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1

Formation of secondary organic aerosol by reactive condensation of furandiones, aldehydes, and water vapor onto inorganic aerosol seed particles.  

PubMed

Volatile furandiones and aldehydes are significant atmospheric oxidation products of aromatic compounds. The mechanism of secondary organic aerosol formation by these compounds was probed using particle chamber observations and macroscale simulations of condensed phases. Growth of inorganic seed aerosol was monitored in the presence of humidity and high concentrations of 2,5-furandione (maleic anhydride), 3-methyl-2,5-furandione (citraconic anhydride), benzaldehyde, and trans-cinnamaldehyde. Particle growth commenced when the gas-phase saturation level of each organic compound and water vapor (relative to its pure liquid), when summed together, reached a threshold near one, implying the formation of a nearly ideal mixed organic/aqueous phase. However, these organics are immiscible with water at the high mole fractions that would be expected in such a phase. Highly acidic dicarboxylic acids produced by the reactions between furandiones and water were shown to rapidly acidify an aqueous phase, resulting in greatly increased benzaldehyde solubility. Thus, the uptake of these organics onto particles in the presence of humidity appears to be reaction-dependent. Finally, it is shown that dicarboxylic acids produced in these reactions recyclize back to furandiones when subjected to normal GC injector temperatures, which could cause large artifacts in gas/particle phase distribution measurements. PMID:15506200

Koehler, Charles A; Fillo, Jeremiah D; Ries, Kyle A; Sanchez, Josi T; De Haan, David O

2004-10-01

2

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

SciTech Connect

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.

Paulson, S E

2012-05-30

3

Degradation of SO 2, NO 2 and NH 3 leading to formation of secondary inorganic aerosols: An environmental chamber study  

NASA Astrophysics Data System (ADS)

We have examined the interactions of gaseous pollutants and primary aerosols that can produce secondary inorganic aerosols. The specific objective was to estimate degradation rates of precursor gases (NH 3, NO 2 and SO 2) responsible for formation of secondary inorganic aerosols. A Teflon-based outdoor environmental chamber facility (volume 12.5 m 3) was built and checked for wall losses, leaks, solar transparency and ability to simulate photochemical reactions. The chamber was equipped with state-of-the-art instrumentation to monitor concentration-time profiles of precursor gases, ozone, and aerosol. A total of 14 experimental runs were carried out for estimating the degradation of precursor gases. The following initial conditions were maintained in the chamber: NO 2 = 246 ± 104 ppb(v), NH 3 = 548 ± 83 ppb(v), SO 2 = 238 ± 107 ppb(v), O 3 = 50 ± 11 ppb(v), PM 2.5 aerosol = 283438 ± 60524 No./litre. The concentration-time profile of gases followed first-order decay and were used for estimating degradation rates (NO 2 = 0.26 ± 0.15 h -1, SO 2 = 0.31 ± 0.17 h -1, NH 3 = 0.35 ± 0.21 h -1). We observed that degradation rates showed a statistical significant positive correlation (at 5% level of significance) with the initial PM 2.5 levels in the chamber (coefficient of correlation: 0.63 for NO 2; 0.62 for NH 3 and 0.51 for SO 2), suggesting that the existing surface of the aerosol could play a significant role in degradation of precursor gases. One or more gaseous species can be adsorbed on to the existing particles and these may undergo heterogeneous or homogeneous chemical transformation to produce secondary inorganic aerosols. Through correlation analysis, we have observed that degradation rates of precursor gases were dependent on initial molar ratio of (NH 3)/(NO 2 + SO 2), indicative of ammonia-rich and ammonia-poor situations for eventual production of ammonium salts.

Behera, Sailesh N.; Sharma, Mukesh

2011-08-01

4

Monitoring of atmospheric particulate matter around sources of secondary inorganic aerosol  

NASA Astrophysics Data System (ADS)

A physicochemical characterisation of airborne particulate matter (PM) was performed in a region affected by the emissions from a source of precursors of secondary inorganic aerosols (SIA, 1050 MW power plant). This characterisation sought to study the interferences of other possible natural and anthropogenic sources when monitoring PM10, PM2.5 and PM1 around this emission source. The study was performed in the semi-arid Ebro basin and Catalan and Iberian ranges (Eastern Spain) and consisted in (1) monitoring the transport and impacts on the ground of the SO2 plume (fumigation), (2) chemically characterising (25 PM components) of TSP-size fractions, and diurnal and nocturnal PM10 and PM2.5 samples, and (3) in measuring the PM mass size distribution. This PM characterisation was undertaken in ambient air, during fumigations of the SO2 plume on the ground and around other local PM sources. PM1 was found to be the best parameter for monitoring PM pollution derived from the SO2 emissions owing to the formation of ammonium-sulphate in the finest PM fractions. Three PM1 & PM2.5 events were recorded during the field measurement campaign: two events were caused by ammonium-sulphate episodes, the third was due to an African dust outbreak. PM-mass size distribution and the high correlation of PM1 with SO2 during the SO2 fumigation events suggest that a significant fraction of sulphate is formed by means of `new particle formation' processes (nucleation). PM10 presents a much higher variability (noise) than PM1 & PM2.5 owing to the re-suspension of coarse (2.5- 10?m) mineral dust particles. The PM1 load in PM10 undergoes significant variations: 60-80% during plume fumigations, 20-60% in ambient air, and down to 10% in areas affected by mineral dust re-suspension. The daily cycles observed in some PM components (sulphate, nitrate and mineral dust elements) and the chemical features of PM are also described in detail.

Alastuey, A.; Querol, X.; Rodríguez, S.; Plana, F.; Lopez-Soler, A.; Ruiz, C.; Mantilla, E.

5

Ionic composition of PM2.5 at urban sites of northern Greece: secondary inorganic aerosol formation.  

PubMed

This study investigates the water-soluble ionic constituents (Na(+), K(+), NH4 (+), Ca(2+), Mg(2+), Cl(-), NO3 (-), SO4 (2-)) associated to PM2.5 particle fraction at two urban sites in the city of Thessaloniki, northern Greece, an urban traffic site (UT) and urban background site (UB). Ionic constituents represent a significant fraction of PM2.5 mass (29.6 at UT and 41.5 % at UB). The contribution of marine aerosol was low (<1.5 %). Secondary inorganic aerosols (SIA) represent a significant fraction of PM2.5 mass contributing to 26.9 ± 12.4 % and 39.2 ± 13.2 % at UT and UB sites, respectively. Nitrate and sulfate are fully neutralized by ammonium under the existing conditions. The ionic constituents were evaluated in relation to their spatial and temporal variation, their gaseous precursors, meteorological conditions, local and long-range transport. PMID:24363054

Voutsa, D; Samara, C; Manoli, E; Lazarou, D; Tzoumaka, P

2014-04-01

6

Secondary inorganic aerosol evaluation: Application of a transport chemical model in the eastern part of the Po Valley  

NASA Astrophysics Data System (ADS)

Secondary inorganic aerosol (SIA) represents an important component of fine particulate matter in Europe. A photochemical model has been used to assess the distribution of secondary inorganic ions (sulfate, nitrate and ammonium) in the eastern part of the Po Valley, close to Venice. Specific meteorological and environmental conditions and very highly urbanized and industrialized areas make this domain one of the most polluted in Europe. Several studies have been conducted to assess particulate matter (PM10 and PM2.5) areal distribution. However, SIA formation dynamics are still a research subject especially in the transition environments, where the changes in the orography and in the land-use can affect air mass movements and atmospheric composition. This paper is a first attempt to simulate SIA distribution by using a photochemical model in the sea/land Venice transition area. Moreover, a modeling approach with clean boundary conditions has been used to check local and regional influence on SIA levels in the domain. Results reveal that, despite the importance of regional influences, local formation processes are important in SIA distribution especially during warm periods. SO42- and NH4+ are more linked to emission sources distribution than NO3- that tends to be more diffused in the study area. The use of a photochemical model, suitably tested in a such complex area, can improve air pollution knowledge and can help in air quality decision making.

Pecorari, Eliana; Squizzato, Stefania; Longo, Andrea; Visin, Flavia; Rampazzo, Giancarlo

2014-12-01

7

CCN activity of aliphatic amine secondary aerosol  

NASA Astrophysics Data System (ADS)

Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, ? ? 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3), contains less volatile compounds than the primary aliphatic amine (BA) aerosol. TMA + N2O5 form semi-volatile organics in low RH conditions that have ? ~ 0.20, indicative of slightly soluble organic material. As RH increases, several inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. Higher CCN activity (? > 0.3) was also observed for humid BA+N2O5 aerosols compared with dry aerosol (? ~ 0.2), as a result of the formation of inorganic salts such as NH4NO3 and butylamine nitrate (C4H11N · HNO3). Compared with TMA, BA+N2O5 reactions produce more volatile aerosols. The BA+N2O5 aerosol products under humid experiments were found to be very sensitive to the temperature within the stream-wise continuous flow thermal gradient CCN counter. The CCN counter, when set above a 21 °C temperature difference, evaporates BA+N2O5 aerosol formed at RH ? 30%; ? ranges from 0.4 to 0.7 and is dependent on the instrument supersaturation (ss) settings. The aerosol behaves non-ideally, hence simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems ? ranges from 0.2 < ? < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. Thermal gradient CCN counters measurement will impact the observed CCN activity of volatile aerosol formed via a nitric acid pathway. The contributions of semi-volatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems.

Tang, X.; Price, D.; Praske, E.; Vu, D.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

2014-01-01

8

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

SciTech Connect

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.

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

1999-06-07

9

Using hourly measurements to explore the role of secondary inorganic aerosol in PM2.5 during haze and fog in Hangzhou, China  

NASA Astrophysics Data System (ADS)

This paper explores the role of the secondary inorganic aerosol (SIA) species ammonium, NH{4/+}, nitrate, NO{3/-}, and sulfate, SO{4/2-}, during haze and fog events using hourly mass concentrations of PM2.5 measured at a suburban site in Hangzhou, China. A total of 546 samples were collected between 1 April and 8 May 2012. The samples were analyzed and classified as clear, haze or fog depending on visibility and relative humidity (RH). The contribution of SIA species to PM2.5 mass increased to ˜50% during haze and fog. The mass contribution of nitrate to PM2.5 increased from 11% during clear to 20% during haze episodes. Nitrate mass exceeded sulfate mass during haze, while near equal concentrations were observed during fog episodes. The role of RH on the correlation between concentrations of SIA and visibility was examined, with optimal correlation at 60%-70% RH. The total acidity during clear, haze and fog periods was 42.38, 48.38 and 45.51 nmol m-3, respectively, indicating that sulfate, nitrate and chloride were not neutralized by ammonium during any period. The nitrate to sulfate molar ratio, as a function of the ammonium to sulfate molar ratio, indicated that nitrate formation during fog started at a higher ammonium to sulfate molar ratio compared to clear and haze periods. During haze and fog, the nitrate oxidation ratio increased by a factor of 1.6-1.7, while the sulfur oxidation ratio increased by a factor of 1.2-1.5, indicating that both gaseous NO2 and SO2 were involved in the reduced visibility.

Jansen, Roeland Cornelis; Shi, Yang; Chen, Jianmin; Hu, YunJie; Xu, Chang; Hong, Shengmao; Li, Jiao; Zhang, Min

2014-11-01

10

Effect of acidity on secondary organic aerosol formation from isoprene.  

PubMed

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 closely correlated to increasing aerosol acidity (R2 = 0.979). Direct chemical evidence for acid-catalyzed particle-phase reactions was obtained from the SOA chemical analyses. Aerosol mass concentrations for the 2-methyltetrols, as well as the newly identified sulfate esters, both of which serve as tracers for isoprene SOA in ambient aerosols, increased significantly with enhanced aerosol acidity. Aerosol acidities, as measured in nmol of H+ m(-3), employed in the present study are in the same range as those observed in tropospheric aerosol collected from the eastern U.S. PMID:17822103

Surratt, Jason D; Lewandowski, Michael; Offenberg, John H; Jaoui, Mohammed; Kleindienst, Tadeusz E; Edney, Edward O; Seinfeld, John H

2007-08-01

11

Cloud droplet activation of secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Measurements of hygroscopicity and cloud condensation nuclei (CCN) activity were conducted on secondary organic aerosol (SOA) formed in a smog chamber. SOA precursors included ?-pinene, ?-pinene, ?3-carene, and toluene, representative of both naturally and anthropogenically emitted organic species. Measured CCN activation was comparable for all of the species studied and occurred at humidity conditions which are readily attained in the atmosphere. Further, there was little variation in hygroscopic growth between compounds. However, measured droplet activation conditions were inconsistent with hygroscopicity measured below water saturation and Köhler theory expressions based on Raoult's law for several parameterizations for water activity. In the atmosphere, SOA may compose a large fraction of atmospheric particulate matter and will often exist internally mixed with inorganic species. Using the current results, we compare SOA to insoluble organic species to calculate CCN activation from mixed organic-sulfate particles for a range of atmospheric conditions. We find that droplet activation behavior of mixed particles containing SOA is the same as that of mixed particles for which the organic component is nonhygroscopic, except for cases in which there are low particle concentrations, low updraft velocities, and the aerosol composition is dominated by organics.

Prenni, Anthony J.; Petters, Markus D.; Kreidenweis, Sonia M.; Demott, Paul J.; Ziemann, Paul J.

2007-05-01

12

The Chemistry of Mixed Sodium Chloride and Sodium Nitrate Aerosol Particles: Impacts of a Secondary Inorganic Ion on Gas Phase Chlorine Production  

NASA Astrophysics Data System (ADS)

Unique chemistry at the air-water interface from the reaction of the chloride ion and the hydroxyl radical has been suggested to play a major role in the production of increased levels of molecular chlorine in the marine boundary layer, including coastal regions. Molecular chlorine can then be photolyzed by solar radiation to produce the highly reactive atomic chlorine radical. Laboratory studies have shown that an interfacial reaction between chloride ion and the hydroxyl radical is responsible for generation of molecular chlorine at concentrations which cannot be explained by well-known bulk aqueous chemistry. Molecular dynamics (MD) simulations of chloride ion solutions as well as sum frequency generation studies have shown that the chloride ion has a propensity for the air-water interface. We examine here how the addition of nitrate ion to the aerosol, which is also believed to have a significant interfacial concentration in pure nitrate particles, affects the production of molecular chlorine. Laboratory experiments using mixed NaCl/NaNO3 aerosol particles were performed in a 561 L aerosol chamber at 298 K, 1 atm, and ~85% relative humidity, above the deliquescence points for both salts. Aerosol particles were generated using a commercial atomizer and Cl2 production was measured using atmospheric pressure chemical-ionization mass spectrometry; long path FTIR and DOAS were also used for monitoring ozone and the formation of reaction products. Ozone photolysis at 254 nm was used as a hydroxyl radical source. Molecular chlorine formation is observed from the reaction of the mixed NaCl/NaNO3 aerosol with OH, suggesting that at least some of the chloride remains at the interface in the mixed NaCl/NaNO3 particles. The results of chamber experiments with varying aerosol composition and size will be presented and interpreted in the context of molecular dynamics simulations of pure chloride, pure nitrate and mixed composition aerosol. The implications of this work for the production of reactive chlorine atoms in the troposphere will be discussed.

Wingen, L. M.; Moskun, A. C.; Thomas, J. L.; Roeselova, M.; Tobias, D. J.; Finlayson-Pitts, B. J.

2005-12-01

13

Collection and analysis of inorganic and water soluble organic aerosols over Maryland and Virginia  

NASA Astrophysics Data System (ADS)

Aerosols aloft have slower removal than those near the ground, in part, because dry and wet deposition rates result in longer lifetimes and greater range of influence. Knowledge of deposition rates and range of transport for different species are important for developing local and regional air quality policy. Currently, the vertical distribution of organic aerosols (OA's) and their polar, oxidized fraction is largely unknown. Comprehensive methods to analyze aerosol composition collected in the boundary layer and the lower free troposphere are lacking. During DISCOVER AQ 2011, both the NASA P3 and Cessna 402B collected aerosols, through shrouded aerosol inlets, onto Teflon and quartz fiber filters. Collection occurred in both the boundary layer and lower free troposphere over Maryland and Virginia, USA. After extraction with water and optimizing separation via ion chromatography, commonly identified secondary organic aerosols can be separated based on their functionality as mono-, di-, or polycarboxylic acids. Inorganic aerosol components can simultaneously be separated and identified with the same method. Individual organic acid compound analysis with detection limits in the low ppb range can be achieved when conductivity/ultraviolet/ and mass spectrometric detectors are placed in tandem. Additionally, thermo optical analysis can be used to determine the mass fraction of water soluble organic carbon versus the total collected mass. This research is designed to provide information on the vertical distribution of particulate organic carbon in the atmosphere, its optical properties, information on aerosol transport in the lower free troposphere, and to provide water soluble organic aerosol structural characterization.

Brent, L. C.; Ziemba, L. D.; Beyersdorf, A. J.; Phinney, K.; Conny, J.; Dickerson, R. R.

2012-12-01

14

NO3 radical, OH radical and O3-initiated secondary aerosol formation from aliphatic amines  

NASA Astrophysics Data System (ADS)

Aliphatic amines enter the atmosphere from a variety of sources, and exist in both gas and particle phases in the atmosphere. Similar to ammonia, amines can form inorganic salts through acid-base reactions. However, the atmospheric behavior of amines with atmospheric oxidants (e.g. the nitrate radical (NO3), the hydroxyl radical (OH), O3) is still poorly understood. In this study, chamber experiments were conducted to explore the reaction between three aliphatic amines and HNO3/O3/NO3/OH. Effects of water vapor were also explored by conducting experiments under different relative humidity conditions (RH<0.1% to ˜40%). Results show that all three amines have a high potential to form secondary aerosol in reactions with NO3, and are affected by the presence of water vapor. DEA and BA are capable of forming a significant amount of stable inorganic salt at ppb level concentrations, while TMA tends to form mostly non-salt secondary organic aerosol under dry conditions. The OH photooxidation of amines has much lower secondary aerosol yield and is independent of relative humidity, while ozonolysis produced negligible amount of aerosol. Secondary aerosol from OH oxidation was composed of organic components only, due to the lack of acid source. This study shows that night time chemistry of aliphatic amines can produce secondary organic and inorganic aerosol mixtures, and the relative contribution of each component depends on the environment relative humidity.

Tang, Xiaochen; Price, Derek; Praske, Eric; Lee, Su Anne; Shattuck, Morgan A.; Purvis-Roberts, Kathleen; Silva, Philip J.; Asa-Awuku, Akua; Cocker, David R.

2013-06-01

15

Factor analysis of combined organic and inorganic aerosol mass spectra from high resolution aerosol mass spectrometer measurements  

NASA Astrophysics Data System (ADS)

Positive matrix factorization (PMF) was applied to the merged high resolution mass spectra of organic and inorganic aerosols from aerosol mass spectrometer (AMS) measurements to investigate the sources and evolution processes of submicron aerosols in New York City in summer 2009. This new approach is able to study the distribution of organic and inorganic species in different types of aerosols, the acidity of organic aerosol (OA) factors, and the fragment ion patterns related to photochemical processing. In this study, PMF analysis of the unified AMS spectral matrix resolved 8 factors. The hydrocarbon-like OA (HOA) and cooking OA (COA) factors contain negligible amounts of inorganic species. The two factors that are primarily ammonium sulfate (SO4-OA) and ammonium nitrate (NO3-OA), respectively, are overall neutralized. Among all OA factors the organic fraction of SO4-OA shows the highest degree of oxidation (O/C = 0.69). Two semi-volatile oxygenated OA (OOA) factors, i.e., a less oxidized (LO-OOA) and a more oxidized (MO-OOA), were also identified. MO-OOA represents local photochemical products with a diurnal profile exhibiting a pronounced noon peak, consistent with those of formaldehyde (HCHO) and Ox(= O3 + NO2). The NO+/NO2+ ion ratio in MO-OOA is much higher than that in NO3-OA and in pure ammonium nitrate, indicating the formation of organic nitrates. The nitrogen-enriched OA (NOA) factor contains ~25% of acidic inorganic salts, suggesting the formation of secondary OA via acid-base reactions of amines. The size distributions of OA factors derived from the size-resolved mass spectra show distinct diurnal evolving behaviors but overall a progressing evolution from smaller to larger particle mode as the oxidation degree of OA increases. Our results demonstrate that PMF analysis of the unified aerosol mass spectral matrix which contains both inorganic and organic aerosol signals may enable the deconvolution of more OA factors and gain more insights into the sources, processes, and chemical characteristics of OA in the atmosphere.

Sun, Y. L.; Zhang, Q.; Schwab, J. J.; Yang, T.; Ng, N. L.; Demerjian, K. L.

2012-09-01

16

Evolved gas analysis of secondary organic aerosols  

SciTech Connect

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.

Grosjean, D.; Williams, E.L. II; Grosjean, E. (DGA, Inc., Ventura, CA (United States)); Novakov, T. (Lawrence Berkeley Lab., CA (United States))

1994-11-01

17

Evidence for organosulfates in secondary organic aerosol.  

PubMed

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 alpha-pinene and isoprene, in the presence or absence of sulfate seed aerosol, is investigated through a series of controlled chamber experiments in two separate laboratories. By using electrospray ionization-mass spectrometry, sulfate esters in SOA produced in laboratory photooxidation experiments are identified for the first time. Sulfate esters are found to account for a larger fraction of the SOA mass when the acidity of seed aerosol is increased, a result consistent with aerosol acidity increasing SOA formation. Many of the isoprene and alpha-pinene sulfate esters identified in these chamber experiments are also found in ambient aerosol collected at several locations in the southeastern U.S. It is likely that this pathway is important for other biogenic terpenes, and may be important in the formation of humic-like substances (HULIS) in ambient aerosol. PMID:17310716

Surratt, Jason D; Kroll, Jesse H; Kleindienst, Tadeusz E; Edney, Edward O; Claeys, Magda; Sorooshian, Armin; Ng, Nga L; Offenberg, John H; Lewandowski, Michael; Jaoui, Mohammed; Flagan, Richard C; Seinfeld, John H

2007-01-15

18

Glass transition measurements in mixed organic and organic/inorganic aerosol particles  

NASA Astrophysics Data System (ADS)

The recent proposal of a semi-solid or glassy state of secondary organic aerosol (SOA) particles has sparked intense research in that area. In particular, potential effects of a glassy aerosol state such as incomplete gas-to-particle partitioning of semi-volatile organics, inhibited chemical reactions and water uptake, and the potential to act as heterogeneous ice nuclei have been identified so far. Many of these studies use well-studied proxies for oxidized organics such as sugars or other polyols. There are, however, few measurements on compounds that do exist in atmospheric aerosol particles. Here, we have performed studies on the phase state of organics that actually occur in natural SOA particles arising from the oxidation of alpha-pinene emitted in boreal forests. We have investigated the two marker compounds pinonic acid and 3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA) and their mixtures. 3-MBCTA was synthesized from methyl isobutyrate and dimethyl maleate in two steps. In order to transfer these substances into a glassy state we have developed a novel aerosol spray drying technique. Dilute solutions of the relevant organics are atomized into aerosol particles which are dried subsequently by diffusion drying. The dried aerosol particles are then recollected in an impactor and studied by means of differential scanning calorimetry (DSC), which provides unambiguous information on the aerosols' phase state, i.e. whether the particles are crystalline or glassy. In the latter case DSC is used to determine the glass transition temperature Tg of the investigated samples. Using the above setup we were able to determine Tg of various mixtures of organic aerosol compounds as a function of their dry mass fraction, thus allowing to infer a relation between Tg and the O:C ratio of the aerosols. Moreover, we also studied the glass transition behavior of mixed organic/inorganic aerosol particles, including the effects of liquid-liquid phase separation upon drying.

Dette, Hans Peter; Qi, Mian; Schröder, David; Godt, Adelheid; Koop, Thomas

2014-05-01

19

Secondary Ion Mass Spectrometry of Environmental Aerosols  

SciTech Connect

Atmospheric particles influence many aspects of climate, air quality and human health. Understanding the composition, chemistry and behavior of atmospheric aerosols is a key remaining challenge in improving climate models. Furthermore, particles may be traced back to a particular source based on composition, stable isotope ratios, or the presence of particular surface chemistries. Finally, the characterization of atmospheric particles in the workplace plays an important role in understanding the potential for exposure and environmental and human health effects to engineered and natural nanoscale particles. Secondary ion mass spectrometry (SIMS) is a useful tool in determining any of several aspects of the structure, composition and chemistry of these particles. Often used in conjunction with other surface analysis and electron microscopy methods, SIMS has been used to determine or confirm reactions on and in particles, the presence of particular organic species on the surface of atmospheric aerosols and several other interesting and relevant findings. Various versions of SIMS instruments – dynamic SIMS, time of flight secondary ion mass spectrometry or TOF-SIMS, nanoSIMS – have been used to determine specific aspects of aerosol structure and chemistry. This article describes the strengths of each type of SIMS instrument in the characterization of aerosols, along with guidance on sample preparation, specific characterization specific to the particular information sought in the analysis. Examples and guidance are given for each type of SIMS analysis.

Gaspar, Daniel J.; Cliff, John B.

2010-08-01

20

Formation of secondary aerosols: impact of the gas-phase chemical mechanism  

NASA Astrophysics Data System (ADS)

The impact of two recent gas-phase chemical kinetic mechanisms (CB05 and RACM2) on the formation of secondary inorganic and organic aerosols is compared for simulations of PM2.5 over Europe between 15 July and 15 August 2001. The host chemistry transport model is Polair3D of the Polyphemus air-quality platform. Particulate matter is modeled with SIREAM, which is coupled to the thermodynamic model ISORROPIA and to the secondary organic aerosol module MAEC. Model performance is satisfactory with both mechanisms for speciated PM2.5. The monthly-mean difference of the concentration of PM2.5 is less than 1 ?g/m3 (6%) over the entire domain. Secondary chemical components of PM2.5 include sulfate, nitrate, ammonium and organic aerosols, and the chemical composition of PM2.5 is not significantly different between the two mechanisms. Monthly-mean concentrations of inorganic aerosol are higher with RACM2 than with CB05 (+16% for sulfate, +11% for nitrate, and +12% for ammonium), whereas the concentrations of organic aerosols are slightly higher with CB05 than with RACM2 (+26% for anthropogenic SOA and +1% for biogenic SOA). Differences in the inorganic and organic aerosols result primarily from differences in oxidant concentrations (OH, O3 and NO3). Nitrate formation tends to be HNO3-limited over land and differences in the concentrations of nitrate are due to differences in concentration of HNO3. Differences in aerosols formed from aromatics SVOC are due to different aromatics oxidation between CB05 and RACM2. The aromatics oxidation in CB05 leads to more cresol formation, which then leads to more SOA. Differences in the aromatics aerosols would be significantly reduced with the recent CB05-TU mechanism for toluene oxidation. Differences in the biogenic aerosols are due to different oxidant concentrations (monoterpenes) and different particulate organic mass concentrations affecting the gas-particle partitioning of SOA (isoprene).

Kim, Y.; Sartelet, K.; Seigneur, C.

2010-08-01

21

Characterizing the formation of secondary organic aerosols  

SciTech Connect

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 concentrations of important gas phase nitrogen compounds. Experiments have been ongoing at the Blodgett field site since the fall of 2000, and have included portions of the summer and fall of 2001, 2002, and 2003. Analysis of both the gas and particle phase data from the year 2000 show that the particle loading at the site correlates with both biogenic precursors emitted in the forest and anthropogenic precursors advected to the site from Sacramento and the Central Valley of California. Thus the particles at the site are affected by biogenic processing of anthropogenic emissions. Size distribution measurements show that the aerosol at the site has a geometric median diameter of approximately 100 nm. On many days, in the early afternoon, growth of nuclei mode particles (<20 nm) is also observed. These growth events tend to occur on days with lower average temperatures, but are observed throughout the summer. Analysis of the size resolved data for these growth events, combined with typical measured terpene emissions, show that the particle mass measured in these nuclei mode particles could come from oxidation products of biogenic emissions, and can serve as a significant route for SOA partitioning into the particle phase. During periods of each year, the effect of emissions for forest fires can be detected at the Blodgett field location. During the summer of 2002 emissions from the Biscuit fire, a large fire located in Southwest Oregon, was detected in the aerosol data. The results show that increases in particle scattering can be directly related to increased black carbon concentration and an appearance of a larger mode in the aerosol size distribution. These results show that emissions from fires can have significant impact on visibility over large distances. The results also reinforce the view that forest fires can be a significant source of black carbon in the atmosphere, which has important climate and visibility. Continuing work with the 2002 data set, particularly the combination of the aerosol and gas phase data, will continue to provide important information o

Lunden, Melissa; Black, Douglas; Brown, Nancy

2004-02-01

22

Organosulfate formation in biogenic secondary organic aerosol.  

PubMed

Organosulfates of isoprene, alpha-pinene, and beta-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 series of laboratory photooxidation (i.e., OH-initiated oxidation) and nighttime oxidation (i.e., NO3-initiated oxidation under dark conditions) experiments using nine monoterpenes (alpha-pinene, beta-pinene, d-limonene, l-limonene, alpha-terpinene, gamma-terpinene, terpinolene, Delta(3)-carene, and beta-phellandrene) and three monoterpenes (alpha-pinene, d-limonene, and l-limonene), respectively. Organosulfates were characterized using liquid chromatographic techniques coupled to electrospray ionization combined with both linear ion trap and high-resolution time-of-flight mass spectrometry. Organosulfates are formed only when monoterpenes are oxidized in the presence of acidified sulfate seed aerosol, a result consistent with prior work. Archived laboratory-generated isoprene SOA and ambient filter samples collected from the southeastern U.S. were reexamined for organosulfates. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory-generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, alpha-pinene, beta-pinene, and limonene-like monoterpenes (e.g., myrcene), demonstrating the ubiquity of organosulfate formation in ambient SOA. Several of the organosulfates of isoprene and of the monoterpenes characterized in this study are ambient tracer compounds for the occurrence of biogenic SOA formation under acidic conditions. Furthermore, the nighttime oxidation experiments conducted under highly acidic conditions reveal a viable mechanism for the formation of previously identified nitrooxy organosulfates found in ambient nighttime aerosol samples. We estimate that the organosulfate contribution to the total organic mass fraction of ambient aerosol collected from K-puszta, Hungary, a field site with a similar organosulfate composition as that found in the present study for the southeastern U.S., can be as high as 30%. PMID:18710205

Surratt, Jason D; Gómez-González, Yadian; Chan, Arthur W H; Vermeylen, Reinhilde; Shahgholi, Mona; Kleindienst, Tadeusz E; Edney, Edward O; Offenberg, John H; Lewandowski, Michael; Jaoui, Mohammed; Maenhaut, Willy; Claeys, Magda; Flagan, Richard C; Seinfeld, John H

2008-09-11

23

Chemistry of secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

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 effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.

Yee, Lindsay Diana

24

Characteristics of major secondary ions in typical polluted atmospheric aerosols during autumn in central Taiwan  

Microsoft Academic Search

In autumn of 2008, the chemical characteristics of major secondary ionic aerosols at a suburban site in central Taiwan were measured during an annually occurring season of high pollution. The semicontinuous measurement system measured major soluble inorganic species, including NH4+, NO3?, and SO42?, in PM10 with a 15 min resolution time. The atmospheric conditions, except for the influences of typhoons, were dominated

Guor-Cheng Fang; Shih-Chieh Lin; Shih-Yu Chang; Chuan-Yao Lin; Charles-C. K. Chou; Yun-Jui Wu; Yu-Chieh Chen; Wei-Tzu Chen; Tsai-Lin Wu

2011-01-01

25

Influence of aerosol acidity on the formation of secondary organic aerosol from biogenic precursor hydrocarbons.  

PubMed

Secondary organic carbon (SOC) concentrations in steady-state aerosol were measured in a series of alpha-pinene/NOx and one series of beta-caryophyllene/NOx irradiation experiments. The acidity of the inorganic seed aerosol was varied while the hydrocarbon and NOx concentrations were held constant in each series of experiments. Measurements were made for acidity levels and SOC concentrations much closer to ambient levels than had been previously achieved for alpha-pinene, while there are no previous measurements for SOC increases due to acidity for beta-caryophyllene. The observed enhancement in SOC concentration linearly increases with the measured hydrogen ion concentration in air for each system. For the conditions of these studies, SOC increased by 0.04% per nmol H+ m(-3) for alpha-pinene under two conditions where the organic carbon concentration differed by a factor of 5. For alpha-pinene, this level of response to acidic aerosol was a factor of 8 lower than was reported by Surratt et al. for similar series of experiments for SOC from the photooxidation of isoprene/NOx mixtures. By contrast, SOC from beta-caryophyllene showed an increase of 0.22% per nmol H+ m(-3), roughly two-thirds of the response in the isoprene system. Mass fractions for SOC particle-phase tracers for alpha-pinene decreased slightly with increasing aerosol acidity, although remaining within previously stated uncertainties. Below 200 nmol H+ m(-3), the mass fraction of beta-caryophyllenic acid, the only identified tracer for beta-caryophyllene SOC, was constant although beta-caryophyllenic acid showed a substantial decrease for acidities greater than 400 nmol H+ m(-3). PMID:19921888

Offenberg, John H; Lewandowski, Michael; Edney, Edward O; Kleindienst, Tadeusz E; Jaoui, Mohammed

2009-10-15

26

A COMPARATIVE REVIEW OF INORGANIC AEROSOL THERMODYNAMIC EQUILIBRIUM MODULES: SIMILARITIES, DIFFERENCES, AND THEIR LIKELY CAUSES  

EPA Science Inventory

A comprehensive comparison of five inorganic aerosol thermodynamic equilibrium modules, MARS-A, SEQUILIB, SCAPE2, EQUISOLV II, and AIM2, was conducted for a variety of atmospheric concentrations of particulate matter (PM) constituents, relative humidities (RHs), and temperatures....

27

Formation of semivolatile inorganic aerosols in the Mexico City Metropolitan Area during the MILAGRO campaign  

E-print Network

One of the most challenging tasks for chemical transport models (CTMs) is the prediction of the formation and partitioning of the major semi-volatile inorganic aerosol components (nitrate, chloride, ammonium) between the ...

Karydis, V. A.

28

Aqueous phase processing of secondary organic aerosols  

NASA Astrophysics Data System (ADS)

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, ?-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 ?g 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 ?-pinene, whereas it affected that formed from TMB. For the two first precursors, the aqueous phase chemical composition of SOA was further investigated using offline measurements, i.e. ion chromatography coupled to a mass spectrometer (IC-MS) and an atmospheric pressure chemical ionization mass spectrometer (APCI-MS) equipped with high pressure liquid chromatography (HPLC-MS). These analyses showed that aqueous phase processing enhanced the formation of some compounds already present in the SOA, thus confirming the aging effect of aqueous phase processes. For isoprene experiments, additional new compounds, likely oligomers, were formed through aqueous phase photooxidation, and their possible origins are discussed.

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

29

Cloud Droplet Activation of Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Measurements will be presented of water uptake and cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) formed in a smog chamber. SOA precursors included alpha-pinene, beta-pinene, delta- 3-carene, and toluene. Below water saturation, hygroscopicity was invariant between compounds and was generally consistent with previous measurements. Measured growth factors were approximately 1.05 at 85% relative humidity. Measured CCN activation also was comparable for all of the species studied; particles 100 nm in diameter activated at approximately 0.4% supersaturation. We attempt to link the hygroscopicity and CCN measurements, but find that measured droplet activation conditions were inconsistent with hygroscopicity measured below water saturation and Köhler theory expressions based on Raoult's Law. We explore several possible reasons for this discrepancy. Finally, using the current CCN measurements, we compare SOA to other non-hygroscopic organic species to calculate CCN activation from mixed organic-sulfate particles for a range of organic fractions and a range of atmospheric conditions.

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

2006-12-01

30

A review of Secondary Organic Aerosol (SOA) formation from isoprene  

E-print Network

Recent field and laboratory evidence indicates that the oxidation of isoprene, (2-methyl-1,3-butadiene, C[subscript 5]H[subscript 8]) forms secondary organic aerosol (SOA). Global biogenic emissions of isoprene (600 Tg ...

Kroll, Jesse

31

Secondary organic aerosol formation from road vehicle emissions  

NASA Astrophysics Data System (ADS)

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. Furthermore, we observed that vehicle emissions and SOA are significantly affected by temperature and RH: doubling the RH in the chamber resulted in significantly increased SOA formation. Primary emissions and secondary aerosol formation from diesel and gasoline vehicles will be compared at different temperature and RH. Also the interaction and influence of inorganics on organics will be discussed. References: [1] Robinson, A.L., et al. (2007) Science 315, 1259. [2] Weitkamp, E.A., et al. (2007) Environ. Sci. Technol. 41, 6969. [3] Bahreini, R., et al. (2012) Geophys. Res. Lett. 39, L06805. [4] Gentner, D.R. et al. (2012) PNAS 109, 18318. [5] Gordon, T.D. et al. (2013) Atmos. Chem. Phys. Discuss 13, 23173. [6] Platt, S.M., et al. (2013) Atmos. Chem. Phys. Discuss. 12, 28343.

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

32

A large source of low-volatility secondary organic aerosol  

NASA Astrophysics Data System (ADS)

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 ?-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.

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

33

A large source of low-volatility secondary organic aerosol.  

PubMed

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 ?-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

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

34

Modeling the Thermodynamics of Mixed Organic-Inorganic Aerosols to Predict Water Activities and Phase Equilibria  

NASA Astrophysics Data System (ADS)

Tropospheric aerosol particles contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behavior. While the thermodynamics of aqueous inorganic systems at atmospheric temperatures are well established, little is known about the physicochemistry of mixed organic-inorganic particles. Salting-out and salting-in effects result from organic-inorganic interactions and are used to improve industrial separation processes. In the atmosphere, they may influence the aerosol phases. Liquid-liquid phase separations into a mainly polar (aqueous) and a less polar organic phase may considerably influence the gas/particle partitioning of semi-volatile substances compared to a single phase estimation. Moreover, the phases present in the aerosol define the reaction medium for heterogeneous and multiphase chemistry occurring in aerosol particles. A correct description of these phases is needed when gas- or cloud-phase reaction schemes are adapted to aerosols. Non-ideal thermodynamic behavior in mixtures is usually described by an expression for the excess Gibbs energy. We present the group-contribution model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients), which explicitly accounts for molecular interactions between solution constituents, both organic and inorganic, to calculate activities, chemical potentials and the total Gibbs energy of mixed systems. This model allows to compute vapor-liquid (VLE), liquid-liquid (LLE) and solid-liquid (SLE) equilibria within one framework. Focusing on atmospheric applications we considered eight different cations, five anions and a wide range of alcohols/polyols as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are very well represented up to high ionic strength. We show that the semiempirical middle-range parametrization of direct organic-inorganic interactions in alcohol-water-salt solutions enables accurate computations of liquid-liquid equilibria -- and phase diagrams in general.

Zuend, A.; Marcolli, C.; Luo, B.; Peter, T.

2008-12-01

35

ATR-FTIR characterization of organic functional groups and inorganic ions in ambient aerosols at a rural site  

NASA Astrophysics Data System (ADS)

An Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopic method was used to measure organic functional groups and inorganic ions at Tonto National Monument (TNM), an Interagency Monitoring of Protected Visual Environments (IMPROVE) sampling site in a rural area near Phoenix, Arizona. Functional groups and ions from common aerosol compound classes such as aliphatic and aromatic CH, methylene, methyl, aldehydes/ketones, carboxylic acids, ammonium sulfate and nitrate as well as functional groups from difficult to measure compound classes such as esters/lactones, acid anhydrides, carbohydrate hydroxyl and ethers, amino acids, and amines were quantified. On average, ˜33% of the PM 1.0 mass was composed of organic aerosol. The average (standard deviation) composition of the organic aerosol at TNM was 34% (6%) biogenic functional groups, 21% (5%) oxygenated functional groups, 28% (7%) aliphatic hydrocarbon functional groups (aliphatic CH, methylene and methyl) and 17% (1%) aromatic hydrocarbon functional groups. Compositional analysis, functional group correlations, and back trajectories were used to identify three types of events with source signatures: primary biogenic-influenced, urban-influenced, and regional background. The biogenic-influenced event had high concentrations of amino acids and carbohydrate hydroxyl and ether, as well as aliphatic CH and aromatic CH functional groups and qualitatively high levels of silicate. The urban-influenced events had back trajectories traveling directly from the Phoenix area and high concentrations of hydrocarbons, oxygenated functional groups, and inorganic ions. This aerosol characterization suggests that both primary emissions in Phoenix and secondary formation of aerosols from Phoenix emissions had a major impact on the aerosol composition and concentration at TNM. The regional background source had low concentrations of all functional groups, but had higher concentrations of biogenic functional groups than the urban source.

Coury, Charity; Dillner, Ann M.

36

Improvement and further development in CESM/CAM5: gas-phase chemistry and inorganic aerosol treatments  

NASA Astrophysics Data System (ADS)

Gas-phase chemistry and subsequent gas-to-particle conversion processes such as new particle formation, condensation, and thermodynamic partitioning have large impacts on air quality, climate, and public health through influencing the amounts and distributions of gaseous precursors and secondary aerosols. Their roles in global air quality and climate are examined in this work using the Community Earth System Model version 1.0.5 (CESM1.0.5) with the Community Atmosphere Model version 5.1 (CAM5.1) (referred to as CESM1.0.5/CAM5.1). CAM5.1 includes a simple chemistry that is coupled with a 7-mode prognostic Modal Aerosol Model (MAM7). MAM7 includes classical homogenous nucleation (binary and ternary) and activation nucleation (empirical first-order power law) parameterizations, and a highly simplified inorganic aerosol thermodynamics treatment that only simulates particulate-phase sulfate and ammonium. In this work, a new gas-phase chemistry mechanism based on the 2005 Carbon Bond Mechanism for Global Extension (CB05_GE) and several advanced inorganic aerosol treatments for condensation of volatile species, ion-mediated nucleation (IMN), and explicit inorganic aerosol thermodynamics for sulfate, ammonium, nitrate, sodium, and chloride have been incorporated into CESM/CAM5.1-MAM7. Compared to the simple gas-phase chemistry, CB05_GE can predict many more gaseous species, and thus could improve model performance for PM2.5, PM10, PM components, and some PM gaseous precursors such as SO2 and NH3 in several regions as well as aerosol optical depth (AOD) and cloud properties (e.g., cloud fraction (CF), cloud droplet number concentration (CDNC), and shortwave cloud forcing, SWCF) on the global scale. The modified condensation and aqueous-phase chemistry could further improve the prediction of additional variables such as HNO3, NO2, and O3 in some regions, and new particle formation rate (J) and AOD on the global scale. IMN can improve the prediction of secondary PM2.5 components, PM2.5, and PM10 over Europe as well as AOD and CDNC on the global scale. The explicit inorganic aerosol thermodynamics using the ISORROPIA II model improves the prediction of all major PM2.5 components and their gaseous precursors in some regions as well as downwelling shortwave radiation, SWCF, and cloud condensation nuclei at a supersaturation of 0.5% on the global scale. For simulations of 2001-2005 with all the modified and new treatments, the improved model predicts that on global average, SWCF increases by 2.7 W m-2, reducing the normalized mean bias (NMB) of SWCF from -5.4 to 1.2%. Uncertainties in emissions can largely explain the inaccurate prediction of precursor gases (e.g., SO2, NH3, and NO) and primary aerosols (e.g., black carbon and primary organic matter). Additional factors leading to the discrepancies between model predictions and observations include assumptions associated with equilibrium partitioning for fine particles assumed in ISORROPIA II, irreversible gas/particle mass transfer treatment for coarse particles, uncertainties in model treatments such as dust emissions, secondary organic aerosol formation, multi-phase chemistry, cloud microphysics, aerosol-cloud interaction, dry and wet deposition, and model parameters (e.g., accommodation coefficients and prefactors of the nucleation power law) as well as uncertainties in model configuration such as the use of a coarse-grid resolution.

He, J.; Zhang, Y.

2014-09-01

37

Understanding Anthropogenic and Biogenic Primary and Secondary Aerosol Mixtures  

NASA Astrophysics Data System (ADS)

Atmospheric organic matter can constitute 20-70% of the total fine aerosol mass, yet much of its chemical composition is not well understood nor are the mechanisms via which these compounds form. Continental organic aerosol can be directly emitted as primary aerosol from combustion sources or formed in the atmosphere via secondary process with both biogenic and anthropogenic hydrocarbon precursors. In urban air masses, the mixture of anthropogenic primary emissions and secondary organic aerosol (SOA) is ubiquitous. Changes due to the mixing of the different organic chemical compositions can affect the oxidation state and ageing properties of particulates. Hence the change in state can consequently impact air quality, public health and regional climate. The mixing state and the affinity of primary emissions with SOA not well understood: very little is known about the properties of these mixtures. In this a study, SOA formed in the Carnegie Mellon University environmental smog chamber is mixed with diesel exhaust and motor oil aerosol. The objective is to combine two aerosol classes in an external mixture and to then watch the dynamics as well as total mass balance as the mixtures come to equilibrium, possibly forming a single, internal mixture. The SOA is formed from monoterpene and sesquiterpene precursors, specifically ?-pinene and ?- caryophyllene SOA formed via dark ozonlysis. Primary aerosol is injected into the chamber once the biogenic nucleation and growth has completed and the mixture is allowed to age for three to four hours. A suite of instruments characterize the changes in size, volatility, and chemical composition of the aerosol mixtures. Scanning Mobility Particle Sizers record changes in the size distribution before and after mixing. An Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer measures the change in mass spectra and the composition of separate size modes both before and after the mixing event, and a thermodenuder is used to characterize changes in mixed aerosol volatility.

Asa-Awuku, A.; Miracola, M.; Lee, B. D.; Kroll, J.; Pandis, S.; Robinson, A.; Donahue, N.

2008-12-01

38

Formation of halogen-induced secondary organic aerosol (XOA)  

NASA Astrophysics Data System (ADS)

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 ?-pinene and 0.0004 for bromine with ?-pinene. This work was funded by German Research Foundation (DFG) under grants HE 5214/5-1 and ZE792/5-2. References: Cai, X., and Griffin, R. J.: Secondary aerosol formation from the oxidation of biogenic hydrocarbons by chlorine atoms, J. Geophys. Res., 111, D14206/14201-D14206/14214, 2006. Ofner, J. Balzer, N., Buxmann, J., Grothe, H., Schmitt-Kopplin, Ph., Platt, U., and Zetzsch, C., Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms, Atmos. Chem. Phys. Discuss. 12, 2975-3017, 2012.

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

2013-04-01

39

Secondary Ion Mass Spectrometry of Environmental Aerosols  

Microsoft Academic Search

Atmospheric particles influence many aspects of climate, air quality and human health. Understanding the composition, chemistry and behavior of atmospheric aerosols is a key remaining challenge in improving climate models. Furthermore, particles may be traced back to a particular source based on composition, stable isotope ratios, or the presence of particular surface chemistries. Finally, the characterization of atmospheric particles in

Daniel J. Gaspar; John B. Cliff

2010-01-01

40

High secondary aerosol contribution to particulate pollution during haze events in China.  

PubMed

Rapid industrialization and urbanization in developing countries has led to an increase in air pollution, along a similar trajectory to that previously experienced by the developed nations. In China, particulate pollution is a serious environmental problem that is influencing air quality, regional and global climates, and human health. In response to the extremely severe and persistent haze pollution experienced by about 800 million people during the first quarter of 2013 (refs 4, 5), the Chinese State Council announced its aim to reduce concentrations of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometres) by up to 25 per cent relative to 2012 levels by 2017 (ref. 6). Such efforts however require elucidation of the factors governing the abundance and composition of PM2.5, which remain poorly constrained in China. Here we combine a comprehensive set of novel and state-of-the-art offline analytical approaches and statistical techniques to investigate the chemical nature and sources of particulate matter at urban locations in Beijing, Shanghai, Guangzhou and Xi'an during January 2013. We find that the severe haze pollution event was driven to a large extent by secondary aerosol formation, which contributed 30-77 per cent and 44-71 per cent (average for all four cities) of PM2.5 and of organic aerosol, respectively. On average, the contribution of secondary organic aerosol (SOA) and secondary inorganic aerosol (SIA) are found to be of similar importance (SOA/SIA ratios range from 0.6 to 1.4). Our results suggest that, in addition to mitigating primary particulate emissions, reducing the emissions of secondary aerosol precursors from, for example, fossil fuel combustion and biomass burning is likely to be important for controlling China's PM2.5 levels and for reducing the environmental, economic and health impacts resulting from particulate pollution. PMID:25231863

Huang, Ru-Jin; Zhang, Yanlin; Bozzetti, Carlo; Ho, Kin-Fai; Cao, Jun-Ji; Han, Yongming; Daellenbach, Kaspar R; Slowik, Jay G; Platt, Stephen M; Canonaco, Francesco; Zotter, Peter; Wolf, Robert; Pieber, Simone M; Bruns, Emily A; Crippa, Monica; Ciarelli, Giancarlo; Piazzalunga, Andrea; Schwikowski, Margit; Abbaszade, Gülcin; Schnelle-Kreis, Jürgen; Zimmermann, Ralf; An, Zhisheng; Szidat, Sönke; Baltensperger, Urs; El Haddad, Imad; Prévôt, André S H

2014-10-01

41

High secondary aerosol contribution to particulate pollution during haze events in China  

NASA Astrophysics Data System (ADS)

Rapid industrialization and urbanization in developing countries has led to an increase in air pollution, along a similar trajectory to that previously experienced by the developed nations. In China, particulate pollution is a serious environmental problem that is influencing air quality, regional and global climates, and human health. In response to the extremely severe and persistent haze pollution experienced by about 800 million people during the first quarter of 2013 (refs 4, 5), the Chinese State Council announced its aim to reduce concentrations of PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 micrometres) by up to 25 per cent relative to 2012 levels by 2017 (ref. 6). Such efforts however require elucidation of the factors governing the abundance and composition of PM2.5, which remain poorly constrained in China. Here we combine a comprehensive set of novel and state-of-the-art offline analytical approaches and statistical techniques to investigate the chemical nature and sources of particulate matter at urban locations in Beijing, Shanghai, Guangzhou and Xi'an during January 2013. We find that the severe haze pollution event was driven to a large extent by secondary aerosol formation, which contributed 30-77 per cent and 44-71 per cent (average for all four cities) of PM2.5 and of organic aerosol, respectively. On average, the contribution of secondary organic aerosol (SOA) and secondary inorganic aerosol (SIA) are found to be of similar importance (SOA/SIA ratios range from 0.6 to 1.4). Our results suggest that, in addition to mitigating primary particulate emissions, reducing the emissions of secondary aerosol precursors from, for example, fossil fuel combustion and biomass burning is likely to be important for controlling China's PM2.5 levels and for reducing the environmental, economic and health impacts resulting from particulate pollution.

Huang, Ru-Jin; Zhang, Yanlin; Bozzetti, Carlo; Ho, Kin-Fai; Cao, Jun-Ji; Han, Yongming; Daellenbach, Kaspar R.; Slowik, Jay G.; Platt, Stephen M.; Canonaco, Francesco; Zotter, Peter; Wolf, Robert; Pieber, Simone M.; Bruns, Emily A.; Crippa, Monica; Ciarelli, Giancarlo; Piazzalunga, Andrea; Schwikowski, Margit; Abbaszade, Gülcin; Schnelle-Kreis, Jürgen; Zimmermann, Ralf; An, Zhisheng; Szidat, Sönke; Baltensperger, Urs; Haddad, Imad El; Prévôt, André S. H.

2014-10-01

42

Formation of secondary aerosols over Europe: comparison of two gas-phase chemical mechanisms  

NASA Astrophysics Data System (ADS)

The impact of two recent gas-phase chemical kinetic mechanisms (CB05 and RACM2) on the formation of secondary inorganic and organic aerosols is compared for simulations of PM2.5 over Europe between 15 July and 15 August 2001. The host chemistry transport model is Polair3D of the Polyphemus air-quality platform. Particulate matter is modeled with a sectional aerosol model (SIREAM), which is coupled to the thermodynamic model ISORROPIA for inorganic species and to a module (MAEC) that treats both hydrophobic and hydrophilic species for secondary organic aerosol (SOA). Modifications are made to the gas-phase chemical mechanisms to handle the formation of SOA. In order to isolate the effect of the original chemical mechanisms on PM formation, the addition of reactions and chemical species needed for SOA formation was harmonized to the extent possible between the two gas-phase chemical mechanisms. Model performance is satisfactory with both mechanisms for speciated PM2.5. The monthly-mean difference of the concentration of PM2.5 is less than 1 ?g m-3 (6%) over the entire domain. Secondary chemical components of PM2.5 include sulfate, nitrate, ammonium and organic aerosols, and the chemical composition of PM2.5 is not significantly different between the two mechanisms. Monthly-mean concentrations of inorganic aerosol are higher with RACM2 than with CB05 (+16% for sulfate, +11% for nitrate, and +10% for ammonium), whereas the concentrations of organic aerosols are slightly higher with CB05 than with RACM2 (+22% for anthropogenic SOA and +1% for biogenic SOA). Differences in the inorganic and organic aerosols result primarily from differences in oxidant concentrations (OH, O3 and NO3). Nitrate formation tends to be HNO3-limited over land and differences in the concentrations of nitrate are due to differences in concentration of HNO3. Differences in aerosols formed from aromatic SVOC are due to different aromatic oxidation between CB05 and RACM2. The aromatic oxidation in CB05 leads to more cresol formation, which then leads to more SOA. Differences in the aromatic aerosols would be significantly reduced with the recent CB05-TU mechanism for toluene oxidation. Differences in the biogenic aerosols are due to different oxidant concentrations (monoterpenes) and different particulate organic mass concentrations affecting the gas-particle partitioning of SOA (isoprene). These results show that the formulation of a gas-phase chemical kinetic mechanism for ozone can have significant direct (e.g., cresol formation) and indirect (e.g., oxidant levels) effects on PM formation. Furthermore, the incorporation of SOA into an existing gas-phase chemical kinetic mechanism requires the addition of reactions and product species, which should be conducted carefully to preserve the original mechanism design and reflect current knowledge of SOA formation processes (e.g., NOx dependence of some SOA yields). The development of chemical kinetic mechanisms, which offer sufficient detail for both oxidant and SOA formation is recommended.

Kim, Y.; Sartelet, K.; Seigneur, C.

2011-01-01

43

Secondary organic aerosol from photooxidation of polycyclic aromatic hydrocarbons.  

PubMed

Secondary organic aerosol (SOA) formation from the photooxidation of five polycyclic aromatic hydrocarbons (PAHs, naphthalene, 1- and 2-methylnaphthalene, acenaphthylene, and acenaphthene) was investigated in a 9-m(3) chamber in the presence of nitrogen oxides and the absence of seed aerosols. Aerosol size distributions and PAH decay were monitored by a scanning mobility particle sizer and a gas chromatograph with a flame ionization detector. Over a wide range of conditions, the aerosol yields for the investigated PAHs were observed to be in the range of 2-22%. The observed evolution of aerosol and PAH decay indicate that light and oxidant sources influence the time required to form aerosol and the required threshold reacted concentration of the PAHs. The SOA yields also were related to this induction period and the hydroxyl radical concentrations, particularly for smaller aerosol loadings (

Shakya, Kabindra M; Griffin, Robert J

2010-11-01

44

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...

45

Effect of Hydrophobic Primary Organic Aerosols on Secondary Organic Aerosol Formation from Ozonolysis of ?-Pinene  

SciTech Connect

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 ?-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.

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

46

A Phase Equilibrium Model for Atmospheric Aerosols Containing Inorganic Electrolytes and Dicarboxylic Acids (UHAERO)  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols contain a significant fraction of organic compounds. While a variety of thermodynamic models have been developed to predict inorganic gas-aerosol equilibrium, the prediction of phase equilibrium for mixed inorganic/organic aerosols has gathered much less attention. Presented here is a phase equilibrium model for atmospheric aerosols containing inorganic electrolytes and dicarboxylic acids, including oxalic, malonic, succinic, glutaric, maleic, and malic acids. The computational framework of UHAERO is based on minimization of the Gibbs free energy using a primal-dual method, coupled to a Newton iteration. The water update and deliquescence properties of aqueous solutions of dicarboxylic acids, and their mixtures with salts, are treated using a hybrid thermodynamic approach, namely the CSB model, in which existing models of inorganic (electrolyte) multicomponent solutions and water/organic mixtures are combined in a self consistent way. The model computes deliquescence behavior without any a priori specification of the relative humidities of deliquescence. Detailed phase diagrams of the sulfate/nitrate/ammonium/dicarboxylic acid/water system are presented as a function of relative humidity at 298.15K over the complete space of composition.

Martynenko, A. V.; Amundson, N.; Caboussat, A.; He, J.; Seinfeld, J. H.

2006-12-01

47

Characterization of Size-Differentiated Inorganic Composition of Aerosols in Mexico City (CU)  

NASA Astrophysics Data System (ADS)

Aerosol size distributions for the major ionic species: sulfate, nitrate, ammonium and potassium were determined at one sampling site (CU), located in the southwest of Mexico City (19° N, 99° W) from October, 2000 through August, 2001 with a Micro Orifice Uniform Deposit Impactor (MOUDI). Based on this analysis, sulfate and ammonium, which were correlated, were major features of the size distributions. Inorganic PM occurred mainly in one submicrometer mode, 0.32 ?m. This peak of concentration is the result of condensation of secondary aerosol components from the gas phase. During the rainy season (April, June), the peak of concentration was shifted to the droplet mode (0.56 ?m size range) as a result of heterogeneous, aqueous-phase reactions. In one case (August) both peaks were present simultaneously. Overall, ion balances were achieved with a small deficiency of cations, except for the cases April and June, where a significant amount of sulfate (2-3 times higher than that measured from the rest of the months) was present as a result of moderate activity of the neighboring volcano, Popocatepetl, as well as favoring conditions to produce sulfate (humid conditions). Based on the analysis of the ammonia/sulfate molar ratios for April and June, the ammonia concentration was not enough to fully neutralize the sulfate concentration. The predominant compounds in the condensation and droplet modes, i.e., 0.32 ?m and 0.56 ?m size ranges, during April and June were ammonium bisulfate and letovicite (or a solution of the corresponding ions), respectively. This acidic atmosphere (where the NH4/H2SO4 molar ratio is in the 0.5 to 1.5 range) is important in possible health effects of inhaled particles.

Moya, M.; Castro, T.; Zepeda, M.; Baez, A.

2002-12-01

48

The impact of long-range transport on secondary aerosol in Northeast Asia  

NASA Astrophysics Data System (ADS)

Long-range transport air pollution is an important issue in Northeast Asia. Large amounts of anthropogenic emissions of SO2 and NOx aggravate air pollution in the region. Most of the emissions come from the industrialized regions along the East China coast. China and Korea are changing their air quality standards for particle pollutant from PM10 to PM2.5 in 2012 and 2015, respectively. According to many previous studies, the long-rang transport of particle matter contributes to Korean air pollution problems, but there are many uncertainties regarding the impact of long range transport. Secondary inorganic aerosols (sulfate, nitrate and ammonium) are dominant ionic contributors to PM2.5. Especially high relative contributions of secondary aerosol appear under westerly wind cases at Korea. The secondary aerosols are produced by converting from SO2 and NOx during the long-range transport, but the contribution varies dramatically depending on season and wind pattern. So far, sulfate is the primary contributor to PM2.5, but nitrate levels are increasing because that NOx emissions in China are increasing dramatically since 2000 due to the growth in power, industry, and transport, while SO2 emissions are trending downward since 2005. We will present chemical characteristics of PM2.5 by westerly long-range transport focused on secondary aerosol, tracking their transport pattern, and production pathway in order to better understand regional air quality modeling of the long-range transport. This study will be performed based on the international study, MICS-Asia phase III, initiated with many researchers. Results using CMAQ with the modeling domain covering Northeast and Southeast China, Korea, and Japan with 15km resolution will be discussed.

Kim, Y.; Carmichael, G. R.; Woo, J.; Zhang, Q.

2013-12-01

49

Effects of mineral dust on the semivolatile inorganic aerosol components in a polluted Megacity  

NASA Astrophysics Data System (ADS)

Aerosols play a significant role in the atmosphere having adverse impacts on human health and directly affecting air quality, visibility and climate change. One of the most challenging tasks for models is the prediction of the partitioning of the semivolatile inorganic aerosol components (ammonia, nitric acid, hydrochloric acid, etc) between the gas and particulate phases. Moreover, the effects of mineral aerosols in the atmosphere remain largely uncertain. As a result, most current models have serious difficulties in reproducing the observed particulate nitrate and chloride concentrations. The improved aerosol thermodynamic model ISORROPIA II (Fountoukis and Nenes, 2007) simulating explicitly the chemistry of Ca, Mg, and K salts has been linked to the regional chemical transport model PMCAMx (Gaydos et al., 2007). PMCAMx also includes the CMU inorganic aerosol growth module (Gaydos et al., 2003; Koo et al., 2003a) and the VSRM aqueous-phase chemistry module (Fahey and Pandis, 2001). The hybrid approach (Koo et al., 2003b) for modeling aerosol dynamics is applied in order to accurately simulate the inorganic components in the coarse mode. This approach assumes that the smallest particles are in equilibrium, while the condensation/evaporation equation is solved for the larger ones. PMCAMx is applied to the Mexico City Metropolitan Area (MCMA). The emission inventory has been improved and now includes more accurate dust and NaCl emissions. The April 2003 (MCMA Campaign) and the March 2006 (MILAGRO campaign) datasets are used to evaluate the inorganic aerosol module of PMCAMx in order to test our understanding of inorganic aerosol. The results from the new modeling framework are also compared with the results from the previous version of PMCAMx in order to investigate the influence of each of the added features to the formation of the semivolatile inorganic components. References Fountoukis, C. and Nenes, A., (2007). ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K+-Ca2+-Mg2+-NH4+-Na+-SO42- -NO3- -Cl- -H2O aerosols. Atmos. Chem. Phys., 7, 4639-4659. Gaydos, T., Pinder, R., Koo, B., Fahey, ?., Yarwood, G., and Pandis, S. N., (2007). Development and application of a three-dimensional Chemical Transport Model, PMCAMx. Atmospheric Environment, in press. Gaydos, T., Koo, B., and Pandis, S. N., (2003). Development and application of an efficient moving sectional approach for the solution of the atmospheric aerosol condensation/evaporation equations. Atmospheric Environment, 37, 3303-3316. Koo, B., Pandis S. N., and Ansari, A. (2003a). Integrated approaches to modeling the organic and inorganic atmospheric aerosol components. Atmospheric Environment, 37, 4757-4768. Fahey, K. and Pandis, S. N., (2001). Optimizing model performance: variable size resolution in cloud chemistry modeling. Atmospheric Environment 35, 4471-4478. Koo, B., Gaydos, T.M., Pandis, S.N., (2003b). Evaluation of the equilibrium, hybrid, and dynamic aerosol modeling approaches. Aerosol Science and Technology 37, 53-64

Karydis, V. A.; Tsimpidi, A. P.; Fountoukis, C.; Nenes, A.; Zavala, M.; Lei, W.; Molina, L. T.; Pandis, S. N.

2009-04-01

50

Indoor and outdoor concentrations of inorganic acidic aerosols and gases  

SciTech Connect

Annular denuder-filter pack sampling systems were used to make indoor and outdoor measurements of aerosol strong H{sup +}, SO{sub 4}{sup 2{minus}}, NH{sub 4}{sup +}, NO{sub 3}{sup {minus}} and NO{sub 2}{sup {minus}}, and the gaseous pollutants SO{sub 2}, HNO{sub 3}, HONO and NH{sub 3} during summer and winter periods in Boston, Massachusetts. Outdoor levels of SO{sub 2}, HNO{sub 3}, H{sup +} and SO{sub 4}{sup 2{minus}} exceeded their indoor concentrations during both seasons. Winter indoor/outdoor ratios were lower than during the summer, probably due to lower air exchange rates during the winter period. During both monitoring periods, indoor/outdoor ratios of aerosol strong H{sub +} were 40-50% of the indoor/outdoor SO{sub 4}{sup 2{minus}} ratio. Since aerosol strong acidity is typically associated with SO{sub 4}{sup 2{minus}}, this finding is indicative of neutralization of the acidic aerosol by the higher indoor NH{sub 3} levels. Geometric mean indoor/outdoor NH{sub 3} ratios of 3.5 and 23 respectively were measured for the summer and winter sampling periods. For HONO, NH{sub 3}, NH{sub 4}{sup +} and NO{sub 2}{sup {minus}}, indoor concentrations were significantly higher than ambient levels. Indoor levels of NO{sub 3}{sup {minus}} were slightly less than outdoor concentrations.

Brauer, M.; Koutrakis, P.; Keeler, G.J.; Spengler, J.D. (Harvard Univ., Boston, MA (USA))

1991-02-01

51

Thermodynamic Modeling of Organic-Inorganic Aerosols with the Group-Contribution Model AIOMFAC  

NASA Astrophysics Data System (ADS)

Liquid aerosol particles are - from a physicochemical viewpoint - mixtures of inorganic salts, acids, water and a large variety of organic compounds (Rogge et al., 1993; Zhang et al., 2007). Molecular interactions between these aerosol components lead to deviations from ideal thermodynamic behavior. Strong non-ideality between organics and dissolved ions may influence the aerosol phases at equilibrium by means of liquid-liquid phase separations into a mainly polar (aqueous) and a less polar (organic) phase. A number of activity models exists to successfully describe the thermodynamic equilibrium of aqueous electrolyte solutions. However, the large number of different, often multi-functional, organic compounds in mixed organic-inorganic particles is a challenging problem for the development of thermodynamic models. The group-contribution concept as introduced in the UNIFAC model by Fredenslund et al. (1975), is a practical method to handle this difficulty and to add a certain predictability for unknown organic substances. We present the group-contribution model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients), which explicitly accounts for molecular interactions between solution constituents, both organic and inorganic, to calculate activities, chemical potentials and the total Gibbs energy of mixed systems (Zuend et al., 2008). This model enables the computation of vapor-liquid (VLE), liquid-liquid (LLE) and solid-liquid (SLE) equilibria within one framework. Focusing on atmospheric applications we considered eight different cations, five anions and a wide range of alcohols/polyols as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are very well represented up to high ionic strength. We show that the semi-empirical middle-range parametrization of direct organic-inorganic interactions in alcohol-water-salt solutions enables accurate computations of vapor-liquid and liquid-liquid equilibria. References Fredenslund, A., Jones, R. L., and Prausnitz, J. M.: Group-Contribution Estimation of Activity Coefficients in Nonideal Liquid Mixtures, AIChE J., 21, 1086-1099, 1975. Rogge, W. F., Mazurek, M. A., Hildemann, L. M., Cass, G. R., and Simoneit, B. R. T.: Quantification of Urban Organic Aerosols at a Molecular Level: Identification, Abundance and Seasonal Variation, Atmos. Environ., 27, 1309-1330, 1993. Zhang, Q. et al.: Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically influenced Northern Hemisphere midlatitudes, Geophys. Res. Lett., 34, L13 801, 2007. Zuend, A., Marcolli, C., Luo, B. P., and Peter, T.: A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients, Atmos. Chem. Phys., 8, 4559-4593, 2008.

Zuend, A.; Marcolli, C.; Luo, B. P.; Peter, T.

2009-04-01

52

Aerosol composition and sources during the Chinese Spring Festival: fireworks, secondary aerosol, and holiday effects  

NASA Astrophysics Data System (ADS)

Aerosol particles were characterized by an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) along with various collocated instruments in Beijing, China to investigate the aerosol composition and sources during the Chinese Spring Festival, 2013. Three fireworks (FW) events exerting significant and short-term impacts on fine particles (PM2.5) were observed on the days of Lunar New Year, Lunar Fifth Day, and Lantern Festival. The FW showed major impacts on non-refractory potassium, chloride, sulfate, and organics in PM1, of which the FW organics appeared to be mainly secondary with its mass spectrum resembling to that of secondary organic aerosol (SOA). Pollution events (PEs) and clean periods (CPs) alternated routinely throughout the study. Secondary particulate matter (SPM = SOA + sulfate + nitrate + ammonium) dominated PM1 accounting for 63-82% during the nine PEs observed. The elevated contributions of secondary species during PEs resulted in a higher mass extinction efficiency of PM1 (6.4 m2 g-1) than that during CPs (4.4 m2 g-1). The Chinese Spring Festival also provides a unique opportunity to study the impacts of reduced anthropogenic emissions on aerosol chemistry in the city. The primary species showed ubiquitous reductions during the holiday period with the largest reduction for cooking OA (69%), nitrogen monoxide (54%), and coal combustion OA (28%). The secondary sulfate, however, remained minor change, and the SOA and the total PM2.5 even slightly increased. These results have significant implications that controlling local primary source emissions, e.g., cooking and traffic activities, might have limited effects on improving air quality during PEs when SPM that is formed over regional scales dominates aerosol particle composition.

Jiang, Q.; Sun, Y. L.; Wang, Z.; Yin, Y.

2014-08-01

53

Phases and Phase Changes of Mixed Organic/Inorganic Model Systems of Tropospheric Aerosols  

NASA Astrophysics Data System (ADS)

Knowledge of the physical state of tropospheric aerosols is important for an adequate description of cloud formation, heterogeneous and multiphase chemistry, and the aerosol's radiative properties. We will present and discuss laboratory experiments on bulk aerosol model mixtures and micron-sized particles consisting of polyols, polyethylene glycol or dicarboxylic acids mixed with ammonium sulfate. Depending on the exact composition and relative humidity, these mixtures form liquid-one-phase or two-phase systems plus additional solid phases. Whilst the organic matter in ambient aerosols is expected to be predominantly present in the form of liquid or amorphous phases, the inorganic salts may still undergo deliquescence and efflorescence as a function of relative humidity. Moreover, they may induce phase separations into a predominantly organic and an inorganic aqueous phase. In the absence of solid phases, the water uptake and release of the investigated micron-sized particles was usually well described by the Zdanovskii-Stokes-Robinson (ZSR) approach. However, this model became inaccurate when solid phases were present. Moreover, it is not able to account for liquid-liquid phase separations due to the salting-out effects of the investigated inorganic salts. While most organics participate in liquid phases some organic substances are abundant enough in the particles to form crystalline solids that might act as ice nuclei. We show that this is the case for oxalic acid.

Marcolli, C.; Krieger, U. K.; Zardini, A. A.; Zobrist, B.; Zuend, A.; Luo, B. P.; Peter, T.

2006-12-01

54

Aerosol Precursor Emissions, Secondary Aerosol Production, and Climate-Forcing Gas Exchange in the Midwestern United States  

NASA Astrophysics Data System (ADS)

Aerosol precursors in the Midwest are generated from a myriad of sources including biogenic emissions of terpenes from the Ozarks region, anthropogenic emissions of volatile and semivolatile aliphatic and aromatic hydrocarbons from the St. Louis airshed, and agricultural emissions of ammonia (NH3), amines, and nitrogen oxides (NOx) from animal husbandry and cropping systems of the Midwest Corn Belt. The deciduous and coniferous forests of the Ozarks region are significant sources of isoprene, monoterpenes, and sesquiterpenes that are sensitive to rising CO2 levels and temperature and generate light-scattering, secondary organic aerosol (SOA). Application of nitrogen fertilizers stimulates emissions of ammonia (NH3), nitric oxide (NO), and nitrous oxide (N2O) from agricultural soils and crops. Nitric acid, generated through photooxidation of NO emissions from fossil fuel combustion in urban air and from soil emissions in agroecosystems, reacts rapidly with NH3 to generate light-scattering, secondary inorganic aerosol (SIA). The atmospheric lifetime of N2O is about 120 years, making the substance a potent greenhouse gas with a global warming potential of 290 for a time horizon of 20 years relative to CO2. Emissions of CO2, N2O, and SIA precursors from the Midwest Corn Belt and surrounding areas are likely to increase in the near future as pastureland and prairie is converted to grow corn and other biofuel crops to meet the demand for renewable fuels. Several large river systems transport nutrients from fertilized fields of the Midwest agroecosystem to the Gulf of Mexico where plankton growth is accelerated. Microbial decomposition of plankton detritus consumes oxygen and creates a hypoxic zone, which might be a significant source of N2O.The presentation will discuss gaps in our knowledge of the production of climate-forcing species in the Midwestern United States.

Doskey, P. V.

2009-12-01

55

Cloud condensation nucleus activation properties of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Organic aerosols in general and secondary organic aerosol (SOA) in particular are known to contribute significantly to the atmospheric population of cloud condensation nuclei (CCN). However, current knowledge is limited with respect to the nature of this contribution. This study presents a series of experiments wherein the potential for biogenically derived SOA to act as CCN is explored. Five compounds were studied: four monoterpenes (?-pinene, ?-pinene, limonene, and ?3-carene) and one terpenoid alcohol (terpinene-4-ol). In each case the aerosol formation was driven by the reaction of ozone with the biogenic precursor. The SOA produced in each experiment was allowed to age for several hours, during which CCN concentrations were periodically measured at four supersaturations: S = 0.27%, 0.32%, 0.54%, and 0.80%. The calculated relationships between particle dry diameter and critical supersaturation were found to fall in the range of previously reported data for single-component organic aerosols; of the systems studied, ?-pinene SOA was the least CCN active, while limonene SOA exhibited the strongest CCN activity. Interestingly, the inferred critical supersaturation of the SOA products was considerably more sensitive to particle diameter than was found in previous studies. Furthermore, the relationships between particle size and critical supersaturation for the monoterpene SOA shifted considerably over the course of the experiments, with the aerosol becoming less hygroscopic over time. These results are consistent with the progressive oligomerization of the SOA.

Vanreken, Timothy M.; Ng, Nga L.; Flagan, Richard C.; Seinfeld, John H.

2005-04-01

56

SECONDARY ORGANIC AEROSOL FORMATION FROM THE OXIDATION OF AROMATIC HYDROCARBONS IN THE PRESENCE OF DRY SUBMICRON AMMONIUM SULFATE AEROSOL  

EPA Science Inventory

A laboratory study was conducted to examine formation of secondary organic aerosols. A smog chamber system was developed for studying gas-aerosol interactions in a dynamic flow reactor. These experiments were conducted to investigate the fate of gas and aerosol phase compounds ...

57

Secondary organic aerosol formation from m -xylene, toluene, and benzene  

Microsoft Academic Search

Secondary organic aerosol (SOA) formation from the photooxidation of m-xylene, toluene, and benzene is in- vestigated in the Caltech environmental chambers. Exper- iments are performed under two limiting NOx conditions; under high-NOx conditions the peroxy radicals (RO2) react only with NO, while under low-NOx conditions they react only with HO2. For all three aromatics studied (m-xylene, toluene, and benzene), the

N. L. Ng; J. H. Kroll; A. W. H. Chan; P. S. Chhabra; R. C. Flagan; J. H. Seinfeld

2007-01-01

58

The role of long-range transport and domestic emissions in determining atmospheric secondary inorganic particle concentrations across the UK  

NASA Astrophysics Data System (ADS)

Surface concentrations of secondary inorganic particle components over the UK have been analysed for 2001-2010 using the EMEP4UK regional atmospheric chemistry transport model and evaluated against measurements. Gas/particle partitioning in the EMEP4UK model simulations used a bulk approach, which may lead to uncertainties in simulated secondary inorganic aerosol. However, model simulations were able to accurately represent both the long-term decadal surface concentrations of particle sulfate and nitrate and an episode in early 2003 of substantially elevated nitrate measured across the UK by the AGANet network. The latter was identified as consisting of three separate episodes, each of less than 1 month duration, in February, March and April. The primary cause of the elevated nitrate levels across the UK was meteorological: a persistent high-pressure system, whose varying location impacted the relative importance of transboundary versus domestic emissions. Whilst long-range transport dominated the elevated nitrate in February, in contrast it was domestic emissions that mainly contributed to the March episode, and for the April episode both domestic emissions and long-range transport contributed. A prolonged episode such as the one in early 2003 can have substantial impact on annual average concentrations. The episode led to annual concentration differences at the regional scale of similar magnitude to those driven by long-term changes in precursor emissions over the full decade investigated here. The results demonstrate that a substantial part of the UK, particularly the south and southeast, may be close to or exceeding annual mean limit values because of import of inorganic aerosol components from continental Europe under specific conditions. The results reinforce the importance of employing multiple year simulations in the assessment of emissions reduction scenarios on particulate matter concentrations and the need for international agreements to address the transboundary component of air pollution.

Vieno, M.; Heal, M. R.; Hallsworth, S.; Famulari, D.; Doherty, R. M.; Dore, A. J.; Tang, Y. S.; Braban, C. F.; Leaver, D.; Sutton, M. A.; Reis, S.

2014-08-01

59

Characterization of size-differentiated inorganic composition of aerosols in Mexico City  

Microsoft Academic Search

Size-differentiated atmospheric aerosol particles were collected during December 2000–October 2001 in Mexico City (19°N, 99°W) using a micro-orifice uniform deposit impactor. Sulfate and ammonium, which were correlated, were major features of the size distributions. The more predominant mode was at 0.32±0.1?m, aerodynamic diameter. This peak of concentration is likely the result of condensation of secondary aerosol components from the gas

Mireya Moya; Telma Castro; Monica Zepeda; Armando Baez

2003-01-01

60

STXM-NEXAFS Investigations of Amazonian Background Aerosols, Laboratory Secondary Organic Aerosols, and Fungal Spores  

NASA Astrophysics Data System (ADS)

We applied Scanning Transmission X-ray Microscopy—Near Edge X-ray Absorption Fine Structure (STXM-NEXAFS) analysis to investigate the morphology and chemical composition of aerosol samples from a pristine tropical environment, the Amazon Basin. The samples were collected in the Amazonian rainforest during the rainy season and can be regarded as a natural background aerosol. The aerosol was found to be dominated by Secondary Organic Aerosols (SOA) in the fine and Primary Biological Aerosol Particles (PBAP) in the coarse mode. Lab-generated SOA-samples (produced by the (photo)oxidation of isoprene and ?-pinene) and microtome slices of fungal spores were measured as reference samples. The aim of this study was to investigate the microphysical and -chemical properties of a tropical background aerosol and its internal mixing state. SOA particles are present as spherical droplet-like particles or as coatings on PBAP, and show a high density of functionalities in their NEXAFS spectra. Besides the typical NEXAFS signals for oxidized carbonaceous groups, such as carboxylate, a significant number of SOA particles unexpectedly exhibit a strong K signal. For PBAP the C-, N- and O-specific NEXAFS maps allow insights into the intracellular structure and chemical composition of fungal spores, which clearly dominate the coarse mode of the Amazonian samples. Furthermore, clusters of bioparticles could be identified. PBAP show a complex NEXAFS spectrum due to a high variety of differently functionalized biomolecules, with different spectra and element abundances for individual cell components.

Andreae, M. O.; Pöhlker, C.; Artaxo, P.; Gilles, M. K.; Kilcoyne, A. L.; Martin, S. T.; Moffet, R.; Pöschl, U.; Sinha, B.; Smith, M. L.; Wiedemann, K. T.

2010-12-01

61

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

E-print Network

Secondary organic aerosol formation from fossil fuel sources contribute majority of summertime organic aerosol formation from fossil fuel sources contribute majority of summertime organic mass is fossil fuel combustion from gasoline- and diesel- powered vehicles and other industrial activities (e

Silver, Whendee

62

Secondary organic aerosol formation through cloud processing of aromatic VOCs  

NASA Astrophysics Data System (ADS)

Field observations have shown substantial concentrations (20-5,500 ng L-1) of aromatic volatile organic compounds (VOC) in 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 laboratory conditions, in idealized solutions, benzene, toluene, ethylbenzene, and xylene (BTEX) degraded quickly in the aqueous phase. 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 rates decreased with increasing organic carbon content. Kinetic data derived from these experiments were used as input to a multiphase box model in order to evaluate the secondary organic aerosol (SOA) mass formation potential of cloud processing of BTEX. Model results will be presented that quantify the SOA amounts from these aqueous phase pathways. The efficiency of this multiphase SOA source will be compared to SOA yields from the same aromatics as treated in traditional SOA models that are restricted to gas phase oxidation and subsequent condensation on particles.

Herckes, P.; Hutchings, J. W.; Ervens, B.

2010-12-01

63

Formation of secondary organic aerosols through photooxidation of isoprene.  

PubMed

Detailed organic analysis of natural aerosols from the Amazonian rain forest showed considerable quantities of previously unobserved polar organic compounds, which were identified as a mixture of two diastereoisomeric 2-methyltetrols: 2-methylthreitol and 2-methylerythritol. These polyols, which have the isoprene skeleton, can be explained by OH radical-initiated photooxidation of isoprene. They have low vapor pressure, allowing them to condense onto preexisting particles. It is estimated that photooxidation of isoprene results in an annual global production of about 2 teragrams of the polyols, a substantial fraction of the Intergovernmental Panel on Climate Change estimate of between 8 and 40 teragrams per year of secondary organic aerosol from biogenic sources. PMID:14976309

Claeys, Magda; Graham, Bim; Vas, Gyorgy; Wang, Wu; Vermeylen, Reinhilde; Pashynska, Vlada; Cafmeyer, Jan; Guyon, Pascal; Andreae, Meinrat O; Artaxo, Paulo; Maenhaut, Willy

2004-02-20

64

A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients  

NASA Astrophysics Data System (ADS)

Tropospheric aerosols contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behaviour. By means of activity coefficients, non-ideal behaviour can be taken into account. We present here a thermodynamic model named AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate activity coefficients covering inorganic, organic, and organic-inorganic interactions in aqueous solutions over a wide concentration range. This model is based on the activity coefficient model LIFAC by Yan et al. (1999) that we modified and reparametrised to better describe atmospherically relevant conditions and mixture compositions. Focusing on atmospheric applications we considered H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42- as cations and anions and a wide range of alcohols/polyols composed of the functional groups CHn and OH as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are well represented up to high ionic strength. Most notably, a semi-empirical middle-range parametrisation of direct organic-inorganic interactions in alcohol + water + salt solutions strongly improves the agreement between experimental and modelled activity coefficients. At room temperature, this novel thermodynamic model offers the possibility to compute equilibrium relative humidities, gas/particle partitioning and liquid-liquid phase separations with high accuracy. In further studies, other organic functional groups will be introduced. The model framework is not restricted to specific ions or organic compounds and is therefore also applicable for other research topics.

Zuend, A.; Marcolli, C.; Luo, B. P.; Peter, Th.

2008-03-01

65

A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients  

NASA Astrophysics Data System (ADS)

Tropospheric aerosols contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behaviour. By means of activity coefficients, non-ideal behaviour can be taken into account. We present here a thermodynamic model named AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) that is able to calculate activity coefficients covering inorganic, organic, and organic-inorganic interactions in aqueous solutions over a wide concentration range. This model is based on the activity coefficient model LIFAC by Yan et al. (1999) that we modified and reparametrised to better describe atmospherically relevant conditions and mixture compositions. Focusing on atmospheric applications we considered H+, Li+, Na+, K+, NH+4, Mg2+, Ca2+, Cl-, Br-, NO-3, HSO-4, and SO2-4 as cations and anions and a wide range of alcohols/polyols composed of the functional groups CHn and OH as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are well represented up to high ionic strength. Most notably, a semi-empirical middle-range parametrisation of direct organic-inorganic interactions in alcohol+water+salt solutions strongly improves the agreement between experimental and modelled activity coefficients. At room temperature, this novel thermodynamic model offers the possibility to compute equilibrium relative humidities, gas/particle partitioning and liquid-liquid phase separations with high accuracy. In further studies, other organic functional groups will be introduced. The model framework is not restricted to specific ions or organic compounds and is therefore also applicable for other research topics.

Zuend, A.; Marcolli, C.; Luo, B. P.; Peter, T.

2008-08-01

66

MATHEMATICAL MODEL FOR GAS/PARTICLE PARTITIONING OF SECONDARY ORGANIC AEROSOLS. (R824970)  

EPA Science Inventory

A dynamic model is developed for gas-particle absorptive partitioning of semi-volatile organic aerosols. The model is applied to simulate a pair of m -xylene/NO x outdoor smog chamber experiments. In the presence of an inorganic seed aerosol a threshold ...

67

The activity of mixed organic /inorganic/water aerosols and the spacial distribution of individual substances resulting from their efflorescence  

NASA Astrophysics Data System (ADS)

Since chemical and radiative effects of atmospheric aerosols are size and phase related, they are strongly influenced by the ambient relative humidity (RH) due to water absorbing hygroscopic components, changing both particle diameter and wavelength dependent refractive indices. Therefore, the assessment of the net effect on chemistry and/or climate for a given atmospheric particle load will critically depend on the level of scientific understanding regarding the phase behaviour of complex organic/ inorganic aerosols. The influence of organic substances such as dicarboxylic acids on the deliquescence behaviour has been subject of numerous studies over the past years. In this work a number of different mixtures comprising ammonium sulphate (AS) and different dicarboxylic acids (glutaric acid, maleic acid, malonic acid, succinic acid, and oxalic acid) have been used in Raman scanning experiments to study the spacial distribution of substances in the crystalline aerosol formed from the efflorescence process of internally mixed ternary ammonium sulphate / dicarboxylic acid / water aerosols. The results give intriguing insights into the complexity of the behaviour of highly supersaturated ternary organic/inorganic solutions and reveal substantial differences in the spacial distributions of organic and inorganic crystalline substances resulting from the efflorescence of these originally internally mixed systems. The relevance of these findings for the interpretations of the complex, concentration dependent phase behaviour of organic/ inorganic aerosols will be discussed. Modelling the behaviour of these complex solution aerosols frequently involves calculations of interactions between individual ionic components. In order to quantify these impacts the ammonium salts for a number of dicarboxylic acids have been synthesised and their thermodynamic behaviour has been elucidated with the surface aerosol microscope (SAM) setup. The results have been used to test and validate critical parameters of the aerosol inorganics model (AIM). In this work we present activity measurements for aqueous aerosols containing these organic ammonium salts as well as a comparison of AIM model data and experimental results.

Treuel, Lennart; Graß, Stefan; Sandmann, Alice; Zellner, Reinhard

2010-05-01

68

Nonequilibrium atmospheric secondary organic aerosol formation and growth  

PubMed Central

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 ?-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 ?-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

Perraud, Veronique; 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

69

Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles  

NASA Astrophysics Data System (ADS)

This study presents a modeling framework based on laboratory data to describe the kinetics of glyoxal reactions that form secondary organic aerosol (SOA) in aqueous aerosol particles. Recent laboratory results on glyoxal reactions are reviewed and a consistent set of empirical reaction rate constants is derived that captures the kinetics of glyoxal hydration and subsequent reversible and irreversible reactions in aqueous inorganic and water-soluble organic aerosol seeds. Products of these processes include (a) oligomers, (b) nitrogen-containing products, (c) photochemical oxidation products with high molecular weight. These additional aqueous phase processes enhance the SOA formation rate in particles and yield two to three orders of magnitude more SOA than predicted based on reaction schemes for dilute aqueous phase (cloud) chemistry for the same conditions (liquid water content, particle size). The application of the new module including detailed chemical processes in a box model demonstrates that both the time scale to reach aqueous phase equilibria and the choice of rate constants of irreversible reactions have a pronounced effect on the predicted atmospheric relevance of SOA formation from glyoxal. During day time, a photochemical (most likely radical-initiated) process is the major SOA formation pathway forming ∼5 ?g m-3 SOA over 12 h (assuming a constant glyoxal mixing ratio of 300 ppt). During night time, reactions of nitrogen-containing compounds (ammonium, amines, amino acids) contribute most to the predicted SOA mass; however, the absolute predicted SOA masses are reduced by an order of magnitude as compared to day time production. The contribution of the ammonium reaction significantly increases in moderately acidic or neutral particles (5 < pH < 7). Glyoxal uptake into ammonium sulfate seed under dark conditions can be represented with a single reaction parameter keffupt that does not depend on aerosol loading or water content, which indicates a possibly catalytic role of aerosol water in SOA formation. However, the reversible nature of uptake under dark conditions is not captured by keffupt, and can be parameterized by an effective Henry's law constant including an equilibrium constant Kolig = 1000 (in ammonium sulfate solution). Such reversible glyoxal oligomerization contributes <1% to total predicted SOA masses at any time. Sensitivity tests reveal five parameters that strongly affect the predicted SOA mass from glyoxal: (1) time scales to reach equilibrium states (as opposed to assuming instantaneous equilibrium), (2) particle pH, (3) chemical composition of the bulk aerosol, (4) particle surface composition, and (5) particle liquid water content that is mostly determined by the amount and hygroscopicity of aerosol mass and to a lesser extent by the ambient relative humidity. Glyoxal serves as an example molecule, and the conclusions about SOA formation in aqueous particles can serve for comparative studies of other molecules that form SOA as the result of multiphase chemical processing in aerosol water. This SOA source is currently underrepresented in atmospheric models; if included it is likely to bring SOA predictions (mass and O/C ratio) into better agreement with field observations.

Ervens, B.; Volkamer, R.

2010-09-01

70

Absorption of Visible and Long-wave Radiation by Primary and Secondary Biogenic Aerosols  

Microsoft Academic Search

Field results for the 14C content of carbonaceous aerosols are presented that indicate significant biogenic sources of both primary and secondary aerosols in urban and regional environments. Samples collected in Mexico City and downwind of the urban area during the MILAGRO field study are compared with results reported previously in the literature indicating a significant amount of biogenic aerosols from

J. S. Gaffney; N. A. Marley

2008-01-01

71

A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra  

Microsoft Academic Search

Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 mum) mass. Secondary organic aerosol (SOA) is an important contributor to the OA and can be formed from biogenic and anthropogenic precursors. Here we present results from the characterization of SOA produced from the emissions of three

M. F. Heringa; P. F. Decarlo; R. Chirico; T. Tritscher; M. Clairotte; C. Mohr; M. Crippa; J. G. Slowik; L. Pfaffenberger; J. Dommen; E. Weingartner; A. S. H. Prévôt; U. Baltensperger

2011-01-01

72

Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model - Part I: Treatment of inorganic electrolytes and organic compounds in the condensed phase  

NASA Astrophysics Data System (ADS)

Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 1999; Kleeman et al., 1999) assumes that aerosol particles consist of an aqueous phase, containing inorganic electrolytes and soluble organic compounds, and a hydrophobic phase containing mainly primary hydrocarbon material. Thirty eight semi-volatile reaction products are grouped into ten surrogate species which partition between the gas phase and both phases in the aerosol. Activity coefficients of the organic compounds are calculated using UNIFAC. In a companion paper (Clegg et al., 2007) we examine the likely uncertainties in the vapour pressures of the semi-volatile compounds and their effects on partitioning over a range of atmospheric relative humidities. In this work a simulation for the South Coast Air Basin surrounding Los Angeles, using lower vapour pressures of the semi-volatile surrogate compounds consistent with estimated uncertainties in the boiling points on which they are based, yields a doubling of the predicted 24-h average secondary organic aerosol concentrations. The dependency of organic compound partitioning on the treatment of inorganic electrolytes in the air quality model, and the performance of this component of the model, are determined by analysing the results of a trajectory calculation using an extended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications are identified where substantial efficiency gains can be made, principally: the omission of dissociation of the organic acid surrogates; restriction of aerosol organic compounds to one of the two phases (aqueous or hydrophobic) where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organic compounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in the aqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobic phase) and are therefore almost invariant. The implications of the results for the development of aerosol models are discussed.

Clegg, S. L.; Kleeman, M. J.; Griffin, R. J.; Seinfeld, J. H.

2007-07-01

73

Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model - Part 1: Treatment of inorganic electrolytes and organic compounds in the condensed phase  

NASA Astrophysics Data System (ADS)

Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 2003; Kleeman et al., 1999) assumes that aerosol particles consist of an aqueous phase, containing inorganic electrolytes and soluble organic compounds, and a hydrophobic phase containing mainly primary hydrocarbon material. Thirty eight semi-volatile reaction products are grouped into ten surrogate species which partition between the gas phase and both phases in the aerosol. Activity coefficients of the organic compounds are calculated using UNIFAC. In a companion paper (Clegg et al., 2008) we examine the likely uncertainties in the vapour pressures of the semi-volatile compounds and their effects on partitioning over a range of atmospheric relative humidities. In this work a simulation for the South Coast Air Basin surrounding Los Angeles, using lower vapour pressures of the semi-volatile surrogate compounds consistent with estimated uncertainties in the boiling points on which they are based, yields a doubling of the predicted 24-h average secondary organic aerosol concentrations. The dependency of organic compound partitioning on the treatment of inorganic electrolytes in the air quality model, and the performance of this component of the model, are determined by analysing the results of a trajectory calculation using an extended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications are identified where substantial efficiency gains can be made, principally: the omission of dissociation of the organic acid surrogates; restriction of aerosol organic compounds to one of the two phases (aqueous or hydrophobic) where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organic compounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in the aqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobic phase) and are therefore almost invariant. The implications of the results for the development of aerosol models are discussed.

Clegg, S. L.; Kleeman, M. J.; Griffin, R. J.; Seinfeld, J. H.

2008-02-01

74

Characteristics of major secondary ions in typical polluted atmospheric aerosols during autumn in central Taiwan.  

PubMed

In autumn of 2008, the chemical characteristics of major secondary ionic aerosols at a suburban site in central Taiwan were measured during an annually occurring season of high pollution. The semicontinuous measurement system measured major soluble inorganic species, including NH(4)(+), NO(3)(-), and SO(4)(2-), in PM(10) with a 15 min resolution time. The atmospheric conditions, except for the influences of typhoons, were dominated by the local sea-land breeze with clear diurnal variations of meteorological parameters and air pollutant concentrations. To evaluate secondary aerosol formation at different ozone levels, daily ozone maximum concentration (O(3,daily max)) was used as an index of photochemical activity for dividing between the heavily polluted period (O(3,daily max) ?80 ppb) and the lightly polluted period (O(3,daily max)<80 ppb). The concentrations of PM(10), NO(3)(-), SO(4)(2-), NH(4)(+) and total major ions during the heavily polluted period were 1.6, 1.9, 2.4, 2.7 and 2.3 times the concentrations during the lightly polluted period, respectively. Results showed that the daily maximum concentrations of PM(10) occurred around midnight and the daily maximum ozone concentration occurred during daytime. The average concentration of SO(2) was higher during daytime, which could be explained by the transportation of coastal industry emissions to the sampling site. In contrast, the high concentration of NO(2) at night was due to the land breeze flow that transport inland urban air masses toward this site. The simulations of breeze circulations and transitions were reflected in transports and distributions of these pollutants. During heavily polluted periods, NO(3)(-) and NH(4)(+) showed a clear diurnal variations with lower concentrations after midday, possibly due to the thermal volatilization of NH(4)NO(3) during daytime and transport of inland urban plume at night. The diurnal variation of PM(10) showed the similar pattern to that of NO(3)(-) and NH(4)(+) aerosols. This indicated that the formatted secondary aerosols in the inland urban area could be transported to the coastal area by the weak land breeze and deteriorated the air quality in the coastal area at night. PMID:21320743

Fang, Guor-Cheng; Lin, Shih-Chieh; Chang, Shih-Yu; Lin, Chuan-Yao; Chou, Charles-C K; Wu, Yun-Jui; Chen, Yu-Chieh; Chen, Wei-Tzu; Wu, Tsai-Lin

2011-06-01

75

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

NASA Astrophysics Data System (ADS)

The formation of Secondary organic aerosol (SOA) was simulated with the Secondary ORGanic Aerosol Model (SORGAM) by a classical gas-particle partitioning concept, using the two-product model approach, which is widely used in chemical transport models. In this study, we extensively updated SORGAM including three major modifications: firstly, we derived temperature dependence functions of the SOA yields for aromatics and biogenic VOCs, based on recent chamber studies within a sophisticated mathematic optimization framework; secondly, we implemented the SOA formation pathways from photo oxidation (OH initiated) of isoprene; thirdly, we implemented the SOA formation channel from NO3-initiated oxidation of reactive biogenic hydrocarbons (isoprene and monoterpenes). The temperature dependence functions of the SOA yields were validated against available chamber experiments. Moreover, the whole updated SORGAM module was validated against ambient SOA observations represented by the summed oxygenated organic aerosol (OOA) concentrations abstracted from Aerosol Mass Spectrometer (AMS) measurements at a rural site near Rotterdam, the Netherlands, performed during the IMPACT campaign in May 2008. In this case, we embedded both the original and the updated SORGAM module into the EURopean Air pollution and Dispersion-Inverse Model (EURAD-IM), which showed general good agreements with the observed meteorological parameters and several secondary products such as O3, sulfate and nitrate. With the updated SORGAM module, the EURAD-IM model also captured the observed SOA concentrations reasonably well especially those during nighttime. In contrast, the EURAD-IM model before update underestimated the observations by a factor of up to 5. The large improvements of the modeled SOA concentrations by updated SORGAM were attributed to the mentioned three modifications. Embedding the temperature dependence functions of the SOA yields, including the new pathways from isoprene photo oxidations, and switching on the SOA formation from NO3 initiated biogenic VOCs oxidations contributed to this enhancement by 10%, 22% and 47%, respectively. However, the EURAD-IM model with updated SORGAM still clearly underestimated the afternoon SOA observations up to a factor of two. More work such as to improve the simulated OH concentrations under high VOCs and low NOx concentrations, further including the SOA formation from semi-volatile organic compounds, the correct aging process of aerosols, oligomerization process and the influence on the biogenic SOA by the anthropogenic SOA, are still required to fill the gap.

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

2013-03-01

76

Photochemical Aging of Secondary Organic Aerosol Particles Generated from the Oxidation of d-Limonene  

E-print Network

particles play an important role in controlling global climate and air quality.1-6 Studies have shownPhotochemical Aging of Secondary Organic Aerosol Particles Generated from the Oxidation of d; In Final Form: January 13, 2007 Secondary organic aerosol (SOA) particles are generated by reacting d

Nizkorodov, Sergey

77

Predicting secondary organic aerosol formation rates in southeast Texas  

NASA Astrophysics Data System (ADS)

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 (?-pinene, ?-pinene, sabinene, d-limonene, and ?3-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 (?SOA/?HC) 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 ?-pinene and ?-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.

Russell, Matthew; Allen, David T.

2005-04-01

78

Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.  

PubMed

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

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

79

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

80

Characterization of secondary aerosol and its extinction effects on visibility over the Pearl River Delta Region, China.  

PubMed

Aerosol samples collected from July 2007 to March 2008 were used to obtain major aerosol constituents in an urban location in the Pearl River Delta Region (PRD), China. The minimum organic carbon (OC)/elemental carbon (EC) ratio was used to calculate the primary and secondary organic carbon and the extinction effect of the secondary aerosol on visibility was estimated. As indicated in the analysis, the mass of secondary aerosol takes up 50% of the total mass of PM2.5; the OC/EC ratio is larger than 2 and there are significant characteristics of secondary aerosol generation; the levels of secondary OC are comparable with those of sulfate; and there is obvious enrichment of secondary aerosol on more polluted days. In a dry environment, the extinction weight is 59% for the secondary aerosol, while it is as high as 82% if the environment is highly humid (relative humidity [RH] = 95%). The hygroscopic growth of the aerosol can reduce visibility greatly; the secondary aerosol shares much larger quotas on more polluted days. For the Pearl River Delta (PRD), secondary aerosol and carbonaceous aerosol, especially secondary organic carbon (SOC), are a very acute problem; the study of the generating mechanism and sources for secondary aerosol is the key to the effort of controlling visibility in this region. The equation set forth in IMPROVE experiments can only be referenced but is not applicable to evaluate the extinction effect of individual aerosol components on visibility in the PRD region. PMID:24151676

Deng, Xuejiao; Wu, Dui; Yu, Jianzhen; Lau, Alexis K H; Li, Fei; Tan, Haobo; Yuan, Zibing; Ng, Wai Man; Deng, Tao; Wu, Cheng; Zhou, Xiuji

2013-09-01

81

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

NASA Astrophysics Data System (ADS)

The formation of Secondary organic aerosol (SOA) was simulated with the Secondary ORGanic Aerosol Model (SORGAM) by a classical gas-particle partitioning concept, using the two-product model approach, which is widely used in chemical transport models. In this study, we extensively updated SORGAM including three major modifications: firstly, we derived temperature dependence functions of the SOA yields for aromatics and biogenic VOCs (volatile organic compounds), based on recent chamber studies within a sophisticated mathematic optimization framework; secondly, we implemented the SOA formation pathways from photo oxidation (OH initiated) of isoprene; thirdly, we implemented the SOA formation channel from NO3-initiated oxidation of reactive biogenic hydrocarbons (isoprene and monoterpenes). The temperature dependence functions of the SOA yields were validated against available chamber experiments, and the updated SORGAM with temperature dependence functions was evaluated with the chamber data. Good performance was found with the normalized mean error of less than 30%. Moreover, the whole updated SORGAM module was validated against ambient SOA observations represented by the summed oxygenated organic aerosol (OOA) concentrations abstracted from aerosol mass spectrometer (AMS) measurements at a rural site near Rotterdam, the Netherlands, performed during the IMPACT campaign in May 2008. In this case, we embedded both the original and the updated SORGAM module into the EURopean Air pollution and Dispersion-Inverse Model (EURAD-IM), which showed general good agreements with the observed meteorological parameters and several secondary products such as O3, sulfate and nitrate. With the updated SORGAM module, the EURAD-IM model also captured the observed SOA concentrations reasonably well especially those during nighttime. In contrast, the EURAD-IM model before update underestimated the observations by a factor of up to 5. The large improvements of the modeled SOA concentrations by updated SORGAM were attributed to the mentioned three modifications. Embedding the temperature dependence functions of the SOA yields, including the new pathways from isoprene photo oxidations, and switching on the SOA formation from NO3 initiated biogenic VOC oxidations, contributed to this enhancement by 10, 22 and 47%, respectively. However, the EURAD-IM model with updated SORGAM still clearly underestimated the afternoon SOA observations up to a factor of two.

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

2013-07-01

82

Size-differentiated composition of inorganic atmospheric aerosols of both marine and polluted continental origin  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols were sampled with a high volume impactor/diffusion battery system and the collected fractions analysed for their major water-soluble inorganic constituents. Sulphate, nitrate and chloride showed bimodal distributions; sulphate and nitrate were mainly associated with NH 4+, having approximately log-normal distributions with modes at 1.0 ?m. In unpolluted maritime air, chlorides appeared as salts of sodium and magnesium with average modes at c. 5 ?m, whilst in polluted air masses significant concentrations of ammonium chloride sub-?m aerosols were detected. Sodium nitrate and sodium sulphate aerosols having average modes of c. 3.5 ?m were observed in mixed maritime/polluted air masses. The dimensions of these particles indicate formation from absorption of H 2SO 4 and HNO 3 at the surface of marine NaCl particles. The concentration of H + was very low, but the possibility of its neutralization by atmospheric ammonia during sampling was ruled out by parallel air sampling using an 'ammonia denuder'.

Harrison, Roy M.; Pio, Casimiro A.

83

2-hydroxyterpenylic acid: an oxygenated marker compound for ?-pinene secondary organic aerosol in ambient fine aerosol.  

PubMed

An oxygenated MW 188 compound is commonly observed in substantial abundance in atmospheric aerosol samples and was proposed in previous studies as an ?-pinene-related marker compound that is associated with aging processes. Owing to difficulties in producing this compound in sufficient amounts in laboratory studies and the occurrence of isobaric isomers, a complete assignment for individual MW 188 compounds could not be achieved in these studies. Results from a comprehensive mass spectrometric analysis are presented here to corroborate the proposed structure of the most abundant MW 188 compound as a 2-hydroxyterpenylic acid diastereoisomer with 2R,3R configuration. The application of collision-induced dissociation with liquid chromatography/electrospray ionization-ion trap mass spectrometry in both negative and positive ion modes, as well as chemical derivatization to methyl ester derivatives and analysis by the latter technique and gas chromatography/electron ionization mass spectrometry, enabled a comprehensive characterization of MW 188 isomers, including a detailed study of the fragmentation behavior using both mass spectrometric techniques. Furthermore, a MW 188 positional isomer, 4-hydroxyterpenylic acid, was tentatively identified, which also is of atmospheric relevance as it could be detected in ambient fine aerosol. Quantum chemical calculations were performed to support the diastereoisomeric assignment of the 2-hydroxyterpenylic acid isomers. Results from a time-resolved ?-pinene photooxidation experiment show that the 2-hydroxyterpenylic acid 2R,3R diastereoisomer has a time profile distinctly different from that of 3-methyl-1,2,3-butanetricarboxylic acid, a marker for oxygenated (aged) secondary organic aerosol. This study presents a comprehensive chemical data set for a more complete structural characterization of hydroxyterpenylic acids in ambient fine aerosol, which sets the foundation to better understand the atmospheric fate of ?-pinene in future studies. PMID:24697354

Kahnt, Ariane; Iinuma, Yoshiteru; Blockhuys, Frank; Mutzel, Anke; Vermeylen, Reinhilde; Kleindienst, Tadeusz E; Jaoui, Mohammed; Offenberg, John H; Lewandowski, Michael; Böge, Olaf; Herrmann, Hartmut; Maenhaut, Willy; Claeys, Magda

2014-05-01

84

Modeling Gas-phase Glyoxal and Associated Secondary Organic Aerosol Formation in a Megacity using WRF/Chem  

NASA Astrophysics Data System (ADS)

Organic aerosol (OA) as one of a major fine particulate matter in the atmosphere plays an important role in air pollution, human health, and climate forcing. OA is composed of directly emitted primary organic aerosol and chemically produced secondary organic aerosols (SOA). Despite much recent progress in understanding SOA formation, current air quality models cannot explain the magnitude and growth of atmospheric SOA, due to high uncertainties in sources, properties, and chemical reactions of precursors and formation pathways of SOA. Recent laboratory and modeling studies showed that glyoxal may serve as an important SOA precursor in the condensed solution of inorganic or organic aerosol particles (e.g., ammonium sulfate, fulvic acid, and amino acids). In this study, the Weather Research and Forecasting model with chemistry (WRF/Chem) is modified to account for the latest observed gas-phase yields of glyoxal from various volatile organic compounds (VOCs) and the associated SOA formation in the aqueous aerosol phase. The SOA formation in the aqueous aerosol phase is implemented using two approaches. In the first approach, two simplified parameterizations are used to represent the lumped particle-phase chemical processes under dark conditions and photochemical surface uptake. In the second approach, more detailed kinetic glyoxal reactions such as reversible glyoxal uptake, dimer formation of glyoxal, and oligomerization are treated and resolved explicitly. The updated WRF/Chem is assessed over the Mexico City and the surrounding region during March 2006 using the MILAGRO campaign data. Various observations such as organic matter from Aerodyne Aerosol Mass Spectrometer and VOCs from Proton-transfer Ion Trap Mass Spectrometry were compared. The preliminary results showed that the addition of the SOA formation from glyoxal in aqueous particles brings SOA predictions into a better agreement with field observations, in particular in presence of high relative humidity. The simulation with updated glyoxal yields gives a factor of 2 higher mixing ratio of glyoxal. The uncertainties in the model treatments as well as future work will also be discussed.

Wang, K.; Hodzic, A.; Barth, M. C.; Jimenez, J. L.; Volkamer, R.; Ervens, B.; Zhang, Y.

2011-12-01

85

High Molecular Weight Dimer Esters in ?-Pinene Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Monoterpenes, such as ?-pinene, constitute an important group of biogenic volatile organic compounds (BVOC). Once emitted into the atmosphere ?-pinene is removed by oxidization by the hydroxyl radical (OH), reactions with ozone (O3), and with nitrate radicals (NO3) resulting in the formation of first-generation oxidation products, such as semi-volatile carboxylic acids. In addition, higher molecular weight dimer esters originating from the oxidation of ?-pinene have been observed in both laboratory-generated and ambient secondary organic aerosols (SOA). While recent studies suggest that the dimers are formed through esterification between carboxylic acids in the particle phase, the formation mechanism of the dimer esters is still ambiguous. In this work, we present the results of a series of smog chamber experiments to assess the formation of dimer esters formed from the oxidation of ?-pinene. Experiments were conducted in the University of North Carolina (UNC) dual outdoor smog chamber facility to investigate the effect of oxidant species (OH versus O3), relative humidity (RH), and seed aerosol acidity in order to obtain a better understanding of the conditions leading to the formation of the dimer esters and how these parameters may affect the formation and chemical composition of SOA. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), and a total of eight carboxylic acids and four dimer esters were identified, constituting between 8 and 12 % of the total ?-pinene SOA mass.

Kristensen, Kasper; Cui, Tianqu; Zhang, Haofei; Gold, Avram; Glasius, Marianne; Surratt, Jason D.

2014-05-01

86

Contribution of primary and secondary sources to organic aerosol and PM2.5 at SEARCH network sites.  

PubMed

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. Laboratory chamber experiments provide insights into the precursors of SOA, but field data must be used to test the approaches. This study investigates primary and secondary sources of organic carbon (OC) and determines their mass contribution to particulate matter 2.5 microm or less in aerodynamic diameter (PM2.5) in Southeastern Aerosol Research and Characterization (SEARCH) network samples. Filter samples were taken during 20 24-hr periods between May and August 2005 at SEARCH sites in Atlanta, GA (JST); Birmingham, AL (BHM); Centerville, AL (CTR); and Pensacola, FL (PNS) and analyzed for organic tracers by gas chromatography-mass spectrometry. Contribution to primary OC was made using a chemical mass balance method and to secondary OC using a mass fraction method. Aerosol masses were reconstructed from the contributions of POA, SOA, elemental carbon, inorganic ions (sulfate [SO4(2-)], nitrate [NO3-], ammonium [NH4+]), metals, and metal oxides and compared with the measured PM2.5. From the analysis, OC contributions from seven primary sources and four secondary sources were determined. The major primary sources of carbon were from wood combustion, diesel and gasoline exhaust, and meat cooking; major secondary sources were from isoprene and monoterpenes with minor contributions from toluene and beta-caryophyllene SOA. Mass concentrations at the four sites were determined using source-specific organic mass (OM)-to-OC ratios and gave values in the range of 12-42 microg m(-3). Reconstructed masses at three of the sites (JST, CTR, PNS) ranged from 87 to 91% of the measured PM2.5 mass. The reconstructed mass at the BHM site exceeded the measured mass by approximately 25%. The difference between the reconstructed and measured PM2.5 mass for nonindustrial areas is consistent with not including aerosol liquid water or other sources of organic aerosol. PMID:21141432

Kleindienst, Tadeusz E; Lewandowski, Michael; Offenberg, John H; Edney, Edward O; Jaoui, Mohammed; Zheng, Mei; Ding, Xiang; Edgerton, Eric S

2010-11-01

87

Atmospheric Secondary Aerosol Formation by Heterogeneous Reactions of Aldehydes in the Presence of a Sulfuric Acid Aerosol Catalyst  

NASA Astrophysics Data System (ADS)

Particle growth by the heterogeneous reaction of aldehydes was observed in 0.5 m3 indoor Teflon bags in the presence of background seed aerosols. The aldehydes used were: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. This result was compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a differential mobility analyzer (DMA), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups in the aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst.

Jang, M.; Kamens, R. M.

2001-12-01

88

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

89

Radiative Effects of Carbonaceous and Inorganic Aerosols over California during CalNex and CARES: Observations versus Model Predictions  

NASA Astrophysics Data System (ADS)

Aerosols have been identified to be a major contributor to the uncertainty in understanding the present climate. Most of this uncertainty arises due to the lack of knowledge of their micro-physical and chemical properties as well as how to adequately represent their spatial and temporal distributions. Increased process level understanding can be achieved through carefully designed field campaigns and experiments. These measurements can be used to elucidate the aerosol properties, mixing, transport and transformation within the atmosphere and also to validate and improve models that include meteorology-aerosol-chemistry interactions. In the present study, the WRF-Chem model is used to simulate the evolution of carbonaceous and inorganic aerosols and their impact on radiation during May and June of 2010 over California when two field campaigns took place: the California Nexus Experiment (CalNex) and Carbonaceous Aerosol and Radiative Effects Study (CARES). We merged CalNex and CARES data along with data from operational networks such as, California Air Resources Board (CARB's) air quality monitoring network, the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, the AErosol RObotic NETwork (AERONET), and satellites into a common dataset for the Aerosol Modeling Test bed. The resulting combined dataset is used to rigorously evaluate the model simulation of aerosol mass, size distribution, composition, and optical properties needed to understand uncertainties that could affect regional variations in aerosol radiative forcing. The model reproduced many of the diurnal, multi-day, and spatial variations of aerosols as seen in the measurements. However, regionally the performance varied with reasonably good agreement with observations around Los Angeles and Sacramento and poor agreement with observations in the vicinity of Bakersfield (although predictions aloft were much better). Some aerosol species (sulfate and nitrate) were better represented than others (organic matter, black carbon) at many locations. The model also reproduced the observed transport of sea-salt by intrusions of marine air from the Bay Area to Sacramento. The vertical distribution of aerosols was simulated reasonably as evidenced from comparison with observed profiles from the High Spectral Resolution Lidar (HSRL) on the NASA B-200 aircraft, although the values in the boundary layer were too high at times. Consistent with the bias in aerosol mass, the simulated column aerosol optical depths at the AERONET and field campaign sites were often too high. Comparisons between observed and predicted aerosol optical depth and single scattering albedo will be presented. Using aerosol observations as a constraint, we will present the radiative effect of simulated aerosols and its sensitivity to the uncertainties in predicted aerosol properties.

Vinoj, V.; Fast, J. D.; Liu, Y.

2012-12-01

90

Secondary organic aerosol formation in urban air: Temporal variations and possible contributions from unidentified hydrocarbons  

Microsoft Academic Search

Quantitative evaluation of the performance of one of the most advanced mechanistic secondary organic aerosol (SOA) modules\\/models, the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution 2 (MADRID2) in the three-dimensional Models-3\\/Community Multiscale Air Quality (CMAQ), in urban air is made. Model calculations are compared for the Tokyo, Japan, metropolitan area with measurements made using an Aerodyne quadrupole aerosol mass

H. Matsui; M. Koike; N. Takegawa; Y. Kondo; R. J. Griffin; Y. Miyazaki; Y. Yokouchi; T. Ohara

2009-01-01

91

[Seasonal distribution of water-soluble inorganic ions in the atmospheric aerosol in Qingdao].  

PubMed

To collect comprehensive information on the characteristics and sources of water-soluble ions in the atmospheric aerosol in Qingdao, samples of total suspended particles (TSP) were collected from January to December 2008, and the concentrations of the major water-soluble inorganic ions were analyzed using ion chromatography. The results showed that SO4(2-), NO3-, NH4+ and Cl- were the dominant water-soluble ions in TSP, the sum of the four accounting for 86.9% of water-soluble ions in mass concentration. TSP and water-soluble inorganic ions showed obvious seasonal variations and there were a variety of sources. The mass concentrations of Na+, NH4+, Ca2+, F- and Mg2+ were highest in winter and lowest in summer. The concentrations of K+ and PO4(3-) were highest in autumn and lowest in summer. NO3-, Cl- and SO4(2-) concentrations had the highest values in spring, winter, and spring, respectively. Different weather conditions had great influence on the concentrations of TSP and water-soluble ions. The mass concentrations of TSP were highest in dust weather followed by haze, smog, fog and sunny days. The average mass concentrations of Na+ , Mg2+, Ca2+, F- , Cl- and PO4(3-) were highest in smog days while the other ions in haze days. PMID:23002589

Liu, Zhen; Qi, Jian-Hua; Wang, Lin; Chen, Xiao-Jing; Shi, Jin-Hui; Gao, Hui-Wang

2012-07-01

92

Experimental Determination of Chemical Diffusion within Secondary Organic Aerosol Particles  

SciTech Connect

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.

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

2013-02-28

93

Nonequilibrium Atmospheric Secondary Organic Aerosol Formation and Growth  

SciTech Connect

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.

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

94

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

NASA Astrophysics Data System (ADS)

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 (2007) Annual Review of Physical Chemistry 58: 321-352 2. Szmigielski, R., J.D. Surratt, Y. Gomez-Gonzalez, P. Van der Veken, I. Kourtchev, R. Vermeylen, F. Blockhuys, M. Jaoui, T.E. Kleindienst, M. Lewandowski, J.H. Offenberg, E.O. Edney, J.H. Seinfeld, W. Maenhaut and M. Claeys (2007) Geophysical Research Letters 34(24) 3. Jimenez, JL , et al. (2009) Science (326), 1525-1529

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

2010-05-01

95

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...

96

Elucidating secondary organic aerosol from diesel and gasoline vehicles through detailed characterization of  

E-print Network

Elucidating secondary organic aerosol from diesel and gasoline vehicles through detailed 19, 2012 (received for review July 22, 2012) Emissions from gasoline and diesel vehicles and diesel vehicles, and find diesel exhaust is seven times more efficient at forming aerosol than gasoline

Silver, Whendee

97

Oxidation of ambient biogenic secondary organic aerosol by hydroxyl radicals: Effects on cloud condensation nuclei activity  

E-print Network

Changes in the hygroscopicity of ambient biogenic secondary organic aerosols (SOA) due to controlled OH oxidation were investigated at a remote forested site at Whistler Mountain, British Columbia during July of 2010. ...

Wong, J. P. S.

98

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...

99

Investigation of the correlation between odd oxygen and secondary organic aerosol in Mexico City and Houston  

E-print Network

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. ...

Wood, E. C.

100

A Methodology for the Prediction of the Chemical Composition of Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols have been identified by the Intergovernmental Panel on Climate Change in their recent reports (IPCC, 2007) as a key influence on climate change, but as also an influence about which we have minimal understanding. Atmospheric aerosols can contain a wide range of components but most are believed to be mainly composed of an inorganic part, an organic part and associated water. The inorganic component is relatively well understood and is composed of a limited number of ionic species. However, the organic component is much more complex as any of the thousands of organic compounds found in the atmosphere can potentially condense into the aerosol. A major contributor to the organic aerosol is believed to be from chemicals formed by atmospheric processes. Volatile organic compounds (VOC's) from both anthropogenic and biogenic sources (primary emissions), undergo progressive oxidation in the atmosphere and the products of these atmospheric reactions may contribute to the formation of secondary organic aerosol (SOA) particles. The oxidation process leads to increased functionalization of the VOC with a resulting increase in polarity and decrease in volatility. The less volatile components in this mixture may condense to form SOA particles by nucleation or by condensation onto particles (such as involatile primary emissions, or polymerised water soluble material) already present in the atmosphere. There is much speculation about the composition of SOA particles as complete analyses are not available. One approach is to model the formation of SOA using an explicit atmospheric chemistry scheme coupled to a condensation/absorption model. We will report on the use the Master Chemical Mechanism (MCM:- see http://mcm.leeds.ac.uk/MCM/) with a modified version of the Pankow absorption model to predict the chemical composition of SOA particles formed under a range of conditions. The MCM provided the atmospheric abundances of 3700 non-radical atmospheric chemical species in a trajectory model of a heavily polluted air parcel that arrived at Writtle (Essex) in the south of England at 18:00 on August 6th 2003 during the TORCH campaign. A similar set of abundances were simulated for an air-parcel arriving on August 12th with high concentrations of VOC's from biological sources. These two sets of atmospheric concentrations formed the inputs for the calculation of the chemical composition of anthropogenically dominated and biogenically dominated SOA respectively. The condensation of the oxidised VOC's were modelled using the following methodology:- 1) The model used was a modified version of the Pankow absorption model. 2) Estimated vapour pressures were used for all components and liquid phase ideality was assumed. 3) It was assumed that water condensed into the SOA alongside the organic components. 4) As liquid phase water is expected to be present the acid anhydrides predicted to be present in the atmosphere are expected to hydrolyse to their corresponding acids. 5) The presence of an involatile core onto which the organics can condense is assumed. Formation of SOA by condensation was modelled for both the anthropogenic and biogenic case over a range of temperatures, relative humidity and target mass (=core mass+SOA mass). This provided a range of SOA masses- particularly for the anthropogenic case where it was clear that the chemical composition of the SOA was strongly affected by the mass of SOA predicted. The results showed that anthropogenic SOA contained significant dicarboxylic acids derived from the hydrolysis of cyclic anhydrides while the biogenic SOA contained pinic acid (another dicarboxylic acid) and a range of multifunctional compounds dominated by hydroxyl and hydroperoxide groups.

Barley, M.; Topping, D.; McFiggans, G.; Jenkin, M.

2009-04-01

101

Dimers in ?-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity  

NASA Astrophysics Data System (ADS)

The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of ?-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of ?-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high-NO conditions. However, no effect of RH on SOA mass was evident. Ozone (O3)-initiated oxidation of ?-pinene in the presence of ammonium sulfate (AS) seed coated with organic aerosol from OH-initiated oxidation of ?-pinene showed reduced nucleation compared to ozonolysis in the presence of pure AS seed aerosol. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), with a focus on the formation of carboxylic acids and high-molecular weight dimers. A total of eight carboxylic acids and four dimers were identified, constituting between 8 and 12% of the total ?-pinene SOA mass. OH-initiated oxidation of ?-pinene in the presence of nitrogen oxides (NOx) resulted in the formation of highly oxidized carboxylic acids, such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and diaterpenylic acid acetate (DTAA). The formation of dimers was observed only in SOA produced from the ozonolysis of ?-pinene in the absence of NOx, with increased concentrations by a factor of two at higher RH (50-90%) relative to lower RH (30-50%). The increased formation of dimers correlates with an observed increase in new particle formation at higher RH due to nucleation. Increased aerosol acidity was found to have a negligible effect on the formation of the dimers. SOA mass yield did not influence the chemical composition of SOA formed from ?-pinene ozonolysis with respect to carboxylic acids and dimers. The results support the formation of the high-molecular weight dimers through gas-phase reactions of the stabilized Criegee Intermediate (sCI) formed from the ozonolysis of ?-pinene. The high molecular weight and polar nature of dimers formed in the gas phase may explain increased particle number concentration as a result of homogenous nucleation. Since three of these dimers (i.e. pinyl-diaterpenyl dimer (MW 358), pinyl-diaterebyl dimer (MW 344) and pinonyl-pinyl dimer (MW 368)) have been observed in both laboratory-generated and ambient fine organic aerosol samples, we conclude that the dimers observed in this study can be used as tracers for the O3-initiated oxidation of ?-pinene, and are therefore indicative of enhanced anthropogenic activities, and that the high molecular weight and low volatility dimers result in homogenous nucleation under laboratory conditions, increasing the particle number concentration.

Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

2014-04-01

102

Organic molecular composition of marine aerosols over the Arctic Ocean in summer: contributions of primary emission and secondary aerosol formation  

NASA Astrophysics Data System (ADS)

Organic molecular composition of marine aerosol samples collected during the MALINA cruise in the Arctic Ocean was investigated by gas chromatography/mass spectrometry. More than 110 individual organic compounds were determined in the samples and were grouped into different compound classes based on the functionality and sources. The concentrations of total quantified organics ranged from 7.3 to 185 ng m-3 (mean 47.6 ng m-3), accounting for 1.8-11.0% (4.8%) of organic carbon in the marine aerosols. Primary saccharides were found to be dominant organic compound class, followed by secondary organic aerosol (SOA) tracers formed from the oxidation of biogenic volatile organic compounds (VOCs) such as isoprene, ?-pinene and ?-caryophyllene. Mannitol, the specific tracer for airborne fungal spores, was detected as the most abundant organic species in the samples with a concentration range of 0.052-53.3 ng m-3 (9.2 ng m-3), followed by glucose, arabitol, and the isoprene oxidation products of 2-methyltetrols. Biomass burning tracers such as levoglucosan are evident in all samples with trace levels. On the basis of the tracer-based method for the estimation of fungal-spore OC and biogenic secondary organic carbon (SOC), we estimate that an average of 10.7% (up to 26.2%) of the OC in the marine aerosols was due to the contribution of fungal spores, followed by the contribution of isoprene SOC (mean 3.8%) and ?-pinene SOC (2.9%). In contrast, only 0.19% of the OC was due to the photooxidation of ?-caryophyllene. This study indicates that primary organic aerosols from biogenic emissions, both from long-range transport of mid-latitude aerosols and from sea-to-air emission of marine organics, as well as secondary organic aerosols formed from the photooxidation of biogenic VOCs are important factors controlling the organic chemical composition of marine aerosols in the Arctic Ocean.

Fu, P. Q.; Kawamura, K.; Chen, J.; Charrière, B.; Sempéré, R.

2013-02-01

103

Organic molecular composition of marine aerosols over the Arctic Ocean in summer: contributions of primary emission and secondary aerosol formation  

NASA Astrophysics Data System (ADS)

Organic molecular composition of marine aerosol samples collected during the MALINA cruise in the Arctic Ocean was investigated by gas chromatography/mass spectrometry. More than 110 individual organic compounds were determined in the samples and were grouped into different compound classes based on the functionality and sources. The concentrations of total quantified organics ranged from 7.3 to 185 ng m-3 (mean 47.6 ng m-3), accounting for 1.8-11.0% (4.8%) of organic carbon in the marine aerosols. Primary saccharides were found to be dominant organic compound class, followed by secondary organic aerosol (SOA) tracers formed from the oxidation of biogenic volatile organic compounds (VOCs) such as isoprene, ?-pinene and ?-caryophyllene. Mannitol, the specific tracer for airborne fungal spores, was detected as the most abundant organic species in the samples with a concentration range of 0.052-53.3 ng m-3 (9.2 ng m-3), followed by glucose, arabitol, and the isoprene oxidation products of 2-methyltetrols. Biomass burning tracers such as levoglucosan are evident in all samples with trace levels. On the basis of the tracer-based method for the estimation of fungal-spore OC and biogenic secondary organic carbon (SOC), we estimate that an average of 10.7% (up to 26.2%) of the OC in the marine aerosols was due to the contribution of fungal spores, followed by the contribution of isoprene SOC (mean 3.8%) and ?-pinene SOC (2.9%). In contrast, only 0.19% of the OC was due to the photooxidation of ?-caryophyllene. This study indicates that primary organic aerosols from biogenic emissions, both from long-range transport of mid-latitude aerosols and from sea-to-air emission of marine organics, as well as secondary organic aerosols formed from the photooxidation of biogenic VOCs are important factors controlling the organic chemical composition of marine aerosols in the Arctic Ocean.

Fu, P. Q.; Kawamura, K.; Chen, J.; Charrière, B.; Sempéré, R.

2012-08-01

104

The role of long-range transport and domestic emissions in determining atmospheric secondary inorganic particle concentrations across the UK  

NASA Astrophysics Data System (ADS)

Surface concentrations of secondary inorganic particle components over the UK have been analysed for 2001-2010 using the EMEP4UK regional atmospheric chemistry transport model. In early 2003 an episode of substantially elevated surface concentrations of ammonium nitrate was measured across the UK by the AGANET network. The EMEP4UK model was able accurately to represent both the long-term decadal surface concentrations and the episode in 2003. The latter was identified as consisting of three separate episodes, each of less than 1 month duration, in February, March and April. The primary cause of the elevated nitrate levels across the UK was meteorological, a persistent high pressure system, but whose varying location impacted the relative importance of transboundary vs. domestic emissions. Whilst long-range transport dominated the elevated nitrate in February, in contrast it was domestic emissions that mainly contributed to the March episode, and for the April episode both domestic emissions and long-range transport contributed. A prolonged episode such as the one in early 2003 can have substantial impact on annual average concentrations. The episode led to annual concentration differences at the regional scale of similar magnitude to those driven by long-term changes in precursor emissions over the full decade investigated here. The results demonstrate that a substantial part of the UK, particularly the south and south-east, may be close to or actually exceeding annual mean limit values because of import of inorganic aerosol components from continental Europe under specific conditions. The results reinforce the importance of employing multiple year simulations in the assessment of emissions reduction scenarios on PM concentrations and the need for international agreements to address the transboundary component of air pollution.

Vieno, M.; Heal, M. R.; Hallsworth, S.; Famulari, D.; Doherty, R. M.; Dore, A. J.; Tang, Y. S.; Braban, C. F.; Leaver, D.; Sutton, M. A.; Reis, S.

2013-12-01

105

Chemical characterisation of atmospheric aerosols during a 2007 summer field campaign at Brasschaat, Belgium: sources and source processes of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Measurements of organic marker compounds and inorganic species were performed on PM2.5 aerosols from a Belgian forest site that is severely impacted by urban pollution ("De Inslag", Brasschaat, Belgium) during a 2007 summer period within the framework of the "Formation mechanisms, marker compounds, and source apportionment for biogenic atmospheric aerosols (BIOSOL)" project. The measured organic species included (i) low-molecular weight (MW) dicarboxylic acids (LMW DCAs), (ii) methanesulfonate (MSA), (iii) terpenoic acids originating from the oxidation of ?-pinene, ?-pinene, d-limonene and ?3-carene, and (iv) organosulfates related to secondary organic aerosol from the oxidation of isoprene and ?-pinene. The organic tracers explained, on average, 5.3 % of the organic carbon (OC), of which 0.7 % was due to MSA, 3.4 % to LMW DCAs, 0.6 % to organosulfates, and 0.6 % to terpenoic acids. The highest atmospheric concentrations of most species were observed during the first five days of the campaign, which were characterised by maximum day-time temperatures >22 °C. Most of the terpenoic acids and the organosulfates peaked during day-time, consistent with their local photochemical origin. High concentrations of 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and low concentrations of cis-pinonic acid were noted during the first five days of the campaign, indicative of an aged biogenic aerosol. Several correlations between organic species were very high (r>0.85), high (0.70.7) and showed an Arrhenius-type relationship, consistent with their formation through OH radical chemistry.

Gómez-González, Y.; Wang, W.; Vermeylen, R.; Chi, X.; Neirynck, J.; Janssens, I. A.; Maenhaut, W.; Claeys, M.

2012-01-01

106

Experimental determination of chemical diffusion within secondary organic aerosol particles.  

PubMed

Formation, properties, transformations, and temporal evolution of secondary organic aerosol (SOA) particles depend strongly on SOA phase. Recent experimental evidence from both our group and several others indicates that, in contrast to common models' assumptions, SOA constituents do not form a low-viscosity, well-mixed solution, yielding instead a semisolid phase with high, but undetermined, viscosity. We find that when SOA particles are made in the presence of vapors of semi-volatile hydrophobic compounds, such molecules become trapped in the particles' interiors and their subsequent evaporation rates and thus their rates of diffusion through the SOA can be directly obtained. Using pyrene as the tracer molecule and SOA derived from ?-pinene ozonolysis, we find that it takes ~24 hours for half the pyrene to evaporate. Based on the observed pyrene evaporation kinetics we estimate a diffusivity of 2.5 × 10(-21) m(2) s(-1) for pyrene in SOA. Similar measurements on SOA doped with fluoranthene and phenanthrene yield diffusivities comparable to that of pyrene. Assuming a Stokes-Einstein relation, an approximate viscosity of 10(8) Pa s can be calculated for this SOA. Such a high viscosity is characteristic of tars and is consistent with published measurements of SOA particle bounce, evaporation kinetics, and the stability of two reverse-layered morphologies. We show that a viscosity of 10(8) Pa s implies coalescence times of minutes, consistent with the findings that SOA particles formed by coagulation are spherical on the relevant experimental timescales. Measurements on aged SOA particles doped with pyrene yield an estimated diffusivity ~3 times smaller, indicating that hardening occurs with time, which is consistent with the increase in SOA oligomer content, decrease in water uptake, and decrease in evaporation rates previously observed with aging. PMID:23340901

Abramson, Evan; Imre, Dan; Beránek, Josef; Wilson, Jacqueline; Zelenyuk, Alla

2013-02-28

107

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

SciTech Connect

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.

John H. Seinfeld

2011-12-08

108

Secondary Organic Aerosol Formation from Glyoxal: Effects of Seed Aerosol on Particle Composition  

NASA Astrophysics Data System (ADS)

Conventional models of secondary organic aerosol (SOA) production neglect aqueous-phase processing mechanisms, thereby excluding potentially important SOA formation pathways. These missing pathways may be an important factor in the inability of current models to fully explain SOA yields and oxidation states. Molecules identified as important precursors to SOA generated through aqueous-phase include glyoxal, which is an oxidation product of numerous organic gases. Glyoxal SOA formation experiments were conducted in the PSI smog chamber as a function of seed composition, relative humidity (RH, 60 to 85%), and the presence/absence of gaseous ammonia, affecting particle acidity. In a typical experiment, the chamber was filled with the selected seed aerosol (NaCl, (NH4)2SO4, NaNO3, or K2SO4), after which glyoxal was generated by the brief (i.e. a few minutes) exposure of acetylene to UV light. The experiment was then allowed to proceed undisturbed for several hours. Each experiment consisted of several UV exposures, followed by a dilution phase at constant RH to investigate the gas/particle partitioning behavior of the generated SOA. Gas-phase glyoxal was monitored by an LED-CE-DOAS system, while the particle composition was measured using online aerosol mass spectrometry (Aerodyne HR-ToF-AMS) and offline analysis of collected filter samples. SOA composition was observed to depend strongly on seed type, with increased imidazole formation evident during experiments with (NH4)2SO¬4 and K2SO4 seeds relative to those with NaCl and NaNO3. Additionally, experiments conducted in the presence of ammonia showed large enhancements in both imidazole content and total SOA yield. Analysis of mass spectral markers indicates reversible uptake of glyoxal but irreversible particle-phase production of the imidazole-containing SOA. Positive matrix factorization (PMF) using the Multilinear Engine (ME-2) was applied to the AMS mass spectral time series to quantify factors related to reaction progress and product formation (e.g. glyoxal and different types of irreversibly-generated SOA). We will discuss glyoxal SOA yields and product distributions in terms of seed composition and ammonia effects.

Slowik, Jay; Waxman, Eleanor; Coburn, Sean; Klein, Felix; Koenig, Theodore; Krapf, Manuel; Kumar, Nivedita; Wang, Siyuan; Baltensperger, Urs; Dommen, Josef; Prévôt, Andre; Volkamer, Rainer

2014-05-01

109

Examination of the Effects of Sea Salt Aerosols on Southeast Texas Ozone and Secondary Organic Aerosol  

E-print Network

Despite decades of study, we still do not fully understand aerosols and their interactions among gases or other aerosols in the atmosphere. Among their impacts, they influence radiative transfer in the atmosphere and contribute to cloud formation...

Benoit, Mark David

2013-02-06

110

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...

111

Mass yields of secondary organic aerosols from the oxidation of alpha-pinene and real plant emissions  

E-print Network

Biogenic volatile organic compounds (VOCs) are a significant source of global secondary organic aerosol (SOA); however, quantifying their aerosol forming potential remains a challenge. This study presents smog chamber ...

Kroll, Jesse

112

Secondary organic aerosol formation from the irradiation of simulated automobile exhaust.  

PubMed

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

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

113

Deposition ice nucleation on fresh, cloud processed, internally mixed and oxidatively aged ?-pinene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

There are many uncertainties related to role of organic aerosol (OA) as ice nuclei (IN). To that end, the ice nucleating abilities of fresh, cloud processed, internally mixed, and oxidatively aged secondary organic aerosol (SOA) particles were investigated with the University of Toronto continuous flow diffusion chamber (UT-CFDC) at temperatures relevant for cirrus cloud formation. Our SOA particles were produced by ?-pinene ozonolysis which took place in a flow tube (FT) and a smog chamber (SC). The FT-SOA particles mimicked freshly formed particles while the water soluble organic compound (WSOC) experiments from both the flow tube (FT-WSOC-SOA) and the smog chamber (SC-WSOC-SOA) capture the character of aged and cloud processed SOA particles. The FT-SOA particles exhibited low ice nucleation efficiency, i.e. relative humidities with respect to ice (RHi) of 152×4% and 157×4% were required to activate 0.1% of the aerosol particles in deposition mode at 223K and 218K, respectively. Similarly, the IN efficiencies of the FT-WSOC-SOA and SC-WSOC-SOA particles were found to be comparably low between 233K and 214K. However, if both the FT-WSOC-SOA and the SC-WSOC-SOA particles were pre-cooled at 233K prior to entering the UT-CFDC they nucleate ice at between 6 to 9% lower relative humidities, probably due to decreased viscosity. We also observed that an increase in the oxygen to carbon ratio (from 0.39 to 0.78) of the SC-WSOC-SOA particles from aqueous oxidative processing did not modify IN abilities. Finally, given that SOA is commonly mixed with inorganic salts, especially when arising through cloud processing, it was found that internally mixed particles of SC-WSOC-SOA and ammonium sulfate (AS) had a significantly higher RHi (140×5% at 219K) than pure AS particles of the same size (125×4%). Overall conclusions are that SOA-containing particles may act as IN only in regions where more efficient are not present. The SOA component will serve to suppress the IN abilities of efficient IN when internally mixed.

Ladino Moreno, L.; Zhou, S.; Aljawhary, D.; Yakobi-Hancock, J.; Abbatt, J.

2013-12-01

114

Source indicators of biomass burning associated with inorganic salts and carboxylates in dry season ambient aerosol in Chiang Mai Basin, Thailand  

NASA Astrophysics Data System (ADS)

PM10 aerosol was collected between February and April 2010 at an urban site (CMU) and an industrial site (TOT) in Chiang Mai, Thailand, and characteristics and provenance of water-soluble inorganic species, carboxylates, anhydrosugars and sugar alcohols were investigated with particular reference to air quality, framed as episodic or non-episodic pollution. Sulfate, a product of secondary photochemical reactions, was the major inorganic salt in PM10, comprising 25.9% and 22.3% of inorganic species at CMU and TOT, respectively. Acetate was the most abundant monocarboxylate, followed by formate. Oxalate was the dominant dicarboxylate. A high acetate/formate mass ratio indicated that primary traffic-related and biomass-burning emissions contributed to Chiang Mai aerosols during episodic and non-episodic pollution. During episodic pollution carboxylate peaks indicated sourcing from photochemical reactions and/or directly from traffic-related and biomass burning processes and concentrations of specific biomarkers of biomass burning including water-soluble potassium, glutarate, oxalate and levoglucosan dramatically increased. Levoglucosan, the dominant anhydrosugar, was highly associated with water-soluble potassium (r = 0.75-0.79) and accounted for 93.4% and 93.7% of anhydrosugars at CMU and TOT, respectively, during episodic pollution. Moreover, levoglucosan during episodic pollution was 14.2-21.8 times non-episodic lows, showing clearly that emissions from biomass burning are the major cause of PM10 episodic pollution in Chiang Mai. Additionally, the average levoglucosan/mannosan mass ratio during episodic pollution was 14.1-14.9, higher than the 5.73-7.69 during non-episodic pollution, indicating that there was more hardwood burning during episodic pollution. Higher concentrations of glycerol and erythritol during episodic pollution further indicate that biomass burning activities released soil biota from forest and farmland soils.

Tsai, Ying I.; Sopajaree, Khajornsak; Chotruksa, Auranee; Wu, Hsin-Ching; Kuo, Su-Ching

2013-10-01

115

Secondary Organic Aerosol Formation from the Photooxidation of Naphthalene  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants that are released into the atmosphere as a by-product of combustion processes. The gas-phase PAHs can be chemically transformed via reaction with the hydroxyl radical to produce a range of oxidised organic compounds and other pollutants such as ozone and secondary organic aerosol (SOA). Epidemiological studies have established that exposure to this type of air pollution is associated with damaging effects on the respiratory and cardiovascular systems, and can lead to asthma, oxidative stress, health deterioration and even death. The major anthropogenic source of SOA in urban areas is believed to be aromatic hydrocarbons, which are present in automobile fuels and are used as solvents. As a result, research is currently being performed on the characterisation of SOA produced from aromatic hydrocarbons such as toluene, the xylenes and trimethylbenzenes. However, significant amounts of PAHs are also released into urban areas from automobile emissions and the combustion of fossil fuels for home heating. Naphthalene is regularly cited as the most abundant PAH in polluted urban air, with typical ambient air concentrations of 0.05 - 0.20 parts per billion (ppbV) in European cities, comparable to the xylenes. Since naphthalene reacts in an analogous manner to monocyclic aromatic compounds then it is also expected to make a significant contribution to ambient SOA. However, the yield and chemical composition of SOA produced from the atmospheric degradation of naphthalene is not well known. In this presentation, the effects of NOx level and relative humidity on the SOA formation from the phootooixdation of naphthalene will be presented. A series of experiments has been performed in a large atmospheric simulation chamber equipped with a gas chromatograph and analyzers for monitoring nitrogen oxides (NOx) and ozone. SOA formation from the photooxidation of naphthalene was measured using a scanning mobility particle sizer. The effect of NOx concentration on SOA formation was evaluated by varying the initial naphthalene and NOx concentrations. The results clearly show that a higher hydrocarbon to NOx ratio produces a higher yield of SOA. The SOA mass yields were also found to increase as the relative humidity was raised from 0 to 50%. A recently developed denuder-filter sampling technique was used to investigate the gas/particle partitioning behavior of the photooxidation products. This work is the first study of the formation of SOA from naphthalene and the results will be compared to those obtained from other aromatic compounds.

Zhou, S.; Chen, Y.; Wenger, J.

2009-04-01

116

Secondary Organic Aerosol Formation from in-Use Motor Vehicle Emissions Using a Potential Aerosol Mass Reactor.  

PubMed

Secondary organic aerosol (SOA) formation from in-use vehicle emissions was investigated using a potential aerosol mass (PAM) flow reactor deployed in a highway tunnel in Pittsburgh, Pennsylvania. Experiments consisted of passing exhaust-dominated tunnel air through a PAM reactor over integrated hydroxyl radical (OH) exposures ranging from ?0.3 to 9.3 days of equivalent atmospheric oxidation. Experiments were performed during heavy traffic periods when the fleet was at least 80% light-duty gasoline vehicles on a fuel-consumption basis. The peak SOA production occurred after 2-3 days of equivalent atmospheric oxidation. Additional OH exposure decreased the SOA production presumably due to a shift from functionalization to fragmentation dominated reaction mechanisms. Photo-oxidation also produced substantial ammonium nitrate, often exceeding the mass of SOA. Analysis with an SOA model highlight that unspeciated organics (i.e., unresolved complex mixture) are a very important class of precursors and that multigenerational processing of both gases and particles is important at longer time scales. The chemical evolution of the organic aerosol inside the PAM reactor appears to be similar to that observed in the atmosphere. The mass spectrum of the unoxidized primary organic aerosol closely resembles ambient hydrocarbon-like organic aerosol (HOA). After aging the exhaust equivalent to a few hours of atmospheric oxidation, the organic aerosol most closely resembles semivolatile oxygenated organic aerosol (SV-OOA) and then low-volatility organic aerosol (LV-OOA) at higher OH exposures. Scaling the data suggests that mobile sources contribute ?2.9 ± 1.6 Tg SOA yr(-1) in the United States, which is a factor of 6 greater than all mobile source particulate matter emissions reported by the National Emissions Inventory. This highlights the important contribution of SOA formation from vehicle exhaust to ambient particulate matter concentrations in urban areas. PMID:25188317

Tkacik, Daniel S; Lambe, Andrew T; Jathar, Shantanu; Li, Xiang; Presto, Albert A; Zhao, Yunliang; Blake, Donald; Meinardi, Simone; Jayne, John T; Croteau, Philip L; Robinson, Allen L

2014-10-01

117

On molecular chirality within naturally occurring secondary organic aerosol particles from the central Amazon Basin.  

PubMed

In this perspectives article, we reflect upon the existence of chirality in atmospheric aerosol particles. We then show that organic particles collected at a field site in the central Amazon Basin under pristine background conditions during the wet and dry seasons consist of chiral secondary organic material. We show how the chiral response from the aerosol particles can be imaged directly without the need for sample dissolution, solvent extraction, or sample preconcentration. By comparing the chiral-response images with optical images, we show that chiral responses always originate from particles on the filter, but not all aerosol particles produce chiral signals. The intensity of the chiral signal produced by the size resolved particles strongly indicates the presence of chiral secondary organic material in the particle. Finally, we discuss the implications of our findings on chiral atmospheric aerosol particles in terms of climate-related properties and source apportionment. PMID:21633733

Martinez, Imee Su; Peterson, Mark D; Ebben, Carlena J; Hayes, Patrick L; Artaxo, Paulo; Martin, Scot T; Geiger, Franz M

2011-07-14

118

Real-Time Secondary Aerosol Formation Measurements using a Photooxidation Reactor (PAM) and AMS in Urban Air and Biomass Smoke  

NASA Astrophysics Data System (ADS)

Recent field studies reveal large formation of secondary organic aerosol (SOA) under urban polluted ambient conditions, while SOA formation in biomass burning smoke appears to be variable but sometimes substantial. To study this formation in real-time, a Potential Aerosol Mass (PAM) photooxidation reactor was deployed with submicron aerosol size and chemical composition measurements during two studies: FLAME-3, a biomass-burning study at USDA Fire Sciences Laboratory in Missoula in 2009, MT and CalNex-LA in Pasadena, CA in 2010. A high-resolution aerosol mass spectrometer (HR-AMS) and a scanning mobility particle sizer (SMPS) alternated sampling unprocessed and PAM-processed aerosol. The PAM reactor produces OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent aging of ~2 weeks in 5 minutes of processing. The OH intensity was also scanned every 20 min. in both field studies. Results show the value of PAM-AMS as a tool for in-situ evaluation of changes in OA concentration and composition due to SOA formation and POA oxidation. In FLAME-3, net SOA formation was variable among smokes from different biomasses; however, OA oxidation was always observed. The average SOA enhancement factor was 1.7 +/- 0.5 of the initial POA. Reactive VOCs such as toluene, monoterpenes, and acetaldehyde, as measured from a PIT-MS, decreased with increased PAM processing; however, formic acid, acetone, and some unidentified OVOCs increased after significant exposure to high oxidant levels suggesting multigenerational chemistry. Results from CalNex-LA show enhancement of SOA and inorganic aerosol from gas-phase precursors. This enhanced OA mass increase from PAM processing is maximum at night and correlates with trimethylbenzene concentrations, which indicates the dominance of short-lived SOA precursors in the LA Basin. A traditional SOA model with mostly aromatic precursors underpredicts the amount of SOA formed by about an order-of-magnitude, which is consistent with model evaluations for ambient air at many polluted locations. These results suggest that photooxidation reactors may be useful tools to identify and quantify aerosol precursors and formation potential in the ambient atmosphere.

Ortega, A. M.; Cubison, M.; Hayes, P. L.; Brune, W. H.; Hu, W.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; Alvarez, S. L.; Rappenglueck, B.; Bon, D.; Graus, M.; Warneke, C.; Gilman, J. B.; Kuster, W. C.; De Gouw, J. A.; Sullivan, A. P.; Jimenez, J. L.

2011-12-01

119

Secondary Aerosol: Precursors and Formation Mechanisms. Technical Report on Grant  

SciTech Connect

This project focused on studying trace gases that participate in chemical reactions that form atmospheric aerosols. Ammonium sulfate is a major constituent of these tiny particles, and one important pathway to sulfate formation is oxidation of dissolved sulfur dioxide by hydrogen peroxide in cloud, fog and rainwater. Sulfate aerosols influence the number and size of cloud droplets, and since these factors determine cloud radiative properties, sulfate aerosols also influence climate. Peroxide measurements, in conjunction with those of other gaseous species, can used to distinguish the contribution of in-cloud reaction to new sulfate aerosol formation from gas-phase nucleation reactions. This will lead to more reliable global climate models. We constructed and tested a new 4-channel fluorescence detector for airborne detection of peroxides. We integrated the instrument on the G-1 in January, 2006 and took a test flight in anticipation of the MAX-Mex field program, where we planned to fly under pressurized conditions for the first time. We participated in the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) - Megacity Aerosol EXperiment â?? Mexico City (MAX-Mex) field measurement campaign. Peroxide instrumentation was deployed on the DOE G-1 research aircraft based in Veracruz, and at the surface site at Tecamac University.

Weinstein-Lloyd, Judith B

2009-05-04

120

The roles of individual oxidants in secondary organic aerosol formation from ? 3-carene: 1. gas-phase chemical mechanism  

NASA Astrophysics Data System (ADS)

Oxidation of certain gas-phase organic species results in secondary products of volatility that is sufficiently low that they partition between the gas and aerosol phases. The fraction that partitions to the aerosol phase is known as secondary organic aerosol (SOA). The present paper reviews the relevant chemistry and describes the development of a chemical mechanism that consists of the gas-phase reactions of ? 3-carene and its products, including the formation of individual organic oxidation products that are capable of forming SOA. The mechanism also incorporates ozone formation chemistry and other relevant inorganic reactions. The new mechanism differentiates specific oxidation products according to both molecular structure and routes of formation. The concentrations of oxidation products (termed cross-products) that are formed in pathways involving two or more oxidants (ozone, the oxygen atom, and the hydroxyl and nitrate radicals) are accurately accounted in this way. The mechanism is evaluated in a zero-dimensional model by simulating gas-phase concentrations of ? 3-carene, oxides of nitrogen, and ozone from ozonolysis, nitrate radical, and photooxidation chamber experiments in which ? 3-carene was oxidized. Simulation results indicate that the main characteristics of the chemistry are adequately described by the mechanism. Part 2 of this series of papers develops a gas-particle partitioning model and presents simulations of SOA formation in single oxidant (e.g., ozonolysis and nitrate radical) and photooxidation experiments. Part 2 examines in detail the role of individual oxidants in consumption of the parent organic, creation of cross-products, and formation of SOA.

Colville, Christopher J.; Griffin, Robert J.

121

Individual Aerosol Particles from Biomass Burning in Southern Africa Compositions and Aging of Inorganic Particles. 2; Compositions and Aging of Inorganic Particles  

NASA Technical Reports Server (NTRS)

Individual aerosol particles collected over southern Africa during the SAFARI 2000 field study were studied using transmission electron microscopy and field-emission scanning electron microscopy. The sizes, shapes, compositions, mixing states, surface coatings, and relative abundances of aerosol particles from biomass burning, in boundary layer hazes, and in the free troposphere were compared, with emphasis on aging and reactions of inorganic smoke particles. Potassium salts and organic particles were the predominant species in the smoke, and most were internally mixed. More KCl particles occur in young smoke, whereas more K2SO4 and KNO3 particles were present in aged smoke. This change indicates that with the aging of the smoke, KCl particles from the fires were converted to K2SO4 and KNO3 through reactions with sulfur- and nitrogen- bearing species from biomass burning as well as other sources. More soot was present in smoke from flaming grass fires than bush and wood fires, probably due to the predominance of flaming combustion in grass fires. The high abundance of organic particles and soluble salts can affect the hygroscopic properties of biomass-burning aerosols and therefore influence their role as cloud condensation nuclei. Particles from biomass burning were important constituents of the regional hazes.

Li, Jia; Posfai, Mihaly; Hobbs, Peter V.; Buseck, Peter R.

2003-01-01

122

Effect of mineral dust on secondary organic aerosol yield and aerosol size in ?-pinene/NOx photo-oxidation  

NASA Astrophysics Data System (ADS)

Although it is a significant contributor to atmospheric particles, the role of mineral dust in secondary organic aerosol (SOA) formation has not been fully recognized. In this study, alumina was chosen as the surrogate to investigate the effect of mineral dust on ?-pinene/NOx photo-oxidation in a 2 m3 smog chamber at 30 °C and 50% relative humidity (RH). Results showed that alumina seeds could influence both the SOA yield and the aerosol size in the photo-oxidation process. Compared to the seed-free system, the presence of alumina seeds resulted in a slight reduction of SOA yield, and also influenced the final concentration of O3 in the chamber. As an important oxidant of ?-pinene, the decrease in O3 concentration could reduce the formation of semi-volatile compounds (SVOCs) and consequently inhibited SOA formation. In addition, the size of aerosol was closely related with the mass loading of alumina seeds. At low alumina concentration, SVOCs condensed onto the pre-existing seed surface and led to aerosol size growth. When alumina concentration exceeded about 5 ?g m-3, SVOC species that condensed to each seed particle were dispersed by alumina seeds, resulting in the decrease in aerosol size.

Liu, Chang; Chu, Biwu; Liu, Yongchun; Ma, Qingxin; Ma, Jinzhu; He, Hong; Li, Junhua; Hao, Jiming

2013-10-01

123

Mechanism of secondary organic aerosol formation from isoprene photooxidation: Identification of precursors to aerosol-phase products  

NASA Astrophysics Data System (ADS)

Isoprene (2-methyl-1,3-butadiene) is the most abundant non-methane hydrocarbon, accounting for ~500 Tg/year of emissions into the atmosphere. Reactions of isoprene can lead to significant secondary organic aerosol (SOA) formation, which has important implications for global climate and local air quality. Chamber photooxidation of isoprene has been shown to produce such aerosol-phase products as 2-methyltetrols and organosulfates under low-NOx conditions, and 2-methylglyceric acid (2-MG) and oligoesters under high-NOx conditions. While these products have been identified to be major aerosol-phase components in both chamber-generated and field aerosol samples, the mechanism by which these products are formed remains poorly understood. In the first part of this study, we probe the effect of seed acidity on the formation of 2-methyltetrols and organosulfates in isoprene low-NOx SOA. This is done by investigating reactive uptake of various intermediate gas-phase oxidation products onto neutral and acidic sulfate aerosols. The second part of this study involves high-NOx photooxidation of methacrolein, a gas-phase oxidation product of isoprene responsible for production of aerosol-phase 2-MG and oligomer products. The experiments are performed in the Caltech dual 28-m3 environmental chambers. The gas-phase products are measured using a chemical ionization mass spectrometer. Filter samples of chamber SOA are analyzed using a variety of mass spectrometry techniques. By comparing the aerosol-phase composition from reactive uptake or photooxidation of intermediates to that from isoprene photooxidation, we elucidate the mechanism by which these major isoprene-SOA products are formed. With a more detailed understanding of SOA formation from isoprene oxidation, the implications for future chamber experiments and ambient SOA production are discussed.

Chan, A. W.; Surratt, J. D.; Eddingsaas, N. C.; Chan, M. N.; Loza, C.; Wennberg, P. O.; Flagan, R. C.; Seinfeld, J.

2009-12-01

124

Volatility of secondary organic aerosol during OH radical induced ageing  

Microsoft Academic Search

The aim of this study was to investigate oxidation of SOA formed from ozonolysis of alpha-pinene and limonene by hydroxyl radicals. This paper focuses on changes of particle volatility, using a Volatility Tandem DMA (VTDMA) set-up, in order to explain and elucidate the mechanism behind atmospheric ageing of the organic aerosol. The experiments were conducted at the AIDA chamber facility

K. Salo; M. Hallquist; Å. M. Jonsson; H. Saathoff; K.-H. Naumann; C. Spindler; R. Tillmann; H. Fuchs; B. Bohn; F. Rubach; Th. F. Mentel; L. Müller; M. Reinnig; T. Hoffmann; N. M. Donahue

2011-01-01

125

Characterization of size-differentiated inorganic composition of aerosols in Mexico City  

NASA Astrophysics Data System (ADS)

Size-differentiated atmospheric aerosol particles were collected during December 2000-October 2001 in Mexico City (19°N, 99°W) using a micro-orifice uniform deposit impactor. Sulfate and ammonium, which were correlated, were major features of the size distributions. The more predominant mode was at 0.32±0.1 ?m, aerodynamic diameter. This peak of concentration is likely the result of condensation of secondary aerosol components from the gas phase. During part of the rainy season (April and June), a larger mode was found at 0.56±0.2 ?m, aerodynamic diameter. This peak of concentration, identified as a droplet mode, is probably the result of aqueous-phase reactions (i.e., oxidation of sulfur dioxide in liquid droplets). During August, the peak of concentration was observed at both size ranges of the accumulation mode. Overall, ion balances were achieved with a small deficit of cations, except for the April and June samples, where a significant amount of excess sulfate was present as a result of moderate-high activity of the neighboring volcano Popocatepetl, as well as ambient conditions that favored production of sulfate (moderate-high relative humidity values). Based on the analysis of the ammonia/sulfate molar ratios, the ammonia concentrations were sufficient to fully neutralize sulfate concentrations, except for the April and June samples. During these months, ammonium bisulfate, letovicite and H 2SO 4(aq) (or a solution of the corresponding ions) were the dominant form of sulfate present in both fine and coarse modes. The acidic nature of these particles (with NH 3/H 2SO 4 molar ratio less than 2) is potentially important in assessing health effects of inhaled particles.

Moya, Mireya; Castro, Telma; Zepeda, Monica; Baez, Armando

126

Glyoxal processing outside clouds: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles  

NASA Astrophysics Data System (ADS)

This study presents a modeling framework based on laboratory data to describe the kinetics of glyoxal reactions in aqueous aerosol particles that form secondary organic aerosol (SOA). Recent laboratory results on glyoxal reactions are reviewed and a consistent set of reaction rate constants is derived that captures the kinetics of glyoxal hydration and subsequent reversible and irreversible reactions in aqueous inorganic and water-soluble organic aerosol seeds to form (a) oligomers, (b) nitrogen-containing products, (c) photochemical oxidation products with high molecular weight. These additional aqueous phase processes enhance the SOA formation rate in particles compared to cloud droplets and yield two to three orders of magnitude more SOA than predicted based on reaction schemes for dilute aqueous phase (cloud) chemistry. The application of this new module in a chemical box model demonstrates that both the time scale to reach aqueous phase equilibria and the choice of rate constants of irreversible reactions have a pronounced effect on the atmospheric relevance of SOA formation from glyoxal. During day time a photochemical (most likely radical-initiated) process is the major SOA formation pathway forming ~5 ?g m-3 SOA over 12 h (assuming a constant glyoxal mixing ratio of 300 ppt). During night time, reactions of nitrogen-containing compounds (ammonium, amines, amino acids) contribute most to the predicted SOA mass; however, the absolute predicted SOA masses are reduced by an order of magnitude as compared to day time production. The contribution of the ammonium reaction significantly increases in moderately acidic or neutral particles (5aerosol, (4) particle surface composition, and (5) particle liquid water content that is mostly determined by the amount and hygroscopicity of aerosol mass and to a lesser extent by the ambient relative humidity. Glyoxal serves as an example molecule, and the conclusions about SOA formation in aqueous particles can serve for comparative studies also of other molecules that form SOA as the result of multiphase chemical processing in aerosol water. This SOA source is currently underrepresented in atmospheric models; if included it is likely to bring SOA predictions (mass and O/C ratio) into better agreement with field observations.

Ervens, B.; Volkamer, R.

2010-05-01

127

Resolving The Primary Or Secondary Origin Of Individual Organic Compounds In Aerosols: Application To The 2- Methyltetrols  

Microsoft Academic Search

Secondary Organic Aerosols (SOA) have been studied for decades, yet the mechanisms contributing to their formation in the atmosphere are still not completely understood. Their description in global and climate models is therefore highly uncertain. Here we present a new analytical method that has been developed to determine the primary or secondary origin of individual organic compounds in atmospheric aerosols

N. J. Gonzalez Cantu; A. Borg-Karlsson; J. Petersson Redeby; B. Noziere; R. Krejci; P. P. Artaxo

2009-01-01

128

Formation of Secondary Organic Aerosols Through Photooxidation of Isoprene  

Microsoft Academic Search

Detailed organic analysis of natural aerosols from the Amazonian rain forest showed considerable quantities of previously unobserved polar organic compounds, which were identified as a mixture of two diastereoisomeric 2-methyltetrols: 2-methylthreitol and 2-methylerythritol. These polyols, which have the isoprene skeleton, can be explained by OH radical-initiated photooxidation of isoprene. They have low vapor pressure, allowing them to condense onto preexisting

Magda Claeys; Bim Graham; Gyorgy Vas; Wu Wang; Reinhilde Vermeylen; Vlada Pashynska; Jan Cafmeyer; Pascal Guyon; Meinrat O. Andreae; Paulo Artaxo; Willy Maenhaut

2004-01-01

129

Cloud forming potential of oligomers relevant to secondary organic aerosols  

NASA Astrophysics Data System (ADS)

hygroscopic growth factor (HGF) and cloud condensation nuclei (CCN) activity are measured for surrogates that mimic atmospherically relevant oligomers, including glyoxal trimer dihydrate, methyl glyoxal trimer dihydrate, sucrose, methyl glyoxal mixtures with sulfuric acid and glycolic acid, and 2,4-hexandienal mixtures with sulfuric acid and glycolic acid. For the single-component aerosols, the measured HGF ranges from 1.3 to 1.4 at a relative humidity of 90%, and the hygroscopicity parameter (?) is in the range of 0.06 to 0.19 on the basis of the measured CCN activity and 0.13 to 0.22 on the basis of the measured HGF, compared to the calculated values of 0.08 to 0.16. Large differences exist in the ? values derived using the measured HGF and CCN data for the multi-component aerosols. Our results reveal that, in contrast to the oxidation process, oligomerization decreases particle hygroscopicity and CCN activity and provides guidance for analyzing the organic species in ambient aerosols.

Xu, Wen; Guo, Song; Gomez-Hernandez, Mario; Zamora, Misti L.; Secrest, Jeremiah; Marrero-Ortiz, Wilmarie; Zhang, Annie L.; Collins, Don R.; Zhang, Renyi

2014-09-01

130

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

PubMed Central

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

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

131

Emission, oxidation, and secondary organic aerosol formation of volatile organic compounds as observed at Chebogue Point,  

E-print Network

Emission, oxidation, and secondary organic aerosol formation of volatile organic compounds, methanol, and MEK measured by other in situ instrumentation. On the other hand these oxidized volatile show these compounds match the oxidation products of isoprene observed in smog chamber studies, and we

Silver, Whendee

132

SEMI-VOLATILE SECONDARY AEROSOLS IN URBAN ATMOSPHERES: MEETING A MEASURED CHALLENGE  

EPA Science Inventory

This presentation compares the results from various particle measurement methods as they relate to semi-volatile secondary aerosols in urban atmospheres. The methods include the PM2.5 Federal Reference Method; Particle Concentrator - BYU Organic Sampling System (PC-BOSS); the Re...

133

Effects of chemical aging on global secondary organic aerosol using the volatility basis set approach  

E-print Network

, regional climate implications. For example, the regional DRF change due to chemical aging of SOAEffects of chemical aging on global secondary organic aerosol using the volatility basis set, School of Earth and Environmental Science, Seoul National University, Seoul 151-747, Republic of Korea b

Park, Rokjin

134

Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected  

Microsoft Academic Search

The atmospheric chemistry of volatile organic compounds (VOCs) in urban areas results in the formation of ‘photochemical smog’, including secondary organic aerosol (SOA). State-of-the-art SOA models parameterize the results of simulation chamber experiments that bracket the conditions found in the polluted urban atmosphere. Here we show that in the real urban atmosphere reactive anthropogenic VOCs (AVOCs) produce much larger amounts

Rainer Volkamer; Jose L. Jimenez; Federico San Martini; Katja Dzepina; Qi Zhang; Dara Salcedo; Luisa T. Molina; Douglas R. Worsnop; Mario J. Molina

2006-01-01

135

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

Microsoft Academic Search

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

James D Blando; Barbara J Turpin

2000-01-01

136

Measurement of Optical Properties of Organic and Mixed Organic/ Inorganic Laboratory Aerosols at Relative Humidities between 8 and 95%  

NASA Astrophysics Data System (ADS)

Relative humidity (RH) affects the liquid water content of an aerosol, altering its scattering and absorption of visible light, which is important for aerosol effects on visibility and climate. Particle light extinction, light scattering and light absorption coefficient values are reported here for laboratory-generated inorganic and organic carbon (OC) aerosols at RH values between 8% and 95%. Light scattering was measured with a nephelometer, light extinction was measured with an extinction cell and light absorption was determined based on the difference between those two values at three visible wavelengths (467 nm, 530 nm and 660 nm). The instrumentation was benchmarked with non-absorbing ammonium sulfate, absorbing polystyrene microspheres (PSMs) and absorbing nigrosin aerosol under controlled RH conditions. Agreement between dry measured scattering and extinction coefficients for ammonium sulfate was achieved within 3%. Optical closure with modeled scattering values based on measured ammonium sulfate particle size distributions was achieved within 7%. Measured single scattering albedo for dry absorbing PSMs agreed within 0.02 with the literature value. Light absorption by nigrosin increased by a factor of 1.24 +/-0.06 at all wavelengths as RH increased from 38 to 95%. Light absorption of OC aerosol that was generated from wood pyrolysis demonstrated enhancements of 2.2 +/- 0.7 and 2.7 +/- 1.2 between 32 and 95% RH at the wavelengths of 467 and 530 nm, but no absorption was detected at 660 nm. A spectral dependence of light absorption by OC was observed with absorption increasing from 530 nm towards the 467 nm wavelength, consistent with previously reported ex situ measurements of filter extracts. Current work focuses on the measurement of optical properties as a function of RH for OC wood pyrolysis aerosol mixed with ammonium sulfate. Additionally optical closure is evaluated between measured and modeled results.

Brem, B.; Mena, F. C.; Chen, Y.; Bond, T. C.; Rood, M. J.

2011-12-01

137

Secondary organic aerosol formation through fog processing of VOCs  

NASA Astrophysics Data System (ADS)

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.

Herckes, P.; Hutchings, J. W.

2010-07-01

138

Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

Emissions of biogenic volatile organic compounds (BVOC) have changed in the past millennium due to changes in land use, temperature and CO2 concentrations. Recent model reconstructions of BVOC emissions over the past millennium predicted changes in dominant secondary organic aerosol (SOA) producing BVOC classes (isoprene, monoterpenes and sesquiterpenes). The reconstructions predicted that global isoprene emissions have decreased (land-use changes to crop/grazing land dominate the reduction), while monoterpene and sesquiterpene emissions have increased (temperature increases dominate the increases); however, all three show regional variability due to competition between the various influencing factors. These BVOC changes have largely been anthropogenic in nature, and land-use change was shown to have the most dramatic effect by decreasing isoprene emissions. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on SOA formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS global aerosol microphysics model. With anthropogenic emissions (e.g. SO2, NOx, primary aerosols) held at present day values and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of >25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in direct plus indirect aerosol radiative effect of >0.5 W m-2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m-2 and the global mean cloud-albedo aerosol indirect effect of between -0.008 and -0.056 W m-2. This change in aerosols, and the associated radiative forcing, could be a~largely overlooked and important anthropogenic aerosol effect on regional climates.

D'Andrea, S. D.; Acosta Navarro, J. C.; Farina, S. C.; Scott, C. E.; Rap, A.; Farmer, D. K.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

2014-10-01

139

Secondary Aerosol Formation over the ESCOMPTE Area: Results from airborne Aerosol and Trace Gas Measurements  

NASA Astrophysics Data System (ADS)

From June 10th to July 14th 2001, the ESCOMPTE campaign took place in the Marseille-Berre area in Southern France. The goal of the campaign was to produce a high quality 3-D data base from emissions, transport and air composition measurements during urban photochemical pollution episodes at the meso-scale. The CAATER AEROPLUM project was embedded within this international field campaign. AEROPLUM aimed at mapping size distributions of aerosols and photo-oxidants in the mixed layer over the ESCOMPTE domain, using the ARAT Fokker 27 as measurement platform. Aircraft sub-micrometer aerosol measurements are validated during overpasses against ground-based measurements, carried out with similar instrumentation. We will present and discuss data during periods of seabreeze, transporting coastal industrial and urban pollution land-inwards. This leads to intense photochemical activity, evidenced by elevated O_3 concentrations and aerosol levels.

van Dingenen, R.; Martins-Dos Santos, S.; Putaud, J. P.; Allet, C.; Bretton, E.; Perros, P.

2003-04-01

140

Simulating Inorganic Aerosol Components Using ISORROPIA II in a Chemical Transport Model (PMCAMx) - Evaluation for the MILAGRO Campaign 2006 in Mexico City  

NASA Astrophysics Data System (ADS)

Aerosols have a significant role in the atmosphere having adverse impacts on human health and directly affecting air quality, visibility and climate change. One of the most challenging tasks for the available models is the prediction of the partitioning of the semivolatile inorganic aerosol components (ammonia, nitric acid, hydrochloric acid, etc) between the gas and aerosol phases. Moreover, the effects of mineral aerosols in the atmosphere remain largely unquantified. As a result, most current models have serious difficulties in reproducing the observed particulate nitrate and chloride concentrations. The aerosol thermodynamic model ISORROPIA has been improved as it now simulates explicitly the chemistry of Ca, Mg, and K salts and is linked to PMCAMx (Gaydos et al., 2007). PMCAMx also includes the inorganic aerosol growth module (Gaydos et al., 2003; Koo et al., 2003a) and the aqueous-phase chemistry module (Fahey and Pandis, 2001). The hybrid approach (Koo et al., 2003b) for modeling aerosol dynamics is applied in order to accurately simulate the inorganic components in coarse mode. This approach assumes that the smallest particles are in equilibrium while the condensation/evaporation equation is solved for the larger ones. PMCAMx is applied in Mexico City Metropolitan Area (MCMA) covering a 180x180x6 km region. The emission inventory used has as a starting point the MCMA 2004 official emissions inventory (CAM, 2006) and includes more accurate dust and NaCl emissions. The March 2006 dataset (MILAGRO Campaign) is used to evaluate the inorganic aerosol module of PMCAMx in order to test our understanding of aerosol thermodynamics and the equilibrium assumption. Gaydos, T., Pinder, R., Koo, B., Fahey, ?., Yarwood, G., and Pandis, S. N., (2007). Development and application of a three-dimensional Chemical Transport Model, PMCAMx. Atmospheric Environment, 41, 2594- 2611. Gaydos, T., Koo, B., and Pandis, S. N., (2003). Development and application of an efficient moving sectional approach for the solution of the atmospheric aerosol condensation/evaporation equations. Atmospheric Environment, 37, 3303-3316. Fahey, K. and Pandis, S. N., (2001). Optimizing model performance: variable size resolution in cloud chemistry modelling. Atmospheric Environment 35, 4471-4478. Koo, B., Pandis S. N., and Ansari, A. (2003a). Integrated approaches to modelling the organic and inorganic atmospheric aerosol components. Atmospheric Environment, 37, 4757-4768. Koo, B., Gaydos, T.M., Pandis, S.N., (2003b). Evaluation of the equilibrium, hybrid, and dynamic aerosol modeling approaches. Aerosol Science and Technology 37, 53-64.

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

2007-12-01

141

Inorganic trace element content of aerosols at puy de Dôme, France  

NASA Astrophysics Data System (ADS)

The puy de Dôme research station is located at 1465 m above sea level in central France (45° 46' N, 2° 57' E, 1465 m a.s.l.). The station is surrounded by a protected area where agriculture and forests are predominant. The city of Clermont-Ferrand (150 000 inhabitants) is located 16 km east of the station. At the pdD site, the dominant westerly winds bring background or aged air masses. Despite its relatively low elevation, long-term records of gases and meteorological parameters indicate that in winter the site is mainly located in the free troposphere. Aerosol physical and chemical properties (particle size, black carbon mass), and gas-phase mixing ratios (SO2, CO, CO2, O3, NO, and NO2) are measured continuously throughout the year. Since October 2011, inorganic trace element content of aerosols is also monitored weekly. Precisely measured air volumes (typically from 15 to 20 m3) are filtered during two consecutive days and two consecutive nights on high purity teflon filters (47 mm diameter and 1.0 micrometer porosity). The Teflon filters are leached in savillex beakers using HNO3(0.4M) - HF (0.05M) and trace elements concentrations are analyzed by ICPMS (Agilent 7500, Laboratoire Magmas et Volcans). Preliminary data were analyzed in logarithmic plots sorting elements according to their decreasing abundance in the upper continental crust. A first group of elements (Al, Na, Fe, Mg, Ti, Mn, Ba, Sr, Zr, V, Cr, Rb, Li, Y, Ga, Co, Sc, Nb, Th, Hf, Cs, U, Be, Ta and Rare Earth Elements) shows a progressive decreasing trend, which suggests a crustal origin. A second group of elements (Zn, Ni, Cu, B, Pb, As, Sn, W, Ge, Mo, Tl, Sb, Bi, Se, Cd, In and Ag) shows strong positive anomalies that superimpose on the smooth trend. With the exception of Ni, all elements from this second group are volatile to some degree. The excess element concentration (i.e., unsupported by crustal input) decreases in the following order: Zn (7.75 ng/m3), B (1.2 ng/m3), Ni (0.44 ng/m3), Pb (0.34 ng/m3), Sn and Ag (0.18 ng/m3), W (0.13 ng/m3), Sb, As, Mo, Bi, Se, Cd, Ge (<0.1 ng/m3). Over the limited time-period yet investigated, the large variations of concentration ratios, such as Al/Ti (5 to 338) and Zn/Pb (0.5 to 196), point to important and rapid changes in element sources. These changes are currently examined in the light of air mass back-trajectories.

Vlastelic, I.; Sellegri, K.; Colomb, A.; Suchroski, K.; Bouvier, L.; Nauret, F.

2012-04-01

142

A phase equilibrium model for atmospheric aerosols containing inorganic electrolytes and organic compounds (UHAERO), with application to dicarboxylic acids  

NASA Astrophysics Data System (ADS)

Computation of phase and chemical equilibria of water-organic-inorganic mixtures is of significant interest in atmospheric aerosol modeling. A new version of the phase partitioning model, named UHAERO, is presented here, which allows one to compute the phase behavior for atmospheric aerosols containing inorganic electrolytes and organic compounds. The computational implementation of the model is based on standard minimization of the Gibbs free energy using a primal-dual method, coupled to a Newton iteration. Water uptake and deliquescence properties of mixtures of aqueous solutions of salts and dicarboxylic acids, including oxalic, malonic, succinic, glutaric, maleic, malic, or methyl succinic acids, are based on a hybrid thermodynamic approach for the modeling of activity coefficients (Clegg and Seinfeld, 2006a, 2006b). UHAERO currently considers ammonium salts and the neutralization of dicarboxylic acids and sulfuric acid. Phase diagrams for sulfate/ammonium/water/dicarboxylic acid systems are presented as a function of relative humidity at 298.15 K over the complete space of compositions.

Amundson, N. R.; Caboussat, A.; He, J. W.; Martynenko, A. V.; Seinfeld, J. H.

2007-12-01

143

Climate-relevant physical properties of molecular constituents for isoprene-derived secondary organic aerosol material  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) particles, formed from gas-phase biogenic volatile organic compounds (BVOCs), contribute large uncertainties to the radiative forcing that is associated with aerosols in the climate system. Reactive uptake of surface-active organic oxidation products of BVOCs at the gas-aerosol interface can potentially decrease the overall aerosol surface tension and therefore influence their propensity to act as cloud condensation nuclei (CCN). Here, we synthesize and measure some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products ?-, ?-, and cis- and trans-?-IEPOX (isoprene epoxide), as well as syn- and anti-2-methyltetraol. Following viscosity measurements, we use octanol-water partition coefficients to quantify the relative hydrophobicity of the oxidation products while dynamic surface tension measurements indicate that aqueous solutions of ?- and trans-?-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that trans-?-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers.

Upshur, M. A.; Strick, B. F.; McNeill, V. F.; Thomson, R. J.; Geiger, F. M.

2014-10-01

144

Individual aerosol particles from biomass burning in southern Africa: 2, Compositions and aging of inorganic particles  

Microsoft Academic Search

(1) Individual aerosol particles collected over southern Africa during the SAFARI 2000 field study were studied using transmission electron microscopy and field-emission scanning electron microscopy. The sizes, shapes, compositions, mixing states, surface coatings, and relative abundances of aerosol particles from biomass burning, in boundary layer hazes, and in the free troposphere were compared, with emphasis on aging and reactions of

Jia Li; Mihaly Posfai; Peter V. Hobbs; Peter R. Buseck

2003-01-01

145

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

Microsoft Academic Search

Secondary organic aerosol (SOA) accounts for a significant fraction of\\u000a ambient tropospheric aerosol and a detailed knowledge of the formation,\\u000a properties and transformation of SOA is therefore required to evaluate\\u000a its impact on atmospheric processes, climate and human health. The\\u000a chemical and physical processes associated with SOA formation are\\u000a complex and varied, and, despite considerable progress in recent years,\\u000a a

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

2009-01-01

146

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions  

PubMed Central

The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models. PMID:22869714

Donahue, Neil M.; Henry, Kaytlin M.; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Spindler, Christian; Bohn, Birger; Brauers, Theo; Dorn, Hans P.; Fuchs, Hendrik; Tillmann, Ralf; Wahner, Andreas; Saathoff, Harald; Naumann, Karl-Heinz; Möhler, Ottmar; Leisner, Thomas; Müller, Lars; Reinnig, Marc-Christopher; Hoffmann, Thorsten; Salo, Kent; Hallquist, Mattias; Frosch, Mia; Bilde, Merete; Tritscher, Torsten; Barmet, Peter; Praplan, Arnaud P.; DeCarlo, Peter F.; Dommen, Josef; Prévôt, Andre S.H.; Baltensperger, Urs

2012-01-01

147

Inorganic and carbonaceous aerosols during the Southern African Regional Science Initiative (SAFARI 2000) experiment: Chemical characteristics, physical properties, and emission data for smoke from African biomass burning  

Microsoft Academic Search

We collected filter samples of the atmospheric aerosol during the Southern African Regional Science Initiative (SAFARI 2000) experiment onboard the UK Met Office C-130 aircraft. The main operational area was the Atlantic Ocean offshore of Namibia and Angola, where biomass-smoke haze at least 1–2 days old was widespread. The size-fractionated aerosol samples were analyzed for the major inorganic ions, carbonaceous

P. Formenti; W. Elbert; W. Maenhaut; J. Haywood; S. Osborne; M. O. Andreae

2003-01-01

148

Inorganic and carbonaceous aerosols during the Southern African Regional Science Initiative (SAFARI 2000) experiment: Chemical characteristics, physical properties, and emission data for smoke from African biomass burning  

Microsoft Academic Search

We collected filter samples of the atmospheric aerosol during the Southern African Regional Science Initiative (SAFARI 2000) experiment onboard the UK Met Office C-130 aircraft. The main operational area was the Atlantic Ocean offshore of Namibia and Angola, where biomass-smoke haze at least 1-2 days old was widespread. The size-fractionated aerosol samples were analyzed for the major inorganic ions, carbonaceous

P. Formenti; W. Elbert; W. Maenhaut; J. Haywood; S. Osborne; M. O. Andreae

2003-01-01

149

Analysis of secondary organic aerosols from ozonolysis of isoprene by proton transfer reaction mass spectrometry  

NASA Astrophysics Data System (ADS)

To understand the mechanism of formation of the secondary organic aerosols (SOAs) produced by the ozonolysis of isoprene, proton transfer reaction mass spectrometry (PTR-MS) was used to identify the semi-volatile organic compounds (SVOCs) produced in both the gaseous and the aerosol phases and to estimate the gas-aerosol partitioning of each SVOC in chamber experiments. To aid in the identification of the SVOCs, the products were also studied with negative ion-chemical ionization mass spectrometry (NI-CIMS), which can selectively detect carboxylic acids and hydroperoxides. The gaseous products were observed by on-line PTR-MS and NI-CIMS, whereas the SVOCs in SOAs collected on a filter were vaporized by heating the filter and were then analysed by off-line PTR-MS and NI-CIMS. The formation of oligomeric hydroperoxides involving a Criegee intermediate as a chain unit was observed in both the gaseous and the aerosol phases by NI-CIMS. PTR-MS also detected oligomeric hydroperoxides as protonated molecules from which a H2O molecule was eliminated, [M-OH]+. In the aerosol phase, oligomers involving formaldehyde and methacrolein as chain units were observed by PTR-MS in addition to oligomeric hydroperoxides. The gas-aerosol partitioning of each component was calculated from the ion signals in the gaseous and aerosol phases measured by PTR-MS. From the gas-aerosol partitioning, the saturated vapour pressures of the oligomeric hydroperoxides were estimated. Measurements by a fast-mobility-particle-sizer spectrometer revealed that the increase of the number density of the particles was complete within a few hundred seconds from the start of the reaction.

Inomata, Satoshi; Sato, Kei; Hirokawa, Jun; Sakamoto, Yosuke; Tanimoto, Hiroshi; Okumura, Motonori; Tohno, Susumu; Imamura, Takashi

2014-11-01

150

The formation of secondary organic aerosol from the isoprene + OH reaction in the absence of NOx  

NASA Astrophysics Data System (ADS)

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 chamber operated in a steady-state mode permitting measurements of moderately low aerosol levels. GC-MS analysis was conducted to measure methyl butenediols in the gas phase and polyols in the aerosol phase. Analyses were made to obtain several bulk aerosol parameters from the reaction including values for the organic mass to organic carbon ratio, the effective enthalpy of vaporization (?Hvapeff), organic peroxide fraction, and the aerosol yield. The gas phase analysis showed the presence of methacrolein, methyl vinyl ketone, and four isomers of the methyl butenediols. These gas-phase compounds may serve as precursors for one or more of several compounds detected in the aerosol phase including 2-methylglyceric acid, three 2-methyl alkenetriols, and two 2-methyl tetrols. In contrast to most previous studies, the 2-methyl tetrols (and the 2-methyl alkenetriols) were found to form in the absence of acidic sulfate aerosol. However, reaction conditions did not favor the production of HO2 radicals, thus allowing RO2+RO2 reactions to proceed more readily than if higher HO2 levels had been generated. SOA/SOC (i.e. OM/OC) was found to average 1.9 in the absence of NOx. The effective enthalpy of vaporization was measured as 38.6 kJ mol-1, consistent with values used previously in modeling studies. The yields in this work (using an independent technique than used previously) are lower than those of Kroll et al. (2006) for similar aerosol masses. SOC yields reported in this work range from 0.5-1.4% for carbon masses between 17 and 49 ?gC m-3.

Kleindienst, T. E.; Lewandowski, M.; Offenberg, J. H.; Jaoui, M.; Edney, E. O.

2009-09-01

151

The formation of secondary organic aerosol from the isoprene + OH reaction in the absence of NOx  

NASA Astrophysics Data System (ADS)

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 chamber operated in a steady-state mode permitting measurements of moderately low aerosol levels. GC-MS analysis was conducted to measure methyl butenediols in the gas phase and polyols in the aerosol phase. Analyses were made to obtain several bulk aerosol parameters from the reaction including values for the organic mass to organic carbon ratio, the effective enthalpy of vaporization (?Hvapeff), the organic peroxide fraction, and the aerosol yield. The gas phase analysis showed the presence of methacrolein, methyl vinyl ketone, and four isomers of the methyl butenediols. These gas-phase compounds may serve as precursors for one or more of several compounds detected in the aerosol phase including 2-methylglyceric acid, three 2-methyl alkenetriols, and two 2-methyl tetrols. In contrast to most previous studies, the 2-methyl tetrols (and the 2-methyl alkenetriols) were found to form in the absence of acidic sulfate aerosol. A re-evaluation of field samples in Research Triangle Park, North Carolina, during the summers of 2000 and 2001 indicated in the presence of the methyl butenediols from gas-phase denuder samples taken at the time. SOA/SOC (i.e., OM/OC) was found to average 1.9 in the absence of NOx. The effective enthalpy of vaporization was measured as 38.6 kJ mol-1, consistent with values that have previously been used in modeling studies. The yields in this work (using an independent technique than that previous) are lower than those of Kroll et al. (2006) for similar aerosol masses. SOC yields reported in this work range from 0.5-1.4% for carbon masses between 17 and 49 ?gC m-3.

Kleindienst, T. E.; Lewandowski, M.; Offenberg, J. H.; Jaoui, M.; Edney, E. O.

2009-04-01

152

Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multi-layer model ADCHAM  

NASA Astrophysics Data System (ADS)

We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: (1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), (2) the slow and almost particle size independent evaporation of ?-pinene secondary organic aerosol (SOA) particles, and (3) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed ?-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. These salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating ?-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar like amorphous phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if low-volatility and viscous oligomerized SOA material accumulates in the particle surface layer upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass transfer limited uptake of condensable organic compounds onto wall deposited particles or directly onto the Teflon chamber walls of smog chambers can have profound influence on the observed SOA formation. During the early stage of the SOA formation the wall deposited particles and walls themselves serve as a SOA sink from the air to the walls. However, at the end of smog chamber experiments the semi-volatile SOA material may start to evaporate from the chamber walls. With these three model applications, we demonstrate that several poorly quantified processes, i.e. mass transport limitations within the particle phase, oligomerization, heterogeneous oxidation, organic salt formation, and chamber wall effects can have substantial influence on the SOA formation, lifetime, chemical and physical particle properties, and their evolution. In order to constrain the uncertainties related to these processes, future experiments are needed where as many of the influential variables as possible are varied. ADCHAM can be a valuable model tool in the design and analysis of such experiments.

Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, D.; Rusanen, A.; Boy, M.; Swietlicki, E.; Svenningsson, B.; Zelenyuk, A.; Pagels, J.

2014-01-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

154

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

PubMed

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

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

2012-08-01

155

Secondary organic aerosol formation initiated from reactions between ozone and surface-sorbed squalene  

NASA Astrophysics Data System (ADS)

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.

Wang, Chunyi; Waring, Michael S.

2014-02-01

156

Evidence for Secondary Organic Aerosol Formation Involving Liquid-Phase Partitioning to Haze Particles in Summertime Atlanta  

NASA Astrophysics Data System (ADS)

Simultaneous online (10 min) measurements of water-soluble organic carbon in the particle (WSOCp) and gas (WSOCg) phase were made in Atlanta to characterize the gas/particle partitioning of WSOC in an urban environment. The data set is substantial (n=10994) spanning continuous measurements from May to September 2007. During this period WSOCp was a large component of PM2.5, and on average accounted for 70% of Organic Carbon (OC, gC per gC). The WSOC partitioning parameter, Fp, which represents the fraction of total WSOC (WSOCg + WSOCp) in the particle phase, was found to depend on aerosol liquid water content, and the WSOCp and NOx concentration. Overall, these results provide a detailed overview of WSOC partitioning behavior in the summertime in an urban region dominated by biogenic emissions. WSOC gas/particle partitioning showed a strong RH dependence that was attributed to particulate liquid water. At elevated RH (> 70%), a significant increase in WSOC partitioning to the particle phase was observed and followed the predicted water uptake by the fine particle inorganic components, resulting in an apparent linear dependence between WSOC partitioning and particle liquid water concentration. The increase in WSOCp concentrations from this effect was significant, and it offers compelling evidence that secondary organic aerosol formation involving partitioning to liquid water associated with fine haze particles is an important aerosol source. Partitioning was positively correlated with WSOCp for concentrations below roughly 4 ? g C m-3, but showed little dependence at higher WSOCp concentrations. In contrast, no relationship between Fp and total OC aerosol mass was found for any OC concentration. Chemical similarity between the absorbing organic phase and partitioning compounds appears to be important. NOx concentrations also affected Fp. On average, lower NOx concentrations were associated with higher Fp values, however, the Fp - NOx relationship may not have been linked to the gas/particle partitioning process, but may instead result from the influence NOx imparts on the product distribution of volatile organic compound oxidation.

Hennigan, C. J.; Bergin, M. H.; Dibb, J. E.; Weber, R. J.

2008-12-01

157

Secondary Organic Aerosol Formation from m-Xylene in the Absence of NOx  

SciTech Connect

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.

Song, Chen; Na, Kwangsam; Warren, Bethany; Malloy, Quentin; Cocker, David R.

2007-11-01

158

Secondary organic aerosol formation from the photo-oxidation of benzene  

NASA Astrophysics Data System (ADS)

The production of condensate compounds from the degradation of benzene by OH radical chemistry was studied. Secondary organic aerosol (SOA) formation was investigated in the EUPHORE ( European Photoreactor) simulation chambers. Experiments were performed under different OH-production conditions - addition of H 2O 2, NO or HONO -, in a high-volume reactor, with natural light and in the absence of seed aerosols. The consumption of precursor/reagents, the formation of gas-phase and particulate-phase products and the temporal evolution of aerosol were monitored. Several aerosol physical properties - mass concentration, overall aerosol yield, particle size distribution and density - were determined and found to be clearly dependent on OH radical production and NO x concentrations. Furthermore, the use of one and/or two products gas-particle partitioning absorption models allowed us to determine the aerosol yield curves. The SOA yield ranged from 1.6 to 9.7 %, with higher SOA formation under low-NO x conditions. Chemical characterization of the SOA was carried out, determining multi-oxygenated condensed organic compounds by a method based on the gas chromatography-mass spectrometry technique. Several ring-retaining and ring-cleavage products were identified and quantified. The compounds with the highest percentage contribution to the total aerosol mass were 4-nitrobenzene-1,2-diol, butenedioic acid, succinic acid and trans-trans-muconic. In addition, a multigenerational study was performed comparing with the photo-oxidations of phenol and catechol. The results showed that although the mass concentration of SOA produced was different, the physical and chemical properties were quite similar. Finally, we suggest a general mechanism to describe how changes in benzene degradation pathways - rate of OH generation and concentration of NO x - could justify the variation in SOA production and properties.

Borrás, Esther; Tortajada-Genaro, Luis Antonio

2012-02-01

159

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

160

Emissions of Black Carbon, Organic, and Inorganic Aerosols From Biomass Burning in North America and Asia in 2008  

NASA Technical Reports Server (NTRS)

Reliable assessment of the impact of aerosols emitted from boreal forest fires on the Arctic climate necessitates improved understanding of emissions and the microphysical properties of carbonaceous (black carbon (BC) and organic aerosols (OA)) and inorganic aerosols. The size distributions of BC were measured by an SP2 based on the laser-induced incandescence technique on board the DC-8 aircraft during the NASA ARCTAS campaign. Aircraft sampling was made in fresh plumes strongly impacted by wildfires in North America (Canada and California) in summer 2008 and in those transported from Asia (Siberia in Russia and Kazakhstan) in spring 2008. We extracted biomass burning plumes using particle and tracer (CO, CH3CN, and CH2Cl2) data. OA constituted the dominant fraction of aerosols mass in the submicron range. The large majority of the emitted particles did not contain BC. We related the combustion phase of the fire as represented by the modified combustion efficiency (MCE) to the emission ratios between BC and other species. In particular, we derived the average emission ratios of BC/CO = 2.3 +/- 2.2 and 8.5 +/- 5.4 ng/cu m/ppbv for BB in North America and Asia, respectively. The difference in the BC/CO emission ratios is likely due to the difference in MCE. The count median diameters and geometric standard deviations of the lognormal size distribution of BC in the BB plumes were 136-141 nm and 1.32-1.36, respectively, and depended little on MCE. These BC particles were thickly coated, with shell/core ratios of 1.3-1.6. These parameters can be used directly for improving model estimates of the impact of BB in the Arctic.

Kondo, Y.; Matsui, H.; Moteki, N.; Sahu, L.; Takegawa, N.; Kajino, M.; Zhao, Y.; Cubison, M. J.; Jimenez, J. L.; Vay, S.; Diskin, G. S.; Anderson, B.; Wisthaler, A.; Mikoviny, T.; Fuelberg, H. E.; Blake, D. R.; Huey, G.; Weinheimer, A. J.; Knapp, D. J.; Brune, W. H.

2011-01-01

161

Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide  

Microsoft Academic Search

Aerosols produced over forests impair visibility and may affect climate by scattering and absorbing solar radiation and by serving as cloud condensation nuclei. Here, we introduce, to our knowledge, a new route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, methacrolein and methacrylic acid, namely, multiphase acid-catalysed oxidation with hydrogen peroxide, a perfect analogue to atmospheric

Magda Claeys; Wu Wang; Alina C Ion; Ivan Kourtchev; András Gelencsér; Willy Maenhaut

2004-01-01

162

Spatial distribution and size evolution of particles in Asian outflow: Significance of primary and secondary aerosols during ACE-Asia  

E-print Network

formation and condensational growth during the Asian Pacific Regional Aerosol Characterization ExperimentSpatial distribution and size evolution of particles in Asian outflow: Significance of primary measurements above the Yellow Sea, East China Sea, and Sea of Japan revealed synoptic-scale secondary aerosol

163

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

E-print Network

Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2Methyl-3-Buten-2-ol, Pasadena, California 91125, United States *S Supporting Information ABSTRACT: 2-Methyl-3-buten-2-ol (MBO

Silver, Whendee

164

MOLECULAR SPECIATION OF SECONDARY ORGANIC AEROSOL FROM PHOTOOXIDATION OF THE HIGHER ALKENES: 1-OCTENE AND 1-DECENE. (R824970)  

EPA Science Inventory

Outdoor smog chamber photooxidations to determine the molecular composition of secondary organic aerosol (SOA) from 1-octene and 1-decene in sunlight-irradiated hydrocarbon-NO x mixtures are reported. The observed products are consistent with the current under...

165

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...

166

Formation of Secondary Particulate Matter by Reactions of Gas Phase Hexanal with Sulfate Aerosol Particles  

NASA Astrophysics Data System (ADS)

The formation of secondary particulate matter from the atmospheric oxidation of organic compounds can significantly contribute to the particulate burden, but the formation of organic secondary particulate matter is poorly understood. One way of producing organic secondary particulate matter is the oxidation of hydrocarbons with seven or more carbon atoms to get products with low vapor pressure. However, several recent reports suggest that relatively low molecular weight carbonyls can enter the particle phase by undergoing heterogeneous reactions. This may be a very important mechanism for the formation of organic secondary particulate matter. Atmospheric aldehydes are important carbonyls in the gas phase, which form via the oxidation of hydrocarbons emitted from anthropogenic and biogenic sources. In this poster, we report the results on particle growth by the heterogeneous reactions of hexanal. A 5 L Continuous Stirred Tank Reactor (CSTR) is set up to conduct the reactions in the presence of seed aerosol particles of deliquesced ammonia bisulfate. Hexanal is added into CSTR by syringe pump, meanwhile the concentrations of hexanal are monitored with High Pressure Liquid Chromatograph (HPLC 1050). A differential Mobility Analyzer (TSI 3071) set to an appropriate voltage is employed to obtain monodisperse aerosols, and another DMA associated with a Condensation Nuclear Counter (TSI 7610) is used to measure the secondary particle size distribution by the reaction in CSTR. This permits the sensitive determination of particle growth due to the heterogeneous reaction, very little growth occurs when hexanal added alone. Results for the simultaneous addition of hexanal and alcohols will also be presented.

Zhang, J.

2003-12-01

167

No evidence for acid-catalyzed secondary organic aerosol formation in power plant plumes over metropolitan Atlanta, Georgia  

E-print Network

metropolitan Atlanta, Georgia R. E. Peltier,1 A. P. Sullivan,1 R. J. Weber,1 A. G. Wollny,2,3 J. S. Holloway,2-soluble fraction of fine PM organic carbon (WSOC) and inorganic salt composition in the Atlanta, GA region were are not likely a significant contributor to the ambient aerosol mass loading in Atlanta and the surrounding

Weber, Rodney

168

Secondary aerosol formation through photochemical reactions estimated by using air quality monitoring data in Taipei City from 1994 to 2003  

NASA Astrophysics Data System (ADS)

Analyses of diurnal patterns of PM 10 in Taipei City have been performed in this study at different daily ozone maximum concentrations (O 3,max) from 1994 to 2003. In order to evaluate secondary aerosol formation at different ozone levels, CO was used as a tracer of primary aerosol, and O 3,max was used as an index of photochemical activity. Results show that when O 3,max exceeds 120 ppb, the highest photochemical formation of secondary aerosol can be found at 15:00 (local time). The produced secondary aerosol is estimated to contribute 30 ?g m -3 (43%) of PM 10 concentration, and about 77% of the estimated secondary PM 10 is composed of PM 2.5. The estimated maximum concentration of secondary aerosol occurs 2-3 h later than the maximum ozone concentration. As revealed in an O 3 episode, PM 10 and PM 2.5 vary consistently with O 3 at daytime, which suggests that they are mostly secondary aerosols produced from photochemical reactions. Data collected from Taipei aerosol supersite in 2002 indicates that for all O 3 levels, summertime PM 2.5 is composed of 23%, 20%, 9%, and 7% of organic carbon, sulfate, nitrate, and elemental carbon, respectively. Aerosol number and volume size spectra are dominated by submicron particles either from pollution transport or photochemical reactions. Secondary PM 10 concentrations show increasing tendencies for the time between 15:00 and 19:00 from 1994-1996 to 2001-2003. This reveals that the abatement of secondary PM 10 becomes more important after pronounced primary PM 10 reduction in a metropolis.

Chang, Shuenn-Chin; Lee, Chung-Te

169

Determination of Secondary Organic Aerosol Products from the Photooxidation of Toluene and their Implications in Ambient PM 2.5  

Microsoft Academic Search

A 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 inthe dynamic mode and collecting submicron secondary organic aerosol samples through a sampling train that consisted of an XAD denuder and a ZefluorTM filter. Oxidation products in

T. E. Kleindienst; T. S. Conver; C. D. McIver; E. O. Edney

2004-01-01

170

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

NASA Astrophysics Data System (ADS)

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%-Trifluoropropyl)-methylpolysiloxane × 90% Cyanopropyl Polysilphenylene-siloxane × Polyethylene Glycol in a Sol-Gel matrix arrangement and (2) derivatizing the aerosol extract and reanalyzing the sample on the GC × 2GC column combination. Quantifying groupings and organic molecular species in time series of collections of vapor- and aerosol-phase atmospheric organic matter is a promising analytic technique for measuring production of SOA and evaluating transformations of SOA precursors.

Flores, Rosa M.; Doskey, Paul V.

2014-10-01

171

Size fractionation and molecular composition of water-soluble inorganic and organic nitrogen in aerosols of a coastal environment  

NASA Astrophysics Data System (ADS)

This study reports the first high and low molecular weight measurements of dissolved organic nitrogen (DON) in size-fractionated atmospheric particles. The variations in concentration of nitrogen species corresponded to varying sources and weather conditions. The results indicate that continental, local, and marine origins are the key factors controlling the particle size distribution of inorganic and organic nitrogen species. For dissolved inorganic nitrogen and DON, relatively high concentrations and fine-mode particle (particle diameter <1 ?m) enrichment were significantly affected by continental and locally derived sources, which were mainly attributable to anthropogenic activities. However, the coarse/fine ratios indicate that DON was derived from a coarse particle (particle diameter >1 ?m) source that may be sea salt particles. To investigate the possible sources of DON, an ultrafiltration method was used to separate DON into high (HMW) and low (LMW) molecular weight categories. The results indicate that HMW-DON and LMW-DON contributed 57 ± 9% and 43 ± 9%, respectively, to the total DON concentration. Correlations and positive matrix factorization analysis of HMW-DON and LMW-DON levels with major and non-sea-salt ions indicated that HMW-DON and LMW-DON in coarse particles may be generated from continental soil dust and sea spray, respectively, whereas, in fine particles, DON may originate from aerosols derived from combustion processes. The annual fluxes of HMW-DON and LMW-DON were estimated to be 11.0 and 11.3 mmol m-2 yr-1, respectively. Consequently, the inputs of HMW-DON and LMW-DON appear to make equal contributions to DON in aerosols over the studied coastal area.

Chen, Hung-Yu; Chen, Liang-De; Chiang, Zhong-Ying; Hung, Chin-Chang; Lin, Fei-Jan; Chou, Wen-Chen; Gong, Gwo-Ching; Wen, Liang-Saw

2010-11-01

172

Secondary organic aerosol formation from gasoline passenger vehicle emissions investigated in a smog chamber  

NASA Astrophysics Data System (ADS)

Gasoline vehicles have elevated emissions of volatile organic compounds during cold starts and idling and have recently been pointed out as potentially the main source of anthropogenic secondary organic aerosol (SOA) in megacities. However, there is a lack of laboratory studies to systematically investigate SOA formation in real-world exhaust. In this study, SOA formation from pure aromatic precursors, idling and cold start gasoline exhaust from one Euro II, one Euro III and one Euro IV passenger vehicles were investigated using photo-oxidation experiments in a 6 m3 smog chamber. The experiments were carried out at atmospherically relevant organic aerosol mass concentrations. The characterization methods included a high resolution aerosol mass spectrometer and a proton transfer mass spectrometer. It was found that gasoline exhaust readily forms SOA with a signature aerosol mass spectrum similar to the oxidized organic aerosol that commonly dominates the organic aerosol mass spectra downwind urban areas. After 4 h aging the formed SOA was 1-2 orders of magnitude higher than the Primary OA emissions. The SOA mass spectrum from a relevant mixture of traditional light aromatic precursors gave f43 (mass fraction at m/z = 4 3) approximately two times higher than to the gasoline SOA. However O : C and H : C ratios were similar for the two cases. Classical C6-C9 light aromatic precursors were responsible for up to 60% of the formed SOA, which is significantly higher than for diesel exhaust. Important candidates for additional precursors are higher order aromatic compounds such as C10, C11 light aromatics, naphthalene and methyl-naphthalenes.

Nordin, E. Z.; Eriksson, A. C.; Roldin, P.; Nilsson, P. T.; Carlsson, J. E.; Kajos, M. K.; Hellén, H.; Wittbom, C.; Rissler, J.; Löndahl, J.; Swietlicki, E.; Svenningsson, B.; Bohgard, M.; Kulmala, M.; Hallquist, M.; Pagels, J.

2012-12-01

173

Formation and evolution of biogenic secondary organic aerosol over a forest site in Japan  

NASA Astrophysics Data System (ADS)

composition of atmospheric aerosol particles was characterized using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer at a forest site in Japan during 20-30 August 2010. A major fraction of nonrefractory submicron aerosol particles consisted of organics (accounting for, on average, 46% of total mass), sulfate (41%), and ammonium (12%). Positive matrix factorization of high-resolution organic aerosol mass spectra identified two oxygenated organic aerosol (OOA) components: a highly oxidized, low-volatility OOA and a less oxidized, semivolatile OOA (SV-OOA), interpreted mainly as aged regional organic aerosol (OA) and as locally formed biogenic secondary OA (BSOA), respectively. The mass concentrations of SV-OOA increased prominently during the daytime, suggesting a strong photochemical production of BSOA on both nonevent and new particle formation event days. Increases of f44 (fraction of m/z 44 in OA mass spectrum), the fraction of CxOy+ fragment, and the O/C ratio after midday (around 13:00 local time) suggest that OA became increasingly oxygenated, which can be explained by the aging of freshly formed BSOA. Aqueous phase oxidation reactions under conditions of high relative humidity may have played a vital role in the aging of BSOA in this forest atmosphere. A substantial increase of the mass concentration of organics in the small size range (below 300 nm in vacuum aerodynamic diameter), without an increase in that of sulfate, suggests that the formation of BSOA made a dominant contribution to the presence of particles of cloud condensation nuclei size around the studied area.

Han, Yuemei; Iwamoto, Yoko; Nakayama, Tomoki; Kawamura, Kimitaka; Mochida, Michihiro

2014-01-01

174

Characterization of Size-Differentiated Inorganic Composition of Aerosols in Mexico City (CU)  

Microsoft Academic Search

Aerosol size distributions for the major ionic species: sulfate, nitrate, ammonium and potassium were determined at one sampling site (CU), located in the southwest of Mexico City (19° N, 99° W) from October, 2000 through August, 2001 with a Micro Orifice Uniform Deposit Impactor (MOUDI). Based on this analysis, sulfate and ammonium, which were correlated, were major features of the

M. Moya; T. Castro; M. Zepeda; A. Baez

2002-01-01

175

Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance  

NASA Astrophysics Data System (ADS)

The organic fraction of atmospheric aerosols contains a multitude of compounds and usually only a small fraction can be identified and quantified. However, a limited number of representative organic compounds can be used to describe the water-soluble organic fraction. In this work, initiated within the EU 5FP project SMOCC, four mixtures containing various amounts of inorganic salts (ammonium sulfate, ammonium nitrate, and sodium chloride) and three model organic compounds (levoglucosan, succinic acid and fulvic acid) were studied. The interaction between water vapor and aerosol particles was studied at different relative humidities: at subsaturation using a hygroscopic tandem differential mobility analyzer (H-TDMA) and at supersaturation using a cloud condensation nuclei spectrometer (CCN spectrometer). Surface tensions as a function of carbon concentrations were measured using a bubble tensiometer. Parameterizations of water activity as a function of molality, based on hygroscopic growth, are given for the pure organic compounds and for the mixtures, indicating van't Hoff factors around 1 for the organics. The Zdanovskii-Stokes-Robinson (ZSR) mixing rule was tested on the hygroscopic growth of the mixtures and it was found to adequately explain the hygroscopic growth for 3 out of 4 mixtures, when the limited solubility of succinic acid is taken into account. One mixture containing sodium chloride was studied and showed a pronounced deviation from the ZSR mixing rule. Critical supersaturations calculated using the parameterizations of water activity and the measured surface tensions were compared with those determined experimentally.

Svenningsson, B.; Rissler, J.; Swietlicki, E.; Mircea, M.; Bilde, M.; Facchini, M. C.; Decesari, S.; Fuzzi, S.; Zhou, J.; Mønster, J.; Rosenørn, T.

2006-06-01

176

Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance  

NASA Astrophysics Data System (ADS)

The organic fraction of atmospheric aerosols contains a multitude of compounds and usually only a small fraction can be identified and quantified. However, a limited number of representative organic compounds can be used to describe the water-soluble organic fraction. In this work, initiated within the EU 5FP project SMOCC, four mixtures containing various amounts of inorganic salts (ammonium sulfate, ammonium nitrate, and sodium chloride) and three model organic compounds (levoglucosan, succinic acid and fulvic acid) were studied. The interaction between water vapor and aerosol particles was studied at different relative humidities: at subsaturation using a hygroscopic tandem differential mobility analyzer (H-TDMA) and at supersaturation using a cloud condensation nuclei spectrometer (CCN spectrometer). Surface tensions as a function of carbon concentrations were measured using a bubble tensiometer. Parameterizations of water activity as a function of molality, based on hygroscopic growth, are given for the pure organic compounds and for the mixtures, indicating van't Hoff factors around 1 for the organics. The Zdanovskii-Stokes-Robinson (ZSR) mixing rule was tested on the hygroscopic growth of the mixtures and it was found to adequately explain the hygroscopic growth for 3 out of 4 mixtures, when the limited solubility of succinic acid is taken into account. One mixture containing sodium chloride was studied and showed a pronounced deviation from the ZSR mixing rule. Critical supersaturations calculated using the parameterizations of water activity and the measured surface tensions were compared with those determined experimentally.

Svenningsson, B.; Rissler, J.; Swietlicki, E.; Mircea, M.; Bilde, M.; Facchini, M. C.; Decesari, S.; Fuzzi, S.; Zhou, J.; Mønster, J.; Rosenørn, T.

2005-05-01

177

Fog scavenging of organic and inorganic aerosol in the Po Valley  

NASA Astrophysics Data System (ADS)

The interaction of aerosol with atmospheric water affects the processing and wet removal of atmospheric particles. Understanding such interaction is mandatory to improve model description of aerosol lifetime and ageing. We analyzed the aerosol-water interaction at high relative humidity during fog events in the Po Valley within the framework of the Agenzia Regionale per la Prevenzione e l'Ambiente (ARPA) - Emilia Romagna supersite project. For the first time in this area, the changes in particle chemical composition caused by fog are discussed along with changes in particle microphysics. During the experiment, 14 fog events were observed. The average mass scavenging efficiency was 70% for nitrate, 68% for ammonium, 61% for sulfate, 50% for organics, and 39% for black carbon. After fog formation, the interstitial aerosol was dominated by particles smaller than 200 nm Dva (vacuum aerodynamic diameter) and enriched in carbonaceous aerosol, mainly black carbon and water-insoluble organic aerosol. For each fog event, the size-segregated scavenging efficiency of nitrate and organic aerosol (OA) was calculated by comparing chemical species size distribution before and after fog formation. For both nitrate and OA, the size-segregated scavenging efficiency followed a sigmoidal curve, with values close to zero below 100 nm Dva and close to 1 above 700 nm Dva. OA was able to affect scavenging efficiency of nitrate in particles smaller than 300 nm Dva. A linear correlation between nitrate scavenging and particle hygroscopicity (?) was observed, indicating that 44-51% of the variability of nitrate scavenging in smaller particles (below 300 nm Dva) was explained by changes in particle chemical composition. The size-segregated scavenging curves of OA followed those of nitrate, suggesting that organic scavenging was controlled by mixing with water-soluble species. In particular, functional group composition and OA elemental analysis indicated that more oxidized OA was scavenged more efficiently than less oxidized OA. Nevertheless, the small variability of organic functional group composition during the experiment did not allow us to discriminate the effect of different organic functionalities on OA scavenging.

Gilardoni, S.; Massoli, P.; Giulianelli, L.; Rinaldi, M.; Paglione, M.; Pollini, F.; Lanconelli, C.; Poluzzi, V.; Carbone, S.; Hillamo, R.; Russell, L. M.; Facchini, M. C.; Fuzzi, S.

2014-07-01

178

Hexagonal ice stability and growth in the presence of glyoxal and secondary organic aerosols.  

PubMed

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

Daskalakis, Vangelis; Hadjicharalambous, Marios

2014-09-01

179

Oxidation of ambient biogenic secondary organic aerosol by hydroxyl radicals: Effects on cloud condensation nuclei activity  

NASA Astrophysics Data System (ADS)

Changes in the hygroscopicity of ambient biogenic secondary organic aerosols (SOA) due to controlled OH oxidation were investigated at a remote forested site at Whistler Mountain, British Columbia during July of 2010. Coupled photo-oxidation and cloud condensation nuclei (CCN) experiments were conducted on: i) ambient particles exposed to high levels of gas-phase OH, and ii) the water-soluble fraction of ambient particles oxidized by aqueous-phase OH. An Aerodyne Aerosol Mass Spectrometer (AMS) monitored the changes in the chemical composition and degree of oxidation (O:C ratio) of the organic component of ambient aerosol due to OH oxidation. The CCN activity of size-selected particles was measured to determine the hygroscopicity parameter ($\\kappa$org,CCN) for particles of various degrees of oxygenation. In both cases, the CCN activity of the oxidized material was higher than that of the ambient particles. In general, $\\kappa$org,CCN of the aerosol increases with its O:C ratio, in agreement with previous laboratory measurements.

Wong, J. P. S.; Lee, A. K. Y.; Slowik, J. G.; Cziczo, D. J.; Leaitch, W. R.; Macdonald, A.; Abbatt, J. P. D.

2011-11-01

180

Unraveling Contributions of Urban, Biomass Burning and Secondary Organic Aerosols Near Mexico City During MILAGRO 2006  

NASA Astrophysics Data System (ADS)

Organic aerosols (OA) can be classified into three broad categories: 1) primary organic aerosols (POA) directly emitted from urban sources (e.g., vehicular exhaust), 2) biomass burning organic aerosols (BBOA) directly emitted from forest/vegetation fires, and 3) secondary organic aerosols (SOA) from gas-to-particle conversion of semi-volatile and non-volatile organic species formed as a result of photooxidation of volatile organic compounds (VOCs) of both anthropogenic and biogenic origins. It is of great interest for both air quality and climate forcing purposes to quantify the contributions of these three types to the total OA mass observed at any given location. The Aerodyne Aerosol Mass Spectrometer (AMS) is particularly useful for obtaining high time-resolution measurements of OA mass concentrations. However, the difficulty lies in separating the POA, BBOA, and SOA fractions from the observed total OA mass. In this paper we focus on the analysis of the 10-min average AMS and PTR-MS data at the T1 ground site (just outside of Mexico City to the north) to unravel the contributions of the three OA fractions. We make use of acetylene (C2H2) and acetonitrile (CH3CN) mixing ratios as tracers of urban and biomass burning emissions, respectively, to first determine the POA and BBOA masses with the rather straightforward multi-linear regression (MLR) technique. SOA is then estimated from the difference between the total OA and POA+BBOA masses. A similar multi-linear regression analysis is also performed on the CO data to determine the urban and biomass burning components. We also apply the more sophisticated Positive Matrix Factorization (PMF) technique to deconvolve the AMS mass spectra into hydrocarbon-like organic aerosol (HOA), biomass burning-like organic aerosol (BBOA), and oxygenated organic aerosol (OOA). A comparison of the estimates of POA, BBOA, and SOA from the MLR and PMF analyses will be presented. The ?[POA]/?[CO]urban and ?[BBOA]/?[CO]fire ratios estimated from both the techniques will also be compared with those obtained from the available emissions inventory for the Mexico City area as well as with the available values in literature. Implications of our findings on POA and BBOA emission factors will be discussed.

Zaveri, R. A.; Song, C.; Alexander, L.; Xie, Y.; Fast, J. D.; Yu, X.; Canagaratna, M.; Onasch, T. B.; Jayne, J. T.; Worsnop, D. R.; de Gouw, J.; Welsh-Bon, D.; Warneke, C.; Aiken, A. C.; Jimenez, J. L.; Huey, G.

2008-12-01

181

Evolution and aging of biogenic secondary organic aerosol over a mid-latitude forest site  

NASA Astrophysics Data System (ADS)

Biogenic secondary organic aerosols (BSOAs), which are originated from the oxidation of biogenic volatile organic compounds (BVOCs) emitted from terrestrial vegetation, may contribute largely to atmospheric organic aerosols on the global scale. However, their formation pathways, physical and chemical properties, and aging processes are poorly characterized to date. In this study, submicron organic aerosols were measured using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) at a remote forest site in Japan during 20-30 August 2010. The formation and evolution of BSOA are investigated based on the variations in the mass spectra of organic aerosols, in particular on the days when new particle formation (NPF) events were evident. The increases of f43 (fraction of m/z 43 in organic mass spectrum), the fraction of CxHyO1+ fragment, and the H/C ratio at around 0800-1300 local time (LT) on NPF event and non-event days suggest that the less oxygenated organic aerosols (fresh BSOAs herein) were formed substantially during this time period. The increases of f44 (fraction of m/z 44 in organic mass spectrum), the fraction of CxOy+ fragment, and the O/C ratio after midday (around 1300 LT) on NPF event days suggest that organic aerosols were increasingly oxygenated, which can be explained by the aging of freshly-formed BSOA in this forest atmosphere. The heterogeneous and aqueous phase reactions of BSOA with oxidants were possibly the major aging pathways that explain the observed changes in the mass spectra of organic aerosols after midday on NPF event days. High relative humidity condition in this forest environment (hourly average: 74%-97%) suggests that the reactions of organics in the aqueous phase may have played a vital role in the aging of BSOA. Another possible cause of the changes in the organic mass spectra after midday on NPF event days is the uptake of semi-volatile species. The substantive formation of BSOA and their prompt aging may have made a dominant contribution to the growth of particles to the size of cloud condensation nuclei in the studied forest atmosphere.

Han, Y.; Iwamoto, Y.; Nakayama, T.; Kawamura, K.; Mochida, M.

2013-12-01

182

Influence of vapor wall loss in laboratory chambers on yields of secondary organic aerosol  

PubMed Central

Secondary organic aerosol (SOA) constitutes a major fraction of submicrometer atmospheric particulate matter. Quantitative simulation of SOA within air-quality and climate models—and its resulting impacts—depends on the translation of SOA formation observed in laboratory chambers into robust parameterizations. Worldwide data have been accumulating indicating that model predictions of SOA are substantially lower than ambient observations. Although possible explanations for this mismatch have been advanced, none has addressed the laboratory chamber data themselves. Losses of particles to the walls of chambers are routinely accounted for, but there has been little evaluation of the effects on SOA formation of losses of semivolatile vapors to chamber walls. Here, we experimentally demonstrate that such vapor losses can lead to substantially underestimated SOA formation, by factors as much as 4. Accounting for such losses has the clear potential to bring model predictions and observations of organic aerosol levels into much closer agreement. PMID:24711404

Zhang, Xuan; Cappa, Christopher D.; Jathar, Shantanu H.; McVay, Renee C.; Ensberg, Joseph J.; Kleeman, Michael J.; Seinfeld, John H.

2014-01-01

183

Dimer esters in ?-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity  

NASA Astrophysics Data System (ADS)

The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of ?-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of ?-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high NO conditions. However, no effect of RH on SOA mass was evident. Ozone (O3)-initiated oxidation of ?-pinene in the presence of ammonium sulfate (AS) seed coated with organic aerosol from OH-initiated oxidation of ?-pinene showed reduced nucleation compared to ozonolysis in the presence of pure AS seed aerosol. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), with a focus on the formation of carboxylic acids and high-molecular weight dimer esters. A total of eight carboxylic acids and four dimer esters were identified, constituting between 8 and 12% of the total ?-pinene SOA mass. OH-initiated oxidation of ?-pinene in the presence of nitrogen oxides (NOx) resulted in the formation of highly oxidized carboxylic acids, such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and diaterpenylic acid acetate (DTAA). The formation of dimer esters was observed only in SOA produced from the ozonolysis of ?-pinene in the absence of NOx, with increased concentrations by a~factor of two at higher RH (50-90%) relative to lower RH (30-50%). The increased formation of dimer esters correlates with an observed increase in new particle formation at higher RH due to nucleation. Increased aerosol acidity was found to have a negligible effect on the formation of the dimer esters. SOA mass yield did not influence the chemical composition of SOA formed from ?-pinene ozonolysis with respect to carboxylic acids and dimer esters. The results support the formation of the high-molecular weight dimer esters through gas-phase reactions of the stabilized Criegee Intermediate (sCI) formed from the ozonolysis of ?-pinene. The high molecular weight and polar nature of dimer esters formed in the gas-phase may explain increased particle number concentration as a~result of homogenous nucleation. Since three of these dimer esters (i.e., pinyl-diaterpenyl ester (MW 358), pinyl-diaterebyl ester (MW 344) and pinonyl-pinyl ester (MW 368)) have been observed in both laboratory-generated and ambient fine organic aerosol samples, we conclude that the dimer esters observed in this study can be used as tracers for the O3-initiated oxidation of ?-pinene, and are therefore indicative of enhanced anthropogenic activities, and that the high molecular weight and low volatility esters result in homogenous nucleation under laboratory conditions, increasing the particle number concentration.

Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

2013-12-01

184

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

PubMed

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 additional sources for this tracer at rural site and that it should be used with caution as meat cooking tracer in rural areas in the future. PMID:24262212

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

185

Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)  

NASA Astrophysics Data System (ADS)

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.

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

186

Acute Decreases in Proteasome Pathway Activity after Inhalation of Fresh Diesel Exhaust or Secondary Organic Aerosol  

PubMed Central

Background Epidemiologic studies consistently demonstrate an association between acute cardiopulmonary events and changes in air pollution; however, the mechanisms that underlie these associations are not completely understood. Oxidative stress and inflammation have been suggested to play a role in human responses to air pollution. The proteasome is an intracellular protein degradation system linked to both of these processes and may help mediate air pollution effects. Objectives In these studies, we determined whether acute experimental exposure to two different aerosols altered white blood cell (WBC) or red blood cell (RBC) proteasome activity in human subjects. One aerosol was fresh diesel exhaust (DE), and the other freshly generated secondary organic aerosol (SOA). Methods Thirty-eight healthy subjects underwent 2-hr resting inhalation exposures to DE and separate exposures to clean air (CA); 26 subjects were exposed to DE, CA, and SOA. CA responses were subtracted from DE or SOA responses, and mixed linear models with F-tests were used to test the effect of exposure to each aerosol on WBC and RBC proteasome activity. Results WBC proteasome activity was reduced 8% (p = 0.04) after exposure to either DE or SOA and decreased by 11.5% (p = 0.03) when SOA was analyzed alone. RBCs showed similar 8–10% declines in proteasome activity (p = 0.05 for DE alone). Conclusions Air pollution produces oxidative stress and inflammation in many experimental models, including humans. Two experimental aerosols caused rapid declines in proteasome activity in peripheral blood cells, supporting a key role for the proteasome in acute human responses to air pollution. PMID:21163722

Kipen, Howard M.; Gandhi, Sampada; Rich, David Q.; Ohman-Strickland, Pamela; Laumbach, Robert; Fan, Zhi-Hua; Chen, Li; Laskin, Debra L.; Zhang, Junfeng; Madura, Kiran

2011-01-01

187

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

NASA Astrophysics Data System (ADS)

We present a new mobile environmental reaction chamber for the simulation of the atmospheric aging of different emission sources without limitation from the instruments or facilities available at any single site. 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 aging of emissions may be simulated over a range of temperatures (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was determined at 25 °C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total organic aerosol (OA; primary organic aerosol (POA) emission + secondary organic aerosol (SOA) formation) was (369.8-397.5)10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the composition of the gas phase emissions suggests that the observed SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.

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.; Mo?nik, G.; Möhler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prévôt, A. S. H.

2013-09-01

188

Effects of chemical aging on global secondary organic aerosol using the volatility basis set approach  

NASA Astrophysics Data System (ADS)

A global 3-D chemical transport model (GEOS-Chem) is used with the volatility basis set (VBS) approach to examine the effects of chemical aging on global secondary organic aerosol (SOA) concentrations and budgets. We present full-year simulations and their comparisons with the global aerosol mass spectrometer (AMS) dataset, the Interagency Monitoring of Protected Visual Environments (IMPROVE) dataset from the United States, the European Monitoring and Evaluation Programme (EMEP) dataset from Europe, and water-soluble organic carbon observation data collected over East Asia. Using different chemical aging constants, we find that the model results with 4 × 10-11 cm3 molecule-1 s-1 are in better agreement with all observations relative to the model results with other aging constants, without aging, and with the two-product approach. The model simulations are improved when chemical aging is considered, especially for rural regions. However, the simulations still underestimate observed oxygenated organic aerosol (OOA) in urban areas. Two sensitivity simulations including semi-volatile primary organic aerosol (POA) were conducted. We find that including semi-volatile POA improves the model in terms of the hydrogen-like organic aerosol (HOA) to OOA ratio. However, the total OA concentrations are not improved. The total SOA production is considerably increased by 53%, from 26.0 to 39.9 Tg yr-1, after considering chemical aging, remaining lower than top-down estimates of SOA production. Direct radiative forcing (DRF) increases by -0.07 W m-2 due to the chemical aging of SOA, which is comparable to the mean DRF (-0.13 W m-2) of OA from the AeroCom multi-model study. This result indicates considerable global and, more importantly, regional climate implications. For example, the regional DRF change due to chemical aging of SOA in the eastern US is -0.29 W m-2, which is 4 times greater in magnitude than the global mean value.

Jo, D. S.; Park, R. J.; Kim, M. J.; Spracklen, D. V.

2013-12-01

189

Key parameters controlling the formation of secondary organic aerosol in the aqueous phase (aqSOA)  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol formation in the aqueous phase of cloud (fog) droplets and aerosol particles (aqSOA) might contribute significantly to the total SOA burden and can help to explain the discrepancies in observed and predicted SOA properties. Ambient SOA often comprises highly oxidized material (high O/C ratio) composed of oligomers and dicarboxylic acids that do not have any known efficient gas phase sources. In order to implement aqSOA formation in models, the most important processes within the multiphase system have to be identified. We explore parameter ranges of physical key processes and aqSOA formation rates as a function of oxidant (OH) availability. The processes include (1) phase transfer of both SOA precursors and oxidants from the gas to the aqueous phase, (2) diffusion within the aqueous phase, and (3) aqueous phase reactions that result in aqSOA formation within the aqueous particles or droplets, respectively. Model results suggest that cloud aqSOA formation is oxidant-limited even if aqueous sources of the OH radical are taken into account. This limitation manifests itself as an apparent surface-dependence of aqSOA formation. Comparison to ambient data on organic mass (oxalate) formation in clouds as a function of cloud properties (drop surface area) exhibits similar trends. These findings imply that future cloud aqSOA parametrizations should include drop surface area and/or effective droplet radius instead of liquid water volume only. In aerosol particles, chemical aqueous OH sources result in higher OH concentrations due to the enhanced surface/volume ratio and higher solute concentrations that affect aqueous OH formation rates. Thus, aerosol aqSOA might scale either with the wet aerosol surface or volume, depending on oxidant availability.

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

2013-12-01

190

Secondary organic aerosol formation and composition from the photo-oxidation of methyl chavicol (estragole)  

NASA Astrophysics Data System (ADS)

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.

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

191

Carbonaceous and inorganic composition in long-range transported aerosols over northern Japan: Implication for aging of water-soluble organic fraction  

NASA Astrophysics Data System (ADS)

To better understand the influence of sources and atmospheric processing on aerosol chemical composition, we collected atmospheric particles in Sapporo, northern Japan during spring and early summer 2005 under the air mass transport conditions from Siberia, China and surrounding seas. The aerosols were analyzed for inorganic ions, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and the major water-soluble organic compound classes (i.e., dicarboxylic acids and sugars). SO 42- is the most abundant inorganic constituent (average 44% of the identified inorganic ion mass) followed by NH 4+ (21%) and NO 3- (13%). Concentrations of OC, EC, and WSOC ranged from 2.0-16, 0.24-2.9, and 0.80-7.9 ?g m -3 with a mean of 7.4, 1.0, and 3.1 ?g m -3, respectively. High OC/EC ratios (range: 3.6-19, mean: 8.7) were obtained, however WSOC/OC ratios (0.23-0.69, 0.44) do not show any significant diurnal changes. These results suggest that the Sapporo aerosols were already aged, but were not seriously affected by local photochemical processes. Identified water-soluble organic compounds (diacids + sugars) account for <10% of WSOC. Based on some marker species and air mass back trajectory analyses, and using stable carbon isotopic compositions of shorter-chain diacids (i.e., C 2-C 4) as photochemical aging factor of organic aerosols, the present study suggests that a fraction of WSOC in OC is most likely influenced by aerosol aging, although the OC loading in aerosols may be more influenced by their sources and source regions.

Aggarwal, Shankar Gopala; Kawamura, Kimitaka

192

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

NASA Astrophysics Data System (ADS)

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 spectra and ambient OOA factors, though this poor agreement should be expected based on the variability of ambient OOA factors. Van Krevelen analysis of the POA and SOA factors for gasoline and diesel experiments reveal slopes of -0.50 and -0.40, 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.

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

2014-05-01

193

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

NASA Astrophysics Data System (ADS)

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

Schultz, Colin

2012-12-01

194

Determination of oxygenated compounds in secondary organic aerosol from isoprene and toluene smog chamber experiments  

Microsoft Academic Search

The determination of multifunctional oxygenated compounds in secondary organic aerosols (SOA) usually requires a derivatisation protocol prior to gas chromatography-mass spectrometry analysis (GC-MS). Our proposed protocol, a combination of O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) plus diluted N-methyl-N-trimethyl-silyltrifluoroacetamide (MSTFA) without catalyst, has improved the determination of carbonyls, polyhydroxyl-compounds, hydroxyl-carbonyls, hydroxyl-carboxylic acids and di-carboxylic acids. The optimised derivatisation protocol has been successfully used for

Esther Borrás; Luis Antonio Tortajada-Genaro

2011-01-01

195

Determination of oxygenated compounds in secondary organic aerosol from isoprene and toluene smog chamber experiments  

Microsoft Academic Search

The determination of multifunctional oxygenated compounds in secondary organic aerosols (SOA) usually requires a derivatisation protocol prior to gas chromatography-mass spectrometry analysis (GC-MS). Our proposed protocol, a combination of O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) plus diluted N-methyl-N-trimethyl-silyltrifluoroacetamide (MSTFA) without catalyst, has improved the determination of carbonyls, polyhydroxyl-compounds, hydroxyl-carbonyls, hydroxyl-carboxylic acids and di-carboxylic acids. The optimised derivatisation protocol has been successfully used for

Esther Borrás; Luis Antonio Tortajada-Genaro

2012-01-01

196

Persistent sensitivity of Asian aerosol to emissions of nitrogen oxides  

NASA Astrophysics Data System (ADS)

We use a chemical transport model and its adjoint to examine the sensitivity of secondary inorganic aerosol formation to emissions of precursor trace gases from Asia. Sensitivity simulations indicate that secondary inorganic aerosol mass concentrations are most sensitive to ammonia (NH3) emissions in winter and to sulfur dioxide (SO2) emissions during the rest of the year. However, in the annual mean, the perturbations on Asian population-weighted ground-level secondary inorganic aerosol concentrations of 34% due to changing nitrogen oxide (NOx) emissions are comparable to those from changing either SO2 (41%) or NH3 (25%) emissions. The persistent sensitivity to NOx arises from the regional abundance of NH3 over Asia that promotes ammonium nitrate formation. IASI satellite observations corroborate the NH3 abundance. Projected emissions for 2020 indicate continued sensitivity to NOx emissions. We encourage more attention to NOx controls in addition to SO2 and NH3 controls to reduce ground-level East Asian aerosol.

Kharol, S. K.; Martin, R. V.; Philip, S.; Vogel, S.; Henze, D. K.; Chen, D.; Wang, Y.; Zhang, Q.; Heald, C. L.

2013-03-01

197

Source contributions to primary and secondary inorganic particulate matter during a severe wintertime PM2.5 pollution episode in Xi'an, China  

NASA Astrophysics Data System (ADS)

Average PM2.5 concentrations of ?250 ?g m-3 and peak concentrations of ?500 ?g m-3 were observed in Xi'an, the largest city in Northwest China during an extreme event in January 2013. The source-oriented versions of the Community Multi-scale Air Quality (CMAQ) model with anthropogenic emissions from Emissions Database for Global Atmospheric Research (EDGAR) were used to study the source contributions of six different source categories including energy production, industries, transportation, residential activities, “other” (agriculture, biomass, waste burning, and biogenic sources), and windblown dust to primary and secondary inorganic PM2.5 (nitrate and sulfate) during this episode. The model generally captured the variation and magnitude of PM2.5 concentrations at monitoring sites. The monthly average concentration of the predicted PM2.5 in Xi'an was >200 ?g m-3, comparing favorably with the measurement of ?250 ?g m-3. Predicted concentrations of elemental carbon (EC), organic aerosol (OA), sulfate, nitrate, and ammonium were 6, 35, 18, 22, and 12 ?g m-3, respectively. Chemically unresolved PM2.5 components (PM2.5 Other) were ?80 ?g m-3. Industries and residential activities dominated EC, organic carbon (OC) and PM2.5 Other, contributing 85%, 95%, and 83%, respectively. Energy production (mainly coal combustion) was the dominating source for secondary nitrate, contributing 46%. Other local and upwind sources were also important, contributing 43% and 11% of total nitrate, respectively. Primary sulfate was ?10 ?g m-3 in vicinity surrounding point sources. Secondary sulfate from upwind sources was also important with concentrations of ?4-5 ?g m-3. Secondary sulfate formed by SO2 emitted from local sources was dominated by energy production. Based on the contributions of different sources to primary components and secondary nitrate and sulfate, the contributions of different sources to PM2.5 total mass in Xi'an during the extremely polluted months are: energy 5%, industries 58%, transportation 2%, residential activities 16%, dust 4%, and other (including other components, inexplicit sources, and upwind sources) 15%.

Wang, Dexiang; Hu, Jianlin; Xu, Yong; Lv, Di; Xie, Xiaoyang; Kleeman, Michael; Xing, Jia; Zhang, Hongliang; Ying, Qi

2014-11-01

198

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)

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 species, and possibly of unidentified VOCs as SOA precursors in biomass burning smoke. Chemical transformations continue even after mass concentration stabilizes. Changes in the biomass-burning tracer f60 ranged from substantially decreasing to remaining constant with increased aging. With increased OHexp, oxidation was always detected (as indicated by f44 and O/C). POA O/C ranged 0.15-0.5, while aged OA O/C reached up to 0.87. The rate of oxidation and maximum O/C achieved differs for each biomass and appears to increase with the initial O/C of the POA.

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

2013-05-01

199

Secondary organic aerosol formation from m-xylene photooxidation: The role of the phenolic product  

NASA Astrophysics Data System (ADS)

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.

Nakao, S.; Qi, L.; Clark, C.; Sato, K.; Tang, P.; Cocker, D.

2009-12-01

200

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

PubMed

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 (?-pinene, ?-pinene, ?-3-carene, limonene, sabinene, and ?-caryophyllene), were investigated in a series of continuous flow experiments in a 10 m(3) 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 ?-pinene to 38-65% for ?-3-carene and 86% for ?-caryophyllene at mass loading of 10 ?g 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 ?-pinene, little organonitrate and no aerosol is formed. PMID:25229208

Fry, Juliane L; Draper, Danielle C; Barsanti, Kelley C; Smith, James N; Ortega, John; Winkler, Paul M; Lawler, Michael J; Brown, Steven S; Edwards, Peter M; Cohen, Ronald C; Lee, Lance

2014-10-21

201

Using proton transfer reaction mass spectrometry for online analysis of secondary organic aerosols.  

PubMed

Proton-transfer-reaction mass spectrometry (PTR-MS) is a useful tool in ambient trace gas analysis, especially for the analysis of oxygenated volatile organic compounds (OVOC). Many OVOCs are produced during photooxidation of volatile organic compounds and contribute to both the gas phase and secondary organic aerosols (SOA). The inlet system of the PTR-MS instrument was modified to allow also for the measurement of the particulate phase of an aerosol with a high time resolution. The new inlet consists mainly of a denuder to strip off the gas phase, and a heater (120/150 degrees C) to vaporize the aerosol particles. This inlet system was tested with pinonic acid particles generated with a nebulizer and SOA particles formed during the photooxidation of 1,3,5-trimethylbenzene and alpha-pinene with NO(x) in a smog chamber. The performance of this new technique is discussed and the partitioning coefficients for the oxidation products are estimated. PMID:18939569

Hellén, Heidi; Dommen, Josef; Metzger, Axel; Gascho, Astrid; Duplissy, Jonathan; Tritscher, Torsten; Prevot, Andre S H; Baltensperger, Urs

2008-10-01

202

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

203

Soft ionization chemical analysis of secondary organic aerosol from green leaf volatiles emitted by turf grass.  

PubMed

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

Jain, Shashank; Zahardis, James; Petrucci, Giuseppe A

2014-05-01

204

Secondary organic aerosol and the burning question of gasoline vs. diesel  

NASA Astrophysics Data System (ADS)

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.

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

205

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

SciTech Connect

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.

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

2011-04-14

206

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

PubMed Central

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 (?-pinene, ?-pinene, ?-3-carene, limonene, sabinene, and ?-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 ?-pinene to 38–65% for ?-3-carene and 86% for ?-caryophyllene at mass loading of 10 ?g 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 ?-pinene, little organonitrate and no aerosol is formed. PMID:25229208

2014-01-01

207

Organic aerosol formation from the reactive uptake of isoprene epoxydiols (IEPOX) onto non-acidified inorganic seeds  

NASA Astrophysics Data System (ADS)

The reactive partitioning of cis and trans ?-IEPOX was investigated on hydrated inorganic seed particles, without the addition of acids. No organic aerosol (OA) formation was observed on dry ammonium sulfate (AS); however, prompt and efficient OA growth was observed for the cis and trans ?-IEPOX on AS seeds at liquid water contents of 40-75% of the total particle mass. OA formation from IEPOX is a kinetically limited process, thus the OA growth continues if there is a reservoir of gas-phase IEPOX. There appears to be no differences, within error, in the OA growth or composition attributable to the cis / trans isomeric structures. Reactive uptake of IEPOX onto hydrated AS seeds with added base (NaOH) also produced high OA loadings, suggesting the pH dependence for OA formation from IEPOX is weak for AS particles. No OA formation, after particle drying, was observed on seed particles where Na+ was substituted for NH4+. The Henry's Law partitioning of IEPOX was measured on NaCl particles (ionic strength ~9 M) to be 3 × 107 M atm-1 (-50 / +100%). A small quantity of OA was produced when NH4+ was present in the particles, but the chloride (Cl-) anion was substituted for sulfate (SO42-), possibly suggesting differences in nucleophilic strength of the anions. Online time-of-flight aerosol mass spectrometry and offline filter analysis provide evidence of oxygenated hydrocarbons, organosulfates, and amines in the particle organic composition. The results are consistent with weak correlations between IEPOX-derived OA and particle acidity or liquid water observed in field studies, as the chemical system is nucleophile-limited and not limited in water or catalyst activity.

Nguyen, T. B.; Coggon, M. M.; Bates, K. H.; Zhang, X.; Schwantes, R. H.; Schilling, K. A.; Loza, C. L.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

2014-04-01

208

Organic aerosol formation from the reactive uptake of isoprene epoxydiols (IEPOX) onto non-acidified inorganic seeds  

NASA Astrophysics Data System (ADS)

The reactive partitioning of cis and trans ?-IEPOX was investigated on hydrated inorganic seed particles, without the addition of acids. No organic aerosol (OA) formation was observed on dry ammonium sulfate (AS); however, prompt and efficient OA growth was observed for the cis and trans ?-IEPOX on AS seeds with liquid water contents of 40-75% of the total particle mass. OA formation from IEPOX is a kinetically-limited process; thus the OA growth continues if there is a reservoir of gas-phase IEPOX. There appears to be no differences, within error, in the OA growth or composition attributable to the cis/trans isomeric structures. Reactive uptake of IEPOX onto hydrated AS seeds with added base (NaOH) also produced high OA loadings, suggesting the pH-dependence for OA formation from IEPOX is weak for AS particles. No OA formation, after particle drying, was observed on seed particles where Na+ was substituted for NH4+. The Henry's Law partitioning of IEPOX was measured on NaCl particles (ionic strength ~9 M) to be 3 × 107 M atm-1. A small quantity of OA was produced when NH4+ was present in the particles, but the chloride (Cl-) anion was substituted for sulfate (SO42-), suggesting differences in nucleophilic strength of the anions. Online time-of-flight aerosol mass spectrometry and offline filter analysis provide evidence of oxygenated hydrocarbons, organosulfates and, notably, amines in the particle organic composition. The results help explain the substantial quantities of ambient IEPOX-derived OA observed under neutralized conditions. Experiments and models aimed at understanding OA production from IEPOX, or other epoxides, should consider the NH4+ activity, in conjunction with H+ activity (i.e., particle acidity) and nucleophile activity.

Nguyen, T. B.; Coggon, M. M.; Bates, K. H.; Zhang, X.; Schwantes, R. H.; Schilling, K. A.; Loza, C. L.; Flagan, R. C.; Wennberg, P. O.; Seinfeld, J. H.

2013-10-01

209

Online measurements of ammonia, acidic trace gases and aerosol inorganic ionic species in the Amazon Basin under biomass burning and background conditions  

NASA Astrophysics Data System (ADS)

We have measured diurnal and seasonal variations in the mixing ratios of ammonia (NH_3), nitric acid (HNO_3), nitrous acid (HNO_2), hydrochloric acid (HCl) and water-soluble inorganic aerosol species as ammonium (NH4+), nitrate (NO3-), nitrite (NO2-), chloride (Cl_-) and sulfate (SO_42-) on a pasture site in the Amazon Basin (Rondônia, Brazil) from September to November 2002 (LBA-SMOCC). Sampling was performed using a wet-annular denuder in combination with a Steam-Jet Aerosol Collector (SJAC) followed by online analysis using a mobile ion chromatograph for anions and flow injection analysis for ammonium. Measurements were supported by monitoring of meteorological parameters (e.g., relative humidity, air temperature, wind speed). Results from the biomass burning season, transition period and wet season will be presented. Preliminary evaluations show that ammonia levels were found to be highest (median values of 2.0 ppb during the biomass burning season), whereas median values for acidic trace gases were found to be an order of magnitude lower (0.2 ppb for nitric acid and 0.14 ppb for hydrochloric acid under biomass burning conditions). Preliminary results of aerosol species show that the mixing ratios were highest during the burning season (median values for ammonium ? 1.0 ppb, for nitrate ? 0.3 ppb, for nitrite ? 0.05 ppb, for chloride ? 0.1 ppb and for sulfate ? 0.25 ppb). The calculated median mixing ratio levels decreased steadily from the biomass burning season through the transition period to the wet season, by approximately 75% for trace gases and by 50% and 75% for aerosol ammonium and other inorganic aerosol species respectively. We found a strong dependence of ammonia, nitric acid, and aerosol ammonium nitrate on meteorological parameters (especially air temperature and relative humidity) as well as on daily/ nocturnal boundary layer conditions during day and night time. The diurnal data sets suggest that evaporation of ammonia and nitric acid from the aerosol surface contributes effectively to increased mixing ratios in the turbulent boundary layer at day time. Additionally, we found that a sharp increase of relative humidity to nearly 100% and a decrease of temperature from day to night time promotes the formation of aerosol ammonium nitrate due to gas-aerosol interactions. Both the soluble inorganic ionic species and soluble gases, such as NH_3 and HNO_3, are expected to play a major role in the nucleation and growth of cloud droplets under clean and polluted conditions.

Trebs, I.; Meixner, F. X.; Otjes, R. P.; Slanina, J. J.; Jongejan, P. A. C.; Moura, M. A. L.; da Silva, R. S., Jr.; Mayol-Bracero, O. L.; Artaxo, P.; Andreae, M. O.

2003-04-01

210

Gas phase precursors to anthropogenic secondary organic aerosol: detailed observations of 1,3,5-trimethylbenzene photooxidation  

Microsoft Academic Search

A series of photooxidation experiments were conducted in an atmospheric simulation chamber in order to investigate the oxidation mechanism and secondary organic aerosol (SOA) formation potential of the model anthropogenic gas phase precursor, 1,3,5-trimethylbenzene. Alongside specific aerosol measurements, comprehensive gas phase measurements, primarily by Chemical Ionisation Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS), were carried out to provide detailed insight into the

K. P. Wyche; P. S. Monks; A. M. Ellis; R. L. Cordell; A. E. Parker; C. Whyte; A. Metzger; J. Dommen; J. Duplissy; A. S. H. Prevot; U. Baltensperger; A. R. Rickard; F. Wulfert

2009-01-01

211

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

NASA Astrophysics Data System (ADS)

Long before the industrial evolution and the era of fossil fuels, high concentrations of aerosol particles were alluded to in heavily populated areas, including ancient Rome and medieval London. Recent radiocarbon measurements (14C) conducted in modern megacities came as a surprise: carbonaceous aerosol (mainly organic aerosol, OA), a predominant fraction of particulate matter (PM), remains overwhelmingly non-fossil despite extensive fossil fuel combustion. Such particles are directly emitted (primary OA, POA) or formed in-situ in the atmosphere (secondary OA, SOA) via photochemical reactions of volatile organic compounds (VOCs). Urban levels of non-fossil OA greatly exceed the levels measured in pristine environments strongly impacted by biogenic emissions, suggesting a contribution from unidentified anthropogenic non-fossil sources to urban OA. Positive matrix factorization (PMF) techniques applied to ambient aerosol mass spectrometer (AMS, Aerodyne) data identify primary cooking emissions (COA) as one of the main sources of primary non-fossil OA in major cities like London (Allan et al., 2010), New York (Sun et al., 2011) and Beijing (Huang et al., 2010). Cooking processes can also emit VOCs that can act as SOA precursors, potentially explaining in part the high levels of oxygenated OA (OOA) identified by the AMS in urban areas. However, at present, the chemical nature of these VOCs and their secondary aerosol production potential (SAPP) remain virtually unknown. The approach adopted here involves laboratory quantification of PM and VOC emission factors from the main primary COA emitting processes and their SAPP. Primary emissions from deep-fat frying, vegetable boiling, vegetable frying and meat cooking for different oils, meats and vegetables were analysed under controlled conditions after ~100 times dilution. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a high resolution proton transfer time-of-flight mass spectrometer (PTR-ToF-MS) were used to quantify OA and VOC emissions, respectively. SOA production potential of the different emissions was quantified by introducing them into the PSI mobile smog chamber and a potential aerosol chamber (PAM) where they were photochemically aged. The measurements of primary emissions suggest that the COA factor identified in ambient atmospheric aerosols is mostly related to fat release from frying with vegetable oils or grilling fatty-meats. In contrast, vegetable cooking (boiling and frying) was associated with significant VOC emissions. The VOC emissions from frying consist mainly of aldehydes which are formed through breaking of fatty acids. Gas phase composition, emission factors and SAPP from all these processes will be presented. This work was supported by the Swiss National Science Foundation as well as the Swiss Federal Office for the Environment. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.° 290605 (COFUND: PSI-FELLOW). J. Allan et al, Atmos. Chem. Phys. 10, 647-668 (2010) X.-F. Huang et al, Atmos. Chem. Phys. 10, 8933-8945 (2010) Y.-L. Sun et al, Atmos. Chem. Phys. 11, 1581-1602 (2011)

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

2014-05-01

212

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation  

NASA Astrophysics Data System (ADS)

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m 3 FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at ˜300-305 K under dry conditions, concerning NO x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic-NO x and simplified ambient surrogate-NO x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO x levels as low as ˜2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.

Carter, William P. L.; Cocker, David R.; Fitz, Dennis R.; Malkina, Irina L.; Bumiller, Kurt; Sauer, Claudia G.; Pisano, John T.; Bufalino, Charles; Song, Chen

213

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

PubMed

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

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

2013-01-01

214

Aging of Secondary Organic Aerosol from ?-Pinene: Changes in Chemical Composition, Density and Morphology  

NASA Astrophysics Data System (ADS)

Biogenic volatile organic compounds (VOC) are emitted in large quantities into the atmosphere. These VOC, which includes ?-pinene, can react to produce secondary organic aerosols (SOA), which contribute to a substantial fraction of ambient organic aerosols and are known to adversely affect visibility, climate and health. Despite this, the current knowledge regarding the SOA composition, their physical properties and the chemical aging processes they undergo in the atmosphere is limited. In this study, chemical aging of SOA generated from the photooxidation of ?-pinene was investigated in the York University smog chamber. The formation and aging of both gas and particle phase products were analyzed using an atmospheric pressure chemical ionization triple quadrupole mass spectrometer. The density of secondary organic matter was also simultaneously measured over the course of the aging experiments, allowing us to improve our understanding in changes in particle composition that may occur. In addition, particle phase and shape was investigated for generated particles from ?-pinene oxidation by scanning electron microscope (SEM). Results of this work, including particle density and morphology will be presented as well as comparisons of gas and particle phase products time profiles during aging.

Sarrafzadeh, M.; Hastie, D. R.

2013-12-01

215

Secondary organic aerosol formation from intermediate-volatility organic compounds: cyclic, linear, and branched alkanes.  

PubMed

Intermediate volatility organic compounds (IVOCs) are an important class of secondary organic aerosol (SOA) precursors that have not been traditionally included in chemical transport models. A challenge is that the vast majority of IVOCs cannot be speciated using traditional gas chromatography-based techniques; instead they are classified as an unresolved complex mixture (UCM) that is presumably made up of a complex mixture of branched and cyclic alkanes. To better understand SOA formation from IVOCs, a series of smog chamber experiments was conducted with different alkanes, including cyclic, branched, and linear compounds. The experiments focused on freshly formed SOA from hydroxyl (OH) radical-initiated reactions under high-NO(x) conditions at typical atmospheric organic aerosol concentrations (C(OA)). SOA yields from cyclic alkanes were comparable to yields from linear alkanes three to four carbons larger in size. For alkanes with equivalent carbon numbers, branched alkanes had the lowest SOA mass yields, ranging between 0.05 and 0.08 at a C(OA) of 15 ?g m(-3). The SOA yield of branched alkanes also depends on the methyl branch position on the carbon backbone. High-resolution aerosol mass spectrometer data indicate that the SOA oxygen-to-carbon ratios were largely controlled by the carbon number of the precursor compound. Depending on the precursor size, the mass spectrum of SOA produced from IVOCs is similar to the semivolatile-oxygenated and hydrocarbon-like organic aerosol factors derived from ambient data. Using the new yield data, we estimated SOA formation potential from diesel exhaust and predict the contribution from UCM vapors to be nearly four times larger than the contribution from single-ring aromatics and comparable to that of polycyclic aromatic hydrocarbons after several hours of oxidation at typical atmospheric conditions. Therefore, SOA from IVOCs may be an important contributor to urban OA and should be included in SOA models; the yield data presented in this study are suitable for such use. PMID:22823284

Tkacik, Daniel S; Presto, Albert A; Donahue, Neil M; Robinson, Allen L

2012-08-21

216

Cloud Condensation Nucleus (CCN) Activation Properties of Biogenic Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Organic compounds are known to comprise a significant fraction of the atmospheric aerosol population and have been found to contribute to the concentration of cloud condensation nuclei (CCN). Much of this organic material is secondary in nature; secondary organic aerosol (SOA) is formed when volatile organic compounds are oxidized to form less volatile products, which then condense into the aerosol phase. Many organic compounds found in the atmosphere, of both anthropogenic and biogenic origin, have been found to produce SOA. Such reactions typically result in complex mixtures of products, only a fraction of which have been identified. Thus while there have been several studies exploring the potential for organic particles to act as CCN (including some of the compounds identified in SOA products), there have been almost no direct investigation of the potential CCN activity of SOA. This paper presents the results of a series of experiments measuring directly the CCN activity of SOA produced by the ozonolysis of several common biogenic compounds. Six compounds were studied: five monoterpenes (? -pinene, ? -pinene, ? 3-carene, limonene, terpinolene) and one terpinoid alcohol (terpinen-4-ol). The chosen monoterpenes represent an estimated 87% of global monoterpene emissions, while the terpenoid alcohols make up approximately 25% of the other biogenic compounds capable of forming SOA. In each experiment, SOA was generated under controlled conditions at the Caltech indoor facility. Over several hours, CCN concentrations were measured at supersaturations ranging from 0.27% to 0.80%. These data are compared to simultaneous particle concentration and size distribution observations to determine the relationship between particle diameter and CCN activity. The analysis indicates considerable variation in CCN activity among the experiments; possible causes for such variability are explored.

Vanreken, T. M.; Ng, N. L.; Flagan, R. C.; Seinfeld, J. H.

2004-12-01

217

Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM  

NASA Astrophysics Data System (ADS)

We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas-phase Master Chemical Mechanism version 3.2 (MCMv3.2), an aerosol dynamics and particle-phase chemistry module (which considers acid-catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion-limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study (1) the evaporation of liquid dioctyl phthalate (DOP) particles, (2) the slow and almost particle-size-independent evaporation of ?-pinene ozonolysis secondary organic aerosol (SOA) particles, (3) the mass-transfer-limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), and (4) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed ?-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. In the smog chamber experiments, these salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating ?-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar-like amorphous-phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if the concentration of low-volatility and viscous oligomerized SOA material at the particle surface increases upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass-transfer-limited uptake of condensable organic compounds onto wall-deposited particles or directly onto the Teflon chamber walls of smog chambers can have a profound influence on the observed SOA formation. During the early stage of the SOA formation the wall-deposited particles and walls themselves serve as an SOA sink from the air to the walls. However, at the end of smog chamber experiments the semi-volatile SOA material may start to evaporate from the chamber walls. With these four model applications, we demonstrate that several poorly quantified processes (i.e. mass transport limitations within the particle phase, oligomerization, heterogeneous oxidation, organic salt formation, and chamber wall effects) can have a substantial influence on the SOA formation, lifetime, chemical and physical particle properties, and their evolution. In order to constrain the uncertainties related to these processes, future experiments are needed in which as many of the influential variables as possible are varied. ADCHAM can be a valuable model tool in the design and analysis of such experiments.

Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, D.; Rusanen, A.; Boy, M.; Swietlicki, E.; Svenningsson, B.; Zelenyuk, A.; Pagels, J.

2014-08-01

218

Spatial and temporal variability of ammonia and other inorganic aerosol species  

NASA Astrophysics Data System (ADS)

Nitrogen deposition to the sensitive ecosystems in Rocky Mountain National Park (RMNP) has been increasing. Ammonia has been shown to be a large fraction of this nitrogen deposition, and sources in northeastern Colorado were found to be a significant contributor. In this work we report on the results from a small network of Radiello passive samplers to investigate the temporal and spatial variability of ammonia gas concentrations in northeastern Colorado. A URG denuder/filter-pack sampler was collocated with a Radiello passive sampler to provide a check on the accuracy of passive ammonia measurements and to provide information about complementary aerosol and trace gas species. These measurements showed seasonal variations in the concentrations of both particulate- and gas-phase aerosol components. The highest concentrations of ammonia occurred during summer months. These were almost twice the lowest concentrations, which occurred during spring and fall months. Ammonia also exhibited higher than expected concentrations during winter. There was considerable spatial variability in average ammonia concentrations, with May-August averages ranging from 3 ?g m-3 in rural grasslands to 4-11 ?g m-3 at suburban-urban sites to almost 30 ?g m-3 in an area of intensive livestock feeding and farming operations. The large ammonia gradients near sources are expected for this primary pollutant with high deposition rates. The overall concentrations in this region are significantly larger than those measured in RMNP, which were around 0.5 ?g m-3, and represent a large reservoir of ammonia that can be transported to RMNP with easterly winds.

Day, D. E.; Chen, X.; Gebhart, K. A.; Carrico, C. M.; Schwandner, F. M.; Benedict, K. B.; Schichtel, B. A.; Collett, J. L.

2012-12-01

219

Contribution of fungi to primary biogenic aerosols in the atmosphere: wet and dry discharged spores, carbohydrates, and inorganic ions  

NASA Astrophysics Data System (ADS)

Biogenic aerosols play important roles in atmospheric chemistry physics, the biosphere, climate, and public health. Here, we show that fungi which actively discharge their spores with liquids into the air, in particular actively wet spore discharging Ascomycota (AAM) and actively wet spore discharging Basidiomycota (ABM), are a major source of primary biogenic aerosol particles and components. We present the first estimates for the global average emission rates of fungal spores. Measurement results and budget calculations based on investigations in Amazonia (Balbina, Brazil, July 2001) indicate that the spores of AAM and ABM may account for a large proportion of coarse particulate matter in tropical rainforest regions during the wet season (0.7-2.3 ?g m-3). For the particle diameter range of 1-10 ?m, the estimated proportions are ~25% during day-time, ~45% at night, and ~35% on average. For the sugar alcohol mannitol, the budget calculations indicate that it is suitable for use as a molecular tracer for actively wet discharged basidiospores (ABS). ABM emissions seem to account for most of the atmospheric abundance of mannitol (10-68 ng m-3), and can explain the observed diurnal cycle (higher abundance at night). ABM emissions of hexose carbohydrates might also account for a significant proportion of glucose and fructose in air particulate matter (7-49 ng m-3), but the literature-derived ratios are not consistent with the observed diurnal cycle (lower abundance at night). AAM emissions appear to account for a large proportion of potassium in air particulate matter over tropical rainforest regions during the wet season (17-43 ng m-3), and they can also explain the observed diurnal cycle (higher abundance at night). The results of our investigations and budget calculations for tropical rainforest aerosols are consistent with measurements performed at other locations. Based on the average abundance of mannitol reported for extratropical continental boundary layer air (~25 ng m-3), we have also calculated a value of ~17 Tg yr-1 as a first estimate for the global average emission rate of ABS over land surfaces, which is consistent with the typically observed concentrations of ABS (~10³-104 m-3; ~0.1-1 ?g m-3). The global average atmospheric abundance and emission rate of total fungal spores, including wet and dry discharged species, are estimated to be higher by a factor of about three, i.e. 1 ?g m-3 and ~50 Tg yr-1. Comparisons with estimated rates of emission and formation of other major types of organic aerosol (~47 Tg yr-1 of anthropogenic primary organic aerosol; 12-70 Tg yr-1 of secondary organic aerosol) indicate that emissions from fungi should be taken into account as a significant global source of organic aerosol. The effects of fungal spores and related chemical components might be particularly important in tropical regions, where both physicochemical processes in the atmosphere and biological activity at the Earth's surface are particularly intense, and where the abundance of fungal spores and related chemical compounds are typically higher than in extratropical regions.

Elbert, W.; Taylor, P. E.; Andreae, M. O.; Pöschl, U.

2007-09-01

220

Surface Tension and Critical Supersaturations for Mixed Aerosol Particles Composed of Inorganic and Organic Compounds of Atmospheric Relevance  

NASA Astrophysics Data System (ADS)

The interaction between water vapor and aerosol particles in the atmosphere has implications on important processes. Among these are cloud droplet formation and growth, which impact cloud properties and therefore have an indirect effect on climate. A significant fraction of the dry submicron mass of atmospheric aerosols is composed of water-soluble organic carbon (WSOC). Although the WSOC fraction contains a large amount of compounds, most yet unidentified, it can be partitioned into three main categories in order to use a set of model substances to reproduce its behavior. In this study, we chose levoglucosan, succinic acid and Nordic Reference fulvic acid (NRFA) to represent the WSOC categories of neutral compounds, mono-/di-carboxylic acids, and polycarboxylic acids, respectively. We measured the surface tension of aqueous pure NRFA and of five of its mixtures at 298 K using the Wilhemy plate method. Langmuir adsorption parameters for the organic mixtures were extracted by fitting the surface tension measurements and corresponding solute concentrations to the Szyszkowski-Langmuir equation. The measured surface tension as a function of aqueous NRFA concentration was identical to that of Suwannee River (SR) and Waskish Peat fulvic acids below 0.02 g/L but up to 12% and 15% higher, respectively, at higher concentrations. Similar to previous findings by Aumann et al. (2010) with SRFA, the surface tension of a NRFA/inorganic salt solution was mainly controlled by the organic compound even when the salt comprised 75% of the added solute mass. This effect was observed for mixtures of NRFA with both sodium chloride and ammonium sulfate salts up to 5 g/L of NRFA. From 5 g/L to about 50 g/L of NRFA, the surface tension for both NRFA/salt mixtures stopped decreasing, remained constant at 52-53 mN/m and then started slowly increasing indicating that the salt component might start dominating at higher concentrations. For a solution of 25% NRFA / 75% levoglucosan, the surface tension lowering with increasing concentration was very similar to that of pure aqueous NRFA even to the maximum measured concentration of 50 g/L of NRFA. However, the surface tension of the NRFA/saccharide mixture exhibited a more linear decrease when plotted against ln(NRFA concentration) in the 0.1 to 50 g/L range. We also measured the surface tension of two additional mixtures based on chemical composition data for different aerosol types. The measured surface tension for the solution representing organic aerosols (40% NRFA / 40% succinic acid / 20% levoglucosan) was bounded by that of pure NRFA and the NRFA/levoglucosan mixture up to a concentration of ~28 g/L of NRFA, where it remained constant at around 46.6 mN/m until 80 g/L of NRFA. The solution representing biomass burning aerosols (25% NRFA/ 27% succinic acid / 18% levoglucosan / 30% ammonium sulfate) had a similar surface tension to pure NRFA up to a concentration of ~5 g/L of NRFA, from where the surface tension drop continued between that of pure NRFA and the NRFA/salt mixtures. Critical supersaturations as a function of dry particle diameter were estimated by using measured water activity as a function of concentration and surface tension data to calculate the maximum of each Köhler curve for the mixtures studied.

Zamora, I. R.; Jacobson, M. Z.

2012-12-01

221

Aerosol-assisted atmospheric cold plasma deposition and characterization of superhydrophobic organic-inorganic nanocomposite thin films.  

PubMed

A facile atmospheric pressure cold plasma process is presented to deposit a novel organic-inorganic hydrocarbon polymer/ZnO nanoparticles nanocomposite coating. Specifically, this method involves the utilization of an atmospheric pressure dielectric barrier discharge (DBD) fed with helium and the aerosol of a dispersion of oleate-capped ZnO nanoparticles (NPs) in n-octane. As assessed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, the deposited nanocomposite coating combines the chemical features of both the oleate-capped ZnO NPs and the polyethylene-like organic component originated from the plasma polymerization of n-octane. Additionally, scanning electron microscopy (SEM) and transmission scanning electron microscopy (TSEM) confirm the synthesis of hierarchical micro/nanostructured coatings containing quasi-spherical NPs agglomerates. The polyethylene-like polymer covers the NPs agglomerates to different extents and contributes to their immobilization in the three-dimensional network of the coating. The increase of both the deposition time (1-10 min) and the NPs concentration in the dispersion (0.5-5 wt %) has a significant effect on the chemical and morphological structure of the thin films and, in fact, results in the increase the ZnO NPs content, which ultimately leads to superhydrophobic surfaces (advancing and receding water contact angles higher than 160°) with low hysteresis due to the hierarchical multiscale roughness of the coating. PMID:24393041

Fanelli, Fiorenza; Mastrangelo, Anna M; Fracassi, Francesco

2014-01-28

222

Reactions of Volatile Furandiones, Aldehydes and Water Vapor in Secondary Organic Aerosol Formation and in Gas Chromatography Analysis  

NASA Astrophysics Data System (ADS)

Volatile furandiones and aldehydes are important atmospheric oxidation products of simple aromatic compounds found in gasoline. A mechanism of secondary organic aerosol formation by furandiones was identified using particle chamber observations and FTIR measurements of model condensed phases. Growth of inorganic seed aerosol was monitored by scanning mobility particle sizing in the presence of humidity and high concentrations of 2,5-furandione (maleic anhydride), 3-methyl-2,5-furandione (citraconic anhydride), benzaldehyde, and trans-cinnamaldehyde. Particle growth began when the gas-phase saturation level of each organic compound (relative to its pure liquid) and water vapor, when summed together, reached a threshold near one. This threshold implies that equilibrium is established between the gas phase and a newly formed, mixed condensed phase containing both organic compounds and water. This equilibrium appears to be governed by Raoult's Law, where the vapor pressure of each component is reduced proportionally to its mole fraction in the condensed phase. However, bulk liquid phase experiments showed that these organics are immiscible with water at the mole fractions expected in the particle phase in our chamber experiments. Thus, non-reactive condensation of these compounds into a mixed organic / aqueous phase is ruled out. Instead, we show that reactions between furandiones and water produce unusually strong dicarboxylic acids: cis-methylbutenedioic acid (citraconic acid) and cis-butenedioic acid (maleic acid). Bulk phase pH microprobe and FTIR attenuated total reflectance measurements demonstrated that an aqueous phase is rapidly acidified during exposure to furandiones. In addition, the presence of furandiones also greatly increased benzaldehyde solubility. This solubility increase has two causes. First, the entry of maleate (or methylmaleate) ions into the water layer lowers the polarity of the phase. Second, the increase in acidity may enhance reactivity at the aldehyde functional group. Thus the uptake of both furandiones and aldehydes onto particles in the presence of humidity appears to be reaction-dependent. When subjected to normal GC injector temperatures, the cis-butenedioic acids produced in these reactions recyclize back to furandiones with much greater ease than similar alkanedioic or trans-alkenedioic acids. This production of volatile compounds during GC analysis could cause large artifacts in gas / particle phase distribution measurements if chemical derivatization techniques are not employed.

Koehler, C. A.; Fillo, J. D.; Ries, K. A.; Sanchez, J. T.; de Haan, D. O.

2004-05-01

223

Combined volatility and mass spectrometric measurements of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

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 ?-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 becomes less volatile during ageing and this ageing was further enhanced when the mixtures were exposed to sunlight. The volatility was also affected by changes in the terpene mixtures. With the AMS we measured mass spectra of the organic aerosol particles at a reference temperature of 298 K and two additional elevated temperatures. Size distributions of the particles were obtained from the particle-time-of-flight mode of the AMS at sixteen representative m/z values. The residual total mass measured at the elevated oven temperatures was related to the total mass at the reference temperature to obtain the mass fraction remaining (MFR), which is higher for less volatile SOA. In agreement with the decreasing volatility during aging measured with the VTDMA, the MFR increases with time. An effective density of the particles was calculated comparing the mode position of the size distributions measured with the AMS and the SMPS. The effective density increases with ongoing photochemical ageing. In addition, the density of the low volatile residual particles that passed a high-temperature oven is higher than the density of particles at reference temperature. In order to investigate if the observed changes in density and volatility can be attributed to changes of the chemical composition of the particles, the mass spectra obtained at different oven temperatures and different chemical age were compared. We found that the ratio of heavy fragments (m/z > 90) increases with higher temperatures. Furthermore the fraction of the CO2+-fragment at m/z 44 to the total mass increases during the ageing process.

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

2009-04-01

224

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

NASA Astrophysics Data System (ADS)

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 lignin decomposition products (guaiacol and syringol derivatives) by reaction with OH and NO2. This research highlights the dynamic nature of fire emissions and atmospheric organic aerosols in general.

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

2009-12-01

225

Measurements and modeling of glyoxal: Insights into rural photochemistry and secondary organic aerosol production  

NASA Astrophysics Data System (ADS)

Glyoxal is important to atmospheric science as an indicator for oxidation chemistry and secondary organic aerosol formation. Global models indicate that the majority of glyoxal is biogenically derived, but few measurements of glyoxal are available in biogenically dominated regions. The Madison Laser-Induced Phosphorescence Instrument enables rapid measurements of glyoxal in such rural areas and facilitates new science with sensitive, selective, fast measurements of gas-phase glyoxal. We describe the development of this instrument and results from a deployment to a collaborative field campaign near Blodgett Forrest, CA. A photochemical box model was developed to evaluate the sources and sinks of glyoxal at the site and validated using laboratory data leading to two findings: (1) prompt formation of glyoxal from the reaction of isoprene + OH in the presence of NO; (2) model over-prediction of higher--generation glyoxal from isoprene by a factor of at least eight. Inclusion of these processes will alter mode] predictions of glyoxal and secondary aerosol due to the dominance of isoprene among biogenic emissions. A model incorporating these changes over-predicted glyoxal at the field site by a factor of 2 to 5. Vertical dilution, deposition, loss to aerosol, and transport were examined; no single process was able to reduce the over-prediction without introducing another problem such as incorrect diurnal profile. The ability of the box model to reproduce chamber but not ambient conditions suggests that the mechanistic representation of isoprene and 2--methyl--3--buten--2--ol (the dominant precursors of glyoxal at the site) should be examined in future studies with attention to the influence of the ratio of alkyl peroxy radical (RO2) to hydrogen dioxide radical (HO2). Comparison of measurements to results from the Community Multiscale Air Quality model show that the model correctly predicts ozone at the site but fails to match crucial aspects of radical and higher--generation chemistry, leading to excess glyoxal. Current generation global and regional models may place undue emphasis on the formation of aerosol from glyoxal from biogenic precursors as a result of similar over--predictions. Improvements to model photochemistry are suggested, likely leading to changes in predicted ozone.

Huisman, Andrew J.

226

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

NASA Astrophysics Data System (ADS)

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. Therefore heterogeneous or gaseous formation of NDMA with partitioning to droplet must be the source of aqueous NDMA. Box-model calculations tended to demonstrate a predominance of a gas phase formation mechanism followed by partitioning into the cloud droplets. The calculations were consistent with field measurements of gaseous and aqueous NDMA concentrations. Measurements and model calculations showed that while NDMA is eventually photolyzed, it might persist in the atmosphere for hours.

Hutchings, James W., III

227

Kinetic limitations in gas-particle reactions arising from slow diffusion in secondary organic aerosol.  

PubMed

The potential for aerosol physical properties, such as phase, morphology and viscosity/ diffusivity, to affect particle reactivity remains highly uncertain. We report here a study of the effect of bulk diffusivity of polycyclic aromatic hydrocarbons (PAHs) in secondary organic aerosol (SOA) on the kinetics of the heterogeneous reaction of particle-borne benzo[a]pyrene (BaP) with ozone. The experiments were performed by coating BaP-ammonium sulfate particles with multilayers of SOA formed from ozonolysis of alpha-pinene, and by subsequently investigating the kinetics of BaP loss via reaction with excess ozone using an aerosol flow tube coupled to an Aerodyne Aerosol Mass Spectrometer (AMS). All reactions exhibit pseudo-first order kinetics and are empirically well described by a Langmuir-Hinshelwood (L-H) mechanism. The results show that under dry conditions (RH < 5%) diffusion through the SOA coating can lead to significant mass transfer constraints on the kinetics, with behavior between that previously observed by our group for solid and liquid organic coats. The reactivity of BaP was enhanced at -50% relative humidity (RH) suggesting that water uptake lowers the viscosity of the SOA, hence lifting the mass transfer constraint to some degree. The kinetics for -70% RH were similar to results obtained without SOA coats, indicating that the SOA had sufficiently low viscosity and was sufficiently liquid-like that reactants could rapidly diffuse through the coat. A kinetic multi-layer model for aerosol surface and bulk chemistry was applied to simulate the kinetics, yielding estimates for the diffusion coefficients (in cm2 s(-1)) for BaP in alpha-pinene SOA of 2 x 10(-14), 8 x 10(-14) and > 1 x 10(-12) for dry (RH < 5%), 50% RH and 70% RH conditions, respectively. These results clearly indicate that slow diffusion of reactants through SOA coats under specific conditions can provide shielding from gas-phase oxidants, enabling the long-range atmospheric transport of toxic trace species, such as PAHs and persistent organic pollutants. PMID:24601014

Zhou, Shouming; Shiraiwa, Manabu; McWhinney, Robert D; Pöschl, Ulrich; Abbatt, Jonathan P D

2013-01-01

228

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

NASA Astrophysics Data System (ADS)

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 be examined.

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

2012-12-01

229

Phase state is a limiting factor in hygroscopic growth of secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) particles formed from oxidation products of volatile organic compounds (VOC) form a significant fraction of the total atmospheric particulate matter affecting climate both directly and indirectly. The dependence of hygroscopicity on particle composition is often represented with the single parameter ?, commonly used in global models to describe the hygroscopic properties of atmospheric aerosol particles. The physical phase state of SOA particles affects the partitioning of organic vapors and also may affect the uptake of water vapor and particle activation into cloud droplets. Thus, hygroscopic behaviour of SOA particles is affected by composition (i.e. oxidation state and molecular size) but also by phase of particles. In this study the following three distinct studies were performed: (1) particle bounced fraction (BF) measurements, which are qualitatively related to particle phase, as a function of relative humidity using an Aerosol Bounce Instrument (ABI). We assume that the particles with BF > 0 are solid or semisolid, and that particles with BF = 0 behave mechanically as liquids (2) water uptake measured in the sub-saturated region using hygroscopicity tandem differential mobility analyzer (HTDMA) by measuring the ratio of wet to dry particle diameter following exposure to water vapor at a controlled RH (3) cloud droplet formation in the supersaturated region using a cloud condensation nuclei counter (CCNc). Particle composition and oxidation state was measured with a compact time of flight aerosol mass spectrometer (c-ToF-AMS). In this study we show that at sub-saturation conditions water uptake by SOA particles is restricted due to the kinetic limitations. Diffusion and solubility limitations inhibit water uptake until the humidity is high enough for dissolution to occur. Our studies show that this 'threshold' humidity is dependent on particle composition, oxidation state, and average molecular size. Our laboratory results explain several observations both in laboratory and in the atmosphere that have reported discrepancies between SOA particle hygroscopicity measurements in subsaturated and in supersaturated conditions. The results reported here provide new information about one of the most central aerosol processes in the atmosphere.

Pajunoja, Aki; Virtanen, Annele

2014-05-01

230

239,240Pu and inorganic substances in aerosols from the vicinity of a waste isolation pilot plant: the importance of resuspension.  

PubMed

Aerosol samples were collected and analyzed to characterize the spatial and temporal variations in the concentrations of plutonium and selected inorganic substances in the atmosphere around the Waste Isolation Pilot Plant (WIPP). High-volume aerosol sampling was conducted at three sites: (1) On Site, (2) Near Field, and (3) Cactus Flats. 239,240Pu was determined by alpha spectrometry following chemical separations; mass loadings were determined gravimetrically. A separate set of low-volume aerosol samples was analyzed for major ions using ion chromatography and for trace elements by inductively-coupled plasma emission spectrometry and mass spectrometry. The average 239,240Pu activity concentrations in total suspended particle (TSP) samples (12 to 16 nBq m(-3)) were consistent with those previously reported, but they varied strongly with season, with the highest values generally in spring. Further, the 239,240Pu activity concentrations were comparable among the three sites, and therefore there was no evidence for elevated 239,240Pu activities due to WIPP operations. The fraction of the 239,240Pu activity concentrations in the PM10, samples (particles less than 10 microm diameter) relative to TSP was lower than the corresponding PM10/TSP ratios of either high-volume mass or several inorganics (sulfate, aluminum or lead), indicating that 239,240Pu tends to be on large particles. Aerosol mass loadings (microg m(-3)) and 239,240Pu activity concentrations were correlated for all sets of samples, but at On Site, the TSP samples showed higher mass to 239,240Pu ratios than the other sites. Thus activities or processes occurring at or near the WIPP site evidently produced aerosols that contributed to the mass loadings but contained less 239,244Pu than ambient aerosols. About 63% of the variability in 239,240Pu activity concentrations was explained by wind travel, sampling location, length of the sampling interval, and aerosol mass. 239,240Pu activity concentrations also were correlated with aluminum (an indicator of mineral dust), further implicating the resuspension of soils as an important determinant of 239,240Pu in aerosols. The 239,240Pu/Al ratios for the aerosols were higher than in soils, and this could be explained by the preferential binding of 239,240Pu to small soil particles that have large surface area to mass ratios and also have higher aluminum contents than larger particles. PMID:12240720

Arimoto, R; Kirchner, T; Webb, J; Conley, M; Stewart, B; Schoep, D; Walthall, M

2002-10-01

231

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

NASA Astrophysics Data System (ADS)

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 obtained will be compared with those from the literature when available and discussed in terms of their atmospheric impact. Berndt, T., O. Böge and F. Stratmann (2003). Gas-phase ozonolysis of a-pinene: gaseous products and particle formation. Atmospheric Environment, 37: 3933-3945. Bonn, B. and G.K. Moortgat (2003). Sesquiterpene ozonolysis: Origin of atmospheric new particle formation from biogenic hydrocarbons. Journal of Geophysical Research, 30(11). Kavouras, I. and E.G. Stephanou (2002). Direct evidence of atmospheric secondary organic aerosol formation in forest atmosphere through heteromolecular nucleation. Environmental Science and Technology, 36: 5083-5091. Koch, S., R. Winterhalter, E. Uherek, A. Kolloff, P. Neeb and G.K. Moortagt (2000). Formation of new particles in the gas-phase ozonolysis of monoterpenes. Atmospheric Environment, 34: 4031-4042. Kulmala, M., V.-M. Kerminen, T. Anttila, A. Laaksonen and C.D. O'Dowd (2004b). Organic aerosol formation via sulphate cluster activation. Journal of Geophysical Research, 109(D04205): 1-7. Kulmala, M., H. Vehkamäki, T. Petäjä, M. Dal Maso, A. Lauri, V.-M. Kerminen, W. Birmili and P.H. McMurry (2004a). Formation and growth rates of ultra-fine atmospheric particles: a review of observations. Journal of Aerosol Science, 35: 143-176. Lee, S. and R.M. Kamens (2005). Particle nucleation from the reaction of a-pinene and O3. Atmospheric Environment, 39: 6822-6832.

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

2010-05-01

232

Balloon observations of organic and inorganic chlorine in the stratosphere: the role of HClO4 production on sulfate aerosols  

NASA Technical Reports Server (NTRS)

Simultaneous observations of stratospheric organic and inorganic chlorine were made in September 1993 out of Fort Sumner, New Mexico, using JPL balloon-borne MkIV interferometer. Between 15 and 20 km, a significant fraction (20-60%) of the inorganic chlorine could not be accounted for by the sum of measured HCl, ClONO2, and HOCl. Laboratory measurements of the reaction of ClO radicals on sulfuric acid solutions have indicated that, along with HCl, small amounts of perchloric acid, HClO4, were formed. Very little is known about the fate of HClO4 in the stratosphere and we use a photochemical box model to determine the impact of this new species on the partitioning of inorganic chlorine in the stratosphere. Assuming that HClO4 is photochemically stable, it is shown that in the enhanced aerosol loading conditions resulting from Mt. Pinatubo's eruption, HClO4 could represent a significant reservoir of chlorine in the lower stratosphere, sequestering up to 0.2 ppbv (or 50%) of the total inorganic chlorine at 16 km. The occurrence of this new species could bring to closure the inorganic chlorine budget deficiency made apparent by recent ER-2 aircraft in situ measurements of HCl.

Jaegle, L.; Yung, Y. L.; Toon, G. C.; Sen, B.; Blavier, J. F.

1996-01-01

233

Chemical composition of secondary organic aerosol formed from the photooxidation of isoprene.  

PubMed

Recent work in our laboratory has shown that the photooxidation of isoprene (2-methyl-1,3-butadiene, C(5)H(8)) leads to the formation of secondary organic aerosol (SOA). In the current study, the chemical composition of SOA from the photooxidation of isoprene over the full range of NO(x) conditions is investigated through a series of controlled laboratory chamber experiments. SOA composition is studied using a wide range of experimental techniques: electrospray ionization-mass spectrometry, matrix-assisted laser desorption ionization-mass spectrometry, high-resolution mass spectrometry, online aerosol mass spectrometry, gas chromatography/mass spectrometry, and an iodometric-spectroscopic method. Oligomerization was observed to be an important SOA formation pathway in all cases; however, the nature of the oligomers depends strongly on the NO(x) level, with acidic products formed under high-NO(x) conditions only. We present, to our knowledge, the first evidence of particle-phase esterification reactions in SOA, where the further oxidation of the isoprene oxidation product methacrolein under high-NO(x) conditions produces polyesters involving 2-methylglyceric acid as a key monomeric unit. These oligomers comprise approximately 22-34% of the high-NO(x) SOA mass. Under low-NO(x) conditions, organic peroxides contribute significantly to the low-NO(x) SOA mass (approximately 61% when SOA forms by nucleation and approximately 25-30% in the presence of seed particles). The contribution of organic peroxides in the SOA decreases with time, indicating photochemical aging. Hemiacetal dimers are found to form from C(5) alkene triols and 2-methyltetrols under low-NO(x) conditions; these compounds are also found in aerosol collected from the Amazonian rainforest, demonstrating the atmospheric relevance of these low-NO(x) chamber experiments. PMID:16884200

Surratt, Jason D; Murphy, Shane M; Kroll, Jesse H; Ng, Nga L; Hildebrandt, Lea; Sorooshian, Armin; Szmigielski, Rafal; Vermeylen, Reinhilde; Maenhaut, Willy; Claeys, Magda; Flagan, Richard C; Seinfeld, John H

2006-08-10

234

The chemical and microphysical properties of secondary organic aerosols from Holm Oak emissions  

NASA Astrophysics Data System (ADS)

The Mediterranean region is expected to experience substantial climatic change in the next 50 years. But, possible effects of climate change on biogenic volatile organic compound (VOC) emissions as well as on the formation of secondary organic aerosols (SOA) produced from these VOC are yet unexplored. To address such issues, the effects of temperature on the VOC emissions of Mediterranean Holm Oak and small Mediterranean stand of Wild Pistacio, Aleppo Pine, and Palestine Oak have been studied in the Jülich plant aerosol atmosphere chamber. For Holm Oak the optical and microphysical properties of the resulting SOA were investigated. Monoterpenes dominated the VOC emissions from Holm Oak (97.5%) and Mediterranean stand (97%). Higher temperatures enhanced the overall VOC emission but with different ratios of the emitted species. The amount of SOA increased linearly with the emission strength with a fractional mass yield of 6.0±0.6%, independent of the detailed emission pattern. The investigated particles were highly scattering with no absorption abilities. Their average hygroscopic growth factor of 1.13±0.03 at 90% RH with a critical diameter of droplet activation was 100±4 nm at a supersaturation of 0.4%. All microphysical properties did not depend on the detailed emission pattern, in accordance with an invariant O/C ratio (0.57(+0.03/-0.1)) of the SOA observed by high resolution aerosol mass spectrometry. The increase of Holm oak emissions with temperature (?20% per degree) was stronger than e.g. for Boreal tree species (?10% per degree). The SOA yield for Mediterranean trees determined here is similar as for Boreal trees. Increasing mean temperature in Mediterranean areas could thus have a stronger impact on BVOC emissions and SOA formation than in areas with Boreal forests.

Lang-Yona, N.; Rudich, Y.; Mentel, Th. F.; Bohne, A.; Buchholz, A.; Kiendler-Scharr, A.; Kleist, E.; Spindler, C.; Tillmann, R.; Wildt, J.

2010-08-01

235

CCN activity and droplet growth kinetics of fresh and aged monoterpene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The ability of secondary organic aerosol (SOA) produced from the ozonolysis of ?-pinene and monoterpene mixtures (?-pinene, ?-pinene, limonene and 3-carene) to become cloud droplets was investigated. Monoterpene SOA is quite active and would likely be a good source of cloud condensation nuclei (CCN) in the atmosphere. A static CCN counter and a Scanning Mobility CCN Analyser (a Scanning Mobility Particle Sizer coupled with a Continuous Flow counter) were used for the CCN measurements. A decrease in CCN activation diameter for ?-pinene SOA of approximately 3 nm h-1 was observed as the aerosol continued to react with oxidants. Hydroxyl radicals further oxidize the SOA particles thereby enhancing the particle CCN activity with time. The initial concentrations of ozone and monoterpene precursor (for concentrations lower than 40 ppb) do not appear to affect the activity of the resulting SOA. Köhler Theory Analysis (KTA) is used to infer the molar mass of the SOA sampled online and offline from atomized filter samples. KTA suggests that the aged aerosol (both from ?-pinene and the mixed monoterpene oxidation) is primarily water-soluble (around 70-80%), with an estimated average molar mass of 180±55 g mol-1 (consistent with existing SOA speciation studies). CCN activity measurements of the SOA mixed with (NH4)2SO4 suggest that the organic can depress surface tension by as much as 10 nM m-1 (with respect to pure water). The droplet growth kinetics of SOA samples are similar to (NH4)2SO4, except at low supersaturation, where SOA tends to grow more slowly. The CCN activity of ?-pinene and mixed monoterpene SOA can be modelled by a very simple implementation of Köhler theory, assuming complete dissolution of the particles, no dissociation into ions, molecular weight of 180 g mol-1, density of 1.5 g cm-3, and surface tension to within 10-15% of water.

Engelhart, G. J.; Asa-Awuku, A.; Nenes, A.; Pandis, S. N.

2008-01-01

236

Molecular corridors and kinetic regimes in the multiphase chemical evolution of secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The dominant component of atmospheric, organic aerosol is that derived from the oxidation of volatile organic compounds (VOCs), so-called secondary organic aerosol (SOA). SOA consists of a multitude of organic compounds, only a small fraction of which has historically been identified. Formation and evolution of SOA is a complex process involving coupled chemical reaction and mass transport in the gas and particle phases. Current SOA models do not embody the full spectrum of reaction and transport processes, nor do they identify the dominant rate-limiting steps in SOA formation. Based on molecular identification of SOA oxidation products, we show here that the chemical evolution of SOA from a variety of VOC precursors adheres to characteristic "molecular corridors" with a tight inverse correlation between volatility and molar mass. The slope of these corridors corresponds to the increase in molar mass required to decrease volatility by one order of magnitude (-dM / dlogC0). It varies in the range of 10-30 g mol-1, depending on the molecular size of the SOA precursor and the O : C ratio of the reaction products. Sequential and parallel reaction pathways of oxidation and dimerization or oligomerization progressing along these corridors pass through characteristic regimes of reaction-, diffusion-, or accommodation-limited multiphase chemical kinetics that can be classified according to reaction location, degree of saturation, and extent of heterogeneity of gas and particle phases. The molecular corridors and kinetic regimes help to constrain and describe the properties of the products, pathways, and rates of SOA evolution, thereby facilitating the further development of aerosol models for air quality and climate.

Shiraiwa, M.; Berkemeier, T.; Schilling-Fahnestock, K. A.; Seinfeld, J. H.; Pöschl, U.

2014-08-01

237

Direct Photolysis of ?-Pinene Ozonolysis Secondary Organic Aerosol: Effect on Particle Mass and Peroxide Content.  

PubMed

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 ?-pinene ozonolysis SOA with three 1-m-long denuders, and exposing the residual particles in a flow cell to near-ultraviolet (?>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 ?-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

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

2014-10-01

238

Effect of chemical structure on secondary organic aerosol formation from C12 alkanes  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) formation from four C12 alkanes (n-dodecane, 2-methylundecane, hexylcyclohexane, and cyclododecane) is studied in the Caltech Environmental Chamber under low-NOx conditions, in which the principal fate of the peroxy radical formed in the initial OH reaction is reaction with HO2. Simultaneous gas- and particle-phase measurements elucidate the effect of alkane structure on the chemical mechanisms underlying SOA growth. Reaction of branched structures leads to fragmentation and more volatile products, while cyclic structures are subject to faster oxidation and lead to less volatile products. Product identifications reveal that particle-phase reactions involving peroxyhemiacetal formation from several multifunctional hydroperoxide species are key components of initial SOA growth in all four systems. The continued chemical evolution of the particle-phase is structure-dependent, with 2-methylundecane SOA formation exhibiting the least extent of chemical processing and cyclododecane SOA achieving sustained growth with the greatest variety of chemical pathways. The extent of chemical development is not necessarily reflected in the oxygen to carbon (O : C) ratio of the aerosol as cyclododecane achieves the lowest O : C, just above 0.2, by the end of the experiment and hexylcyclohexane the highest, approaching 0.35.

Yee, L. D.; Craven, J. S.; Loza, C. L.; Schilling, K. A.; Ng, N. L.; Canagaratna, M. R.; Ziemann, P. J.; Flagan, R. C.; Seinfeld, J. H.

2013-11-01

239

Integrating phase and composition of secondary organic aerosol from the ozonolysis of ?-pinene.  

PubMed

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 ?-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

Kidd, Carla; Perraud, Véronique; Wingen, Lisa M; Finlayson-Pitts, Barbara J

2014-05-27

240

Cloud condensation nuclei activation of monoterpene and sesquiterpene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The ability of biogenic secondary organic aerosol (SOA) to contribute to the concentration of cloud condensation nuclei (CCN) in the atmosphere is examined. Aerosol is generated by the ozonolysis reaction of monoterpenes (?-pinene, ?-pinene, 3-carene, and limonene) and sesquiterpenes (?-caryophyllene, ?-humulene, and ?-cedrene) in a 10 m3 temperature-controlled Teflon smog chamber. In some cases, a self-seeding technique is used, which enables high particle concentrations with the desired diameters without compromising particle composition and purity. The monoterpene SOA is excellent CCN material, and it activates similarly (average activation diameter equals 48 ± 8 nm at 1% supersaturation for the species used in this work) to highly water-soluble organic species. Its effective solubility in water was estimated to be in the range of 0.07-0.40 g solute/g H2O. CCN measurements for sesquiterpene SOA (average activation diameter equals 120 ± 20 nm at 1% supersaturation for the species used in this work) show that it is less CCN active than monoterpene SOA. The initial terpene mixing ratio (between 3 and 100 ppb) does not affect the CCN activation for freshly generated SOA.

Huff Hartz, Kara E.; RosenøRn, Thomas; Ferchak, Shaun R.; Raymond, Timothy M.; Bilde, Merete; Donahue, Neil M.; Pandis, Spyros N.

2005-07-01

241

Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Brown carbon (BrC), which may include secondary organic aerosol (SOA), can be a significant climate-forcing agent via its optical absorption properties. However, the overall contribution of SOA to BrC remains poorly understood. Here, correlations between oxidation level and optical properties of SOA are examined. SOA was generated in a flow reactor in the absence of NOx by OH oxidation of gas-phase precursors used as surrogates for anthropogenic (naphthalene, tricyclo-[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (?-pinene) emissions. SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer. SOA mass-specific absorption cross sections (MAC) and refractive indices were calculated from real-time cavity ring-down photoacoustic spectrometry measurements at 405 and 532 nm and from UV-vis spectrometry measurements of methanol extracts of filter-collected particles (300 to 600 nm). At 405 nm, SOA MAC values and imaginary refractive indices increased with increasing oxidation level and decreased with increasing wavelength, leading to negligible absorption at 532 nm. Real refractive indices of SOA decreased with increasing oxidation level. Comparison with literature studies suggests that under typical polluted conditions the effect of NOx on SOA absorption is small. SOA may contribute significantly to atmospheric BrC, with the magnitude dependent on both precursor type and oxidation level. Mass-specific absorption cross sections (MAC) of SOA at ? = 405 nm as a function of the O/C ratio

Lambe, A. T.; Cappa, C. D.; Massoli, P.; Onasch, T. B.; Forestieri, S.; Martin, A. T.; Cummings, M. J.; Croasdale, D. R.; Brune, W. H.; Worsnop, D. R.; Davidovits, P.

2013-12-01

242

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

SciTech Connect

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.

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

2013-05-10

243

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

PubMed

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 water-soluble SOA generated from two monoterpenes, limonene and ?-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 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 ?-pinene-derived SOA. Both regions overlap with the EEM spectra of some of the fluorophores found in primary biological aerosols. Despite the low quantum yield, the aged SOA particles may have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols. PMID:23663151

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

2013-06-01

244

Evaporation Kinetics and Phase of Laboratory and Ambient Secondary Organic Aerosol  

SciTech Connect

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.

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

2011-02-08

245

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

PubMed

2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C(5)H(12)O(6)S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM(2.5)) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM(2.5) collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA. PMID:22849588

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

2012-09-01

246

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

PubMed Central

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

2012-01-01

247

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

Microsoft Academic Search

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

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

2006-01-01

248

Supplemental Information : Secondary Organic Aerosol Production from Modern Diesel Engine Emissions, Shar Samy and1 Barbara Zielinska2  

E-print Network

Supplemental Information : Secondary Organic Aerosol Production from Modern Diesel Engine Emissions emissions. For more detail on compositional and toxicity changes produced from further29 diesel engine use, including: engine age or total engine lifetime operation,23 differences in the initial in-chamber toluene

Meskhidze, Nicholas

249

Epoxide as a Precursor to Secondary Organic Aerosol Formation from Isoprene Photooxidation in the Presence of Nitrogen Oxides  

EPA Science Inventory

Isoprene is a substantial contributor to the global secondary organic aerosol (SOA) burden, with implications for public health and the climate system. The mechanism by which isoprene-derived SOA is formed and the influence of environmental conditions, however, remain unclear...

250

Secondary organic aerosol formation from the ozonolysis of 2-carene and 3-carene  

NASA Astrophysics Data System (ADS)

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(?[Carenes]).

Mellouki, A.; Chen, H.; Bernard, F.; Cazaunau, M.; Grosselin, B.; Daele, V.; Chen, J.

2013-12-01

251

Carboxylic acids in secondary aerosols from oxidation of cyclic monoterpenes by ozone  

SciTech Connect

A series of smog chamber experiments have been conducted in which five cyclic monoterpenes were oxidized by ozone. The evolved secondary aerosol was analyzed by GC-MS and HPLC-MS for nonvolatile polar oxidation products with emphasis on the identification of carboxylic acids. Three classes of compounds were determined at concentration levels corresponding to low percentage molar yields: i.e., dicarboxylic acids, oxocarboxylic acids, and hydroxyketocarboxylic acids. Carboxylic acids are highly polar and have lower vapor pressures than their corresponding aldehydes and may thus play an important role in secondary organic aerosol formation processes. The most abundant carboxylic acids were the following: cis-pinic acid AB1(cis-3-carboxy-2,2-dimethylcyclobutylethanoic acid) from {alpha} and {beta}-pinene; cis-pinonic acid A3 (cis-3-acetyl-2,2-dimethylcyclobutylethanoic acid) and cis-10-hydroxypinonic acid Ab6 (cis-2,2-dimethyl-3-hydroxyacetylcyclobutyl-ethanoic acid) from {alpha}-pinene and {beta}-pinene; cis-3-caric acid C1 (cis-2,2-dimethyl-1,3-cyclopropyldiethanoic acid), cis-3-caronic acid C3 (2,2-dimethyl-3-(2-oxopropyl)cyclopropanylethanoic acid), and cis-10-hydroxy-3-caronic acid C6 (cis-2,2-dimethyl-3(hydroxy-2-oxopropyl)cyclopropanylethanoic acid) from 3-carene; cis-sabinic acid S1 (cis-2-carboxy-1-isopropylcyclopropylethanoic acid) from sabinene; limonic acid L1 (3-isopropenylhexanedioic acid), limononic acid L3 (3-isopropenyl-6-oxo-heptanoic acid), 7-hydroxy-limononic acid L6 (3-isopropenyl-7-hydroxy-6-oxoheptanoic acid), and 7-hydroxylimononic acid Lg{prime} (7-hydroxy-3-isopropenyl-6-oxoheptanoic acid) from limonene.

Glasius, M.; Lahaniati, M.; Calogirou, A.; Di Bella, D.; Jensen, N.R.; Hjorth, J.; Kotzias, D.; Larsen, B.R.

2000-03-15

252

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

NASA Astrophysics Data System (ADS)

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.

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

253

Final Report: Process Models of the Equilibrium Size & State of Organic/Inorganic Aerosols for the Development of Large Scale Atmospheric Models & the Analysis of Field Data  

SciTech Connect

Our work addressed the following elements of the Call for Proposals: (i) “to improve the theoretical representation of aerosol processes studied in ASP laboratory or field studies”, (ii) “to enhance the incorporation of aerosol process information into modules suitable for large-scale or global atmospheric models”, and (iii) “provide systematic experimental validation of process model predictions ... using data from targeted laboratory and field experiments”. Achievements to the end of 2012 are described in four previous reports, and include: new models of densities and surface tensions of pure (single solute) and mixed aqueous solutions of typical aerosol composition under all atmospheric conditions (0 to 100% RH and T > 150 K); inclusion of these models into the widely used Extended Aerosol Inorganics model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php); the addition of vapor pressure calculators for organic compounds to the E-AIM website; the ability of include user-defined organic compounds and/or lumped surrogates in gas/aerosol partitioning calculations; the development of new equations to represent the properties of soluble aerosols over the entire concentration range (using methods based upon adsorption isotherms, and derived using statistical mechanics), including systems at close to zero RH. These results are described in publications 1-6 at the end of this report, and on the “News” page of the E-AIM website (http://www.aim.env.uea.ac.uk/aim/info/news.html). During 2012 and 2013 we have collaborated in a combined observation and lab-based study of the water uptake of the organic component of atmospheric aerosols (PI Gannet Hallar, of the Desert Research Institute). The aerosol samples were analyzed using several complementary techniques (GC/MS, FT-ICR MS, and ion chromatography) to produce a very complete organic “speciation” including both polar and non-polar compounds. Hygroscopic growth factors of the samples were measured, and we have just completed comparisons of the data with our process model predictions based upon the inorganic and organic composition of the samples.

Wexler, Anthony Stein [UC Davis] [UC Davis; Clegg, Simon Leslie [UC Davis] [UC Davis

2013-10-26

254

Real-time measurements of ammonia, acidic trace gases and water-soluble inorganic aerosol species at a rural site in the Amazon Basin  

NASA Astrophysics Data System (ADS)

We measured the mixing ratios of ammonia (NH3), nitric acid (HNO3), nitrous acid (HONO), hydrochloric acid (HCl), sulfur dioxide (SO2) and the corresponding water-soluble inorganic aerosol species, ammonium (NH4+), nitrate (NO3-), nitrite (NO2-), chloride (Cl-) and sulfate (SO42-), and their diel and seasonal variations at a pasture site in the Amazon Basin (Rondônia, Brazil). This study was conducted within the framework of LBA-SMOCC (Large Scale Biosphere Atmosphere Experiment in Amazonia Smoke Aerosols, Clouds, Rainfall and Climate). Sampling was performed from 12 September to 14 November 2002, extending from the dry season (extensive biomass burning activity), through the transition period to the wet season (background conditions). Measurements were made continuously using a wet-annular denuder in combination with a Steam-Jet Aerosol Collector (SJAC) followed by suitable on-line analysis. A detailed description and verification of the inlet system for simultaneous sampling of soluble gases and aerosol compounds is presented. Overall measurement uncertainties of the ambient mixing ratios usually remained below 15%. The limit of detection (LOD) was determined for each single data point measured during the field experiment. Median LOD values (3?-definition) were ?0.015 ppb for acidic trace gases and aerosol anions and ?0.118 ppb for NH3 and aerosol NH4+. Mixing ratios of acidic trace gases remained below 1ppb throughout the measurement period, while NH3 levels were an order of magnitude higher. Accordingly, mixing ratios of NH4+ exceeded those of other inorganic aerosol contributors by a factor of 4 to 10. During the wet season, mixing ratios decreased by nearly a factor of 3 for all compounds compared to those observed when intensive biomass burning took place. Additionally, N-containing gas and aerosol species featured pronounced diel variations. This is attributed to strong relative humidity and temperature variations between day and night as well as to changing photochemistry and stability conditions of the planetary boundary layer. HONO exhibited a characteristic diel cycle with high mixing ratios at nighttime and was not completely depleted by photolysis during daylight hours.

Trebs, I.; Meixner, F. X.; Slanina, J.; Otjes, R.; Jongejan, P.; Andreae, M. O.

2004-02-01

255

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

NASA Astrophysics Data System (ADS)

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-nitroguaiacol, 6-nitroguaiacol and 4,6-dinitroguaiacol) were examined for their presence in winter aerosol samples by using an optimized HPLC-(-)ESI-MS/MS. 4-nitroguaiacol and 4,6-dinitroguaiacol were unambiguously identified in winter PM10 from Ljubljana, Slovenia, whereas the absence of 6-nitroguaiacol was further explained with the help of long-term reaction monitoring. To our knowledge, our study represents the first report on the identification of 4,6-dinitroguaiacol in ambient aerosols. Laskin, A. et al. (2009) Environ. Sci. Technol. 43, 3764-3771. Maenhaut, W. et al. (2012) Sci. Tot. Environ. 437, 226-236. Claeys, M. et al. (2012) Environ. Chem. 9, 273-284. Iinuma, Y. et al. (2010) Environ. Sci. Technol. 44, 8453-8459. Kitanovski, Z. et al. (2012)J. Chromatogr. A 1268, 35-43.

Grgi?, Irena; Kitanovski, Zoran; Krofli?, Ana; ?usak, Alen

2014-05-01

256

The direct and indirect radiative effects of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

We use a global aerosol microphysics model in combination with an offline radiative transfer model to quantify the radiative effect of biogenic secondary organic aerosol (SOA) in the present-day atmosphere. Through its role in particle growth and ageing, the presence of biogenic SOA increases the global annual mean concentration of cloud condensation nuclei (CCN; at 0.2% supersaturation) by 3.6-21.1%, depending upon the yield of SOA production from biogenic volatile organic compounds (BVOCs), and the nature and treatment of concurrent primary carbonaceous emissions. This increase in CCN causes a rise in global annual mean cloud droplet number concentration (CDNC) of 1.9-5.2%, and a global mean first aerosol indirect effect (AIE) of between +0.01 W m-2 and -0.12 W m-2. The radiative impact of biogenic SOA is far greater when biogenic oxidation products also contribute to the very early stages of new particle formation; using two organically mediated mechanisms for new particle formation, we simulate global annual mean first AIEs of -0.22 W m-2 and -0.77 W m-2. The inclusion of biogenic SOA substantially improves the simulated seasonal cycle in the concentration of CCN-sized particles observed at three forested sites. The best correlation is found when the organically mediated nucleation mechanisms are applied, suggesting that the first AIE of biogenic SOA could be as large as -0.77 W m-2. The radiative impact of SOA is sensitive to the presence of anthropogenic emissions. Lower background aerosol concentrations simulated with anthropogenic emissions from 1750 give rise to a greater fractional CCN increase and a more substantial first AIE from biogenic SOA. Consequently, the anthropogenic indirect radiative forcing between 1750 and the present day is sensitive to assumptions about the amount and role of biogenic SOA. We also calculate an annual global mean direct radiative effect of between -0.08 W m-2 and -0.78 W m-2 in the present day, with uncertainty in the amount of SOA produced from the oxidation of BVOCs accounting for most of this range.

Scott, C. E.; Rap, A.; Spracklen, D. V.; Forster, P. M.; Carslaw, K. S.; Mann, G. W.; Pringle, K. J.; Kivekäs, N.; Kulmala, M.; Lihavainen, H.; Tunved, P.

2014-01-01

257

Secondary Organic Aerosol formation from isoprene photooxidation under dry conditions (CUMULUS project)  

NASA Astrophysics Data System (ADS)

Isoprene (2-methyl-1,3-butadiene, C5H8) is one of the most abundant non-methane hydrocarbons emitted into the troposphere. Its annual global emission has recently been estimated in the range of 440 to 660 TgC (Guenther et al., 2006). Because of its large concentrations and high reactivity with the hydroxyl radical (OH), isoprene can have a strong influence on tropospheric photochemistry. It has been determined recently that isoprene also plays a role in secondary organic aerosol (SOA) formation in the ambient atmosphere even if isoprene leads to low SOA yields. The aim of the present work was to study isoprene photo-oxidation with OH radical in order to investigate its oxidation products and resulting aerosol production. A special care was taken to the realism of the experiment: light source, NOx and OH levels and aging time (around 10 hours). Experiments were performed in the CESAM chamber (Wang et al., 2011) which was designed to investigate multiphase processes under realistic actinic flux, and accurate control of temperature. In each experiment, around 800 ppb of isoprene was injected in the chamber together with the OH source under dry conditions (<5 %RH) before irradiation. Gas-phase composition was analyzed in-situ by a Fourier Transform Infrared Spectrometer (FTIR), a Proton Transfer Reaction Mass Spectrometer (PTR-TOF-MS) and NOx and ozone analyzers. A Scanning Mobility Particle Sizer (SMPS) and an Aerodyne High Resolution Time-Of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS) were also used to investigate SOA formation and composition. In all experiments, we noted a SOA production at the end of isoprene oxidation i.e. exhibiting a clear secondary products type growth. Several results (including SOA densities and yields, and O/C ratios) were obtained using SMPS and AMS data allowing us to characterize SOA formation and composition during the experiments. The characterization of the gaseous and particulate phases will be presented. While the SOA yields in the literature exhibit a general dispersion, the SOA yields obtained during the experiments are consistent with the lowest values found in the literature. Some assumptions concerning the cause of this dispersion, including the role of the irradiation source used, will be discussed. Guenther, A. et al. (2006). Atmos. Chem. Phys 6(11): 3181-3210. Wang, J. et al. (2011). Atmospheric Measurement Techniques 4(11): 2465-2494.

Brégonzio-Rozier, Lola; Siekmann, Frank; Giorio, Chiara; Temime-Roussel, Brice; Pangui, Edouard; Morales, Sébastien; Gratien, Aline; Ravier, Sylvain; Monod, Anne; Doussin, Jean-Francois

2014-05-01

258

Model representation of secondary organic aerosol in CMAQv4.7.  

PubMed

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 pathways: in-cloud oxidation of glyoxal and methylglyoxal, particle-phase oligomerization, and acid enhancement of isoprene SOA. NO(x)-dependent aromatic SOA yields are also added along with new empirical measurements of the enthalpies of vaporization and organic mass-to-carbon ratios. For the first time, these SOA precursors, pathways and empirical parameters are included simultaneously in an air quality model for an annual simulation spanning the continental U.S. Comparisons of CMAQ-modeled secondary organic carbon (OC(sec)) with semiempirical estimates screened from 165 routine monitoring sites across the U.S. indicate the new SOA module substantially improves model performance. The most notable improvement occurs in the central and southeastern U.S. where the regionally averaged temporal correlations (r) between modeled and semiempirical OC(sec) increase from 0.5 to 0.8 and 0.3 to 0.8, respectively, when the new SOA module is employed. Wintertime OC(sec) results improve in all regions of the continental U.S. and the seasonal and regional patterns of biogenic SOA are better represented. PMID:20883028

Carlton, Annmarie G; Bhave, Prakash V; Napelenok, Sergey L; Edney, Edward O; Sarwar, Golam; Pinder, Robert W; Pouliot, George A; Houyoux, Marc

2010-11-15

259

Heterogeneous Atmospheric Aerosol Production by Acid Catalyzed Particle-Phase Reactions  

Microsoft Academic Search

According to evidence from our laboratory, acidic surfaces on atmospheric aerosols lead to potentially multifold increases in secondary organic aerosol (SOA) mass. Experimental observations using a multichannel flow reactor, Teflon (polytetrafluoroethylene) film bag batch reactors, and outdoor Teflon-film smog chambers strongly confirm that inorganic acids, such as sulfuric acid, catalyze particle-phase heterogeneous reactions of atmospheric organic carbonyl species. The net

Myoseon Jang; Nadine M. Czoschke; Sangdon Lee; Richard M. Kamens

2002-01-01

260

Secondary organic aerosol formation from the gas phase reaction of hydroxyl radicals with m-, o- and p-cresol  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation during the atmospheric oxidation of cresols was investigated using a large smog chamber (8000 L), at atmospheric pressure, 294±2 K and low relative humidity (6-10%). Cresol oxidation was initiated by irradiation of cresol/CH 3ONO/NO/air mixtures. The cresol loss was measured by gas chromatography with a flame ionization detector (GC-FID) and the temporal evolution of the aerosol was monitored using a scanning mobility particle sizer (SMPS). The overall organic aerosol yield ( Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses ( Mo) to the total reacted cresol concentrations assuming a particle density of 1.4 g cm -3. Analysis of the data clearly show that Y is a strong function of Mo and that SOA formation can be expressed by a one-product gas/particle partitioning absorption model. The aerosol formation is affected by the initial cresol concentration, which leads to aerosol yields from 9% to 42%. These results are in good agreement with a recent study performed on SOA formation from the photo-oxidation of o-cresol in a smog chamber. To our knowledge, the present work represents the first investigation of SOA formation from OH reaction with m- and p-cresol.

Henry, Françoise; Coeur-Tourneur, Cecile; Ledoux, Frédéric; Tomas, Alexandre; Menu, Dominique

261

Climate-relevant physical properties of molecular constituents relevant for isoprene-derived secondary organic aerosol material  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) particles, formed from gas-phase biogenic volatile organic compounds (BVOCs), contribute large uncertainties to the radiative forcing that is associated with aerosols in the climate system. Reactive uptake of surface-active organic oxidation products of BVOCs at the gas-aerosol interface can potentially decrease the overall aerosol surface tension and therefore influence their propensity to act as cloud condensation nuclei (CCN). Here, we synthesize and measure some climate-relevant physical properties of SOA particle constituents consisting of the isoprene oxidation products ?-, ?-, and cis- and {trans-?-IEPOX (isoprene epoxide), as well as syn- and anti-2-methyltetraol. Following viscosity measurements, we use octanol-water partition coefficients to quantify the relative hydrophobicity of the oxidation products while dynamic surface tension measurements indicate that aqueous solutions of ?- and trans-?-IEPOX exhibit significant surface tension depression. We hypothesize that the surface activity of these compounds may enhance aerosol CCN activity, and that trans-?-IEPOX may be highly relevant for surface chemistry of aerosol particles relative to other IEPOX isomers.

Upshur, M. A.; Strick, B. F.; McNeill, V. F.; Thomson, R. J.; Geiger, F. M.

2014-06-01

262

Laboratory Studies of Processing of Carbonaceous Aerosols by Atmospheric Oxidants/Hygroscopicity and CCN Activity of Secondary & Processed Primary Organic Aerosols  

SciTech Connect

The atmosphere is composed of a complex mixture of gases and suspended microscopic aerosol particles. The ability of these particles to take up water (hygroscopicity) and to act as nuclei for cloud droplet formation significantly impacts aerosol light scattering and absorption, and cloud formation, thereby influencing air quality, visibility, and climate in important ways. A substantial, yet poorly characterized component of the atmospheric aerosol is organic matter. Its major sources are direct emissions from combustion processes, which are referred to as primary organic aerosol (POA), or in situ processes in which volatile organic compounds (VOCs) are oxidized in the atmosphere to low volatility reaction products that subsequent condense to form particles that are referred to as secondary organic aerosol (SOA). POA and VOCs are emitted to the atmosphere from both anthropogenic and natural (biogenic) sources. The overall goal of this experimental research project was to conduct laboratory studies under simulated atmospheric conditions to investigate the effects of the chemical composition of organic aerosol particles on their hygroscopicity and cloud condensation nucleation (CCN) activity, in order to develop quantitative relationships that could be used to more accurately incorporate aerosol-cloud interactions into regional and global atmospheric models. More specifically, the project aimed to determine the products, mechanisms, and rates of chemical reactions involved in the processing of organic aerosol particles by atmospheric oxidants and to investigate the relationships between the chemical composition of organic particles (as represented by molecule sizes and the specific functional groups that are present) and the hygroscopicity and CCN activity of oxidized POA and SOA formed from the oxidation of the major classes of anthropogenic and biogenic VOCs that are emitted to the atmosphere, as well as model hydrocarbons. The general approach for this project was to carry out reactions of representative anthropogenic and biogenic VOCs and organic particles with ozone (O3), and hydroxyl (OH), nitrate (NO3), and chlorine (Cl) radicals, which are the major atmospheric oxidants, under simulated atmospheric conditions in large-volume environmental chambers. A combination of on-line and off-line analytical techniques were used to monitor the chemical and physical properties of the particles including their hygroscopicity and CCN activity. The results of the studies were used to (1) improve scientific understanding of the relationships between the chemical composition of organic particles and their hygroscopicity and CCN activity, (2) develop an improved molecular level theoretical framework for describing these relationships, and (3) establish a large database that is being used to develop parameterizations relating organic aerosol chemical properties and SOA sources to particle hygroscopicity and CCN activity for use in regional and global atmospheric air quality and climate models.

Ziemann, P.J.; Arey, J.; Atkinson, R.; Kreidenweis, S.M.; Petters, M.D.

2012-06-13

263

Predicted change in global secondary organic aerosol concentrations in response to future climate, emissions, and land use change  

E-print Network

aromatic emissions. The projected decrease in global sulfur emissions implies that SOA will contribute a progressively larger fraction of the global aerosol burden. Citation: Heald, C. L., et al. (2008), Predicted change in global secondary organic aerosol... budget and therefore specify fixed sea surface temperatures archived from previous NCAR CCSM climate change experiments using the SRES A1B emissions [Meehl et al., 2006]. Globally averaged temper- ature increases here by 1.8#1;C by 2100 for A1B. A full...

Heald, C. L.; Henze, D. K.; Horowitz, L. W.; Feddema, Johannes J.; Lamarque, J. F.; Guenther, A.; Hess, P. G.; Vitt, F.; Seinfeld, J. H.; Goldstein, A. H.; Fung, I.

2008-03-01

264

Time-resolved variations in the distributions of inorganic ions, carbonaceous components, dicarboxylic acids and related compounds in atmospheric aerosols from Sapporo, northern Japan during summertime  

NASA Astrophysics Data System (ADS)

To better understand time-resolved variations of water-soluble organic aerosols in the atmosphere, we collected atmospheric particles (TSP) every 3 h during summertime (8-10 August, 2005) in Sapporo, northern Japan. We measured inorganic ions, carbonaceous components, dicarboxylic acids, ketoacids and ?-dicarbonyls in TSP. SO42- was found as the most abundant ionic species (57 ± 9% of total ions determined) followed by NH4+ and NO3-. However, none of the ionic species showed any diurnal trend throughout the campaign. Organic carbon (OC) ranged from 2.1 to 12.1 ?g m-3 whereas elemental carbon (EC) was negligible in most of the samples (0.31 ± 0.56 ?g m-3). Oxalic (C2) acid was the most abundant diacid species, followed by malonic (C3) and succinic (C4) acids. Water-soluble OC (WSOC), water-insoluble OC (WIOC) and OC as well as dominant diacids (C2-C4), total diacids, ketoacids and ?-dicarbonyls did not show diurnal trend on 8 August, but they showed clear diurnal distributions during 9-10 August following the changes in ambient temperature (and radiation). Detailed analyses of time-resolved aerosols demonstrate that diurnal variations of organic aerosol compositions are caused by local in situ photochemical production, but are significantly superimposed by long-range atmospheric transport of aerosols, particularly when the air masses are enriched with emissions from higher plants and/or biomass burning, and their photochemical processing during the transport.

Pavuluri, Chandra Mouli; Kawamura, Kimitaka; Kikuta, Motomi; Tachibana, Eri; Aggarwal, Shankar G.

2012-12-01

265

Aqueous photooxidation of ambient Po Valley Italy air samples: Insights into secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

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 ~ 50-100?M) 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.

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

266

Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA), particulate matter composed of compounds formed from the atmospheric transformation of organic species, accounts for a substantial fraction of tropospheric aerosol. The formation of low-volatility (semivolatile and possibly nonvolatile) compounds that make up SOA is governed by a complex series of reactions of a large number of organic species, so the experimental characterization and theoretical description of SOA formation presents a substantial challenge. In this review we outline what is known about the chemistry of formation and continuing transformation of low-volatility species in the atmosphere. The primary focus is chemical processes that can change the volatility of organic compounds: (1) oxidation reactions in the gas phase, (2) reactions in the particle phase, and (3) continuing chemistry (in either phase) over several generations. Gas-phase oxidation reactions can reduce volatility by the addition of polar functional groups or increase it by the cleavage of carbon-carbon bonds; key branch points that control volatility are the initial attack of the oxidant, reactions of alkylperoxy (RO2) radicals, and reactions of alkoxy (RO) radicals. Reactions in the particle phase include oxidation reactions as well as accretion reactions, non-oxidative processes leading to the formation of high-molecular-weight species. Organic carbon in the atmosphere is continually subject to reactions in the gas and particle phases throughout its atmospheric lifetime (until lost by physical deposition or oxidized to CO or CO2), implying continual changes in volatility over the timescales of several days. The volatility changes arising from these chemical reactions must be parameterized and included in models in order to gain a quantitative and predictive understanding of SOA formation.

Kroll, Jesse H.; Seinfeld, John H.

2008-05-01

267

Gas-phase products and secondary aerosol yields from the ozonolysis of ten different terpenes  

NASA Astrophysics Data System (ADS)

The ozonolyses of six monoterpenes (?-pinene, ?-pinene, 3-carene, terpinolene, ?-terpinene, and myrcene), two sesquiterpenes (?-humulene and ?-caryophyllene), and two oxygenated terpenes (methyl chavicol and linalool) were conducted individually in Teflon chambers to examine the gas-phase oxidation product and secondary organic aerosol (SOA) yields from these reactions. Particle size distribution and number concentration were monitored and allowed for the calculation of the SOA yield from each experiment, which ranged from 1 to 54%. A proton transfer reaction mass spectrometer (PTR-MS) was used to monitor the evolution of gas-phase products, identified by their mass to charge ratio (m/z). Several gas-phase oxidation products, formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, and nopinone, were identified and calibrated. Aerosol yields, and the yields of these identified and calibrated oxidation products, as well as many higher m/z oxidation products observed with the PTR-MS, varied significantly between the different parent terpene compounds. The sum of measured oxidation products in the gas and particle phase ranged from 33 to 77% of the carbon in the reacted terpenes, suggesting there are still unmeasured products from these reactions. The observations of the higher molecular weight oxidation product ions provide evidence of previously unreported compounds and their temporal evolution in the smog chamber from multistep oxidation processes. Many of the observed ions, including m/z 111 and 113, have also been observed in ambient air above a Ponderosa pine forest canopy, and our results confirm they are consistent with products from terpene + O3 reactions. Many of these products are stable on the timescale of our experiments and can therefore be monitored in field campaigns as evidence for ozone oxidative chemistry.

Lee, Anita; Goldstein, Allen H.; Keywood, Melita D.; Gao, Song; Varutbangkul, Varuntida; Bahreini, Roya; Ng, Nga L.; Flagan, Richard C.; Seinfeld, John H.

2006-04-01

268

Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide  

NASA Astrophysics Data System (ADS)

Recently, methacrylic acid epoxide (MAE) has been proposed as a precursor to an important class of isoprene-derived compounds found in secondary organic aerosol (SOA): 2-methylglyceric acid (2-MG) and a set of oligomers, nitric acid esters and sulfuric acid esters related to 2-MG. However, the specific chemical mechanisms by which MAE could form these compounds have not been previously studied. In order to determine the relevance of these processes to atmospheric aerosol, MAE and 2-MG have been synthesized and a series of bulk solution-phase experiments aimed at studying the reactivity of MAE using nuclear magnetic resonance (NMR) spectroscopy have been performed. The present results indicate that the acid-catalyzed MAE reaction is more than 600 times slower than a similar reaction of an important isoprene-derived epoxide, but is still expected to be kinetically feasible in the atmosphere on more acidic SOA. The specific mechanism by which MAE leads to oligomers was identified, and the reactions of MAE with a number of atmospherically relevant nucleophiles were also investigated. Because the nucleophilic strengths of water, sulfate, alcohols (including 2-MG), and acids (including MAE and 2-MG) in their reactions with MAE were found to be of a similar magnitude, it is expected that a diverse variety of MAE + nucleophile product species may be formed on ambient SOA. Thus, the results indicate that epoxide chain reaction oligomerization will be limited by the presence of high concentrations of non-epoxide nucleophiles (such as water); this finding is consistent with previous environmental chamber investigations of the relative humidity-dependence of 2-MG-derived oligomerization processes and suggests that extensive oligomerization may not be likely on ambient SOA because of other competitive MAE reaction mechanisms.

Birdsall, A. W.; Miner, C. R.; Mael, L. E.; Elrod, M. J.

2014-08-01

269

Composition of Secondary Organic Aerosol from the Photolysis of 1-Nitronaphthalene  

NASA Astrophysics Data System (ADS)

Nitro-substituted polycyclic aromatic hydrocarbons are of interest due to their associated mutagenic and carcinogenic effects. 1-Nitronaphthalene is emitted directly from combustion processes such as vehicle exhaust, but is also formed through the reaction of naphthalene with the hydroxyl or nitrate radical in the presence of NOx. Photolysis has previously been demonstrated to be the major degradation pathway for 1-nitronaphthalene in the troposphere. In this study, a series of simulation chamber experiments has been performed to investigate the chemical composition of secondary organic aerosol (SOA) formed through the direct photolysis of 1-nitronaphthalene using an Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS, TSI). SOA forms rapidly with a yield of up to 50% depending on precursor concentration and photolysis rate. Along with expected products such as naphthoquinone and nitronaphthol, condensed species exhibiting mass spectra consistent with the presence of four aromatic rings were also observed. It is proposed that these species may be formed through dimerization of naphthoxy radicals generated during the photolysis process. Further evidence to support this mechanism was obtained when 1-nitronaphthalene was photolyzed in the presence of excess nitrobenzene. Dimers were then formed containing three aromatic rings, consistent with the reaction of phenoxy and naphthoxy radicals. The molecular formulae of the dimers were also confirmed by collecting SOA on filters and analysing the extracts off-line using an LTQ Orbitrap Velos mass spectrometer (Thermo-Fisher Scientific), fitted with a TriVersa NanoMate chip-based electrospray ionization source (Advion Biosystems). The rapid formation of condensable dimers through the self-reaction of naphthoxy radicals represents a previously unreported potential pathway to SOA formation. Analogous mechanisms may also be important for other nitrated polycyclic aromatic hydrocarbons.

Wenger, J.; Healy, R.; Chen, Y.; Kalberer, M.; Kourtchev, I.

2012-12-01

270

Formation and aging of secondary organic aerosol from isoprene photooxidation during cloud condensation-evaporation cycles  

NASA Astrophysics Data System (ADS)

Biogenic volatile organic compounds (BVOCs) can be oxidized in the gas phase to form more water-soluble compounds which could partition into atmospheric water droplets. Oxidation processes in the liquid phase could produce high molecular weight and less volatile compounds which can partly remain in the particle phase after water evaporation (Ervens et al., 2011). This work investigates the formation and composition of secondary organic aerosol (SOA) from the photooxidation of isoprene (the most abundant BVOC) and methacrolein (its main first-generation oxidation product). The experiments were performed during the CUMULUS (CloUd MULtiphase chemistry of organic compoUndS in the troposphere) campaigns at the 4.2 m3 stainless steel CESAM chamber at LISA, specifically designed to investigate multiphase processes (Wang et al., 2011). In each experiment, 500/1000 ppb of isoprene or methacrolein were injected in the chamber together with HONO before irradiation. Gas phase oxidation products have been analyzed on-line by a Proton Transfer Reaction Mass Spectrometer (PTR-MS) and a Fourier Transform Infrared Spectrometer (FTIR) together with NOx and O3 analyzers. SOA formation and composition has been followed on-line with a Scanning Mobility Particle Sizer (SMPS) and an Aerodyne High Resolution Time-Of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS). Particular attention has been focused on the study of SOA formation and aging during cloud condensation-evaporation cycles simulated in the smog chamber. In all experiments, we noted that water soluble gas-phase oxidation products readily partition into cloud droplets accompanied by a prompt SOA production during cloud formation which partly persists after cloud evaporation. Ervens, B. et al. (2011) Atmos. Chem. Phys. 11, 11069 11102. Wang, J. et al. (2011) Atmos. Measur. Tech. 4, 2465 2494.

Giorio, C.; Siekmann, F.; Bregonzio, L.; Temime-Roussel, B.; Ravier, S.; Tapparo, A.; Kalberer, M.; Doussin, J.; Monod, A.

2013-12-01

271

Novel methods for predicting gas-particle partitioning during the formation of secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Several methods have been presented in the literature to predict an organic chemical's equilibrium partitioning between the water insoluble organic matter (WIOM) component of aerosol and the gas phase, Ki, WIOM as a function of temperature. They include (i) polyparameter linear free energy relationships calibrated with empirical aerosol sorption data, as well as (ii) the solvation models implemented in SPARC and (iii) the quantum-chemical software Cosmotherm, which predict solvation equilibria from molecular structure alone. We demonstrate that these methods can be used to predict Ki, WIOM for large numbers of individual molecules implicated in secondary organic aerosol (SOA) formation, including those with multiple functional groups. Although very different in their theoretical foundations, these methods give remarkably consistent results for the products of the reaction of normal alkanes with OH, i.e. their partition coefficients Ki, WIOM generally agree within one order of magnitude over a range of more than ten orders of magnitude. This level of agreement is much better than that achieved by different vapour pressure estimation methods that are more commonly used in the SOA community. Also, in contrast to the agreement between vapour pressure estimates, that between the Ki, WIOM estimates does not deteriorate with increasing number of functional groups. Furthermore, these partitioning coefficients Ki, WIOM are found to predict the SOA mass yield in chamber experiments of the oxidation of normal alkanes as good or better than a vapour pressure based method. If a Ki, WIOM prediction method was based on one or more surrogate molecules representing the solvation properties of the mixed OM phase of SOA, the choice of those molecule(s) was found to have a relatively minor effect on the predicted Ki, WIOM, as long as the molecule(s) are not very polar. This suggests that a single surrogate molecule, such as 1-octanol or a hypothetical SOA structure proposed by Kalberer et al. (2004), may often be sufficient to represent the WIOM component of the SOA phase, greatly simplifying the prediction. The presented methods could substitute for vapour pressure based methods in studies such as the explicit modeling of SOA formation from single precursor molecules in chamber experiments or the assignment of SOA-forming molecules to volatility basis sets.

Wania, F.; Lei, Y. D.; Wang, C.; Abbatt, J. P. D.; Goss, K.-U.

2014-08-01

272

CCN activity and droplet growth kinetics of fresh and aged monoterpene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The ability of secondary organic aerosol (SOA) produced from the ozonolysis of ?-pinene and monoterpene mixtures (?-pinene, ?-pinene, limonene and 3-carene) to become cloud droplets was investigated. A static CCN counter and a Scanning Mobility CCN Analyser (a Scanning Mobility Particle Sizer coupled with a Continuous Flow counter) were used for the CCN measurements. Consistent with previous studies monoterpene SOA is quite active and would likely be a good source of cloud condensation nuclei (CCN) in the atmosphere. A decrease in CCN activation diameter for ?-pinene SOA of approximately 3 nm hr-1 was observed as the aerosol continued to react with oxidants. Hydroxyl radicals further oxidize the SOA particles thereby enhancing the particle CCN activity with time. The initial concentrations of ozone and monoterpene precursor (for concentrations lower than 40 ppb) do not appear to affect the activity of the resulting SOA. Köhler Theory Analysis (KTA) is used to infer the molar mass of the SOA sampled online and offline from atomized filter samples. The estimated average molar mass of online SOA was determined to be 180±55 g mol-1 (consistent with existing SOA speciation studies) assuming complete solubility. KTA suggests that the aged aerosol (both from ?-pinene and the mixed monoterpene oxidation) is primarily water-soluble (around 65%). CCN activity measurements of the SOA mixed with (NH4)2SO4 suggest that the organic can depress surface tension by as much as 10 N m-1 (with respect to pure water). The droplet growth kinetics of SOA samples are similar to (NH4)2SO4, except at low supersaturation, where SOA tends to grow more slowly. The CCN activation diameter of ?-pinene and mixed monoterpene SOA can be modelled to within 10 15% of experiments by a simple implementation of Köhler theory, assuming complete dissolution of the particles, no dissociation into ions, a molecular weight of 180 g mol-1, a density of 1.5 g cm-3, and the surface tension of water.

Engelhart, G. J.; Asa-Awuku, A.; Nenes, A.; Pandis, S. N.

2008-07-01

273

Water uptake is independent of the inferred composition of secondary aerosols derived from multiple biogenic VOCs  

NASA Astrophysics Data System (ADS)

We demonstrate that the water uptake properties derived from sub- and super-saturated measurements of chamber-generated biogenic secondary organic aerosol (SOA) particles are independent of their degree of oxidation determined using both online and offline methods. SOA particles are formed from the photooxidation of five structurally different biogenic VOCs representing a broad range of emitted species and their corresponding range of chemical reactivity: ?-pinene, ?-caryophyllene, limonene, myrcene and linalool. The fractional contribution of mass fragment 44 to the total organic signal (f44) is used to characterise the extent of oxidation of the formed SOA as measured online by an aerosol mass spectrometer. Results illustrate that the values of f44 are dependent on the precursor, the extent of photochemical ageing as well as on the initial experimental conditions. SOA generated from a single biogenic precursor should therefore not be used as a general proxy for biogenic SOA. Similarly, the generated SOA particles exhibit a range of hygroscopic properties depending on the precursor, its initial mixing ratio and photochemical ageing. The activation behaviour of the formed SOA particles show no temporal trends with photochemical ageing. The average ? values derived from the HTDMA and CCNc are generally found to cover the same range for each precursor under two different initial mixing ratio conditions. A positive correlation is observed between the hygroscopicity of particles of a single size and f44 for ?-pinene, ?-caryophyllene, linalool and myrcene, but not for limonene SOA. The investigation of the generality of this relationship reveal that ?-pinene, limonene, linalool and myrcene are all able to generate particles with similar hygroscopicity (?HTDMA ~0.1) despite f44 exhibiting a relatively wide range of values (~4 to 11%). Similarly, ?CCN is found to be independent of f44. The same findings are also true when sub- and super-saturated water uptake properties of SOA are compared to the averaged carbon oxidation state (OSC) determined using an off-line method. These findings do not necessarily suggest that water uptake and chemical composition are not related. Instead, they suggest that either f44 and OSC do not represent the main dominant composition-related factors controlling water uptake of SOA particles, or they emphasise the possible impact of semi-volatile compounds on limiting the ability of current state-of-the-art techniques to determine the chemical composition and water uptake properties of aerosol particles.

Alfarra, M. R.; Good, N.; Wyche, K. P.; Hamilton, J. F.; Monks, P. S.; Lewis, A. C.; McFiggans, G. B.

2013-04-01

274

Water uptake is independent of the inferred composition of secondary aerosols derived from multiple biogenic VOCs  

NASA Astrophysics Data System (ADS)

We demonstrate that the water uptake properties derived from sub- and super-saturated measurements of chamber-generated biogenic secondary organic aerosol (SOA) particles are independent of their degree of oxidation, determined using both online and offline methods. SOA particles are formed from the photooxidation of five structurally different biogenic VOCs, representing a broad range of emitted species and their corresponding range of chemical reactivity: ?-pinene, ?-caryophyllene, limonene, myrcene and linalool. The fractional contribution of mass fragment 44 to the total organic signal (f44) is used to characterise the extent of oxidation of the formed SOA as measured online by an aerosol mass spectrometer. Results illustrate that the values of f44 are dependent on the precursor, the extent of photochemical ageing as well as on the initial experimental conditions. SOA generated from a single biogenic precursor should therefore not be used as a general proxy for biogenic SOA. Similarly, the generated SOA particles exhibit a range of hygroscopic properties, depending on the precursor, its initial mixing ratio and photochemical ageing. The activation behaviour of the formed SOA particles show no temporal trends with photochemical ageing. The average ? values derived from the HTDMA and CCNc are generally found to cover the same range for each precursor under two different initial mixing ratio conditions. A positive correlation is observed between the hygroscopicity of particles of a single size and f44 for ?-pinene, ?-caryophyllene, linalool and myrcene, but not for limonene SOA. The investigation of the generality of this relationship reveals that ?-pinene, limonene, linalool and myrcene are all able to generate particles with similar hygroscopicity (?HTDMA ~0.1) despite f44 exhibiting a relatively wide range of values (~4 to 11%). Similarly, ?CCN is found to be independent of f44. The same findings are also true when sub- and super-saturated water uptake properties of SOA are compared to the averaged carbon oxidation state (OSC) determined using an offline method. These findings do not necessarily suggest that water uptake and chemical composition are not related. Instead, they suggest that either f44 and OSC do not represent the main dominant composition-related factors controlling water uptake of SOA particles, or they may emphasise the possible impact of semi-volatile compounds on limiting the ability of current state-of-the-art techniques to determine the chemical composition and water uptake properties of aerosol particles.

Alfarra, M. R.; Good, N.; Wyche, K. P.; Hamilton, J. F.; Monks, P. S.; Lewis, A. C.; McFiggans, G.

2013-12-01

275

Campholenic aldehyde ozonolysis: a possible mechanism for the formation of specific biogenic secondary organic aerosol constituents  

NASA Astrophysics Data System (ADS)

In the present study, campholenic aldehyde ozonolysis was performed to investigate pathways leading to specific biogenic secondary organic aerosol (SOA) marker compounds. Campholenic aldehyde, a known ?-pinene oxidation product, is suggested to be a key intermediate in the formation of terpenylic acid upon ?-pinene ozonolysis. It was reacted with ozone in the presence and absence of an OH radical scavenger leading to SOA formation with a yield of 0.75 and 0.8, respectively. The resulting oxidation products in the gas and particle phases were investigated employing a denuder/filter sampling combination. Gas-phase oxidation products bearing a carbonyl group, which were collected by the denuder, were derivatised with 2,4-dinitrophenylhydrazine (DNPH) followed by Liquid Chromatography/negative ion Electrospray Ionisation Time-of-Flight Mass Spectrometry analysis and were compared to the gas-phase compounds detected by online Proton-Transfer-Reaction Mass Spectrometry. Particle-phase products were also analysed, directly or after DNPH derivatisation, to derive information about specific compounds leading to SOA formation. Among the detected compounds, the aldehydic precursor of terpenylic acid was identified and its presence was confirmed in ambient aerosol samples from the DNPH derivatisation, accurate mass data, and MS2 and MS3 fragmentation studies. Furthermore, the present investigation sheds light on a reaction pathway leading to the formation of terpenylic acid, involving ?-pinene, ?-pinene oxide, campholenic aldehyde, and terpenylic aldehyde. Additionally, the formation of diaterpenylic acid acetate could be connected to campholenic aldehyde oxidation. The present study also provides insights into the source of other highly functionalised oxidation products (e.g. m/z 201, C9H14O5 and m/z 215, C10H16O5), which have been observed in ambient aerosol samples and smog chamber-generated monoterpene SOA. The m/z 201 and 215 compounds were tentatively identified as a C9- and C10-carbonyl-dicarboxylic acid, respectively, based on reaction mechanisms of campholenic aldehyde and ozone, detailed interpretation of mass spectral data, in conjunction with the formation of corresponding DNPH-derivatives.

Kahnt, A.; Iinuma, Y.; Mutzel, A.; Böge, O.; Claeys, M.; Herrmann, H.

2013-08-01

276

Campholenic aldehyde ozonolysis: a mechanism leading to specific biogenic secondary organic aerosol constituents  

NASA Astrophysics Data System (ADS)

In the present study, campholenic aldehyde ozonolysis was performed to investigate pathways leading to specific biogenic secondary organic aerosol (SOA) marker compounds. Campholenic aldehyde, a known ?-pinene oxidation product, is suggested to be a key intermediate in the formation of terpenylic acid upon ?-pinene ozonolysis. It was reacted with ozone in the presence and absence of an OH radical scavenger, leading to SOA formation with a yield of 0.75 and 0.8, respectively. The resulting oxidation products in the gas and particle phases were investigated employing a denuder/filter sampling combination. Gas-phase oxidation products bearing a carbonyl group, which were collected by the denuder, were derivatised by 2,4-dinitrophenylhydrazine (DNPH) followed by liquid chromatography/negative ion electrospray ionisation time-of-flight mass spectrometry analysis and were compared to the gas-phase compounds detected by online proton-transfer-reaction mass spectrometry. Particle-phase products were also analysed, directly or after DNPH derivatisation, to derive information about specific compounds leading to SOA formation. Among the detected compounds, the aldehydic precursor of terpenylic acid was identified and its presence was confirmed in ambient aerosol samples from the DNPH derivatisation, accurate mass data, and additional mass spectrometry (MS2 and MS3 fragmentation studies). Furthermore, the present investigation sheds light on a reaction pathway leading to the formation of terpenylic acid, involving ?-pinene, ?-pinene oxide, campholenic aldehyde, and terpenylic aldehyde. Additionally, the formation of diaterpenylic acid acetate could be connected to campholenic aldehyde oxidation. The present study also provides insights into the source of other highly functionalised oxidation products (e.g. m / z 201, C9H14O5 and m / z 215, C10H16O5), which have been observed in ambient aerosol samples and smog chamber-generated monoterpene SOA. The m / z 201 and 215 compounds were tentatively identified as a C9- and C10-carbonyl-dicarboxylic acid, respectively, based on reaction mechanisms of campholenic aldehyde and ozone, as well as detailed interpretation of mass spectral data, in conjunction with the formation of corresponding DNPH derivatives.

Kahnt, A.; Iinuma, Y.; Mutzel, A.; Böge, O.; Claeys, M.; Herrmann, H.

2014-01-01

277

Secondary Aerosol Formation in the planetary boundary layer observed by aerosol mass spectrometry on a Zeppelin NT  

NASA Astrophysics Data System (ADS)

The airship Zeppelin NT is an airborne platform capable of flying at low speed throughout the entire planetary boundary layer (PBL). In combination with the high scientific payload of more than 1 ton, the Zeppelin is an ideal platform to study regional processes in the lowest layers of the atmosphere with high spatial resolution. Atmospheric aerosol as a medium long lived tracer substance is of particular interest due to its influence on the global radiation budget. Due its lifetime of up to several days secondaray aerosol at a certain location can result from local production or from transport processes. For aerosol measurements on a Zeppelin, a High-Resolution Time-of-Flight Aerosol Mass spectrometer (DeCarlo et al, 2006) was adapted to the requirements posed by an airborne platform. A weight reduction of over 20 % compared to the commercial instrument was achieved, while space occupation and footprint were each reduced by over 25 %. Within the PEGASOS project, the instrument was part of 10 measurement flight days over the course of seven weeks. Three flights were starting from Rotterdam, NL, seven flights were starting from Ozzano in the Po Valley, IT. Flight patterns included vertical profiles to study the dynamics of the PBL and cross sections through regions of interest to shed light on local production and transport processes. Analysis of data from transects between the Apennin and San Pietro Capofiume in terms of "residence time of air masses in the Po valley" indicates that aerosol nitrate has only local sources while aerosol sulfate is dominated by transport. The organic aerosol component has significant contributions of both processes. The local prodcution yields are commensurable with imultaneously observed precursor concentrations and oxidant levels. The PEGASOS project is funded by the European Commission under the Framework Programme 7 (FP7-ENV-2010-265148). DeCarlo, P.F. et al (2006), Anal. Chem., 78, 8281-8289.

Rubach, Florian; Trimborn, Achim; Mentel, Thomas; Wahner, Andreas; Zeppelin Pegasos-Team 2012

2014-05-01

278

Aerosol liquid water driven by anthropogenic nitrate: implications for lifetimes of water-soluble organic gases and potential for secondary organic aerosol formation.  

PubMed

Aerosol liquid water (ALW) influences aerosol radiative properties and the partitioning of gas-phase water-soluble organic compounds (WSOCg) to the condensed phase. A recent modeling study drew attention to the anthropogenic nature of ALW in the southeastern United States, where predicted ALW is driven by regional sulfate. Herein, we demonstrate that ALW in the Po Valley, Italy, is also anthropogenic but is driven by locally formed nitrate, illustrating regional differences in the aerosol components responsible for ALW. We present field evidence for the influence of controllable ALW on the lifetimes and atmospheric budgets of reactive organic gases and note the role of ALW in the formation of secondary organic aerosol (SOA). Nitrate is expected to increase in importance due to increased emissions of nitrate precursors, as well as policies aimed at reducing sulfur emissions. We argue that the impacts of increased particulate nitrate in future climate and air quality scenarios may be under predicted because they do not account for the increased potential for SOA formation in nitrate-derived ALW, nor do they account for the impacts of this ALW on reactive gas budgets and gas-phase photochemistry. PMID:25191968

Hodas, Natasha; Sullivan, Amy P; Skog, Kate; Keutsch, Frank N; Collett, Jeffrey L; Decesari, Stefano; Facchini, M Cristina; Carlton, Annmarie G; Laaksonen, Ari; Turpin, Barbara J

2014-10-01

279

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

NASA Astrophysics Data System (ADS)

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 had negligible influence on production of secondary organic aerosol. Details of the finding and related contribution of sources to SOA will be presented.

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

2011-12-01

280

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

NASA Astrophysics Data System (ADS)

Environmental chamber ("smog chamber") experiments were conducted to investigate secondary organic aerosol (SOA) production from dilute emissions from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel vehicles (HDDVs) under urban-like conditions. Some of the vehicles were equipped with emission control aftertreatment devices including diesel particulate filters (DPF), selective catalytic reduction (SCR) and diesel oxidation catalysts (DOC). Experiments were also performed with different fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur diesel) and driving cycles (Unified Cycle, Urban Dynamometer Driving Schedule, and creep+idle). During normal operation, vehicles with a catalyzed DPF emitted very little primary particulate matter (PM). Furthermore, photo-oxidation of dilute emissions from these vehicles produced essentially no SOA (below detection limit). However, significant primary PM emissions and SOA production were measured during active DPF regeneration experiments. Nevertheless, under reasonable assumptions about DPF regeneration frequency, the contribution of regeneration emissions to the total vehicle emissions is negligible, reducing PM trapping efficiency by less than 2%. Therefore, catalyzed DPFs appear to be very effective in reducing both primary and secondary fine particulate matter from diesel vehicles. For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the smog chamber - with the emissions from some vehicles generating twice as much SOA as primary organic aerosol after three hours of oxidation at typical urban VOC : NOx ratios (3:1). Comprehensive organic gas speciation was performed on these emissions, but less than half of the measured SOA could be explained by traditional (speciated) SOA precursors. The remainder presumably originates from the large fraction (~30%) of the non-methane organic gas emissions that could not be speciated using traditional one-dimensional gas-chromatography. The unspeciated organics - likely comprising less volatile species, such as intermediate volatility organic compounds - appear to be important SOA precursors; we estimate that the effective SOA yield (defined as the ratio of SOA mass to reacted precursor mass) was 9 ± 6% if both speciated SOA precursors and unspeciated organics are included in the analysis. SOA production from creep+idle operation was 3-4 times larger than SOA production from the same vehicle operated over the Urban Dynamometer Driving Schedule (UDDS). Fuel properties had little or no effect on primary PM emissions or SOA formation.

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

2013-09-01

281

Real-Time Observations of Secondary Aerosol Formation and Aging from Different Emission Sources and Environments  

NASA Astrophysics Data System (ADS)

To investigate atmospheric processing of direct urban and wildfire emissions, we deployed a photochemical flow reactor (Potential Aerosol Mass, PAM) with submicron aerosol size and chemical composition measurements during FLAME-3, a biomass-burning study at USDA Fire Sciences Laboratory in Missoula, MT, and CalNex, a field study investigating the nexus of air quality and climate change at a receptor site in the LA-Basin at Pasadena, CA. The reactor produces OH concentrations up to 4 orders of magnitude higher than in ambient air, achieving equivalent aging of ~2 weeks in 5 minutes of processing. The OH exposure (OHexp) was stepped every 20 min in both field studies. Results show the value of this approach as a tool for in-situ evaluation of changes in OA concentration and composition due to photochemical processing. In FLAME-3, the average OA enhancement factor was 1.42 × 0.36 of the initial POA. Reactive VOCs, such as toluene, monoterpenes, and acetaldehyde, decreased with increased OHexp; however, formic acid, acetone, and some unidentified OVOCs increased after significant exposure. Net SOA formation in the photochemical reactor increased with OHexp, typically peaking around 3 days of equivalent atmospheric photochemical age (OHexp ~3.9e11 molecules cm-3 s), then leveling off at higher exposures. Unlike other studies, no decrease in OA is observed at high exposure, likely due to lower max OHexp in this study due to very high OH reactivity. 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 exceeded the mass of the known VOC precursors, indicating the likely importance of primary semivolatile/intermediate volatility species, and possibly of unidentified VOCs as SOA precursors in biomass burning smoke. Results from CalNex show enhancement of OA and inorganic aerosol from gas-phase precursors. The OA mass enhancement from aging was highest at night and correlated with trimethylbenzene concentrations, indicating the dominance of highly reactive VOC emissions as SOA precursors in the LA Basin. Aging in the reactor mimics atmospheric processing as the elemental composition of ambient and reactor measurements, when plotted in a Van Krevelen diagram, follow similar slopes; additionally, reactor measurements extend over a larger range of oxygen-to-carbon ratios (O/C) compared to that observed in the LA-Basin. While reactor aging always increases O/C, often beyond maximum ambient levels, we observe a transition from functionalization to fragmentation oxidation reactions at intermediate OHexp, with fragmentation dominating at very high OHexp. Maximum net SOA production is observed between 3-6 days of aging and decreases at higher exposures. A traditional SOA model with mostly aromatic precursors underpredicts the amount of SOA formed by an order-of-magnitude, which is consistent with model evaluations for ambient air at many polluted locations.

Ortega, A. M.; Palm, B. B.; Hayes, P. L.; Day, D. A.; Cubison, M.; Brune, W. H.; Hu, W.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; Rappenglueck, B.; Bon, D.; Graus, M.; Warneke, C.; Gilman, J.; Kuster, W.; De Gouw, J. A.; Jimenez, J. L.

2013-12-01

282

Size distribution and chemical composition of secondary organic aerosol formed from C1-initiated oxidation of toluene.  

PubMed

Secondary organic aerosol (SOA) formed from C1-initiated oxidation of toluene was investigated in a home-made smog chamber. The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS), respectively. According to a large number of single aerosol diameter and mass spectra, the size distribution and chemical composition of SOA were obtained statistically. Experimental results showed that SOA particles created by C1-initiated oxidation of toluene is predominantly in the form of fine particles, which have diameters less than 2.5 microm (i.e., PM2.5), and glyoxal, benzaldehyde, benzyl alcohol, benzoquinone, benzoic acid, benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA. The possible reaction mechanisms leading to these products are also proposed. PMID:22893963

Huang, Mingqiang; Zhang, Weijun; Gu, Xuejun; Hu, Changjin; Zhao, Weixiong; Wang, Zhenya; Fang, Li

2012-01-01

283

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)

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 al. Photolytic processing of secondary organic aerosols dissolved in cloud droplets. Phys. Chem. Chem. Phys. 2011, 13, 12199. Nguyen et al. Direct aqueous photochemistry of isoprene high-NOx secondary organic aerosol. Phys. Chem. Chem. Phys. 2012, 14, 9702. Walser et al. Photochemical aging of secondary organic aerosol particles generated from the oxidation of d-limonene. J. Phys. Chem. A 2007, 111, 1907.

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

2013-12-01

284

Proposed chemical mechanisms leading to secondary organic aerosol in the reactions of aliphatic amines with hydroxyl and nitrate radicals  

NASA Astrophysics Data System (ADS)

The presence and importance of amines in the atmosphere, including aliphatic amines, continues to gain more attention. The atmospheric reaction mechanisms of these amines with key atmospheric radicals are important to predict both daytime and nighttime atmospheric chemistry. While previous studies have focused on the production of amine salts, this analysis looks at the importance of peroxy radical reactions to the formation of secondary organic aerosol. Atmospheric oxidation mechanisms are presented to explain the observed chemistry. A series of environmental chamber experiments were conducted in which aliphatic tertiary and secondary amines were reacted with either hydroxyl radical (OH) or nitrate radical (NO3). Chemical composition of the aerosol products was obtained with a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a Particle Into Liquid Sampler Time of Flight Mass Spectrometer (PILS-ToF-MS), while the chemical composition of the gas-phase products was obtained with a Selected Ion Flow Tube Mass Spectrometer (SIFT-MS). A number of aerosol-phase mass spectra showed highly oxidized fragments at a much higher molecular weight (MW) than the amine precursor. It is proposed that these larger compounds are oligomers formed through peroxy radical reactions with hydrogen rearrangement. Another reaction pathway observed was the formation of amine salts. The relative importance of each pathway to the overall production of aerosol is found to be dependent on the type of amine and oxidant. For example, the oligomers were observed in the tertiary methyl amines, while the formation of amine salts was more prevalent in the secondary and tertiary ethyl amines.

Price, Derek J.; Clark, Christopher H.; Tang, Xiaochen; Cocker, David R.; Purvis-Roberts, Kathleen L.; Silva, Philip J.

2014-10-01

285

Aqueous Oxidation of Green Leaf Volatiles as a Source of Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Vegetation emits volatile oxygenated hydrocarbons - the green leaf volatiles (GLVs) - which are formed from the biochemical conversion of linoleic and linolenic acids within plant cells. Stress or damage to vegetation can significantly elevate emission fluxes of these compounds, some of which are fairly water soluble. Aqueous-phase reactions of the GLVs with photochemically generated oxidants - such as hydroxyl radical (OH), singlet oxygen (1O2) and excited triplet states of organic compounds (3C*) _ might then form low-volatility products that can act as secondary organic aerosol (SOA). In order to determine if GLVs can be a significant source of secondary organic carbon in fogwater, studies of GLVs in laboratory solutions are needed to elucidate the oxidation kinetics and the corresponding SOA mass yields. In this study we are determining the second-order rate constants, and SOA mass yields, for five GLVs (cis-3-hexen-1-ol, cis-3-hexenylacetate, methyl salicylate, methyl jasmonate, and 2-methyl-3-butene-2-ol) reacting with OH,1O2 and 3C*. Experiments are performed at relevant fog water pHs, temperatures, and oxidant concentrations. Rate constants are determined using a relative rate approach in which the decay of GLVs and reference compounds are monitored as function of time by HPLC. The capacity of GLVs to form aqueous SOA was determined by following the formation of their decomposition products with HPLC-UV/DAD and HPLC-ESI/MS. SOA mass yields are measured gravimetrically from laboratory solutions containing atmospherically relevant concentrations of photooxidants and GLVs, and irradiated with simulated sunlight. We will use our results to assess the potential contribution of aqueous GLV reactions as a source of SOA in cloudy or foggy atmospheres.

Richards-Henderson, N. K.; Hansel, A.; Pham, A. T.; Vempati, H. S.; Valsaraj, K. T.; Anastasio, C.

2013-12-01

286

3rd hand smoking; heterogeneous oxidation of nicotine and secondary aerosol formation in the indoor environment  

NASA Astrophysics Data System (ADS)

Tobacco smoking is well known as a significant source of primary indoor air pollutants. However, only recently has it been recognized that the impact of Tobacco smoking may continue even after the cigarette has been extinguished (i.e., third hand smoke) due to the effect of indoor surfaces. These surfaces may affect the fate of tobacco smoke in the form of secondary reactions and pollutants, including secondary organic aerosol (SOA) formation. Fourier Transform Infrared spectrometry with Attenuated Total Reflection (FTIR-ATR) in tandem with a Scanning Mobility Particle Sizing (SMPS) system was used to monitor the ozonation of cellulose sorbed nicotine and resulting SOA formation. SOA formation began at onset of ozone introduction ([O3] = 60 ± 5 ppb) with a size distribution of dp ? 25 nm, and was determined to be a result of heterogeneous reaction (opposed to homogeneous). SOA yield from reacted surface nicotine was on the order of 10 %. Simultaneous to SOA monitoring, FTIR-ATR spectra showed surface changes in the nicotine film as the reaction progressed, revealing a pseudo first-order surface reaction rate of 0.0026 ± 0.0008 min-1. Identified surface oxidation products included: cotinine, myosmine, methylnicotinamide and nicotyrine. Surface reaction rate was found to be partially inhibited at high relative humidity. Given the toxicity of some of the identified products (e.g., cotinine has shown potential mutagenicity and teratogenicity) and that small particles may contribute to adverse health effects, the present study indicates that exposure to 3rd hand smoke ozonation products may pose additional health risks.

Petrick, Lauren; Dubowski, Yael

2010-05-01

287

Synergy between Secondary Organic Aerosols and Long Range Transport of Polycyclic Aromatic Hydrocarbons  

SciTech Connect

Polycyclic aromatic hydrocarbons (PAHs) known for their harmful health effects undergo long-range transport (LRT) when adsorbed on and/or absorbed in atmospheric particles. The association between atmospheric particles, PAHs, and their LRT has been the subject of many studies, yet remains poorly understood. Current models assume PAHs instantaneously attain reversible gas-particle equilibrium. In this paradigm, during LRT, as gas-phase PAHs concentrations are depleted due to oxidation and dilution, particle-bound PAHs rapidly evaporate to re-establish equilibrium, leading to severe underpredictions of LRT potential of particle-bound PAHs. Here we present a new, experimentally based picture, in which the PAHs become trapped inside highly viscous quasi-solid secondary organic aerosol (SOA) particles during particle formation, and thus prevented from evaporation, and shielded from oxidation. In contrast, surface-adsorbed PAHs rapidly evaporate, leaving no trace behind. We find synergetic effects between PAHs and SOA, in that the presence of PAHs inside SOA particles drastically slows SOA evaporation to the point that it can be ignored, and the highly viscous SOA prevents PAHs evaporation assuring efficient LRT. The data show that the assumptions of instantaneous reversible gas-particle equilibrium for PAHs and for SOA are fundamentally flawed, providing explanation for the persistent discrepancy between observed and predicted particle-bound PAHs.

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

2012-10-25

288

Filterable redox cycling activity: a comparison between diesel exhaust particles and secondary organic aerosol constituents.  

PubMed

The redox activity of diesel exhaust particles (DEP) collected from a light-duty diesel passenger car engine was examined using the dithiothreitol (DTT) assay. DEP was highly redox-active, causing DTT to decay at a rate of 23-61 pmol min(-1) ?g(-1) of particle used in the assay, which was an order of magnitude higher than ambient coarse and fine particulate matter (PM) collected from downtown Toronto. Only 2-11% of the redox activity was in the water-soluble portion, while the remainder occurred at the black carbon surface. This is in contrast to redox-active secondary organic aerosol constituents, in which upward of 90% of the activity occurs in the water-soluble fraction. The redox activity of DEP is not extractable by moderately polar (methanol) and nonpolar (dichloromethane) organic solvents, and is hypothesized to arise from redox-active moieties contiguous with the black carbon portion of the particles. These measurements illustrate that "Filterable Redox Cycling Activity" may therefore be useful to distinguish black carbon-based oxidative capacity from water-soluble organic-based activity. The difference in chemical environment leading to redox activity highlights the need to further examine the relationship between activity in the DTT assay and toxicology measurements across particles of different origins and composition. PMID:23470039

McWhinney, Robert D; Badali, Kaitlin; Liggio, John; Li, Shao-Meng; Abbatt, Jonathan P D

2013-04-01

289

The effects of increasing atmospheric ozone on biogenic monoterpene profiles and the formation of secondary aerosols  

NASA Astrophysics Data System (ADS)

Monoterpenes are biogenic volatile organic compounds (BVOCs) which play an important role in plant adaptation to stresses, atmospheric chemistry, plant-plant and plant-insect interactions. In this study, we determined whether ozonolysis can influence the monoterpenes in the headspace of cabbage. The monoterpenes were mixed with an air-flow enriched with 100, 200 or 400 ppbv of ozone (O 3) in a Teflon chamber. The changes in the monoterpene and O 3 concentrations, and the formation of secondary organic aerosols (SOA) were determined during ozonolysis. Furthermore, the monoterpene reactions with O 3 and OH were modelled using reaction kinetics equations. The results showed that all of the monoterpenes were unequally affected: ?-thujene, sabinene and D-limonene were affected to the greatest extend, whereas the 1,8-cineole concentration did not change. In addition, plant monoterpene emissions reduced the O 3 concentration by 12-24%. The SOA formation was dependent on O 3 concentration. At 100 ppbv of O 3, virtually no new particles were formed but clear SOA formation was observed at the higher ozone concentrations. The modelled results showed rather good agreements for ?-pinene and 1,8-cineole, whereas the measured concentrations were clearly lower compared to modelled values for sabinene and limonene. In summary, O 3-quenching by monoterpenes occurs beyond the boundary layer of leaves and results in a decreased O 3 concentration, altered monoterpene profiles and SOA formation.

Pinto, Delia M.; Tiiva, Päivi; Miettinen, Pasi; Joutsensaari, Jorma; Kokkola, Harri; Nerg, Anne-Marja; Laaksonen, Ari; Holopainen, Jarmo K.

290

Gaseous products and Secondary Organic Aerosol formation during long term oxidation of isoprene and methacrolein  

NASA Astrophysics Data System (ADS)

First- and higher-generation products from the oxidation of isoprene and methacrolein with OH radicals in the presence of NOx have been studied in a simulation chamber: (1) significant oxidation rates have been maintained for up to 7 h allowing the study of highly oxidized products, (2) gas-phase products distribution and yields are provided, and show good agreement with previous studies. Secondary organic aerosol (SOA) formation resulting from these experiments has also been investigated. Among the general dispersion exhibited by SOA mass yields from previous studies, the mass yields obtained here were consistent with the lowest values found in the literature, and more specifically in agreement with studies carried out with natural light or artificial lamps with emission spectrum similar to the solar one. An effect of light source is hence proposed to explain, at least in part, the discrepancies observed between different studies in the literature for both isoprene- and methacrolein-SOA mass yields. A high degree of similarity is shown in the comparison of SOA mass spectra from isoprene and methacrolein photooxidation, thus strengthening the importance of the role of methacrolein in SOA formation from isoprene photooxidation under our experimental conditions (i.e. presence of NOx and long term oxidation). Overall, if these results are further confirmed, SOA mass yields from both isoprene and methacrolein in the atmosphere could be lower than suggested by most of the current chamber studies.

Brégonzio-Rozier, L.; Siekmann, F.; Giorio, C.; Pangui, E.; Morales, S. B.; Temime-Roussel, B.; Gratien, A.; Michoud, V.; Ravier, S.; Tapparo, A.; Monod, A.; Doussin, J.-F.

2014-09-01

291

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

SciTech Connect

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.

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

2011-07-06

292

Impact of Propene on Secondary Organic Aerosol Formation from m-Xylene  

SciTech Connect

Propene is widely used in smog chamber experiments to increase the hydroxyl radical (OH) level based on the assumption that the formation of secondary organic aerosol (SOA) from parent hydrocarbon is unaffected. A series ofm-xylene/NOx photooxidation experiments were conducted in the presence of propene in the University of California CECERT atmospheric chamber facility. The experimental data are compared with previousm-xylene/NOx photooxidation work performed in the same chamber facility in the absence of propene (Song et al. Environ. Sci. Technol. 2005, 39, 3143-3149). The result shows that, for similar initial conditions, experiments with propene have lower reaction rates of m-xylene than those without propene, which indicates that propene reduces OH in the system. Furthermore, experiments with propene showed more than 15% reduction in SOA yield compared to experiments in the absence of propene. Additional experiments ofm-xylene/NOx with CO showed similar trends of suppressing OH and SOA formation. These results indicate that SOA from m-xylene/NOx photooxidation is strongly dependent on the OH level present, which provides evidence for the critical role of OH in SOA formation from aromatic hydrocarbons.

Song, Chen; Na, Kwangsam; Warren, Bethany; Malloy, Quentin; Cocker, David R.

2007-10-15

293

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

SciTech Connect

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

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

2008-01-01

294

Characteristics of water-soluble inorganic and organic ions in aerosols over the Southern Ocean and coastal East Antarctica during austral summer  

NASA Astrophysics Data System (ADS)

characterize the concentrations and size distributions of water-soluble organic and inorganic aerosol species, including Na+, non-sea-salt sulfate (nss SO42-), methane sulfonate (MSA), oxalate, and succinate, over the Southern Ocean (SO) and coastal East Antarctica (CEA), bulk and size-segregated aerosols were collected from 40°S, 100°E to 69°S, 76°E and between 69°S, 76°E and 66°S, 110°E during a cruise from November 2010 to March 2011. Results show that sea salt was the major component of the total aerosol mass, accounting for 72% over the SO and 56% over CEA. The average concentrations of nss SO42- varied from 420 ng m-3 over the SO to 480 ng m-3 over CEA. The concentrations of MSA ranged from 63 to 87 ng m-3 over the SO and from 46 to 170 ng m-3 in CEA. The average concentrations of oxalate were 3.8 ng m-3 over the SO and 2.2 ng m-3 over CEA. The concentrations of formate, acetate, and succinate were lower than those of oxalate. A bimodal size distribution of aerosol mass existed over CEA, peaking at 0.32-0.56 µm and 3.2-5.6 µm. MSA was accumulated in particles of 0.32-0.56 µm over CEA. High chloride depletion was associated with fine-mode particles enriched with nss SO42-, MSA, and oxalate. Higher cation-to-anion and NH4+/nss SO42- ratios in aerosols over CEA compared to that over the SO imply the higher neutralization capacity of the marine atmosphere over CEA.

Xu, Guojie; Gao, Yuan; Lin, Qi; Li, Wei; Chen, Liqi

2013-12-01

295

Aerosol Precursor Emissions, Secondary Aerosol Production, and Climate-Forcing Gas Exchange in the Midwestern United States  

Microsoft Academic Search

Aerosol precursors in the Midwest are generated from a myriad of sources including biogenic emissions of terpenes from the Ozarks region, anthropogenic emissions of volatile and semivolatile aliphatic and aromatic hydrocarbons from the St. Louis airshed, and agricultural emissions of ammonia (NH3), amines, and nitrogen oxides (NOx) from animal husbandry and cropping systems of the Midwest Corn Belt. The deciduous

P. V. Doskey

2009-01-01

296

2-Hydroxyterpenylic acid: An oxygenated marker compound for a-pinene secondary organic aerosol in ambient fine aerosol  

EPA Science Inventory

An oxygenated MW 188 compound is commonly observed in substantial abundance in atmospheric aerosol samples and was proposed in previous studies as an a-pinene-related marker compound that is associated with aging processes. Owing to difficulties in producing this compound in suff...

297

Speciation of water-soluble inorganic, organic, and total nitrogen in a background marine environment: Cloud water, rainwater, and aerosol particles  

NASA Astrophysics Data System (ADS)

Cloud water, rainwater, and aerosol particles were collected in Puerto Rico from December 2004 to March 2007 in order to investigate their chemical composition, relation to sources, and removal processes. The species analyzed were inorganic ions, metals, total and dissolved organic carbon (TOC, DOC), total nitrogen (TN), and organic acids. For all samples, the dominant species were marine (Na+, Cl-), representing about 50%-65% of total content. Non-sea-salt fraction was dominated by SO42- (17%-25%), followed by water-soluble organic (2%-8%) and total nitrogen (2% -6%) compounds. Organic acids represented contributions to the organic fraction in cloud water of 20% and 6% for aerosol particles. Inorganic species were predominant in total nitrogen portion. The chemical composition of cloud water, rainwater, and aerosol particles were observed to be sensitive to transport patterns. Air masses from northwest Africa showed the highest concentrations of nss-Ca2+, Fe, and Al, suggesting a crustal origin. The pH values for cloud water and rainwater observed under this transport pattern were higher than background conditions, probably due to the alkalinity associated with nss-Ca2+. The highest concentrations of Cl- and SO42-, with lower pH, were measured during periods of influence from Soufriere Hills volcano eruptions, most likely due to emitted SO2 and HCl. Air masses from North America had an anthropogenic influence, where levels of nss-SO42-, TOC, and TN were higher (˜4 times) than in clean air masses. These results suggest that long-range transport could be an extra source of metals and organic/nitrogen species to the Caribbean region ecosystems.

Gioda, Adriana; Reyes-RodríGuez, Gabriel J.; Santos-Figueroa, Gilmarie; Collett, Jeffrey L.; Decesari, Stefano; Ramos, Maria Da ConceiçÃ.£O. K. V.; Bezerra Netto, Heleno J. C.; de Aquino Neto, Francisco R.; Mayol-Bracero, Olga L.

2011-03-01

298

Source Apportionment of Primary and Secondary Organic Aerosols in Southern California during the 2005 Study of Organic Aerosols in Riverside (SOAR-1)  

NASA Astrophysics Data System (ADS)

Ambient sampling was conducted in Riverside, California during the 2005 Study of Organic Aerosols in Riverside (SOAR-1) to characterize the composition and sources of organic aerosol using a variety of state-of-the-art instrumentation and source apportionment techniques. The secondary organic aerosol (SOA) mass is estimated by elemental carbon and carbon monoxide tracer methods, water soluble organic carbon content, chemical mass balance of organic molecular markers, and positive matrix factorization of high-resolution aerosol mass spectrometer data. Estimates obtained from each of these methods indicate that the organic fraction in ambient aerosol is overwhelmingly secondary in nature during a period of several weeks with moderate ozone concentrations and that SOA is the single largest component of PM1 aerosol in Riverside. Average SOA/OA contributions of 70-90% were observed during mid-day periods while minimum SOA/OA contributions of 45% were observed during peak morning traffic periods. These results are contrary to previous estimates of SOA throughout the Los Angeles Basin which reported that, other than during severe photochemical smog episodes, SOA was lower than primary OA. Possible reasons for these differences include: (a) for studies that used the EC-tracer method, a large systematic underestimation of SOA can occur when primary OC/EC ratios are derived from ambient measurements during periods "dominated by POA" since there is almost always a large SOA background present (Zhang et al., ACP, 2005); and (b) for model-based studies a large underestimation of SOA is observed for this area, consistent with previous studies (e.g. Volkamer et al., GRL, 2006). The results of the PMF analysis of high-resolution AMS spectra will also be summarized, and tracers from 1-hr data from the thermal-aerosol-GCMS instrument (TAG, Williams et al., JGR 2007) are used to help the interpretation of the AMS components. PMF is applied both to ambient-only and ambient plus thermally-denuded data, the latter of which is shown to enhance the separation of AMS components and which also provides information on their volatilities. We identify six OA components. Three of these components are likely primary and are characterized by a wide range of volatilities. These include a reduced hydrocarbon-like OA (HOA) which correlates with combustion emission tracers and two minor (3% of the OA mass each) components, one of which is strongly associated with amines. The majority ( 80%) of the OA is composed of oxidized components (OOA) which are of likely secondary origin. These include a highly oxidized, low volatility regional background OOA-1 component and a less oxidized, high volatility nitrate-associated OOA-3 component, each of which have been reported from previous AMS PMF analyses. We also report for the first time the presence of a secondary OA component which is intermediate in both extent of oxidation and volatility (OOA-2). Biomass burning makes a negligible impact to OA during SOAR-1, a result that is consistent across all the apportionment methods as well as ATOFMS data.

Docherty, K. D.; Jimenez, J. L.; Stone, E. A.; Ulbrich, I. M.; Decarlo, P. F.; Schauer, J. J.; Williams, B.; Goldstein, A. H.; Peltier, R.; Weber, R.

2009-04-01

299

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

NASA Astrophysics Data System (ADS)

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 (?-pinene, ?-pinene, ?3-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 ?-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 laboratory measurements with the ambient atmosphere, this paper also compares filter samples taken at the Finnish Forest Research Station in Hyytiälä to the filter samples obtained from SAPHIR/AIDA experiments. 1. Rudich, Y., N.M. Donahue, and T.F. Mentel (2007) Annual Review of Physical Chemistry 58: 321-352 2. Szmigielski, R., J.D. Surratt, Y. Gomez-Gonzalez, P. Van der Veken, I. Kourtchev, R. Vermeylen, F. Blockhuys, M. Jaoui, T.E. Kleindienst, M. Lewandowski, J.H. Offenberg, E.O. Edney, J.H. Seinfeld, W. Maenhaut, and M. Claeys (2007) Geophysical Research Letters 34(24)

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

2009-04-01

300

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

NASA Astrophysics Data System (ADS)

Two new secondary organic aerosol (SOA) modeling frameworks are developed, one based on an aromatic gas and particle-phase kinetic mechanism and another based on a parameterized SOA model used in conjunction with an underlying gas-phase mechanism, both of which simulate SOA formation through partitioning to two stable liquid phases: one hydrophilic containing particle aqueous-phase and the other hydrophobic comprising mainly organic components. The models were evaluated against outdoor smog chamber experiments with different combinations of initial toluene, o-xylene, p-xylene, toluene and xylene mixtures, NOx, non-SOA-forming hydrocarbon mixture, initial seed type, and humidity. Aerosol data for experiments with either ammonium sulfate or initial background seed particles, in the presence of an atmospheric hydrocarbon mixture, NOx and in sunlight under a dry atmosphere (RH = 6 to 10%) show reduced SOA formation when compared to experiments with similar initial gas and particle concentrations at higher relative humidities (RH = 40 to 90%). Both frameworks simulated reasonable fits to the total observed SOA concentrations under all conditions. For both dry and wet experiments with low initial seed, semi-volatile product partitioning in particle organic-phase is mass-transfer limited and is modeled using a dynamic gas-particle partitioning algorithm with accommodation coefficient as the primary pseudo-transport parameter. Further, the modeled SOA product distributions for both frameworks clearly show the importance of the contribution of aqueous-phase SOA particularly under conditions of low initial seed concentrations and high-humidity. For both models, under these conditions, aqueous-phase SOA from uptake of glyoxal, methylglyoxal and related polar products to particle water phase dominates as compared to the partitioning of semi-volatiles to particle organic phase. Interestingly, both the kinetic and parameterized SOA frameworks simulate similar amounts of aqueous-phase SOA for each experiment. For wet experiments with initial ammonium sulfate seed, the modeled fraction of aqueous-phase SOA is up to 82% of the total ammonium sulfate mass and for wet experiment with initial background seed this fraction is as high as 60% of the total particle mass formed for the duration of the experiments. This suggests that aqueous-phase SOA from oxidation of toluene and xylene, under atmospherically relevant conditions, is significant and should be part of kinetic or parameterized SOA modeling frameworks in current air quality models.

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

2010-12-01

301

Characterization of low-temperature vapour pressure estimates for secondary organic aerosol applications  

NASA Astrophysics Data System (ADS)

Many models of secondary organic aerosol (SOA) formation, adhering to gas-particle equilibrium partitioning theory, require known vapour pressures for low volatility products of volatile organic compound (VOC) oxidation. Since the majority of such products have yet to be isolated and analysed, few experimental determinations of pertinent vapour pressures have been achieved, and models are forced to rely on vapour pressure estimates, such as those available through the common, computer-based SPARC and MPBPWIN property calculators. Thus, the accuracy of the respective estimation methods must be measured and evaluated, in order to determine the consequences in the resulting models. However, published evaluations, and most models themselves, typically focus on moderate to high ambient temperatures, which may not be applicable year-round in colder regions, where the rate of VOC oxidation slows, while the vapour pressures of the products decrease, indicating an increased tendency to condense into the aerosol phase. In this paper, the accuracy of the SPARC and MPBPWIN methods is evaluated over a broad temperature range, from 248.15 to 298.15 K, in five degree intervals using a test set of 45 compounds. The results are reported in terms of mean average error (MAE) and mean bias error (MBE), and given for alcohol, carboxylic acid, aldehyde, and ketone compound classes at each temperature. Specific trends in MAE and MBE with regard to compound class and changing temperature are discussed. More generally, the evaluation indicates that SPARC, with MAE decreasing from 0.288 at 248.15 K to 0.165 at 298.15 K and MBE increasing from -0.180 at 248.15 K to a peak of -0.081 at 293.15 K, is more accurate at low to moderate temperatures than MPBPWIN, with MAE decreasing from 0.436 at 248.15 K to 0.272 at 298.15 K and MBE increasing from -0.328 at 248.15 K to -0.213 at 298.15 K. Decreasing accuracy at lower temperatures emphasizes a need for focused experimental and model efforts in this temperature range.

Schnitzler, Elijah G.; McDonald, Karen M.

2012-09-01

302

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

NASA Astrophysics Data System (ADS)

Environmental chamber ("smog chamber") experiments were conducted to investigate secondary organic aerosol (SOA) production from dilute emissions from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel vehicles (HDDVs) under urban-like conditions. Some of the vehicles were equipped with emission control aftertreatment devices, including diesel particulate filters (DPFs), selective catalytic reduction (SCR) and diesel oxidation catalysts (DOCs). Experiments were also performed with different fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur diesel) and driving cycles (Unified Cycle,~Urban Dynamometer Driving Schedule, and creep + idle). During normal operation, vehicles with a catalyzed DPF emitted very little primary particulate matter (PM). Furthermore, photooxidation of dilute emissions from these vehicles produced essentially no SOA (below detection limit). However, significant primary PM emissions and SOA production were measured during active DPF regeneration experiments. Nevertheless, under reasonable assumptions about DPF regeneration frequency, the contribution of regeneration emissions to the total vehicle emissions is negligible, reducing PM trapping efficiency by less than 2%. Therefore, catalyzed DPFs appear to be very effective in reducing both primary PM emissions and SOA production from diesel vehicles. For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the smog chamber - with the emissions from some vehicles generating twice as much SOA as primary organic aerosol after 3 h of oxidation at typical urban VOC / NOx ratios (3 : 1). Comprehensive organic gas speciation was performed on these emissions, but less than half of the measured SOA could be explained by traditional (speciated) SOA precursors. The remainder presumably originates from the large fraction (~30%) of the nonmethane organic gas emissions that could not be speciated using traditional one-dimensional gas chromatography. The unspeciated organics - likely comprising less volatile species such as intermediate volatility organic compounds - appear to be important SOA precursors; we estimate that the effective SOA yield (defined as the ratio of SOA mass to reacted precursor mass) was 9 ± 6% if both speciated SOA precursors and unspeciated organics are included in the analysis. SOA production from creep + idle operation was 3-4 times larger than SOA production from the same vehicle operated over the Urban Dynamometer Driving Schedule (UDDS). Fuel properties had little or no effect on primary PM emissions or SOA formation.

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

2014-05-01

303

Gas-phase products and secondary organic aerosol formation from the ozonolysis and photooxidation of myrcene  

NASA Astrophysics Data System (ADS)

In this study, the ozone and OH-radical reactions of myrcene were investigated in an aerosol chamber (at 292-295 K and 50% relative humidity) to examine the gas-phase oxidation products and secondary organic aerosol (SOA) formation. The ozone reaction studies were performed in the presence and absence of CO, which serves as an OH radical scavenger. In the photooxidation experiments OH radicals were generated by photolysis of methyl nitrite. The ozonolysis of myrcene in the presence of CO resulted in a substantial yield of 4-vinyl-4-pentenal (55.3%), measured as m/z 111 plus m/z 93 using proton transfer reaction-mass spectrometry (PTR-MS) and confirmed unambiguously as C7H10O by denuder measurements and HPLC/ESI-TOFMS analysis of its 2,4-dinitrophenylhydrazine (DNPH) derivative. Additionally, the formation of two different organic dicarbonyls with m/z 113 and a molecular formula of C6H8O2 were observed (2.1%). The yields of these dicarbonyls were higher in the ozonolysis experiments without an OH scavenger (5.4%) and even higher (13.8%) in the myrcene OH radical reaction. The formation of hydroxyacetone as a direct product of the myrcene reaction with ozone with a molar yield of 17.6% was also observed. The particle size distribution and volume concentrations were monitored and facilitated the calculation of SOA yields, which ranged from 0 to 0.01 (ozonolysis in the presence of CO) to 0.39 (myrcene OH radical reaction). Terpenylic acid was found in the SOA samples collected from the ozonolysis of myrcene in the absence of an OH scavenger and the OH radical-initiated reaction of myrcene but not in samples collected from the ozonolysis in the presence of CO as an OH radical scavenger, suggesting that terpenylic acid formation involves the reaction of myrcene with an OH radical. A reaction mechanism describing the formation of terpenylic acid is proposed.

Böge, Olaf; Mutzel, Anke; Iinuma, Yoshiteru; Yli-Pirilä, Pasi; Kahnt, Ariane; Joutsensaari, Jorma; Herrmann, Hartmut

2013-11-01

304

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

NASA Astrophysics Data System (ADS)

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), organonitrates (RONO2) and/or organosulfates (ROSO3H).

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

2013-08-01

305

Molecular Formula Characterization of Biogenic Secondary Organic Aerosol: Descriptive Statistical Evaluation  

NASA Astrophysics Data System (ADS)

The detailed molecular composition of approximately 20 laboratory generated terpene ozonolysis secondary organic aerosol (SOA) samples was studied using ultrahigh resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Individual experiments were conducted with one of four terpene SOA precursors (?-pinene, ?-pinene, limonene or ?-caryophyllene), varied relative humidity (RH) conditions (0%, 4%, or 30%) and the presence or absence of cyclohexane (serving as a radical scavenger). In this work, we focus on the molecular composition of the SOA experiments conducted at 4% and 30% RH without cyclohexane. In each of the experimental SOA samples, the oxygen number and the DBE values increase with increasing carbon number and three or four distinct groups (aka oligomer groups) were observed in the mass spectra. The overall bulk properties, such as the elemental ratios and the average number of double bond equivalents (DBE), of the SOA were highly similar. Despite the high number of identified species (N ? 1000) in each SOA sample, compounds unique to the SOA formed at either 4% or 30% RH conditions were comparatively low (< 200). An exception to this was observed for the D-limonene ozonolysis SOA formed at 4% RH conditions where over 450 unique molecular formulas were observed. Due to the similarity in the bulk properties and composition of the SOA from the experiments, multivariate statistics were used to distinguish the experiments from each other. Hierarchical cluster analysis and principal component analysis was performed using the molecular formulas and their relative abundances for all of the identified species. Slight compositional differences between the experiments showed that experiments with the same terpene SOA precursor were most closely related regardless of the RH or the presence/absence of cyclohexane. Furthermore, SOA experiments with D-limonene and ?-caryophyllene as precursors were clearly distinguished from ?-pinene and ?-pinene. When the experimental SOA composition was compared with ambient samples, we observed a high number of common monoisotopic molecular formulas for summer aerosol [63%; Mazzoleni et. al., Env. Chem. 2012] and winter cloudwater samples [60%; Zhao et. al., ACPD 2013]. However the molecular formulas identified as significant using principal components analysis, were not found consistently in both samples indicating variable SOA contributions to summer and winter ambient samples. Mazzoleni, L.R., P. Saranjampour, M.M. Dalbec, V. Samburova, B. Zielinska, A.G. Hallar, D. Lowenthal, and S. Kohl, Identification of Water-Soluble Organic Carbon in Nonurban Organic Aerosols using Ultrahigh-Resolution FT-ICR Mass Spectrometry: Organic Anions, Environmental Chemistry, Vol. 9(3) 285-297, 2012. Zhao, Y., A.G. Hallar, and L.R. Mazzoleni, Atmospheric Organic Matter in Clouds: Exact Masses and Molecular Formula Identification using Ultrahigh Resolution FT-ICR Mass Spectrometry, Atmospheric Chemistry and Physics Discussion, In Press, 2013.

Dalbec, M.; Zhao, Y.; Fisseha, R.; Putman, A.; Kundu, S.; Rahn, T. A.; Mazzoleni, L. R.

2013-12-01

306

Understanding the anthropogenic influence on formation of biogenic secondary organic aerosols via analysis of organosulfates and related oxidation products  

NASA Astrophysics Data System (ADS)

Anthropogenic emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) may affect concentration levels and composition of biogenic secondary organic aerosols (BSOA) through photochemical reactions with biogenic organic precursors to form organosulfates and nitrooxy organosulfates. We investigated this influence in a field study from 19 May-22 June 2011 at two sampling sites in Denmark. Within the study, we identified a substantial number of organic acids, organosulfates and nitrooxy organosulfates in the ambient urban curbside and semi-rural background air. A high degree of correlation in concentrations was found among a group of specific organic acids, organosulfates and nitrooxy organosulfates, which may originate from various precursors, suggesting a common mechanism or factor affecting their concentration levels at the sites. It was proposed that the formation of those species most likely occurred on a larger spatial scale with the compounds being long-range transported to the sites on the days with highest concentrations. The origin of the long-range transported aerosols was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model in addition to modeled emissions of related precursors including isoprene and monoterpenes using the global Model of Emissions of Gases and Aerosols from Nature (MEGAN) and SO2 emissions using the European Monitoring and Evaluation Program (EMEP) database. The local impacts were also studied by examining the correlation between selected species which showed significantly enhanced concentrations at the urban curbside site and the local concentrations of various gases including SO2, ozone (O3), carbon monoxide (CO), NOx, aerosol acidity and other meteorological conditions. This investigation showed that an inter-play of the local parameters such as the aerosol acidity, NOx, relative humidity (RH), temperature and global radiation seemed to influence the concentration level of those species, via such as wet aerosol chemistry. The local impacts however seemed minor on the concentration levels of the studied compounds. The total concentrations of organosulfates and nitrooxy organosulfates contributed to approximately 0.7% of PM1 mass.

Nguyen, Q. T.; Christensen, M. K.; Cozzi, F.; Zare, A.; Hansen, A. M. K.; Kristensen, K.; Tulinius, T. E.; Madsen, H. H.; Christensen, J. H.; Brandt, J.; Massling, A.; Nøjgaard, J. K.; Glasius, M.

2014-01-01

307

Physico­chemical Properties of Secondary Organic Aerosol (soa) Particles Generated Under Laboratory Photooxidation Conditions  

NASA Astrophysics Data System (ADS)

The goal of this experiment is to investigate the chemical reactivity of secondary or- ganic aerosol particles (SOA) in the presence of NOx. of special interest is the ques- tion whether or not SOA enables the reduction of NO2 to HONO, an important photochemical OH precursor. We report the controlled production of SOA particles using 5ppm of toluene (C7H8) or limonene (C10H16) in the presence of O3 or NO2 at 60% r.h. at 1 atmosphere of air using a (filtered) 150W high­pressure Xe arc lamp as a photon source. The particle production is taking place in an atmospheric pressure flow cell whose gas phase residence time was chosen to lie in the range of one to several seconds. The gas phase is monitored using a differentially pumped quadrupole mass spectrometer whereas the condensed phase has been characterized both by its total particle count using a Condensation Nucleation Counter (CNC) or a downstream Differential Mobility Analyzer (DMA) coupled to an additional CNC. Particle counts of several 105 particles cm-3 were routinely achieved. Both O3 and NO2 are removed immediately after the flow reactor using a diffusion denuder coated with either KI or NDA. The flow has been directed across a glass fiber filter during one to two hours at constant throughput. Subsequently the SOA particles supported on the glass fiber fil- ter, typically a few mg, have been investigated in a low-pressure Knudsen flow reactor using NO2 and H2O.

Demirdjian, B.; Rossi, M. J.

308

Direct Aqueous Photochemistry of Isoprene High-NOx Secondary Organic Aerosol  

SciTech Connect

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.

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

2012-05-17

309

Chemical Characterization of Secondary Organic Aerosol Formed Through Cloud Processing of Methylglyoxal  

NASA Astrophysics Data System (ADS)

There is increasing evidence suggesting that secondary organic aerosol (SOA) forms as a result of low volatility product formation in atmospheric aqueous phase reactions. In this work aqueous phase photooxidation experiments between methylglyoxal (an isoprene oxidation product) and hydroxyl radical were conducted to simulate the cloud processing of methylglyoxal. The results verify that, as predicted, oxalic acid forms through cloud processing of methylglyoxal. This work adds to the growing body of literature (Altieri et al., 2006; Carlton et al., 2006; Carlton et al., 2007; Crahan et al., 2004; Warneck, 2003; 2005; Yu et al., 2005) supporting the hypothesis that cloud processing is a substantial source of oxalic acid to the atmosphere. Oxalic acid is the most abundant dicarboxylic acid in the atmosphere and a contributor to SOA. The formation of additional monomer products (e.g., malic acid, succinic acid, glycolic acid) and the development of an oligomer system were also identified through use of a combination of electrospray ionization mass spectrometry (ESI-MS) techniques: a quadrupole ESI-MS, an ion trap ESI-MS-MS, and an ultra-high resolution ESI FT-ICR MS. We propose a mechanism of oligomer formation through esterification of monomers with a hydroxy acid formed from hydroxyl radical initiated reactions. Oligomers were only recently identified as cloud processing products (Altieri et al., 2006), and this work is the first chemical characterization of oligomers formed through cloud processing reactions. The chemical characterization includes the distribution of molecular weights, elemental compositions, structure, and organic mass to organic carbon (OM:OC) ratio. Methylglyoxal is a water- soluble product of both biogenic and anthropogenic hydrocarbon oxidation. The varied and multiple sources of methylglyoxal suggest there is strong potential for these low volatility products (e.g., oxalic acid and oligomers) to significantly contribute to SOA.

Altieri, K. E.; Seitzinger, S. P.; Carlton, A. G.; Turpin, B. J.; Klein, G. C.; Marshall, A. G.

2007-12-01

310

Quantifying the ionic reaction channels in the Secondary Organic Aerosol formation from glyoxal  

NASA Astrophysics Data System (ADS)

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.

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

311

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

NASA Astrophysics Data System (ADS)

The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter after three hours of oxidation inside the chamber at typical atmospheric oxidant levels. Therefore, the contribution of light duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3-7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photo-oxidizing exhaust from newer (LEV1 and LEV2) vehicles was only modestly lower (38%) than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions in non-methane organic gas emissions. These data suggest that a complex and non-linear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the time scale of these experiments, the mixture of organic vapors emitted by newer vehicles appear to be more efficient (higher yielding) in producing SOA than the emissions from older vehicles. About 30% of the non-methane organic gas emissions from the newer (LEV1 and LEV2) vehicles could not be speciated, and the majority of the SOA formed from these vehicles appears to be associated with these unspeciated organics. These results for light-duty gasoline vehicles contrast with the results from a companion study of on-road heavy-duty diesel trucks; in that study late model (2007 and later) diesel trucks equipped with catalyzed diesel particulate filters emitted very little primary PM, and the photo-oxidized emissions produced negligible amounts of SOA.

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

2013-09-01

312

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

NASA Astrophysics Data System (ADS)

The effects of photochemical aging on emissions from 15 light-duty gasoline vehicles were investigated using a smog chamber to probe the critical link between the tailpipe and ambient atmosphere. The vehicles were recruited from the California in-use fleet; they represent a wide range of model years (1987 to 2011), vehicle types and emission control technologies. Each vehicle was tested on a chassis dynamometer using the unified cycle. Dilute emissions were sampled into a portable smog chamber and then photochemically aged under urban-like conditions. For every vehicle, substantial secondary organic aerosol (SOA) formation occurred during cold-start tests, with the emissions from some vehicles generating as much as 6 times the amount of SOA as primary particulate matter (PM) after 3 h of oxidation inside the chamber at typical atmospheric oxidant levels (and 5 times the amount of SOA as primary PM after 5 × 106 molecules cm-3 h of OH exposure). Therefore, the contribution of light-duty gasoline vehicle exhaust to ambient PM levels is likely dominated by secondary PM production (SOA and nitrate). Emissions from hot-start tests formed about a factor of 3-7 less SOA than cold-start tests. Therefore, catalyst warm-up appears to be an important factor in controlling SOA precursor emissions. The mass of SOA generated by photooxidizing exhaust from newer (LEV2) vehicles was a factor of 3 lower than that formed from exhaust emitted by older (pre-LEV) vehicles, despite much larger reductions (a factor of 11-15) in nonmethane organic gas emissions. These data suggest that a complex and nonlinear relationship exists between organic gas emissions and SOA formation, which is not surprising since SOA precursors are only one component of the exhaust. Except for the oldest (pre-LEV) vehicles, the SOA production could not be fully explained by the measured oxidation of speciated (traditional) SOA precursors. Over the timescale of these experiments, the mixture of organic vapors emitted by newer vehicles appears to be more efficient (higher yielding) in producing SOA than the emissions from older vehicles. About 30% of the nonmethane organic gas emissions from the newer (LEV1 and LEV2) vehicles could not be speciated, and the majority of the SOA formed from these vehicles appears to be associated with these unspeciated organics. By comparing this study with a companion study of diesel trucks, we conclude that both primary PM emissions and SOA production for light-duty gasoline vehicles are much greater than for late-model (2007 and later) on-road heavy-duty diesel trucks.

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

2014-05-01

313

The influence of temperature and aerosol acidity on biogenic secondary organic aerosol tracers: Observations at a rural site in the central Pearl River Delta region, South China  

NASA Astrophysics Data System (ADS)

At a rural site in the central Pearl River Delta (PRD) region in south China, fine particle (PM 2.5) samples were collected during fall-winter 2007 to measure biogenic secondary organic aerosol (SOA) tracers, including isoprene SOA tracers (3-methyl-2,3,4-trihydroxy-1-butene, 2-methylglyceric acid, 2-methylthreitol and 2-methylerythritol), ?-pinene SOA tracers ( cis-pinonic acid, pinic acid, 3-methyl-1,2,3-butanetricarboxylic acid, 3-hydroxyglutaric acid and 3-hydroxy-4,4-dimethylglutaric acid) and a sesquiterpene SOA tracer (?-caryophyllinic acid). The isoprene-, ?-pinene- and sesquiterpene-SOA tracers averaged 30.8 ± 15.9, 6.61 ± 4.39, and 0.54 ± 0.56 ng m -3, respectively; and 2-methyltetrols (sum of 2-methylthreitol and 2-methylerythritol, 27.6 ± 15.1 ng m -3) and cis-pinonic acid (3.60 ± 3.76 ng m -3) were the dominant isoprene- and ?-pinene-SOA tracers, respectively. 2-Methyltetrols exhibited significantly positive correlations ( p < 0.05) with ambient temperature, probably resulting from the enhanced isoprene emission strength and tracer formation rate under higher temperature. The significantly positive correlation ( p < 0.05) between 2-methyltetrols and the estimated aerosol acidity with a slope of 59.4 ± 13.4 ng m -3 per ?mol [H +] m -3 reflected the enhancement of isoprene SOA formation by aerosol acidity, and acid-catalyzed heterogeneous reaction was probably the major formation pathway for 2-methyltetrols in the PRD region. 2-Methylglyceric acid showed poor correlations with both temperature and aerosol acidity. The ?-pinene SOA tracers showed poor correlations with temperature, probably due to the counteraction between temperature effects on the precursor emission/tracer formation and gas/particle partitioning. Among the ?-pinene SOA tracers, only cis-pinonic acid and pinic acid exhibited significant correlations with aerosol acidity with slopes of -11.7 ± 3.7 and -2.2 ± 0.8 ng m -3 per ?mol [H +] m -3, respectively. The negative correlations observed for ?-pinene SOA tracers might result from their transfer from particle to gas phase with the increase of aerosol acidity. The ratio of cis-pinonic acid plus pinic acid to 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) ranged from 0.28 to 28.9 with a mean of 7.19, indicating the relatively fresh ?-pinene SOA tracers during our campaign.

Ding, Xiang; Wang, Xin-Ming; Zheng, Mei

2011-02-01

314

MODELING THE FORMATION OF SECONDARY ORGANIC AEROSOL WITHIN A COMPREHENSIVE AIR QUALITY MODEL SYSTEM  

EPA Science Inventory

The aerosol component of the CMAQ model is designed to be an efficient and economical depiction of aerosol dynamics in the atmosphere. The approach taken represents the particle size distribution as the superposition of three lognormal subdistributions, called modes. The proces...

315

Atmospheric oxalic acid and related secondary organic aerosols in Qinghai Lake, a continental background site in Tibet Plateau  

NASA Astrophysics Data System (ADS)

Summertime PM2.5 aerosols collected from Qinghai Lake (3200 m a.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2-C11), ketocarboxylic acids and ?-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231 ± 119 ng m-3), ketocarboxylic acids (8.4 ± 4.3 ng m-3), and ?-dicarbonyls (2.7 ± 2.1 ng m-3) at the Tibetan background site are 2-5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30-400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and ?-dicarbonyls at this background site.

Meng, Jingjing; Wang, Gehui; Li, Jianjun; Cheng, Chunlei; Cao, Junji

2013-11-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

317

CCN spectra, hygroscopicity, and droplet activation kinetics of secondary organic aerosol resulting from the 2010 Deepwater Horizon oil spill.  

PubMed

Secondary organic aerosol (SOA) resulting from the oxidation of organic species emitted by the Deepwater Horizon oil spill were sampled during two survey flights conducted by a National Oceanic and Atmospheric Administration WP-3D aircraft in June 2010. A new technique for fast measurements of cloud condensation nuclei (CCN) supersaturation spectra called Scanning Flow CCN Analysis was deployed for the first time on an airborne platform. Retrieved CCN spectra show that most particles act as CCN above (0.3 ± 0.05)% supersaturation, which increased to (0.4 ± 0.1)% supersaturation for the most organic-rich aerosol sampled. The aerosol hygroscopicity parameter, ?, was inferred from both measurements of CCN activity and from humidified-particle light extinction, and varied from 0.05 to 0.10 within the emissions plumes. However, ? values were lower than expected from chemical composition measurements, indicating a degree of external mixing or size-dependent chemistry, which was reconciled assuming bimodal, size-dependent composition. The CCN droplet effective water uptake coefficient, ?(cond), was inferred from the data using a comprehensive instrument model, and no significant delay in droplet activation kinetics from the presence of organics was observed, despite a large fraction of hydrocarbon-like SOA present in the aerosol. PMID:22356579

Moore, Richard H; Raatikainen, Tomi; Langridge, Justin M; Bahreini, Roya; Brock, Charles A; Holloway, John S; Lack, Daniel A; Middlebrook, Ann M; Perring, Anne E; Schwarz, Joshua P; Spackman, J Ryan; Nenes, Athanasios

2012-03-20

318

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

NASA Astrophysics Data System (ADS)

Filter samples of secondary organic aerosols (SOA) generated from the ozone (O3)- and hydroxyl radical (OH)-initiated oxidation of various biogenic (isoprene, ?-pinene, limonene, ?-cedrene, ?-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.

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

2012-12-01

319

Effects of alkylate fuel on exhaust emissions and secondary aerosol formation of a 2-stroke and a 4-stroke scooter  

NASA Astrophysics Data System (ADS)

Regulated and unregulated emissions from a 2-stroke and a 4-stroke scooter were characterized during a legislative driving cycle in a certified laboratory. Scooter exhaust was analyzed at the tailpipe, in a dilution tunnel, and partly collected in a mobile smog chamber for photochemical ageing. We present evidence that the photochemically aged exhaust from a 2-stroke and a 4-stroke scooter produces considerable amounts of secondary organic aerosol: from 1.5 to 22.0 mg/km, and from 5.5 to 6.6 mg/km, respectively. Tests were repeated after replacing the standard petrol and synthetic lube oil with an alkylate fuel (with low content of aromatic compounds) and ultra-clean lube oil (low ash forming potential). We observed emission reduction (with some exceptions) for several gaseous and particulate phase species, in particular for carbon monoxide (from 8% up to 38% and from 31% to 50%, for the 2-stroke and the 4-stroke scooters, respectively), particulate mass (from 32% up to 75% for the 2-stroke scooter), aromatic compounds (89% and 97% for the 2-stroke and the 4-stroke scooter, respectively), and secondary organic aerosol (from 87% to 100% and 99% for the 2-stroke and the 4-stroke scooters, respectively). We attribute the organic aerosol reduction to the low content of aromatics in the alkylate fuel.

Zardini, Alessandro A.; Platt, Stephen M.; Clairotte, Michael; El Haddad, Imad; Temime-Roussel, Brice; Marchand, Nicolas; Ježek, Irena; Drinovec, Luka; Mo?nik, Griša; Slowik, Jay G.; Manfredi, Urbano; Prévôt, André S. H.; Baltensperger, Urs; Astorga, Covadonga

2014-09-01

320

Secondary organic aerosol formation during June 2010 in Central Europe: measurements and modelling studies with a mixed thermodynamic-kinetic approach  

NASA Astrophysics Data System (ADS)

Until recently secondary organic carbon (SOC) aerosol mass concentrations have been systematically underestimated by three-dimensional atmospheric-chemistry-aerosol models. With a newly proposed concept of aging of organic vapours more realistic model results for organic carbon aerosol mass concentrations could be achieved. Applying a mixed thermodynamic-kinetic approach for SOC aerosol formation shifted the aerosol size distribution towards particles in the cloud condensation nuclei size range, thereby emphasising the importance of SOC aerosol formation schemes for modelling realistic cloud and precipitation formation. The additional importance of hetero-molecular nucleation between H2SO4 and organic vapours remains to be evaluated in three-dimensional atmospheric-chemistry-aerosol models. Here a case study is presented focusing on Puy-de-Dôme, France in June 2010. Even though nucleation events at Puy-de-Dôme were rare during the chosen period of investigation a weak event in the boundary layer could be reproduced by the model when nucleation of low-volatile secondary organic vapour is included. Differences in the model results with and without nucleation of organic vapour are visible in the lower free troposphere over several days of the period. Taking into account nucleation of organic vapour leads to an increase in accumulation mode particles due to coagulation of nucleation and aitken mode particles. Moreover, the measurements indicate a considerable increase in SOC aerosol mass concentration during the measurement campaign, which could be reproduced by modelling using a simplified thermodynamic-kinetic approach for SOC aerosol formation and increased biogenic VOC precursor emissions. Comparison with a thermodynamic SOC aerosol formation approach shows a huge improvement in modelled SOC aerosol mass concentration with the thermodynamic-kinetic approach for SOC aerosol formation and a slight improvement of modelled particle size distribution.

Langmann, B.; Sellegri, K.; Freney, E.

2013-10-01

321

Remote Sensing of Glyoxal as a New Atmospheric Tracer for VOC Chemistry and Secondary Organic Aerosol Formation in the Mexico City Metropolitan Area  

Microsoft Academic Search

Air pollution in the Mexico City Metropolitan Area (MCMA) is intimately linked with the photochemical transformation of primary pollutants like VOC (volatile organic compounds) and NOx, which gives rise to the formation of secondary pollutants such as ozone and secondary organic aerosol (SOA) and their associated adverse effects on human health. As part of the field campaign held in the

R. Volkamer; L. T. Molina; M. J. Molina; T. Shirley; R. Lesher; W. Brune; K. Dzepina; J. Jimenez

2004-01-01

322

Real refractive indices of ?- and ?-pinene and toluene secondary organic aerosols generated from ozonolysis and photo-oxidation  

NASA Astrophysics Data System (ADS)

The refractive index is the fundamental property controlling aerosol optical properties. Secondary organic aerosol (SOA) real refractive indices (mr) were derived from polar nephelometer measurements using parallel and perpendicular polarized 670 nm light, using a genetic algorithm method with Mie-Lorenz scattering theory and measured particle size distributions. The absolute error associated with the mr retrieval is ±0.03, and the instrument has sufficient sensitivity to achieve reliable retrievals for particles larger than about 200 nm. SOA generated by oxidizing ?-pinene, ?-pinene, and toluene with ozone and NOx/sunlight are explored. Retrieved refractive indices for the SOA vary between 1.38 and 1.61, depending on several factors. For ?- and ?-pinene ozonolysis, SOA mr ranges from 1.4 to 1.5 and, within the resolution of our method and bounds of our experiments, is not affected by the addition of an OH scavenger, and is only slightly dependent on the aerosol mass concentration. For photochemically generated SOA, mr generally increases as experiments progress, ranging from about 1.4 to 1.53 for ?-pinene, 1.38 to 1.53 for ?-pinene, and 1.4 to 1.6 for toluene. The pinene SOA mr appear to decrease somewhat toward the end of the experiments. Aspects of the data suggest aerosol mass concentration, oxidation chemistry, temperature, and aerosol aging may all influence the refractive index. There is more work to be done before recommendations can be made for atmospheric applications, but our calculations of the resulting asymmetry parameter indicate that a single value for SOA refractive index will not be sufficient to accurately model radiative transfer.

Kim, Hwajin; Barkey, Brian; Paulson, Suzanne E.

2010-12-01

323

Diurnally resolved particulate and VOC measurements at a rural site: indication of significant biogenic secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

We report simultaneous measurements of volatile organic compound (VOC) mixing ratios including C6 to C8 aromatics, isoprene, monoterpenes, acetone and organic aerosol mass loadings at a rural location in southwestern Ontario, Canada by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and Aerosol Mass Spectrometry (AMS), respectively. During the three-week-long Border Air Quality and Meteorology Study in June-July 2007, air was sampled from a range of sources, including aged air from the polluted US Midwest, direct outflow from Detroit 50 km away, and clean air with higher biogenic input. After normalization to the diurnal profile of CO, a long-lived tracer, diurnal analyses show clear photochemical loss of reactive aromatics and production of oxygenated VOCs and secondary organic aerosol (SOA) during the daytime. Biogenic VOC mixing ratios increase during the daytime in accord with their light- and temperature-dependent sources. Long-lived species, such as hydrocarbon-like organic aerosol and benzene show little to no photochemical reactivity on this timescale. From the normalized diurnal profiles of VOCs, an estimate of OH concentrations during the daytime, measured O3 concentrations, and laboratory SOA yields, we calculate integrated local organic aerosol production amounts associated with each measured SOA precursor. Under the assumption that biogenic precursors are uniformly distributed across the southwestern Ontario location, we conclude that such precursors contribute significantly to the total amount of SOA formation, even during the period of Detroit outflow. The importance of aromatic precursors is more difficult to assess given that their sources are likely to be localized and thus of variable impact at the sampling location.

Sjostedt, S. J.; Slowik, J. G.; Brook, J. R.; Chang, R. Y.-W.; Mihele, C.; Stroud, C. A.; Vlasenko, A.; Abbatt, J. P. D.

2011-06-01

324

Gas/particle partitioning of primary and secondary organic aerosol products in a boreal forest  

NASA Astrophysics Data System (ADS)

The volatile and semi-volatile of the polar and acidic fractions in both particulate and gas phase of biogenic secondary aerosol over a boreal forest (Hyytälä, Finland) were analyzed. A series of monoterpene-skeleton photo-oxidation carbonyl and acidic compounds were detected and quantified conjointly with high molecular weight n-alkan-1-ols, n-alkanoic, n-alkenoic and ?,?-dicarboxylic acids in both gas and particles over the Hyytälä forest. In particular, nopinone and pinonaldehyde, nor-pinonic acid pinonic acidand pinic acids were identified on the basis of their CI and EI mass spectra and comparison with authentic standards. These compounds have been determined as characteristic products of the photo-oxidation of ?- and ?-pinene with ozone, OH and NO_3 radicals, in laboratory studies. Furthermore, n-alkan-1-ols, n-alkanoic acids, n-alkenoic acids and ?,?-dicarboxylic acids were identified and determined in both gas and particles of studied areas. The n-alkanols and n-alkanoic and alkenoic acids are known as constituents of epicuticular leaf wax of terrestrial plantsand their presence has been confirmed in the leaf extract of the studied forest trees. For pinonic, nor pinonic and pinic acids, particle concentrations were higher than the corresponding concentrations in the gas phase. The concentration of the acids was mostly higher, when photo-oxidation reactions of monoterpenes prevailed. The decrease of oxidant concentration in the nighttime yielded lower or not detectable gas phase concentration. Pinonaldehyde and nopinone have shown higher gas phase than particle concentrations. Nighttime reactions of pinenes with NO_3 radicals eventually contributed to the relatively elevated concentration of pinonaldehyde. The concentration profile was observed for the semi-volatile polar (alkanols) and acidic (alkanoic and alkenoic acids) organic compounds, associated with primary emissions from plants, has shown that these compounds were predominantly in the particle phase although their concentration w