary organic carbon and cloud impact on carbonaceous aerosols at Mount Tai, North China

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Wang, Tao; Guo, Jia; Gao, Rui; Xue, Likun; Zhang, Jiamin; Zhou, Yang; Zhou, Xuehua; Zhang, Qingzhu; Wang, Wenxing

    2012-01-01

    Carbonaceous aerosols measured at Mount Tai in north China in 2007 were further examined to study the formation of secondary organic carbon (SOC) and the impact of clouds on carbonaceous species. A constrained EC-tracer method and a multiple regression model showed excellent agreement in estimating SOC concentration. The average concentrations of non-volatile and semi-volatile SOC (SOC NV and SOC SV) were 2.61, 5.58 μg m -3 in spring and 2.81, 10.44 μg m -3 in summer. The total SOC accounted for 57.3% and 71.2% of total organic carbon in spring and summer, respectively, indicating the presence of high loading of secondary organic aerosol (SOA) in the North China Plain. The fraction of SOC NV increased with photochemical age (as indicated by NO x/NO y ratios) of air mass, whereas SOC SV was also influenced by the dynamic equilibrium between formation and sink. Significant scavenging by clouds of non-volatile organic carbon (OC NV) and elemental carbon (EC) was observed, whereas semi-volatile organic carbon (OC SV) concentrations increased during clouds, suggesting substantial SOA formation through aqueous-phase reactions in clouds. A mass balance model was proposed to quantify the scavenging coefficients for OC NV, EC and formation rates of OC SV in clouds. The scavenging coefficient constant of EC ( KEC) varied from 0.11 to 0.90 h -1, and was higher than that of OC NV ( KNV-OC: 0.07-0.55 h -1), implying internal mixing of EC with more hygroscopic species. The formation rate constant ( JSV-OC) and sink constant ( SSV-OC) of OC SV ranged from 0.09 to 1.39 h -1 and 0.001 to 1.07 h -1, respectively. These field derived parameters could be incorporated into atmospheric models to help close the gap between predicted and observed SOA loadings in the atmosphere.

  1. Organizing your practice for screening and secondary prevention among adults.

    PubMed

    Knierim, Kyle E; Fernald, Douglas H; Staton, Elizabeth W; Nease, Donald E

    2014-06-01

    Prevention plays an important role in achieving the triple aim of decreasing per capita health care costs, improving the health of populations, and bettering the patient experience. Primary care is uniquely positioned to provide preventive services. External forces are aligning to support the transition of primary care from traditional models focused on disease-specific, acute episodes of care to new ways of organizing that are more patient centered, team based, and quality driven. By aligning leadership, building change capacity, and selectively choosing relevant processes to change, those practicing primary care can successfully organize their practice environment to deliver preventive services. PMID:24830604

  2. Graphic Organizers for Secondary Students with Learning Disabilities

    ERIC Educational Resources Information Center

    Singleton, Sabrina M.; Filce, Hollie Gabler

    2015-01-01

    Research suggests students with learning disabilities often have trouble connecting new and prior knowledge, distinguishing essential and nonessential information, and applying comprehension strategies (DiCecco & Gleason, 2002; Vaughn & Edmonds, 2006). Graphic organizers have been suggested as tools educators can use to facilitate critical…

  3. Organized Pneumonia Secondary to Increasing Doses of Temozolomide

    PubMed Central

    Consuegra Vanegas, Angélica; Matachana Martínez, María; Cordero Lorenzana, Lourdes; Vidal García, Iria; Montero Martínez, Carmen

    2015-01-01

    Surgery, radiotherapy (RT), and chemotherapy have a role in the control of tumor growth, progression, and recurrence in high-grade gliomas. Temozolomide has been incorporated as the main chemotherapy agent for managing these tumors. Here, we present a case of a patient who developed a severe organizing pneumonia after increasing doses of temozolomide for a high-grade glioma. PMID:26487994

  4. PRODUCTION OF SECONDARY ORGANIC AEROSOL FROM MULTIPHASE TERPENE PHOTOOXIDATION

    EPA Science Inventory

    This project involves a field and laboratory study of the production of aerosol from the atmospheric photooxidation of biogenic volatile organic compounds (BVOCs), specifically the terpenes α- and β-pinene, using a unique combination of approaches that rely on produ...

  5. 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

  6. Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Romonosky, Dian E.; Ali, Nujhat N.; Saiduddin, Mariyah N.; Wu, Michael; Lee, Hyun Ji (Julie); Aiona, Paige K.; Nizkorodov, Sergey A.

    2016-04-01

    Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.

  7. Interpretation of Secondary Organic Aerosol Formation from Diesel Exhaust Photooxidation in an Environmental Chamber

    SciTech Connect

    Nakao, Shunsuke; Shrivastava, ManishKumar B.; Nguyen, Anh; Jung, Hee-Jung; Cocker, David R.

    2011-04-14

    Secondary organic aerosol (SOA) formation from diesel exhaust in a smog chamber was investigated. Particle volume measurement based on mobility diameter is shown to underestimate SOA formation from diesel exhaust due to the external void space of agglomerate particles, in which case mass-based measurement technique is necessary. Rapid determination of particle effective density as a function of particle mass was performed by an Aerosol Particle Mass analyzer – Scanning Mobility Particle Sizer (APM-SMPS) to obtain particle mass concentration and fractal dimension. Continuous aging of aerosol was observed in terms of atomic ratio (O/C), from 0.05 to 0.25 in 12 hours, underscoring the importance of multi-generational oxidation of low-volatile organic vapors emitted from diesel engine as the significant source of oxygenated SOA. Experimental conditions possibly have strong impacts on physical evolution of diesel particulates in a smog chamber. Higher particle effective densities were observed when raw exhaust was injected into a full bag as opposed to filling a bag with diluted exhaust using an ejector diluter. When longer transfer line was used for injecting diesel exhaust into the smog chamber, rapid particle coagulation was observed, leading to increasing particle volume concentration in dark while its mass concentration is decreasing.

  8. Organic aerosol formation photo-enhanced by the formation of secondary photosensitizers in aerosols.

    PubMed

    Aregahegn, Kifle Z; Nozière, Barbara; George, Christian

    2013-01-01

    Secondary organic aerosols (SOA), which are produced by the transformations of volatile organic compounds in the atmosphere, play a central role in air quality, public health, visibility and climate, but their formation and aging remain poorly characterized. This study evidences a new mechanism for SOA formation based on photosensitized particulate-phase chemistry. Experiments were performed with a horizontal aerosol flow reactor where the diameter growth of the particles was determined as a function of various parameters. In the absence of gas-phase oxidant, experiments in which ammonium sulfate seeds containing glyoxal were exposed to gas-phase limonene and UV light exhibited a photo-induced SOA growth. Further experiments showed that this growth was due to traces of imidazole-2-carboxaldehyde (IC) in the seeds, a condensation product of glyoxal acting as an efficient photosensitizer. Over a 19 min irradiation time, 50 nm seed particles containing this compound were observed to grow between 3.5 and 30 +/- 3% in the presence of either limonene, isoprene, alpha-pinene, beta-pinene, or toluene in concentrations between 1.8 and 352 ppmv. The other condensation products of glyoxal, imidazole (IM) and 2,2-bi1H-imidazole (BI), also acted as photosensitizer but with much less efficiency under the same conditions. In the atmosphere, glyoxal and potentially other gas precursors would thus produce efficient photosensitizers in aerosol and autophotocatalyze SOA growth. PMID:24601000

  9. The Correlation of Secondary Organic Aerosol with Odd Oxygen in Mexico City

    EPA Science Inventory

    Data from a mountain location intercepting the Mexico City emission plume demonstrate a strong correlation between secondary organic aerosol and odd-oxygen (O3 + NO2). The measured oxygenated-organic aerosol correlates with odd-oxygen measurements with an a...

  10. 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...

  11. The contribution of secondary organic aerosol to PM2.5 concentrations in Pittsburgh

    NASA Astrophysics Data System (ADS)

    Cabada, J. C.; Pandis, S. N.; Robinson, A. L.; Subramanian, R.; Polidori, A.; Turpin, B.

    2002-12-01

    A major component of PM2.5 in the Eastern US is carbonaceous material. This organic particulate matter results from both direct emissions from sources such as automobiles, trucks and industries (primary), and from the oxidation of organic gases (secondary). Data from the Pittsburgh Air Quality Study are used to examine the contribution of secondary organic aerosol to the total organic aerosol loading measured in the city during 2001 and 2002. The contribution of secondary organic aerosol is estimated by using elemental carbon as a tracer for primary emissions of organic particulate matter (OC to EC ratio approach). A systematic method for the determination of the primary ratio has been developed based on the correlation of measurements of OC and EC to gaseous tracers of photochemical activity (O3) and primary emissions (CO, NOx). This method is applied to different sets of organic aerosols measurements (using an undenuded sampler, a denuded sampler and an in-situ carbon analyzer) for carbonaceous concentrations. Consistent results for the SOA fraction are obtained when the method is applied to the different sets of measurements for OC and EC. This approach indicates that between 20 and 40% of the organic particulate matter in Pittsburgh during the summer and fall of 2001 is secondary in origin while negligible contributions of SOA are estimated for the winter of 2001 and the spring of 2002.

  12. 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.

  13. Contribution of Organic Vapors to the Growth of Secondary Aerosols

    NASA Astrophysics Data System (ADS)

    Wang, L.; Khalizov, A.; Zhang, R.

    2008-12-01

    Processes governing the growth of atmospheric aerosols represent an important aspect of anthropogenic climate forcing but remain poorly understood. Condensation of organic vapors onto the pre-existing atmospheric aerosols, potentially followed by chemical reactions within the particles medium, is believed to be one of the major pathways that contribute to particle growth. Recent research has focused on the total mass increase on pre-existing seed particles, but the chemistry that determines the efficiency of organic uptake remains to be elucidated. In this study, attenuated total reflection- Fourier transform infrared spectroscopy (ATR-FT-IR) was used to study the formation of new chemical bonds in the sub-micron sulfuric acid droplets deposited on ATR crystal and subjected to exposure to organic vapors (2,4-hexadienal and glyoxal). The observation of new functional groups, together with the dependence of the absorption intensity on the relative humidity, indicates that the uptake of 2,4-hexadienal is through an aldol condensation reaction and uptake of glyoxal is an acid-catalyzed hydration followed by self-reaction of hydrated and carbonyl forms to form cyclic acetal structures. The evolvement of infrared absorption features also suggests that the uptake of both compounds is at least partly reversible.

  14. 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 PMID:11924857

  15. CCN activity and volatility of β-caryophyllene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Frosch, M.; Bilde, M.; Nenes, A.; Praplan, A. P.; Jurányi, Z.; Dommen, J.; Gysel, M.; Weingartner, E.; Baltensperger, U.

    2012-08-01

    In a series of smog chamber experiments, the Cloud Condensation Nuclei (CCN) activity of Secondary Organic Aerosol (SOA) generated from ozonolysis of β-caryophyllene was characterized by determining the CCN derived hygroscopicity parameter, κCCN, from experimental data. Two types of CCN counters, operating at different temperatures, were used. The effect of semi-volatile organic compounds on the CCN activity of SOA was studied using a thermodenuder. Overall, SOA was only slightly CCN active (with κCCN in the range 0.001-0.16), and in dark experiments with no OH scavenger present, κCCN decreased when particles were sent through the thermodenuder (with a temperature up to 50 °C). SOA was generated under different experimental conditions: in some experiments, an OH scavenger (2-butanol) was added. SOA from these experiments was less CCN active than SOA produced in experiments without an OH scavenger (i.e. where OH was produced during ozonolysis). In other experiments, lights were turned on, either without or with the addition of HONO (OH source). This led to the formation of more CCN active SOA. SOA was aged up to 30 h through exposure to ozone and (in experiments with no OH scavenger present) to OH. In all experiments, the derived κCCN consistently increased with time after initial injection of β-caryophyllene, showing that chemical ageing increases the CCN activity of β-caryophyllene SOA. κCCN was also observed to depend on supersaturation, which was explained either as an evaporation artifact from semi-volatile SOA (only observed in experiments lacking light exposure) or, alternatively, by effects related to chemical composition depending on dry particle size. Using the method of Threshold Droplet Growth Analysis it was also concluded that the activation kinetics of the SOA do not differ significantly from calibration ammonium sulphate aerosol.

  16. Secondary organic aerosol formation through fog processing of VOCs

    NASA Astrophysics Data System (ADS)

    Herckes, P.; Hutchings, J. W.

    2010-07-01

    Volatile Organic Compounds (VOCs) including benzene, toluene, ethylbenzene and xylenes (BTEX) have been determined in highly concentrated amounts (>1 ug/L) in intercepted clouds in northern Arizona (USA). These VOCs are found in concentrations much higher than predicted by partitioning alone. The reactivity of BTEX in the fog/cloud aqueous phase was investigated through laboratory studies. BTEX species showed fast degradation in the aqueous phase in the presence of peroxides and light. Observed half-lives ranged from three and six hours, substantially shorter than the respective gas phase half-lives (several days). The observed reaction rates were on the order of 1 ppb/min but decreased substantially with increasing concentrations of organic matter (TOC). The products of BTEX oxidation reactions were analyzed using HPLC-UV and LCMS. The first generation of products identified included phenol and cresols which correspond to the hydroxyl-addition reaction to benzene and toluene. Upon investigating of multi-generational products, smaller, less volatile species are predominant although a large variety of products is found. Most reaction products have substantially lower vapor pressure and will remain in the particle phase upon droplet evaporation. The SOA generation potential of cloud and fog processing of BTEX was evaluated using simple calculations and showed that in ideal situations these reactions could add up to 9% of the ambient aerosol mass. In more conservative scenarios, the contribution of the processing of BTEX was around 1% of ambient aerosol concentrations. Overall, cloud processing of VOC has the potential to contribute to the atmospheric aerosol mass. However, the contribution will depend upon many factors such as the irradiation, organic matter content in the droplets and droplet lifetime.

  17. Organic composition of carbonaceous aerosols in an aged prescribed fire plume

    NASA Astrophysics Data System (ADS)

    Yan, B.; Zheng, M.; Hu, Y. T.; Lee, S.; Kim, H. K.; Russell, A. G.

    2007-12-01

    Aged smoke from a prescribed fire (dominated by conifers) impacted Atlanta, GA on 28 February 2007 and dramatically increased hourly ambient concentrations of PM2.5 and organic carbon (OC) up to 140 and 72 μg m-3, respectively. It was estimated that over 1 million residents were exposed to the smoky air lasting from the late afternoon to midnight. To better understand the processes impacting the aging of fire plumes, a detailed chemical speciation of carbonaceous aerosols was conducted by gas chromatography/mass spectrometry (GC/MS) analysis. Ambient concentrations of many organic species (levoglucosan, resin acids, retene, n-alkanes, n-alkanoic acids) associated with wood burning emission were significantly elevated on the event day. Levoglucosan increased by a factor of 10, while hopanes, steranes, cholesterol and major polycyclic aromatic hydrocarbons (PAHs) did not show obvious increases. Strong odd over even carbon number predominance was found for n-alkanes versus even over odd predominance for n-alkanoic acids. Alteration of resin acids during transport from burning sites to monitors is suggested by the observations. Our study also suggests that large quantities of biogenic volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) were released both as products of combustion and unburned vegetation heated by the fire. Higher leaf temperature can stimulate biogenic VOC and SVOC emissions, which enhanced formation of secondary organic aerosols (SOA) in the atmosphere. This is supported by elevated ambient concentrations of secondary organic tracers (dicarboxylic acids, 2-methyltetrols, pinonic acid and pinic acid). An approximate source profile was built for the aged fire plume to help better understand evolution of wood smoke emission and can be used for source apportionment.

  18. Organic composition of carbonaceous aerosols in an aged prescribed fire plume

    NASA Astrophysics Data System (ADS)

    Yan, B.; Zheng, M.; Hu, Y. T.; Lee, S.; Kim, H. K.; Russell, A. G.

    2008-11-01

    Aged smoke from a prescribed fire (dominated by conifers) impacted Atlanta, GA on 28 February 2007 and dramatically increased hourly ambient concentrations of PM2.5 and organic carbon (OC) up to 140 and 72 μg m-3, respectively. It was estimated that over 1 million residents were exposed to the smoky air lasting from the late afternoon to midnight. To better understand the processes impacting the aging of fire plumes, a detailed chemical speciation of carbonaceous aerosols was conducted by gas chromatography/mass spectrometry (GC/MS) analysis. Ambient concentrations of many organic species (levoglucosan, resin acids, retene, n-alkanes and n-alkanoic acids) associated with wood burning emission were significantly elevated on the event day. Levoglucosan increased by a factor of 10, while hopanes, steranes, cholesterol and major polycyclic aromatic hydrocarbons (PAHs) did not show obvious increases. Strong odd over even carbon number predominance was found for n-alkanes versus even over odd predominance for n-alkanoic acids. Alteration of resin acids during transport from burning sites to monitors is suggested by the observations. Our study also suggests that large quantities of biogenic volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) were released both as products of combustion and unburned vegetation heated by the fire. Higher leaf temperature can stimulate biogenic VOC and SVOC emissions, which enhanced formation of secondary organic aerosols (SOA) in the atmosphere. This is supported by elevated ambient concentrations of secondary organic tracers (dicarboxylic acids, 2-methyltetrols, pinonic acid and pinic acid). An approximate source profile was built for the aged fire plume to help better understand evolution of wood smoke emission and for use in source impact assessment.

  19. Fuel composition and secondary organic aerosol formation: gas-turbine exhaust and alternative aviation fuels.

    PubMed

    Miracolo, Marissa A; Drozd, Greg T; Jathar, Shantanu H; Presto, Albert A; Lipsky, Eric M; Corporan, Edwin; Robinson, Allen L

    2012-08-01

    A series of smog chamber experiments were performed to investigate the effects of fuel composition on secondary particulate matter (PM) formation from dilute exhaust from a T63 gas-turbine engine. Tests were performed at idle and cruise loads with the engine fueled on conventional military jet fuel (JP-8), Fischer-Tropsch synthetic jet fuel (FT), and a 50/50 blend of the two fuels. Emissions were sampled into a portable smog chamber and exposed to sunlight or artificial UV light to initiate photo-oxidation. Similar to previous studies, neat FT fuel and a 50/50 FT/JP-8 blend reduced the primary particulate matter emissions compared to neat JP-8. After only one hour of photo-oxidation at typical atmospheric OH levels, the secondary PM production in dilute exhaust exceeded primary PM emissions, except when operating the engine at high load on FT fuel. Therefore, accounting for secondary PM production should be considered when assessing the contribution of gas-turbine engine emissions to ambient PM levels. FT fuel substantially reduced secondary PM formation in dilute exhaust compared to neat JP-8 at both idle and cruise loads. At idle load, the secondary PM formation was reduced by a factor of 20 with the use of neat FT fuel, and a factor of 2 with the use of the blend fuel. At cruise load, the use of FT fuel resulted in no measured formation of secondary PM. In every experiment, the secondary PM was dominated by organics with minor contributions from sulfate when the engine was operated on JP-8 fuel. At both loads, FT fuel produces less secondary organic aerosol than JP-8 because of differences in the composition of the fuels and the resultant emissions. This work indicates that fuel reformulation may be a viable strategy to reduce the contribution of emissions from combustion systems to secondary organic aerosol production and ultimately ambient PM levels. PMID:22732009

  20. Absence of cytoglobin promotes multiple organ abnormalities in aged mice

    PubMed Central

    Thuy, Le Thi Thanh; Van Thuy, Tuong Thi; Matsumoto, Yoshinari; Hai, Hoang; Ikura, Yoshihiro; Yoshizato, Katsutoshi; Kawada, Norifumi

    2016-01-01

    Cytoglobin (Cygb) was identified in hepatic stellate cells (HSCs) and pericytes of all organs; however, the effects of Cygb on cellular functions remain unclear. Here, we report spontaneous and age-dependent malformations in multiple organs of Cygb−/− mice. Twenty-six percent of young Cygb−/− mice (<1 year old) showed heart hypertrophy, cystic disease in the kidney or ovary, loss of balance, liver fibrosis and lymphoma. Furthermore, 71.3% (82/115) of aged Cygb−/− mice (1–2 years old) exhibited abnormalities, such as heart hypertrophy and cancer development in multiple organs; by contrast, 5.8% (4/68) of aged wild-type (WT) mice had abnormalities (p < 0.0001). Interestingly, serum and urine analysis demonstrated that the concentration of nitric oxide metabolites increased significantly in Cygb−/− mice, resulting in an imbalance in the oxidative stress and antioxidant defence system that was reversed by NG-monomethyl-L-arginine treatment. A senescent phenotype and evidence of DNA damage were found in primary HSCs and the liver of aged Cygb−/− mice. Moreover, compared with HSC+/+, HSC−/− showed high expression of Il-6 and chemokine mRNA when cocultured with mouse Hepa 1–6 cells. Thus, the absence of Cygb in pericytes provokes organ abnormalities, possibly via derangement of the nitric oxide and antioxidant defence system and through accelerated cellular senescence. PMID:27146058

  1. Estimates of non-traditional secondary organic aerosols from aircraft SVOC and IVOC emissions using CMAQ

    NASA Astrophysics Data System (ADS)

    Woody, M. C.; West, J. J.; Jathar, S. H.; Robinson, A. L.; Arunachalam, S.

    2015-06-01

    Utilizing an aircraft-specific parameterization based on smog chamber data in the Community Multiscale Air Quality (CMAQ) model with the volatility basis set (VBS), we estimated contributions of non-traditional secondary organic aerosols (NTSOA) for aircraft emissions during landing and takeoff (LTO) activities at the Hartsfield-Jackson Atlanta International Airport. NTSOA, formed from the oxidation of semi-volatile and intermediate volatility organic compounds (S/IVOCs), is a heretofore unaccounted component of fine particulate matter (PM2.5) in most air quality models. We expanded a prerelease version of CMAQ with VBS implemented for the Carbon Bond 2005 (CB05) chemical mechanism to use the Statewide Air Pollution Research Center 2007 (SAPRC-07) chemical mechanism and added species representing aircraft S/IVOCs and corresponding NTSOA oxidation products. Results indicated that the maximum monthly average NTSOA contributions occurred at the airport and ranged from 2.4 ng m-3 (34 % from idle and 66 % from non-idle aircraft activities) in January to 9.1 ng m-3 (33 and 67 %) in July. This represents 1.7 % (of 140 ng m-3) in January and 7.4 % in July (of 122 ng m-3) of aircraft-attributable PM2.5 compared to 41.0-42.0 % from elemental carbon and 42.8-58.0 % from inorganic aerosols. As a percentage of PM2.5, impacts were higher downwind of the airport, where NTSOA averaged 4.6-17.9 % of aircraft-attributable PM2.5 and, considering alternative aging schemes, was as high as 24.0 % - thus indicating the increased contribution of aircraft-attributable SOA as a component of PM2.5. However, NTSOA contributions were generally low compared to smog chamber results, particularly at idle, due to the considerably lower ambient organic aerosol concentrations in CMAQ compared to those in the smog chamber experiments.

  2. Photochemistry of limonene secondary organic aerosol studied with chemical ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Pan, Xiang

    Limonene is one of the most abundant monoterpenes in the atmosphere. Limonene easily reacts with gas-phase oxidants in air such as NO3, ozone and OH. Secondary organic aerosol (SOA) is formed when low vapor pressure products condense into particles. Chemicals in SOA particles can undergo further reactions with oxidants and with solar radiation that significantly change SOA composition over the course of several days. The goal of this work was to characterize radiation induced reaction in SOA. To perform experiments, we have designed and constructed an Atmospheric Pressure Chemical Ionization Mass Spectrometer (APCIMS) coupled to a photochemical cell containing SOA samples. In APCIMS, (H2O)nH 3O+ clusters are generated in a 63Ni source and react with gaseous organic analytes. Most organic chemicals are not fragmented by the ionization process. We have focused our attention on limonene SOA prepared in two different ways. The first type of SOA is produced by oxidation of limonene by ozone; and the second type of SOA is formed by the NO3-induced oxidation of limonene. They model the SOA formed under daytime and nighttime conditions, respectively. Ozone initiated oxidation is the most important chemical sink for limonene both indoors, where it is used for cleaning purposes, and outdoors. Terpenes are primarily oxidized by reactions with NO3 at night time. We generated limonene SOA under different ozone and limonene concentrations. The resulting SOA samples were exposed to wavelength-tunable radiation in the UV-Visible range between 270 nm and 630 nm. The results show that the photodegradation rates strongly depend on radiation wavelengths. Gas phase photodegradation products such as acetone, formaldehyde, acetaldehyde, and acetic acid were shown to have different production rates for SOA formed in different concentration conditions. Even for SOA prepared under the lowest concentrations, the SOA photodegradation was efficient. The conclusion is that exposure of SOA to

  3. Limited effect of anthropogenic nitrogen oxides on Secondary Organic Aerosol formation

    DOE PAGESBeta

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

    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

  4. Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity

    SciTech Connect

    Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J.; Shilling, John E.; Martin, Scot T.; Bertram, Allan K.

    2013-05-14

    Particles composed of secondary organic material (SOM) are abundant in the lower troposphere and play important roles in climate, air quality, and health. The viscosity of these particles is a fundamental property that is presently poorly quantified for conditions relevant to the lower troposphere. Using two new techniques, namely a bead-mobility technique and a poke-flow technique, in conjunction with simulations of fluid flow, we measure the viscosity of the watersoluble component of SOM produced by α-pinene ozonolysis. The viscosity is comparable to that of honey at 90% relative humidity (RH), comparable to that of peanut butter at 70% RH and greater than or comparable to that of bitumen for ≤ 30% RH, implying that the studied SOM ranges from liquid to semisolid/solid at ambient relative humidities. With the Stokes-Einstein relation, the measured viscosities further imply that the growth and evaporation of SOM by the exchange of organic molecules between the gas and condensed phases may be confined to the surface region when RH ≤ 30%, suggesting the importance of an adsorption-type mechanism for partitioning in this regime. By comparison, for RH ≥ 70% partitioning of organic molecules may effectively occur by an absorption mechanism throughout the bulk of the particle. Finally, the net uptake rates of semi-reactive atmospheric oxidants such as O3 are expected to decrease by two to five orders of magnitude for a change in RH from 90% to ≤ 30% RH, with possible implications for the rates of chemical aging of SOM particles in the atmosphere.

  5. 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.

  6. In Vivo and Real-time Monitoring of Secondary Metabolites of Living Organisms by Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Wang, Lei; Ye, Wen-Cai; Yao, Zhong-Ping

    2013-07-01

    Secondary metabolites are compounds that are important for the survival and propagation of animals and plants. Our current understanding on the roles and secretion mechanism of secondary metabolites is limited by the existing techniques that typically cannot provide transient and dynamic information about the metabolic processes. In this manuscript, by detecting venoms secreted by living scorpion and toad upon attack and variation of alkaloids in living Catharanthus roseus upon stimulation, which represent three different sampling methods for living organisms, we demonstrated that in vivo and real-time monitoring of secondary metabolites released from living animals and plants could be readily achieved by using field-induced direct ionization mass spectrometry.

  7. Organic tanks safety program FY96 waste aging studies

    SciTech Connect

    Camaioni, D.M.; Samuels, W.D.; Linehan, J.C.; Clauss, S.A.; Sharma, A.K.; Wahl, K.L.; Campbell, J.A.

    1996-10-01

    Uranium and plutonium production at the Hanford Site produced large quantities of radioactive by-products and contaminated process chemicals, which are stored in underground tanks awaiting treatment and disposal. Having been made strongly alkaline and then subjected to successive water evaporation campaigns to increase storage capacity, the wastes now exist in the physical forms of salt cakes, metal oxide sludges, and partially saturated aqueous brine solutions. The tanks that contain organic process chemicals mixed with nitrate/nitrite salt wastes may be at risk for fuel- nitrate combustion accidents. The purpose of the Waste Aging Task is to elucidate how chemical and radiological processes will have aged or degraded the organic compounds stored in the tanks. Ultimately, the task seeks to develop quantitative measures of how aging changes the energetic properties of the wastes. This information will directly support efforts to evaluate the hazard as well as to develop potential control and mitigation strategies.

  8. Source apportioning of primary and secondary organic carbon in summer PM2.5 in Hong Kong using positive matrix factorization of secondary and primary organic tracer data

    NASA Astrophysics Data System (ADS)

    Hu, Di; Bian, Qijing; Lau, Alexis K. H.; Yu, Jian Zhen

    2010-08-01

    The major inorganic constituents and organic tracer compounds in PM2.5 were used in positive matrix factorization (PMF) and chemical mass balance (CMB) models to apportion the primary and secondary source contributions to organic carbon (OC) in Hong Kong during the summer of 2006. Secondary organic aerosol (SOA) tracers of several biogenic and anthropogenic hydrocarbons were included in the PMF analysis. Their inclusion allowed the identification of two components of SOA among seven factors resolved by PMF. One SOA component was mainly associated with secondary sulfate and nitrate. The other SOA component, characterized by biogenic SOA tracers and mixed with biomass burning and vegetative detritus particles, was biomass burning-induced SOA. Secondary OC (SOC) apportioned by PMF (SOCPMF) was on average 6.84 μgC m-3 (65% of PM2.5 OC) on high pollution days under influence of significant regional transport (i.e., regional days) and 0.70 μgC m-3 (25% of PM2.5 OC) on days under the influence of mainly local emissions (i.e., local days). The biomass burning-induced SOA accounted for 20% of the total SOA on the regional days, underlining the importance of biomass burning aerosol source in this region. The average uncertainty for the SOCPMF estimates was ˜20% on the regional days and ˜120% on the local days. SOCPMF was compared with SOC determined by CMB (SOCCMB, i.e., unapportioned OC by CMB analysis) and a tracer-based method (SOCTBM) that apportioned SOC contributions by four hydrocarbon precursors including isoprene, monoterpenes, β-caryophyllene, and toluene. The three estimates of SOC closely tracked with each other among individual samples. The SOCCMB and SOCPMF estimates on the majority of the regional days differed from each other by less than 25%. Good correlations between contributions of SOC and individual primary OC sources apportioned by PMF and CMB further added to the credence to the PMF-derived estimation of secondary and primary OC source

  9. Assessment of organ dose reduction and secondary cancer risk associated with the use of proton beam therapy and intensity modulated radiation therapy in treatment of neuroblastomas

    PubMed Central

    2013-01-01

    Background To compare proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) with conformal radiation therapy (CRT) in terms of their organ doses and ability to cause secondary cancer in normal organs. Methods Five patients (median age, 4 years; range, 2–11 years) who underwent PBT for retroperitoneal neuroblastoma were selected for treatment planning simulation. Four patients had stage 4 tumors and one had stage 2A tumor, according to the International Neuroblastoma Staging System. Two patients received 36 Gy, two received 21.6 Gy, and one received 41.4 Gy of radiation. The volume structures of these patients were used for simulations of CRT and IMRT treatment. Dose–volume analyses of liver, stomach, colon, small intestine, pancreas, and bone were performed for the simulations. Secondary cancer risks in these organs were calculated using the organ equivalent dose (OED) model, which took into account the rates of cell killing, repopulation, and the neutron dose from the treatment machine. Results In all evaluated organs, the mean dose in PBT was 20–80% of that in CRT. IMRT also showed lower mean doses than CRT for two organs (20% and 65%), but higher mean doses for the other four organs (110–120%). The risk of secondary cancer in PBT was 24–83% of that in CRT for five organs, but 121% of that in CRT for pancreas. The risk of secondary cancer in IMRT was equal to or higher than CRT for four organs (range 100–124%). Conclusion Low radiation doses in normal organs are more frequently observed in PBT than in IMRT. Assessments of secondary cancer risk showed that PBT reduces the risk of secondary cancer in most organs, whereas IMRT is associated with a higher risk than CRT. PMID:24180282

  10. Modeling organic aerosols during MILAGRO: importance of biogenic secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Jimenez, J. L.; Madronich, S.; Aiken, A. C.; Bessagnet, B.; Curci, G.; Fast, J.; Lamarque, J.-F.; Onasch, T. B.; Roux, G.; Schauer, J. J.; Stone, E. A.; Ulbrich, I. M.

    2009-09-01

    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 contain 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 one-step oxidation of anthropogenic (i.e. aromatics, alkanes), biogenic (i.e. monoterpenes and isoprene), and biomass-burning SOA precursors and their partitioning into both organic and aqueous phases. Conservative assumptions are made for uncertain parameters to maximize the amount of SOA produced by the model. 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, with a factor of 2-10 model underestimate. When only anthropogenic SOA precursors were considered, the model was able to reproduce within a factor of two the sharp increase in OOA concentrations during the late morning at both urban and near-urban locations but the discrepancy increases rapidly later in the day, consistent with previous results, and is especially obvious when the column-integrated SOA mass is considered instead of the surface concentration. The increase in the missing SOA mass in the afternoon coincides with the sharp drop in POA suggesting a

  11. Organic Nitrate Contribution to New Particle Formation and Growth in Secondary Organic Aerosols from α-Pinene Ozonolysis.

    PubMed

    Berkemeier, Thomas; Ammann, Markus; Mentel, Thomas F; Pöschl, Ulrich; Shiraiwa, Manabu

    2016-06-21

    The chemical kinetics of organic nitrate production during new particle formation and growth of secondary organic aerosols (SOA) were investigated using the short-lived radioactive tracer (13)N in flow-reactor studies of α-pinene oxidation with ozone. Direct and quantitative measurements of the nitrogen content indicate that organic nitrates accounted for ∼40% of SOA mass during initial particle formation, decreasing to ∼15% upon particle growth to the accumulation-mode size range (>100 nm). Experiments with OH scavengers and kinetic model results suggest that organic peroxy radicals formed by α-pinene reacting with secondary OH from ozonolysis are key intermediates in the organic nitrate formation process. The direct reaction of α-pinene with NO3 was found to be less important for particle-phase organic nitrate formation. The nitrogen content of SOA particles decreased slightly upon increase of relative humidity up to 80%. The experiments show a tight correlation between organic nitrate content and SOA particle-number concentrations, implying that the condensing organic nitrates are among the extremely low volatility organic compounds (ELVOC) that may play an important role in the nucleation and growth of atmospheric nanoparticles. PMID:27219077

  12. Mechanisms of Formation of Secondary Organic Aerosols and Implications for Global Radiative Forcing

    SciTech Connect

    John H. Seinfeld

    2011-12-08

    Organic material constitutes about 50% of global atmospheric aerosol mass, and the dominant source of organic aerosol is the oxidation of volatile hydrocarbons, to produce secondary organic aerosol (SOA). Understanding the formation of SOA is crucial to predicting present and future climate effects of atmospheric aerosols. The goal of this program is to significantly increase our understanding of secondary organic aerosol (SOA) formation in the atmosphere. Ambient measurements indicate that the amount of SOA in the atmosphere exceeds that predicted in current models based on existing laboratory chamber data. This would suggest that either the SOA yields measured in laboratory chambers are understated or that all major organic precursors have not been identified. In this research program we are systematically exploring these possibilities.

  13. Aging, Neurogenesis, and Caloric Restriction in Different Model Organisms

    PubMed Central

    Arslan-Ergul, Ayca; Ozdemir, A Tugrul; Adams, Michelle M

    2013-01-01

    Brain aging is a multifactorial process that is occurring across multiple cognitive domains. A significant complaint that occurs in the elderly is a decrement in learning and memory ability. Both rodents and zebrafish exhibit a similar problem with memory during aging. The neurobiological changes that underlie this cognitive decline are complex and undoubtedly influenced by many factors. Alterations in the birth of new neurons and neuron turnover may contribute to age-related cognitive problems. Caloric restriction is the only non-genetic intervention that reliably increases life span and healthspan across multiple organisms although the molecular mechanisms are not well-understood. Recently the zebrafish has become a popular model organism for understanding the neurobiological consequences but to date very little work has been performed. Similarly, few studies have examined the effects of dietary restriction in zebrafish. Here we review the literature related to memory decline, neurogenesis, and caloric restriction across model organisms and suggest that zebrafish has the potential to be an important animal model for understanding the complex interactions between age, neurobiological changes in the brain, and dietary regimens or their mimetics as interventions. PMID:23936746

  14. Secondary organic aerosol formation from ozone-initiated reactions with nicotine and secondhand tobacco smoke

    NASA Astrophysics Data System (ADS)

    Sleiman, Mohamad; Destaillats, Hugo; Smith, Jared D.; Liu, Chen-Lin; Ahmed, Musahid; Wilson, Kevin R.; Gundel, Lara A.

    2010-11-01

    We used controlled laboratory experiments to evaluate the aerosol-forming potential of ozone reactions with nicotine and secondhand smoke. Special attention was devoted to real-time monitoring of the particle size distribution and chemical composition of SOA as they are believed to be key factors determining the toxicity of SOA. The experimental approach was based on using a vacuum ultraviolet photon ionization time-of-flight aerosol mass spectrometer (VUV-AMS), a scanning mobility particle sizer (SMPS) and off-line thermal desorption coupled to mass spectrometry (TD-GC-MS) for gas-phase byproducts analysis. Results showed that exposure of SHS to ozone induced the formation of ultrafine particles (<100 nm) that contained high molecular weight nitrogenated species ( m/ z 400-500), which can be due to accretion/acid-base reactions and formation of oligomers. In addition, nicotine was found to contribute significantly (with yields 4-9%) to the formation of secondary organic aerosol through reaction with ozone. The main constituents of the resulting SOA were tentatively identified and a reaction mechanism was proposed to elucidate their formation. These findings identify a new component of thirdhand smoke that is associated with the formation of ultrafine particles (UFP) through oxidative aging of secondhand smoke. The significance of this chemistry for indoor exposure and health effects is highlighted.

  15. The 12-Month Prevalence of DSM-IV Anxiety Disorders among Nigerian Secondary School Adolescents Aged 13-18 Years

    ERIC Educational Resources Information Center

    Adewuya, Abiodun O.; Ola, Bola A.; Adewumi, Tomi A.

    2007-01-01

    Aims: To estimate the 12-month prevalence of DSM-IV-specific anxiety disorders among Nigerian secondary school adolescents aged 13-18 years. Method: A representative sample of adolescents (n=1090) from senior secondary schools in a semi-urban town in Nigeria was assessed for the 12-month prevalence of DSM-IV-specific anxiety. Results: The 12-month…

  16. Invertebrates as model organisms for research on aging biology

    PubMed Central

    Murthy, Mahadev; Ram, Jeffrey L.

    2015-01-01

    Invertebrate model systems, such as nematodes and fruit flies, have provided valuable information about the genetics and cellular biology involved in aging. However, limitations of these simple, genetically tractable organisms suggest the need for other model systems, some of them invertebrate, to facilitate further advances in the understanding of mechanisms of aging and longevity in mammals, including humans. This paper introduces 10 review articles about the use of invertebrate model systems for the study of aging by authors who participated in an ‘NIA-NIH symposium on aging in invertebrate model systems’ at the 2013 International Congress for Invertebrate Reproduction and Development. In contrast to the highly derived characteristics of nematodes and fruit flies as members of the superphylum Ecdysozoa, cnidarians, such as Hydra, are more ‘basal’ organisms that have a greater number of genetic orthologs in common with humans. Moreover, some other new model systems, such as the urochordate Botryllus schlosseri, the tunicate Ciona, and the sea urchins (Echinodermata) are members of the Deuterostomia, the same superphylum that includes all vertebrates, and thus have mechanisms that are likely to be more closely related to those occurring in humans. Additional characteristics of these new model systems, such as the recent development of new molecular and genetic tools and a more similar pattern to humans of regeneration and stem cell function suggest that these new model systems may have unique advantages for the study of mechanisms of aging and longevity. PMID:26241448

  17. Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber

    NASA Astrophysics Data System (ADS)

    Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Ježek, I.; Drinovec, L.; Močnik, G.; Möhler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prévôt, A. S. H.

    2012-10-01

    We present a new mobile environmental reaction chamber for the simulation of the atmospheric aging of aerosols from different emissions sources without limitation from the instruments or facilities available at any single site. The chamber can be mounted on a trailer for transport to host facilities or for mobile measurements. Photochemistry is simulated using a set of 40 UV lights (total power 4 KW). Characterisation of the emission spectrum of these lights shows that atmospheric photochemistry can be accurately simulated over a range of temperatures from -7-25 °C. A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 molecules cm-3 s-1 was determined at 25 °C. Further, we present the first application of the mobile chamber and demonstrate its utility by quantifying primary organic aerosol (POA) emission and secondary organic aerosol (SOA) production from a Euro 5 light duty gasoline vehicle. Exhaust emissions were sampled during the New European Driving Cycle (NEDC), the standard driving cycle for European regulatory purposes, and injected into the chamber. The relative concentrations of oxides of nitrogen (NOx) and total hydrocarbon (THC) during the aging of emissions inside the chamber were controlled using an injection system developed as a part of the new mobile chamber set up. Total OA (POA + SOA) emission factors of (370 ± 18) × 10-3 g kg-1 fuel, or (14.6 ± 0.8) × 10-3 g km-1, after aging, were calculated from concentrations measured inside the smog chamber during two experiments. The average SOA/POA ratio for the two experiments was 15.1, a much larger increase than has previously been seen for diesel vehicles, where smog chamber studies have found SOA/POA ratios of 1.3-1.7. Due to this SOA formation, carbonaceous particulate matter (PM) emissions from a gasoline vehicle may approach those of a diesel vehicle of the same class. Furthermore, with the advent of emission controls requiring the use of diesel particle filters, gasoline vehicle emissions

  18. Light extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometers

    NASA Astrophysics Data System (ADS)

    Varma, R. M.; Ball, S. M.; Brauers, T.; Dorn, H.-P.; Heitmann, U.; Jones, R. L.; Platt, U.; Pöhler, D.; Ruth, A. A.; Shillings, A. J. L.; Thieser, J.; Wahner, A.; Venables, D. S.

    2013-11-01

    Broadband optical cavity spectrometers are maturing as a technology for trace-gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulfate particles, the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using the Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

  19. Light extinction by Secondary Organic Aerosol: an intercomparison of three broadband cavity spectrometers

    NASA Astrophysics Data System (ADS)

    Varma, R. M.; Ball, S. M.; Brauers, T.; Dorn, H.-P.; Heitmann, U.; Jones, R. L.; Platt, U.; Pöhler, D.; Ruth, A. A.; Shillings, A. J. L.; Thieser, J.; Wahner, A.; Venables, D. S.

    2013-07-01

    Broadband optical cavity spectrometers are maturing as a technology for trace gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulphate particles the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.

  20. Effect of viscosity on photodegradation rates in complex secondary organic aerosol materials.

    PubMed

    Hinks, Mallory L; Brady, Monica V; Lignell, Hanna; Song, Mijung; Grayson, James W; Bertram, Allan K; Lin, Peng; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A

    2016-04-01

    This work explores the effect of environmental conditions on the photodegradation rates of atmospherically relevant, photolabile, organic molecules embedded in a film of secondary organic material (SOM). Three types of SOM were studied: α-pinene/O3 SOM (PSOM), limonene/O3 SOM (LSOM), and aged limonene/O3 obtained by exposure of LSOM to ammonia (brown LSOM). PSOM and LSOM were impregnated with 2,4-dinitrophenol (2,4-DNP), an atmospherically relevant molecule that photodegrades faster than either PSOM or LSOM alone, to serve as a probe of SOM matrix effects on photochemistry. Brown LSOM contains an unidentified chromophore that absorbs strongly at 510 nm and photobleaches upon irradiation. This chromophore served as a probe molecule for the brown LSOM experiments. In all experiments, either the temperature or relative humidity (RH) surrounding the SOM films was varied. The extent of photochemical reaction in the samples was monitored using UV-vis absorption spectroscopy. For all three model systems examined, the observed photodegradation rates were slower at lower temperatures and lower RH, conditions that make SOM more viscous. Additionally, the activation energies for photodegradation of each system were positively correlated with the viscosity of the SOM matrix as measured in poke-flow experiments. These activation energies were calculated to be 50, 24, and 17 kJ mol(-1) for 2,4-DNP in PSOM, 2,4-DNP in LSOM, and the chromophore in brown LSOM, respectively, and PSOM was found to be the most viscous of the three. These results suggest that the increased viscosity is hindering the motion of the molecules in SOM and is slowing down their respective photochemical reactions. PMID:26685987

  1. 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

  2. Oil sands operations as a large source of secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Liggio, John; Li, Shao-Meng; Hayden, Katherine; Taha, Youssef M.; Stroud, Craig; Darlington, Andrea; Drollette, Brian D.; Gordon, Mark; Lee, Patrick; Liu, Peter; Leithead, Amy; Moussa, Samar G.; Wang, Danny; O’Brien, Jason; Mittermeier, Richard L.; Brook, Jeffrey R.; Lu, Gang; Staebler, Ralf M.; Han, Yuemei; Tokarek, Travis W.; Osthoff, Hans D.; Makar, Paul A.; Zhang, Junhua; L. Plata, Desiree; Gentner, Drew R.

    2016-06-01

    Worldwide heavy oil and bitumen deposits amount to 9 trillion barrels of oil distributed in over 280 basins around the world, with Canada home to oil sands deposits of 1.7 trillion barrels. The global development of this resource and the increase in oil production from oil sands has caused environmental concerns over the presence of toxic compounds in nearby ecosystems and acid deposition. The contribution of oil sands exploration to secondary organic aerosol formation, an important component of atmospheric particulate matter that affects air quality and climate, remains poorly understood. Here we use data from airborne measurements over the Canadian oil sands, laboratory experiments and a box-model study to provide a quantitative assessment of the magnitude of secondary organic aerosol production from oil sands emissions. We find that the evaporation and atmospheric oxidation of low-volatility organic vapours from the mined oil sands material is directly responsible for the majority of the observed secondary organic aerosol mass. The resultant production rates of 45–84 tonnes per day make the oil sands one of the largest sources of anthropogenic secondary organic aerosols in North America. Heavy oil and bitumen account for over ten per cent of global oil production today, and this figure continues to grow. Our findings suggest that the production of the more viscous crude oils could be a large source of secondary organic aerosols in many production and refining regions worldwide, and that such production should be considered when assessing the environmental impacts of current and planned bitumen and heavy oil extraction projects globally.

  3. Oil sands operations as a large source of secondary organic aerosols.

    PubMed

    Liggio, John; Li, Shao-Meng; Hayden, Katherine; Taha, Youssef M; Stroud, Craig; Darlington, Andrea; Drollette, Brian D; Gordon, Mark; Lee, Patrick; Liu, Peter; Leithead, Amy; Moussa, Samar G; Wang, Danny; O'Brien, Jason; Mittermeier, Richard L; Brook, Jeffrey R; Lu, Gang; Staebler, Ralf M; Han, Yuemei; Tokarek, Travis W; Osthoff, Hans D; Makar, Paul A; Zhang, Junhua; Plata, Desiree L; Gentner, Drew R

    2016-06-01

    Worldwide heavy oil and bitumen deposits amount to 9 trillion barrels of oil distributed in over 280 basins around the world, with Canada home to oil sands deposits of 1.7 trillion barrels. The global development of this resource and the increase in oil production from oil sands has caused environmental concerns over the presence of toxic compounds in nearby ecosystems and acid deposition. The contribution of oil sands exploration to secondary organic aerosol formation, an important component of atmospheric particulate matter that affects air quality and climate, remains poorly understood. Here we use data from airborne measurements over the Canadian oil sands, laboratory experiments and a box-model study to provide a quantitative assessment of the magnitude of secondary organic aerosol production from oil sands emissions. We find that the evaporation and atmospheric oxidation of low-volatility organic vapours from the mined oil sands material is directly responsible for the majority of the observed secondary organic aerosol mass. The resultant production rates of 45-84 tonnes per day make the oil sands one of the largest sources of anthropogenic secondary organic aerosols in North America. Heavy oil and bitumen account for over ten per cent of global oil production today, and this figure continues to grow. Our findings suggest that the production of the more viscous crude oils could be a large source of secondary organic aerosols in many production and refining regions worldwide, and that such production should be considered when assessing the environmental impacts of current and planned bitumen and heavy oil extraction projects globally. PMID:27251281

  4. The Formation of Secondary Organic Aerosol from the Isoprene + OH Reaction in the Absence of NOx

    EPA Science Inventory

    The reaction of isoprene (C5H8) with hydroxyl radicals has been studied in the absence of nitrogen oxides (NOx) to determine physical and chemical characteristics of the secondary organic aerosol formed. Experiments were conducted using a smog ch...

  5. ß-CARYOPHYLLINIC ACID: AN ATMOSPHERIC TRACER FOR ß-CARYOPHYLLENE SECONDARY ORGANIC AEROSOL

    EPA Science Inventory

    The chemical compositions of ambient PM2.5 samples, collected in Research Triangle Park, North Carolina, USA, and a sample of secondary organic aerosol, formed by irradiating a mixture of the sesquiterpene, ß-caryophyllene, and oxides of nitrogen in a smog chamber, wer...

  6. Handbook on the Organization and Administration of a Student Job Placement Service for a Secondary School.

    ERIC Educational Resources Information Center

    Crawford, Lucy C.; Jewell, Lloyd M., Jr.

    Presented in four sections, this handbook was prepared to assist school administrators and placement service personnel in the organization and administration of a student job placement service for a secondary school. The handbook is primarily based on results obtained from developmental projects in a series of workshops provided to train placement…

  7. Graphic Organizers Applied to Secondary Algebra Instruction for Students with Learning Disorders

    ERIC Educational Resources Information Center

    Ives, Bob

    2007-01-01

    Students who have particular difficulty in mathematics are a growing concern for educators. Graphic organizers have been shown to improve reading comprehension and may be applied to upper level secondary mathematics content. In two systematic replications, one randomly assigned group was taught to solve systems of linear equations through direct…

  8. Optical Properties of Mixed Black Carbon, Inorganic and Secondary Organic Aerosols

    SciTech Connect

    Paulson, S E

    2012-05-30

    Summarizes the achievements of the project, which are divided into four areas: 1) Optical properties of secondary organic aerosols; 2) Development and of a polar nephelometer to measure aerosol optical properties and theoretical approaches to several optical analysis problems, 3) Studies on the accuracy of measurements of absorbing carbon by several methods, and 4) Environmental impacts of biodiesel.

  9. OZONE-ISOPRENE REACTION: RE-EXAMINATION OF THE FORMATION OF SECONDARY ORGANIC AEROSOL

    EPA Science Inventory

    The reaction of ozone and isoprene has been studied to examine physical and chemical characteristics of the secondary organic aerosol formed. Using a scanning mobility particle sizer, the volume distribution of the aerosol was found in the range 0.05 - 0.2 µm. The aerosol yield w...

  10. Elementary/Secondary Education Data Redesign Project: Letters, Comments, Reactions from Organizations and Agencies.

    ERIC Educational Resources Information Center

    1985

    The following organizations and agencies sent their suggestions and comments on the National Center for Education Statistics (NCES) Elementary/Secondary Education Data Redesign Project: American Association for Counseling and Development, American Association of Colleges for Teacher Education, American Library Association, Indiana University,…

  11. Pragmatic comprehension in secondary school-aged students with specific developmental language disorder.

    PubMed

    Rinaldi, W

    2000-01-01

    This study explores the hypothesis that there may be particular difficulties for secondary school students with specific developmental language disorder (SDLD) in understanding contextual, pragmatic meaning. Sixty-four SDLD students aged 11+ to 14+ years are compared with chronological-age-matched and language-age-matched non-impaired students. New procedures are used to examine comprehension of two types of ambiguity where the context determines speaker intention: inconsistent messages of emotion and multiple meanings in context. These types of ambiguity are evident in a range of communicative intent, e.g. sarcasm, idiomatic expression, deceit and humour. Preliminary study into adolescent language suggests that at this age there is a growing expectation for students to understand these kinds of communication, both in the classroom and socially. The study finds that the SDLD students were less able than both comparison groups to use context to understand implied meanings. Non-impaired children were also more able to rule out literal interpretations when they did not know the non-literal meaning. These findings were statistically significant. The implications for research and practice are discussed, including those of diagnostic assessment, in the light of the literature survey revealing that many currently available do not assess pragmatic meaning comprehension. There is a challenge to the view that disorders in the semantic and pragmatic domains necessarily co-occur, as suggested by the diagnostic category semantic-pragmatic disorder. PMID:10824222

  12. Photosensitized Formation of Secondary Organic Aerosols above the Air/Water Interface.

    PubMed

    Bernard, F; Ciuraru, R; Boréave, A; George, C

    2016-08-16

    In this study, we evaluated photosensitized chemistry at the air-sea interface as a source of secondary organic aerosols (SOA). Our results show that, in addition to biogenic emissions, abiotic processes could also be important in the marine boundary layer. Photosensitized production of marine secondary organic aerosol was studied in a custom-built multiphase atmospheric simulation chamber. The experimental chamber contained water, humic acid (1-10 mg L(-1)) as a proxy for dissolved organic matter, and nonanoic acid (0.1-10 mM), a fatty acid proxy which formed an organic film at the air-water interface. Dark secondary reaction with ozone after illumination resulted in SOA particle concentrations in excess of 1000 cm(-3), illustrating the production of unsaturated compounds by chemical reactions at the air-water interface. SOA numbers via photosensitization alone and in the absence of ozone did not exceed background levels. From these results, we derived a dependence of SOA numbers on nonanoic acid surface coverage and dissolved organic matter concentration. We present a discussion on the potential role of the air-sea interface in the production of atmospheric organic aerosol from photosensitized origins. PMID:27434860

  13. Estimating the Age Distribution of Oceanic Dissolved Organic Carbon

    NASA Astrophysics Data System (ADS)

    Follett, C. L.; Forney, D. C.; Repeta, D.; Rothman, D.

    2010-12-01

    Dissolved organic carbon (DOC) is a large, ubiquitous component of open ocean water at all depths and impacts atmospheric carbon dioxide levels at both short and long timescales. It is currently believed that oceanic DOC contains a multi-thousand-year-old refractory deep-water component which is mixed with a young labile component in surface waters. Unfortunately, the only evidence for this comes from a few isolated depth profiles of both DOC concentration and bulk radiocarbon. Although the profile data is consistent with a two-component mixing model, directly separating the two components has proven to be a challenge. We explore the validity of the two component mixing model by directly estimating the age distribution of oceanic DOC. The two-component model suggests that the age distribution is composed of two distinct peaks. In order to obtain an estimate of the age distribution we first record changes in both concentration and percent radiocarbon as a sample is oxidized under ultra-violet radiation [1]. We formulate a mathematical model relating the age distribution to these changes, assuming that they result from components of different radiocarbon age and UV-reactivity. This allows us to numerically invert the data and estimate the age distribution. We apply our procedure to DOC samples collected from three distinct depths (50, 500, and 2000 meters) in the north-central Pacific Ocean. [1] S.R. Beaupre, E.R.M. Druffel, and S. Griffin. A low-blank photochemical extraction system for concentration and isotopic analyses of marine dissolved organic carbon. Limnol. Oceanogr. Methods, 5:174-184, 2007.

  14. Contributions of Organic Vapors to Aerosol Aging and Growth

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Wang, L.; Khalizov, A.

    2009-05-01

    Atmospheric aerosols impair visibility and human health, interfere with radiative transfer, and alter cloud formation. The major contributors include sulfate and organic aerosols from anthropogenic and biogenic activities, which are produced through a multitude of complex multiphase atmospheric processes by photochemical oxidation of emitted sulfur dioxide and volatile organic compounds (VOCs) into less volatile forms and gas-to-particle conversion. Condensation of organic vapors onto the pre-existing atmospheric aerosols, followed by chemical reactions within the particles medium, is believed to be one of the major pathways that contribute to particle growth. Recent research has focused on the total mass increase on pre- existing seed particles, but the chemistry that determines the efficiency of organic uptake remains to be elucidated. This talk will focus on the growth of nano- to sub-micron sulfuric acid droplets exposed organic vapors. Experiments performed at different relative humidity and using different organic vapors (i.e., small alpha-dicarbonyls and large aldehydes) will be presented. The chemical mechanisms and size dependence of the particle growth will be demonstrated. Implications of the present results to aging and growth of aerosols under ambient conditions will be discussed.

  15. Ageing dynamics of ion bombardment induced self-organization processes

    PubMed Central

    Bikondoa, Oier; Carbone, Dina; Chamard, Virginie; Metzger, Till Hartmut

    2013-01-01

    Instabilities caused during the erosion of a surface by an ion beam can lead to the formation of self-organized patterns of nanostructures. Understanding the self-organization process requires not only the in-situ characterization of ensemble averaged properties but also probing the dynamics. This can be done with the use of coherent X-rays and analyzing the temporal correlations of the scattered intensity. Here, we show that the dynamics of a semiconductor surface nanopatterned by normal incidence ion beam sputtering are age-dependent and slow down with sputtering time. This work provides a novel insight into the erosion dynamics and opens new perspectives for the understanding of self-organization mechanisms. PMID:23685386

  16. Effect of hydrophilic organic seed aerosols on secondary organic aerosol formation from ozonolysis of α-pinene.

    PubMed

    Song, Chen; Zaveri, Rahul A; Shilling, John E; Alexander, M Lizabeth; Newburn, Matt

    2011-09-01

    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 volatile organic compound product will increase as the mass loading of preexisting organic aerosol increases. In a previous work, we showed that the presence of model hydrophobic primary organic aerosol (POA) had no detectable effect on the SOA yields from ozonolysis of α-pinene, suggesting that the condensing SOA compounds form a separate phase from the preexisting POA. However, a substantial faction of atmospheric aerosol is composed of polar, hydrophilic organic compounds. In this work, we investigate the effects of model hydrophilic organic aerosol (OA) species such as fulvic acid, adipic acid, and citric acid on the gas-particle partitioning of SOA from α-pinene ozonolysis. The results show that only citric acid seed significantly enhances the absorption of α-pinene SOA into the particle-phase. The other two seed particles have a negligible effect on the α-pinene SOA yields, suggesting that α-pinene SOA forms a well-mixed organic aerosol phase with citric acid and 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 OA species. PMID:21790137

  17. Soil organic carbon pools in olive groves of different age

    NASA Astrophysics Data System (ADS)

    Massaccesi, Luisa; De Feudis, Mauro; Nasini, Luigi; Regni, Luca; D'Ascoli, Rosaria; Castaldi, Simona; Proietti, Primo; Agnelli, Alberto

    2016-04-01

    In the last years, the practices which favor the increase of soil organic carbon in the agroecosystem have been widely studied because of their influence on the reduction of atmospheric CO2 (Lal, 1993; Schlesinger, 2000). The accumulation of the organic carbon into the soil depends to a great extent upon climate and pedological properties (Burke et al., 1989; Miller et al., 1994), although in the agricultural soils the cultivation system also plays a key role. The olive grove might potentially represent a relevant land use to improve C sequestration in soil, but there are few data available to support this hypothesis. In a study site located in central Italy (Deruta, PG), we analyzed the soil organic carbon (SOC) pools in two olive groves of different age (7 and 30 years) and, as control, in a site adjacent to the groves cropped with cereals for at least 30 years. With the aim to isolate and quantify the active, intermediate and passive functional SOC pools in the olive groves and in the control, we used a combined physical and chemical fractionation method (Zimmermann et al., 2007). The main results shown that the total organic carbon content in the Ap horizons was the highest in the 30-years-old olive grove, followed by the 7-years-old olive grove, and then by the control soil. The content of active C, in form of particulate organic matter (POM) and water soluble organic matter (WEOM), was greater in the olive grove compared to the control soil and increase with the age of the grove. About the amount of C in the intermediate and passive pools, no significant differences were found among the olive groves and the control. These preliminary results indicated that the greater total organic C content occurred in the 30-year-old olive grove with respect to the 7-years-old grove and the control, has to be ascribed to the greater content of active organic matter (POM and WEOM), and not to the accumulation in soil of organic C in a more stabilised form.

  18. The contributions of biomass burning to primary and secondary organics: A case study in Pearl River Delta (PRD), China.

    PubMed

    Wang, BaoLin; Liu, Ying; Shao, Min; Lu, SiHua; Wang, Ming; Yuan, Bin; Gong, ZhaoHeng; He, LingYan; Zeng, LiMin; Hu, Min; Zhang, YuanHang

    2016-11-01

    Synchronized online measurements of gas- and particle- phase organics including non-methane hydrocarbons (NMHCs), oxygenated volatile organic compounds (OVOCs) and submicron organic matters (OM) were conducted in November 2010 at Heshan, Guangdong provincial supersite, China. Several biomass burning events were identified by using acetonitrile as a tracer, and enhancement ratios (EnRs) of organics to carbon monoxide (CO) obtained from this work generally agree with those from rice straw burning in previous studies. The influences of biomass burning on NMHCs, OVOCs and OM were explored by comparing biomass burning impacted plumes (BB plumes) and non-biomass burning plumes (non-BB plumes). A photochemical age-based parameterization method was used to characterize primary emission and chemical behavior of those three organic groups. The emission ratios (EmRs) of NMHCs, OVOCs and OM to CO increased by 27-71%, 34-55% and 67% in BB plumes, respectively, in comparison with non-BB plumes. The estimated formation rate of secondary organic aerosol (SOA) in BB plumes was found to be 24% faster than non-BB plumes. By applying the above emission ratios to the whole PRD, the annual emissions of VOCs and OM from open burning of crop residues would be 56.4 and 3.8Gg in 2010 in PRD, respectively. PMID:27371770

  19. Anxiety, Self-Esteem and Coping with Stress in Secondary School Students in Relation to Involvement in Organized Sports

    PubMed Central

    DOLENC, Petra

    2015-01-01

    Aim The objective of the study was to examine self-esteem, anxiety level and coping strategies among secondary school students in relation to their involvement in organized sports. Methods The sample included 280 Slovenian male and female secondary school students aged between 15 and 19 years. The participants completed The Adolescent Coping Scale, the Spielberger State-Trait Anxiety Inventory, and the PSDQ Selfesteem Scale. Results Participants engaged in organized sports exhibited higher self-esteem scores and lower anxiety scores in comparison to non-sport participants. Differences between the two groups have also been identified with respect to the use of certain coping strategies. Sport participants reported more productive coping than non-sport participants, which represents an active and problem-focused approach to dealing with everyday problems. Gender differences in the referred variables have also been studied, with female athletes exhibiting higher levels of anxiety than male athletes. Female participants were also found to use more non-productive coping than males, focused mainly on reducing emotional effects of stress. Conclusions Organized youth sports have an important role in improving and maintaining a favorable sense of self-worth, reducing anxiety, and promoting productive coping strategies in adolescents when dealing with everyday problems.

  20. Secondary organic aerosol origin in an urban environment: influence of biogenic and fuel combustion precursors.

    PubMed

    Minguillón, M C; Pérez, N; Marchand, N; Bertrand, A; Temime-Roussel, B; Agrios, K; Szidat, S; van Drooge, B; Sylvestre, A; Alastuey, A; Reche, C; Ripoll, A; Marco, E; Grimalt, J O; Querol, X

    2016-07-18

    Source contributions of organic aerosol (OA) are still not fully understood, especially in terms of quantitative distinction between secondary OA formed from anthropogenic precursors vs. that formed from natural precursors. In order to investigate the OA origin, a field campaign was carried out in Barcelona in summer 2013, including two periods characterized by low and high traffic conditions. Volatile organic compound (VOC) concentrations were higher during the second period, especially aromatic hydrocarbons related to traffic emissions, which showed a marked daily cycle peaking during traffic rush hours, similarly to black carbon (BC) concentrations. Biogenic VOC (BVOC) concentrations showed only minor changes from the low to the high traffic period, and their intra-day variability was related to temperature and solar radiation cycles, although a decrease was observed for monoterpenes during the day. The organic carbon (OC) concentrations increased from the first to the second period, and the fraction of non-fossil OC as determined by (14)C analysis increased from 43% to 54% of the total OC. The combination of (14)C analysis and Aerosol Chemical Speciation Monitor (ACSM) OA source apportionment showed that the fossil OC was mainly secondary (>70%) except for the last sample, when the fossil secondary OC only represented 51% of the total fossil OC. The fraction of non-fossil secondary OC increased from 37% of total secondary OC for the first sample to 60% for the last sample. This enhanced formation of non-fossil secondary OA (SOA) could be attributed to the reaction of BVOC precursors with NOx emitted from road traffic (or from its nocturnal derivative nitrate that enhances night-time semi-volatile oxygenated OA (SV-OOA)), since NO2 concentrations increased from 19 to 42 μg m(-3) from the first to the last sample. PMID:27119273

  1. Functional group composition of organic aerosol from combustion emissions and secondary processes at two contrasted urban environments

    NASA Astrophysics Data System (ADS)

    El Haddad, Imad; Marchand, Nicolas; D'Anna, Barbara; Jaffrezo, Jean Luc; Wortham, Henri

    2013-08-01

    The quantification of major functional groups in atmospheric organic aerosol (OA) provides a constraint on the types of compounds emitted and formed in atmospheric conditions. This paper presents functional group composition of organic aerosol from two contrasted urban environments: Marseille during summer and Grenoble during winter. Functional groups were determined using a tandem mass spectrometry approach, enabling the quantification of carboxylic (RCOOH), carbonyl (RCOR‧), and nitro (RNO2) functional groups. Using a multiple regression analysis, absolute concentrations of functional groups were combined with those of organic carbon derived from different sources in order to infer the functional group contents of different organic aerosol fractions. These fractions include fossil fuel combustion emissions, biomass burning emissions and secondary organic aerosol (SOA). Results clearly highlight the differences between functional group fingerprints of primary and secondary OA fractions. OA emitted from primary sources is found to be moderately functionalized, as about 20 carbons per 1000 bear one of the functional groups determined here, whereas SOA is much more functionalized, as in average 94 carbons per 1000 bear a functional group under study. Aging processes appear to increase both RCOOH and RCOR‧ functional group contents by nearly one order of magnitude. Conversely, RNO2 content is found to decrease with photochemical processes. Finally, our results also suggest that other functional groups significantly contribute to biomass smoke and SOA. In particular, for SOA, the overall oxygen content, assessed using aerosol mass spectrometer measurements by an O:C ratio of 0.63, is significantly higher than the apparent O:C* ratio of 0.17 estimated based on functional groups measured here. A thorough examination of our data suggests that this remaining unexplained oxygen content can be most probably assigned to alcohol (ROH), organic peroxides (ROOH

  2. Reactivity of NaCl with Secondary Organic Acids: An Important Mechanism of the Chloride Depletion in Sea Salt Particles Mixed with Organic Materials

    NASA Astrophysics Data System (ADS)

    Wang, B.; Laskin, A.; Kelly, S.; Gilles, M. K.; Shilling, J. E.; Zelenyuk, A.; Wilson, J. M.; Tivanski, A.

    2012-12-01

    Sea salt particles, one of the major sources of atmospheric aerosols, undergo complex multi-phase reactions and have profound consequences on their physical and chemical properties, thus on climate. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of sea salt chlorides with inorganic acids, such as nitric and sulfuric acids. Some studies have also showed that the chloride deficit cannot be fully compensated for this mechanism. We present an important pathway contributing to this chloride depletion: reactions of weak organic acids with sea salt particles. NaCl particles internally mixed with secondary organic materials generated from the reactions of limonene and alpha-pinene with ozone served as surrogates for sea salt particles mixed with organic materials. Chemical imaging analysis of these particles was conducted using complementary techniques including computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX), scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and micro-fourier transform infrared spectroscopy (micro-FTIR). Substantial chloride depletion and formation of organic salts were observed along with distinctive changes in particle morphology after hydration/dehydration processes. The results indicate that secondary organic acids can effectively react with NaCl particles resulting in displacement of chloride and release of gaseous HCl. This is consistent with a recent field study showing chloride depletion in sea salt particles mixed with organic materials which cannot be fully compensated by inorganic acid displacement. Although the formation of the organic salts is not thermodynamically favored in bulk aqueous solution, these reactions are driven by the high volatility and evaporation of gaseous HCl in particles, especially during hydration/dehydration processes. The

  3. Quantitative evaluation of emission control of primary and secondary organic aerosol sources during Beijing 2008 Olympics

    NASA Astrophysics Data System (ADS)

    Guo, S.; Hu, M.; Guo, Q.; Zhang, X.; Schauer, J. J.; Zhang, R.

    2012-12-01

    To explore the primary and secondary sources of fine organic particles after the aggressive implementation of air pollution controls during 2008 Beijing Olympic Games, 12-h PM2.5 concentrations were measured at one urban and one upwind rural site during the CAREBeijing-2008 (Campaigns of Air quality REsearch in Beijing and surrounding region) summer field campaign. The PM2.5 concentrations were 72.5±43.6μg m3 and 64.3±36.2μg m-3 at the urban site and rural site, respectively, which were the lowest in recent years due to the implementation of drastic control measures and favorable weather conditions. Five primary and four secondary fine organic particle sources were quantified using a CMB (chemical mass balance) model and tracer-yield method. Compared with previous studies in Beijing, the contribution of vehicle emission increased, with diesel engines contributing 16.2±5.9% and 14.5±4.1% to the total organic carbon (OC) concentrations and gasoline vehicles accounting for 10.3±8.7% and 7.9±6.2% of the OC concentrations at two sites. Due to the implementation of emission control measures, the OC concentrations from important primary sources have been reduced, and secondary formation has become an important contributor to fine organic aerosols. Compared with the non-controlled period, primary vehicle contributions were reduced by 30% and 24% in the urban and regional area, and reductions in the contribution from coal combustion were 57% and 7%, respectively. These results demonstrate the emission control measures significantly alleviated the primary organic particle pollution in and around Beijing. However, the control effectiveness of secondary organic particles was not significant.

  4. Contribution of Primary and Secondary Sources to Organic Aerosol and PM2.5 at SEARCH Network Sites

    EPA Science Inventory

    Chemical tracer methods for determining contributions to primary organic aerosol (POA) are fairly well established, whereas similar techniques for secondary organic aerosol (SOA), inherently complicated by time-dependent atmospheric processes, are only beginning to be studied. La...

  5. Organic tanks safety program FY95 waste aging studies

    SciTech Connect

    Camaioni, D.M.; Samuels, W.D.; Clauss, S.A.; Lenihan, B.D.; Wahl, K.L.; Campbell, J.A.; Shaw, W.J.

    1995-09-01

    This report gives the second year`s findings of a study of how thermal and radiological processes may change the composition of organic compounds in the underground tanks at Hanford. Efforts were focused on the global reaction kinetics in a simulated waste exposed to {gamma} rays and the reactions of organic radicals with nitrite ion. The gas production is predominantly radiolytic. Decarboxylation of carboxylates is probably an aging pathway. TBP was totaly consumed in almost every run. Radiation clearly accelerated consumption of the other compounds. EDTA is more reactive than citrate. Oximes and possibly organic nitro compounds are key intermediates in the radiolytic redox reactions of organic compounds with nitrate/nitrite. Observations are consistent with organic compounds being progressively degraded to compounds with greater numbers of C-O bonds and fewer C-H and C-C bonds, resulting in an overall lower energy content. If the radwaste tanks are adequately ventilated and continually dosed by radioactivity, their total energy content should have declined. Level of risk depends on how rapidly carboxylate salts of moderate energy content (including EDTA fragments) degrade to low energy oxalate and formate.

  6. Gas uptake and chemical aging of semisolid organic aerosol particles

    PubMed Central

    Shiraiwa, Manabu; Ammann, Markus; Koop, Thomas; Pöschl, Ulrich

    2011-01-01

    Organic substances can adopt an amorphous solid or semisolid state, influencing the rate of heterogeneous reactions and multiphase processes in atmospheric aerosols. Here we demonstrate how molecular diffusion in the condensed phase affects the gas uptake and chemical transformation of semisolid organic particles. Flow tube experiments show that the ozone uptake and oxidative aging of amorphous protein is kinetically limited by bulk diffusion. The reactive gas uptake exhibits a pronounced increase with relative humidity, which can be explained by a decrease of viscosity and increase of diffusivity due to hygroscopic water uptake transforming the amorphous organic matrix from a glassy to a semisolid state (moisture-induced phase transition). The reaction rate depends on the condensed phase diffusion coefficients of both the oxidant and the organic reactant molecules, which can be described by a kinetic multilayer flux model but not by the traditional resistor model approach of multiphase chemistry. The chemical lifetime of reactive compounds in atmospheric particles can increase from seconds to days as the rate of diffusion in semisolid phases can decrease by multiple orders of magnitude in response to low temperature or low relative humidity. The findings demonstrate that the occurrence and properties of amorphous semisolid phases challenge traditional views and require advanced formalisms for the description of organic particle formation and transformation in atmospheric models of aerosol effects on air quality, public health, and climate. PMID:21690350

  7. Detailed Chemical Characterization of Unresolved Complex Mixtures (UCM) inAtmospheric Organics: Insights into Emission Sources, Atmospheric Processing andSecondary Organic Aerosol Formation

    EPA Science Inventory

    Recent studies suggest that semivolatile organic compounds (SVOCs) are important precursors to secondary organic aerosol (SOA) in urban atmospheres. However, knowledge of the chemical composition of SVOCs is limited by current analytical techniques, which are typically unable to...

  8. Sources, Ages, and Alteration of Organic Matter in Estuaries

    NASA Astrophysics Data System (ADS)

    Canuel, Elizabeth A.; Hardison, Amber K.

    2016-01-01

    Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters.

  9. Sources, Ages, and Alteration of Organic Matter in Estuaries.

    PubMed

    Canuel, Elizabeth A; Hardison, Amber K

    2016-01-01

    Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters. PMID:26407145

  10. Impact of biological filtrations for organic micropollutants and polyfluoroalkyl substances removal from secondary effluent.

    PubMed

    Pramanik, Biplob Kumar; Pramanik, Sagor Kumar; Suja, Fatihah

    2016-08-01

    The impact of biological activated carbon (BAC), sand filtration (SF) and biological aerated filter (BAF) for removal of the selected organic micropollutants and polyfluoroalkyl substances (PFASs) from secondary effluent was studied. BAC led to greater removal of dissolved organic carbon (43%) than BAF (30%) which in turn was greater than SF (24%). All biological filtration systems could effectively remove most of the selected organic micropollutants, and there was a greater removal of these micropollutants by BAC (76-98%) than BAF (70-92%) or SF (68-90%). It was found that all treatment was effective for removal of the hydrophobic (log D > 3.2) and readily biodegradable organic micropollutants. The major mechanism for the removal of these molecules was biodegradation by the micro-organism and sorption by the biofilm. Compared to organic micropollutants removal, there was a lower removal of PFASs by all treatments, and BAF and SF had a considerably lower removal than BAC treatment. The better removal for all molecule types by BAC was due to additional adsorption capacity by the activated carbon. This study demonstrated that the BAC process was most effective in removing organic micropollutants present in the secondary effluent. PMID:26695189

  11. Limited influence of dry deposition of semivolatile organic vapors on secondary organic aerosol formation in the urban plume

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    The dry deposition of volatile organic compounds (VOCs) and its impact on secondary organic aerosols (SOA) are investigated in the Mexico City plume. Gas-phase chemistry and gas-particle partitioning of oxygenated VOCs are modeled with the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) from C3 to C25 alkanes, alkenes, and light aromatics. Results 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. Dry deposition competes with the gas-particle uptake, and only gases with fewer than ~12 carbons dry deposit while longer species partition to SOA. Because dry deposition of submicron aerosols is slow, condensation onto particles protects organic gases from deposition, thus increasing their atmospheric burden and lifetime. In the absence of this condensation, ~50% of the regionally produced mass would have been dry deposited.

  12. Volatility dependence of Henry's law constants of condensable organics: Application to estimate depositional loss of secondary organic aerosols

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    The water solubility of oxidation intermediates of volatile organic compounds that can condense to form secondary organic aerosol (SOA) is largely unconstrained in current chemistry-climate models. We apply the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere to calculate Henry's law constants for these intermediate species. Results show a strong negative correlation between Henry's law constants and saturation vapor pressures. Details depend on precursor species, extent of photochemical processing, and NOx levels. Henry's law constants as a function of volatility are made available over a wide range of vapor pressures for use in 3-D models. In an application using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) over the U.S. in summer, we find that dry (and wet) deposition of condensable organic vapors leads to major reductions in SOA, decreasing surface concentrations by ~50% (10%) for biogenic and ~40% (6%) for short chain anthropogenic precursors under the considered volatility conditions.

  13. Age of Giordano Bruno crater as deduced from the morphology of its secondaries at the Luna 24 landing site

    NASA Astrophysics Data System (ADS)

    Basilevsky, A. T.; Head, J. W.

    2012-12-01

    We undertook a photogeologic study of Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images of the ejecta of the very young 22-km diameter crater Giordano Bruno (GB) and for the Luna 24 landing site region, where secondary craters from Giordano Bruno are observed. Using the technique of Basilevsky (1976) for estimating the absolute ages of small lunar craters based on their morphologic prominence and size, craters near the Luna 24 site considered to be secondaries of Giordano Bruno crater and craters superposed on ejecta of Giordano Bruno crater are found to have approximately the same age: somewhere between 5 and 10 m.y. This suggests that the craters at the Luna 24 site are indeed secondaries of GB crater and that this age range is an estimate for the time of GB crater formation. Our results generally agree with estimates derived from counts of small craters superposed on GB ejecta: 1-10 m.y. and with the exposure age of one of the samples derived from Zone I of the Luna 24 core. Plescia et al. (2010b) interpreted a large fraction of the craters superposed on GB ejecta and floor not as primary craters, but rather as secondary craters formed from the GB event itself. On this basis, it was postulated that GB may be formed by an historic impact. Our new data and analysis do not support an age as young as historical. The general agreement of our results for age determination for the GB secondaries of the Luna 24 area, and for craters superposed on the GB ejecta, with the age estimate based on crater count and with the mentioned exposition age of one of the Luna 24 samples, also validates the technique of Basilevsky (1976). A special study of the Luna 24 samples should be undertaken designed to find records of the formation age of the crater on whose rim Luna 24 landed, thus better constraining the age of GB crater.

  14. Campaign 1.7 Pu Aging. Development of Time of Flight Secondary Ion Mass Spectroscopy

    SciTech Connect

    Venhaus, Thomas J.

    2015-09-09

    The first application of Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) to an aged plutonium surface has resulted in a rich set of surface chemistry data, as well as some unexpected results. FY15 was highlighted by not only the first mapping of hydrogen-containing features within the metal, but also a prove-in series of experiments using the system’s Sieverts Reaction Cell. These experiments involved successfully heating the sample to ~450 oC for nearly 24 hours while the sample was dosed several times with hydrogen, followed by an in situ ToF-SIMS analysis. During this year, the data allowed for better and more consistent identification of the myriad peaks that result from the SIMS sputter process. In collaboration with the AWE (U.K), the system was also fully aligned for sputter depth profiling for future experiments.

  15. Aged Riverine Particulate Organic Carbon in Four UK Catchments

    NASA Astrophysics Data System (ADS)

    Adams, Jessica; Tipping, Edward; Bryant, Charlotte; Helliwell, Rachel; Toberman, Hannah; Quinton, John

    2016-04-01

    The riverine transport of particulate organic matter (POM) is a significant flux in the carbon cycle, and affects macronutrients and contaminants. We used radiocarbon to characterise POM at 9 riverine sites of four UK catchments (Avon, Conwy, Dee, Ribble) over a one-year period. High-discharge samples were collected on three or four occasions at each site. Suspended particulate matter (SPM) was obtained by centrifugation, and the samples were analysed for carbon isotopes. Concentrations of SPM and SPM organic carbon (OC) contents were also determined, and were found to have a significant negative correlation. For the 7 rivers draining predominantly rural catchments, PO14C values, expressed as percent modern carbon absolute (pMC), varied little among samplings at each site, and there was no significant difference in the average values among the sites. The overall average PO14C value for the 7 sites of 91.2 pMC corresponded to an average age of 680 14C years, but this value arises from the mixing of differently-aged components, and therefore significant amounts of organic matter older than the average value are present in the samples. Although topsoil erosion is probably the major source of the riverine POM, the average PO14C value is appreciably lower than topsoil values (which are typically 100 pMC). This is most likely explained by inputs of older subsoil OC from bank erosion, or the preferential loss of high-14C topsoil organic matter by mineralisation during riverine transport. The significantly lower average PO14C of samples from the River Calder (76.6 pMC), can be ascribed to components containing little or no radiocarbon, derived either from industrial sources or historical coal mining, and this effect is also seen in the River Ribble, downstream of its confluence with the Calder. At the global scale, the results significantly expand available information for PO14C in rivers draining catchments with low erosion rates.

  16. Aged riverine particulate organic carbon in four UK catchments.

    PubMed

    Adams, Jessica L; Tipping, Edward; Bryant, Charlotte L; Helliwell, Rachel C; Toberman, Hannah; Quinton, John

    2015-12-01

    The riverine transport of particulate organic matter (POM) is a significant flux in the carbon cycle, and affects macronutrients and contaminants. We used radiocarbon to characterise POM at 9 riverine sites of four UK catchments (Avon, Conwy, Dee, Ribble) over a one-year period. High-discharge samples were collected on three or four occasions at each site. Suspended particulate matter (SPM) was obtained by centrifugation, and the samples were analysed for carbon isotopes. Concentrations of SPM and SPM organic carbon (OC) contents were also determined, and were found to have a significant negative correlation. For the 7 rivers draining predominantly rural catchments, PO14C values, expressed as percent modern carbon absolute (pMC), varied little among samplings at each site, and there was no significant difference in the average values among the sites. The overall average PO14C value for the 7 sites of 91.2 pMC corresponded to an average age of 680 14C years, but this value arises from the mixing of differently-aged components, and therefore significant amounts of organic matter older than the average value are present in the samples. Although topsoil erosion is probably the major source of the riverine POM, the average PO14C value is appreciably lower than topsoil values (which are typically 100 pMC). This is most likely explained by inputs of older subsoil OC from bank erosion, or the preferential loss of high-14C topsoil organic matter by mineralisation during riverine transport. The significantly lower average PO14C of samples from the River Calder (76.6 pMC), can be ascribed to components containing little or no radiocarbon, derived either from industrial sources or historical coal mining, and this effect is also seen in the River Ribble, downstream of its confluence with the Calder. At the global scale, the results significantly expand available information for PO14C in rivers draining catchments with low erosion rates. PMID:26254066

  17. OH-initiated heterogeneous aging of highly oxidized organic aerosol

    SciTech Connect

    Kessler, Sean H.; Nah, Theodora; Daumit, Kelly E.; Smith, Jared D.; Leone, Stephen R.; Kolb, Charles E.; Worsnop, Douglas R.; Wilson, Kevin R.; Kroll, Jesse H.

    2011-12-05

    The oxidative evolution (“aging”) of organic species in the atmosphere is thought to have a major influence on the composition and properties of organic particulate matter, but remains poorly understood, particularly for the most oxidized fraction of the aerosol. Here we measure the kinetics and products of the heterogeneous oxidation of highly oxidized organic aerosol, with an aim of better constraining such atmospheric aging processes. Submicron particles composed of model oxidized organics—1,2,3,4-butanetetracarboxylic acid (C{sub 8}H{sub 10}O{sub 8}), citric acid (C{sub 6}H{sub 8}O{sub 7}), tartaric acid (C{sub 4}H{sub 6}O{sub 6}), and Suwannee River fulvic acid—were oxidized by gas-phase OH in a flow reactor, and the masses and elemental composition of the particles were monitored as a function of OH exposure. In contrast to our previous studies of less-oxidized model systems (squalane, erythritol, and levoglucosan), particle mass did not decrease significantly with heterogeneous oxidation. Carbon content of the aerosol always decreased somewhat, but this mass loss was approximately balanced by an increase in oxygen content. The estimated reactive uptake coefficients of the reactions range from 0.37 to 0.51 and indicate that such transformations occur at rates corresponding to 1-2 weeks in the atmosphere, suggesting their importance in the atmospheric lifecycle of organic particulate matter.

  18. Environmental Drivers of Global Riverine Organic Carbon Age

    NASA Astrophysics Data System (ADS)

    McIntosh, H.; Buffam, I. D.; McCallister, S. L.

    2015-12-01

    The transport of terrestrial organic carbon (OC) to downstream systems via the fluvial network represents a "leakage" of terrestrial net primary production. The age of OC exported ranges from modern OC, derived from surficial soils and leaf litter, to ancient OC that had been stored for millennia on land. The age and ultimately the fate of this OC has ramifications for both the terrestrial carbon balance and the anthropogenic CO2 budget. Consequently, it is critical to understand the environmental and landscape associated factors that influence the age of OC laterally transferred to aquatic systems. We compiled radiocarbon data for both dissolved OC (DOC) (n = 670) and particulate OC (POC) (n = 722) for both rivers and streams. Sampling locations (n = 382) and their associated watersheds (1x10-2 km2 to 4.7x106 km2) encompassed a range from 38.7 oS to 74.9 oN. These radiocarbon values were paired with associated ancillary data, when available (OC concentration, δ13C), and subsequently combined with a spatial dataset developed in ArcGIS for corresponding watersheds. The spatial dataset contained a range of landscape parameters including mean elevation, relief, mean slope, and stream order as well as soil typology and land use. Δ14CDOC ranged from -974 ‰ to +383 ‰ (mean = 3 ‰, standard deviation (s.d.) = 150 ‰) and Δ14CPOC ranged from -992 ‰ to +227 ‰ (mean = -234 ‰, s.d. = 253 ‰) demonstrating a trend of younger DOC relative to its particulate counterpart. Landscape characteristics were first analyzed for their influence on radiocarbon ages of DOC and POC at a global scale. The data were then aggregated by biome (n = 14) to assess the role of regional environmental characteristics (i.e. precipitation, temperature, soil organic carbon) on DOC and POC age. Models were derived to determine the principle drivers of the radiocarbon age of OC in streams and rivers, among the landscape and environmental characteristics, for each biome.

  19. Contribution of secondary condensable organics to new particle formation: A case study in Houston, Texas

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Zhang, Renyi; Collins, Don; Li, Guohui

    2006-08-01

    We report aerosol simulations using the EPA's Models-3 Community Multiscale Air Quality model (CMAQ) and ground-based and aircraft aerosol measurements to investigate new particle formation in Houston, Texas. The aerosol measurements reveal elevated ultrafine particles that reach the highest value in the afternoon, indicating prominent new particle formation. Simulations of the binary H2SO4-H2O nucleation predict an order of magnitude lower concentrations for aerosols near 10 nm than the measurements. A parameterized nucleation scheme that accounts for the enhanced nucleation effect of secondary condensable organics is incorporated into the Models-3/CMAQ. The organic nucleation scheme predicts the number concentrations in agreement with the measurements during the daytime. The diurnal variation is well reproduced in the simulations including the organic nucleation scheme. Comparison with the aircraft measurements also shows that the organic nucleation scheme produces good predictions of the altitude-dependent number size distributions of the ultrafine particles. The results corroborate the importance of secondary condensable organics in new particle formation when sulfate and organics are abundant.

  20. Modeling Secondary Organic Aerosols over Europe: Impact of Activity Coefficients and Viscosity

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Sartelet, K.; Couvidat, F.

    2014-12-01

    Semi-volatile organic species (SVOC) can condense on suspended particulate materials (PM) in the atmosphere. The modeling of condensation/evaporation of SVOC often assumes that gas-phase and particle-phase concentrations are at equilibrium. However, recent studies show that secondary organic aerosols (SOA) may not be accurately represented by an equilibrium approach between the gas and particle phases, because organic aerosols in the particle phase may be very viscous. The condensation in the viscous liquid phase is limited by the diffusion from the surface of PM to its core. Using a surrogate approach to represent SVOC, depending on the user's choice, the secondary organic aerosol processor (SOAP) may assume equilibrium or model dynamically the condensation/evaporation between the gas and particle phases to take into account the viscosity of organic aerosols. The model is implemented in the three-dimensional chemistry-transport model of POLYPHEMUS. In SOAP, activity coefficients for organic mixtures can be computed using UNIFAC for short-range interactions between molecules and AIOMFAC to also take into account the effect of inorganic species on activity coefficients. Simulations over Europe are performed and POLYPHEMUS/SOAP is compared to POLYPHEMUS/H2O, which was previously used to model SOA using the equilibrium approach with activity coefficients from UNIFAC. Impacts of the dynamic approach on modeling SOA over Europe are evaluated. The concentrations of SOA using the dynamic approach are compared with those using the equilibrium approach. The increase of computational cost is also evaluated.

  1. Assessment of secondary sources of Persistent Organic Pollutants in the Arctic

    NASA Astrophysics Data System (ADS)

    Pisso, Ignacio; Eckhardt, Sabine; Breivik, Knut

    2014-05-01

    Persistent organic pollutants (POPs) including highly toxic pesticides and other chemicals accumulate in living tissues and magnify in food chains. POPs are subject to long-range transport and hence represent a serious public health issue even in regions where their production is regulated. Rational control strategies require an understanding of the overall relationship between environmental emissions of contaminants and environmental / human exposure. In this study, we assess the relationships between environmental emissions and potential human exposure of organic contaminants with emphasis on long-range atmospheric transport. We investigate whether atmospheric levels of POPs measured at Zeppelin observatory in Svalbard since the early '90s are controlled by primary or secondary emissions. We present statistical indications that the measurements are affected by secondary ocean emissions and discuss the applicability of different inverse modeling approaches.

  2. Reactive Uptake of Ammonia to Secondary Organic Aerosols: Kinetics of Organonitrogen Formation

    NASA Astrophysics Data System (ADS)

    Liu, Yongchun; Liggio, John; Staebler, Ralf; Li, Shao-Meng

    2015-04-01

    Organonitrogen compounds originating from the heterogeneous uptake of NH3 or amines by secondary organic aerosol (SOA) has received significant attention recently. This is primarily due to its potential contribution to brown carbon (BrC), which can absorb solar radiation and affect climate. In addition, particle phase Organonitrogen species may represent a means of altering regional nitrogen cycles and/or nitrogen deposition patterns though the sequestering of ambient ammonia which is ultimately deposited downwind. Several reduced nitrogen forming heterogeneous reactions have previously been proposed, including Schiff base and/or Mannich reactions between NH3, ammonium salts or amines and organic carbonyl functional groups in particles. In order to assess and model the possible impact of Schiff base, Mannich or other N-forming reactions (via NH3) on the radiative forcing ability of ambient SOA and/or its impact on N-deposition, the kinetics of such heterogeneous reactions are required, and yet remain largely unknown. In the current study, the uptake kinetics of NH3 to form organonitrogen compounds in SOA derived from the ozonolysis of α-pinene and the OH oxidation of m-xylene is reported for the first time from experiments performed in a 9 m3 smog chamber equipped with a High Resolution Time-of-Flight Aerosol Mass Spectrometer. The results demonstrate that particle bound organonitrogen compounds are mainly formed by NH3 uptake onto newly formed SOA (~1 hr), but relatively little onto more aged SOA. The uptake coefficients of NH3 to form organonitrogen compounds (between 0-150 min) are on the order of 10-4-10-3 and are prominently dependent upon particle acidity. Following 6 hours of reaction, the total organonitrogen mass contributed up to 10.0±1.5 wt% and 31.5±4.4 wt% to the total SOA mass from the ozonolysis of α-pinene and OH oxidation of m-xylene. The influence of VOC precursors, seed particle acidity and gaseous NH3 concentration on the obtained uptake

  3. Changes in organic aerosol composition with aging inferred from aerosol mass spectra

    NASA Astrophysics Data System (ADS)

    Ng, N. L.; Canagaratna, M. R.; Jimenez, J. L.; Chhabra, P. S.; Seinfeld, J. H.; Worsnop, D. R.

    2011-07-01

    Organic aerosols (OA) can be separated with factor analysis of aerosol mass spectrometer (AMS) data into hydrocarbon-like OA (HOA) and oxygenated OA (OOA). We develop a new method to parameterize H:C of OOA in terms of f43 (ratio of m/z 43, mostly C2H3O+, to total signal in the component mass spectrum). Such parameterization allows for the transformation of large database of ambient OOA components from the f44 (mostly CO2+, likely from acid groups) vs. f43 space ("triangle plot") (Ng et al., 2010) into the Van Krevelen diagram (H:C vs. O:C) (Van Krevelen, 1950). Heald et al. (2010) examined the evolution of total OA in the Van Krevelen diagram. In this work total OA is deconvolved into components that correspond to primary (HOA and others) and secondary (OOA) organic aerosols. By deconvolving total OA into different components, we remove physical mixing effects between secondary and primary aerosols which allows for examination of the evolution of OOA components alone in the Van Krevelen space. This provides a unique means of following ambient secondary OA evolution that is analogous to and can be compared with trends observed in chamber studies of secondary organic aerosol formation. The triangle plot in Ng et al. (2010) indicates that f44 of OOA components increases with photochemical age, suggesting the importance of acid formation in OOA evolution. Once they are transformed with the new parameterization, the triangle plot of the OOA components from all sites occupy an area in Van Krevelen space which follows a ΔH:C/ΔO:C slope of ~ -0.5. This slope suggests that ambient OOA aging results in net changes in chemical composition that are equivalent to the addition of both acid and alcohol/peroxide functional groups without fragmentation (i.e. C-C bond breakage), and/or the addition of acid groups with fragmentation. These results provide a framework for linking the bulk aerosol chemical composition evolution to molecular-level studies.

  4. Direct evidence of atmospheric secondary organic aerosol formation in forest atmosphere through heteromolecular nucleation.

    PubMed

    Kavouras, Ilias G; Stephanou, Euripides G

    2002-12-01

    Atmospheric aerosols play a central role in climate and atmospheric chemistry. Organic matter frequently composes aerosol major fraction over continental areas. Reactions of natural volatile organic compounds, with atmospheric oxidants, are a key formation pathway of fine particles. The gas and particle atmospheric concentration of organic compounds directly emitted from conifer leaf epicuticular wax and of those formed through the photooxidation of alpha- and beta-pinene were simultaneously collected and measured in a conifer forest by using elaborated sampling and GC/ MS techniques. The saturation concentrations of acidic and carbonyl photooxidation products were estimated, by taking into consideration primary gas- and particle-phase organic species. Primary organic aerosol components represented an important fraction of the atmospheric gas-phase organic content Consequently, saturation concentrations of photooxidation products have been lowered facilitating new particle formation between molecules of photooxidation products and semi-volatile organic compounds. From the measured concentrations of the above-mentioned compounds, saturation concentrations (Csat,i) of alpha- and beta-pinene photooxidation products were calculated for nonideal conditions using a previously developed absorptive model. The results of these calculations indicated that primarily emitted organic species and ambient temperature play a crucial role in secondary organic aerosol formation. PMID:12523424

  5. Single-particle measurements of phase partitioning between primary and secondary organic aerosols.

    PubMed

    Robinson, Ellis Shipley; Donahue, Neil M; Ahern, Adam T; Ye, Qing; Lipsky, Eric

    2016-07-18

    Organic aerosols provide a measure of complexity in the urban atmosphere. This is because the aerosols start as an external mixture, with many populations from varied local sources, that all interact with each other, with background aerosols, and with condensing vapors from secondary organic aerosol formation. The externally mixed particle populations start to evolve immediately after emission because the organic molecules constituting the particles also form thermodynamic mixtures - solutions - in which a large fraction of the constituents are semi-volatile. The external mixtures are thus well out of thermodynamic equilibrium, with very different activities for many constituents, and yet also have the capacity to relax toward equilibrium via gas-phase exchange of semi-volatile vapors. Here we describe experiments employing quantitative single-particle mass spectrometry designed to explore the extent to which various primary organic aerosol particle populations can interact with each other or with secondary organic aerosols representative of background aerosol populations. These methods allow us to determine when these populations will and when they will not mix with each other, and then to constrain the timescales for that mixing. PMID:27092377

  6. Significant formation of water-insoluble secondary organic aerosols in semi-arid urban environment

    NASA Astrophysics Data System (ADS)

    Favez, Olivier; Sciare, Jean; Cachier, Hélène; Alfaro, Stéphane C.; Abdelwahab, Magdy M.

    2008-08-01

    Diurnal variations of submicron elemental carbon (EC), water-soluble organic carbon (WSOC) and water-insoluble organic carbon (WIOC) were investigated at an urban background site in Cairo (Egypt) from 23 March to 14 April 2005. Well-marked diurnal patterns, with minima during the traffic-influenced morning period (6:00-9:00) and maxima during the intense photochemical period (12:00-15:00), were observed for the WSOC/EC ratio and, more surprisingly, for the WIOC/EC ratio. Such diurnal variations suggest significant formation of both water-soluble and water-insoluble secondary organic aerosols during the afternoon. Applying the EC-tracer method, freshly-formed secondary organic carbon (fresh SOC) was found to possibly account for more than 50% of OC concentrations measured during the 12:00-15:00 period, and this fresh SOC was calculated to be mainly (~60%) composed of water-insoluble species. The latter (unexpected) result could be due to low ambient relative humidity as well as to the importance of anthropogenic volatile organic compounds in Cairo.

  7. Evidence of aqueous secondary organic aerosol formation from biogenic emissions in the North American Sonoran Desert

    PubMed Central

    Youn, Jong-Sang; Wang, Zhen; Wonaschütz, Anna; Arellano, Avelino; Betterton, Eric A.; Sorooshian, Armin

    2013-01-01

    This study examines the role of aqueous secondary organic aerosol formation in the North American Sonoran Desert as a result of intense solar radiation, enhanced moisture, and biogenic volatile organic compounds (BVOCs). The ratio of water-soluble organic carbon (WSOC) to organic carbon (OC) nearly doubles during the monsoon season relative to other seasons of the year. When normalized by mixing height, the WSOC enhancement during monsoon months relative to preceding dry months (May–June) exceeds that of sulfate by nearly a factor of 10. WSOC:OC and WSOC are most strongly correlated with moisture parameters, temperature, and concentrations of O3 and BVOCs. No positive relationship was identified between WSOC or WSOC:OC and anthropogenic tracers such as CO over a full year. This study points at the need for further work to understand the effect of BVOCs and moisture in altering aerosol properties in understudied desert regions. PMID:24115805

  8. Effects of aging on organic aerosol from open biomass burning smoke in aircraft and laboratory studies

    NASA Astrophysics Data System (ADS)

    Cubison, M. J.; Ortega, A. M.; Hayes, P. L.; Farmer, D. K.; Day, D.; Lechner, M. J.; Brune, W. H.; Apel, E.; Diskin, G. S.; Fisher, J. A.; Fuelberg, H. E.; Hecobian, A.; Knapp, D. J.; Mikoviny, T.; Riemer, D.; Sachse, G. W.; Sessions, W.; Weber, R. J.; Weinheimer, A. J.; Wisthaler, A.; Jimenez, J. L.

    2011-12-01

    Biomass burning (BB) is a large source of primary and secondary organic aerosols (POA and SOA). This study addresses the physical and chemical evolution of BB organic aerosols. Firstly, the evolution and lifetime of BB POA and SOA signatures observed with the Aerodyne Aerosol Mass Spectrometer are investigated, focusing on measurements at high-latitudes acquired during the 2008 NASA ARCTAS mission, in comparison to data from other field studies and from laboratory aging experiments. The parameter f60, the ratio of the integrated signal at m/z 60 to the total signal in the organic component mass spectrum, is used as a marker to study the rate of oxidation and fate of the BB POA. A background level of f60~0.3% ± 0.06% for SOA-dominated ambient OA is shown to be an appropriate background level for this tracer. Using also f44 as a tracer for SOA and aged POA and a surrogate of organic O:C, a novel graphical method is presented to characterise the aging of BB plumes. Similar trends of decreasing f60 and increasing f44 with aging are observed in most field and lab studies. At least some very aged BB plumes retain a clear f60 signature. A statistically significant difference in f60 between highly-oxygenated OA of BB and non-BB origin is observed using this tracer, consistent with a substantial contribution of BBOA to the springtime Arctic aerosol burden in 2008. Secondly, a summary is presented of results on the net enhancement of OA with aging of BB plumes, which shows large variability. The estimates of net OA gain range from ΔOA/ΔCO(mass) = -0.01 to ~0.05, with a mean ΔOA/POA ~19%. With these ratios and global inventories of BB CO and POA a global net OA source due to aging of BB plumes of ~8 ± 7 Tg OA yr-1 is estimated, of the order of 5 % of recent total OA source estimates. Further field data following BB plume advection should be a focus of future research in order to better constrain this potentially important contribution to the OA burden.

  9. Innervation of lymphoid organs and implications in development, aging, and autoimmunity.

    PubMed

    Bellinger, D L; Lorton, D; Felten, S Y; Felten, D L

    1992-04-01

    We now have substantial evidence demonstrating noradrenergic sympathetic and peptidergic innervation of both primary and secondary lymphoid organs. We have established criteria for norepinephrine, and some of the neuropeptides, as neurotransmitters, and have found changes in immune responsiveness following pharmacological manipulation of noradrenergic sympathetic or peptidergic nerves. Classic receptor binding studies have demonstrated a wide variety of target cells that possess beta-adrenoceptors and receptors for neuropeptides on cells of the immune system, including lymphocyte subsets, macrophages, accessory cells, or stromal elements. In this chapter we describe noradrenergic and peptidergic innervation of primary and secondary lymphoid organs in development, at maturation and during the normal aging process, and discuss possible functional implications of direct neural signals onto cells of the immune system at critical time points in the lifespan of an animal. Further, we examine for involvement of noradrenergic sympathetic and peptidergic innervation in the development and progression of several autoimmune disorders, including adjuvant-induced arthritis, New Zealand mice strains as a model for hemolytic anemia and lupus-like syndrome, and the experimental allergic encephalomyelitis model for multiple sclerosis. PMID:1319962

  10. Water mass age and aging driving chromophoric dissolved organic matter in the dark global ocean

    NASA Astrophysics Data System (ADS)

    Catalá, T. S.; Reche, I.; Álvarez, M.; Khatiwala, S.; Guallart, E. F.; Benítez-Barrios, V. M.; Fuentes-Lema, A.; Romera-Castillo, C.; Nieto-Cid, M.; Pelejero, C.; Fraile-Nuez, E.; Ortega-Retuerta, E.; Marrasé, C.; Álvarez-Salgado, X. A.

    2015-07-01

    The omnipresence of chromophoric dissolved organic matter (CDOM) in the open ocean enables its use as a tracer for biochemical processes throughout the global overturning circulation. We made an inventory of CDOM optical properties, ideal water age (τ), and apparent oxygen utilization (AOU) along the Atlantic, Indian, and Pacific Ocean waters sampled during the Malaspina 2010 expedition. A water mass analysis was applied to obtain intrinsic, hereinafter archetypal, values of τ, AOU, oxygen utilization rate (OUR), and CDOM absorption coefficients, spectral slopes and quantum yield for each one of the 22 water types intercepted during this circumnavigation. Archetypal values of AOU and OUR have been used to trace the differential influence of water mass aging and aging rates, respectively, on CDOM variables. Whereas the absorption coefficient at 325 nm (a325) and the fluorescence quantum yield at 340 nm (Φ340) increased, the spectral slope over the wavelength range 275-295 nm (S275-295) and the ratio of spectral slopes over the ranges 275-295 nm and 350-400 nm (SR) decreased significantly with water mass aging (AOU). Combination of the slope of the linear regression between archetypal AOU and a325 with the estimated global OUR allowed us to obtain a CDOM turnover time of 634 ± 120 years, which exceeds the flushing time of the dark ocean (>200 m) by 46%. This positive relationship supports the assumption of in situ production and accumulation of CDOM as a by-product of microbial metabolism as water masses turn older. Furthermore, our data evidence that global-scale CDOM quantity (a325) is more dependent on aging (AOU), whereas CDOM quality (S275-295, SR, Φ340) is more dependent on aging rate (OUR).

  11. Impact of Stronger Production and Loss Rates of Secondary Organic Aerosols on their Global Distribution and Budget

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Kasibhatla, P. S.; Cappa, C. D.; Madronich, S.; Jo, D. S.; Park, R.; Jimenez, J. L.

    2015-12-01

    Organic aerosols are observed to be the major constituents of submicron particles worldwide, and yet their atmospheric lifecycle including formation, ageing, and removal processes is poorly understood. Recent laboratory and ambient measurements suggest that both production yields and removal rates of chemically produced secondary organic aerosols (SOA) are much stronger and more diverse than currently assumed in chemistry-climate models (which typically consider wet deposition as the major loss process). In this study, we re-assess the global SOA distribution and budget with newly proposed SOA production and loss processes derived from these recent measurements, as well as from theoretical calculations. We evaluate and discuss the relative importance of removal pathways for organic vapors and particles (e.g. dry and wet deposition, photo-dissociation, evaporation, and heterogeneous surface reactions), and their effect on the SOA vertical distribution and budget using the GEOS-Chem global chemistry-transport model. We compare simulated SOA from various model configurations against ground, aircraft and satellite measurements to assess the extent to which these new developments in our understanding of SOA formation and removal processes are consistent with observed characteristics of the SOA distribution. Our results show strong changes in predicted vertical profiles of organic aerosols with higher SOA concentrations in the boundary layer and lower concentrations in the upper troposphere, which appear to be in a better agreement with aircraft measurements.

  12. Direct photolysis of α-pinene ozonolysis secondary organic aerosol: effect on particle mass and peroxide content.

    PubMed

    Epstein, Scott A; Blair, Sandra L; Nizkorodov, Sergey A

    2014-10-01

    Primary and secondary organic aerosols (POA and SOA) contain a complex mixture of multifunctional chemicals, many of which are photolabile. Much of the previous work that aimed to understand the chemical evolution (aging) of POA and SOA has focused on the reactive uptake of gas-phase oxidants by particles. By stripping volatile compounds and ozone from α-pinene ozonolysis SOA with three 1-m-long denuders, and exposing the residual particles in a flow cell to near-ultraviolet (λ>300 nm) radiation, we find that condensed-phase photochemistry can induce significant changes in SOA particle size and chemical composition. The particle-bound organic peroxides, which are highly abundant in α-pinene ozonolysis SOA (22 ± 5% by weight), have an atmospheric photolysis lifetime of about 6 days at a 24-h average solar zenith angle (SZA) of 65° experienced at 34° latitude (Los Angeles) in the summer. In addition, the particle diameter shrinks 0.56% per day under these irradiation conditions as a result of the loss of volatile photolysis products. Experiments with and without the denuders show similar results, suggesting that condensed-phase processes dominate over heterogeneous reactions of particles with organic vapors, excess ozone, and gas-phase free radicals. These condensed-phase photochemical processes occur on atmospherically relevant time scales and should be considered when modeling the evolution of organic aerosol in the atmosphere. PMID:25165890

  13. Secondary organic aerosol formation and primary organic aerosol oxidation from biomass-burning smoke in a flow reactor during FLAME-3

    NASA Astrophysics Data System (ADS)

    Ortega, A. M.; Day, D. A.; Cubison, M. J.; Brune, W. H.; Bon, D.; de Gouw, J. A.; Jimenez, J. L.

    2013-11-01

    We report the physical and chemical effects of photochemically aging dilute biomass-burning smoke. A "potential aerosol mass" (PAM) flow reactor was used with analysis by a high-resolution aerosol mass spectrometer and a proton-transfer-reaction ion-trap mass spectrometer during the FLAME-3 campaign. Hydroxyl (OH) radical concentrations in the reactor reached up to ~1000 times average tropospheric levels, producing effective OH exposures equivalent to up to 5 days of aging in the atmosphere, and allowing for us to extend the investigation of smoke aging beyond the oxidation levels achieved in traditional smog chambers. Volatile organic compound (VOC) observations show aromatics and terpenes decrease with aging, while formic acid and other unidentified oxidation products increase. Unidentified gas-phase oxidation products, previously observed in atmospheric and laboratory measurements, were observed here, including evidence of multiple generations of photochemistry. Substantial new organic aerosol (OA) mass ("net SOA"; secondary OA) was observed from aging biomass-burning smoke, resulting in total OA average of 1.42 ± 0.36 times the initial primary OA (POA) after oxidation. This study confirms that the net-SOA-to-POA ratio of biomass-burning smoke is far lower on average than that observed for urban emissions. Although most fuels were very reproducible, significant differences were observed among the biomasses, with some fuels resulting in a doubling of the OA mass, while for others a very small increase or even a decrease was observed. Net SOA formation in the photochemical reactor increased with OH exposure (OHexp), typically peaking around three days of equivalent atmospheric photochemical age (OHexp~3.9 × 1011 molecules cm-3 s), then leveling off at higher exposures. The amount of additional OA mass added from aging is positively correlated with initial POA concentration, but not with the total VOC concentration or the concentration of known SOA precursors

  14. Carbon in southeastern U.S. aerosol particles: Empirical estimates of secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Blanchard, Charles L.; Hidy, George M.; Tanenbaum, Shelley; Edgerton, Eric; Hartsell, Benjamin; Jansen, John

    Fine particles in the southeastern United States are rich in carbon: Southeastern Aerosol Research and Characterization (SEARCH) network measurements from 2001 through 2004 indicate that fine particles less than 2.5 μm aerodynamic diameter (PM 2.5) at two inland urban sites, Atlanta, GA and Birmingham, AL, contain 9 and 11% black carbon (BC) by mass, respectively, on average. For neighboring rural or urban Gulf Coast sites, the range is 4-7% BC. Organic carbon (OC) ranges from 25 to 27% in the inland cities, and 19-24% at the rural or Gulf Coast locations. Evidence in the literature suggests that a substantial fraction of the OC found in the Southeast is produced by atmospheric chemical reactions of volatile organic compounds (VOCs). Estimation of the fraction of OC from primary and secondary sources is difficult from first principles, because the chemistry is complex and incompletely understood, and the emission sources are both anthropogenic and natural. As an alternative, measurement-based models can be used to estimate empirically the primary and secondary source contributions. Three complementary empirical models are described and applied using the SEARCH database. The methods include (a) a multiple regression model employing markers for primary and secondary carbon using gas and particle data, (b) a carbon mass balance using carbon and CO data, along with certain assumptions about the OC/CO ratios in primary emissions for different urban and rural conditions, and (c) exploitation of isotopic measurements of carbon along with the BC and OC data. Secondary organic carbon (SOC) represents ˜20-60% of mean OC, depending upon location and season. The results are sensitive to estimates of emissions of primary OC and BC.

  15. 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

  16. Colonial Secondary Education in a Global Age: Economic Distortions in Bangladesh.

    ERIC Educational Resources Information Center

    Ilon, Lynn

    2000-01-01

    Argues that existing secondary education system in Bangladesh, designed during British colonial times, is ill suited to serve current labor-market demands. Discusses three economic distortions resulting from the misalignment of secondary education with the labor market: inappropriate curriculum, excess demand for secondary education, and increased…

  17. Sources of primary and secondary organic aerosol and their diurnal variations.

    PubMed

    Zheng, Mei; Zhao, Xiuying; Cheng, Yuan; Yan, Caiqing; Shi, Wenyan; Zhang, Xiaolu; Weber, Rodney J; Schauer, James J; Wang, Xinming; Edgerton, Eric S

    2014-01-15

    PM(2.5), as one of the criteria pollutants regulated in the U.S. and other countries due to its adverse health impacts, contains more than hundreds of organic pollutants with different sources and formation mechanisms. Daytime and nighttime PM2.5 samples from the August Mini-Intensive Gas and Aerosol Campaign (AMIGAS) in the southeastern U.S. were collected during summer 2008 at one urban site and one rural site, and were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and various individual organic compounds including some important tracers for carbonaceous aerosol sources by gas chromatography-mass spectrometry. Most samples exhibited higher daytime OC concentration, while higher nighttime OC was found in a few events at the urban site. Sources, formation mechanisms and composition of organic aerosol are complicated and results of this study showed that it exhibited distinct diurnal variations. With detailed organic tracer information, sources contributing to particulate OC were identified: higher nighttime OC concentration occurring in several occasions was mainly contributed by the increasing primary emissions at night, especially diesel exhaust and biomass burning; whereas sources responsible for higher daytime OC concentration included secondary organic aerosol (SOA) formation (e.g., cis-pinonic acid and non-biomass burning WSOC) together with traffic emissions especially gasoline engine exhaust. Primary tracers from combustion related sources such as EC, polycyclic aromatic hydrocarbons, and hopanes and steranes were significantly higher at the urban site with an urban to rural ratio between 5 and 8. However, this urban-rural difference for secondary components was less significant, indicating a relatively homogeneous distribution of SOA spatially. We found cholesterol concentrations, a typical tracer for meat cooking, were consistently higher at the rural site especially during the daytime, suggesting the likely

  18. Quantitative evaluation of emission controls on primary and secondary organic aerosol sources during Beijing 2008 Olympics

    NASA Astrophysics Data System (ADS)

    Guo, S.; Hu, M.; Guo, Q.; Zhang, X.; Schauer, J. J.; Zhang, R.

    2013-08-01

    To assess the primary and secondary sources of fine organic aerosols after the aggressive implementation of air pollution controls during the 2008 Beijing Olympic Games, 12 h PM2.5 values were measured at an urban site at Peking University (PKU) and an upwind rural site at Yufa during the CAREBEIJING-2008 (Campaigns of Air quality REsearch in BEIJING and surrounding region) summer field campaign. The average PM2.5 concentrations were 72.5 ± 43.6 μg m-3 and 64.3 ± 36.2 μg m-3 (average ± standard deviation, below as the same) at PKU and Yufa, respectively, showing the lowest concentrations in recent years. Combining the results from a CMB (chemical mass balance) model and secondary organic aerosol (SOA) tracer-yield model, five primary and four secondary fine organic aerosol sources were compared with the results from previous studies in Beijing. The relative contribution of mobile sources to PM2.5 concentrations was increased in 2008, with diesel engines contributing 16.2 ± 5.9% and 14.5 ± 4.1% and gasoline vehicles contributing 10.3 ± 8.7% and 7.9 ± 6.2% to organic carbon (OC) at PKU and Yufa, respectively. Due to the implementation of emission controls, the absolute OC concentrations from primary sources were reduced during the Olympics, and the contributions from secondary formation of OC represented a larger relative source of fine organic aerosols. Compared with the non-controlled period prior to the Olympics, primary vehicle contributions were reduced by 30% at the urban site and 24% at the rural site. The reductions in coal combustion contributions were 57% at PKU and 7% at Yufa. Our results demonstrate that the emission control measures implemented in 2008 significantly alleviated the primary organic particle pollution in and around Beijing. However, additional studies are needed to provide a more comprehensive assessment of the emission control effectiveness on SOA formation.

  19. Effects of aging on organic aerosol from open biomass burning smoke in aircraft and lab studies

    NASA Astrophysics Data System (ADS)

    Cubison, M. J.; Ortega, A. M.; Hayes, P. L.; Farmer, D. K.; Day, D.; Lechner, M. J.; Brune, W. H.; Apel, E.; Diskin, G. S.; Fisher, J. A.; Fuelberg, H. E.; Hecobian, A.; Knapp, D. J.; Mikoviny, T.; Riemer, D.; Sachse, G. W.; Sessions, W.; Weber, R. J.; Weinheimer, A. J.; Wisthaler, A.; Jimenez, J. L.

    2011-04-01

    Biomass burning (BB) is a large source of primary and secondary organic aerosols (POA and SOA). This study addresses the physical and chemical evolution of BB organic aerosols. Firstly, the evolution and lifetime of BB POA and SOA signatures observed with the Aerodyne Aerosol Mass Spectrometer are investigated, focusing on measurements at high-latitudes acquired during the 2008 NASA ARCTAS mission, in comparison to data from other field studies and from laboratory aging experiments. The parameter f60, the ratio of the integrated signal at m/z 60 to the total signal in the organic component mass spectrum, is used as a marker to study the rate of oxidation and fate of the BB POA. A background level of f60~0.3% ±0.06% for SOA-dominated ambient OA is shown to be an appropriate background level for this tracer. Using also f44 as a tracer for SOA and aged POA, a novel graphical method is presented to characterise the aging of BB plumes. Similar trends of decreasing f60 and increasing f44 with aging are observed in most field and lab studies. At least some very aged BB plumes retain a clear f60 signature. A statistically significant difference in f60 between highly-oxygenated OA of BB and non-BB origin is observed using this tracer, consistent with a substantial contribution of BBOA to the springtime Arctic aerosol burden in 2008. Secondly, a summary is presented of results on the net enhancement of OA with aging of BB plumes, which shows large variability. The estimates of net OA gain range from ΔOA/ΔCO(mass) =-0.01 to ~0.07, with a mean ΔOA/POA ~25%. With these ratios and global inventories of BB CO and POA a global net OA source due to aging of BB plumes of ~9 Tg OA yr-1 is estimated, of the order of 5% of recent total OA source estimates. Further field data following BB plume advection should be a focus of future research in order to better constrain this potentially important contribution to the OA burden.

  20. Biogenic Potassium Salt Particles as Seeds for Secondary Organic Aerosol in the Amazon

    NASA Astrophysics Data System (ADS)

    Pöhlker, Christopher; Wiedemann, Kenia T.; Sinha, Bärbel; Shiraiwa, Manabu; Gunthe, Sachin S.; Smith, Mackenzie; Su, Hang; Artaxo, Paulo; Chen, Qi; Cheng, Yafang; Elbert, Wolfgang; Gilles, Mary K.; Kilcoyne, Arthur L. D.; Moffet, Ryan C.; Weigand, Markus; Martin, Scot T.; Pöschl, Ulrich; Andreae, Meinrat O.

    2012-08-01

    The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest.

  1. Physical Properties of Ambient and Laboratory-Generated Secondary Organic Aerosol

    SciTech Connect

    O'Brien, Rachel E.; Neu, Alexander; Epstein, Scott A.; MacMillan, Amanda; Wang, Bingbing; Kelly, Stephen T.; Nizkorodov, Sergey; Laskin, Alexander; Moffet, Ryan C.; Gilles, Mary K.

    2014-06-17

    The size and thickness of organic aerosol particles collected by impaction in five field campaigns were compared to those of laboratory generated secondary organic aerosols (SOA). Scanning transmission x-ray microscopy (STXM) was used to measure the total carbon absorbance (TCA) by individual particles as a function of their projection areas on the substrate. Because they flatten less upon impaction, particles with higher viscosity and surface tension can be identified by a steeper slope on a plot of TCA vs. size. The slopes of the ambient data are statistically similar indicating a small range of average viscosities and surface tensions across five field campaigns. Steeper slopes were observed for the plots corresponding to ambient particles, while smaller slopes were indicative of the laboratory generated SOA. This comparison indicates that ambient organic particles have higher viscosities and surface tensions than those typically generated in laboratory SOA studies.

  2. 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

  3. Volatility of Secondary Organic Aerosol (SOA) Formed from Photooxidation of Isoprene

    NASA Astrophysics Data System (ADS)

    Ng, N. L.; Kollman, M.; Xu, L.; Shilling, J. E.

    2012-12-01

    Isoprene is the most abundant non-methane hydrocarbon, so even a small aerosol yield may have a large effect on both local and global secondary organic aerosol (SOA) production. Previous studies have shown that isoprene SOA yields are higher under low-NOx conditions, and that volatility of isoprene SOA under low-NOx conditions is similar to a-pinene SOA. In this study, the volatility of SOA formed from the photooxidation of isoprene under different NOx conditions is investigated with a thermodenuder. Laboratory chamber experiments are performed under different NOx conditions at low RH (RH<5%) and without seed. H2O2 and HONO is used as OH precursor for low-NOx and high-NOx experiments, respectively. During each experiment, isoprene and selected gas-phase oxidation products are monitored with a Proton Transfer Reaction Mass Spectrometry (PTRMS).Particle-phase composition, mass, size distribution are measured with a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Scanning Mobility Particle Sizer (SMPS). The thermodenuder is upstream of the the HR-ToF-AMS and SMPS, modulating the aerosol composition with temperatures ranging from 30 to 200 oC. In general, the volatility of SOA decreases after peak SOA growth, indicating the formation of highly oxidized, low-volatility species with increased photochemical aging. The SOA yields obtained are in agreement with previous studies, with more SOA formed under low-NOx conditions. However, it is found that SOA formed under low-NOx conditions are more volatile. Preliminary results show that about 60% of low-NOx isoprene SOA and <40% of high-NOx isoprene SOA evaporates at 100 oC. Under high-NOx conditions, there is still 10% of aerosol mass remaining at 200 oC, suggesting that there are some very non-volatiles species in high-NOx isoprene SOA. The mass fraction of isoprene SOA remaining as a function of NOx and temperature will be presented. The mass spectra features of SOA at these conditions will also

  4. Wintertime Secondary Organic Aerosol (SOA) Formation from Oxidation of Volatile Organic Compounds (VOCs) Associated with Oil and Gas Extraction

    NASA Astrophysics Data System (ADS)

    Murphy, S. M.; Soltis, J.; Field, R. A.; Bates, T. S.; Quinn, P.; De Gouw, J. A.; Veres, P. R.; Warneke, C.; Graus, M.; Gilman, J.; Lerner, B. M.; Koss, A.

    2013-12-01

    The Uintah Basin is located in a lightly populated area of Northeastern Utah near Dinosaur National Monument. Oil and gas extraction activities in the basin have dramatically increased in recent years due to the application of hydraulic fracturing. The Uintah Basin has experienced numerous high-ozone events during the past several winters with concentrations often exceeding 100 ppb. PM 2.5 monitoring by the city of Vernal, located at the edge of the basin, have shown wintertime concentrations in excess of the EPA 8-hour national standard, though the source and composition of particulates during these events is unclear. The Energy and Environment - Uintah Basin Winter Ozone Study (E&E UBWOS) was conducted during the winters of 2012 and 2013. During the study, intensive measurements of aerosol composition and speciated VOCs were made at a monitoring site near oil and gas extraction activities. Organic aerosol was found to be a major component of PM 2.5 and organic aerosol formation was highly correlated with the production of secondary VOC's. This correlation suggests that the organic aerosol is secondary in nature even though O:C ratios suggest a less oxidized aerosol than often observed in summertime SOA. The ozone levels and organic aerosol mass during 2012 were much lower than those observed in 2013. Calculations of the aerosol yield during both years will be presented along with an analysis of how well observed yields match predictions based on smog-chamber data. The potential for additional aerosol formation in the system will also be discussed.

  5. Social Interactions of Secondary-Aged Students with Severe Handicaps: Implications for Facilitating the Transition from School to Work.

    ERIC Educational Resources Information Center

    Chadsey-Rusch, Janis

    This study describes the social interactions used by a group of 10 secondary-aged students with severe to profound mental retardation, using data gathered through the use of narrative recording procedures. The students' interactions were recorded during school arrival, lunch, and vocational training. Results are presented along three dimensions:…

  6. Non-Resident Fathers' Relationships with Their Secondary School Age Children: Determinants and Children's Mental Health Outcomes

    ERIC Educational Resources Information Center

    Flouri, Eirini

    2006-01-01

    Data from 520 British secondary school age children were used to explore determinants of and mental health outcomes (measured with the Strengths and Difficulties Questionnaire) from their non-resident fathers' relationships (child-reported father's involvement and frequency of contact) with them. Frequency of contact was negatively related to time…

  7. Effects of a Metacognitive Strategy on Aggressive Acts and Anger Behavior of Elementary and Secondary-Aged Students.

    ERIC Educational Resources Information Center

    Smith, Steven W.

    1992-01-01

    This report investigates the effectiveness of a metacognitive strategy in reducing anger behavior and/or aggressive acts in elementary and secondary-aged students placed in special education classes. Three separate studies were conducted with three elementary, three middle, and three high school students who were placed in special education…

  8. 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

  9. Estimating the influence of the secondary organic aerosols on present climate using ECHAM5-HAM

    NASA Astrophysics Data System (ADS)

    O'Donnell, D.; Tsigaridis, K.; Feichter, J.

    2011-01-01

    In recent years, several field measurement campaigns have highlighted the importance of the organic fraction of aerosol mass, and with such spatial diversity that one may assert that these aerosols are ubiquitous in the troposphere, with particular importance in continental areas. Investigation of the chemical composition of organic aerosol remains a work in progress, but it is now clear that a significant portion of the total organic mass is composed of secondary organic material, that is, aerosol chemically formed from gaseous volatile organic carbon (VOC) precursors. A number of such precursors, of both biogenic and anthropogenic origin, have been identified. Experimental, inventory building and modelling studies have followed. Laboratory studies have yielded information on the chemical pathways that lead to secondary organic aerosol (SOA) formation, and provided the means to estimate the aerosol yields from a given precursor-oxidant reaction. Global inventories of anthropogenic VOC emissions, and of biogenic VOC emitter species distribution and their emission potential have been constructed. Models have been developed that provide global estimates of precursor VOC emissions, SOA formation and atmospheric burdens of these species. This paper estimates the direct and indirect effects of these aerosols using the global climate-aerosol model ECHAM5-HAM. For year 2000 conditions, we estimate a global annual mean shortwave (SW) aerosol direct effect due to SOA of -0.3 W m-2. The model predicts a positive SW indirect effect due to SOA amounting to +0.23 W m-2, arising from enlargement of particles due to condensation of SOA, together with an enhanced coagulation sink for small particles. Longwave effects are small. Finally, we indicate of areas of research into SOA that are required in order to better constrain our estimates of the influence of aerosols on the climate system.

  10. Nitrogenated and aliphatic organic vapors as possible drivers for marine secondary organic aerosol growth

    NASA Astrophysics Data System (ADS)

    Dall'Osto, Manuel; Ceburnis, Darius; Monahan, Ciaran; Worsnop, Douglas R.; Bialek, Jakub; Kulmala, Markku; KurtéN, Theo; Ehn, Mikael; Wenger, John; Sodeau, John; Healy, Robert; O'Dowd, Colin

    2012-06-01

    Measurements of marine aerosol chemistry, using state-of-the-art mass spectrometry, as well as aerosol microphysics, hygroscopicity and cloud condensation nuclei (CCN) activity were undertaken during new particle growth events. The events were detected in air advecting over North East (NE) Atlantic waters during the EUCAARI Intensive Observation Period in June 2008 at Mace Head, Ireland. During these growth events, the aerosol mass spectrometers illustrated increases in accumulation mode aerosol phase nitrogenated and aliphatic compounds thought to condense from the gas phase. Since the composition changes observed in the accumulation mode occurred simultaneously to the growth of the accumulation, Aitken and nucleation modes, the growth of both the nucleation mode and the Aitken mode is attributed to the condensation of these species. Nitrogenated compounds like amines are also plausible candidates in the nucleation process, as suggested by quantum mechanic calculations. It is also plausible that amides and organic nitrites, also identified by the mass spectrometers, are possible candidate chemical compounds, suggesting that multiple types of chemical species may be contributing. Given that these open ocean aerosol formation and growth events occur in very clean polar marine air masses, we suggest that the organic compounds responsible for particle formation and growth are mainly of biogenic origin. Despite increasing the particle number concentration, the initial effect is to suppress hygroscopicity and CCN activity.

  11. Formation of secondary organic aerosol in the Paris pollution plume and its impact on surrounding regions

    NASA Astrophysics Data System (ADS)

    Zhang, Q. J.; Beekmann, M.; Freney, E.; Sellegri, K.; Pichon, J. M.; Schwarzenboeck, A.; Colomb, A.; Bourrianne, T.; Michoud, V.; Borbon, A.

    2015-03-01

    Secondary pollutants such as ozone, secondary inorganic aerosol, and secondary organic aerosol formed in the plume of megacities can affect regional air quality. In the framework of the FP7/EU MEGAPOLI project, an intensive campaign was launched in the Greater Paris Region in July 2009. The major objective was to quantify different sources of organic aerosol (OA) within a megacity and in its plume. In this study, we use airborne measurements aboard the French ATR-42 aircraft to evaluate the regional chemistry-transport model CHIMERE within and downwind the Paris region. Slopes of the plume OA levels vs. Ox (= O3 + NO2) show secondary OA (SOA) formation normalized with respect to photochemical activity and are used for specific evaluation of the OA scheme in the model. Simulated and observed slopes are in good agreement, when the most realistic "high-NOx" yields are used in the Volatility-Basis-Set scheme implemented into the model. In addition, these slopes are relatively stable from one day to another, which suggest that they are characteristic for the given megacity plume environment. Since OA within the plume is mainly formed from anthropogenic precursors (VOC and primary OA, POA), this work allows a specific evaluation of anthropogenic SOA and SOA formed from primary semi-volatile and intermediate volatile VOCs (SI-SOA) formation scheme in a model. For specific plumes, this anthropogenic OA build-up can reach about 10 μg m-3. For the average of the month of July 2009, maximum increases occur close to the agglomeration for primary OA are noticed at several tens (for POA) to hundred (for SI-SOA) kilometers of distance from the Paris agglomeration.

  12. Semi-volatile secondary organic aerosol in urban atmospheres: meeting a measurement challenge

    NASA Astrophysics Data System (ADS)

    Eatough, Delbert J.; Long, Russell W.; Modey, William K.; Eatough, Norman L.

    Ammonium nitrate and semi-volatile organic compounds are significant components of fine particles in urban atmospheres. These components, however, are not properly determined with current US EPA accepted methods such as the PM 2.5 FRM or other single filter samplers due to significant losses of semi-volatile material (SVM) from particles collected on the filter during sampling. Continuous PM 2.5 mass measurements are attempted using methods such as the R&P TEOM monitor. This method, however, heats the sample to remove particle-bound water which also results in evaporation of SVM. Research at Brigham Young University has resulted in samplers for both the integrated and continuous measurement of total PM 2.5, including the SVM. The PC-BOSS is a charcoal diffusion denuder based sampler for the determination of fine particulate chemical composition including the semi-volatile organic material. The RAMS is a modified TEOM monitor which includes diffusion denuders and Nafion dryers to remove gas phase material which can be absorbed by a charcoal sorbent filter. The RAMS then uses a "sandwich filter" consisting of a conventional particle collecting Teflon coated TX40 filter, followed by an activated charcoal sorbent filter which retains any semi-volatile ammonium nitrate or organic material lost from the particles collected on the TEOM monitor Teflon coated filter, thus allowing for determination of total PM 2.5 mass including the SVM. Recent research conducted by Brigham Young University using these two samplers has indicated the following about semi-volatile organic aerosol: The majority of semi-volatile fine particulate organic material is secondary organic aerosol. This semi-volatile organic aerosol is not retained on the heated filter of a regular TEOM monitor and hence is not measured by this sampling technique. In addition, secondary ammonium nitrate is also lost. Much of the semi-volatile organic aerosol is also lost during sampling from single filter samplers

  13. Using multidimensional gas chromatography to group secondary organic aerosol species by functionality

    NASA Astrophysics Data System (ADS)

    Flores, Rosa M.; Doskey, Paul V.

    2014-10-01

    A carbon number-functionality grid (CNFG) for a complex mixture of secondary organic aerosol (SOA) precursors and oxidation products was developed from the theoretical retention index diagram of a multidimensional gas chromatographic (GC × 2GC) analysis of a mixture of SOA precursors and derivatized oxidation products. In the GC × 2GC analysis, comprehensive separation of the complex mixture was achieved by diverting the modulated effluent from a polar primary column into 2 polar secondary columns. Column stationary phases spanned the widest range of selectivity of commercially available GC analytic columns. In general, separation of the species by the polar primary column was by the number of carbon atoms in the molecule (when the homologous series of reference compounds was selected to have molecular volumes and functionalities similar to the target analytes) and the polar secondary columns provided additional separation according to functionality. An algebraic transformation of the Abraham solvation parameter model was used to estimate linear retention indices of solutes relative to elution of a homologous series of methyl diesters on the primary and secondary columns to develop the theoretical GC × 2GC retention diagram. Retention indices of many of the oxidation products of SOA precursors were estimated for derivatized forms of the solutes. The GC stationary phases selected for the primary column [(50%-Trifluoropropyl)-methylpolysiloxane] and secondary columns (90% Cyanopropyl Polysilphenylene-siloxane and Polyethylene Glycol in a Sol-Gel matrix) provided a theoretical separation of 33 SOA precursors and 98 derivatized oxidation products into 35 groups by molecular volume and functionality. Comprehensive analysis of extracts of vapor and aerosol samples containing semivolatile SOA precursors and oxidation products, respectively, is best accomplished by (1) separating the complex mixture of the vapor and underivatized aerosol extracts with a (50

  14. Primary and secondary gaseous organic carbon in suburban Paris during the MEGAPOLI experiments

    NASA Astrophysics Data System (ADS)

    Ait-Helal, W.; Borbon, A.; Sauvage, S.; Michoud, V.; Colomb, A.; Afif, C.; Miet, K.; Perrier, S.; Bechara, J.; Gros, V.; Crippa, M.; Prevot, A. S.; Locoge, N.

    2011-12-01

    Since 1950, the amount of people living in urban areas has not stopped increasing. Indeed, the urban population has risen from 30% to 50% of the world population within 50 years. An increasing number of megacities has also been observed. These urban areas are of a great important since they concentrate not only human being, but also high intensity activities which could end up emitting large amount of pollutants and, thus, threatening people health. In this context, the FP7 MEGAPOLI project aims to quantify sources of primary and secondary aerosols and the role of organic gas-phase precursors, in and around a large agglomeration and to describe their evolution in the megacity plume. Two intensive field campaigns were conducted in the Greater Paris region during the summer 2009 and the winter 2010. Primary and secondary VOCs of both anthropogenic and biogenic origins (monofunctionnal and bifunctionnal alkanes, alkenes, aromatics, terpenes, aldehydes and ketones), were measured at a suburban site in Paris (SIRTA). This wide range of carbonaceous compounds, from C2 to C16, includes species well-known to be secondary organic aerosol (SOAs) precursors, which have as many impacts on the climate as the gaseous compounds. Based on a source-receptor approach, the chemical signature of VOCs highlights that the SIRTA site is impacted by three kinds of influences: Paris urban outflow with higher levels of anthropogenic compounds, oceanic and/or continental air masses transported over long distances with high concentrations in secondary VOCs, southern/south-eastern plumes with significant amounts of biogenic compounds. First we will identify the primary and secondary origins of VOCs emissions and evaluate their contribution. Then, we will investigate the SOA formation regarding its potential VOC precursors. Good correlations have been observed several times during the summer campaign between anthropogenic (aromatics and heavy alkanes >C12) and/or biogenic (isoprene and

  15. Incremental Reactivity Effects of Anthropogenic and Biogenic Volatile Organic Compounds on Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Kacarab, M.; Li, L.; Carter, W. P. L.; Cocker, D. R., III

    2015-12-01

    Two surrogate reactive organic gas (ROG) mixtures were developed to create a controlled reactivity environment simulating different urban atmospheres with varying levels of anthropogenic (e.g. Los Angeles reactivity) and biogenic (e.g. Atlanta reactivity) influences. Traditional chamber experiments focus on the oxidation of one or two volatile organic compound (VOC) precursors, allowing the reactivity of the system to be dictated by those compounds. Surrogate ROG mixtures control the overall reactivity of the system, allowing for the incremental aerosol formation from an added VOC to be observed. The surrogate ROG mixtures were developed based on that used to determine maximum incremental reactivity (MIR) scales for O3 formation from VOC precursors in a Los Angeles smog environment. Environmental chamber experiments were designed to highlight the incremental aerosol formation in the simulated environment due to the addition of an added anthropogenic (aromatic) or biogenic (terpene) VOC. All experiments were conducted in the UC Riverside/CE-CERT dual 90m3 environmental chambers. It was found that the aerosol precursors behaved differently under the two altered reactivity conditions, with more incremental aerosol being formed in the anthropogenic ROG system than in the biogenic ROG system. Further, the biogenic reactivity condition inhibited the oxidation of added anthropogenic aerosol precursors, such as m-xylene. Data will be presented on aerosol properties (density, volatility, hygroscopicity) and bulk chemical composition in the gas and particle phases (from a SYFT Technologies selected ion flow tube mass spectrometer, SIFT-MS, and Aerodyne high resolution time of flight aerosol mass spectrometer, HR-ToF-AMS, respectively) comparing the two controlled reactivity systems and single precursor VOC/NOx studies. Incremental aerosol yield data at different controlled reactivities provide a novel and valuable insight in the attempt to extrapolate environmental chamber

  16. Secondary organic aerosol formation in cloud and fog droplets: a literature evaluation of plausibility

    NASA Astrophysics Data System (ADS)

    Blando, James D.; Turpin, Barbara J.

    This paper investigates the hypothesis that cloud and fog processes produce fine organic particulate matter in the atmosphere. The evidence provided suggests that cloud and fog processes could be important contributors to secondary organic aerosol formation, and the contribution of this formation pathway should be further investigated. This conclusion is based on the following observations: (1) many organic vapors present in the atmosphere are sorbed by suspended droplets and have been measured in cloud and fog water, (2) organics participate in aqueous-phase reactions, and (3) organic particulate matter is sometimes found in the size mode attributed to cloud processing (i.e. the droplet mode). Specific compounds identified as potential precursors include aldehydes (e.g. formaldehyde, acetaldehyde, and propionaldehyde), acetone, alcohols (e.g. methanol, ethanol, 2-propanol, and phenol), monocarboxylic acids, and organic peroxides. Carboxylic acids (e.g. diacids and oxo-acids), glyoxal, esters, organosulfur compounds, polyols, amines and amino acids are potential products of cloud and fog processing.

  17. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-04-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; turning on organic-inorganic interactions only when the water content associated with organic compounds is significant; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 29.7 with ±15% deviation from benchmark results. These speedup methods are applicable to other SOA modules that are based on partitioning theories.

  18. 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.

  19. Atmospheric chemistry in stereo: A new look at secondary organic aerosols from isoprene

    NASA Astrophysics Data System (ADS)

    Nozière, Barbara; González, Nélida J. D.; Borg-Karlson, Anna-Karin; Pei, Yuxin; Redeby, Johan Pettersson; Krejci, Radovan; Dommen, Josef; Prevot, Andre S. H.; Anthonsen, Thorleif

    2011-06-01

    Isoprene, a compound emitted by vegetation, could be a major contributor to secondary organic aerosols (SOA) in the atmosphere. The main evidence for this contribution were the 2-methylbutane-1,2,3,4-tetraols, or 2-methyltetrols (2-methylerythritol and 2-methylthreitol) present in ambient aerosols. In this work, the four stereoisomers of these tetraols were analyzed in aerosols from Aspvreten, Sweden. 2-C-methyl-D-erythritol was found in excess over its enantiomer in the Spring/Summer, by up to 29% in July. This clearly indicated some biological origins for this enantiomer, consistent with its well-documented production by plants and other living organisms. In addition, a minimum of 20 to 60% of the mass of racemic tetraols appeared from biological origin. Thus, the SOA mass produced by isoprene in the atmosphere is less than what indicated by the 2-methyltetrols in aerosols. Our results also demonstrate that stereochemical speciation can distinguish primary and secondary organic material in atmospheric aerosols.

  20. Heterogeneous Chemistry of Carbonyls and Alcohols With Sulfuric Acid: Implications for Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Levitt, N.; Zhang, R.

    2006-12-01

    Recent environmental chamber studies have suggested that acid-catalyzed particle-phase reactions of organic carbonyls lead to multifold increases in secondary organic aerosol (SOA) mass and acid-catalyzed reactions between alcohols and aldehydes in the condensed phase lead to the formation of hemiacetals and acetals, also enhancing secondary organic aerosol growth. The kinetics and mechanism of the heterogeneous chemistry of carbonyls and alcohols with sulfuric acid, however, remain largely uncertain. In this talk, we present measurements of heterogeneous uptake of several carbonyls and alcohols on liquid H2SO4 in a wide range of acid concentrations and temperatures. The results indicate that uptake of larger carbonyls is explained by aldol condensation. For small dicarbonyls, heterogeneous reactions are shown to decrease with acidity and involve negligible formation of sulfate esters. Hydration and polymerization likely explain the measured uptake of such small dicarbonyls on H2SO4 and the measurements do not support an acid- catalyzed uptake. Atmospheric implications from our findings will be discussed.

  1. 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.

  2. DETERMINATION OF SECONDARY ORGANIC AEROSOL PRODUCTS FROM THE PHOTOOXIDATION OF TOLUENE AND THEIR IMPLICATIONS IN AMBIENT PM2.5

    EPA Science Inventory

    Laboratory study was carried out to investigate the secondary organic aerosol products from photooxidation of the aromatic hydrocarbon toluene. The laboratory experiments consisted of irradiating toluene/propylene/NOX/air mixtures in a smog chamber operated in the dynamic mode...

  3. MODELING THE EFFECT OF CHLORINE EMISSIONS ON ATMOSPHERIC OZONE AND SECONDARY ORGANIC AEROSOL CONCENTRATIONS ACROSS THE UNITED STATES

    EPA Science Inventory

    This paper presents the modeled effects of natural and anthropogenic chlorine emissions on the atmospheric concentrations of ozone and secondary organic aerosol across the United States. The model calculations include anthropogenic molecular chlorine emissions, anthropogenic hypo...

  4. Primary and secondary organics in tropical Amazonian rainforest aerosols: Chiral analysis of 2-methyltetrols

    SciTech Connect

    Gonzalez, Nelida; Borg-Karlson, Anna-Karin; Artaxo, Paulo; Guenther, Alex B.; Krejci, R.; Noziere, Barbara; Noone, Kevin

    2014-06-01

    This work presents the application of a newly developed method to facilitate the distinction between primary and secondary organic compounds in ambient aerosols based on their chiral analysis. The organic constituents chosen for chiral analysis are the four stereomers of the 2-methyltetrols, (2R,3S)- and (2S,3R)- methylerythritol and (2S,3S)- and (2R,3R)- methylthreitol. Ambient PM10 aerosol samples were collected between June 2008 and June 2009 near Manaus, Brazil, in a remote tropical rainforest environment of central Amazonia. The samples were analyzed for the presence of these four stereomers because qualitatively, in a previous study, they have been demonstrated to have partly primary origins. Thus the origin of these compounds may be primary and secondary from the biosynthesis and oxidation processes of isoprene within plants and also in the atmosphere. Using authentic standards, the quantified concentrations were in average 78.2 and 72.8 ng m-3 for (2R,3S)- and (2S,3R)- methylerythritol and 3.1 and 3.3 ng m-3 for (2S,3S)- and (2R,3R)- methylthreitol during the dry season and 7.1, 6.5, 2.0, and 2.2 ng m-3 during the wet season, respectively. Furthermore, these compounds were found to be outside the confidence interval for racemic mixtures (enantiomeric fraction, Ef = 0.5 -0.01) in nearly all the samples, with deviations of up to 32 % (Ef = 0.61) for (2R,3S)-methylerythritol and 47 % (Ef = 0.65) for (2S,3S)-methylthreitol indicating (99% confidence level) biologically-produced 2-methyltetrols. The minimum primary origin contribution ranged between 0.19 and 29.67 ng m-3 for the 2-methylerythritols and between 0.15 and 1.2 ng m-3 for the 2-methylthreitols. The strong correlation of the diatereomers (racemic 2-methylerythritol and 2-methylthreitol) in the wet season implied a secondary origin. Assuming the maximum secondary contribution in the dry season, the secondary fraction in the wet season was 81-99 % and in the dry season, 10 - 95 %. Nevertheless, from the

  5. Determination of primary and secondary sources of organic acids and carbonaceous aerosols using stable carbon isotopes

    NASA Astrophysics Data System (ADS)

    Fisseha, Rebeka; Saurer, Matthias; Jäggi, Maya; Siegwolf, Rolf T. W.; Dommen, Josef; Szidat, Sönke; Samburova, Vera; Baltensperger, Urs

    Stable carbon isotope ratio ( δ13C) data can provide important information regarding the sources and the processing of atmospheric organic carbon species. Formic, acetic and oxalic acid were collected from Zurich city in August-September 2002 and March 2003 in the gas and aerosol phase, and the corresponding δ13C analysis was performed using a wet oxidation method followed by isotope ratio mass spectrometry. In August, the δ13C values of gas phase formic acid showed a significant correlation with ozone (coefficient of determination ( r2) = 0.63) due to the kinetic isotope effect (KIE). This indicates the presence of secondary sources (i.e. production of organic acids in the atmosphere) in addition to direct emission. In March, both gaseous formic and acetic acid exhibited similar δ13C values and did not show any correlation with ozone, indicating a predominantly primary origin. Even though oxalic acid is mainly produced by secondary processes, the δ13C value of particulate oxalic acid was not depleted and did not show any correlation with ozone, which may be due to the enrichment of 13C during the gas - aerosol partitioning. The concentrations and δ13C values of the different aerosol fractions (water soluble organic carbon, water insoluble organic carbon, carbonate and black carbon) collected during the same period were also determined. Water soluble organic carbon (WSOC) contributed about 60% to the total carbon and was enriched in 13C compared to other fractions indicating a possible effect of gas - aerosol partitioning on δ13C of carbonaceous aerosols. The carbonate fraction in general was very low (3% of the total carbon).

  6. Characterization of Organic Nitrate Formation in Limonene Secondary Organic Aerosol using High-Resolution Chemical Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Faxon, Cameron; Hammes, Julia; Peng, Jianfei; Hallquist, Mattias; Pathak, Ravi

    2016-04-01

    Previous work has shown that organic nitrates (RONO2) are prevalent in the boundary layer, and can contribute significantly to secondary organic aerosol formation. Monoterpenes, including limonene, have been shown to be precursors for the formation of these organic nitrates. Limonene has two double bonds, either of which may be oxidized by NO3 or O3. This leads to the generation of products that can subsequently condense or partition into the particle phase, producing secondary organic aerosol. In order to further elucidate the particle and gas phase product distribution of organic nitrates forming from the reactions of limonene and the nitrate radical (NO3), a series of experiments were performed in the Gothenburg Flow Reactor for Oxidation Studies at Low Temperatures (G-FROST), described by previous work. N2O5 was used as the source for NO3 and NO2, and a characterized diffusion source was used to introduce limonene into the flow reactor. All experiments were conducted in the absence of light, and the concentration of limonene was increased step-wise throughout each experiment to modify the ratio of N2O5to limonene. The experiments were conducted such that both limonene- and N2O5-limited regimes were present. Gas and particle phase products were measured using an iodide High-Resolution Time-of-Flight Mass Spectrometer (HR-ToF-CIMS) coupled to a Filter Inlet for Gases and AEROsols (FIGAERO, and particle size and SOA mass concentrations were derived using a Scanning Mobility Particle Sizer (SMPS). CIMS measurement techniques have previously been employed for the measurement of organic nitrate products of such compounds using multiple reagent ions. The use of this instrumentation allowed for the identification of chemical formulas for gas and particle phase species. The findings from the experiments will be presented in terms of the relative gas-particle partitioning of major products and the effects of N2O5/limonene ratios on product distributions. Additionally, a

  7. Secondary organic aerosols formed from oxidation of biogenic volatile organic compounds in the Sierra Nevada Mountains of California

    NASA Astrophysics Data System (ADS)

    Cahill, Thomas M.; Seaman, Vincent Y.; Charles, M. Judith; Holzinger, Rupert; Goldstein, Allen H.

    2006-08-01

    Biogenic volatile organic compound (BVOC) emissions, such as isoprene and terpenes, can be oxidized to form less volatile carbonyls, acids, and multifunctional oxygenated products that may condense to form secondary organic aerosols (SOA). This research was designed to assess the contribution of oxidized BVOC emissions to SOA in coniferous forests by collecting high-volume particulate samples for 6 days and 5 nights in the summer of 2003. The samples were analyzed for acids, carbonyls, polyols and alkanes to quantify oxidized BVOCs. Terpene and isoprene oxidation products were among the most abundant chemical species detected with the exception of hexadecanoic acid, octadecanoic acid and two butyl esters of unknown origin. The terpene oxidation products of pinonic acid, pinic acid, nopinone and pinonaldehyde showed clear diurnal cycles with concentrations two- to eight-fold higher at night. These cycles resulted from the diurnal cycles in gaseous terpene concentrations and lower temperatures that enhanced condensation of semivolatile chemicals onto aerosols. The terpene-derived compounds averaged 157 ± 118 ng/m3 of particulate organic matter while the isoprene oxidation compounds, namely the 2-methyltetrols and 2-methylglyceric acid, accounted for 53 ± 19 ng/m3. Together, the terpene and isoprene oxidation products represented 36.9% of the identified organic mass of 490 ± 95 ng/m3. PM10 organic matter loadings in the region were approximately 2.1 ± 1.2 μg/m3, so about 23% of the organic matter was identified and at least 8.6% was oxidized BVOCs. The BVOC oxidation products we measured were significant, but not dominant, contributors to the regional SOA only 75 km downwind of the Sacramento urban area.

  8. Modeling organic aerosols in a megacity: potential contribution of semi-volatile and intermediate volatility primary organic compounds to secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Jimenez, J. L.; Madronich, S.; Canagaratna, M. R.; Decarlo, P. F.; Kleinman, L.; Fast, J.

    2010-06-01

    It has been established that observed local and regional levels of secondary organic aerosols (SOA) in polluted areas cannot be explained by the oxidation and partitioning of anthropogenic and biogenic VOC precursors, at least using current mechanisms and parameterizations. In this study, the 3-D regional air quality model CHIMERE is applied to estimate the potential contribution to SOA formation of recently identified semi-volatile and intermediate volatility organic precursors (S/IVOC) in and around Mexico City for the MILAGRO field experiment during March 2006. The model has been updated to include explicitly the volatility distribution of primary organic aerosols (POA), their gas-particle partitioning and the gas-phase oxidation of the vapors. Two recently proposed parameterizations, those of Robinson et al. (2007) ("ROB") and Grieshop et al. (2009) ("GRI") are compared and evaluated against surface and aircraft measurements. The 3-D model results are assessed by comparing with the concentrations of OA components from Positive Matrix Factorization of Aerosol Mass Spectrometer (AMS) data, and for the first time also with oxygen-to-carbon ratios derived from high-resolution AMS measurements. The results show a substantial enhancement in predicted SOA concentrations (2-4 times) with respect to the previously published base case without S/IVOCs (Hodzic et al., 2009), both within and downwind of the city leading to much reduced discrepancies with the total OA measurements. Model improvements in OA predictions are associated with the better-captured SOA magnitude and diurnal variability. The predicted production from anthropogenic and biomass burning S/IVOC represents 40-60% of the total measured SOA at the surface during the day and is somewhat larger than that from commonly measured aromatic VOCs, especially at the T1 site at the edge of the city. The SOA production from the continued multi-generation S/IVOC oxidation products continues actively downwind. Similar

  9. Secondary organic aerosol (trans)formation through aqueous phase guaiacol photonitration: a kinetic study

    NASA Astrophysics Data System (ADS)

    Kroflič, Ana; Grgić, Irena

    2014-05-01

    It is well known that atmospheric aerosols play a crucial role in the Earth's climate and public health (Pöschl 2005). Despite a great effort invested in the studies of secondary organic aerosol (SOA) budget, composition, and its formation mechanisms, there is still a gap between field observations and atmospheric model predictions (Heald et al. 2005, Hallquist et al. 2009, and Lim et al. 2010). The insisting uncertainties surrounding SOA formation and aging thus gained an increasing interest in atmospheric aqueous phase chemistry; they call for more complex and time consuming studies at the environmentally relevant conditions allowing confident extrapolation to desired ambient conditions. In addition to the adverse health effects of atmospheric particulate matter (PM) as such, toxicity is also attributed to nitro-aromatic and other organic compounds which have already been detected in real aerosol samples (Traversi et al. 2009). Moreover, low-volatility aromatic derivatives are believed to form at least partly in the aerosol aqueous phase and not only in the gas phase from where they partition into water droplets (Ervens et al. 2011). Two nitro derivatives of biomass burning tracer guaiacol have recently been found in winter PM10 samples from the city of Ljubljana, Slovenia, and aqueous photonitration reaction was proposed as their possible production pathway (Kitanovski et al. 2012). In this study the kinetics of guaiacol nitration in aqueous solution was investigated in the presence of H2O2 and NO2¯ upon simulated solar irradiation (Xenon lamp, 300 W). During the experiment the DURAN® flask with the reaction mixture was held in the thermostated bath and thoroughly mixed. The reaction was monitored for 44 hours at different temperatures. Guaiacol and its main nitro-products (4-nitroguaiacol, 4-NG; 6-nitroguaiacol, 6-NG; and 4,6-dinitroguaiacol, 4,6-DNG) were quantified in every aliquot, taken from the reaction mixture, by use of high pressure liquid

  10. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-07-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; conditionally activating organic-inorganic interactions; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 31.4 from benchmark under the rural conditions with 2 ppb isoprene and by factors of 10 71 under various test conditions with 2 10 ppb isoprene and >40% relative humidity while maintaining ±15% deviation. These speed-up methods are applicable to other SOA modules that are based on partitioning theories.

  11. Temporal trends in motor vehicle and secondary organic tracers using in situ methylation thermal desorption GCMS.

    PubMed

    Sheesley, Rebecca J; Deminter, Jeffrey T; Meiritz, Mark; Snyder, David C; Schauer, James J

    2010-12-15

    Organic aerosol measurements with high temporal resolution can differentiate primary organic carbon (POC) from secondary organic carbon (SOC) and can be used to distinguish morning rush hour traffic emissions and subsequent photo-oxidation. In the current study, five hour filter samples were collected during the Summer Study for Organic Aerosols at Riverside (SOAR-1 in CA, USA) for analysis of organic molecular markers. To achieve the low detection limits required for the high temporal resolution data, a laboratory-based in situ methylation thermal desorption gas chromatography-mass spectrometry method was developed. This enabled the measurement of potential markers of SOC, including phthalic acid, along with markers for traffic emissions, including norhopane. The aromatic acids correlated well with unapportioned OC from a molecular marker chemical mass balance model (SOC-cmb; r(2) = 0.46-0.70) and SOC from the elemental carbon tracer method (SOC-ec; r(2) = 0.40-0.56). The aromatic acid/norhopane ratio increased substantially over the course of each day. The average mid-day phthalic acid ratio compared to previously published roadway emissions was a factor of 4 times higher, while the average 1,2,3-benzenetricarboxylic acid ratio was a factor of 40 times higher than roadway emissions. Using correlation plots of SOC-cmb and phthalic acid, it was estimated that 2.9 ± 0.6 μg m(-3) SOC was associated with mid-day aromatic acid production in Riverside. PMID:21105701

  12. Fgf8-Related Secondary Organizers Exert Different Polarizing Planar Instructions along the Mouse Anterior Neural Tube

    PubMed Central

    Crespo-Enriquez, Ivan; Partanen, Juha; Martinez, Salvador; Echevarria, Diego

    2012-01-01

    Early brain patterning depends on proper arrangement of positional information. This information is given by gradients of secreted signaling molecules (morphogens) detected by individual cells within the responding tissue, leading to specific fate decisions. Here we report that the morphogen FGF8 exerts initially a differential signal activity along the E9.5 mouse neural tube. We demonstrate that this polarizing activity codes by RAS-regulated ERK1/2 signaling and depends on the topographical location of the secondary organizers: the isthmic organizer (IsO) and the anterior neural ridge (anr) but not on zona limitans intrathalamica (zli). Our results suggest that Sprouty2, a negative modulator of RAS/ERK pathway, is important for regulating Fgf8 morphogenetic signal activity by controlling Fgf8-induced signaling pathways and positional information during early brain development. PMID:22792203

  13. [Health service organization during the age of pestilence. 2].

    PubMed

    Sabbatani, Sergio

    2003-12-01

    The author presents the history of the places where patients with epidemic pathologies were isolated. Since the study of medicine began, such places have been known as asclepiei, xenodochi, hospices, lazarettos, sanitary cordons, and quarantine stations and they contributed to controlling epidemics in Europe. Important not only in the context in which they were created, these structures expressed the medical culture and point of view of that age. Although very far from discovering the cause of the pathology due to their lack of scientific knowledge, the medical class sometimes knew how to effectively organize the isolation of patients. The history of such structures interweaves with the long history of Christianity and with the emerging nations of Europe and the city-states of the Italian Renaissance. Previously, in classical Greece and Imperial Rome there had also been "homes for the sick" to isolate patients. Today the world is periodically hit by epidemics. In such moments the medical profession uses its research ability and organizational capabilities but also historical memory to reduce epidemic contagion. PMID:14988671

  14. Direct measurement of riverine particulate organic carbon age structure

    NASA Astrophysics Data System (ADS)

    Rosenheim, Brad E.; Galy, Valier

    2012-10-01

    Carbon cycling studies focusing on transport and transformation of terrigenous carbon sources toward marine sedimentary sinks necessitate separation of particulate organic carbon (OC) derived from many different sources and integrated by river systems. Much progress has been made on isolating and characterizing young biologically-formed OC that is still chemically intact, however quantification and characterization of old, refractory rock-bound OC has remained troublesome. Quantification of both endmembers of riverine OC is important to constrain exchanges linking biologic and geologic carbon cycles and regulating atmospheric CO2 and O2. Here, we constrain petrogenic OC proportions in suspended sediment from the headwaters of the Ganges River in Nepal through direct measurement using ramped pyrolysis radiocarbon analysis. The unique results apportion the biospheric and petrogenic fractions of bulk particulate OC and characterize biospheric OC residence time. Compared to the same treatment of POC from the lower Mississippi-Atchafalaya River system, contrast in age spectra of the Ganges tributary samples illustrates the difference between small mountainous river systems and large integrative ones in terms of the global carbon cycle.

  15. Effects of activated carbon ageing in three PCB contaminated sediments: Sorption efficiency and secondary effects on Lumbriculus variegatus.

    PubMed

    Nybom, Inna; Waissi-Leinonen, Greta; Mäenpää, Kimmo; Leppänen, Matti T; Kukkonen, Jussi V K; Werner, David; Akkanen, Jarkko

    2015-11-15

    The sorption efficiency and possible secondary effects of activated carbon (AC) (ø 63-200 μm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs. PMID:26364225

  16. Fourier Transform Infrared Spectroscopy for Identification and Quantification of Organic Functional Groups in Aqueous Phase Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    George, K.; Ruthenburg, T. C.; Smith, J.; Anastasio, C.; Dillner, A. M.

    2011-12-01

    Particles in the atmosphere influence visibility, climate, and human health. Secondary organic aerosols (SOA) formed from chemical reactions in the atmosphere constitute a portion of total organic particle mass. Most research on SOA has focused on gas phase reactions; however, reactions taking place in cloud and fog drops may be significant. One group of water-soluble compounds that participate in these reactions is phenols. Phenols, emitted from biomass burning, react in the aqueous phase to form low-volatility SOA products. The products formed from these reactions are currently poorly characterized. In order to characterize laboratory-generated samples, we are developing an attenuated total reflectance-Fourier transform infrared spectroscopic (ATR-FTIR) technique to identify and quantify organic functional groups in SOA. Aqueous SOA is made in the laboratory by illuminating solutions of phenolic compounds with an oxidant. The illuminated solution is then blown to dryness in order to determine the mass of SOA produced. The dry SOA is reconstituted in water and drops of this solution are placed onto a single-reflection ATR accessory. In order to identify and quantify functional groups in the complex SOA samples, it is necessary to calibrate with compounds and mixtures of compounds containing bond types similar to those found in the laboratory-generated SOA. Initially, focus has been placed on multiple peaks located in the region between 1800 cm-1 and 800 cm-1, including peaks for C=O and C-O. We distinguish between characteristic absorbances to begin determining the organic functional group composition of the SOA samples. This ATR-FTIR technique complements information from mass spectrometry measurements and allows us to quantify organic mass for non-volatile SOA products.

  17. Airborne Measurements of Secondary Organic Aerosol Formation in the Oil Sands Region of Alberta

    NASA Astrophysics Data System (ADS)

    Liggio, J.; Hayden, K.; Liu, P.; Leithead, A.; Moussa, S. G.; Staebler, R. M.; Gordon, M.; O'brien, J.; Li, S. M.

    2014-12-01

    The Alberta oil sands (OS) region represents a strategic natural resource and is a key driver of economic development. Its rapid expansion has led to a need for a more comprehensive understanding of the associated potential cumulative environmental impacts. In summer 2013, airborne measurements of various gaseous and particulate substances were made in the Athabasca oil sands region between August 13 and Sept 7, 2013. In particular, organic aerosol mass and composition measurements were performed with a High Resolution Time of flight Aerosol Mass Spectrometer (HR-ToF-AMS) supported by gaseous measurements of organic aerosol precursors with Proton Transfer Reaction (PTR) and Chemical Ionization (CI) mass spectrometers. These measurement data on selected flights were used to estimate the potential for local anthropogenic OS emissions to form secondary organic aerosol (SOA) downwind of precursor sources, and to investigate the importance of the surrounding biogenic emissions to the overall SOA burden in the region. The results of several flights conducted to investigate these transformations demonstrate that multiple distinct plumes were present downwind of OS industrial sources, each with differing abilities to form SOA depending upon factors such as NOx level, precursor VOC composition, and oxidant concentration. The results indicate that approximately 100 km downwind of an OS industrial source most of the measured organic aerosol (OA) was secondary in nature, forming at rates of ~6.4 to 13.6 μgm-3hr-1. Positive matrix factor (PMF) analysis of the HR-ToF-AMS data suggests that the SOA was highly oxidized (O/C~0.6) resulting in a measured ΔOA (difference above regional background OA) of approximately 2.5 - 3 despite being 100 km away from sources. The relative contribution of biogenic SOA to the total SOA and the factors affecting SOA formation during a number of flights in the OS region will be described.

  18. 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. PMID:26207427

  19. CMAQ model performance enhanced when in-cloud secondary organic aerosol is included: comparisons of organic carbon predictions with measurements.

    PubMed

    Carlton, Annmarie G; Turpin, Barbara I; Altieri, Katye E; Seitzinger, Sybil P; Mathur, Rohit; Roselle, Shawn J; Weber, Rodney J

    2008-12-01

    Mounting evidence suggests that low-volatility (particle-phase) organic compounds form in the atmosphere through aqueous phase reactions in clouds and aerosols. Although some models have begun including secondary organic aerosol (SOA) formation through cloud processing, validation studies that compare predictions and measurements are needed. In this work, agreement between modeled organic carbon (OC) and aircraft measurements of water soluble OC improved for all 5 of the compared ICARTT NOAA-P3 flights during August when an in-cloud SOA (SOAcld) formation mechanism was added to CMAQ (a regional-scale atmospheric model). The improvement was most dramatic for the August 14th flight, a flight designed specifically to investigate clouds. During this flight the normalized mean bias for layer-averaged OC was reduced from -64 to -15% and correlation (r) improved from 0.5 to 0.6. Underpredictions of OC aloft by atmospheric models may be explained, in part, by this formation mechanism (SOAcld). OC formation aloft contributes to long-range pollution transport and has implications to radiative forcing, regional air quality and climate. PMID:19192800

  20. Direct Aqueous Photochemistry of Isoprene High-NOx Secondary Organic Aerosol

    SciTech Connect

    Nguyen, Tran B.; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey

    2012-05-17

    Secondary organic aerosol (SOA) generated from the high-NOx photooxidation of isoprene was dissolved in water and irradiated with {lambda} > 290 nm light to simulate direct photolytic processing of organics in atmospheric water droplets. High-resolution mass spectrometry was used to characterize the composition at four time intervals (0, 1, 2, and 4 h). Photolysis resulted in the decomposition of high molecular weight (MW) oligomers, reducing the average length of organics by 2 carbon units. Approximately 65% by count of SOA molecules decomposed during photolysis, accompanied by the formation of new products. An average of 30 % of the organic mass was modified after 4 h of direct photolysis. In contrast, only a small fraction of the mass (<2 %), belonging primarily to organic nitrates, decomposed in the absence of irradiation by hydrolysis. We observed a statistically-significant increase in average O/C, decrease in H/C, and increase in N/C ratios resulting from photolysis. Furthermore, the concentration of aromatic compounds increased significantly during photolysis. Approximately 10 % of photodegraded compounds and 50 % of the photoproducts contain nitrogen. Organic nitrates and multifunctional oligomers were identified as compounds degraded by photolysis. Low-MW 0N (compounds with 0 nitrogen atoms in their structure) and 2N compounds were the dominant photoproducts. Fragmentation experiments using tandem mass spectrometry (MSn, n = 2-3) indicate that the 2N products are likely heterocyclic/aromatic and are tentatively identified as furoxans. Although the exact mechanism is unclear, these 2N heterocyclic compounds are produced by reactions between photochemically-formed aqueous NOx species and SOA organics.

  1. Molecular characterization of urban organic aerosol in tropical India: contributions of primary emissions and secondary photooxidation

    NASA Astrophysics Data System (ADS)

    Fu, P. Q.; Kawamura, K.; Pavuluri, C. M.; Swaminathan, T.; Chen, J.

    2010-03-01

    Organic molecular composition of PM10 samples, collected at Chennai in tropical India, was studied using capillary gas chromatography/mass spectrometry. Fourteen organic compound classes were detected in the aerosols, including aliphatic lipids, sugar compounds, lignin products, terpenoid biomarkers, sterols, aromatic acids, hydroxy-/polyacids, phthalate esters, hopanes, Polycyclic Aromatic Hydrocarbons (PAHs), and photooxidation products from biogenic Volatile Organic Compounds (VOCs). At daytime, phthalate esters were found to be the most abundant compound class; however, at nighttime, fatty acids were the dominant one. Di-(2-ethylhexyl) phthalate, C16 fatty acid, and levoglucosan were identified as the most abundant single compounds. The nighttime maxima of most organics in the aerosols indicate a land/sea breeze effect in tropical India, although some other factors such as local emissions and long-range transport may also influence the composition of organic aerosols. However, biogenic VOC oxidation products (e.g., 2-methyltetrols, pinic acid, 3-hydroxyglutaric acid and β-caryophyllinic acid) showed diurnal patterns with daytime maxima. Interestingly, terephthalic acid was maximized at nighttime, which is different from those of phthalic and isophthalic acids. A positive relation was found between 1,3,5-triphenylbenzene (a tracer for plastic burning) and terephthalic acid, suggesting that the field burning of municipal solid wastes including plastics is a significant source of terephthalic acid. Organic compounds were further categorized into several groups to clarify their sources. Fossil fuel combustion (24-43%) was recognized as the most significant source for the total identified compounds, followed by plastic emission (16-33%), secondary oxidation (8.6-23%), and microbial/marine sources (7.2-17%). In contrast, the contributions of terrestrial plant waxes (5.9-11%) and biomass burning (4.2-6.4%) were relatively small. This study demonstrates that, in

  2. 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

  3. Impacts of Sulfate Seed Acidity and Water Content on Isoprene Secondary Organic Aerosol Formation.

    PubMed

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

    2015-11-17

    The effects of particle-phase water and the acidity of pre-existing sulfate seed particles on the formation of isoprene secondary organic aerosol (SOA) was investigated. SOA was generated from the photo-oxidation of isoprene in a flow tube reactor at 70% relative humidity (RH) and room temperature in the presence of three different sulfate seeds (effloresced and deliquesced ammonium sulfate and ammonium bisulfate) under low NOx conditions. High OH exposure conditions lead to little isoprene epoxydiol (IEPOX) SOA being generated. The primary result is that particle-phase water had the largest effect on the amount of SOA formed, with 60% more SOA formation occurring with deliquesced ammonium sulfate seeds as compared to that on effloresced ones. The additional organic material was highly oxidized. Although the amount of SOA formed did not exhibit a dependence on the range of seed particle acidity examined, perhaps because of the low amount of IEPOX SOA, the levels of high-molecular-weight material increased with acidity. While the uptake of organics was partially reversible under drying, the results nevertheless indicate that particle-phase water enhanced the amount of organic aerosol material formed and that the RH cycling of sulfate particles may mediate the extent of isoprene SOA formation in the atmosphere. PMID:26460477

  4. Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    Reactive halogen species (RHS), such as X·, X2 and HOX containing X = chlorine and/or bromine, are released by various sources like photo-activated sea-salt aerosol or from salt pans, and salt lakes. Despite many studies of RHS reactions, the potential of RHS reacting with secondary organic aerosol (SOA) and organic aerosol derived from biomass-burning (BBOA) has been neglected. Such reactions can constitute sources of gaseous organohalogen compounds or halogenated organic matter in the tropospheric boundary layer and can influence physicochemical properties of atmospheric aerosols. Model SOA from α-pinene, catechol, and guaiacol was used to study heterogeneous interactions with RHS. Particles were exposed to molecular chlorine and bromine in an aerosol smog-chamber in the presence of UV/VIS irradiation and to RHS released from simulated natural halogen sources like salt pans. Subsequently the aerosol was characterized in detail using a variety of physicochemical and spectroscopic methods. Fundamental features were correlated with heterogeneous halogenation, which result in new functional groups, changed UV/VIS absorption, or aerosol size distribution. However, the halogen release mechanisms were also found to be affected by the presence of organic aerosol. Those interaction processes, changing chemical and physical properties of the aerosol are likely to influence e.g. the ability of the aerosol to act as cloud condensation nuclei, its potential to adsorb other gases with low-volatility, or its contribution to radiative forcing and ultimately the Earth's radiation balance.

  5. The Effect of Solvent on the Analysis of Secondary Organic Aerosol Using Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Bateman, Adam P.; Walser, Maggie L.; Dessiaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Serguei

    2008-08-29

    Solvent-analyte reactions in organic aerosol (OA) extracts prepared for analysis by electrospray ionization mass spectrometry (ESI-MS) were examined. Secondary organic aerosol (SOA) produced by ozonation of d-limonene as well as several test organic chemicals with functional groups typical for OA constituents were dissolved and stored in methanol, d3-methanol, acetonitrile, and d3-acetonitrile to investigate the extent and relative rates of reactions between analyte and solvent. High resolution ESI-MS showed that reactions of carbonyls with methanol produce significant amounts of hemiacetals and acetals on time scales ranging from several minutes to several days, with the reaction rates increasing in acidified solutions. Carboxylic acid groups were observed to react with methanol resulting in the formation of esters. In contrast, acetonitrile extracts showed no evidence of reactions with analyte molecules, suggesting that acetonitrile is the preferred solvent for SOA extraction. The use of solvent-analyte reactivity as an analytical chemistry tool for the improved characterization of functional groups in complex organic mixtures was also demonstrated. Direct comparison between ESI mass spectra of the same SOA samples extracted in reactive (methanol) versus non-reactive (acetonitrile) solvents was used to estimate the relative fractions of ketones (≥38%), aldehydes (≥6%), and carboxylic acids (≥55%) in d-limonene SOA.

  6. Effect of NOx level on secondary organic aerosol (SOA) formation from the photooxidation of terpenes

    NASA Astrophysics Data System (ADS)

    Ng, N. L.; Chhabra, P. S.; Chan, A. W. H.; Surratt, J. D.; Kroll, J. H.; Kwan, A. J.; McCabe, D. C.; Wennberg, P. O.; Sorooshian, A.; Murphy, S. M.; Dalleska, N. F.; Flagan, R. C.; Seinfeld, J. H.

    2007-10-01

    Secondary organic aerosol (SOA) formation from the photooxidation of one monoterpene (α-pinene) and two sesquiterpenes (longifolene and aromadendrene) is investigated in the Caltech environmental chambers. The effect of NOx on SOA formation for these biogenic hydrocarbons is evaluated by performing photooxidation experiments under varying NOx conditions. The NOx dependence of α-pinene SOA formation follows the same trend as that observed previously for a number of SOA precursors, including isoprene, in which SOA yield (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) decreases as NOx level increases. The NOx dependence of SOA yield for the sesquiterpenes, longifolene and aromadendrene, however, differs from that determined for isoprene and α-pinene; the aerosol yield under high-NOx conditions substantially exceeds that under low-NOx conditions. The reversal of the NOx dependence of SOA formation for the sesquiterpenes is consistent with formation of relatively low-volatility organic nitrates, and/or the isomerization of large alkoxy radicals leading to less volatile products. Analysis of the aerosol chemical composition for longifolene confirms the presence of organic nitrates under high-NOx conditions. Consequently the formation of SOA from certain biogenic hydrocarbons such as sesquiterpenes (and possibly large anthropogenic hydrocarbons as well) may be more efficient in polluted air.

  7. Density and elemental ratios of secondary organic aerosol: Application of a density prediction method

    NASA Astrophysics Data System (ADS)

    Nakao, Shunsuke; Tang, Ping; Tang, Xiaochen; Clark, Christopher H.; Qi, Li; Seo, Eric; Asa-Awuku, Akua; Cocker, David

    2013-04-01

    Organic material density is a fundamental parameter in aerosol science, yet direct measurement is not readily available. This study investigates density and elemental ratios of secondary organic aerosol (SOA) formed by the oxidation of 22 different volatile organic compounds with a wide range of molecular size (C5˜C15) in an environmental chamber. Reactants with a larger number of carbons yielded SOA with lower density (e.g., β-caryophyllene SOA: 1.22 g cm-3) compared with smaller ones (e.g., phenol SOA: 1.43 g cm-3) consistent with different extents of oxidation of the parent molecule. A recent study proposed a semi-empirical relationship between elemental ratios (O/C and H/C) and organic material density (Kuwata et al., 2012). The prediction method therein is evaluated against the large experimental data set of this study acquired in the UC Riverside/CE-CERT environmental chamber. The predicted particle densities agree with experimental measurements within 12% as stated by Kuwata et al. (2012) except for C6 compounds (benzene, phenol, and catechol). Therefore, the range of application has been further extended to include anthropogenic (aromatic) systems. The effects of nitrogen and sulfur on the density prediction remain unclear.

  8. Contributions of Acid-Catalysed Processes to Secondary Organic Aerosol Mass - A Modelling pproach

    NASA Astrophysics Data System (ADS)

    Ervens, B.; Feingold, G.; Kreidenweis, S. M.

    2005-12-01

    A significant fraction of secondary organic aerosol (SOA) mass is formed by chemical and/or physical processes. However, the amount of organic material found in ambient organic aerosols cannot be explained with current models. Recently, several laboratory studies have been published which suggest that also acid-catalyzed processes that occur either in particles or at their surfaces (heterogeneous) might contribute significantly to mass formation. However, to date there is no general conclusion about the efficiency of such processes due to the great diversity of species and experimental conditions. We present a compilation of literature data (thermodynamic and kinetic) of these processes. The aerosol yields of (i) additional species which are thought previously not contribute to SOA formation (e.g. isoprene, aliphatic aldehydes) and (ii) species which form apparently higher SOA masses on acidic seed aerosols are reported and compared to input data of previous SOA models. Available kinetic data clearly exclude aldol condensation as a significant process for SOA formation on a time scale of typical aerosol life times. Using aerosol size distributions and gas phase concentrations measured during NEAQS2002 as model input data, we show that (even under assumption of equilibrium conditions) these additional processes only contribute a minor fraction to the organic aerosol mass.

  9. 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. PMID:26578760

  10. The formation, properties and impact of secondary organic aerosol: current and emerging issues

    NASA Astrophysics Data System (ADS)

    Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, Th. F.; Monod, A.; Prévôt, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J.

    2009-02-01

    Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with a description of the current state of knowledge on the global SOA budget and the atmospheric degradation mechanisms for SOA precursors. The topic of gas-particle partitioning theory is followed by an account of the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail; molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

  11. The formation, properties and impact of secondary organic aerosol: current and emerging issues

    NASA Astrophysics Data System (ADS)

    Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, Th. F.; Monod, A.; Prévôt, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J.

    2009-07-01

    Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

  12. Quantifying the effect of organic aerosol aging and intermediate-volatility emissions on regional-scale aerosol pollution in China

    NASA Astrophysics Data System (ADS)

    Zhao, Bin; Wang, Shuxiao; Donahue, Neil M.; Jathar, Shantanu H.; Huang, Xiaofeng; Wu, Wenjing; Hao, Jiming; Robinson, Allen L.

    2016-06-01

    Secondary organic aerosol (SOA) is one of the least understood constituents of fine particles; current widely-used models cannot predict its loadings or oxidation state. Recent laboratory experiments demonstrated the importance of several new processes, including aging of SOA from traditional precursors, aging of primary organic aerosol (POA), and photo-oxidation of intermediate volatility organic compounds (IVOCs). However, evaluating the effect of these processes in the real atmosphere is challenging. Most models used in previous studies are over-simplified and some key reaction trajectories are not captured, and model parameters are usually phenomenological and lack experimental constraints. Here we comprehensively assess the effect of organic aerosol (OA) aging and intermediate-volatility emissions on regional-scale OA pollution with a state-of-the-art model framework and experimentally constrained parameters. We find that OA aging and intermediate-volatility emissions together increase OA and SOA concentrations in Eastern China by about 40% and a factor of 10, respectively, thereby improving model-measurement agreement significantly. POA and IVOCs both constitute over 40% of OA concentrations, and IVOCs constitute over half of SOA concentrations; this differs significantly from previous apportionment of SOA sources. This study facilitates an improved estimate of aerosol-induced climate and health impacts, and implies a shift from current fine-particle control policies.

  13. Quantifying the effect of organic aerosol aging and intermediate-volatility emissions on regional-scale aerosol pollution in China.

    PubMed

    Zhao, Bin; Wang, Shuxiao; Donahue, Neil M; Jathar, Shantanu H; Huang, Xiaofeng; Wu, Wenjing; Hao, Jiming; Robinson, Allen L

    2016-01-01

    Secondary organic aerosol (SOA) is one of the least understood constituents of fine particles; current widely-used models cannot predict its loadings or oxidation state. Recent laboratory experiments demonstrated the importance of several new processes, including aging of SOA from traditional precursors, aging of primary organic aerosol (POA), and photo-oxidation of intermediate volatility organic compounds (IVOCs). However, evaluating the effect of these processes in the real atmosphere is challenging. Most models used in previous studies are over-simplified and some key reaction trajectories are not captured, and model parameters are usually phenomenological and lack experimental constraints. Here we comprehensively assess the effect of organic aerosol (OA) aging and intermediate-volatility emissions on regional-scale OA pollution with a state-of-the-art model framework and experimentally constrained parameters. We find that OA aging and intermediate-volatility emissions together increase OA and SOA concentrations in Eastern China by about 40% and a factor of 10, respectively, thereby improving model-measurement agreement significantly. POA and IVOCs both constitute over 40% of OA concentrations, and IVOCs constitute over half of SOA concentrations; this differs significantly from previous apportionment of SOA sources. This study facilitates an improved estimate of aerosol-induced climate and health impacts, and implies a shift from current fine-particle control policies. PMID:27350423

  14. Quantifying the effect of organic aerosol aging and intermediate-volatility emissions on regional-scale aerosol pollution in China

    PubMed Central

    Zhao, Bin; Wang, Shuxiao; Donahue, Neil M.; Jathar, Shantanu H.; Huang, Xiaofeng; Wu, Wenjing; Hao, Jiming; Robinson, Allen L.

    2016-01-01

    Secondary organic aerosol (SOA) is one of the least understood constituents of fine particles; current widely-used models cannot predict its loadings or oxidation state. Recent laboratory experiments demonstrated the importance of several new processes, including aging of SOA from traditional precursors, aging of primary organic aerosol (POA), and photo-oxidation of intermediate volatility organic compounds (IVOCs). However, evaluating the effect of these processes in the real atmosphere is challenging. Most models used in previous studies are over-simplified and some key reaction trajectories are not captured, and model parameters are usually phenomenological and lack experimental constraints. Here we comprehensively assess the effect of organic aerosol (OA) aging and intermediate-volatility emissions on regional-scale OA pollution with a state-of-the-art model framework and experimentally constrained parameters. We find that OA aging and intermediate-volatility emissions together increase OA and SOA concentrations in Eastern China by about 40% and a factor of 10, respectively, thereby improving model-measurement agreement significantly. POA and IVOCs both constitute over 40% of OA concentrations, and IVOCs constitute over half of SOA concentrations; this differs significantly from previous apportionment of SOA sources. This study facilitates an improved estimate of aerosol-induced climate and health impacts, and implies a shift from current fine-particle control policies. PMID:27350423

  15. Characterizing the aging of biomass burning organic aerosol by use of mixing ratios: a meta-analysis of four regions.

    PubMed

    Jolleys, Matthew D; Coe, Hugh; McFiggans, Gordon; Capes, Gerard; Allan, James D; Crosier, Jonathan; Williams, Paul I; Allen, Grant; Bower, Keith N; Jimenez, Jose L; Russell, Lynn M; Grutter, Michel; Baumgardner, Darrel

    2012-12-18

    Characteristic organic aerosol (OA) emission ratios (ERs) and normalized excess mixing ratios (NEMRs) for biomass burning (BB) events have been calculated from ambient measurements recorded during four field campaigns. Normalized OA mass concentrations measured using Aerodyne Research Inc. quadrupole aerosol mass spectrometers (Q-AMS) reveal a systematic variation in average values between different geographical regions. For each region, a consistent, characteristic ratio is seemingly established when measurements are collated from plumes of all ages and origins. However, there is evidence of strong regional and local-scale variability between separate measurement periods throughout the tropical, subtropical, and boreal environments studied. ERs close to source typically exceed NEMRs in the far-field, despite apparent compositional change and increasing oxidation with age. The absence of any significant downwind mass enhancement suggests no regional net source of secondary organic aerosol (SOA) from atmospheric aging of BB sources, in contrast with the substantial levels of net SOA formation associated with urban sources. A consistent trend of moderately reduced ΔOA/ΔCO ratios with aging indicates a small net loss of OA, likely as a result of the evaporation of organic material from initial fire emissions. Variability in ERs close to source is shown to substantially exceed the magnitude of any changes between fresh and aged OA, emphasizing the importance of fuel and combustion conditions in determining OA loadings from biomass burning. PMID:23163290

  16. Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume

    SciTech Connect

    Lee-Taylor, J.; Madronich, Sasha; Aumont, B.; Baker, A.; Camredon, M.; Hodzic, Alma; Tyndall, G. S.; Apel, Eric; Zaveri, Rahul A.

    2011-12-21

    The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15-20 ug m-3, and SOA peaking at 10-15 μg m-3 during mid-day. The majority (> 75%) of the model SOA stems from the large n-alkanes, with the remainder mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by *- hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.

  17. Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume

    NASA Astrophysics Data System (ADS)

    Lee-Taylor, J.; Madronich, S.; Aumont, B.; Baker, A.; Camredon, M.; Hodzic, A.; Tyndall, G. S.; Apel, E.; Zaveri, R. A.

    2011-12-01

    The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15-20 μg m-3, and SOA peaking at 10-15 μg m-3 during mid-day. The majority (≥75%) of the model SOA stems from reaction products of the large n-alkanes, used here as surrogates for all emitted hydrocarbons of similar volatility, with the remaining SOA originating mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by δ-hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.

  18. 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

  19. Simulation Chamber Investigations of Secondary Organic Aerosol Formation From Boreal Tree Emissions: Dependence on VOC Classes

    NASA Astrophysics Data System (ADS)

    Kiendler-Scharr, A.; Mentel, T. F.; Kleist, E.; Hohaus, T.; Mensah, A.; Spindler, C.; Tillmann, R.; Uerlings, R.; Dal Maso, M.; Rudich, Y.; Juergen, W.

    2008-12-01

    A considerable fraction of the organic aerosol component is of secondary origin, meaning it is formed through oxidation of volatile organic compounds (VOCs). Plant emissions, e.g. monoterpenes and sesquiterpenes, are a major source of VOCs in the troposphere. So far most laboratory and simulation chamber investigations on the potential to form secondary organic aerosols (SOA) from plant emissions focused on single VOCs such as a-pinene. In this study we investigated the formation and growth of SOA by ozonolysis and/or photo-oxidation of the VOCs emitted by several tree species such as spruce, pine and birch. The experiments were performed in the Plant chamber of the ICG-3 in Jülich under well defined conditions for the plant. VOC emissions were transferred to a reaction chamber which was operated as a continuously stirred tank reactor. SOA formation from the VOCs was initiated by an excess of ozone and OH radicals. The results are compared to a reference study with a-pinene as the only SOA precursor. Our results indicate that the general laboratory approach of studying the formation of SOA from single components can lead to a bias in both the mass yields and the mass spectral signatures observed. Plots of maximum SOA volumes versus the total amount of carbon fed into the reaction chamber led to approximately linear relationships. The intercepts of these plots were seen as threshold for SOA formation. It was observed that this threshold was lower for the mixture of VOCs emitted from spruce, pine, and birch than for a-pinene as single compound. We therefore conclude that the threshold for SOA formation from real plant mixtures may be much lower than the threshold obtained from laboratory experiments that were focussed on single VOCs. SOA formation from stress induced VOCs will be compared to non stress induced emissions. Possible feedbacks of climate change to VOC emissions and aerosol formation will be discussed based on our experimental observations.

  20. Significant Contributions of Isoprene to Summertime Secondary Organic Aerosol in Eastern United States.

    PubMed

    Ying, Qi; Li, Jingyi; Kota, Sri Harsha

    2015-07-01

    A modified SAPRC-11 (S11) photochemical mechanism with more detailed treatment of isoprene oxidation chemistry and additional secondary organic aerosol (SOA) formation through surface-controlled reactive uptake of dicarbonyls, isoprene epoxydiol and methacrylic acid epoxide was incorporated in the Community Multiscale Air Quality Model (CMAQ) to quantitatively determine contributions of isoprene to summertime ambient SOA concentrations in the eastern United States. The modified model utilizes a precursor-origin resolved approach to determine secondary glyoxal and methylglyoxal produced by oxidation of isoprene and other major volatile organic compounds (VOCs). Predicted OC concentrations show good agreement with field measurements without significant bias (MFB ∼ 0.07 and MFE ∼ 0.50), and predicted SOA reproduces observed day-to-day and diurnal variation of Oxygenated Organic Aerosol (OOA) determined by an aerosol mass spectrometer (AMS) at two locations in Houston, Texas. On average, isoprene SOA accounts for 55.5% of total predicted near-surface SOA in the eastern U.S., followed by aromatic compounds (13.2%), sesquiterpenes (13.0%) and monoterpenes (10.9%). Aerosol surface uptake of isoprene-generated glyoxal, methylglyoxal and epoxydiol accounts for approximately 83% of total isoprene SOA or more than 45% of total SOA. A domain wide reduction of NOx emissions by 40% leads to a slight decrease of domain average SOA by 3.6% and isoprene SOA by approximately 2.6%. Although most of the isoprene SOA component concentrations are decreased, SOA from isoprene epoxydiol is increased by ∼16%. PMID:26029963

  1. Final Report, The Influence of Organic-Aerosol Emissions and Aging on Regional and Global Aerosol Size Distributions and the CCN Number Budget

    SciTech Connect

    Donahue, Neil M.

    2015-12-23

    We conducted laboratory experiments and analyzed data on aging of organic aerosol and analysis of field data on volatility and CCN activity. With supplemental ASR funding we participated in the FLAME-IV campaign in Missoula MT in the Fall of 2012, deploying a two-chamber photochemical aging system to enable experimental exploration of photochemical aging of biomass burning emissions. Results from that campaign will lead to numerous publications, including demonstration of photochemical production of Brown Carbon (BrC) from secondary organic aerosol associated with biomass burning emissions as well as extensive characterization of the effect of photochemical aging on the overall concentrations of biomass burning organic aerosol. Excluding publications arising from the FLAME-IV campaign, project research resulted in 8 papers: [11, 5, 3, 10, 12, 4, 8, 7], including on in Nature Geoscience addressing the role of organic compounds in nanoparticle growth [11

  2. Contributions of Biogenic and Anthropogenic Hydrocarbons to Secondary Organic Aerosol during 2006 in Research Triangle Park, NC

    EPA Science Inventory

    A recently developed, organic tracer-based method was used to estimate the secondary contributions of biogenic and anthropogenic precursor hydrocarbons to ambient organic carbon concentrations in PM2.5 during 2006 in Research Triangle Park, North Carolina, USA. Forty-s...

  3. 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...

  4. The kindness of strangers: organ transplantation in a capitalist age.

    PubMed

    Shannon, T A

    2001-09-01

    The topic of organ transplantation is examined from the perspective of three authors: Robert Bellah, Jeremy Rifkin, and Margaret Jane Radin. Introduced by reflections on the development of the justification of organ transplantation within the Roman Catholic community and the various themes raised by the historical study in Richard Titmuss's The Gift Relationship, the paper examines how and in what ways the possible commodification of organs will affect our society and the impacts this may have on the supply of organs. PMID:11700684

  5. 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. PMID:25002466

  6. Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.

    PubMed

    Zhao, Yunliang; Kreisberg, Nathan M; Worton, David R; Isaacman, Gabriel; Weber, Robin J; Liu, Shang; Day, Douglas A; Russell, Lynn M; Markovic, Milos Z; VandenBoer, Trevor C; Murphy, Jennifer G; Hering, Susanne V; Goldstein, Allen H

    2013-04-16

    In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA. PMID:23448102

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

    PubMed Central

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

    2014-01-01

    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. PMID:25002466

  8. Acute respiratory failure caused by organizing pneumonia secondary to antineoplastic therapy for non-Hodgkin's lymphoma

    PubMed Central

    Santana, Adriell Ramalho; Amorim, Fábio Ferreira; Soares, Paulo Henrique Alves; de Moura, Edmilson Bastos; Maia, Marcelo de Oliveira

    2012-01-01

    Interstitial lung diseases belong to a group of diseases that typically exhibit a subacute or chronic progression but that may cause acute respiratory failure. The male patient, who was 37 years of age and undergoing therapy for non-Hodgkin's lymphoma, was admitted with cough, fever, dyspnea and acute hypoxemic respiratory failure. Mechanical ventilation and antibiotic therapy were initiated but were associated with unfavorable progression. Thoracic computed tomography showed bilateral pulmonary "ground glass" opacities. Methylprednisolone pulse therapy was initiated with satisfactory response because the patient had used three drugs related to organizing pneumonia (cyclophosphamide, doxorubicin and rituximab), and the clinical and radiological symptoms were suggestive. Organizing pneumonia may be idiopathic or linked to collagen diseases, drugs and cancer and usually responds to corticosteroid therapy. The diagnosis was anatomopathological, but the patient's clinical condition precluded performing a lung biopsy. Organizing pneumonia should be a differential diagnosis in patients with apparent pneumonia and a progression that is unfavorable to antimicrobial treatment. PMID:23917942

  9. Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Finessi, E.; Decesari, S.; Paglione, M.; Giulianelli, L.; Carbone, C.; Gilardoni, S.; Fuzzi, S.; Saarikoski, S.; Raatikainen, T.; Hillamo, R.; Allan, J.; Mentel, Th. F.; Tiitta, P.; Laaksonen, A.; Petäjä, T.; Kulmala, M.; Worsnop, D. R.; Facchini, M. C.

    2012-01-01

    The study investigates the sources of fine organic aerosol (OA) in the boreal forest, based on measurements including both filter sampling (PM1) and online methods and carried out during a one-month campaign held in Hyytiälä, Finland, in spring 2007. Two aerosol mass spectrometers (Q-AMS, ToF-AMS) were employed to measure on-line concentrations of major non-refractory aerosol species, while the water extracts of the filter samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy for organic functional group characterization of the polar organic fraction of the aerosol. AMS and NMR spectra were processed separately by non-negative factorization algorithms, in order to apportion the main components underlying the submicrometer organic aerosol composition and depict them in terms of both mass fragmentation patterns and functional group compositions. The NMR results supported the AMS speciation of oxidized organic aerosol (OOA) into two main fractions, which could be generally labelled as more and less oxidized organics. The more oxidized component was characterized by a mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR spectrum showing aromatic and aliphatic backbones highly substituted with oxygenated functional groups (carbonyls/carboxyls and hydroxyls). Such component, contributing on average 50% of the OA mass throughout the observing period, was associated with pollution outbreaks from the Central Europe. The less oxidized component was enhanced in concomitance with air masses originating from the North-to-West sector, in agreement with previous investigations conducted at this site. NMR factor analysis was able to separate two distinct components under the less oxidized fraction of OA. One of these NMR-factors was associated with the formation of terrestrial biogenic secondary organic aerosol (BSOA), based on the comparison with spectral profiles obtained from laboratory experiments of terpenes photo-oxidation. The second NMR

  10. Implications of Graphic Organizers in an Age of Social Media

    ERIC Educational Resources Information Center

    Record, Michael

    2015-01-01

    The term graphic organizer has become so commonplace in teaching that the meaning of the term, as well as the rationale for why the strategy works, has become lost. Revisiting the general concept of an advance organizer is an opportunity to consider the essential teaching act. There is a difference between "using a graphic organizer" in…

  11. Heterogeneous ice nucleation and phase transition of viscous α-pinene secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Ignatius, Karoliina; Kristensen, Thomas B.; Järvinen, Emma; Nichman, Leonid; Fuchs, Claudia; Gordon, Hamish; Herenz, Paul; Hoyle, Christopher R.; Duplissy, Jonathan; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Gallagher, Martin W.; Kirkby, Jasper; Kulmala, Markku; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Virtanen, Annele; Stratmann, Frank

    2016-04-01

    There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate deposition ice nucleation and thus influence cirrus cloud properties. Global model simulations of monoterpene SOA particles suggest that viscous biogenic SOA are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle (INP) budget. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles at the CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN (Ignatius et al., 2015, Järvinen et al., 2015). In the CLOUD chamber, the SOA particles were produced from the ozone initiated oxidation of α-pinene at temperatures in the range from -38 to -10° C at 5-15 % relative humidity with respect to water (RHw) to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. We found that particles formed and grown in the chamber developed an asymmetric shape through coagulation. As the RHw was increased to between 35 % at -10° C and 80 % at -38° C, a transition to spherical shape was observed with a new in-situ optical method. This transition confirms previous modelling of the viscosity transition conditions. The ice nucleation ability of SOA particles was investigated with a new continuous flow diffusion chamber SPIN (Spectrometer for Ice Nuclei) for different SOA particle sizes. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA in the deposition mode for ice saturation ratios between 1.3 and 1.4, significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between -36.5 and -38.3° C ranged from 6 to 20 % and did not depend on the particle surface area. References Ignatius, K. et al., Heterogeneous ice

  12. Seasonal variations of biogenic secondary organic aerosol tracers in ambient aerosols from Alaska

    NASA Astrophysics Data System (ADS)

    Haque, Md. Mozammel; Kawamura, Kimitaka; Kim, Yongwon

    2016-04-01

    We investigated total suspended particles (TSP) collected from central Alaska, USA for molecular compositions of secondary organic aerosol (SOA) derived from the oxidation of biogenic volatile organic compounds (BVOCs). Isoprene-, α-/β-pinene- and β-caryophyllene-SOA tracers were determined using gas chromatography-mass spectrometry. The concentration ranges of isoprene, α-/β-pinene and β-caryophyllene oxidation products were 0.02-18.6 ng m-3 (ave. 4.14 ng m-3), 0.42-8.24 ng m-3 (2.01 ng m-3) and 0.10-9 ng m-3 (1.53 ng m-3), respectively. Isoprene-SOA tracers showed higher concentrations in summer (ave. 8.77 ng m-3), whereas α-/β-pinene- and β-caryophyllene-SOA tracers exhibited highest levels in spring (3.55 ng m-3) and winter (4.04 ng m-3), respectively. β-Caryophyllinic acid and levoglucosan showed a positive correlation, indicating that biomass burning may be a major source for β-caryophyllene. We found that mean contributions of isoprene oxidation products to organic carbon (OC) and water-soluble organic (WSOC) (0.56% and 1.2%, respectively) were higher than those of α-/β-pinene (0.31% and 0.55%) and β-caryophyllene (0.08% and 0.13%). Using a tracer-based method, we estimated the concentrations of secondary organic carbon (SOC) produced from isoprene, α-/β-pinene and β-caryophyllene to be 0.66-718 ngC m-3 (ave. 159 ngC m-3), 7.4-143 ngC m-3 (35 ngC m-3) and 4.5-391 ngC m-3 (66.3 ngC m-3), respectively. Based on SOA tracers, this study suggests that isoprene is a more important precursor for the production of biogenic SOA than α-/β-pinene and β-caryophyllene in subarctic Alaska.

  13. 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.

  14. Secondary organic aerosol formation from m-xylene photooxidation: The role of the phenolic product

    NASA Astrophysics Data System (ADS)

    Nakao, S.; Qi, L.; Clark, C.; Sato, K.; Tang, P.; Cocker, D.

    2009-12-01

    Aromatic hydrocarbons comprise a significant fraction of volatile organic compounds in the urban atmosphere and their importance as precursors to secondary organic aerosols (SOA) has been widely recognized. However, SOA formation from aromatics is one of the least understood processes among all the classes of volatile organic compounds (VOCs) due to its complex multi-generation reactions. Phenolic compounds have been identified as one of the significant products from OH-initiated reaction of aromatic hydrocarbons and are suggested to have a very high potential of SOA formation (e.g., cresol isomers having SOA yield 9~42%, Henry et al., Atmos. Environ., 2008). We examined the effect of extent of oxidation of m-xylene on chemical composition and physical properties using m-xylene and xylenol as reactants in environmental chamber experiments. Chemical composition of SOA was investigated by Liquid Chromatography / Time of Flight Mass Spectrometer (LC/ToF-MS), and Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Physical properties of SOA such as density, volatility, and hygroscopicity were investigated by Aerosol Particle Mass Analyzer - Scanning Mobility Particle Sizer (APM-SMPS), Hygroscopicity/Volatility - Tandem Differential Mobility Analyzer (H/V-TDMA), respectively. Also SOA yields were obtained to evaluate the importance of xylenol as an intermediate product.

  15. Electrochemical properties of new organic radical materials for lithium secondary batteries

    NASA Astrophysics Data System (ADS)

    Lee, Seo Hwan; Kim, Jae-Kwang; Cheruvally, Gouri; Choi, Jae-Won; Ahn, Jou-Hyeon; Chauhan, Ghanshyam S.; Song, Choong Eui

    The use of ionic liquid (IL)-supported organic radicals as cathode-active materials in lithium secondary batteries is reported in this article. Two different types of IL-supported organic radicals based on the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radical and imidazolium hexafluorophosphate IL were synthesized. The first type is a mono-radical with one unit of TEMPO and the second is a symmetrical di-radical with 2 U of TEMPO; both are viscous liquids at 25 °C. The radicals exhibit electrochemical activity at ∼3.5 V versus Li/Li + as revealed in the cyclic voltammetry tests. The organic radical batteries (ORBs) with these materials as the cathode, a lithium metal anode and 1 M LiPF 6 in EC/DMC electrolyte exhibited good performance at room temperature during the charge-discharge and cycling tests. The batteries exhibited specific capacities of 59 and 80 mAh g -1 at 1 C-rate with the mono- and di-radicals as the cathodes, respectively, resulting in 100% utilization of the materials. The performance degradation with increasing C-rate is very minimal for the ORBs, thus demonstrating good rate capability.

  16. Secondary Organic Aerosol formation from isoprene photooxidation during cloud condensation-evaporation cycles

    NASA Astrophysics Data System (ADS)

    Brégonzio-Rozier, L.; Giorio, C.; Siekmann, F.; Pangui, E.; Morales, S. B.; Temime-Roussel, B.; Gratien, A.; Michoud, V.; Cazaunau, M.; DeWitt, H. L.; Tapparo, A.; Monod, A.; Doussin, J.-F.

    2015-07-01

    The impact of cloud events on isoprene secondary organic aerosol (SOA) formation has been studied from an isoprene/NOx/light system in an atmospheric simulation chamber. It was shown that the presence of a liquid water cloud leads to a faster and higher SOA formation than under dry conditions. When a cloud is generated early in the photooxidation reaction, before any SOA formation has occurred, a fast SOA formation is observed with mass yields ranging from 0.002 to 0.004. These yields are two and four times higher than those observed under dry conditions. When the cloud is generated at a later photooxidation stage, after isoprene SOA is stabilized at its maximum mass concentration, a rapid increase (by a factor of two or higher) of the SOA mass concentration is observed. The SOA chemical composition is influenced by cloud generation: the additional SOA formed during cloud events is composed of both organics and nitrate containing species. This SOA formation can be linked to water soluble volatile organic compounds (VOCs) dissolution in the aqueous phase and to further aqueous phase reactions. Cloud-induced SOA formation is experimentally demonstrated in this study, thus highlighting the importance of aqueous multiphase systems in atmospheric SOA formation estimations.

  17. Secondary organic aerosol and the burning question of gasoline vs. diesel

    NASA Astrophysics Data System (ADS)

    Gentner, D. R.; Isaacman, G.; Worton, D. R.; Chan, A. W.; Dallmann, T. R.; Davis, L.; Liu, S.; Day, D. A.; Russell, L. M.; Wilson, K. R.; Weber, R.; Guha, A.; Harley, R. A.; Goldstein, A. H.

    2012-12-01

    Emissions from gasoline and diesel vehicles are predominant anthropogenic sources of reactive gas-phase organic carbon and key precursors to Secondary Organic Aerosol (SOA) in urban areas. Their relative importance for aerosol formation is a controversial issue with implications for air quality control policy and public health. Using novel gas chromatography and mass spectrometry methods, we analyzed liquid gasoline and diesel fuel collected across the state of California during Summer 2010 and used it to assess field data from the CalNex (California at the Nexus of Air Quality and Climate Change) Bakersfield supersite and the Caldecott Tunnel in Oakland, CA. We present the most comprehensive data to date on the chemical composition, mass distribution, emissions, and SOA formation potential of gasoline and diesel sources. We find that diesel exhaust is 7 times more efficient at forming aerosol than gasoline exhaust and emits twice as much gas-phase organic carbon per liter of fuel burned. Yet, both sources are important for air quality; depending on a region's fuel use, diesel is responsible for 65-90% of vehicular-derived SOA, with substantial contributions from both aromatic and aliphatic hydrocarbons. We assess our results in the context of other studies and discuss their implications for regional air pollution policies, fuel regulations, and methodologies for future measurement, laboratory, and modeling studies.

  18. Secondary organic aerosol formation from isoprene photooxidation during cloud condensation-evaporation cycles

    NASA Astrophysics Data System (ADS)

    Brégonzio-Rozier, L.; Giorio, C.; Siekmann, F.; Pangui, E.; Morales, S. B.; Temime-Roussel, B.; Gratien, A.; Michoud, V.; Cazaunau, M.; DeWitt, H. L.; Tapparo, A.; Monod, A.; Doussin, J.-F.

    2016-02-01

    The impact of cloud events on isoprene secondary organic aerosol (SOA) formation has been studied from an isoprene / NOx / light system in an atmospheric simulation chamber. It was shown that the presence of a liquid water cloud leads to a faster and higher SOA formation than under dry conditions. When a cloud is generated early in the photooxidation reaction, before any SOA formation has occurred, a fast SOA formation is observed with mass yields ranging from 0.002 to 0.004. These yields are 2 and 4 times higher than those observed under dry conditions. When the cloud is generated at a later photooxidation stage, after isoprene SOA is stabilized at its maximum mass concentration, a rapid increase (by a factor of 2 or higher) of the SOA mass concentration is observed. The SOA chemical composition is influenced by cloud generation: the additional SOA formed during cloud events is composed of both organics and nitrate containing species. This SOA formation can be linked to the dissolution of water soluble volatile organic compounds (VOCs) in the aqueous phase and to further aqueous phase reactions. Cloud-induced SOA formation is experimentally demonstrated in this study, thus highlighting the importance of aqueous multiphase systems in atmospheric SOA formation estimations.

  19. Hexagonal ice stability and growth in the presence of glyoxal and secondary organic aerosols.

    PubMed

    Daskalakis, Vangelis; Hadjicharalambous, Marios

    2014-09-01

    The presence of ice dominates the microphysics of formation of high altitude cirrus and polar stratospheric clouds, as well as the maturity of thunderstorms. We report on the hexagonal (1h) ice stability and growth in binary as well as multi-compound aerosols in atmospherically relevant conformations. The ubiquitous atmospheric trace gas glyoxal along with secondary organic aerosol (SOA) also in the presence of CO2 interacts with large ice 1h crystals of 1300-2000 water molecules. The crystals are subjected to phase transitions under superheating and supercooling conditions by Molecular Dynamics (MD) simulations. Density Functional Theory (DFT) based geometry optimization and vibrational frequency analysis are also employed for a smaller ice 1h cell of 12 water molecules. The interaction of the latter with each organic molecule reveals the extent of the mechanical stress exerted on the ordered ice structure. Full hydration of glyoxal promotes ice 1h stability and growth in wet aerosols, while partial hydration or full oxidation exerts a destabilizing effect on the ice 1h lattice. This behavior is associated with the ability of each organic phase to match the order of the ice 1h crystal. We propose that aqueous chemistry in wet aerosols may also have a strong effect on the microphysics of cloud formation. PMID:25033409

  20. Substantial secondary organic aerosol formation in a coniferous forest: observations of both day- and nighttime chemistry

    NASA Astrophysics Data System (ADS)

    Lee, Alex K. Y.; Abbatt, Jonathan P. D.; Leaitch, W. Richard; Li, Shao-Meng; Sjostedt, Steve J.; Wentzell, Jeremy J. B.; Liggio, John; Macdonald, Anne Marie

    2016-06-01

    Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region in Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas-particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 arises from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is likely less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22-33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol. Using f91 to evaluate BSOA formation pathways in this unpolluted, forested region, heterogeneous oxidation of BSOA-1 is a minor production pathway of BSOA-2.

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

    PubMed

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

    2010-04-13

    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 alpha-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 alpha-pinene products on size-selected DOP particles and by condensation of DOP on size-selected alpha-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 approximately 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

  2. 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.

  3. Molecular Corridor Based Approach for Description of Evolution of Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Li, Y., Sr.; Poeschl, U.; Shiraiwa, M.

    2015-12-01

    Organic aerosol is ubiquitous in the atmosphere and its major component is secondary organic aerosol (SOA). Formation and evolution of SOA is a complex process involving coupled chemical reactions and mass transport in the gas and particle phases (Shiraiwa et al., 2014). Current air quality models do not embody the full spectrum of reaction and transport processes, nor do they identify the dominant rate-limiting steps in SOA formation, resulting in the significant underprediction of observed SOA concentrations, which precludes reliable quantitative predictions of aerosols and their environmental impacts. Recently, it has been suggested that the SOA chemical evolution can be represented well by "molecular corridor" with a tight inverse correlation between molar mass and volatility of SOA oxidation products (Shiraiwa et al., 2014). Here we further analyzed the structure, molar mass and volatility of 31,000 unique organic compounds. These compounds include oxygenated organic compounds as well as nitrogen- and sulfur-containing organics such as amines, organonitrates, and organosulfates. Results show that most of those compounds fall into this two-dimensional (2-D) space, which is constrained by two boundary lines corresponding to the volatility of n -alkanes CnH2n+2 and sugar alcohols CnH2n+2On. A method to predict the volatility of nitrogen- and sulfur- containing compounds is developed based on those 31,000 organic compounds. It is shown that the volatility can be well predicted as a function of chemical composition numbers, providing a way to apply this 2-D space to organic compounds observed in real atmosphere. A comprehensive set of observation data from laboratory experiments, field campaigns and indoor measurements is mapped to the molecular corridor. This 2-D space can successfully grasp the properties of organic compounds formed in different atmospheric conditions. The molecular corridor represents a new framework in which chemical and physical properties as

  4. Modeling the role of alkanes, polycyclic aromatic hydrocarbons, and their oligomers in secondary organic aerosol formation.

    PubMed

    Pye, Havala O T; Pouliot, George A

    2012-06-01

    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 over the United States. Oxidation of alkanes is predicted to produce more aerosol than oxidation of PAHs driven by relatively higher alkane emissions. SOA from alkanes and PAHs, although small in magnitude, can be a substantial fraction of the SOA from anthropogenic hydrocarbons, particularly in winter, and could contribute more if emission inventories lack intermediate volatility alkanes (>C(13)) or if the vehicle fleet shifts toward diesel-powered vehicles. The SOA produced from oxidation of alkanes correlates well with ozone and odd oxygen in many locations, but the lower correlation of anthropogenic oligomers with odd oxygen indicates that models may need additional photochemically dependent pathways to low-volatility SOA. PMID:22568386

  5. Organic secondary ion mass spectrometry: signal enhancement by water vapor injection.

    PubMed

    Mouhib, Taoufiq; Delcorte, Arnaud; Poleunis, Claude; Bertrand, Patrick

    2010-12-01

    The enhancement of the static secondary ion mass spectrometry (SIMS) signals resulting from the injection, closely to the sample surface, of H(2)O vapor at relatively high-pressure, was investigated for a set of organic materials. While the ion signals are generally improved with increasing H(2)O pressure upon 12 keV Ga(+) bombardment, a specific enhancement of the protonated ion intensity is clearly demonstrated in each case. For instance, the presence of H(2)O vapor induces an enhancement by one order of magnitude of the [M + H](+) static SIMS intensity for the antioxidant Irgafos 168 and a ∼1.5-fold increase for polymers such as poly(vinyl pyrrolidone). PMID:20864353

  6. Computational design of metal-organic frameworks with paddlewheel-type secondary building units

    NASA Astrophysics Data System (ADS)

    Schwingenschlogl, Udo; Peskov, Maxim V.; Masghouni, Nejib

    We employ the TOPOS package to study 697 coordination polymers containing paddlewheel-type secondary building units. The underlying nets are analyzed and 3 novel nets are chosen as potential topologies for paddlewheel-type metal organic frameworks (MOFs). Dicarboxylate linkers are used to build basic structures for novel isoreticular MOF series, aiming at relatively compact structures with a low number of atoms per unit cell. The structures are optimized using density functional theory. Afterwards the Grand Canonical Monte Carlo approach is employed to generate adsorption isotherms for CO2, CO, and CH4 molecules. We utilize the universal forcefield for simulating the interaction between the molecules and hosting MOF. The diffusion behavior of the molecules inside the MOFs is analyzed by molecular dynamics simulations.

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

    PubMed Central

    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. PMID:23880782

  8. Reactive Uptake of Ammonia and Formation of Organic Nitrogen Species for Non-Liquid/Liquid Secondary Organic Material

    NASA Astrophysics Data System (ADS)

    Martin, S. T.; Li, Y.; Liu, P.

    2015-12-01

    Formation of ammonium and organic nitrogen (ON) species was studied for secondary organic material (SOM) of variable viscosity, ranging from non-liquid to liquid physical states. The SOM was produced as particles of 50 to 150 nm in diameter in aerosol form from six precursors, including three terpenoid and three aromatic species. The viscosity of the hygroscopic SOM was adjusted by exposure to relative humidity (RH) from <5% to >90% RH in steps of 10% at 293 ± 2 K. The aerosol was subsequently exposed to 5 ppm NH3 for mean reaction times of 30, 370, or 5230 s. Ammonium and ON were characterized by high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS). The ammonium-to-organic ratio of mass concentrations (MNH4/MOrg) in the particles increased monotonically from <5% RH to a limiting value at a threshold RH, implicating a switchover in the reaction kinetics from a system limited by diffusivity within the SOM for low RH to one limited by other factors, such as saturated uptake, at higher RH. Formation of ON was observed for aromatic-derived SOMs, but not significant for terpenoid-derived SOMs. For aromatic-derived SOMs, the ON-to-organic ratio of mass concentrations (MON/MOrg) was negligible for RH <20%, increased monotonically from 20% to 60% RH, and stayed constant for RH >60%. The threshold RH for the switchover from kinetically controlled regime to a non-kinetically-controlled one was thus different between formation of ammonium and ON. This difference suggests that water may play a role in the slow reactions of ON formation as a reactant or a catalyst, in addition to affecting the reactant diffusion as in the fast reaction of ammonium formation. The implication is that formation of ammonium salts and organic nitrogen species by certain SOMs should be treated separately in chemical transport models to reflect the different roles of water that may affect the phase state of the SOMs or may act as a reactant or a catalyst.

  9. Formation mechanism of the secondary building unit in a chromium terephthalate metal-organic framework

    SciTech Connect

    Cantu Cantu, David; McGrail, B. Peter; Glezakou, Vassiliki Alexandra

    2014-09-18

    Based on density functional theory calculations and simulation, a detailed mechanism is presented on the formation of the secondary building unit (SBU) of MIL-101, a chromium terephthalate metal-organic framework (MOF). SBU formation is key to MOF nucleation, the rate-limiting step in the formation process of many MOFs. A series of reactions that lead to the formation of the SBU of MIL-101 is proposed in this work. Initial rate-limiting reactions form the metal cluster with three chromium (III) atoms linked to a central bridging oxygen. Terephthalate linkers play a key role as chromium (III) atoms are joined to linker carboxylate groups prior to the placement of the central bridging oxygen. Multiple linker addition reactions, which follow in different paths due to structural isomers, are limited by the removal of water molecules in the first chromium coordination shell. The least energy path is identified were all linkers on one face of the metal center plane are added first. A simple kinetic model based on transition state theory shows the rate of secondary building unit formation similar to the rate metal-organic framework nucleation. The authors are thankful to Dr. R. Rousseau for a critical reading of the manuscript. This research would not have been possible without the support of the Office of Fossil Energy, U.S. Department of Energy. This research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and the PNNL Institutional Computing (PIC) program located at Pacific Northwest National Laboratory.

  10. Secondary organic aerosol formation from the ozonolysis of 2-carene and 3-carene

    NASA Astrophysics Data System (ADS)

    Mellouki, A.; Chen, H.; Bernard, F.; Cazaunau, M.; Grosselin, B.; Daele, V.; Chen, J.

    2013-12-01

    The atmospheric degradation of terpenes in the remote areas such as those with coniferous forests is known to lead to the formation and growth of atmospheric new particles. 2-carene and 3-carene have been reported to be present in number of such areas. Hence, their oxidation may represent an important source of secondary organic aerosols in some specific regions. 2-carene and 3-carene possess a structure of endocyclic double bonds which make them reactive toward ozone under atmospheric conditions. We have conducted a study on the reactions of ozone with 2-carene and 3-carene using a flow reactor dedicated to the investigation of secondary organic aerosol (SOA) formation. The reactor is equipped with an ozone generator and a movable injector which allows the reaction to occur within a short time range (typically 17 - 48 seconds). This enables us to investigate the initial steps of the SOA formation. In a first series of experiments, we have determined the rate constant for the reaction of ozone with 3-carene under pseudo-first-order conditions. The rate constant value measured was 3.8 x 10-17 molecule-1s-1, at 298 K, in agreement with the literatures and simulation chamber experiments. We have then investigated the SOA formation from the ozonolysis of 2-carene and 3-carene. By adjusting the residence time and initial concentration of carenes and ozone, number concentration of SOA have been measured for short reactions times and low concentrations of reactants. Nucleation thresholds of 2-carene and 3-carene were extracted from the plots of log N = f(Δ[Carenes]).

  11. Stable carbon isotope composition of secondary organic aerosol from β-pinene oxidation

    NASA Astrophysics Data System (ADS)

    Fisseha, Rebeka; Spahn, Holger; Wegener, Robert; Hohaus, Thorsten; Brasse, Gregor; Wissel, Holger; Tillmann, Ralf; Wahner, Andreas; Koppmann, Ralf; Kiendler-Scharr, Astrid

    2009-01-01

    A chamber study was carried out to investigate the stable carbon isotopic composition (δ13C) of secondary organic aerosol (SOA) formed from ozonolysis of β-pinene. β-Pinene (600 ppb) with a known δ13C value (-30.1‰) and 500 ppb ozone were injected into the chamber in the absence of light and the resulting SOA was collected on preheated quartz fiber filters. Furthermore, δ13C values of the gas-phase β-pinene and one of its oxidation products, nopinone, were measured using a gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS). β-Pinene was progressively enriched with the heavy carbon isotope due to the kinetic isotope effect (KIE). The KIE of the reaction of β-pinene with ozone was measured to be 1.0026 ? 2.6 ± 1.5‰). The δ13C value of total secondary organic aerosol was very similar to that of its precursor (average = -29.6 ± 0.2‰) independent of experiment time. Nopinone, one of the major oxidation products of β-pinene, was found in both the gas and aerosol phases. The gas-phase nopinone was heavier than the initial β-pinene by 1.3‰ but lighter than the corresponding aerosol-phase nopinone. On average, the gas-phase nopinone was lighter by 2.3‰ than the corresponding aerosol-phase nopinone. The second product found in the SOA was detected as acetone, but it desorbed from the filter at a higher temperature than nopinone, which indicates that it is a pyrolysis product. The acetone showed a much lower δ13C (-36.6‰) compared to the initial β-pinene δ13C.

  12. Formation of hydroxyl radicals from photolysis of secondary organic aerosol material

    NASA Astrophysics Data System (ADS)

    Badali, K. M.; Zhou, S.; Aljawhary, D.; Antiñolo, M.; Chen, W. J.; Lok, A.; Mungall, E.; Wong, J. P. S.; Zhao, R.; Abbatt, J. P. D.

    2015-07-01

    This paper demonstrates that OH radicals are formed by photolysis of secondary organic aerosol (SOA) material formed by terpene ozonolysis. The SOA is collected on filters, dissolved in water containing a radical trap (benzoic acid), and then exposed to ultraviolet light in a photochemical reactor. The OH formation rates, which are similar for both α-pinene and limonene SOA, are measured from the formation rate of p-hydroxybenzoic acid as measured using offline HPLC analysis. To evaluate whether the OH is formed by photolysis of H2O2 or organic hydroperoxides (ROOH), the peroxide content of the SOA was measured using the horseradish peroxidase-dichlorofluorescein (HRP-DCF) assay, which was calibrated using H2O2. The OH formation rates from SOA are 5 times faster than from the photolysis of H2O2 solutions whose concentrations correspond to the peroxide content of the SOA solutions, assuming that the HRP-DCF signal arises from H2O2 alone. The higher rates of OH formation from SOA are likely due to ROOH photolysis, but we cannot rule out a contribution from secondary processes as well. This result is substantiated by photolysis experiments conducted with t-butyl hydroperoxide and cumene hydroperoxide which produce over 3 times more OH than photolysis of equivalent concentrations of H2O2. Relative to the peroxide level in the SOA and assuming that the peroxides drive most of the ultraviolet absorption, the quantum yield for OH generation from α-pinene SOA is 0.8 ± 0.4. This is the first demonstration of an efficient photolytic source of OH in SOA, one that may affect both cloud water and aerosol chemistry.

  13. Why organisms age: Evolution of senescence under positive pleiotropy?

    PubMed

    Maklakov, Alexei A; Rowe, Locke; Friberg, Urban

    2015-07-01

    Two classic theories maintain that aging evolves either because of alleles whose deleterious effects are confined to late life or because of alleles with broad pleiotropic effects that increase early-life fitness at the expense of late-life fitness. However, empirical studies often reveal positive pleiotropy for fitness across age classes, and recent evidence suggests that selection on early-life fitness can decelerate aging and increase lifespan, thereby casting doubt on the current consensus. Here, we briefly review these data and promote the simple argument that aging can evolve under positive pleiotropy between early- and late-life fitness when the deleterious effect of mutations increases with age. We argue that this hypothesis makes testable predictions and is supported by existing evidence. PMID:25900580

  14. Modeling anthropogenically-controled secondary organic aerosols in a megacity: a simplified framework for global and climate models

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Jimenez, J. L.

    2011-04-01

    A simplified parameterization for secondary organic aerosol (SOA) formation in polluted air and biomass burning smoke is tested and optimized in this work, towards the goal of a computationally inexpensive method to calculate pollution and biomass burning SOA in global and climate models. A regional chemistry-transport model is used as the testbed for the parameterization, which is compared against observations from the Mexico City metropolitan area during the MILAGRO 2006 field experiment. The empirical parameterization is based on the observed proportionality of SOA concentrations to excess CO and photochemical age of the airmass. The approach consists in emitting an organic gas as lumped SOA precursor surrogate proportional to anthropogenic or biomass burning CO emissions according to the observed ratio between SOA and CO in aged air, and reacting this surrogate with OH into a single non-volatile species that condenses to form SOA. An emission factor of 0.08 g of the lumped SOA precursor per g of CO and a rate constant with OH of 1.25 × 10-11 cm3 molecule-1 s-1 reproduce the observed average SOA mass within 30% in the urban area and downwind. When a 2.5 times slower rate is used (5 × 10-12 cm3 molecule-1 s-1) the predicted SOA amount and temporal evolution is nearly identical to the results obtained with SOA formation from semi-volatile and intermediate volatility primary organic vapors according to the Robinson et al. (2007) formulation. Our simplified method has the advantage of being much less computationally expensive than Robinson-type methods, and can be used in regions where the emissions of SOA precursors are not yet available. As the aged pollution SOA/ΔCO ratios are rather consistent globally, this parameterization could be reasonably tested in and applied to other regions. The potential enhancement of biogenic SOA by anthropogenic pollution, which has been suggested to play a major role in global SOA formation, is also tested using two simple

  15. Modeling anthropogenically controlled secondary organic aerosols in a megacity: a simplified framework for global and climate models

    NASA Astrophysics Data System (ADS)

    Hodzic, A.; Jimenez, J. L.

    2011-10-01

    A simplified parameterization for secondary organic aerosol (SOA) formation in polluted air and biomass burning smoke is tested and optimized in this work, towards the goal of a computationally inexpensive method to calculate pollution and biomass burning SOA mass and hygroscopicity in global and climate models. A regional chemistry-transport model is used as the testbed for the parameterization, which is compared against observations from the Mexico City metropolitan area during the MILAGRO 2006 field experiment. The empirical parameterization is based on the observed proportionality of SOA concentrations to excess CO and photochemical age of the airmass. The approach consists in emitting an organic gas as lumped SOA precursor surrogate proportional to anthropogenic or biomass burning CO emissions according to the observed ratio between SOA and CO in aged air, and reacting this surrogate with OH into a single non-volatile species that condenses to form SOA. An emission factor of 0.08 g of the lumped SOA precursor per g of CO and a rate constant with OH of 1.25 × 10-11 cm3 molecule-1 s-1 reproduce the observed average SOA mass within 30 % in the urban area and downwind. When a 2.5 times slower rate is used (5 × 10-12 cm3 molecule-1 s-1) the predicted SOA amount and temporal evolution is nearly identical to the results obtained with SOA formation from semi-volatile and intermediate volatility primary organic vapors according to the Robinson et al. (2007) formulation. Our simplified method has the advantage of being much less computationally expensive than Robinson-type methods, and can be used in regions where the emissions of SOA precursors are not yet available. As the aged SOA/ΔCO ratios are rather consistent globally for anthropogenic pollution, this parameterization could be reasonably tested in and applied to other regions. The evolution of oxygen-to-carbon ratio was also empirically modeled and the predicted levels were found to be in reasonable agreement

  16. Stable carbon isotope ratios of ambient secondary organic aerosols in Toronto

    NASA Astrophysics Data System (ADS)

    Saccon, M.; Kornilova, A.; Huang, L.; Moukhtar, S.; Rudolph, J.

    2015-09-01

    A method to quantify concentrations and stable carbon isotope ratios of secondary organic aerosols has been applied to study atmospheric nitrophenols in Toronto, Canada. The sampling of five nitrophenols, all with substantial secondary formation from the photooxidation of aromatic volatile organic compounds (VOCs), was conducted in the gas phase and particulate matter (PM) together and in PM alone. Their concentrations in the atmosphere are in the low ng m-3 range and, consequently, a large volume of air (> 1000 m3) is needed to analyze samples for stable carbon isotope ratios, resulting in sampling periods of typically 24 h. While this extended sampling period increases the representativeness of average values, it at the same time reduces possibilities to identify meteorological conditions or atmospheric pollution levels determining nitrophenol concentrations and isotope ratios. Average measured carbon isotope ratios of the different nitrophenols are between -34 and -33 ‰, which is well within the range predicted by mass balance. However, the observed carbon isotope ratios cover a range of nearly 9 ‰ and approximately 20 % of the isotope ratios of the products have isotope ratios lower than predicted from the kinetic isotope effect of the first step of the reaction mechanism and the isotope ratio of the precursor. This can be explained by isotope fractionation during reaction steps following the initial reaction of the precursor VOCs with the OH radical. Limited evidence for local production of nitrophenols is observed since sampling was done in the Toronto area, an urban center with significant anthropogenic emission sources. Strong evidence for significant local formation of nitrophenols is only found for samples collected in summer. On average, the difference in carbon isotope ratios between nitrophenols in the particle phase and in the gas phase is insignificant, but for a limited number of observations in summer, a substantial difference is observed. This

  17. Partitioning phase preference for secondary organic aerosol in an urban atmosphere

    PubMed Central

    Chang, Wayne L.; Griffin, Robert J.; Dabdub, Donald

    2010-01-01

    Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular matter. The impact of particular matter on both human health and global climate has long been recognized. Despite its importance, there are still many unanswered questions regarding the formation and evolution of SOA in the atmosphere. This study uses a modeling approach to understand the preferred partitioning behavior of SOA species into aqueous or organic condensed phases. More specifically, this work uses statistical analyses of approximately 24,000 data values for each variable from a state of the art 3D airshed model. Spatial and temporal distributions of fractions of SOA residing in the aqueous phase (fAQ) in the South Coast Air Basin of California are presented. Typical values of fAQ within the basin near the surface range from 5 to 80%. Results show that the likelihood of large fAQ values is inversely proportional to the total SOA loading. Analysis of various meteorological parameters indicates that large fAQ values are predicted because modeled aqueous-phase SOA formation is less sensitive than that of organic-phase SOA to atmospheric conditions that are not conducive to SOA formation. There is a diurnal variation of fAQ near the surface: It tends to be larger during daytime hours than during nighttime hours. Results also indicate that the largest fAQ values are simulated in layers above ground level at night. In summary, one must consider SOA in both organic and aqueous phases for proper regional and global SOA budget estimation. PMID:20176970

  18. Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    Reactive halogen species (RHS), such as X·, X2 and HOX containing X = chlorine and/or bromine, are released by various sources like photo-activated sea-salt aerosol or from salt pans, and salt lakes. Despite many studies of RHS reactions, the potential of RHS reacting with secondary organic aerosol (SOA) and organic aerosol derived from biomass-burning (BBOA) has been neglected. Such reactions can constitute sources of gaseous organohalogen compounds or halogenated organic matter in the tropospheric boundary layer and can influence physicochemical properties of atmospheric aerosols. Model SOA from α-pinene, catechol, and guaiacol was used to study heterogeneous interactions with RHS. Particles were exposed to molecular chlorine and bromine in an aerosol smog-chamber in the presence of UV/VIS irradiation and to RHS, released from simulated natural halogen sources like salt pans. Subsequently, the aerosol was characterized in detail using a variety of physicochemical and spectroscopic methods. Fundamental features were correlated with heterogeneous halogenation, which results in new functional groups (FTIR spectroscopy), changes UV/VIS absorption, chemical composition (ultrahigh resolution mass spectroscopy (ICR-FT/MS)), or aerosol size distribution. However, the halogen release mechanisms were also found to be affected by the presence of organic aerosol. Those interaction processes, changing chemical and physical properties of the aerosol are likely to influence e.g. the ability of the aerosol to act as cloud condensation nuclei, its potential to adsorb other gases with low-volatility, or its contribution to radiative forcing and ultimately the Earth's radiation balance.

  19. 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.

  20. Strengthening Parenting Skills: School Age. Secondary Learning Guide 2. Project Connect. Linking Self-Family-Work.

    ERIC Educational Resources Information Center

    Emily Hall Tremaine Foundation, Inc., Hartford, CT.

    This competency-based secondary learning guide on strengthening parenting skills is part of a series that are adaptations of guides developed for adult consumer and homemaking education programs. The guides provide students with experiences that help them learn to do the following: make decisions; use creative approaches to solve problems;…

  1. Living in a Global Age. A Simulation Activity for Upper Elementary and Secondary Level Students.

    ERIC Educational Resources Information Center

    Stanford Univ., CA. Stanford Program on International and Cross Cultural Education.

    Designed to introduce concepts in international trade and global economics to upper elementary and secondary level students, this simulation activity engages students in the group task of assembling flashlights. A variety of topics can be explored, such as energy shortages, international crises, relationships between rich and poor nations, foreign…

  2. 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

  3. Secondary Organic Aerosol Formation from m-Xylene in the Absence of NOx

    SciTech Connect

    Song, Chen; Na, Kwangsam; Warren, Bethany; Malloy, Quentin; Cocker, David R.

    2007-11-01

    Formation of secondary organic aerosol (SOA) from m-xylene photoxidation in the absence of NOx was investigated in a series of smog chamber experiments. Experiments were performed in dry air and in the absence of seed aerosol with H2O2 photolysis providing a stable hydroxyl radical (OH radical) source. SOA formation from this study is exceptionally higher than experiments with existence of NOx. The experiments with elevated HO2 levels indicate that organic hydroperoxide compounds should contribute to SOA formation. Nitrogen oxide (NO) is shown to reduce aerosol formation; the constant aerosol formation rate obtained before addition of NO and after consumption of NO strongly suggests that aerosol formation is mainly through reactions with OH and HO2 radicals. In addition, a density of 1.40 ± 0.1 g cm-3 for the SOA from the photooxidation of m-xylene in the absence of NOx has been measured, which is significantly higher than the currently used unit density.

  4. Chemical Reactivity and Liquid/Nonliquid States of Secondary Organic Material.

    PubMed

    Li, Yong Jie; Liu, Pengfei; Gong, Zhaoheng; Wang, Yan; Bateman, Adam P; Bergoend, Clara; Bertram, Allan K; Martin, Scot T

    2015-11-17

    The reactivity of secondary organic material (SOM) of variable viscosity, ranging from nonliquid to liquid physical states, was studied. The SOM, produced in aerosol form from terpenoid and aromatic precursor species, was reacted with ammonia at variable relative humidity (RH). The ammonium-to-organic mass ratio (MNH4+/MOrg) increased monotonically from <5% RH to a limiting value at a threshold RH, implicating a transition from particle reactivity limited by diffusion at low RH to one limited by other factors at higher RH. For the studied size distributions and reaction times, the transition corresponded to a diffusivity above 10-17.5 ± 0.5 m2 s-1. The threshold RH values for the transition were <5% RH for isoprene-derived SOM, 35-45% RH for SOM derived from α-pinene, toluene, m-xylene, and 1,3,5-trimethylbenzene, and >90% for β-caryophyllene-derived SOM. The transition RH for reactivity differed in all cases from the transition RH of a nonliquid to a liquid state. For instance, for α-pinene-derived SOM the transition for chemical reactivity of 35-45% RH can be compared to the nonliquid to liquid transition of 65-90% RH. These differences imply that chemical transport models of atmospheric chemistry should not use the SOM liquid to nonliquid phase transition as one-to-one surrogates of SOM reactivity. PMID:26465059

  5. Heating-Induced Evaporation of Nine Different Secondary Organic Aerosol Types.

    PubMed

    Kolesar, Katheryn R; Li, Ziyue; Wilson, Kevin R; Cappa, Christopher D

    2015-10-20

    The volatility of the compounds comprising organic aerosol (OA) determines their distribution between the gas and particle phases. However, there is a disconnect between volatility distributions as typically derived from secondary OA (SOA) growth experiments and the effective particle volatility as probed in evaporation experiments. Specifically, the evaporation experiments indicate an overall much less volatile SOA. This raises questions regarding the use of traditional volatility distributions in the simulation and prediction of atmospheric SOA concentrations. Here, we present results from measurements of thermally induced evaporation of SOA for nine different SOA types (i.e., distinct volatile organic compound and oxidant pairs) encompassing both anthropogenic and biogenic compounds and O3 and OH to examine the extent to which the low effective volatility of SOA is a general phenomenon or specific to a subset of SOA types. The observed extents of evaporation with temperature were similar for all the SOA types and indicative of a low effective volatility. Furthermore, minimal variations in the composition of all the SOA types upon heating-induced evaporation were observed. These results suggest that oligomer decomposition likely plays a major role in controlling SOA evaporation, and since the SOA formation time scale in these measurements was less than a minute, the oligomer-forming reactions must be similarly rapid. Overall, these results emphasize the importance of accounting for the role of condensed phase reactions in altering the composition of SOA when assessing particle volatility. PMID:26393817

  6. CollagenVI-Cre mice: A new tool to target stromal cells in secondary lymphoid organs.

    PubMed

    Prados, Alejandro; Kollias, George; Koliaraki, Vasiliki

    2016-01-01

    Stromal cells in secondary lymphoid organs (SLOs) are non-hematopoietic cells involved in the regulation of adaptive immune responses. Three major stromal populations have been identified in adult SLOs: fibroblastic reticular cells (FRCs), follicular dendritic cells (FDCs) and marginal reticular cells (MRCs). The properties of these individual populations are not clearly defined, mainly due to the lack of appropriate genetic tools, especially for MRCs. Here, we analyzed stromal cell targeting in SLOs from a transgenic mouse strain that expresses Cre recombinase under the CollagenVI promoter, using lineage tracing approaches. We show that these mice target specifically MRCs and FDCs, but not FRCs in Peyer's patches and isolated lymphoid follicles in the intestine. In contrast, stromal cells in lymph nodes and the spleen do not express the transgene, which renders ColVI-cre mice ideal for the specific targeting of stromal cells in the gut-associated lymphoid tissue (GALT). This funding further supports the hypothesis of organ-specific stromal precursors in SLOs. Interestingly, in all tissues analyzed, there was also high specificity for perivascular cells, which have been proposed to act as FDC precursors. Taken together, ColVI-Cre mice are a useful new tool for the dissection of MRC- and FDC-specific functions and plasticity in the GALT. PMID:27604178

  7. Optical properties of secondary organic aerosols generated by photooxidation of aromatic hydrocarbons

    PubMed Central

    Li, Kun; Wang, Weigang; Ge, Maofa; Li, Jiangjun; Wang, Dong

    2014-01-01

    The refractive index (RI) is the fundamental characteristic that affects the optical properties of aerosols, which could be some of the most important factors influencing direct radiative forcing. The secondary organic aerosols (SOAs) generated by the photooxidation of benzene, toluene, ethylbenzene and m-xylene (BTEX) under low-NOx and high-NOx conditions are explored in this study. The particles generated in our experiments are considered to be spherical, based on atomic force microscopy (AFM) images, and nonabsorbent at a wavelength of 532 nm, as determined by ultraviolet-visible light (UV-Vis) spectroscopy. The retrieved RIs at 532 nm for the SOAs range from 1.38–1.59, depending on several factors, such as different precursors and NOx levels. The RIs of the SOAs are altered differently as the NOx concentration increases as follows: the RIs of the SOAs derived from benzene and toluene increase, whereas those of the SOAs derived from ethylbenzene and m-xylene decrease. Finally, by comparing the experimental data with the model values, we demonstrate that the models likely overestimate the RI values of the SOA particles to a certain extent, which in turn overestimates the global direct radiative forcing of the organic particles. PMID:24815734

  8. Critical Care for Multiple Organ Failure Secondary to Ebola Virus Disease in the United States

    PubMed Central

    Sueblinvong, Viranuj; Johnson, Daniel W.; Weinstein, Gary L.; Connor, Michael J.; Crozier, Ian; Liddell, Allison M.; Franch, Harold A.; Wall, Bruce R.; Kalil, Andre C.; Feldman, Mark; Lisco, Steven J.; Sevransky, Jonathan E.

    2016-01-01

    Objective This report describes three patients with Ebola virus disease who were treated in the United States and developed for severe critical illness and multiple organ failure secondary to Ebola virus infection. The patients received mechanical ventilation, renal replacement therapy, invasive monitoring, vasopressor support, and investigational therapies for Ebola virus disease. Data Sources Patient medical records from three tertiary care centers (Emory University Hospital, University of Nebraska Medical Center, and Texas Health Presbyterian Dallas Hospital). Study Selection Not applicable. Data Extraction Not applicable. Data Synthesis Not applicable. Conclusion In the severe form, patients with Ebola virus disease may require life-sustaining therapy, including mechanical ventilation and renal replacement therapy. In conjunction with other reported cases, this series suggests that respiratory and renal failure may occur in severe Ebola virus disease, especially in patients burdened with high viral loads. Ebola virus disease complicated by multiple organ failure can be survivable with the application of advanced life support measures. This collective, multicenter experience is presented with the hope that it may inform future treatment of patients with Ebola virus disease requiring critical care treatment. PMID:26196353

  9. Effects of phase states on reactions of secondary organic materials with chloride

    NASA Astrophysics Data System (ADS)

    Wang, B.; Laskin, A.; OBrien, R. E.; Kelly, S. T.; Shilling, J. E.; Moffet, R.; Gilles, M. K.

    2014-12-01

    Secondary organic materials (SOM) in atmospheric aerosols are often mixed with inorganic components. Condensed-phase SOM can exist in a liquid, semi-solid, or solid state at different temperatures and RH. We investigated the effects of phase states of SOM on the reactions of SOM from ozonolysis of limonene (LSOM) and α-pinene (PSOM) with NaCl using a set of complementary micro-spectroscopic analyses. SOM can react with NaCl and result in chloride depletion in the condensed phase, release of gaseous HCl, and formation of organic salts. The reactions driven by the high volatility of HCl are attributed to acid displacement by SOM acidic components. Similar reactions can take place in SOM/NaNO3 particles. Glass transition temperatures and viscosity of PSOM were estimated. The results show that the reaction depends on SOM composition, phase state and viscosity, mixing state, and reaction time. The release and potential recycling of HCl and HNO3 from reacted aerosol particles may have important implications for atmospheric chemistry. This reaction can modify particle physicochemical properties, such as the ability to form clouds, and thus may have important atmospheric implications.

  10. 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.

  11. CollagenVI-Cre mice: A new tool to target stromal cells in secondary lymphoid organs

    PubMed Central

    Prados, Alejandro; Kollias, George; Koliaraki, Vasiliki

    2016-01-01

    Stromal cells in secondary lymphoid organs (SLOs) are non-hematopoietic cells involved in the regulation of adaptive immune responses. Three major stromal populations have been identified in adult SLOs: fibroblastic reticular cells (FRCs), follicular dendritic cells (FDCs) and marginal reticular cells (MRCs). The properties of these individual populations are not clearly defined, mainly due to the lack of appropriate genetic tools, especially for MRCs. Here, we analyzed stromal cell targeting in SLOs from a transgenic mouse strain that expresses Cre recombinase under the CollagenVI promoter, using lineage tracing approaches. We show that these mice target specifically MRCs and FDCs, but not FRCs in Peyer’s patches and isolated lymphoid follicles in the intestine. In contrast, stromal cells in lymph nodes and the spleen do not express the transgene, which renders ColVI-cre mice ideal for the specific targeting of stromal cells in the gut-associated lymphoid tissue (GALT). This funding further supports the hypothesis of organ-specific stromal precursors in SLOs. Interestingly, in all tissues analyzed, there was also high specificity for perivascular cells, which have been proposed to act as FDC precursors. Taken together, ColVI-Cre mice are a useful new tool for the dissection of MRC- and FDC-specific functions and plasticity in the GALT. PMID:27604178

  12. 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.

  13. 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.

  14. Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

    NASA Astrophysics Data System (ADS)

    Waxman, E.; Slowik, J.; Kampf, C.; Timkovsky, J.; Noziere, B.; Praplan, A.; Pffafenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A.; Baltensperger, U.; Volkamer, R.

    2012-04-01

    Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

  15. Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation

    NASA Astrophysics Data System (ADS)

    Waxman, E.; Slowik, J. G.; Kampf, C. J.; Timkovsky, J.; Noziere, B.; Praplan, A. P.; Pfaffenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A. S.; Baltensperger, U.; Volkamer, R.

    2011-12-01

    Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

  16. Soft ionization chemical analysis of secondary organic aerosol from green leaf volatiles emitted by turf grass.

    PubMed

    Jain, Shashank; Zahardis, James; Petrucci, Giuseppe A

    2014-05-01

    Globally, biogenic volatile organic compound (BVOC) emissions contribute 90% of the overall VOC emissions. Green leaf volatiles (GLVs) are an important component of plant-derived BVOCs, including cis-3-hexenylacetate (CHA) and cis-3-hexen-1-ol (HXL), which are emitted by cut grass. In this study we describe secondary organic aerosol (SOA) formation from the ozonolysis of dominant GLVs, their mixtures and grass clippings. Near-infrared laser desorption/ionization aerosol mass spectrometry (NIR-LDI-AMS) was used for chemical analysis of the aerosol. The chemical profile of SOA generated from grass clippings was correlated with that from chemical standards of CHA and HXL. We found that SOA derived from HXL most closely approximated SOA from turf grass, in spite of the approximately 5× lower emission rate of HXL as compared to CHA. Ozonolysis of HXL results in formation of low volatility, higher molecular weight compounds, such as oligomers, and formation of ester-type linkages. This is in contrast to CHA, where the hydroperoxide channel is the dominant oxidation pathway, as oligomer formation is inhibited by the acetate functionality. PMID:24666343

  17. Direct observation of aqueous secondary organic aerosol from biomass-burning emissions.

    PubMed

    Gilardoni, Stefania; Massoli, Paola; Paglione, Marco; Giulianelli, Lara; Carbone, Claudio; Rinaldi, Matteo; Decesari, Stefano; Sandrini, Silvia; Costabile, Francesca; Gobbi, Gian Paolo; Pietrogrande, Maria Chiara; Visentin, Marco; Scotto, Fabiana; Fuzzi, Sandro; Facchini, Maria Cristina

    2016-09-01

    The mechanisms leading to the formation of secondary organic aerosol (SOA) are an important subject of ongoing research for both air quality and climate. Recent laboratory experiments suggest that reactions taking place in the atmospheric liquid phase represent a potentially significant source of SOA mass. Here, we report direct ambient observations of SOA mass formation from processing of biomass-burning emissions in the aqueous phase. Aqueous SOA (aqSOA) formation is observed both in fog water and in wet aerosol. The aqSOA from biomass burning contributes to the "brown" carbon (BrC) budget and exhibits light absorption wavelength dependence close to the upper bound of the values observed in laboratory experiments for fresh and processed biomass-burning emissions. We estimate that the aqSOA from residential wood combustion can account for up to 0.1-0.5 Tg of organic aerosol (OA) per y in Europe, equivalent to 4-20% of the total OA emissions. Our findings highlight the importance of aqSOA from anthropogenic emissions on air quality and climate. PMID:27551086

  18. 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

  19. Secondary organic aerosol 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, Th. F.

    2015-01-01

    Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compound (BVOC) 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 (Simulation of Atmospheric PHotochemistry In a large Reaction) chamber in Jülich, Germany, at low NOx (0.01 ~ 1 ppbV) and low ozone (O3) concentration (< 20 ppbV). OH concentration and total OH reactivity (kOH) were measured directly, and through this the overall reaction rate of total organics with OH in each reaction system was quantified. Multi-generation reaction process, particle growth, new particle formation (NPF), 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 rate of OH with total 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 play an important role 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

  20. SOURCES OF ORGANIC AEROSOL: SEMIVOLATILE EMISSIONS AND PHOTOCHEMICAL AGING

    EPA Science Inventory

    The proposed research integrates emissions testing, smog chamber experiments, and regional chemical transport models (CTMs) to investigate the sources of organic aerosol in urban and regional environments.

  1. 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.

  2. [Skeleton or mummy: practices and structures for secondary burial in southern Italy in modern and contemporary age].

    PubMed

    Fornaciari, Antonio

    2013-01-01

    The ancient concepts of death as duration and the practices of secondary burial,first analysed by Robert Hertz, still survive in many areas of southern Italy. According to these beliefs death was perceived not as a sudden event, but as a long-lasting process, during which the deceased person had to go through a transitory phase, passing from one state of existence to another. Recent archeological research documents the persistence of secondary burial rites in Southern Italy during the Modern Age. A survey conducted in the province of Messina in Eastern Sicily has identified two surviving architectural structures appointed for the treatment of the bodies: the 'sitting colatoio' aimed at favoring the skeletonisation and the 'horizontal colatoio' used to obtain mummification by dehydration. Both these structures controlled the corpse's decay and transformed the body in a stable and durable simulacra of the dead. PMID:25807706

  3. Distinct kinetic responses in vivo of cortical thymocytes of ageing mice to primary as compared to secondary peripheral antigenic stimulation.

    PubMed Central

    Luscieti, P; Graff, P; Luethi, M; Cottier, H; Hess, M W; Kraft, R; Stoner, R D

    1983-01-01

    We have studied cellular kinetic changes in the thymic cortex of ageing mice as a function of time after primary and secondary stimulation with aluminum phosphate adsorbed tetanus toxoid via the hind leg footpads. Absolute numbers of DNA synthesizing cortical thymocytes per cross-section of the thymus were computed from combined data obtained by planimetry, counts of cell density (cellularity) and assessment of the labelling index, 1 h after injection of (methyl-3H)-thymidine. The proliferative activity of these cells in the outer fourth of the thymic cortex reached a peak exceeding significantly control values by 45% 14 days after primary, but not secondary, peripheral antigenic stimulation. We conclude that the cortical thymocyte population responded in a distinct manner to the first immunization as opposed to the booster injection of the same antigen. PMID:6602681

  4. Estimating the direct and indirect effects of secondary organic aerosols using ECHAM5-HAM

    NASA Astrophysics Data System (ADS)

    O'Donnell, D.; Tsigaridis, K.; Feichter, J.

    2011-08-01

    Secondary organic aerosol (SOA) has been introduced into the global climate-aerosol model ECHAM5/HAM. The SOA module handles aerosols originating from both biogenic and anthropogenic sources. The model simulates the emission of precursor gases, their chemical conversion into condensable gases, the partitioning of semi-volatile condenable species into the gas and aerosol phases. As ECHAM5/HAM is a size-resolved model, a new method that permits the calculation of partitioning of semi-volatile species between different size classes is introduced. We compare results of modelled organic aerosol concentrations against measurements from extensive measurement networks in Europe and the United States, running the model with and without SOA. We also compare modelled aerosol optical depth against measurements from the AERONET network of grond stations. We find that SOA improves agreement between model and measurements in both organic aerosol mass and aerosol optical depth, but does not fully correct the low bias that is present in the model for both of these quantities. Although many models now include SOA, any overall estimate of the direct and indirect effects of these aerosols is still lacking. This paper makes a first step in that direction. The model is applied to estimate the direct and indirect effects of SOA under simulated year 2000 conditions. The modelled SOA spatial distribution indicates that SOA is likely to be an important source of free and upper tropospheric aerosol. We find a negative shortwave (SW) forcing from the direct effect, amounting to -0.31 Wm-2 on the global annual mean. In contrast, the model indicates a positive indirect effect of SOA of +0.23 Wm-2, arising from the enlargement of particles due to condensation of SOA, together with an enhanced coagulation sink of small particles. In the longwave, model results are a direct effect of +0.02 Wm-2 and an indirect effect of -0.03 Wm-2.

  5. Secondary Organic Aerosol (SOA) production from the Aqueous Reactions of Phenols and Triplet Aromatic Carbonyls

    NASA Astrophysics Data System (ADS)

    Smith, J.; Sun, Y.; Lu, Y.; Zhang, Q.; Anastasio, C.

    2010-12-01

    The phenolic compounds guaiacol, syringol and phenol have recently been shown to produce secondary organic aerosol (SOA) at high yields in the aqueous phase upon exposure to simulated sunlight and hydroxyl radical. These phenols are significant products from wood combustion that can readily enter atmospheric waters, such as aqueous aerosol particles and cloud/fog droplets. Once in the aqueous phase, phenols can react with the triplet excited states of non-phenolic aromatic carbonyls (NPCs), particle-bound organics that are also emitted from wood combustion. In this study, we examined the aqueous-phase production of SOA from the reaction of phenolic compounds with triplet excited state organics. These aqueous phase reactions were tested by illuminating solutions containing a phenolic compound and NPC under simulated sunlight at various concentrations and pH values. The phenolic compound is consumed during these reactions, following a first-order decay that varies with phenol concentration, phenol identity, and pH. The non-volatile product mass formed in our illuminated solutions was determined gravimetrically and by analysis with High Resolution Time of Flight Aerosol Mass Spectrometry (HR-AMS). The SOA mass yield was determined as the mass of non-volatile product formed per mass of phenolic consumed during illumination. We also used HR-AMS to analyze for elemental composition, carbon oxidation state, and oligomers in the SOA produced. Our results to date indicate that phenols can be rapidly oxidized by triplet excited states under environmentally relevant conditions and that the accompanying SOA mass yields are very high.

  6. 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.

  7. Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity.

    PubMed

    Renbaum-Wolff, Lindsay; Grayson, James W; Bateman, Adam P; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J; Shilling, John E; Martin, Scot T; Bertram, Allan K

    2013-05-14

    Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a "bead-mobility" technique and a "poke-flow" technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by α-pinene ozonolysis is quantified for 20- to 50-μm particles at 293-295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ≤30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ≤ 30%; (ii) at ≤30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate. PMID:23620520

  8. CCN activation and hygroscopic growth measurements of secondary organic aerosols from tree emissions

    NASA Astrophysics Data System (ADS)

    Buchholz, Angela; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Spindler, Christian; Tillmann, Ralf; Kleist, Einhard; Wildt, Juergen

    2010-05-01

    Plant emitted volatile organic compounds (VOCs) are a major precursor of secondary organic aerosols (SOA), an important constituent of atmospheric aerosols. We used the Juelich Plant Atmosphere Chamber (JPAC) at the Research Center Juelich to investigate the microphysical properties of aerosols. SOA particles were produced from the ozonolysis and reaction of OH radicals with the complex VOC mixture emitted from trees typical for the boreal forest. Hygroscopic growth factors (GF) were determined with a humidity tandem differential mobility analyzer (HTDMA) for different particle sizes at RH = 2 - 97%. Cloud condensation nuclei (CCN) activation was measured with a continuous flow CCN counter (DMT). Additionally, the chemical composition, size distribution and number concentration of the particles were measured. The gas phase was monitored with GC-MS and PTR-MS. Changing the emission pattern of the trees changed the measured GF and the diameter of the dry particles that were activated (Dcrit). However, below 80% RH the GF changes are within the range of the measurement error. The GF (RH = 95%) are between 1.11 and 1.19 and the Dcrit(SS = 0.4%) in a range of 93 - 100nm. Koehler theory was applied to achieve closure between CCN activation and GF measurements. The κ parameter according to Petters and Kreidenweis (2007) was calculated for all SS (κ(CCN)) and RH (κ(GF)). The κ(GF) decrease with increasing RH but levels off at RH > 95%. Assuming the surface tension of pure water, κ(GF, RH>95%) would be by a factor of 2 lower than κ(CCN). Closure between the HTDMA and CCN measurement requires the use of either a lower surface tension or a limited solubility of the organic material. Reference: Petters, M. D. and Kreidenweis, S. M. (2007). Atmos. Chem. Phys., 7, 1961-1971.

  9. Reactivity of liquid and semisolid secondary organic carbon with chloride and nitrate in atmospheric aerosols

    SciTech Connect

    Wang, Bingbing; O'Brien, Rachel E.; Kelly, Stephen T.; Shilling, John E.; Moffet, Ryan C.; Gilles, Mary K.; Laskin, Alexander

    2015-05-14

    Constituents of secondary organic carbon (SOC) in atmospheric aerosols are often mixed with inorganic components and compose a significant mass fraction of fine particulate matter in the atmosphere. Interactions between SOC and other condensed-phase species are not well understood. Here, we investigate the reactions of liquid-like and semi-solid SOC from ozonolysis of limonene (LSOC) and α-pinene (PSOC) with NaCl using a set of complementary micro-spectroscopic analyses. These reactions result in chloride depletion in the condensed phase, release of gaseous HCl, and formation of organic salts. The reactions attributed to acid displacement by SOC acidic components are driven by the high volatility of HCl. Similar reactions can take place in SOC/NaNO₃ particles. The results show that an increase in SOC mass fraction in the internally mixed SOC/NaCl particles leads to higher chloride depletion. Glass transition temperatures and viscosity of PSOC were estimated for atmospherically relevant conditions. Data show that the reaction extent depends on SOC composition, particle phase state and viscosity, mixing state, temperature, relative humidity (RH), and reaction time. LSOC shows slightly higher potential to deplete chloride than PSOC. Higher particle viscosity at low temperatures and RH can hinder these acid displacement reactions. Formation of organic salts from these overlooked reactions can alter particle physiochemical properties and may affect their reactivity and ability to act as cloud condensation and ice nuclei. The release and potential recycling of HCl and HNO₃ from reacted aerosol particles may have important implications for atmospheric chemistry.

  10. Carbonaceous PM(2.5) and secondary organic aerosol across the Veneto region (NE Italy).

    PubMed

    Khan, Md Badiuzzaman; Masiol, Mauro; Formenton, Gianni; Di Gilio, Alessia; de Gennaro, Gianluigi; Agostinelli, Claudio; Pavoni, Bruno

    2016-01-15

    Organic and elemental carbon (OC-EC) were measured in 360 PM2.5 samples collected from April 2012 to February 2013 at six provinces in the Veneto region, to determine the factors affecting the carbonaceous aerosol variations. The 60 daily samples have been collected simultaneously in all sites during 10 consecutive days for 6 months (April, June, August, October, December and February). OC ranged from 0.98 to 22.34 μg/m(3), while the mean value was 5.5 μg/m(3), contributing 79% of total carbon. EC concentrations fluctuated from 0.19 to 11.90 μg/m(3) with an annual mean value of 1.31 μg/m(3) (19% of the total carbon). The monthly OC concentration gradually increased from April to December. The EC did not vary in accordance with OC. However the highest values for both parameters were recorded in the cold period. The mean OC/EC ratio is 4.54, which is higher than the values observed in most of the other European cities. The secondary organic carbon (SOC) contributed for 69% of the total OC and this was confirmed by both the approaches OC/EC minimum ratio and regression. The results show that OC, EC and SOC exhibited higher concentration during winter months in all measurement sites, suggesting that the stable atmosphere and lower mixing play important role for the accumulation of air pollutant and hasten the condensation or adsorption of volatile organic compounds over the Veneto region. Significant meteorological factors controlling OC and EC were investigated by fitting linear models and using a robust procedure based on weighted likelihood, suggesting that low wind speed and temperature favour accumulation of emissions from local sources. Conditional probability function and conditional bivariate probability function plots indicate that both biomass burning and vehicular traffic are probably the main local sources for carbonaceous particulate matter emissions in two selected cities. PMID:26519578

  11. Aqueous photooxidation of ambient Po Valley Italy air samples: Insights into secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Kirkland, J. R.; Lim, Y. B.; Sullivan, A. P.; Decesari, S.; Facchini, C.; Collett, J. L.; Keutsch, F. N.; Turpin, B. J.

    2012-12-01

    In this work, we conducted aqueous photooxidation experiments with ambient samples in order to develop insights concerning the formation of secondary organic aerosol through gas followed by aqueous chemistry (SOAaq). Water-soluble organics (e.g., glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone) are formed through gas phase oxidation of alkene and aromatic emissions of anthropogenic and biogenic origin. Their further oxidation in clouds, fogs and wet aerosols can form lower volatility products (e.g., oligomers, organic acids) that remain in the particle phase after water evaporation, thus producing SOA. The aqueous OH radical oxidation of several individual potentially important precursors has been studied in the laboratory. In this work, we used a mist-chamber apparatus to collect atmospheric mixtures of water-soluble gases from the ambient air at San Pietro Capofiume, Italy during the PEGASOS field campaign. We measured the concentration dynamics after addition of OH radicals, in order to develop new insights regarding formation of SOA through aqueous chemistry. Specifically, batch aqueous reactions were conducted with 33 ml mist-chamber samples (TOC ~ 50-100μM) and OH radicals (~10-12M) in a new low-volume aqueous reaction vessel. OH radicals were formed in-situ, continuously by H2O2 photolysis. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS +/-), and ESI-MS with IC pre-separation (IC/ESI-MS-). Reproducible formation of pyruvate and oxalate were observed both by IC and ESI-MS. These compounds are known to form from aldehyde oxidation in the aqueous phase. New insights regarding the aqueous chemistry of these "more atmospherically-realistic" experiments will be discussed.

  12. Quantifying the ionic reaction channels in the Secondary Organic Aerosol formation from glyoxal

    NASA Astrophysics Data System (ADS)

    Maxut, Aurelia; Nozière, Barbara; Rossignol, Stéphanie; George, Christian; Waxman, Eleanor Marie; Laskin, Alexander; Slowik, Jay; Dommen, Josef; Prévôt, André; Baltensperger, Urs; Volkamer, Rainer

    2014-05-01

    Glyoxal, a common organic gas in the atmosphere, has been identified in recent years as an important Secondary Organic Aerosol (SOA) precursor (Volkamer et al., 2007). But, unlike with other precursors, the SOA is largely produced by particle-phase reactions (Volkamer et al., 2009) and equilibria (Kampf et al. 2013) that are still not entirely characterized. Since 2009 series of smog chamber experiments have been performed within the Eurochamp program at the Paul Scherrer Institute, Switzerland, to investigate SOA formation from glyoxal. In these experiments, glyoxal was produced by the gas-phase oxidation of acetylene in the presence of seeds, the seed composition and other conditions being varied. The 2011 campaign resulted in the identification of salting processes controlling the glyoxal partitioning in the seeds (Kampf et al. 2013). This presentation will report results of the 2013 campaign focusing on the identification of the various reactions (ionic or photo-induced) contributing to the SOA mass. In particular, the contribution of the ionic reactions, i.e. mediated by NH4+, were investigated by quantifying the formation of imidazoles (imidazole, imidazole-2-carboxaldehyde, 2,2'-biimidazole) from the small condensation channel of glyoxal with ammonia. For this, the SOA produced were collected on quartz filters and analyzed by Orbitrap LC/MS (Q-Exactive Thermo Fisher). The formation of other products such as organic acids was also investigated to determine potential competing reactions. Time-resolved MOUDI sampling coupled with nano-DESY/ESI-MS/MS analysis was also used to identify nitrogen- and sulphur-containing products from all the reactions. The results obtained for a range of conditions will be presented and compared with recent mechanistic information on the ionic reaction channels (Nozière et al., in preparation, 2013). The implementation of all this new information into a glyoxal-SOA model will be discussed.

  13. Secondary Organic Aerosol (SOA) Formation From the NO3 Radical Oxidation of Alpha- pinene

    NASA Astrophysics Data System (ADS)

    Perraud, V.; Yu, Y.; Bruns, E.; Ezell, M. J.; Johnson, S. N.; Alexander, M.; Zelenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

    2008-12-01

    Terpenes such as alpha-pinene, emitted in large quantities from vegetation into the troposphere, are well known to react with O3, OH and NO3 radicals leading to the formation of secondary organic aerosol, SOA. While particle formation and growth from the NO3 reaction with alpha-pinene have been reported by a number of groups, as have the gas phase products of this reaction, little is known about the chemical composition of the particles. We report studies of the composition of particles formed in the NO3 - alpha- pinene reaction using two reactors, a flow tube and a static chamber. Nitrate radicals were generated in the flow tube by the reaction of NO2 with O3 and in the static chamber by the thermal decomposition of N2O5. Particle formation and growth was monitored using SMPS and APS. A variety of analytical techniques were applied to measure the chemical composition, including FTIR of particles collected on ZnSe impactor discs, and GC-MS, ESI-MS, APCI-MS, HPLC-MS and HPLC-UV of samples collected on quartz fiber filters. In addition, particle mass spectrometer techniques including AMS and SPLAT provided real-time analysis. A number of organic nitrates were observed in the particles, along with carbonyl compounds and organic acids. Gas phase products measured using DNPH coated-cartridges included pinonaldehyde, formaldehyde, acetaldehyde and acetone. Results of studies in which concentrations of the reactants were varied will be presented and possible mechanisms and the atmospheric implications will be discussed.

  14. Viscosity of α-pinene secondary organic material and implications for particle growth and reactivity

    PubMed Central

    Renbaum-Wolff, Lindsay; Grayson, James W.; Bateman, Adam P.; Kuwata, Mikinori; Sellier, Mathieu; Murray, Benjamin J.; Shilling, John E.; Martin, Scot T.; Bertram, Allan K.

    2013-01-01

    Particles composed of secondary organic material (SOM) are abundant in the lower troposphere. The viscosity of these particles is a fundamental property that is presently poorly quantified yet required for accurate modeling of their formation, growth, evaporation, and environmental impacts. Using two unique techniques, namely a “bead-mobility” technique and a “poke-flow” technique, in conjunction with simulations of fluid flow, the viscosity of the water-soluble component of SOM produced by α-pinene ozonolysis is quantified for 20- to 50-μm particles at 293–295 K. The viscosity is comparable to that of honey at 90% relative humidity (RH), similar to that of peanut butter at 70% RH, and at least as viscous as bitumen at ≤30% RH, implying that the studied SOM ranges from liquid to semisolid or solid across the range of atmospheric RH. These data combined with simple calculations or previous modeling studies are used to show the following: (i) the growth of SOM by the exchange of organic molecules between gas and particle may be confined to the surface region of the particles for RH ≤ 30%; (ii) at ≤30% RH, the particle-mass concentrations of semivolatile and low-volatility organic compounds may be overpredicted by an order of magnitude if instantaneous equilibrium partitioning is assumed in the bulk of SOM particles; and (iii) the diffusivity of semireactive atmospheric oxidants such as ozone may decrease by two to five orders of magnitude for a drop in RH from 90% to 30%. These findings have possible consequences for predictions of air quality, visibility, and climate. PMID:23620520

  15. Incremental Reactivity Effects on Secondary Organic Aerosol Formation in Urban Atmospheres with and without Biogenic Influence

    NASA Astrophysics Data System (ADS)

    Kacarab, Mary; Li, Lijie; Carter, William P. L.; Cocker, David R., III

    2016-04-01

    Two different surrogate mixtures of anthropogenic and biogenic volatile organic compounds (VOCs) were developed to study secondary organic aerosol (SOA) formation at atmospheric reactivities similar to urban regions with varying biogenic influence levels. Environmental chamber simulations were designed to enable the study of the incremental aerosol formation from select anthropogenic (m‑Xylene, 1,2,4-Trimethylbenzene, and 1-Methylnaphthalene) and biogenic (α-pinene) precursors under the chemical reactivity set by the two different surrogate mixtures. The surrogate reactive organic gas (ROG) mixtures were based on that used to develop the maximum incremental reactivity (MIR) factors for evaluation of O3 forming potential. Multiple incremental aerosol formation experiments were performed in the University of California Riverside (UCR) College of Engineering Center for Environmental Research and Technology (CE-CERT) dual 90m3 environmental chambers. Incremental aerosol yields were determined for each of the VOCs studied and compared to yields found from single precursor studies. Aerosol physical properties of density, volatility, and hygroscopicity were monitored throughout experiments. Bulk elemental chemical composition from high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) data will also be presented. Incremental yields and SOA chemical and physical characteristics will be compared with data from previous single VOC studies conducted for these aerosol precursors following traditional VOC/NOx chamber experiments. Evaluation of the incremental effects of VOCs on SOA formation and properties are paramount in evaluating how to best extrapolate environmental chamber observations to the ambient atmosphere and provides useful insights into current SOA formation models. Further, the comparison of incremental SOA from VOCs in varying surrogate urban atmospheres (with and without strong biogenic influence) allows for a unique perspective on the impacts

  16. Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)

    NASA Astrophysics Data System (ADS)

    Pereira, K. L.; Hamilton, J. F.; Rickard, A. R.; Bloss, W. J.; Alam, M. S.; Camredon, M.; Muñoz, A.; Vásquez, M.; Borrás, E.; Ródenas, M.

    2013-12-01

    The increasing demand for palm oil for uses in biofuel and food products is leading to rapid expansion of oil palm agriculture. Methyl chavicol (also known as estragole and 1-allyl-4-methoxybenzene) is an oxygenated biogenic volatile organic compound that was recently identified as the main floral emission from an oil palm plantation in Malaysian Borneo. The emissions of methyl chavicol observed may impact regional atmospheric chemistry, but little is known of its ability to form secondary organic aerosol (SOA). The photo-oxidation of methyl chavicol was investigated at the European Photoreactor chamber as a part of the atmospheric chemistry of methyl chavicol (ATMECH) project. Aerosol samples were collected using a particle into liquid sampler (PILS) and analysed offline using an extensive range of instruments including; high performance liquid chromatography mass spectrometry (HPLC-ITMS), high performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The SOA yield was determined as 18-29% depending on initial precursor (VOC : NOx) mixing ratios. In total, 59 SOA compounds were observed and the structures of 10 compounds have been identified using high resolution tandem mass spectrometry. The addition of hydroxyl and/or nitro functional groups to the aromatic ring appears to be an important mechanistic pathway for aerosol formation. This results in the formation of compounds with both low volatility and high O : C ratios, where functionalisation rather than fragmentation is mainly observed as a~result of the stability of the ring. The SOA species observed can be characterized as semi-volatile to low volatile oxygenated organic aerosol (SVOOA and LVOOA) components and therefore may be important in aerosol formation and growth.

  17. Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)

    NASA Astrophysics Data System (ADS)

    Pereira, K. L.; Hamilton, J. F.; Rickard, A. R.; Bloss, W. J.; Alam, M. S.; Camredon, M.; Muñoz, A.; Vázquez, M.; Borrás, E.; Ródenas, M.

    2014-06-01

    The increasing demand for palm oil for uses in biofuel and food products is leading to rapid expansion of oil palm agriculture. Methyl chavicol (also known as estragole and 1-allyl-4-methoxybenzene) is an oxygenated biogenic volatile organic compound (VOC) that was recently identified as the main floral emission from an oil palm plantation in Malaysian Borneo. The emissions of methyl chavicol observed may impact regional atmospheric chemistry, but little is known of its ability to form secondary organic aerosol (SOA). The photo-oxidation of methyl chavicol was investigated at the European Photoreactor chamber as a part of the atmospheric chemistry of methyl chavicol (ATMECH) project. Aerosol samples were collected using a particle into liquid sampler (PILS) and analysed offline using an extensive range of instruments including; high-performance liquid chromatography mass spectrometry (HPLC-ITMS), high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The SOA yield was determined as 18 and 29% for an initial VOC mixing ratio of 212 and 460 ppbv (parts per billion by volume) respectively; using a VOC:NOx ratio of ~5:1. In total, 59 SOA compounds were observed and the structures of 10 compounds have been identified using high-resolution tandem mass spectrometry. The addition of hydroxyl and/or nitro-functional groups to the aromatic ring appears to be an important mechanistic pathway for aerosol formation. This results in the formation of compounds with both low volatility and high O:C ratios, where functionalisation rather than fragmentation is mainly observed as a result of the stability of the ring. The SOA species observed can be characterised as semi-volatile to low-volatility oxygenated organic aerosol (SVOOA and LVOOA) components and therefore may be important in aerosol formation and growth.

  18. Reactivity of liquid and semisolid secondary organic carbon with chloride and nitrate in atmospheric aerosols.

    PubMed

    Wang, Bingbing; O'Brien, Rachel E; Kelly, Stephen T; Shilling, John E; Moffet, Ryan C; Gilles, Mary K; Laskin, Alexander

    2015-05-14

    Constituents of secondary organic carbon (SOC) in atmospheric aerosols are often mixed with inorganic components and compose a significant mass fraction of fine particulate matter in the atmosphere. Interactions between SOC and other condensed-phase species are not well understood. Here, we investigate the reactions of liquid-like and semisolid SOC from ozonolysis of limonene (LSOC) and α-pinene (PSOC) with NaCl using a set of complementary microspectroscopic analyses. These reactions result in chloride depletion in the condensed phase, release of gaseous HCl, and formation of organic salts. The reactions attributed to acid displacement by SOC acidic components are driven by the high volatility of HCl. Similar reactions can take place in SOC/NaNO3 particles. The results show that an increase in SOC mass fraction in the internally mixed SOC/NaCl particles leads to higher chloride depletion. Glass transition temperatures and viscosity of PSOC were estimated for atmospherically relevant conditions. Data show that the reaction extent depends on SOC composition, particle phase state and viscosity, mixing state, temperature, relative humidity (RH), and reaction time. LSOC shows slightly higher potential to deplete chloride than PSOC. Higher particle viscosity at low temperatures and RH can hinder these acid displacement reactions. Formation of organic salts from these overlooked reactions can alter particle physiochemical properties and may affect their reactivity and ability to act as cloud condensation and ice nuclei. The release and potential recycling of HCl and HNO3 from reacted aerosol particles may have important implications for atmospheric chemistry. PMID:25386912

  19. Secondary Organic Aerosol Formation by Reactive Condensation of Glyoxal and Water Vapor

    NASA Astrophysics Data System (ADS)

    Hastings, W. P.; Koehler, C. A.; de Haan, D. O.

    2004-05-01

    The formation of secondary organic aerosol particles by particle-phase reactions is currently of great interest. Glyoxal has been identified as a significant component in the particle phase in recent smog chamber aromatic oxidation studies. This is surprising because glyoxal has a high vapor pressure and phase partitioning theory would predict that it remain almost entirely in the gas phase. Growth of inorganic seed aerosol in a particle chamber was monitored by scanning mobility particle sizing during addition of gas-phase glyoxal and small amounts of water vapor. Glyoxal was observed to condense on inorganic seed aerosol at concentrations that are at least 100 times below its vapor pressure. This behavior can be explained by a chemical reaction: glyoxal is known to polymerize when exposed to water vapor. This polymerization may be a general mechanism for secondary aerosol formation by alpha-dicarbonyl compounds. The reactivity of hydrated and polymerized forms of glyoxal during analysis by gas chromatography was assessed. Hydrated glyoxal was found to convert to glyoxal at even slightly elevated temperatures in GC injection ports. We then showed that breakdown of solid-phase glyoxal trimer dihydrate, forming gas phase glyoxal and water vapor, occurs at temperatures just above 50 *C, the boiling point of glyoxal. These observations suggest that reports of particle-phase glyoxal are likely caused by GC sampling artifacts, and that the actual particulate species are instead polymerized forms of glyoxal. It does not appear that chemical derivatization protects glyoxal polymers from thermal breakdown during GC analysis. The existence in the particle phase of glyoxal polymers with negligable vapor pressures, rather than volatile glyoxal, is consistent with phase partitioning theory.

  20. Laboratory Studies of the Reactive Chemistry and Changing CCN Properties of Secondary Organic Aerosol, Including Model Development

    SciTech Connect

    Scot Martin

    2013-01-31

    The chemical evolution of secondary-organic-aerosol (SOA) particles and how this evolution alters their cloud-nucleating properties were studied. Simplified forms of full Koehler theory were targeted, specifically forms that contain only those aspects essential to describing the laboratory observations, because of the requirement to minimize computational burden for use in integrated climate and chemistry models. The associated data analysis and interpretation have therefore focused on model development in the framework of modified kappa-Koehler theory. Kappa is a single parameter describing effective hygroscopicity, grouping together several separate physicochemical parameters (e.g., molar volume, surface tension, and van't Hoff factor) that otherwise must be tracked and evaluated in an iterative full-Koehler equation in a large-scale model. A major finding of the project was that secondary organic materials produced by the oxidation of a range of biogenic volatile organic compounds for diverse conditions have kappa values bracketed in the range of 0.10 +/- 0.05. In these same experiments, somewhat incongruently there was significant chemical variation in the secondary organic material, especially oxidation state, as was indicated by changes in the particle mass spectra. Taken together, these findings then support the use of kappa as a simplified yet accurate general parameter to represent the CCN activation of secondary organic material in large-scale atmospheric and climate models, thereby greatly reducing the computational burden while simultaneously including the most recent mechanistic findings of laboratory studies.

  1. Linear regression techniques for use in the EC tracer method of secondary organic aerosol estimation

    NASA Astrophysics Data System (ADS)

    Saylor, Rick D.; Edgerton, Eric S.; Hartsell, Benjamin E.

    A variety of linear regression techniques and simple slope estimators are evaluated for use in the elemental carbon (EC) tracer method of secondary organic carbon (OC) estimation. Linear regression techniques based on ordinary least squares are not suitable for situations where measurement uncertainties exist in both regressed variables. In the past, regression based on the method of Deming [1943. Statistical Adjustment of Data. Wiley, London] has been the preferred choice for EC tracer method parameter estimation. In agreement with Chu [2005. Stable estimate of primary OC/EC ratios in the EC tracer method. Atmospheric Environment 39, 1383-1392], we find that in the limited case where primary non-combustion OC (OC non-comb) is assumed to be zero, the ratio of averages (ROA) approach provides a stable and reliable estimate of the primary OC-EC ratio, (OC/EC) pri. In contrast with Chu [2005. Stable estimate of primary OC/EC ratios in the EC tracer method. Atmospheric Environment 39, 1383-1392], however, we find that the optimal use of Deming regression (and the more general York et al. [2004. Unified equations for the slope, intercept, and standard errors of the best straight line. American Journal of Physics 72, 367-375] regression) provides excellent results as well. For the more typical case where OC non-comb is allowed to obtain a non-zero value, we find that regression based on the method of York is the preferred choice for EC tracer method parameter estimation. In the York regression technique, detailed information on uncertainties in the measurement of OC and EC is used to improve the linear best fit to the given data. If only limited information is available on the relative uncertainties of OC and EC, then Deming regression should be used. On the other hand, use of ROA in the estimation of secondary OC, and thus the assumption of a zero OC non-comb value, generally leads to an overestimation of the contribution of secondary OC to total measured OC.