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1

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

Microsoft Academic Search

The hygroscopic nature of atmospheric aerosol has generally been associated with its inorganic fraction. In this study, a group contribution method is used to predict the water absorption of secondary organic aerosol (SOA). Compared against growth measurements of mixed inorganic-organic particles, this method appears to provide a first-order approximation in predicting SOA water absorption. The growth of common SOA species

Asif S. Ansari; Spyros N. Pandis

2000-01-01

2

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

SciTech Connect

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

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

2000-01-01

3

Factors determining the formation of secondary inorganic aerosol: a case study in the Po Valley (Italy)  

NASA Astrophysics Data System (ADS)

Physicochemical properties of aerosol were investigated by analyzing the inorganic water soluble content in PM2.5 samples collected in the eastern part of the Po Valley (Italy). In this area the EU limits for many air pollutants are frequently exceeded as a consequence of local sources and regional-scale transport of secondary inorganic aerosol precursors. Nine PM2.5-bound major inorganic ions (F-, Cl-, NO3-, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) were monitored over one year in three sites categorized as semi-rural background, urban background and industrial. The acidic properties of the PM2.5 were studied by applying the recently developed E-AIM thermodynamic model 4. The experimental data were also examined in relation to the levels of gaseous precursors of SIA (SO2, NOx, NO, NO2) and on the basis of some environmental conditions having an effect on the secondary aerosols generation processes. A chemometric procedure using cluster analysis on experimental [NH4+]/[SO42-] molar ratio and NO3- concentration has been applied to determine the conditions needed for ammonium nitrate formation in different chemical environments. Finally, some considerations on the secondary inorganic aerosol formation and the most relevant weather conditions concerning the sulfate-nitrate-ammonium system were also discussed. The methods used can be easily applied to other environments to evaluate the physicochemical characteristics of aerosols and the climatic conditions necessary for the formation of ammonium sulfate and ammonium nitrate aerosols.

Squizzato, S.; Masiol, M.; Brunelli, A.; Pistollato, S.; Tarabotti, E.; Rampazzo, G.; Pavoni, B.

2012-07-01

4

Factors determining the formation of secondary inorganic aerosol: a case study in the Po Valley (Italy)  

NASA Astrophysics Data System (ADS)

Physicochemical properties of aerosol were investigated by analyzing the inorganic water soluble content in PM2.5 samples collected in the eastern part of the Po Valley (Italy). In this area the EU limits for many air pollutants are frequently exceeded as a consequence of local sources and regional-scale transport of secondary inorganic aerosol precursors. Nine PM2.5-bound major inorganic ions (F-, Cl-, NO3-, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) were monitored over one year in three sites categorized as semi-rural background, urban background and industrial. The acidic properties of the PM2.5 were studied by applying the recently developed E-AIM thermodynamic model 4 (Extended Aerosol Thermodynamics Model). The experimental data were also examined in relation to the levels of gaseous precursors of secondary inorganic aerosol (SO2, NOx, NO, NO2) and on the basis of some environmental conditions having an effect on the secondary aerosols generation processes. A chemometric procedure using cluster analysis on experimental [NH4+]/[SO42-] molar ratio and NO3- concentration has been applied to determine the conditions needed for ammonium nitrate formation in different chemical environments. Finally, some considerations on the secondary inorganic aerosol formation and the most relevant weather conditions concerning the sulfate-nitrate-ammonium system were also discussed. The obtained results and discussion can help in understanding the secondary aerosol formation dynamics in the Po Valley, which is one of the most critical regions for air pollution in southern Europe.

Squizzato, S.; Masiol, M.; Brunelli, A.; Pistollato, S.; Tarabotti, E.; Rampazzo, G.; Pavoni, B.

2013-02-01

5

Enhancements to the UK Photochemical Trajectory Model for simulation of secondary inorganic aerosol  

NASA Astrophysics Data System (ADS)

Particulate matter remains a challenging pollutant for air pollution control in the UK and across much of Europe. Particulate matter is a complex mixture of which secondary inorganic compounds (sulphates, nitrates) are a major component. This paper is concerned with taking a basic version of the UK Photochemical Trajectory Model and enhancing a number of features in the model in order to better represent boundary layer processes and to improve the description of secondary inorganic aerosol formation. The enhancements include an improved treatment of the boundary layer, deposition processes (both wet and dry), attenuation of photolysis rates by cloud cover, and inclusion of the aerosol thermodynamic model ISORROPIA II to account both for chemistry within the aerosol and between the particles and gas phase. Emissions inventories have been updated and are adjusted according to season, day of the week and hour of the day. Stack emissions from high level sources are now adjusted according to the height of the boundary layer and a scheme for generating marine aerosol has been included. The skill of the improved model has been evaluated through predictions of the concentrations of particulate chloride, nitrate and sulphate and the results show increased accuracy and lower mean bias. There is a much higher proportion of the values lying within a factor of 2 of the observed values compared to the basic model and Normalised Mean Bias has reduced by at least 89% for nitrate and sulphate. Similarly, the Index of Agreement between calculated and measured values has improved by ˜10%. Considering the contribution of each enhancement to the improvement in the performance metrics, the most significant enhancement was the replacement of the parameterisation of the boundary layer height, relative humidity and temperature by HYSPLIT values calculated for each trajectory. The second most significant enhancement was the parameterisation of the photolysis rates by values calculated by an off line database accounting for the dependence of photolysis rates on zenith angle, cloud cover, land surface type and column ozone. The inclusion of initial conditions which were dependent on the starting point of the trajectory and the modulation of stack emissions made the most significant improvement to sulphate. Furthermore, in order to assess the model's response to abatement scenarios, 30% abatements of either NH3, NOx or SO2 showed a reduction in the sum of chloride, nitrate and sulphate of between 3.1% and 8.5% (with a corresponding estimated reduction of 1.6-3.7% reduction in PM10). The largest reduction in this contribution is due to the abatement of NOx.

Beddows, David C. S.; Hayman, Garry D.; Harrison, Roy M.

2012-09-01

6

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

7

Secondary Inorganic Soluble Aerosol in Hong Kong: Continuous Measurements, Formation Mechanism Discussion and Improvement of an Observation-Based Model to Study Control Strategies  

NASA Astrophysics Data System (ADS)

Work in this thesis focuses on half-hourly or hourly measurements of PM2.5 secondary inorganic aerosols (SIA) in two locations in Hong Kong (HK) using a continuous system, PILS (Particle-into-Liquid System) coupled to two ion chromatographs. The high-resolution data sets allow the examination of SIA temporal dynamics in the scale of hours that the filter-based approach is incapable of providing. (1) Impacts of local emissions, regional transports and their interactions on chemical composition and concentrations of PM2.5 SIA and other ionic species were investigated at the Hong Kong University of Science and Technology (HKUST), a receptor site, under three synoptic conditions. (2) Chemical compositions and size characteristics of ionic species were investigated at Tung Chung, a new town area located in the Southwest part of HK. The sampling period was from 17 to 26 December 2009, covering both normal conditions and an aerosol episode. The three major secondary inorganic ions, SO42, NH4+ and NO 3-, accounted for 47 +/- 6% of PM2.5 mass. Further examination of size characteristics of NO3 - shows that fine mode NO3- is more likely to occur in environments when the fine particles are less acidic and the sea-salt aerosol contributions are low. (3) The ionic chemical composition of PM2.5 and meteorological parameters (e.g., temperature, RH) obtained at the HKUST site under all three different synoptic conditions are input into Aerosol Inorganic Model (AIM-III) for estimation of in situ pH through calculation of H+ amount and aerosol liquid water content (LWC). The second part of this thesis work is to improve an observation-based model (OBAMAP) for SIA, which was first developed by Dr. Zibing Yuan (2006) to evaluate the sensitivity of formation of nitrate ad sulfate to changes in the emissions of their precursors (i.e., NOx, SO2, and VOCs). The improvement work includes incorporating updated chemical mechanisms, thermodynamic equilibrium for gas-aerosol phase apportionment and size distribution of SIA. The new OBM for SIA is applied to hourly gaseous and particulate composition data measured during a wintertime pollution episode encountered in Tung Chung for probing effectiveness of different precursor control strategies. The OBM is demonstrated to provide a relatively simple and cost-effective tool for analyzing the increasing database of high time resolution measurements of VOCs and major aerosol ionic species. In this thesis, we propose a new production regime of SO4 2- in which oxidation of S(IV) is dominated by NO 2 and O3 in the aqueous phase. Simulated with a simplified version of OBAMAP, it is shown elevation of NOx favors productions of SO42- in this regime, especially under high-SO 2 conditions. We then study the importance of NO2-derived and O3-derived SO42- during haze episodes in PRD and during winter at urban/suburban locations in PRD. Our findings reveal these two pathways account for >70% of SO42- productions. Since production of NO2-derived SO4 2- is independent on solar actinic fluxes while production by other pathways is, NO2-derived SO42- plays a more important role under low solar actinic fluxes conditions, even during the night time. In addition, it is noted that high levels of NO2-derived SO42- can only be expected under high-SO2 conditions (like in PRD) because level of atmospheric SO2 is the limiting parameter. (Abstract shortened by UMI.)

Xue, Jian

8

The use of trajectory cluster analysis to examine the long-range transport of secondary inorganic aerosol in the UK  

NASA Astrophysics Data System (ADS)

The influence of synoptic-scale atmospheric transport patterns on observed levels of sulphate, nitrate and PM 10 at Belfast (urban) and Harwell (rural) has been examined. Three-day 6-hourly back trajectories for January 2002 to December 2003, arriving at the two sampling locations at 1200 GMT and 900 hPa were calculated. A K-means clustering algorithm is used to group these trajectories into 10 clusters depending on their direction and speed. Non-parametric statistics were used to test for significant differences in mean aerosol concentration across clusters. Significant inter-cluster differences were observed with highest nitrate and sulphate levels associated with south-easterly and easterly trajectory clusters at Belfast and Harwell respectively, and highest chloride concentrations associated with fast moving maritime trajectory categories at both sites. Easterly trajectory clusters show lower sulphate/nitrate ratios compared to other clusters, especially for air travelling from the near continent. Nitrate shows greater episodicity than sulphate with implications for achievement of the daily PM 10 limit value of 50 ?g m -3. Our trajectory analysis suggests that control of NO x emissions from the UK and adjacent continental European countries has a major role to play in achieving compliance with the current PM 10 limit value.

Abdalmogith, Salah S.; Harrison, Roy M.

9

Characterizing the Formation of Secondary Organic Aerosols.  

National Technical Information Service (NTIS)

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 ...

M. Lunden D. Black N. Brown

2004-01-01

10

Characterization of summer organic and inorganic aerosols in Beijing, China with an Aerosol Chemical Speciation Monitor  

NASA Astrophysics Data System (ADS)

An Aerodyne Aerosol Chemical Speciation Monitor (ACSM) was first deployed in Beijing, China for characterization of summer organic and inorganic aerosols. The non-refractory submicron aerosol (NR-PM1) species, i.e., organics, sulfate, nitrate, ammonium, and chloride were measured in situ at a time resolution of ˜15 min from 26 June to 28 August, 2011. The total NR-PM1 measured by the ACSM agrees well with the PM2.5 measured by a Tapered Element Oscillating Microbalance (TEOM). The average total NR-PM1 mass for the entire study is 50 ± 30 ?g m-3 with the organics being the major fraction, accounting for 40% on average. High concentration and mass fraction of nitrate were frequently observed in summer in Beijing, likely due to the high humidity and excess gaseous ammonia that facilitate the transformation of HNO3 to ammonium nitrate particles. Nitrate appears to play an important role in leading to the high particulate matter (PM) pollution since its contribution increases significantly as a function of aerosol mass loadings. Positive matrix factorization (PMF) of ACSM organic aerosol (OA) shows that the oxygenated OA (OOA) - a surrogate of secondary OA dominates OA composition throughout the day, on average accounting for 64%, while the hydrocarbon-like OA (HOA) shows a large increase at meal times due to the local cooking emissions. Our results suggest that high PM pollution in Beijing associated with stagnant conditions and southern air masses is characterized by the high contribution of secondary inorganic species and OOA from regional scale, whereas the aerosol particles during the clean events are mainly contributed by the local emissions with organics and HOA being the dominant contribution.

Sun, Yele; Wang, Zifa; Dong, Huabin; Yang, Ting; Li, Jie; Pan, Xiaole; Chen, Ping; Jayne, John T.

2012-05-01

11

Secondary organic aerosol formation and transport  

NASA Astrophysics Data System (ADS)

A Lagrangian trajectory model simulating the formation, transport and deposition of secondary organic aerosol is developed and applied to the Los Angeles area, for the air pollution episode of 27-28 August 1987. The predicted secondary organic aerosol on 28 August 1987 represents 15-22% of the measured particulate organic carbon at inland locations in the base case simulations, and 5-8% of that at coastal locations. A maximum secondary organic aerosol concentration of 6.8 ?g m -3 is predicted for Claremont, CA, during this episode. On a daily average basis at Claremont about 46% of this secondary organic aerosol is predicted to be a result of the oxidation of non-toluene aromatics (xylenes, alkylbenzenes, etc.), 19% from toluene, 16% from biogenic hydrocarbons (?-pinene, ß-pinene, etc.), 15% from alkanes and 4% from alkenes. The major uncertainties in predicting secondary organic aerosol concentrations are the reactive organic gas emissions, the aerosol yields and the partitioning of the condensable gases between the two phases. Doubling the reactive organic gas (ROG) emissions results in an increase of the secondary organic aerosol predicted at Claremont by a factor of 2.3. Predicted secondary organic aerosol levels are less sensitive to changes in secondary organic aerosol deposition and NO x emissions than to ROG emissions.

Pandis, Spyros N.; Harley, Robert A.; Cass, Glen R.; Seinfeld, John H.

12

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

13

THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS  

EPA Science Inventory

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

14

Common Inorganic Salts Catalyze the Transformations of Organic Compounds in Atmospheric Aerosols  

NASA Astrophysics Data System (ADS)

This presentation reports the discovery that inorganic salts that are ubiquitous in atmospheric aerosols are efficient catalysts for the transformations of organic compounds in these aerosols, by reactions such as aldol condensation or acetal formation.1 For some of these salts, these catalytic properties were not even known in chemistry.2 Kinetic and product studies of these reactions will be presented for carbonyl compounds such as acetaldehyde, acetone, and glyoxal,1,3 and compared with previously known catalysts such as the recently discovered amino acids.4,5 These studies show that these salts make the reactions as fast in typical tropospheric aerosols as in concentrated sulfuric acid. These reactions produce secondary "fulvic" compounds that absorb light in the near UV and visible and would affect the optical properties of aerosols.1,5 They would also account for the depletion of glyoxal recently reported in Mexico city.3 Thus, while acid catalysis is several orders of magnitudes too slow to be significant in tropospheric aerosols, this work identifies new processes that should be ubiquitous in these aerosols and important for atmospheric chemistry. Refs. 1Noziere, B., Dziedzic, P., Cordova, A., Common inorganic ions catalyze chemical reactions of organic compounds in atmospheric aerosols, Submitted, 2008. 2 Noziere, B., Cordova, A., A novel catalyst for aldol condensation reaction, patent pending 02/10/2007. 3Noziere, B., Dziedzic, P., Cordova, A., Products and kinetics of the liquid-phase reaction of glyoxal catalyzed by inorganic ions, Submitted to J. Phys. Chem. A, 2008. 4Noziere, B., and Cordova, A., A Kinetic and Mechanistic Study of the Amino Acid-Catalyzed Aldol Condensation of Acetaldehyde in Aqueous and Salt Solutions, J. Phys. Chem. A, 112, 2827, 2008. 5Noziere, B., Dziedzic, P., and Cordova, A., The Formation of Secondary Light-Absorbing "fulvic-like" Oligomers: A Common Process in Aqueous and Ionic Atmospheric Particles?, Geophys. Res. Lett., 34, L21812, doi:10.1029/ 2007GL031300, 2007.

Noziere, B.; Dziedzic, P.; Cordova, A.

2008-12-01

15

Common inorganic ions are efficient catalysts for organic reactions in atmospheric aerosols and other natural environments  

NASA Astrophysics Data System (ADS)

In this work, inorganic ammonium ions, NH4+, and carbonate ions, CO32-, are reported for the first time as catalysts for organic reactions in atmospheric aerosols and other natural environments at the Earth's surface. These reactions include the formation of C-C and C-O bonds by aldol condensation and acetal formation, and reveal a new aspect of the interactions between organic and inorganic materials in natural environments. The catalytic properties of inorganic ammonium ions, in particular, were not previously known in chemistry. The reactions were found to be as fast in tropospheric ammonium sulfate composition as in concentrated sulfuric acid. The ubiquitous presence and large concentrations of ammonium ions in tropospheric aerosols would make of ammonium catalysis a main consumption pathway for organic compounds in these aerosols, while acid catalysis would have a minor contribution. In particular, ammonium catalysis would account quantitatively for the aging of carbonyl compounds into secondary ''fulvic'' compounds in tropospheric aerosols, a transformation affecting the optical properties of these aerosols. In general, ammonium catalysis is likely to be responsible for many observations previously attributed to acid catalysis in the troposphere.

Nozière, B.; Dziedzic, P.; Córdova, A.

2009-01-01

16

Secondary organic aerosol formation and gas/aerosol partitioning  

NASA Astrophysics Data System (ADS)

An intensive smog chamber study has revealed that secondary organic aerosol (SOA) formation follows Raoult's Law type gas/aerosol absorption thermodynamics. SOA formation was shown to occur via the gas/aerosol partitioning of semi-volatile, oxidation products rather than through the condensation of saturated, non-volatile products. The major consequence of this finding is that SOA yields are not constant, but rather are a function of the organic aerosol mass concentration. The theory has been used to successfully describe the aerosol formation potential of seventeen individual aromatic species, eight biogenic compounds, two different simple hydrocarbon precursor mixtures, and twelve different blends of whole gasoline vapor, in hundreds of smog chamber experiments. These results have been included in a 3-dimensional size- and chemically-resolved atmospheric chemical-transport model and used to simulate SOA formation in the South Coast Air Basin. The inherent dependence of SOA concentrations on primary organic aerosol (POA) concentrations, places strict constraints on organic and elemental carbon aerosol emissions inventories.

Odum, Jay Russell

17

Organosulfate Formation in Biogenic Secondary Organic Aerosol  

EPA Science Inventory

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

18

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

Microsoft Academic Search

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

Y. Kim; K. Sartelet; C. Seigneur

2011-01-01

19

Chamber studies of secondary organic aerosol growth by reactive uptake of simple carbonyl compounds  

Microsoft Academic Search

Recent experimental evidence indicates that heterogeneous chemical reactions play an important role in the gas-particle partitioning of organic compounds, contributing to the formation and growth of secondary organic aerosol in the atmosphere. Here we present laboratory chamber studies of the reactive uptake of simple carbonyl species (formaldehyde, octanal, trans,trans-2,4-hexadienal, glyoxal, methylglyoxal, 2,3-butanedione, 2,4-pentanedione, glutaraldehyde, and hydroxyacetone) onto inorganic aerosol. Gas-phase

Jesse H. Kroll; Nga L. Ng; Shane M. Murphy; Varuntida Varutbangkul; Richard C. Flagan; John H. Seinfeld

2005-01-01

20

Aqueous oxidation of aerosol and cloud water samples at Whistler, BC: Secondary organic aerosol formation via oxidative cloud processing  

NASA Astrophysics Data System (ADS)

Secondary organic aerosols (SOA) modeled to form from traditional gas-phase oxidation mechanism cannot match observed SOA loadings and their degree of oxidation. Aqueous chemistry has been proposed to explain these discrepancies. In particular, cloud processing is important in modifying chemical composition and properties of atmospheric particulate matter. Extremely high water content in cloud droplets favors additional partitioning of water-soluble gaseous organics to cloud water, which is much less significant in aerosol particles. Subsequent aqueous oxidation of those cloud organics followed by droplet evaporation can be a source of SOA. In this study, the water-extractable fraction of filter aerosol samples (PM1) and cloud water collected at Whistler, British Columbia during summer 2010 (Whistler Aerosol and Cloud Study (WACS) 2010) was aerosolized and then analyzed using an Aerodyne Aerosol Mass Spectrometer (AMS) on site. This is the first study to report AMS spectra of cloud water and to make direct comparison between the AMS spectra of cloud water and filter aerosol particles collected at the same location. While sulfate was the most abundant inorganic component in aerosol samples, a comparable amount of inorganic nitrate and sulfate were observed in cloud water, indicating a unique nitrate formation pathway in cloud water. It was found that fresh biogenic organic aerosols (OA) produced at Whistler forest area were generally less oxygenated than aged OA and cloud organics. In addition, a simple aqueous photochemical reaction vessel was used to oxidize both aerosol filter extracts and cloud water samples. Here we have experimental evidence that aqueous oxidation of water-soluble organic aerosol components generate high vapor pressure species that led to significant organic mass loss through volatilization. On the contrary, formation of AMS-measurable organic mass can be observed during aqueous oxidation of cloud organics. This observation suggests that oxidative processing of cloud water can significantly reduce the vapor pressure of volatile/semi-volatile cloud organics and hence is potentially important to produce atmospheric SOA.

Lee, A. K.; Herckes, P.; Liggio, J.; Leaitch, R.; Macdonald, A.; Abbatt, J.

2011-12-01

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

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

Microsoft Academic Search

Abstract. 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

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

2008-01-01

23

The effect of organic coatings on the cloud condensation nuclei activation of inorganic atmospheric aerosol  

Microsoft Academic Search

Atmospheric aerosols have mixed chemical composition, with a variety of inorganic (e.g., sulfate, nitrate, ammonium, and sodium) and organic species often present in a single particle. In the present study, we investigate experimentally the cloud condensation nuclei (CCN) activation of submicron aerosol consisting of an inorganic core (e.g., ammonium sulfate) coated by an organic film, at typical atmospheric supersaturations. We

Celia N. Cruz; Spyros N. Pandis

1998-01-01

24

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

Microsoft Academic Search

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

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

2009-01-01

25

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

2008-08-19

26

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

Microsoft Academic Search

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

Y. Kim; K. Sartelet; C. Seigneur

2010-01-01

27

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....

28

Summary of the CARBOSOL project: Present and retrospective state of organic versus inorganic aerosol over Europe  

NASA Astrophysics Data System (ADS)

Aerosol is an important source of uncertainty concerning the role of the atmosphere in climate forcing. In particular, major gaps exist with respect to its carbonaceous fraction in terms of composition, source apportionment (natural versus anthropogenic), change over the past, and radiative impact. The CARBOSOL project contributes to reduce these uncertainties. CARBOSOL combines a 2-year study of present-day carbonaceous aerosol in air and precipitation in western/central Europe with the trends of climatically relevant species in Alpine ice cores. Comparisons between observed atmospheric distributions (present and proxy of past) and transport/chemistry model simulations allow to test the accuracy of present and past anthropogenic emission inventories and enable for the first time a comparison of the model results for individual components (primary, secondary, fossil fuel, and biogenic) against data derived from measurements. The net radiative effect of the aerosol load and composition (inorganic/organic) in Europe is evaluated using radiative/chemistry/transport models. This summary paper gives an overview of the CARBOSOL goals, and reports on the key findings as a guide to the results detailed in the papers that follow.

Legrand, M.; Puxbaum, H.

2007-12-01

29

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

30

Humidity influence on gas-particle phase partitioning of ?-pinene + O3 secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Water vapor uptake to particles could potentially affect organic-aerosol mass in three ways: first, water in the organic phase could reduce organic (equilibrium) partial pressures according to Raoult's law; second, an aqueous phase could attract water soluble organics according to Henry's law; finally, deliquescence of inorganic particle cores could mix the organic and inorganic particle phases, significantly diluting the organics and again reducing organic partial pressures according to Raoult's law. We present experiments using initially dry ?-pinene + ozone secondary organic aerosol (SOA) on ammonium sulfate (AS) seeds at atmospheric concentrations in a smog chamber. After SOA formation, the chamber relative humidity is increased steadily by addition of steam to near 100%. Little subsequent SOA mass growth is observed, suggesting that none of these potential effects play a strong role in this system.

Prisle, N. L.; Engelhart, G. J.; Bilde, M.; Donahue, N. M.

2010-01-01

31

Investigative Modeling of New Pathways for Secondary Organic Aerosol Formation.  

National Technical Information Service (NTIS)

Recent advances in secondary organic aerosol (SOA) research are reviewed and the status of current understanding is investigated with a model of SOA formation. Benzene and isoprene are newly identified precursors that are included here in the SOA model; t...

B. K. Pun C. Seigneur

2006-01-01

32

Characterization of fine aerosol and its inorganic components at two rural locations in New York State.  

PubMed

Samples of PM(2.5) were collected to measure the concentrations of its chemical constituents at two rural locations, Potsdam and Stockton, NY from November 2002 to August 2005. These samples were collected on multiple filters at both sites, every third day for a 24-h interval with a speciation network sampler. The Teflo filters were analyzed for PM(2.5) mass by gravimetry, and elemental composition by X-ray fluorescence (XRF). Nylasorb filters and Teflo filters were leached with water and analyzed for anions and cations, respectively, by ion chromatography (IC). Fine particulate matter (PM(2.5)) mass and its inorganic component measurements were statistically characterized, and the temporal behavior of these species were assessed. Over the entire study period, PM(2.5) mass concentrations were lower at Potsdam (8.35 microg/m(3)) than at Stockton (10.24 microg/m(3)). At both locations, organic matter (OM) was the highest contributor to mass. Sulfate was the second highest contributor to mass at 27.0% at Potsdam, and 28.7% at Stockton. Nitrate contributions to mass of 8.9 and 9.5% at Potsdam and Stockton, respectively, were the third highest. At both locations, fine PM mass exhibited an annual cycle with a pronounced summer peak and indications of another peak during the winter, consistent with an overall increase in the rate of secondary aerosol formation during the summer, and increased partitioning of ammonium nitrate to the particle phase and condensation of other semi-volatiles during the winter, respectively. An ion-balance analysis indicated that at both locations, during the summers as well as in the winters, the aerosol was acidic. Lognormal frequency distribution fits to the measured mass concentrations on a seasonal basis indicated the overall increase in particle phase secondary aerosol (sulfate and SOA) concentrations during the summers compared to the winters at both locations. PMID:17994281

Sunder Raman, Ramya; Hopke, Philip K; Holsen, Thomas M

2007-11-10

33

Characterization of the inorganic aerosol in Barcelona site during DAURE 2009 field campaigns  

NASA Astrophysics Data System (ADS)

Inorganic compounds account for a significant mass of the ambient aerosol. However this contribution varies with time and aerosol size fraction, depending on the influence of source emissions and ambient conditions, which can be relevant in the formation processes of secondary species. Time series of particulate nitrate, 10 m time resolution, have been obtained during the February-March and July 2009 DAURE (Determination of the sources of atmospheric Aerosols in Urban and Rural Environments in the western Mediterranean) field campaigns in the urban area of Barcelona by means of an R&P8400N monitor. Meteorological conditions during these periods were relevant for the photochemical formation and accumulation of secondary species. Ambient concentrations were higher in winter, specially coinciding with development of atmospheric stagnant episodes that enhanced the accumulation of pollutants including particulate nitrate that reached concentrations of 25 µgm-3 in some occasions, day or night, under these conditions. High humidity periods favored in occasions the formation of nitrates at submicronic scale. Variations in wind direction resulted in transport of particulate nitrate from near emission areas. Size segregated aerosol was sampled during the winter campaign with a micro-orifice uniform deposit impactor (MOUDI) using eleven size stages with aluminum substrates and a quartz fiber backup filter. Samples were collected twice per day for day/night periods. The first sampling period tried to collect secondary aerosol as it started after the early morning emission period. The second sample collected the night aerosol and the emission period. Soluble ions (sulfate, nitrate, ammonium and calcium) were later analyzed by IC. The nitrate mass was concentrated in two modes, the accumulation one around 0.75 µm and the coarse one around 3.90 µm. The sulfate and ammonium masses were concentrated in the accumulation mode, around 0.50 µm, although a small peak close to 5 µm also appeared. The ammonium measured in the accumulation mode was able to neutralize the inorganic acidity caused by the nitrate and sulfate, but not the acidity in the coarse mode caused by the nitrate. This particulate nitrate was generated by the reaction of gaseous nitric acid with crustal calcium carbonate thus being calcium the neutralizing cation. Acknowledgement: Special thanks are given to the X. Querol and A. Alastauey (IDAEA-CSIC) and J.L. Jimenez (U. Colorado, CO, USA) for organizing the DAURE field campaign This part of the study has been financed by the CGL2007-3052-E/CLI, CGL2008-02817-E/CLI, PROFASE (CGL2007-64117) and GRACCIE (CSD2007-00067) projects. M.A. Revuelta acknowledges the Ministry of Science and Innovation for their economical support through the FPI predoctoral grant BES-2008-007079.

Plaza, Javier; Gómez-Moreno, Francisco J.; Aránzazu Revuelta, M.; Coz, Esther; Moreno, Natalia; Pujadas, Manuel; Artíñano, Begoña.

2010-05-01

34

Formation of halogen-induced secondary organic aerosol (XOA)  

NASA Astrophysics Data System (ADS)

Reactive halogen species (RHS) are released to the atmosphere from sources like photo-activated sea-salt aerosol and salt lakes. RHS seem to interact with SOA precursors similarly to common atmospheric oxidizing gases like OH radicals and ozone. Aerosol formation from reaction of RHS with typical SOA precursors was studied by Cai et al. (2006, 2008) using an aerosol mass spectrometer. No data is available on bromine-induced aerosol formation from organic precursors. The potential interaction of RHS with secondary organic aerosol (SOA) has recently been studied by Ofner et al. (2011). A 700 Liter aerosol smog-chamber was used to generate halogen-induced secondary organic aerosol (XOA). The chosen precursor concentration of 10 ppb for the biogenic precursors and 2 ppb for molecular chlorine and 10 ppb for molecular bromine are close to natural conditions. XOA formation in the smog chamber was initiated using a solar simulator. To follow the aerosol formation process, the aerosol size distribution, the ozone and NOx mixing ratios and the decay of the aerosol precursor were measured and compared to the calculated photolysis of the molecular halogen species. Even very low precursor and RHS concentrations form XOA particles with a mode at about 20 nm and a number concentration up to 104 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 present study compares the XOA formation potential of photolyzed chlorine and bromine with several typical SOA precursors and relates the formation to the calculated photolysis of the RHS. The formation of XOA at atmospherically relevant concentrations in an aerosol smog-chamber suggests natural XOA formation at marine sites, where organic precursor emissions (biogenic or anthropogenic) are close to RHS emitting sea-salt aerosol or salt lakes. The formation of XOA then interacts with the halogen-release cycles by slowing them down.

Ofner, J.; Kamilli, K.; Held, A.; Zetzsch, C.

2012-04-01

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

Mechanism for Production of Secondary Organic Aerosols and Their Representation in Atmospheric Models.  

National Technical Information Service (NTIS)

Table of Contents: Executive Summary; Introduction; 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 Representati...

J. H. Seinfeld R. C. Flagan

1999-01-01

37

Ozone and secondary aerosol formation — Analysis of particle observations in the 2009 SHARP campaign  

NASA Astrophysics Data System (ADS)

Particulate matters (PM) play important roles in the formation and transformation of ozone. Although photooxidation of volatile organic compounds with respect to ozone formation in the gas phase is well understood, many unknowns still exist in heterogeneous mechanisms that process soot, secondary aerosols (both inorganic and organic), and key radical precursors such as formaldehyde and nitrous acid. Our main objective is to answer two key science questions: 1) will reduction of fine PM reduce ozone formation? 2) What sources of PM are most culpable? Are they from local chemistry or long-range transport? The field data collected in the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) by our group at the Moody Tower consist of 1) real-time photolysis rates of ozone precursors, 2) particle size distributions, 3) organic carbon and elemental carbon, and 4) an archive of single particle samples taken with the Time Resolved Aerosol Collector (TRAC) sampler. The time resolution of the TRAC sampler is 30 minutes for routine measurements, and 15 minutes during some identified “events” (usually in the mid-afternoon) of high ozone and secondary organic or sulfate particle formation. The latter events last typically about an hour. Five ozone exceedance days occurred during the 6 weeks of deployment. Strong correlation between photochemical activities and organic carbon was observed. Initial data analysis indicates that secondary organic aerosol is a major component of the carbonaceous aerosols observed in Houston. Soot, secondary sulfate, seal salt, and mineral dust particles are determined from single particle analysis using scanning electron microscope and transmission electron microcopy coupled with energy dispersive X-ray spectroscopy. Compared with observations in 2000, the mass percentage of organics is higher (60 vs. 30%), and lower for sulfate (20% vs. 32%). On-going data analysis will focus on the composition, sources, and transformation of primary and secondary aerosols initiated by photolysis and subsequent heterogeneous reactions in high ozone days.

Cowin, J.; Yu, X.; Laulainen, N.; Iedema, M.; Lefer, B. L.; Anderson, D.; Pernia, D.; Flynn, J. H.

2010-12-01

38

Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing  

NASA Astrophysics Data System (ADS)

To better understand the sources of PM10 samples from Mumbai, India, aerosol chemical compositions, i.e. total carbon (TC), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and inorganic ions were studied together with specific markers such as methanesulfonate (MSA), oxalic acid (C2), azelaic acid (C9), and levoglucosan. The results revealed that biofuel/biomass burning and fossil fuel combustion are the major sources of the Mumbai aerosols. Nitrogen-isotopic (?15N) composition of aerosol total nitrogen, which ranged from 18.1 to 25.4‰, also suggest that biofuel/biomass burning is the dominant source in both summer and winter seasons. Aerosol mass concentrations of major species increased 3-4 times in winter compared to summer, indicating an enhanced emission from these sources in winter season. Photochemical production tracers, C2 diacid and nssSO42- do not show diurnal changes. Concentrations of C2 diacid and WSOC show a strong correlation (r2 = 0.95). In addition, WSOC to OC (or TC) ratios remain almost constant for day- (0.37 ± 0.06 (0.28 ± 0.04)) and nighttime (0.38 ± 0.07 (0.28 ± 0.06)), suggesting that mixing of fresh secondary organic aerosols is not significant rather the Mumbai aerosols are photochemically well processed. Concentrations of MSA and C9 diacid present a positive correlation (r2 = 0.75), indicating a marine influence on Mumbai aerosols in addition to local/regional influence. Backward air mass trajectory analyses further suggested that the Mumbai aerosols are largely influenced by long-range continental and regional transport. Stable C-isotopic ratios (?13C) of TC ranged from -27.0 to -25.4‰ with slightly lower average (-26.5 ± 0.3‰) in summer than in winter (-25.9 ± 0.3‰). Positive correlation between WSOC/TC ratios and ?13C values suggested that the increment in ?13C of wintertime TC may be caused by prolonged photochemical processing of organic aerosols in this season. This study suggests that in winter, the tropical aerosols are more aged due to longer residence time in the atmosphere than in the summer aerosols.

Aggarwal, S. G.; Kawamura, K.; Umarji, G. S.; Tachibana, E.; Patil, R. S.; Gupta, P. K.

2012-08-01

39

Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing  

NASA Astrophysics Data System (ADS)

To better understand the sources of PM10 samples in Mumbai, India, aerosol chemical composition, i.e., total carbon (TC), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and inorganic ions were studied together with specific markers such as methanesulfonate (MSA), oxalic acid (C2), azelaic acid (C9), and levoglucosan. The results revealed that biofuel/biomass burning and fossil fuel combustion are the major sources of the Mumbai aerosols. Nitrogen-isotopic (?15N) composition of aerosol total nitrogen, which ranged from 18.1 to 25.4‰, also suggests that biofuel/biomass burning is a predominate source in both the summer and winter seasons. Aerosol mass concentrations of major species increased 3-4 times in winter compared to summer, indicating enhanced emission from these sources in the winter season. Photochemical production tracers, C2 diacid and nssSO42-, do not show diurnal changes. Concentrations of C2 diacid and WSOC show a strong correlation (r2 = 0.95). In addition, WSOC to OC (or TC) ratios remain almost constant for daytime (0.37 ± 0.06 (0.28 ± 0.04)) and nighttime (0.38 ± 0.07 (0.28 ± 0.06)), suggesting that mixing of fresh secondary organic aerosols is not significant and the Mumbai aerosols are photochemically well processed. Concentrations of MSA and C9 diacid present a positive correlation (r2 = 0.75), indicating a marine influence on Mumbai aerosols in addition to local/regional influence. Backward air mass trajectory analyses further suggested that the Mumbai aerosols are largely influenced by long-range continental and regional transport. Stable C-isotopic ratios (?13C) of TC ranged from -27.0 to -25.4‰, with slightly lower average (-26.5 ± 0.3‰) in summer than in winter (-25.9 ± 0.3‰). Positive correlation between WSOC/TC ratios and ?13C values suggested that the relative increment in 13C of wintertime TC may be caused by prolonged photochemical processing of organic aerosols in this season. This study suggests that in winter, the tropical aerosols are more aged due to longer residence time in the atmosphere than in summer aerosols. However, these conclusions are based on the analysis of a limited number of samples (n=25) and more information on this topic may be needed from other similar coastal sites in future.

Aggarwal, S. G.; Kawamura, K.; Umarji, G. S.; Tachibana, E.; Patil, R. S.; Gupta, P. K.

2013-05-01

40

New Particle Formation and Secondary Organic Aerosol in Beijing  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

41

Hygroscopic properties of inorganic-salt aerosol with surface-active organic compounds  

Microsoft Academic Search

This paper investigates the hygroscopic characteristics of inorganic-salt aerosols with surface-active organic compounds (SAOCs). The experimental system includes a Tandem Differential Mobility Analyzer and a Scanning Mobility Particle Sizing System.The aerosols were prepared by mixing calcium chloride with SACs at five mass fraction of SAOCs, which are 0, 10, 16.7, 20, 25%. Four SAOCs, sodium dodecyl sulfate (SDS), sodium oleate

Ying-Yuan Chen; Whei-May Grace Lee

1999-01-01

42

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

43

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

44

Effect of hydrophobic primary organic aerosols on secondary organic aerosol formation from ozonolysis of ?-pinene  

NASA Astrophysics Data System (ADS)

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, David A.

2007-10-01

45

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

46

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

47

Effect of Hydrophilic Organic Seed Aerosols on Secondary Organic Aerosol Formation from Ozonolysis of ?-Pinene  

SciTech Connect

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

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

2011-07-26

48

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...

49

SECONDARY ORGANIC AEROSOL FORMATION FROM MIXTURES OF BIOGENIC HYDROCARBONS  

EPA Science Inventory

In this work the influence of hydrocarbon mixtures on the overall Secondary Organic Aerosol yield is investigated. Photochemical reaction experiments were conducted using mixtures of a-pinene, isoprene and propene in the presence of NOx. Results of the experiments show...

50

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics - Part 1: Surface tension depression and light-absorbing products  

NASA Astrophysics Data System (ADS)

We show that methylglyoxal forms light-absorbing secondary organic material in aqueous ammonium sulfate and ammonium nitrate solutions mimicking tropospheric aerosol particles. The light-absorbing products form on the order of minutes, and solution composition continues to change over several days. The results suggest an aldol condensation pathway involving the participation of the ammonium ion. Aqueous solutions of methylglyoxal, with and without inorganic salts, exhibit surface tension depression. Methylglyoxal uptake could potentially change the optical properties, climate effects, and heterogeneous chemistry of the seed aerosol over its lifetime.

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

2009-07-01

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

Cluster analysis on mass spectra of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

53

Size distributions of nano/micron dicarboxylic acids and inorganic ions in suburban PM episode and non-episodic aerosol  

NASA Astrophysics Data System (ADS)

The distribution of nano/micron dicarboxylic acids and inorganic ions in size-segregated suburban aerosol of southern Taiwan was studied for a PM episode and a non-episodic pollution period, revealing for the first time the distribution of these nanoscale particles in suburban aerosols. Inorganic species, especially nitrate, were present in higher concentrations during the PM episode. A combination of gas-to-nuclei conversion of nitrate particles and accumulation of secondary photochemical products originating from traffic-related emissions was likely a crucial cause of the PM episode. Sulfate, ammonium, and oxalic acid were the dominant anion, cation, and dicarboxylic acid, respectively, accounting for a minimum of 49% of the total anion, cation or dicarboxylic acid mass. Peak concentrations of these species occurred at 0.54 ?m in the droplet mode during both non-episodic and PM episode periods, indicating an association with cloud-processed particles. On average, sulfate concentration was 16-17 times that of oxalic acid. Oxalic acid was nevertheless the most abundant dicarboxylic acid during both periods, followed by succinic, malonic, maleic, malic and tartaric acid. The mass median aerodynamic diameter (MMAD) of oxalic acid was 0.77 ?m with a bi-modal presence at 0.54 ?m and 18 nm during non-episodic pollution and an MMAD of 0.67 ?m with mono-modal presence at 0.54 ?m in PM episode aerosol. The concomitant formation of malonic acid and oxalic acid was attributed to in-cloud processes. During the PM episode in the 5-100 nm nanoscale range, an oxalic acid/sulfate mass ratio of 40.2-82.3% suggested a stronger formation potential for oxalic acid than for sulfate in the nuclei mode. For total cations (TC), total inorganic anions (TIA) and total dicarboxylic acids (TDA), major contributing particles were in the droplet mode, with least in the nuclei mode. The ratio of TDA to TIA in the nuclei mode increased greatly from 8.40% during the non-episodic pollution period to 28.08% during the PM episode, favoring dicarboxylic acid formation in the nuclei mode. The evidence suggests stronger formation strength and contribution potential exists for dicarboxylic acids than for inorganic salts in nanoscale particles, especially in PM episode aerosol.

Hsieh, Li-Ying; Kuo, Su-Ching; Chen, Chien-Lung; Tsai, Ying I.

54

Hygroscopicity of secondary organic aerosols formed by oxidation of cycloalkenes, monoterpenes, sesquiterpenes, and related compounds  

NASA Astrophysics Data System (ADS)

A series of experiments has been conducted in the Caltech indoor smog chamber facility to investigate the water uptake properties of aerosol formed by oxidation of various organic precursors. Secondary organic aerosol (SOA) from simple and substituted cycloalkenes (C5-C8) is produced in dark ozonolysis experiments in a dry chamber (RH~5%). Biogenic SOA from monoterpenes, sesquiterpenes, and oxygenated terpenes is formed by photooxidation in a humid chamber (~50% RH). Using the hygroscopicity tandem differential mobility analyzer (HTDMA), we measure the diameter-based hygroscopic growth factor (GF) of the SOA as a function of time and relative humidity. All SOA studied is found to be slightly hygroscopic, with smaller water uptake than that of typical inorganic aerosol substances. The aerosol water uptake increases with time early in the experiments for the cycloalkene SOA, but decreases with time for the sesquiterpene SOA. This behavior could indicate competing effects between the formation of more highly oxidized polar compounds (more hygroscopic), and formation of longer-chained oligomers (less hygroscopic). All SOA also exhibit a smooth water uptake with RH with no deliquescence or efflorescence. The water uptake curves are found to be fitted well with an empirical three-parameter functional form. The measured pure organic GF values at 85% RH are between 1.09-1.16 for SOA from ozonolysis of cycloalkenes, 1.01-1.04 for sesquiterpene photooxidation SOA, and 1.06-1.10 for the monoterpene and oxygenated terpene SOA. The GF of pure SOA (GForg) in experiments in which inorganic seed aerosol is used is determined by assuming volume-weighted water uptake (Zdanovskii-Stokes-Robinson or "ZSR" approach) and using the size-resolved organic mass fraction measured by the Aerodyne Aerosol Mass Spectrometer. Knowing the water content associated with the inorganic fraction yields GForg values. However, for each precursor, the GForg values computed from different HTDMA-classified diameters agree with each other to varying degrees. Comparing growth factors from different precursors, we find that GForg is inversely proportional to the precursor molecular weight and SOA yield, which is likely a result of the fact that higher-molecular weight precursors tend to produce larger and less hygroscopic oxidation products.

Varutbangkul, V.; Brechtel, F. J.; Bahreini, R.; Ng, N. L.; Keywood, M. D.; Kroll, J. H.; Flagan, R. C.; Seinfeld, J. H.; Lee, A.; Goldstein, A. H.

2006-06-01

55

Hygroscopicity of secondary organic aerosols formed by oxidation of cycloalkenes, monoterpenes, sesquiterpenes, and related compounds  

NASA Astrophysics Data System (ADS)

A series of experiments has been conducted in the Caltech indoor smog chamber facility to investigate the water uptake properties of aerosol formed by oxidation of various organic precursors. Secondary organic aerosol (SOA) from simple and substituted cycloalkenes (C5-C8) is produced in dark ozonolysis experiments in a dry chamber (RH~5%). Biogenic SOA from monoterpenes, sesquiterpenes, and oxygenated terpenes is formed by photooxidation in a humid chamber (~50% RH). Using the hygroscopicity tandem differential mobility analyzer (HTDMA), we measure the diameter-based hygroscopic growth factor (GF) of the SOA as a function of time and relative humidity. All SOA studied is found to be slightly hygroscopic, with smaller water uptake than that of typical inorganic aerosol substances. The aerosol water uptake increases with time early in the experiments for the cycloalkene SOA, but decreases with time for the biogenic SOA. This behavior could indicate competing effects between the formation of more highly oxidized polar compounds (more hygroscopic), and formation of longer-chained oligomers (less hygroscopic). All SOA also exhibit a smooth water uptake with RH with no deliquescence or efflorescence. The water uptake curves are found to be fitted well with an empirical three-parameter functional form. The measured pure organic GF values at 85% RH are between 1.09-1.16 for SOA from ozonolysis of cycloalkenes, 1.01-1.04 for sesquiterpene photooxidation SOA, and 1.06-1.11 for the monoterpene and oxygenated terpene SOA. The GF of pure SOA (GForg) in experiments in which inorganic seed aerosol is used is determined by assuming volume-weighted water uptake (Zdanovskii-Stokes-Robinson or ''ZSR'' approach) and using the size-resolved organic mass fraction measured by the Aerodyne Aerosol Mass Spectrometer. Knowing the water content associated with the inorganic fraction yields GForg values. However, for each precursor, the GForg values computed from different HTDMA-classified diameters agree with each other to varying degrees. Lack of complete agreement may be a result of the non-idealities of the solutions that are not captured by the ZSR method. Comparing growth factors from different precursors, we find that GForg is inversely proportional to the precursor molecular weight and SOA yield, which is likely a result of the fact that higher-molecular weight precursors tend to produce larger and less hygroscopic oxidation products.

Varutbangkul, V.; Brechtel, F. J.; Bahreini, R.; Ng, N. L.; Keywood, M. D.; Kroll, J. H.; Flagan, R. C.; Seinfeld, J. H.; Lee, A.; Goldstein, A. H.

2006-02-01

56

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

57

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 ...

58

On the mixing and evaporation of secondary organic aerosol components.  

PubMed

The physical state and chemical composition of an organic aerosol affect its degree of mixing and its interactions with condensing species. We present here a laboratory chamber procedure for studying the effect of the mixing of organic aerosol components on particle evaporation. The procedure is applied to the formation of secondary organic aerosol (SOA) from ?-pinene and toluene photooxidation. SOA evaporation is induced by heating the chamber aerosol from room temperature (25 °C) to 42 °C over 7 h and detected by a shift in the peak diameter of the SOA size distribution. With this protocol, ?-pinene SOA is found to be more volatile than toluene SOA. When SOA is formed from the two precursors sequentially, the evaporation behavior of the SOA most closely resembles that of SOA from the second parent hydrocarbon, suggesting that the structure of the mixed SOA resembles a core of SOA from the initial precursor coated by a layer of SOA from the second precursor. Such a core-and-shell configuration of the organic aerosol phases implies limited mixing of the SOA from the two precursors on the time scale of the experiments, consistent with a high viscosity of at least one of the phases. PMID:23725344

Loza, Christine L; Coggon, Matthew M; Nguyen, Tran B; Zuend, Andreas; Flagan, Richard C; Seinfeld, John H

2013-05-31

59

Reactive intermediates revealed in secondary organic aerosol formation from isoprene  

PubMed Central

Isoprene is a significant source of atmospheric organic aerosol; however, the oxidation pathways that lead to secondary organic aerosol (SOA) have remained elusive. Here, we identify the role of two key reactive intermediates, epoxydiols of isoprene (IEPOX = ?-IEPOX + ?-IEPOX) and methacryloylperoxynitrate (MPAN), which are formed during isoprene oxidation under low- and high-NOx conditions, respectively. Isoprene low-NOx SOA is enhanced in the presence of acidified sulfate seed aerosol (mass yield 28.6%) over that in the presence of neutral aerosol (mass yield 1.3%). Increased uptake of IEPOX by acid-catalyzed particle-phase reactions is shown to explain this enhancement. Under high-NOx conditions, isoprene SOA formation occurs through oxidation of its second-generation product, MPAN. The similarity of the composition of SOA formed from the photooxidation of MPAN to that formed from isoprene and methacrolein demonstrates the role of MPAN in the formation of isoprene high-NOx SOA. Reactions of IEPOX and MPAN in the presence of anthropogenic pollutants (i.e., acidic aerosol produced from the oxidation of SO2 and NO2, respectively) could be a substantial source of “missing urban SOA” not included in current atmospheric models.

Surratt, Jason D.; Chan, Arthur W. H.; Eddingsaas, Nathan C.; Chan, ManNin; Loza, Christine L.; Kwan, Alan J.; Hersey, Scott P.; Flagan, Richard C.; Wennberg, Paul O.; Seinfeld, John H.

2010-01-01

60

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

61

Cloud condensation nuclei activity of isoprene secondary organic aerosol  

Microsoft Academic Search

This work explores the cloud condensation nuclei (CCN) activity of isoprene secondary organic aerosol (SOA), likely a significant source of global organic particulate matter and CCN, produced from the oxidation with OH from HONO\\/HOOH photolysis in a temperature-controlled SOA chamber. CCN concentrations, activation diameter, and droplet growth kinetic information were monitored as a function of supersaturation (from 0.3% to 1.5%)

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

2011-01-01

62

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

Microsoft Academic Search

Recent field and laboratory evidence indicates that the oxidation of isoprene, (2-methyl-1,3-butadiene, C5H8) forms secondary organic aerosol (SOA). Global biogenic emissions of isoprene (600 Tg yr-1) are sufficiently large that the formation of SOA in even small yields results in substantial production of atmospheric particulate matter, likely having implications for air quality and climate. Here we present a review of

A. G. Carlton; C. Wiedinmyer; J. H. Kroll

2009-01-01

63

The influence of meteorology on the organic and inorganic properties of aerosols in Hong Kong  

Microsoft Academic Search

The organic and inorganic species in total suspended particulates (TSP) collected from June to December in 1998 in Hong Kong were identified by gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) to investigate the sources of Hong Kong aerosols and the mechanisms that control the chemical compositions and variations in the atmosphere. These samples were classified according to

Mei Zheng; Zhigang Guo; Ming Fang; Dana R. Kester

2007-01-01

64

Secondary Organic Aerosol Production From Terpenes: Chemical Influences on Aerosol Yields  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosol (SOA) generation is caused by the production of relatively low vapor pressure products from higher vapor pressure precursors. Mono- and sesquiterpenes are recognized as major sources of biogenic SOA, especially following ozonolysis. SOA yields, however, depend on numerous factors. First is the widely accepted work of Pankow, Odom, and colleagues demonstrating that the partitioning of semi-volatile compounds depends strongly on the total mass of organic aerosol in a given system; extension of this theory leads us to refute the 'fallacy of the polluting tree'. Biogenic SOA yields in the absence of primary and secondary anthropogenic aerosol would be significantly lower than in polluted urban and regional environments. Other factors strongly influence SOA production. While the reaction mechanism following ozonolysis remains poorly defined, we have recently shown that SOA yields decline dramatically under high NOx conditions. However, continued oxidation, or aging, of semi-volatile organics in either phase will tend to further lower product vapor pressures, thus increasing aerosol yields. In addition to recent experimental results addressing all of these issues, we shall present a unifying framework for modeling semi-volatile partitioning and aerosol aging.

Donahue, N. M.; Huff-Hartz, K.; Presto, A. A.; Pathak, R.; Robinson, A. L.; Pandis, S. N.

2005-12-01

65

Evaluation of secondary organic aerosol formation in winter  

NASA Astrophysics Data System (ADS)

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

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

66

Aerosol Coupling in the Earths System (ACES): Linking Chemical Composition of Secondary Organic Aerosol to Hygroscopic Properties  

Microsoft Academic Search

The formation of secondary organic aerosol from the oxidation of reactive biogenic emissions is thought to be an important factor in global climate regulation. Biogenic Secondary Organic Aerosol (BSOA) can contribute to indirect radiative forcing by acting as cloud condensation nuclei. The potential of particles to act as CCN depends on their composition and hygroscopic properties. Sesquiterpenes, such as beta-caryophyllene,

J. F. Hamilton; M. R. Alfarra; K. P. Wyche; T. Carr; A. C. Lewis; P. S. Monks; G. B. McFiggans; N. A. Good; M. Irwin; F. Turner; M. Ward

2008-01-01

67

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

EPA Science Inventory

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

68

Important source of marine secondary organic aerosol from biogenic amines.  

PubMed

Relevant concentrations of dimethyl- and diethylammonium salts (DMA+ and DEA+) were measured in submicrometer marine aerosol collected over the North Atlantic during periods of high biological activity (HBA) in clean air masses (median concentration (minimum-maximum)=26(6-56) ng m(-3)). Much lower concentrations were measured during periods of low biological activity (LBA): 1 (<0.4-20) ng m(-3) and when polluted air masses were advected to the sampling site: 2 (<0.2-24) ng m(-3). DMA+ and DEA+ are the most abundantorganic species, second only to MSA, detected in fine marine particles representing on average 11% of the secondary organic aerosol (SOA) fraction and a dominant part (35% on average) of the water-soluble organic nitrogen (WSON). Several observations support the hypothesis that DMA+ and DEA+ have a biogenic oceanic source and are produced through the reaction of gaseous amines with sulfuric acid or acidic sulfates. Moreover, the water-soluble fraction of nascent marine aerosol particles produced by bubble-bursting experiments carried out in parallel to ambient aerosol sampling over the open ocean showed WSON, DMA+, and DEA+ concentrations always below the detection limit, thus excluding an important primary sea spray source. PMID:19174880

Facchini, Maria Cristina; Decesari, Stefano; Rinaldi, Matteo; Carbone, Claudio; Finessi, Emanuela; Mircea, Mihaela; Fuzzi, Sandro; Moretti, Fabio; Tagliavini, Emilio; Ceburnis, Darius; O'Dowd, Colin D

2008-12-15

69

Light-absorbing secondary organic material formed by glyoxal in aqueous aerosol mimics  

NASA Astrophysics Data System (ADS)

Light-absorbing and high-molecular-weight secondary organic products were observed to result from the reaction of glyoxal in mildly acidic (pH=4) aqueous inorganic salt solutions mimicking aqueous tropospheric aerosol particles. High-molecular-weight (500-600 amu) products were observed when ammonium sulfate ((NH4)2SO4) or sodium chloride (NaCl) was present in the aqueous phase. The products formed in the (NH4)2SO4 solutions absorb light at UV and visible wavelengths. Substantial absorption at 300-400 nm develops within two hours, and absorption between 400-600 nm develops within days. Pendant drop tensiometry measurements show that the products are not surface-active. The experimental results along with ab initio predictions of the UV/Vis absorption of potential products suggest that an aldol condensation mechanism is active in the glyoxal-(NH4)2SO4system, resulting in the formation of pi-conjugated products. If similar products are formed in atmospheric aerosol particles, they could change the optical properties of the seed aerosol over its lifetime.

Shapiro, E. L.; Szprengiel, J.; Sareen, N.; Jen, C. N.; Giordano, M. R.; McNeill, V. F.

2009-01-01

70

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

71

Isoprene forms secondary organic aerosol through cloud processing: model simulations.  

PubMed

Isoprene accounts for more than half of non-methane volatile organics globally. Despite extensive experimentation, homogeneous formation of secondary organic aerosol (SOA) from isoprene remains unproven. Herein, an incloud process is identified in which isoprene produces SOA. Interstitial oxidation of isoprene produces water-soluble aldehydes that react in cloud droplets to form organic acids. Upon cloud evaporation new organic particulate matter is formed. Cloud processing of isoprene contributes at least 1.6 Tg yr(-1) to a global biogenic SOA production of 8-40 Tg yr(-1). We conclude that cloud processing of isoprene is an important contributor to SOA production, altering the global distribution of hygroscopic organic aerosol and cloud condensation nuclei. PMID:16047779

Lim, Ho-Jin; Carlton, Annmarie G; Turpin, Barbara J

2005-06-15

72

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

73

A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/citric acid and in the ammonium sulfate/glutaric acid cases. However, we observe significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces.

Zardini, A. A.; Sjogren, S.; Marcolli, C.; Krieger, U. K.; Gysel, M.; Weingartner, E.; Baltensperger, U.; Peter, T.

2008-03-01

74

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

75

Bounce behavior of freshly nucleated biogenic secondary organic aerosol particles  

NASA Astrophysics Data System (ADS)

The assessment of the climatic impacts and adverse health effects of atmospheric aerosol particles requires detailed information on particle properties. However, very limited information is available on the morphology and phase state of secondary organic aerosol (SOA) particles. The physical state of particles greatly affects particulate-phase chemical reactions, and thus the growth rates of newly formed atmospheric aerosol particles. Thus verifying the physical phase state of SOA particles gives new and important insight into their formation, subsequent growth, and consequently potential atmospheric impacts. According to our recent study, biogenic SOA particles produced in laboratory chambers from the oxidation of real plant emissions as well as in ambient boreal forest atmospheres can exist in a solid phase in size range >30 nm. In this paper, we extend previously published results to diameters in the range of 17-30 nm. The physical phase of the particles is studied by investigating particle bounce properties utilizing electrical low pressure impactor (ELPI). We also investigate the effect of estimates of particle density on the interpretation of our bounce observations. According to the results presented in this paper, particle bounce clearly decreases with decreasing particle size in sub 30 nm size range. The decreasing bounce can be caused by the differences in composition and phase of large (diameters greater than 30 nm) and smaller (diameters between 17 and 30 nm) particles.

Virtanen, A.; Kannosto, J.; Joutsensaari, J.; Saukko, E.; Kuuluvainen, H.; Hao, L.; Yli-Pirilä, P.; Tiitta, P.; Holopainen, J. K.; Worsnop, D. R.; Smith, J. N.; Laaksonen, A.

2011-03-01

76

Bounce behavior of freshly nucleated biogenic secondary organic aerosol particles  

NASA Astrophysics Data System (ADS)

The assessment of the climatic impacts and adverse health effects of atmospheric aerosol particles requires detailed information on particle properties. However, very limited information is available on the morphology and phase state of secondary organic aerosol (SOA) particles. The physical state of particles greatly affects particulate-phase chemical reactions, and thus the growth rates of newly formed atmospheric aerosol. Thus verifying the physical phase state of SOA particles gives new and important insight into their formation, subsequent growth, and consequently potential atmospheric impacts. According to our recent study, biogenic SOA particles produced in laboratory chambers from the oxidation of real plant emissions as well as in ambient boreal forest atmospheres can exist in a solid phase in size range >30 nm. In this paper, we extend previously published results to diameters in the range of 17-30 nm. The physical phase of the particles is studied by investigating particle bounce properties utilizing electrical low pressure impactor (ELPI). We also investigate the effect of estimates of particle density on the interpretation of our bounce observations. According to the results presented in this paper, particle bounce clearly decreases with decreasing particle size in sub 30 nm size range. The comparison measurements by ammonium sulphate and investigation of the particle impaction velocities strongly suggest that the decreasing bounce is caused by the differences in composition and phase of large (diameters greater than 30 nm) and smaller (diameters between 17 and 30 nm) particles.

Virtanen, A.; Kannosto, J.; Kuuluvainen, H.; Arffman, A.; Joutsensaari, J.; Saukko, E.; Hao, L.; Yli-Pirilä, P.; Tiitta, P.; Holopainen, J. K.; Keskinen, J.; Worsnop, D. R.; Smith, J. N.; Laaksonen, A.

2011-08-01

77

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.

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

78

Nonequilibrium atmospheric secondary organic aerosol formation and growth.  

PubMed

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 NO(3) radicals at room temperature. SOA is primarily formed from low-volatility ozonolysis products, with a small contribution from higher volatility organic nitrates from the NO(3) reaction. Contrary to expectations, the particulate nitrate concentration is not consistent with equilibrium partitioning between the gas phase and a liquid particle. Rather the fraction of organic nitrates in the particles is only explained by irreversible, kinetically determined uptake of the nitrates on existing particles, with an uptake coefficient that is 1.6% of that for the ozonolysis products. If the nonequilibrium particle formation and growth observed in this atmospherically important system is a general phenomenon in the atmosphere, aerosol models may need to be reformulated. The reformulation of aerosol models could impact the predicted evolution of SOA in the atmosphere both outdoors and indoors, its role in heterogeneous chemistry, its projected impacts on air quality, visibility, and climate, and hence the development of reliable control strategies. PMID:22308444

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

2012-01-30

79

Inorganic and black carbon aerosols in the Los Angeles Basin during CalNex  

NASA Astrophysics Data System (ADS)

We evaluate predictions from the Community Multiscale Air Quality (CMAQ version 4.7.1) model against a suite of airborne and ground-based meteorological measurements, gas- and aerosol-phase inorganic measurements, and black carbon (BC) measurements over Southern California during the CalNex field campaign in May/June 2010. Ground-based measurements are from the CalNex Pasadena ground site, and airborne measurements took place onboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Navy Twin Otter and the NOAA WP-3D aircraft. BC predictions are in general agreement with observations at the Pasadena ground site and onboard the WP-3D, but are consistently overpredicted when compared to Twin Otter measurements. Adjustments to predicted inorganic mass concentrations, based on predicted aerosol size distributions and the AMS transmission efficiency, are shown to be significant. Owing to recent shipping emission reductions, the dominant source of sulfate in the L.A. Basin may now be long-range transport. Sensitivity studies suggest that severely underestimated ammonia emissions, and not the exclusion of crustal species (Ca2 +, K+, and Mg2 +), are the single largest contributor to measurement/model disagreement in the eastern part of the L.A. Basin. Despite overstated NOx emissions, total nitrate concentrations are underpredicted, which suggests a missing source of HNO3 and/or overprediction of deposition rates. Adding gas-phase NH3 measurements and size-resolved measurements, up to 10 ?m, of nitrate and various cations (e.g. Na+, Ca2 +, K+) to routine monitoring stations in the L.A. Basin would greatly facilitate interpreting day-to-day fluctuations in fine and coarse inorganic aerosol.

Ensberg, J. J.; Craven, J. S.; Metcalf, A. R.; Allan, J. D.; Angevine, W. M.; Bahreini, R.; Brioude, J.; Cai, C.; Coe, H.; Gouw, J. A.; Ellis, R. A.; Flynn, J. H.; Haman, C. L.; Hayes, P. L.; Jimenez, J. L.; Lefer, B. L.; Middlebrook, A. M.; Murphy, J. G.; Neuman, J. A.; Nowak, J. B.; Roberts, J. M.; Stutz, J.; Taylor, J. W.; Veres, P. R.; Walker, J. M.; Seinfeld, J. H.

2013-02-01

80

Secondary Organic Aerosol Formation from Anthropogenic Air Pollution: Rapid and Higher than Expected  

Microsoft Academic Search

In urban areas the sources of organic aerosol comprise primary emissions of organic aerosol (POA) and volatile organic compounds (VOCs) as precursors for secondary organic aerosol (SOA). SOA is formed from low volatility products of VOC oxidation. Recent field studies offer evidence that current models greatly underestimate SOA. State-of-the-art SOA models parameterize the results of simulation chamber experiments that bracket

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

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, 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

82

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

2011-02-12

83

Simulation Chamber Investigations of Secondary Organic Aerosol Formation From Boreal Tree Emissions: Dependence on VOC Classes  

Microsoft Academic Search

A considerable fraction of the organic aerosol component is of secondary origin, meaning it is formed through oxidation of volatile organic compounds (VOCs). Plant emissions, e.g. monoterpenes and sesquiterpenes, are a major source of VOCs in the troposphere. So far most laboratory and simulation chamber investigations on the potential to form secondary organic aerosols (SOA) from plant emissions focused on

A. Kiendler-Scharr; T. F. Mentel; E. Kleist; T. Hohaus; A. Mensah; C. Spindler; R. Tillmann; R. Uerlings; M. Dal Maso; Y. Rudich; W. Juergen

2008-01-01

84

Aerosol and Inorganic Gaseous Iodine at Appledore Island, Maine During Summers 2004, 2005 and 2006  

NASA Astrophysics Data System (ADS)

Iodine chemistry may affect the ozone budget in the marine atmosphere and has been hypothesized to play an important role in aerosol nucleation and/or growth in surface air, particularly in coastal regions where marine macrophytes are a prolific source of organoiodine gases. Total iodine was determined by neutron activation analysis in: 1) daytime and nighttime samples of bulk and size segregated aerosols (Iaer) and of inorganic gaseous iodine (Iig) collected on LiOH-impregnated filters during summer 2004, 2) daytime and nighttime samples of PM2.5 aerosol samples collected during summers 2005 and 2006, and 3) 1- to 3- hour duration PM2.5 samples collected over four diel cycles during summer 2006 at Appledore Island (AI), ME, approximately 10 km offshore from Portsmouth, NH. A parallel set of PM2.5 samples was collected in 2005 at Durham, NH, approximately 20 km inland from Portsmouth. The 2004 data indicated that the inorganic I pool at AI is mainly gaseous (average 88%) and that Iaer is mainly (average 88%) associated with sub-?m diameter particles. Concentrations in both phases were similar to those observed by others in the 1970s over the tropical and subtropical North Atlantic. Daytime Iaer and Iig concentrations both tended to be greater than respective nighttime concentrations. Iaer concentrations in 2005 and 2006 were significantly higher than in 2004 and displayed pronounced day/night differences. The diel cycle studies in 2006 confirmed that Iaer was low at night (average 3.3 ng m-3) and high (average 8.3 ng m-3) during the day. The timing of the daily maximum varied over the four days sampled. These data imply active multiphase photochemical processing of iodine in the vicinity of the AI site. Iaer concentrations at the Durham site inland were significantly lower than at AI and showed no significant day/night difference.

Pszenny, A.; Cotter, K.; Deegan, B.; Fischer, E.; Griffin, R.; Johnson, D.; Keene, W.; Maben, J.; Seidel, T.; Smith, A.; Ziemba, L.

2006-12-01

85

A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/glutaric acid system; deviations up to 10% in mass growth factor (corresponding to deviations up to 3.5% in size growth factor) are observed for the ammonium sulfate/citric acid 1:1 mixture at 80% RH. We observe even more significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces.

Zardini, A. A.; Sjogren, S.; Marcolli, C.; Krieger, U. K.; Gysel, M.; Weingartner, E.; Baltensperger, U.; Peter, T.

2008-09-01

86

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

87

Secondary organic aerosol coating of synthetic metal-oxide nanoparticles.  

PubMed

Secondary organic aerosol (SOA) from the ?-pinene + ozone reaction readily coats TiO(2) and CeO(2) metal-oxide nanoparticles in smog-chamber experiments under atmospherically relevant conditions. Otherwise identical experiments compared bare nanoparticles and nanoparticles coated with poly(acrylic acid) (PAA). The PAA-coated particles result in significantly higher new-particle formation rates, suggesting that the SOA vapors coat bare metal oxide more readily than the PAA. After particles begin to grow via SOA coating, however, all particles, independent of size or the presence of a metal-oxide core, grow with a rate proportional to their surface area, modified to account for gas-phase diffusion in the transition regime between the kinetic and bulk-flow regimes. This suggests that SOA condensational growth may be modeled based on the size distribution of the condensational sink in the atmosphere. PMID:21534558

Lee, Joohyung; Donahue, Neil M

2011-05-02

88

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

2013-03-27

89

Anthropogenic Influence on Secondary Aerosol Formation and Total Water-Soluble Carbon on Atmospheric Particles  

NASA Astrophysics Data System (ADS)

On a global scale, the atmosphere is an important source of nutrients, as well as pollutants, because of its interfaces with soil and water. Important compounds in the gaseous phase are in both organic and inorganic forms, such as organic acids, nitrogen, sulfur and chloride. In spite of the species in gas form, a huge number of process, anthropogenic and natural, are able to form aerosols, which may be transported over long distances. Sulfates e nitrates are responsible for rain acidity; they may also increase the solubility of organic compounds and metals making them more bioavailable, and also can act as cloud condensation nuclei (CCN). Aerosol samples (PM2.5) were collected in a rural and industrial area in Rio de Janeiro, Brazil, in order to quantify chemical species and evaluate anthropogenic influences in secondary aerosol formation and organic compounds. Samples were collected during 24 h every six days using a high-volume sampler from August 2010 to July 2011. The aerosol mass was determined by Gravimetry. The water-soluble ionic composition (WSIC) was obtained by Ion Chromatography in order to determine the major anions (NO3-, SO4= and Cl-); total water-soluble carbon (TWSC) was determined by a TOC analyzer. The average aerosol (PM2.5) concentrations ranged from 1 to 43 ug/m3 in the industrial site and from 4 to 35 ug/m3 in the rural area. Regarding anions, the highest concentrations were measured for SO42- (10.6 ?g/m3-12.6 ?g/m3); where the lowest value was found in the rural site and the highest in the industrial. The concentrations for NO3- and Cl- ranged from 4.2 ?g/m3 to 9.3 ?g/m3 and 3.1 ?g/m3 to 6.4 ?g /m3, respectively. Sulfate was the major species and, like nitrate, it is related to photooxidation in the atmosphere. Interestingly sulfate concentrations were higher during the dry period and could be related to photochemistry activity. The correlations between nitrate and non-sea-salt sulfate were weak, suggesting different sources for these species. The secondary aerosol represented an important fraction of total compounds in PM2.5 ranged from 16 to 18% for (NH4)2SO4 and 6 to 8% for NH4NO3. The values for TWSC ranged from 0.28 to 6.35 ?g/m3 in the industrial area and 0.12 to 7.49 ?g/m3 for rural area. The similarity between the areas regarding secondary aerosols formation and water-soluble carbon compounds is probably due to the particle size.

Gioda, Adriana; Mateus, Vinicius; Monteiro, Isabela; Taira, Fabio; Esteves, Veronica; Saint'Pierre, Tatiana

2013-04-01

90

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

91

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

92

Correlation of Secondary Organic Aerosol with Odd Oxygen in Mexico City  

SciTech Connect

Data collected from a mountain location within the Mexico City limits are used to demonstrate a correlation between secondary organic aerosol and odd-oxygen (O3 + NO2). Positive matrix factorization techniques are employed to separate organic aerosol components: hydrocarbon-like organic aerosol; oxidized-organic aerosol; and biomass burning organic aerosol. The measured hydrocarbon-like organic aerosol is correlated with urban CO (8±1) µg m-3 ppmv-1. The measured oxidized-organic aerosol is associated with photochemical oxidation products and correlates with odd-oxygen with an apparent slope of (70-120) µg m-3 ppmv-1. The dependence of the oxidized-organic aerosol to odd-oxygen correlation on the nature of the gas-phase hydrocarbon profile is discussed.

Herndon, Scott C.; Onasch, Timothy B.; Wood, Ezra C.; Kroll, Jesse H.; Canagaratna, M. R.; Jayne, John T.; Zavala, Miguel A.; Knighton, W. Berk; Mazzoleni, Claudio; Dubey, Manvendra K.; Ulbrich, Ingrid M.; Jimenez, Jose L.; Seila, Robert; de Gouw, Joost A.; de Foy, B.; Fast, Jerome D.; Molina, Luisa T.; Kolb, C. E.; Worsnop, Douglas R.

2008-08-05

93

CCN activity and volatility of ?-caryophyllene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

94

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

95

Influence of environmental parameters on secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

The influence of environmental parameters on secondary organic aerosol (SOA) was extensively investigated in the UC Riverside/CE-CERT environmental chamber. The presence of water vapor provided an additional SOA formation pathway during cyclohexene ozonolysis that increased SOA formation by ˜30%. The presence of dissolved salts had minimal impact as compared to the presence of water vapor. Temperature proved to be an important SOA formation parameter; aerosol formation increased by 3.5 times at 278K as compared to 300K for both alpha-pinene and cyclohexene isothermal ozonolysis. Changing experimental temperatures, in most cases led to a different gas-particle equilibrium, even after returning to the original temperature set point. A model, temperature influenced partitioning aerosol yield (TIPAY), was created to explain these results by incorporating a thermally labile component, a traditional gas to particle partitioning component, and an additional gas to particle partitioning component whose formation potential was temperature independent. Increasing light intensity, measured as the photolysis rate of NO2 to NO (k1), was found to increase SOA formation for the m-xylene/NOx photooxidation system. Irradiation source had a slight effect on total SOA formation as an irradiation spectrum more similar to natural light produced slightly more SOA than that with black lights, provides the wavelengths necessary for NO2 photolysis, at the same light intensity. Modeling of the gas phase chemistry with SAPRC07, supports the idea that the concentration of radical species OH and HO 2 greatly determine the amount of SOA formation. Building on SAPRC07, the SOA formation model PM-SAPRC08, was developed to determine the dominate gas phase reactions needed to predict SOA formation results for 100 experiments. While 7 simulations are tested, several of which are published routes, none adequately predicted SOA formation. Results of the influence of these environmental parameters provide a wealth of experimental data, along with model simulations that provide insight to SOA formation behavior and SOA formation mechanisms; essential to bridging the apparent disconnect between models of SOA production based on environmental chambers and that estimated from direct ambient measurements.

Warren, Bethany A.

96

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

97

[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

98

Hygroscopicity of internally mixed aerosol particles containing benzoic acid and inorganic salts  

NASA Astrophysics Data System (ADS)

The hygroscopic behaviors of benzoic acid (BA) particles and internal mixtures of inorganic salts (sodium chloride and ammonium sulfate) and BA are investigated in the 10-90% RH using the hygroscopicity tandem differential mobility analyzer (H-TDMA) system. Different morphology of BA, NaCl-BA, and (NH4)2SO4-BA particles at representative RH is characterized by Transmission Electron Microscopy (TEM). The hygroscopic growth factors (GFs) of BA exhibit a significant reduction in the 75-85% RH, followed by a slight increase at 90% RH. Internally mixed NaCl-BA and (NH4)2SO4-BA particles display deliquescence transitions at 70% RH, followed by apparently hampered hygroscopic growth due to the presence of BA. According to the TEM results, the morphology of BA particles and mixed particles show marked change in humidification, which possibly can be attributed to the strong microstructural rearrangement of BA fraction. This significant restructuring is responsible for the GFs change of BA particles and the hygroscopic behaviors transformation of mixed NaCl-BA and (NH4)2SO4-BA particles. These results demonstrate that atmospheric BA could significantly influence the hygroscopic properties of inorganic aerosols.

Shi, Yajun; Ge, Maofa; Wang, Weigang

2012-12-01

99

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 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 were compared for the Tokyo, Japan, metropolitan area with measurements made using an Aerodyne quadrupole aerosol mass spectrometer

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

2009-01-01

100

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

101

TEMPERATURE DEPENDENCE OF THE YIELD OF SECONDARY ORGANIC AEROSOL FROM THE OZONOLYSIS OF ?-PINENE AND LIMONENE  

Microsoft Academic Search

Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humid- ity for the ozone-initiated reaction of the two monoter- penes -pinene (243-313 K) and limonene (253-313 K) us- ing the 84.5 m 3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parame- ters specifically useful for aerosol yield calculations.

H. SAATHOFF; C. LINKE; K.-H. NAUMANN; R. WAGNER; E. WEINGARTNER; U. SCHURATH; F. Mentel; R. Tillmann

2009-01-01

102

Chemical characterization of secondary organic aerosol from aromatic precursors in smog chamber experiments  

Microsoft Academic Search

In a newly built smog chamber (27m^3 volume) at the Paul Scherrer Institute secondary organic aerosols were produced from photo-oxidation products of aromatic compounds. The aerosol composition as well as gas phase reaction products was analyzed. Aerosol collected on filter samples was analyzed with gas chromatography \\/ mass spectrometry GC\\/MS after derivatization of carbonyl, carboxyl and hydroxyl functional groups to

M. Kalberer; M. Sax; R. Zenobi; D. Paulsen; M. Steinbacher; A. Prevot; E. Weingartner; U. Baltensperger

2003-01-01

103

Processes influencing secondary aerosol formation in the San Joaquin Valley during winter  

SciTech Connect

Air quality data collected in the California Regional PM10/PM2.5 Air Quality Study (CRPAQS) are analyzed to qualitatively assess the processes affecting secondary aerosol formation in the San Joaquin Valley (SJV). This region experiences some of the highest fine particulate matter (PM2.5) mass concentrations in California ({le} 188 {mu}g/m{sup 3} 24-hr average), and secondary aerosol components (as a group) frequently constitute over half of the fine aerosol mass in winter. The analyses are based on 15 days of high-frequency filter and canister measurements and several months of wintertime continuous gas and aerosol measurements. The phase-partitioning of nitrogen oxide (NOx)-related nitrogen species and carbonaceous species shows that concentrations of gaseous precursor species are far more abundant than measured secondary aerosol nitrate or estimated secondary organic aerosols. Comparisons of ammonia and nitric acid concentrations indicate that ammonium nitrate formation is limited by the availability of nitric acid rather than ammonia. Time-resolved aerosol nitrate data collected at the surface and on a 90-m tower suggest that both the daytime and nighttime nitric acid formation pathways are active, and entrainment of aerosol nitrate formed aloft at night may explain the spatial homogeneity of nitrate in the SJV. NOx and volatile organic compound (VOC) emissions plus background O{sub 3} levels are expected to determine NOx oxidation and nitric acid production rates, which currently control the ammonium nitrate levels in the SJV. Secondary organic aerosol formation is significant in winter, especially in the Fresno urban area. Formation of secondary organic aerosol is more likely limited by the rate of VOC oxidation than the availability of VOC precursors in winter. 59 refs., 11 figs., 1 tab.

Frederick W. Lurmann; Steven G. Brown; Michael C. McCarthy; Paul T. Roberts [Sonoma Technology, Inc., Petaluma, CA (United States)

2006-12-15

104

Formation of semivolatile inorganic aerosols in the mexico city metropolitan area during the milagro campaign  

NASA Astrophysics Data System (ADS)

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 gas and particulate phases. In this work the PMCAMx-2008 CTM, which includes the recently developed aerosol thermodynamic model ISORROPIA-II, is applied in the Mexico City Metropolitan Area in order to simulate the formation of the major inorganic aerosol components. The main sources of SO2 (such as the Miguel Hidalgo Refinery and the Francisco Perez Rios Power Plant) in the Mexico City Metropolitan Area (MCMA) are located in Tula, resulting in high predicted PM1 sulfate concentrations (over 25 ?g m-3) in that area. The average predicted PM1 nitrate concentrations are up to 3 ?g m-3 (with maxima up to 11 ?g m-3) in and around the urban center, mostly produced from local photochemistry. The presence of calcium coming from the Tolteca area (7 ?g m-3) as well as the rest of the mineral cations (1 ?g m-3 potassium, 1 ?g m-3 magnesium, 2 ?g m-3 sodium, and 3 ?g m-3 calcium) from the Texcoco Lake resulted in the formation of a significant amount of aerosol nitrate in the coarse mode with concentrations up to 3 ?g m-3 over these areas. PM1-10 chloride is also high and its concentration exceeds 2 ?g m-3 in Texcoco Lake. PM ammonium concentrations peak at the center of Mexico City (2 ?g m-3) and the Tula vicinity (2.5 ?g m-3). The performance of the model for the major inorganic PM components (sulfate, ammonium, nitrate, chloride, sodium, calcium, and magnesium) is encouraging. At T0, the average measured values of PM1 sulfate, nitrate, ammonium, and chloride are 3.6 ?g m-3, 3.6 ?g m-3, 2.1 ?g m-3, and 0.35 ?g m-3 respectively. The corresponding predicted values are 3.7 ?g m-3, 2.8 ?g m-3, 1.7 ?g m-3, and 0.25 ?g m-3. Additional improvements are possible by (i) using a day-dependent emission inventory, (ii) improving the performance of the model regarding the oxidant levels, and (iii) revising the emissions and the chemical composition of the fugitive dust. Sensitivity tests indicate that sulfate concentration in Tula decreases by up to 0.5 ?g m-3 after a 50 % reduction of SO2 emissions while it can increase by up to 0.3 ?g m-3 when NOx emissions are reduced by 50 %. Nitrate concentration decreases by up to 1 ?g m-3 after the 50 % reduction of NOx or NH3 emissions. Ammonium concentration decreases by up to 1 ?g m-3, 0.3 ?g m-3, and 0.1 ?g m-3 after the 50 % reduction of NH3, NOx, and SO2 emissions respectively.

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

2011-08-01

105

Volatility of secondary organic aerosols from the ozone initiated oxidation of ? -pinene and limonene  

Microsoft Academic Search

The volatility of secondary organic aerosol (SOA) from the ozone initiated oxidation of ?-pinene and limonene has been investigated in a large aerosol chamber facility, the AIDA chamber of Research Centre Karlsruhe, by using a volatility tandem-DMA system (VTDMA). The volatility of particles has been classified by monitoring the change in particle peak diameter at temperatures between 298 and 583K.

Åsa M. Jonsson; Mattias Hallquist; Harald Saathoff

2007-01-01

106

Hygroscopicity of secondary organic aerosols formed by oxidation of cycloalkenes, monoterpenes, sesquiterpenes, and related compounds  

Microsoft Academic Search

A series of experiments has been conducted in the Caltech indoor smog chamber facility to investigate the water uptake properties of aerosol formed by oxidation of various organic precursors. Secondary organic aerosol (SOA) from simple and substituted cycloalkenes (C5-C8) is produced in dark ozonolysis experiments in a dry chamber (RH~5%). Biogenic SOA from monoterpenes, sesquiterpenes, and oxygenated terpenes is formed

V. Varutbangkul; F. J. Brechtel; R. Bahreini; N. L. Ng; M. D. Keywood; J. H. Kroll; R. C. Flagan; J. H. Seinfeld; A. Lee; A. H. Goldstein

2006-01-01

107

Secondary organic aerosol yields of 12-carbon alkanes  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high- and low-NOx conditions, in which alkyl peroxy radicals (RO2) react primarily with NO and HO2, respectively, for multiple initial alkane concentrations. Experiments were run until 95-100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases. SOA yield differed by 2 orders of magnitude between the two limiting cases, but the same trends among alkane precursors were observed for both limiting cases. Vapor-phase wall losses were addressed through a modeling study and increased SOA yield uncertainty by approximately 30%. SOA yields were highest from cyclododecane under both NOx conditions. Under high-NOx conditions, SOA yields increased from 2-methylundecane < dodecane ~ hexylcyclohexane < cyclododecane, consistent with previous studies. Under low-NOx conditions, SOA yields increased from 2-methylundecane ~ dodecane < hexylcyclohexane < cyclododecane. The presence of cyclization in the parent alkane structure increased SOA yields, whereas the presence of branch points decreased SOA yields due to increased vapor-phase fragmentation. Vapor-phase fragmentation was found to be more prevalent under high-NOx conditions than under low-NOx conditions. For different initial concentrations of the same alkane and same NOx conditions, SOA yield did not correlate with SOA mass throughout SOA growth, suggesting kinetically limited SOA growth for these systems.

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

2013-08-01

108

Ozone-driven secondary organic aerosol production chain.  

PubMed

Acidic sulfate particles are known to enhance secondary organic aerosol (SOA) mass in the oxidation of biogenic volatile organic compounds (BVOCs) through accretion reactions and organosulfate formation. Enhanced phase transfer of epoxides, which form during the BVOC oxidation, into the acidified sulfate particles is shown to explain the latter process. We report here a newly identified ozone-driven SOA production chain that increases SOA formation dramatically. In this process, the epoxides interact with acidic sulfate particles, forming a new generation of highly reactive VOCs through isomerization. These VOCs partition back into the gas phase and undergo a new round of SOA forming oxidation reactions. Depending on the nature of the isomerized VOCs, their next generation oxidation forms highly oxygenated terpenoic acids or organosulfates. Atmospheric evidence is presented for the existence of marker compounds originating from this chain. The identified process partly explains the enhanced SOA formation in the presence of acidic particles on a molecular basis and could be an important source of missing SOA precursor VOCs that are currently not included in atmospheric models. PMID:23488636

Iinuma, Yoshiteru; Kahnt, Ariane; Mutzel, Anke; Böge, Olaf; Herrmann, Hartmut

2013-04-01

109

Secondary organic aerosol from biogenic volatile organic compound mixtures  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

110

Model Representation of Secondary Organic Aerosol in CMAQ v4.7  

EPA Science Inventory

Numerous scientific upgrades to the representation of secondary organic aerosol (SOA) are incorporated into the Community Multiscale Air Quality (CMAQ) modeling system. Additions include several recently identified SOA precursors: benzene, isoprene, and sesquiterpenes; and pathwa...

111

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

EPA Science Inventory

Secondary organic aerosols (SOA), known to form in the atmosphere from oxidation of volatile organic compounds (VOCs) emitted by anthropogenic and biogenic sources, are a poorly understood but substantial component of atmospheric particles. In this study, we examined the chemic...

112

Modeling the formation of secondary organic aerosol within a comprehensive air quality model system  

Microsoft Academic Search

The Secondary Organic Aerosol Model (SORGAM) has been developed for use in comprehensive air quality model systems. Coupled to a chemistry-transport model, SORGAM is capable of simulating secondary organic aerosol (SOA) formation including the production of low-volatility products and their subsequent gas\\/particle partitioning. The current model formulation assumes that all SOA compounds interact and form a quasi-ideal solution. This has

Benedikt Schell; Ingmar J. Ackermann; Heinz Hass; Francis S. Binkowski; Adolf Ebel

2001-01-01

113

Computation of Phase Equilibria, State Diagrams and Gas/Particle Partitioning of Mixed Organic-Inorganic Aerosols  

NASA Astrophysics Data System (ADS)

The chemical composition of organic-inorganic aerosols is linked to several processes and specific topics in the field of atmospheric aerosol science. Photochemical oxidation of organics in the gas phase lowers the volatility of semi-volatile compounds and contributes to the particulate matter by gas/particle partitioning. Heterogeneous chemistry and changes in the ambient relative humidity influence the aerosol composition as well. Molecular interactions between condensed phase species show typically non-ideal thermodynamic behavior. 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 organics and inorganics (Erdakos and Pankow, 2004; Chang and Pankow, 2006). Moreover, the phases present in the aerosol particles feed back on the heterogeneous, multi-phase chemistry, influence the scattering and absorption of radiation and affect the CCN ability of the particles. Non-ideal thermodynamic behavior in mixtures is usually described by an expression for the excess Gibbs energy, enabling the calculation of activity coefficients. We use the group-contribution model AIOMFAC (Zuend et al., 2008) to calculate activity coefficients, chemical potentials and the total Gibbs energy of mixed organic-inorganic systems. This thermodynamic model was combined with a robust global optimization module to compute potential liquid-liquid (LLE) and vapor-liquid-liquid equilibria (VLLE) as a function of particle composition at room temperature. And related to that, the gas/particle partitioning of semi-volatile components. Furthermore, we compute the thermodynamic stability (spinodal limits) of single-phase solutions, which provides information on the process type and kinetics of a phase separation. References Chang, E. I. and Pankow, J. F.: Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water - Part 2: Consideration of phase separation effects by an XUNIFAC model, Atmos. Environ., 40, 6422-6436, 2006. Erdakos, G. B. and Pankow, J. F.: Gas/particle partitioning of neutral and ionizing compounds to single- and multi-phase aerosol particles. 2. Phase separation in liquid particulate matter containing both polar and low-polarity organic compounds, Atmos. Environ., 38, 1005-1013, 2004. 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.; Peter, T.

2009-04-01

114

Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity  

NASA Astrophysics Data System (ADS)

Concentrations of 5 gases (HCl, HNO3, HONO, NH3, SO2) and 8 major inorganic ions in particles (Cl-, NO3-, SO42-, NH4+, Na+, K+, Mg2+, Ca2+) were measured with an online monitor MARGA 2S in two size ranges, Dp <2.5 ?m and Dp < 10 ?m, in Helsinki, Finland from November 2009 to May 2010. The results were compared with filter sampling, mass concentrations obtained from particle number size distributions, and a conventional SO2 monitor. The MARGA yielded lower concentrations than those analyzed from the filter samples for most ions. Linear regression yielded the following MARGA vs. filter slopes: 0.72 for Cl-, 0.90 for NO3-, 0.85 for SO42-, 0.91 for NH4+ , 0.49 for Na+, 3.0 for Mg2+, and 3.0 for Ca2+ and 0.90 for the MARGA vs. SO2 monitor. For K+ there were not enough data points to calculate a statistically significant linear regression. There were clear seasonal cycles in the concentrations of the nitrogen-containing gases: the median concentrations of HNO3, HONO, and NH3 were 0.09 ppb, 0.37 ppb, and 0.01 ppb in winter, respectively, and 0.15, 0.15, and 0.14 in spring, respectively. The gas-phase fraction of nitrogen decreased roughly with decreasing temperature, so that in the coldest period from January to February the median contribution was 28% but in April to May was 53%. There were also large fractionation variations that temperature alone cannot explain. HONO correlated well with NOx but a large fraction of the HONO-to-NOx ratios were larger than published ratios in a road traffic tunnel, suggesting that a large amount of HONO had other sources than vehicle exhaust. Aerosol acidity was estimated by calculating ion equivalent ratios. The sources of acidic aerosols were studied with trajectory statistics that showed that continental aerosol is mainly neutralized and marine aerosol acidic.

Makkonen, U.; Virkkula, A.; Mäntykenttä, J.; Hakola, H.; Keronen, P.; Vakkari, V.; Aalto, P. P.

2012-06-01

115

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics - Part 2: Product identification using Aerosol-CIMS  

NASA Astrophysics Data System (ADS)

We used chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol-CIMS) to characterize secondary organic material formed by methylglyoxal with ammonium sulfate in aqueous aerosol mimics. Bulk reaction mixtures were diluted and atomized to form submicron aerosol particles. Organics were detected using Aerosol-CIMS in positive and negative ion mode using I- and H3O+·(H2O)n as reagent ions. The results are consistent with aldol condensation products, carbon-nitrogen species, sulfur-containing compounds, and oligomeric species up to 759 amu. These results support previous observations by us and others that ammonium sulfate plays a critical role in the SOA formation chemistry of dicarbonyl compounds.

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

2009-07-01

116

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

117

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...

118

The influence of meteorology on the organic and inorganic properties of aerosols in Hong Kong  

NASA Astrophysics Data System (ADS)

The organic and inorganic species in total suspended particulates (TSP) collected from June to December in 1998 in Hong Kong were identified by gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) to investigate the sources of Hong Kong aerosols and the mechanisms that control the chemical compositions and variations in the atmosphere. These samples were classified according to the climate: wet, dry under the influence of southerly winds from the sea (Dry-S) and dry under the influence of northerly winds from the continent (Dry-N). There were significant increases of materials from crustal, biogenic and pollution sources in the Dry-N period by a factor of 5, 4, and 2, respectively. Since the crustal tracers (e.g., Al, Fe) could be from coal flyash, the estimate of crustal material in the Dry-N period may include some materials from pollution source. Therefore, a positive correlation between crustal and pollution elements was observed. From the analysis of solvent-extractable organics (SEOC), microbial and meat cooking sources showed slight increase (1.2-fold). Higher levels of plant wax materials in the Dry-N period were probably due to the higher wind speed during the winter monsoon. The percentage of crustal material in TSP was 47% in the Dry-N period, and only 22% in the wet season and the Dry-S period. Plant wax materials (biogenic source) had a higher percentage in the Dry-N period (39% of SEOC) while microbial and meat cooking sources accounted for 49% of SEOC in the wet season. This study revealed that wind direction and precipitation had a significant influence not only on the concentrations but also on the chemical compositions and sources of Hong Kong aerosols.

Zheng, Mei; Guo, Zhigang; Fang, Ming; Kester, Dana R.

2007-06-01

119

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

120

Chemical Processing of Secondary Aerosol Components in Lake-Breeze Circulations: High Resolution Air Quality Modelling Results from the BAQS-Met Study  

NASA Astrophysics Data System (ADS)

The Border Air Quality and Meteorology Study (BAQS-Met 2007) was an opportunity to collect a dense network of measurements from aircraft, mobile platforms, mesonet stations and supersites in a coastal polluted environment. During the study, air masses sampled were influenced by local and regional emission sources. Important local emissions include the Detroit/Windsor urban area and point source industries along Lake Huron, Lake St Clair and Lake Erie. The proximity of the emissions to the Great Lakes provides the opportunity for chemical processing to be modified by the lake-breeze circulation. This unique data set provided the possibility to evaluate high resolution air quality modelling predictions using Environment Canada's unified regional air quality modelling system (AURAMS). The modelling domains have a nested configuration with grid spacings of 42, 15 and 2.5 km. The focus of this study is on the evaluation of the model against observations for specific case studies involving a lake breeze frontal passage. Of particular interest is an evaluation of the model performance for secondary aerosol components under conditions unique to the lake-breeze circulation (e.g. higher relative humidities, lower mixing heights, potential for cloud interactions, convergence and divergence zones). Measured sulfate, nitrate, ammonium and measurement- derived factors such as the oxygenated organic aerosol (OOA) components and hydrocarbon-like organic aerosol component (HOA) will be compared with modelled inorganics, secondary organic aerosol and primary organic aerosol.

Stroud, C.; Makar, P.; Gong, W.; Zhang, J.; Brook, J.; Hayden, K.; Sills, D.; Murphy, J.; Evans, G.; McLaren, R.

2008-12-01

121

Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst.  

PubMed

Particle growth by the heterogeneous reaction of aldehydes was evaluated in 0.5 m3 Teflon film bags under darkness in the presence of background seed aerosols. The aldehydes used were as follows: 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. These results were 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 scanning mobility particle sizer (TSI-SMPS), 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 inthe 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, and 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. PMID:11775150

Jang, M; Kamens, R M

2001-12-15

122

Effect of OH radical scavengers on secondary organic aerosol formation from reactions of isoprene with ozone  

NASA Astrophysics Data System (ADS)

In order to understand the effect of OH radical scavengers on secondary organic aerosol formation, aerosol yields from the isoprene ozonolysis were measured in the presence of sufficient amounts of OH radical scavengers. Cyclohexane, CO, n-hexane, and diethyl ether were used as the OH radical scavengers. The aerosol yield was determined to be 0.002-0.023 for experiments without OH radical scavengers in the aerosol mass range 2-120 ?g m-3. Similar aerosol yields were observed in experiments using cyclohexane. The aerosol yield observed with n-hexane was close to that observed without scavengers at 120 ?g m-3, but this aerosol yield was slightly lower than those observed in reactions without scavengers in the range 3-83 ?g m-3. The offline aerosol samples obtained in experiments with cyclohexane or n-hexane contained oxygenated hydrocarbons with six or more carbon atoms. Aerosol formation in experiments that used cyclohexane or n-hexane as the scavenger was enhanced. This was caused by the oxidation products of the OH radical scavengers, although the increase in the yield could not be quantified. The aerosol yields were 0.002-0.014 for experiments with CO and diethyl ether in the aerosol mass range 4-120 ?g m-3. The reaction of CO with OH radicals forms HO2 radicals, whereas the reactions of cyclohexane, n-hexane, and diethyl ether, respectively, with OH radicals form organic peroxy (RO2) radicals. Present results show that the aerosol yield is independent of the HO2/RO2 ratio or that it decreases with increasing HO2/RO2 ratio. Since the HO2 concentration is much higher than the RO2 concentration in the atmosphere, the results obtained using CO in this study will be a good approximation of the aerosol yield from the ozonolysis of isoprene in the atmosphere.

Sato, Kei; Inomata, Satoshi; Xing, Jia-Hua; Imamura, Takashi; Uchida, Risa; Fukuda, Sayaka; Nakagawa, Kazumichi; Hirokawa, Jun; Okumura, Motonori; Tohno, Susumu

2013-11-01

123

Parameterising secondary organic aerosol from ?-pinene using a detailed oxidation and aerosol formation model  

NASA Astrophysics Data System (ADS)

A new parameter model for ?-pinene secondary organic aerosol (SOA) is presented, based on simulations with the detailed model BOREAM (Biogenic hydrocarbon Oxidation and Related Aerosol formation Model). The parameterisation takes into account the influence of temperature, type of oxidant, NOx-regime, photochemical ageing and water uptake, and is suitable for use in global chemistry transport models. BOREAM is validated against recent photooxidation smog chamber experiments, for which it reproduces SOA yields to within a factor of 2 in most cases. In the simple chemical mechanism of the parameter model, oxidation of ?-pinene generates peroxy radicals, which, upon reaction with NO or HO2, yield products corresponding to high or low-NOx conditions, respectively. The model parameters - i.e. the temperature-dependent stoichiometric coefficients and partitioning coefficients of 10 semi-volatile products - are obtained from simulations with BOREAM, including a prescribed diurnal cycle for the radiation, oxidant and emission levels, as well as a deposition sink for the particulate and gaseous products. The effects of photooxidative ageing are implicitly included in the parameterisation, since it is based on near-equilibrium SOA concentrations, obtained through simulations of a two-week period. In order to mimic the full BOREAM model results both during SOA build-up and when SOA has reached an equilibrium concentration, the revolatilisation of condensable products due to photochemical processes is taken into account through a fitted pseudo-photolysis reaction of the lumped semi-volatile products. Modelled SOA mass yields are about ten times higher in low-NOx than in high-NOx conditions, with yields of more than 50% in the low-NOx OH-initiated oxidation of ?-pinene, considerably more than in previous parameterisations based on smog chamber experiments. Sensitivity calculations indicate that discrepancies between the full model and the parameterisation due to variations in assumed oxidant levels are limited, but that changes in the radiation levels can lead to larger deviations. Photolysis of species in the particulate phase is found to strongly reduce SOA yields in the full model. Simulations of ambient conditions at 17 different sites (using oxidant, radiation and meteorological data from a global chemistry-transport model) show that overall, the parameterisation displays only little bias (2%) compared with the full model, whereas averaged relative deviations amount to about 11%. Water uptake is parameterised using fitted activity coefficients, resulting in a good agreement with the full model.

Ceulemans, K.; Compernolle, S.; Müller, J.-F.

2012-06-01

124

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

125

Photolytic processing of secondary organic aerosols dissolved in cloud droplets.  

PubMed

The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n??* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ?0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest that biogenic SOA dissolved in cloud and fog droplets will undergo significant photolytic processing on a time scale of hours to days. This type of photolytic processing may account for the discrepancy between the higher values of O/C measured in the field experiments relative to the laboratory measurements on SOA in smog chambers. In addition, the direct photolysis of oligomeric compounds may be responsible for the scarcity of their observation in the field. PMID:21617794

Bateman, Adam P; Nizkorodov, Sergey A; Laskin, Julia; Laskin, Alexander

2011-05-26

126

Modeling of secondary organic aerosols formation during MILAGRO 2006  

NASA Astrophysics Data System (ADS)

The MILAGRO field campaign took place in March 2006 with the aim of gaining a better understanding of the evolution of trace gases and particulate matter emitted in Mexico City. During MILAGRO, a wide range of meteorological, chemical and particulate measurements were performed over local, regional and large-scale domains, all of which makes MILAGRO the most complete study of a tropical megacity’s atmosphere to date. Measurements of secondary organic aerosols (SOA) performed during MILAGRO cannot be explained by traditional SOA models. For example, Kleinman et al. (ACP 2008) reported model vs. measurement discrepancy of about an order of magnitude higher measured SOA than expected from aromatic oxidation using MILAGRO aircraft data. Likewise, Hodzic et al. (ACPD 2009) and Tsimpidi et al. (ACPD 2009) reported model vs. measurement discrepancies of the same order when using traditional SOA models inside two different regional models over Mexico City. Dzepina et al. (ACP 2009) recently showed that the inclusion of several newly proposed SOA formation mechanisms can close the gap in SOA mass between measurements and models for the case study during MCMA-2003 field campaign. Here we apply the same model as in Dzepina et al. (ACP 2009) to model the evolution of organic gases and particles advected from downtown Mexico City at an altitude of ~3.5 km during three days of aging and dilution. Traditional SOA model products, mainly from the oxidation of aromatics, cannot explain the observed OA/?CO ratios in aged pollution. However, over the regional scale there is a significant contribution of low-NOx aromatic pathway (Ng et al., ACP 2009) that has a very high SOA yield and forms non-volatile SOA which in the model always remains in the particle phase as dilution proceeds and semi-volatiles evaporate. The non-traditional SOA model (Robinson et al., Science 2007) still produces the most SOA model mass, although its mass fraction of total SOA decreases during aging. We also characterize the volatility and O/C ratio of model SOA mass after one, two and three days of aging, and compare it to the MILAGRO measurements. Finally, we explore the behavior of the SOA model mass upon rapid lifting to the upper troposphere during convection.

Dzepina, K.; Hodzic, A.; Madronich, S.; Zaveri, R. A.; Volkamer, R.; Cappa, C. D.; Jimenez, J. L.

2009-12-01

127

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

128

Determination of isoprene-derived secondary organic aerosol tracers (2-methyltetrols) by HPAEC-PAD: Results from size-resolved aerosols in a tropical rainforest  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formed from oxidation of isoprene, the most abundant nonmethane hydrocarbon in the atmosphere, has been estimated to contribute significantly to the global aerosol burden. Measurement of isoprene-derived SOA molecular markers has become an effective method for the investigation of biogenic aerosol contributions in the atmosphere. The primary goals of this work are to present a new method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) to quantify diastereoisomeric 2-methyltetrols (2-methylerythritol and 2-methylthreitol), marker compounds of isoprene-derived SOA, and thus to obtain better understanding regarding their abundance and size distribution specifically in a rainforest area. The 2-methyltetrol data, along with water-soluble inorganic ion concentrations, were obtained from size-segregated samples collected at a tropical rainforest site in South China during the period from May to June, 2010. The concentrations of 2-methyltetrols from selected samples measured by HPAEC-PAD showed good agreement with those measured by GC/MS. Overall, the HPAEC-PAD method provides a simple and fast, yet selective and sensitive, alternative to GC/MS for 2-methyltetrol determination, allowing for more efficient analysis of large sample numbers. The size distributions of 2-methylerythritol and 2-methylthreitol both exhibited a unimodal pattern, peaking in the particle size range of 0.44-1.0 ?m, where their average concentrations were 11.7 and 4.2 ng m?3, respectively. A strong correlation between 2-methylerythritol and 2-methylthreitol was observed among the entire set of size-segregated samples, indicating their photochemical origin and similar formation mechanism regardless of particle sizes. Compared to the results obtained from previous chamber studies, the similar isomeric fraction of 2-methyltetrols obtained in this study and other field studies confirms their formation through photooxidation of isoprene.

Zhang, Zhi-Sheng; Engling, Guenter; Chan, Chuen-Yu; Yang, Yi-Hong; Lin, Mang; Shi, Si; He, Jun; Li, Yi-De; Wang, Xue-Mei

2013-05-01

129

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

130

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

NASA Astrophysics Data System (ADS)

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 both biomass burning and secondary photochemical production (e.g. terpene oxidations) are contributing to the overall carbonaceous aerosols in the optically active region of 0.1 to 1.0 micron. Samples in this size range collected on quartz fiber filters were also examined using an integrating sphere and FTIR diffuse reflectance techniques to obtain absorption spectra from 280 to the mid-IR. These data clearly indicate that the biogenic derived primary aerosols from agricultural and trash-burning, as well as secondary organic aerosols from isoprene and terpene oxidations will produce both UV-Visible (short-wave) absorbing substances as well as IR (long-wave) absorbing compounds including humic-like-substances (HULIS). With the anticipated increases in growing seasons (i.e. earlier springs and longer summers) the likely hood of increased fires (forest and grassland) as well as the continuing growth in agricultural burning activities, these primary sources are expected to increase and may play a role in heating of the atmosphere. The compound effects of these primary and secondary biogenic sources of absorbing aerosols to the total aerosol loading and regional climate will be discussed. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328 as part of the Atmospheric Science Program.

Gaffney, J. S.; Marley, N. A.

2008-12-01

131

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

Microsoft Academic Search

Many recent models underpredict secondary organic aerosol (SOA) particulate matter (PM) concentrations in polluted regions, indicating serious deficiencies in the models' chemical mechanisms and\\/or missing SOA precursors. Since tropospheric photochemical ozone production is much better understood, we investigate the correlation of odd-oxygen ([Ox]?[O3]+[NO2]) and the oxygenated component of organic aerosol (OOA), which is interpreted as a surrogate for SOA. OOA

E. C. Wood; M. R. Canagaratna; S. C. Herndon; J. H. Kroll; T. B. Onasch; C. E. Kolb; D. R. Worsnop; W. B. Knighton; R. Seila; M. Zavala; L. T. Molina; P. F. Decarlo; J. L. Jimenez; A. J. Weinheimer; D. J. Knapp; B. T. Jobson; J. Stutz; W. C. Kuster; E. J. Williams

2010-01-01

132

Secondary Organic Aerosol formation from the gas-phase ozonolysis of 3-methylcatechol and 4-methylcatechol  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosol (SOA) formation during the ozonolysis of 3-methylcatechol (3-methyl-1,2-dihydroxybenzene) and 4-methylcatechol (3-methyl-1,2-dihydroxybenzene) was investigated using a simulation chamber (8 m3) at atmospheric pressure, room temperature (294 ± 2 K) and low relative humidity (5-10%). The initial mixing ratios were as follows (in ppb): 3-methylcatechol (194-1059), 4-methylcatechol (204-1188) and ozone (93-531). The ozone and methylcatechol concentrations were followed by UV photometry and GC-FID (Gas Chromatography - Flame ionization detector), respectively and the aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer). The SOA yields (Y) were determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted methylcatechol concentrations assuming a particle density of 1.4 g cm-3. The aerosol formation yield increases as the initial methylcatechol concentration increases, and leads to aerosol yields ranging from 32% to 67% and from 30% to 64% for 3-methylcatechol and 4-methylcatechol, respectively. Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. These data are comparable to those published in a recent study on secondary organic aerosol formation from catechol ozonolysis. To our knowledge, this work represents the first investigation of SOA formation from the ozone reaction with methylcatechols.

Coeur-Tourneur, Cécile; Foulon, Valentine; Laréal, Michel; Cassez, Andy; Zhao, Weixiong

2010-05-01

133

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

134

Real-time, controlled OH-initiated oxidation of biogenic secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The chemical complexity of atmospheric organic aerosol (OA) requires novel methods for characterization of its components and description of its atmospheric processing-induced transformations. We present the first field deployment of the Toronto Photooxidation Tube (TPOT), a field-deployable flow reactor for the controlled exposure of ambient aerosol to OH radicals. The system alternates between sampling of (1) (unreacted) ambient aerosol, (2) aerosol exposed to UV light and subjected to a ~4 to 10 °C temperature increase, and (3) aerosol that is oxidized by OH (in addition to the aforementioned UV exposure/temperature increase). This allows both characterization of the aging process and classification of aerosol in terms of its volatility and reaction-based properties. Summertime measurements by an aerosol mass spectrometer coupled to the TPOT were performed in the remote forest of western Canada, resulting in aerosol dominated by biogenic secondary organic aerosol. Volatilization/UV exposure resulted in an approximately 10 to 25% decrease in organic mass and resulted in a slight increase in oxygenation. OH oxidation resulted in a further organic mass decrease (additional ~25%) and yielded an aerosol with O:C values comparable to those characteristic of low volatility, highly oxygenated OA. Most OH-induced changes occurred within ~3 day-equivalents of atmospheric processing, with further reactions generally proceeding at a greatly reduced rate. Positive matrix factorization (PMF) analysis of the TPOT data yielded five factors. One factor is related to primary biomass burning organic aerosol, while the others describe oxygenated organic aerosol (OOA) components in terms of reactivity and volatility: (1) volatile and reactive; (2) non-volatile and reactive; (3) non-volatile and reactive early-generation product; (4) non-volatile and non-reactive product. This PMF classification of aerosol components directly in terms of reactivity and volatility is enabled by the TPOT-modulated perturbation of aerosol composition, and is not otherwise accessible. The particle-phase reaction end products have mass spectra similar to the low-volatility oxygenated organic aerosol (LV-OOA) factors widely reported in the literature, providing supporting evidence for aged organic aerosol formation from OH-driven oxidation processes.

Slowik, J. G.; Wong, J. P. S.; Abbatt, J. P. D.

2012-10-01

135

Field Study of Filter Sampling Artifacts for Inorganic and Organic Aerosol Species  

NASA Astrophysics Data System (ADS)

It is well-known that the collection of carbonaceous aerosols on quartz fibre filters is prone to both positive and negative artifacts (e.g., Turpin et al., 2000). In studies on these artifacts, one normally concentrates on organic carbon (OC) as a whole or occasionally on water-soluble OC (WSOC). It is rare that studies are carried on individual organic species. Examples of the latter type of study are those by Limbeck et al. (2001; 2005), who used a low-volume tandem filter set-up at a rural background site in South Africa and at the urban site Vienna in Austria, and measured dicarboxylic acids (DCAs) on the front and back filters. We conducted a similar study as those of Limbeck et al. (2001; 2005). For our study we collected high-volume PM2.5 samples during summer field campaigns at three European forested sites, i.e., in Hungary, Belgium, and Finland. The front and back filters of our samples were analysed for OC with a thermal-optical transmission technique (Birch & Cary, 1996), for WSOC as described by Viana et al. (2006), and for water-soluble inorganic cationic and anionic species and organic anionic species by suppressed ion chromatography with conductometric detection. The organic species measured included methanesulphonic acid (MSA) and the four major DCAs, i.e., oxalic, malonic, succinic, and glutaric. The median back/front percentage ratios for ammonium and sulphate were low, below 5% and 1%, respectively, but for nitrate they were around 25-30%. That undenuded filter samplings for nitrate are prone to artifacts is well-documented (e.g., Schaap et al., 2004). For OC the median back/front percentage ratios were around 15% and for WSOC around 20%. For MSA and the four DCAs, they increased in the following order: oxalic (1.5%), succinic (3%), MSA (4%), malonic (2-9%), glutaric (7-26%). Our back/front ratios for three of the four DCAs are lower to much lower than these found by Limbeck et al. (2001; 2005); for malonic, however, we found higher back/front ratios. There were a number of differences between the sampling conditions in the earlier studies and ours; the collection time per sample was one week in Limbeck et al. (2001) and 36 h in Limbeck et al. (2005), but only 12 h in our study; besides, the sampling face velocity was substantially larger in our study; on the other hand, in both the earlier studies and ours, use was made of pre-fired Pallfex 2500 QAT-UP quartz fibre filters. It is clear that results from one site and sampler cannot be generalised to all sites and sampler types and perhaps also not to other quartz fibre filter types or to non-fired filters. Birch, M. E., & Cary, R. A. (1996). Aerosol Sci. Technol. 25, 221-241. Limbeck, A., Puxbaum, H., Otter, L., & Scholes, M. C. (2001). Atmos. Environ. 35, 1853-1862. Limbeck, A., Kraxner, Y. & Puxbaum, H. (2005). J. Aerosol Sci. 36, 991-1005. Schaap, M., et al. (2004). Atmos. Environ. 38, 6487-6496. Turpin, B. J., Saxena, P., & Andrews, E. (2000). Atmos. Environ. 34, 2983-3013. Viana, M., et al. (2006). Atmos. Environ. 40, 2180-2193.

Maenhaut, W.; Wang, W.; Chi, X.

2009-12-01

136

Volatility of secondary organic aerosol during OH radical induced ageing  

NASA Astrophysics Data System (ADS)

The aim of this study was to investigate oxidation of SOA formed from ozonolysis of ?-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 of KIT in Karlsruhe and at the SAPHIR chamber of FZJ in Jülich. A fresh SOA was produced from ozonolysis of ?-pinene or limonene and then aged by enhanced OH exposure. As an OH-radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of ?-pinene and limonene initially were rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the ?-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi- or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing processing.

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

2011-07-01

137

Volatility of secondary organic aerosol during OH radical induced ageing  

NASA Astrophysics Data System (ADS)

The aim of this study was to investigate oxidation of SOA formed from ozonolysis of ?-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 of Karlsruhe Institute of Technology (KIT) in Karlsruhe and at the SAPHIR chamber of Forchungzentrum Jülich (FZJ) in Jülich. A fresh SOA was produced from ozonolysis of ?-pinene or limonene and then aged by enhanced OH exposure. As an OH radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of ?-pinene and limonene initially was rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the ?-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi- or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing.

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

2011-11-01

138

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

139

Oligomer formation within secondary organic aerosol: equilibrium and dynamic considerations  

NASA Astrophysics Data System (ADS)

We present a model based on the volatility basis set to consider the potential influence of oligomer content on volatility-driven SOA yields. The implications for aerosol evaporation studies, including dilution, chamber thermo-equilibration, and thermodenuder studies are also considered. A simplified description of oligomer formation reproduces essentially all of the broad classes of equilibrium and dynamical observations related to SOA formation and evaporation: significant oligomer content may be consistent with mass yields that increase with organic aerosol mass concentration; reversible oligomerization can explain the hysteresis between the rate of SOA formation and its evaporation rate upon dilution; and the model is consistent with both chamber thermo-equilibration studies and thermodenuder studies of SOA evaporation.

Trump, E. R.; Donahue, N. M.

2013-09-01

140

Source Apportionment of Primary and Secondary Organic Aerosols in Southern California during the 2005 Study of Organic Aerosols in Riverside (SOAR1)  

Microsoft Academic Search

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

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

2009-01-01

141

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

142

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

PubMed

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

2012-10-22

143

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.

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

144

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

145

Modeling of size-distributed secondary aerosols associated with petrochemical plant emissions  

Microsoft Academic Search

The particulate load (PM10) in the Los Angeles basin exceeds the standards and has to be reduced. A large fraction of the PM10 is secondary, i.e., formed in the atmosphere in smog reactions. The formation of secondary aerosols is simulated using a comprehensive numerical model. The model is trajectory-type and includes dispersion, emissions, deposition and chemistry. Both gas phase and

Dragoescu

1988-01-01

146

The impact of building recirculation rates on secondary organic aerosols generated by indoor chemistry  

Microsoft Academic Search

Numerous investigators have documented increases in the concentrations of airborne particles as a consequence of ozone\\/terpene reactions in indoor environments. This study examines the effect of building recirculation rates on the concentrations of secondary organic aerosol (SOA) resulting from reactions between indoor limonene and ozone. The experiments were conducted in a large environmental chamber using four recirculation rates (11, 14,

M. S. Zuraimi; C. J. Weschler; K. W. Tham; M. O. Fadeyi

2007-01-01

147

SOURCE APPORTIONMENT OF PRIMARY AND SECONDARY CARBONACEOUS AEROSOL IN THE UNITED STATES USING MODELS AND MEASUREMENTS  

EPA Science Inventory

In this presentation, three diagnostic evaluation methods of model performance for carbonaceous aerosol are reviewed. The EC-tracer method is used to distinguish primary and secondary carbon, radiocarbon data are used to distinguish fossil-fuel and contemporary carbon, and organ...

148

Investigating the Formation of Ambient Secondary Organic Aerosol in Southeastern USA  

Microsoft Academic Search

It is well known that during periods of intense photochemistry the formation of secondary organic aerosol (SOA) is a major source for fine particle mass, and a significant contributor to poor air quality. This process is thought to be especially important in the southeastern United States due to high concentrations of both anthropogenic and biogenic precursor organic compounds. SOA formation,

R. Weber; A. Sullivan; R. Peltier; C. Hennigan; B. Yan; M. Zheng; B. Kaynak; J. Russell; C. Brock; J. de Gouw; C. Warneke; J. Holloway; E. Atlas; E. Edgerton

2006-01-01

149

Modeling secondary organic aerosol formation from oxidation of ?-pinene, ?-pinene, and d-limonene  

Microsoft Academic Search

The biogenic species ?-pinene, ?-pinene, and d-limonene are among the most abundant monoterpenes emitted globally. They are also important precursors to secondary organic aerosol (SOA) formation in the atmosphere. This study involves the development of proposed oxidation mechanisms for these three species. Semi- and non-volatile oxidation products with the potential to lead to SOA formation are predicted explicitly. Simulation code

Jianjun Chen; Robert J. Griffin

2005-01-01

150

A missing sink for gas-phase glyoxal in Mexico City: Formation of secondary organic aerosol  

Microsoft Academic Search

The sources of secondary organic aerosol (SOA) are highly uncertain. Direct measurements of gas-phase glyoxal in Mexico City are compared to experimentally constrained model predictions. Observed glyoxal concentrations are found significantly below those predicted. Additional glyoxal sources are likely and would increase these differences; an additional glyoxal sink must be operative. The model-measurement differences are fully resolved by a sink

Rainer Volkamer; Federico San Martini; Luisa T. Molina; Dara Salcedo; Jose L. Jimenez; Mario J. Molina

2007-01-01

151

A missing sink for gas-phase glyoxal in Mexico City: Formation of secondary organic aerosol  

Microsoft Academic Search

(1) The sources of secondary organic aerosol (SOA) are highly uncertain. Direct measurements of gas-phase glyoxal in Mexico City are compared to experimentally constrained model predictions. Observed glyoxal concentrations are found significantly below those predicted. Additional glyoxal sources are likely and would increase these differences; an additional glyoxal sink must be operative. The model-measurement differences are fully resolved by a

Rainer Volkamer; Federico San Martini; Luisa T. Molina; Dara Salcedo; Jose L. Jimenez; Mario J. Molina

2007-01-01

152

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

Microsoft Academic Search

Limonene is one of the most abundant monoterpenes in the atmosphere. Limonene easily reacts with gas-phase oxidants in air such as NO3, ozone and OH. Secondary organic aerosol (SOA) is formed when low vapor pressure products condense into particles. Chemicals in SOA particles can undergo further reactions with oxidants and with solar radiation that significantly change SOA composition over the

Xiang Pan

2009-01-01

153

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

154

Laser ablation and static secondary ion mass spectrometry capabilities in the characterization of inorganic materials  

NASA Astrophysics Data System (ADS)

Recently, mass spectrometry techniques such as laser ablation and static secondary ion mass spectrometry (LA-MS and s-SIMS, respectively) have been successfully applied to the characterization of inorganic compounds in solid state phase: s-SIMS is known as a surface analytical technique whereas LA-MS involves atoms in a greater thickness (bulk). In the case of s-SIMS, the direct ejection of ions from the surface upon primary ion sputtering for ion fluence down to 10 13 ions/cm 2, leads to a simple and direct diagnostic by comparing the spectra to databases. On the opposite, characterization of inorganic compounds by means of LA-MS is not immediate due to the most detected ions are issued from complex gas phase reactions. This feature can be successfully applied to investigate matter transfer processes occurring during pulsed-laser deposition (PLD) experiments. By the mean of a systematic and comparative study of LA-MS and s-SIMS spectra for binary (Cu-O) or ternary (Fe-Cr-O) oxide systems, we demonstrate that both techniques are complementary to each other in the field of material science.

Aubriet, Frédéric; Poleunis, Claude; Chaoui, Nouari; Maunit, Beno??t; Millon, Eric; Muller, Jean-François; Bertrand, Patrick

2002-01-01

155

Contribution of Organic Vapors to the Growth of Secondary Aerosols  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

156

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

157

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

160

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation  

NASA Astrophysics Data System (ADS)

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Waxman, E.; Slowik, J.; Kampf, C.; Timkovsky, J.; Noziere, B.; Praplan, A.; Pffafenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A.; Baltensperger, U.; Volkamer, R.

2012-04-01

161

Secondary Organic Aerosol Formation from Glyoxal: photochemical versus dark uptake and reversible versus irreversible SOA formation  

NASA Astrophysics Data System (ADS)

Glyoxal forms secondary organic aerosol (SOA) by partitioning to the aerosol aqueous phase according to Henry's law. The subsequent processing by heterogeneous and multiphase reactions shifts the partitioning towards aerosols. Currently it is not well understood whether these reactions result in reversible or irreversible SOA formation, and what parameters influence the rate limiting step of multiphase processing. We conducted a series of simulation chamber experiments at PSI in April and May 2011 to investigate processing under dark conditions, UV and/or visible light irradiated conditions, and in the presence and absence of OH radicals. Experiments used ammonium sulfate or ammonium sulfate/fulvic acid mixtures as seed aerosols, and were conducted between 50% and 85% relative humidity at approximately constant RH over the course of any given experiment. Glyoxal was produced photochemically from acetylene, using HONO photolysis as the OH radical source. Gas-phase glyoxal was measured by the CU LED-Cavity Enhanced-DOAS. The Thermal-Desorption Proton-Transfer-Reaction Mass Spectrometer (TD-PTR-MS) and Ion Chromatography Mass Spectrometer (IC-MS) monitored both gas and aerosol-phase organic reaction products. Particle composition was monitored by High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS), and HPLC-ESI MS/MS and LC-MS analysis of filter samples.

Waxman, E.; Slowik, J. G.; Kampf, C. J.; Timkovsky, J.; Noziere, B.; Praplan, A. P.; Pfaffenberger, L.; Holzinger, R.; Hoffmann, T.; Dommen, J.; Prevot, A. S.; Baltensperger, U.; Volkamer, R.

2011-12-01

162

Mitigating secondary aerosol generation potentials from biofuel use in the energy sector.  

PubMed

This paper demonstrates secondary aerosol generation potential of biofuel use in the energy sector from the photochemical interactions of precursor gases on a life cycle basis. The paper is divided into two parts-first, employing life cycle analysis (LCA) to evaluate the extent of the problem for a typical biofuel based electricity production system using five baseline scenarios; second, proposing adequate mitigation options to minimise the secondary aerosol generation potential on a life cycle basis. The baseline scenarios cover representative technologies for 2010 utilising energy crop (miscanthus), short rotation coppiced chips and residual/waste wood in different proportions. The proposed mitigation options include three approaches-biomass gasification prior to combustion, delaying the harvest of biomass, and increasing the geographical distance between the biomass plant and the harvest site (by importing the biofuels). Preliminary results indicate that the baseline scenarios (assuming all the biomass is sourced locally) bear significant secondary aerosol formation potential on a life cycle basis from photochemical neutralisation of acidic emissions (hydrogen chloride and sulphur dioxide) with ammonia. Our results suggest that gasification of miscanthus biomass would provide the best option by minimising the acidic emissions from the combustion plant whereas the other two options of delaying the harvest or importing biofuels from elsewhere would only lead to marginal reduction in the life cycle aerosol loadings of the systems. PMID:19878969

Tiwary, Abhishek; Colls, Jeremy

2009-10-29

163

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.

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; Mohler, Ottmar; Leisner, Thomas; Muller, 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; Prevot, Andre S.H.; Baltensperger, Urs

2012-01-01

164

Markers of heterogeneous reaction products in ?-pinene ozone secondary organic aerosol  

NASA Astrophysics Data System (ADS)

A gas chromatograph iontrap mass spectrometer (GC-ITMS) was used to analyze the gas-and particle-phase products of ?-pinene ozone oxidation in the presence of three different inorganic seed aerosols: sodium chloride, ammonium sulfate only, and ammonium sulfate with sulfuric acid. Products of ?-pinene ozone oxidation common to the literature showed little difference in gas or particle-phase concentrations between seed types within the precision of the measurements even though significantly different aerosol yields were found between seed types. Small amounts of ring-opening products of four-membered cyclic oxygenates and markers of aldol condensation products were tentatively identified in the particle-phase for all seed types. These tentatively identified products are thought to be the result of acid-catalyzed heterogeneous reactions in the particle-phase or during sampling processes or analysis. The mechanisms for their formation are also proposed in this study.

Czoschke, Nadine M.; Jang, Myoseon

165

FORMATION MECHANISMS FOR SECONDARY ORGANIC AEROSOL IN AMBIENT AIR  

EPA Science Inventory

An laboratory and field research program is underway at the NERL to characterize secondary organic carbon in PM2.5 which is formed through chemical reactions in the atmosphere. Information from this study will provide critical data needed to improve the treatment of SO...

166

Characterization of secondary organic aerosol particles using aerosol laser time-of-flight mass spectrometer coupled with FCM clustering algorithm  

NASA Astrophysics Data System (ADS)

Experiments for formation of secondary organic aerosol (SOA) from photooxidation of 1,3,5-trimethylbenzene in the CH3ONO/NO/air mixture were carried out in the laboratory chamber. The size and chemical composition of the resultant individual particles were measured in real-time by an aerosol laser time of flight mass spectrometer (ALTOFMS) recently designed in our group. We also developed Fuzzy C-Means (FCM) algorithm to classify the mass spectra of large numbers of SOA particles. The study first started with mixed particles generated from the standards benzaldehyde, phenol, benzoic acid, and nitrobenzene solutions to test the feasibility of application of the FCM. The FCM was then used to extract out potential aerosol classes in the chamber experiments. The results demonstrate that FCM allowed a clear identification of ten distinct chemical particle classes in this study, namely, 3,5-dimethylbenzoic acid, 3,5-dimethylbenzaldehyde, 2,4,6-trimethyl-5-nitrophenol, 2-methyl-4-oxo-2-pentenal, 2,4,6-trimethylphenol, 3,5-dimethyl-2-furanone, glyoxal, and high-molecular-weight (HMW) components. Compared to offline method such as gas chromatography-mass spectrometry (GC-MS) measurement, the real-time ALTOFMS detection approach coupled with the FCM data processing algorithm can make cluster analysis of SOA successfully and provide more information of products. Thus ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chambers.

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

2013-01-01

167

Secondary Organic Aerosol Formation from the Photooxidation of p- and o-Xylene  

SciTech Connect

The formation of secondary organic aerosol (SOA) from the photooxidation of xylene isomers (m-, p-, and o-xylenes) has been extensively investigated. The dependence of SOA aerosol formation on the structure of xylene isomers in the presence of NO was confirmed. Generally, SOA formation of p-xylene was less than that ofm- and o-xylenes. This discrepancy varies significantly with initial NOx levels. In a NOx-free environment, the difference of aerosol formation between o- and p-xylenes becomes insignificant. Several chemical pathways for the SOA dependence on structure and NOx are explored, with the experimental findings indicating that organic peroxides may be a major key to explaining SOA formation from aromatic hydrocarbons.

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

2007-11-01

168

Modeling the role of alkanes, polycyclic aromatic hydrocarbons, and their oligomers in secondary organic aerosol formation.  

PubMed

A computationally efficient method to treat secondary organic aerosol (SOA) from various length and structure alkanes as well as SOA from polycyclic aromatic hydrocarbons (PAHs) is implemented in the Community Multiscale Air Quality (CMAQ) model to predict aerosol concentrations over the United States. Oxidation of alkanes is predicted to produce more aerosol than oxidation of PAHs driven by relatively higher alkane emissions. SOA from alkanes and PAHs, although small in magnitude, can be a substantial fraction of the SOA from anthropogenic hydrocarbons, particularly in winter, and could contribute more if emission inventories lack intermediate volatility alkanes (>C(13)) or if the vehicle fleet shifts toward diesel-powered vehicles. The SOA produced from oxidation of alkanes correlates well with ozone and odd oxygen in many locations, but the lower correlation of anthropogenic oligomers with odd oxygen indicates that models may need additional photochemically dependent pathways to low-volatility SOA. PMID:22568386

Pye, Havala O T; Pouliot, George A

2012-05-08

169

Temperature dependence of yields of secondary organic aerosols from the ozonolysis of alpha-pinene and limonene  

Microsoft Academic Search

Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humidity for the ozone-initiated reaction of the two monoterpenes alpha-pinene (243-313 K) and limonene (253-313 K) using the 84.5 m3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parameters specifically useful for aerosol yield calculations. The ozonolysis reaction, selected oxidation

H. Saathoff; K.-H. Naumann; O. Möhler; Â. M. Jonsson; M. Hallquist; A. Kiendler-Scharr; Th. F. Mentel; R. Tillmann; U. Schurath

2009-01-01

170

Temperature dependence of yields of secondary organic aerosols from the ozonolysis of alpha-pinene and limonene  

Microsoft Academic Search

Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humidity for the ozone-initiated reaction of the two monoterpenes alpha-pinene (243 313 K) and limonene (253 313 K) using the 84.5 m3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parameters specifically useful for aerosol yield calculations. The ozonolysis reaction,

H. Saathoff; K.-H. Naumann; O. Möhler; Ã. M. Jonsson; M. Hallquist; A. Kiendler-Scharr; Th. F. Mentel; R. Tillmann; U. Schurath

2008-01-01

171

Glyoxal-methylglyoxal cross-reactions in secondary organic aerosol formation.  

PubMed

Glyoxal (G) and methylglyoxal (MG) are potentially important secondary organic aerosol (SOA) precursors. Previous studies of SOA formation by G and MG have focused on either species separately; however, G and MG typically coexist in the atmosphere. We studied the formation of secondary organic material in aqueous aerosol mimic mixtures containing G and MG with ammonium sulfate. We characterized the formation of light-absorbing products using UV-vis spectrophotometry. We found that absorption at 280 nm can be described well using models for the formation of light-absorbing products by G and MG in parallel. Pendant drop tensiometry measurements showed that surface tension depression by G and MG in these solutions can be modeled as a linear combination of the effects of G and MG alone. Product species were identified using chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol CIMS). Peaks consistent with G-MG cross-reaction products were observed, accounting for a significant fraction of detected product mass, but most peaks could be attributed to self-reaction. We conclude that cross-reactions contribute to SOA mass from uptake of G and MG, but they are not required to accurately model the effects of this process on aerosol surface tension or light absorption. PMID:20704215

Schwier, Allison N; Sareen, Neha; Mitroo, Dhruv; Shapiro, Erica L; McNeill, V Faye

2010-08-15

172

Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber  

NASA Astrophysics Data System (ADS)

The evolution of secondary organic aerosols (SOA) during (photo-)chemical aging processes was investigated in a smog chamber. Fresh SOA from ozonolysis of 10 to 40 ppb ?-pinene was formed followed by aging with OH radicals. The particles' volatility and hygroscopicity (expressed as volume fraction remaining (VFR) and hygroscopicity parameter ?) were measured in parallel with a volatility and hygroscopicity tandem differential mobility analyzer (V/H-TDMA). An aerosol mass spectrometer (AMS) was used for the chemical characterization of the aerosol. These measurements were used as sensitive parameters to reveal the mechanisms possibly responsible for the changes in the SOA composition during aging. A change of VFR and/or ? during processing of atmospheric aerosols may occur either by addition of SOA mass (by condensation) or by a change of SOA composition leading to different aerosol properties. The latter may occur either by heterogeneous reactions on the surface of the SOA particles, by condensed phase reactions like oligomerization or by an evaporation - gas-phase oxidation - recondensation cycle. The condensation mechanism showed to be dominant when there is a substantial change in the aerosol mass by addition of new molecules to the aerosol phase with time. Experiments could be divided into four periods based on the temporal evolution (qualitative changes) of VFR, ? and organic mass: O3 induced condensation, ripening, and OH induced chemical aging first with substantial mass gain and then without significant mass gain. During the O3 induced condensation the particles' volatility decreased (increasing VFR) while the hygroscopicity increased. Thereafter, in the course of ripening volatility continued to decrease, but hygroscopicity stayed roughly constant. After exposing the SOA to OH radicals an OH induced chemical aging with substantial mass gain started resulting in the production of at least 50 % more SOA mass. This new SOA mass was highly volatile and oxidized. This period was then followed by further OH induced chemical aging without significant mass gain leading to a decrease of volatility while hygroscopicity and SOA mass stayed roughly constant.

Tritscher, T.; Dommen, J.; Decarlo, P. F.; Gysel, M.; Barmet, P. B.; Praplan, A. P.; Weingartner, E.; Prévôt, A. S. H.; Riipinen, I.; Donahue, N. M.; Baltensperger, U.

2011-11-01

173

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

174

Dicarboxylic acids, metals and isotopic compositions of C and N in atmospheric aerosols from inland China: implications for dust and coal burning emission and secondary aerosol formation  

NASA Astrophysics Data System (ADS)

Dicarboxylic acids (C2-C10), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C2) was the dominant diacid, followed by succinic (C4) and malonic (C3) acids. Total diacids in the urban and suburban areas are 1546±203 and 1728±495 ng m-3 during winter and 1236±335 and 1028±193 ng m-3 during spring. EC in the urban and the suburban atmospheres are 17±3.8 and 8.0±2.1 ?g m-3 during winter and 20±5.9 and 7.1±2.7 ?g m-3 during spring whereas OC at the urban and suburban sites are 74±14 and 51±7.9 ?g m-3 in winter and 51±20 and 23±6.1 ?g m-3 in spring. Secondary organic carbon (SOC) accounted for 38±16% of OC in winter and 28±18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring are 34±10 and 61±27 ?g m-3 in the urban air and 18±7 and 32±23 ?g m-3 in the suburban air. A linear correlation (r2>0.8 in winter and r2>0.6 in spring) was found between primary organic carbon (POC) and Ca2+/Fe, together with a strong dependence of pH value on water-soluble inorganic carbon, suggesting fugitive dust as a major source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the samples well correlated each other (r2>0.6) in winter samples, suggesting an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (?13C) became higher with an increase in the concentration ratios of C2/OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (?15N) became lower with an increases in the mass ratios of NH4+/PM10 and NO3-/PM10 due to an enhanced adsorption and/or condensation of NH3 and HNO3 from gas phase onto solid phase.

Wang, G.; Xie, M.; Hu, S.; Tachibana, E.; Kawamura, K.

2010-03-01

175

Dicarboxylic acids, metals and isotopic compositions of C and N in atmospheric aerosols from inland China: implications for dust and coal burning emission and secondary aerosol formation  

NASA Astrophysics Data System (ADS)

Dicarboxylic acids (C2-C10), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C2) was the dominant diacid, followed by succinic (C4) and malonic (C3) acids. Total diacids in the urban and suburban areas were 1546±203 and 1728±495 ng m-3 during winter and 1236±335 and 1028±193 ng m-3 during spring. EC in the urban and the suburban atmospheres were 17±3.8 and 8.0±2.1 ?g m-3 during winter and 20±5.9 and 7.1±2.7 ?g m-3 during spring, while OC at the urban and suburban sites were 74±14 and 51±7.9 ?g m-3 in winter and 51±20 and 23±6.1 ?g m-3 in spring. Secondary organic carbon (SOC) accounted for 38±16% of OC in winter and 28±18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring were 34±10 and 61±27 ?g m-3 in the urban air and 18±7 and 32±23 ?g m-3 in the suburban air. A linear correlation (r2>0.8 in winter and r2>0.6 in spring) was found between primary organic carbon (POC) and Ca2+/Fe, together with a strong dependence of pH value of sample extracts on water-soluble inorganic carbon, suggesting fugitive dust as an important source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the samples well correlated each other (r2>0.6) in winter, indicating an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (?13C) became higher with an increase in the concentration ratios of C2/OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (?15N) became lower with an increases in the mass ratios of NH4+/PM10 and NO3-/PM10, which is possibly caused by an enhanced adsorption and/or condensation of gaseous NH3 and HNO3 onto particles.

Wang, G.; Xie, M.; Hu, S.; Gao, S.; Tachibana, E.; Kawamura, K.

2010-07-01

176

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

177

Evidence for a significant proportion of Secondary Organic Aerosol from isoprene above a maritime tropical forest  

NASA Astrophysics Data System (ADS)

Isoprene is the most abundant non-methane biogenic volatile organic compound (BVOC), but the processes governing secondary organic aerosol (SOA) formation from isoprene oxidation are only beginning to become understood and selective quantification of the atmospheric particulate burden remains difficult. Organic aerosol above a tropical rainforest located in Danum Valley, Borneo, Malaysia, a high isoprene emission region, was studied during Summer 2008 using Aerosol Mass Spectrometry and offline detailed characterisation using comprehensive two dimensional gas chromatography. Observations indicate that a substantial fraction (up to 15% by mass) of atmospheric sub-micron organic aerosol was observed as methylfuran (MF) after thermal desorption. This observation was associated with the simultaneous measurements of established gas-phase isoprene oxidation products methylvinylketone (MVK) and methacrolein (MACR). Observations of MF were also made during experimental chamber oxidation of isoprene. Positive matrix factorisation of the AMS organic mass spectral time series produced a robust factor which accounts for an average of 23% (0.18 ?g m-3), reaching as much as 53% (0.50 ?g m-3) of the total oraganic loading, identified by (and highly correlated with) a strong MF signal. Assuming that this factor is generally representative of isoprene SOA, isoprene derived aerosol plays a significant role in the region. Comparisons with measurements from other studies suggest this type of isoprene SOA plays a role in other isoprene dominated environments, albeit with varying significance.

Robinson, N. H.; Hamilton, J. F.; Allan, J. D.; Langford, B.; Oram, D. E.; Chen, Q.; Docherty, K.; Farmer, D. K.; Jimenez, J. L.; Ward, M. W.; Hewitt, C. N.; Barley, M. H.; Jenkin, M. E.; Rickard, A. R.; Martin, S. T.; McFiggans, G.; Coe, H.

2011-02-01

178

Evidence for a significant proportion of Secondary Organic Aerosol from isoprene above a maritime tropical forest  

NASA Astrophysics Data System (ADS)

Isoprene is the most abundant non-methane biogenic volatile organic compound (BVOC), but the processes governing secondary organic aerosol (SOA) formation from isoprene oxidation are only beginning to become understood and selective quantification of the atmospheric particulate burden remains difficult. Organic aerosol above a tropical rainforest located in Danum Valley, Borneo, Malaysia, a high isoprene emission region, was studied during Summer 2008 using Aerosol Mass Spectrometry and offline detailed characterisation using comprehensive two dimensional gas chromatography. Observations indicate that a substantial fraction (up to 15% by mass) of atmospheric sub-micron organic aerosol was observed as methylfuran (MF) after thermal desorption. This observation was associated with the simultaneous measurements of established gas-phase isoprene oxidation products methylvinylketone (MVK) and methacrolein (MACR). Observations of MF were also made during experimental chamber oxidation of isoprene. Positive matrix factorisation of the AMS organic mass spectral time series produced a robust factor which accounts for an average of 23% (0.18 ?g m-3), reaching as much as 53% (0.50 ?g m-3) of the total oraganic loading, identified by (and highly correlated with) a strong MF signal. Assuming that this factor is generally representative of isoprene SOA, isoprene derived aerosol plays a significant role in the region. Comparisons with measurements from other studies suggest this type of isoprene SOA plays a role in other isoprene dominated environments, albeit with varying significance.

Robinson, N. H.; Hamilton, J. F.; Allan, J. D.; Langford, B.; Oram, D. E.; Chen, Q.; Docherty, K.; Farmer, D. K.; Jimenez, J. L.; Ward, M. W.; Hewitt, C. N.; Barley, M. H.; Jenkin, M. E.; Rickard, A. R.; Martin, S. T.; McFiggans, G.; Coe, H.

2010-11-01

179

Aerosol Coupling in the Earths System (ACES): Linking Chemical Composition of Secondary Organic Aerosol to Hygroscopic Properties.  

NASA Astrophysics Data System (ADS)

The formation of secondary organic aerosol from the oxidation of reactive biogenic emissions is thought to be an important factor in global climate regulation. Biogenic Secondary Organic Aerosol (BSOA) can contribute to indirect radiative forcing by acting as cloud condensation nuclei. The potential of particles to act as CCN depends on their composition and hygroscopic properties. Sesquiterpenes, such as beta-caryophyllene, have been proposed as SOA precursors due to their low volatility and highly reactive nature. One of the main problems with using smog chamber simulations to study SOA formation and properties is the need to use high concentrations of reactive organic species. This can result in higher SOA yields and a different composition than in the real atmosphere. As part of the Aerosol coupling in the Earth System (ACES) project, a series of novel experiments were carried out at the Manchester Aerosol Chamber. By using a high volume pump and a collapsible chamber, the entire contents of the chamber can be sampled rapidly onto a filter. Recent improvements in the sensitivity of analytical techniques have allowed us to use lower VOC precursor concentrations (20 ppb) than previous studies. Repetitive experiments were carried out and filter samples taken at different experiment times, 2, 4 and 6 hours, allowing the evolution of individual SOA components to be evaluated. Complementary proton transfer mass spectrometry was used to study the evolution of gas phase oxidation products. The composition of beta-caryophyllene SOA was studied using liquid chromatography coupled to mass spectrometry. Twelve components were identified based on MS2 fragmentation patterns. The SOA composition was found to be much simpler than seen for monoterpenes and no oligomers were found. Experiments at 42 ppb and 210 ppb, indicate that the distribution of products varied depending on the starting VOC concentration. Low concentrations resulted in a higher proportion of more polar species such as nor-caryophyllenic acid (172 g mol-1), indicating the importance of carrying out smog chamber studies as close to ambient concentrations as possible. Results obtained using an Aerodyne aerosol mass spectrometer showed that SOA formed using lower initial precursor concentration contained a higher fraction of m/z 44 (a typical marker for highly oxygenated organic molecules) compared to SOA produced using high precursor concentration. Ageing resulted in an increasingly complex OVOC profile compared to the simpler, early generation products, seen in the initial stages of the experiment. The hygroscopic properties of the beta-caryophyllene SOA were investigated using a hygroscopicity tandem differential mobility analyser (HTDMA) and a CCN counter. The evolution of the hygroscopic growth factor and the CCN activity were compared to the aerosol composition, giving an insight into how the oxidation processes altered the ability of the aerosol to take up water.

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

2008-12-01

180

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

2012-07-09

181

Temperature dependence of secondary organic aerosol formation by photo-oxidation of hydrocarbons  

Microsoft Academic Search

Photo-oxidation experiments on hydrocarbons were performed with a temperature-controlled smog chamber to study the temperature dependence of secondary organic aerosol (SOA) formation. A higher SOA yield was obtained at lower temperature and with a higher concentration of SOA generated. The relationship of SOA yield to temperature and SOA concentration is expressed by a gas\\/particle partitioning absorption model considered with temperature

Hideto Takekawa; Hiroaki Minoura; Satoshi Yamazaki

2003-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

183

Temperature and humidity dependence of secondary organic aerosol yield from the ozonolysis of ?-pinene  

Microsoft Academic Search

The temperature dependence of secondary organic aerosol (SOA) formation from ozonolysis of -pinene was studied in a flow reactor at 263 K-303 K and 1007 hPa un- der dry and humid conditions (0% and 26%-68% relative humidity, respectively). The observed SOA yields reached maximum values of 0.18-0.39 at high particle mass concen- trations (Mo). Under dry conditions, the measurement data

C. von Hessberg; P. von Hessberg; U. Pöschl; M. Bilde; O. J. Nielsen; G. K. Moortgat

2009-01-01

184

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

Microsoft Academic Search

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 198L chamber at steady rates. Consistently, at the time of ozone introduction, nucleation occurred exhibiting similar behavior to atmospheric events. The initial

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

2008-01-01

185

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

Microsoft Academic Search

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

B. Demirdjian; M. J. Rossi

2002-01-01

186

High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene  

Microsoft Academic Search

Chemical composition of secondary organic aerosol (SOA) formed from the ozone-initiated oxidation of limonene is characterized by high-resolution electrospray ionization mass spectrometry in both positive and negative ion modes. The mass spectra reveal a large number of both monomeric (m\\/z o 300) and oligomeric (m\\/z 4 300) condensed products of oxidation. A combination of high resolving power (m\\/Dm B 60

Maggie L. Walser; Yury Dessiaterik; Julia Laskin; Alexander Laskin; Sergey A. Nizkorodov

2008-01-01

187

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

188

Analysis of secondary organic aerosol formation and aging using positive matrix factorization of high-resolution aerosol mass spectra: application to the dodecane low-NOx system  

NASA Astrophysics Data System (ADS)

Positive matrix factorization (PMF) of high-resolution laboratory aerosol mass spectra is applied for the first time, the results of which are consistent with molecular level MOVI-HRToF-CIMS aerosol-phase and CIMS gas-phase measurements. Secondary organic aerosol was generated by photooxidation of dodecane under low-NOx conditions in the Caltech environmental chamber. The PMF results exhibit three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition. The slope of the measured high-resolution aerosol mass spectrometer (HR-ToF-AMS) composition data on a Van Krevelen diagram is consistent with that of other low-NOx alkane systems in the same O:C range. Elemental analysis of the PMF factor mass spectral profiles elucidates the combinations of functionality that contribute to the slope on the Van Krevelen diagram.

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

2012-07-01

189

Analysis of secondary organic aerosol formation and aging using positive matrix factorization of high-resolution aerosol mass spectra: application to the dodecane low-NOx system  

NASA Astrophysics Data System (ADS)

Positive matrix factorization (PMF) of high-resolution laboratory chamber aerosol mass spectra is applied for the first time, the results of which are consistent with molecular level MOVI-HRToF-CIMS aerosol-phase and CIMS gas-phase measurements. Secondary organic aerosol was generated by photooxidation of dodecane under low-NOx conditions in the Caltech environmental chamber. The PMF results exhibit three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition. The slope of the measured high-resolution aerosol mass spectrometer (HR-ToF-AMS) composition data on a Van Krevelen diagram is consistent with that of other low-NOx alkane systems in the same O : C range. Elemental analysis of the PMF factor mass spectral profiles elucidates the combinations of functionality that contribute to the slope on the Van Krevelen diagram.

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

2012-12-01

190

Aerosol and Inorganic Gaseous Iodine at Appledore Island, Maine During Summers 2004, 2005 and 2006  

Microsoft Academic Search

Iodine chemistry may affect the ozone budget in the marine atmosphere and has been hypothesized to play an important role in aerosol nucleation and\\/or growth in surface air, particularly in coastal regions where marine macrophytes are a prolific source of organoiodine gases. Total iodine was determined by neutron activation analysis in: 1) daytime and nighttime samples of bulk and size

A. Pszenny; K. Cotter; B. Deegan; E. Fischer; R. Griffin; D. Johnson; W. Keene; J. Maben; T. Seidel; A. Smith; L. Ziemba

2006-01-01

191

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

192

Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The study investigates the sources of fine organic aerosol (OA) in the boreal forest, based on measurements including both filter sampling (PM1) and online methods and carried out during a one-month campaign held in Hyytiälä, Finland, in spring 2007. Two aerosol mass spectrometers (Q-AMS, ToF-AMS) were employed to measure on-line concentrations of major non-refractory aerosol species, while the water extracts of the filter samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy for organic functional group characterization of the polar organic fraction of the aerosol. AMS and NMR spectra were processed separately by non-negative factorization algorithms, in order to apportion the main components underlying the submicrometer organic aerosol composition and depict them in terms of both mass fragmentation patterns and functional group compositions. The NMR results supported the AMS speciation of oxidized organic aerosol (OOA) into two main fractions, which could be generally labelled as more and less oxidized organics. The more oxidized component was characterized by a mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR spectrum showing aromatic and aliphatic backbones highly substituted with oxygenated functional groups (carbonyls/carboxyls and hydroxyls). Such component, contributing on average 50% of the OA mass throughout the observing period, was associated with pollution outbreaks from the Central Europe. The less oxidized component was enhanced in concomitance with air masses originating from the North-to-West sector, in agreement with previous investigations conducted at this site. NMR factor analysis was able to separate two distinct components under the less oxidized fraction of OA. One of these NMR-factors was associated with the formation of terrestrial biogenic secondary organic aerosol (BSOA), based on the comparison with spectral profiles obtained from laboratory experiments of terpenes photo-oxidation. The second NMR factor associated with western air masses was linked to biogenic marine sources, and was enriched in low-molecular weight aliphatic amines. Such findings provide evidence of at least two independent sources originating biogenic organic aerosols in Hyytiälä by oxidation and condensation mechanisms: reactive terpenes emitted by the boreal forest and compounds of marine origin, with the latter relatively more important when predominantly polar air masses reach the site. This study is an example of how spectroscopic techniques, such as proton NMR, can add functional group specificity for certain chemical features (like aromatics) of OA with respect to AMS. They can therefore be profitably exploited to complement aerosol mass spectrometric measurements in organic source apportionment studies.

Finessi, E.; Decesari, S.; Paglione, M.; Giulianelli, L.; Carbone, C.; Gilardoni, S.; Fuzzi, S.; Saarikoski, S.; Raatikainen, T.; Hillamo, R.; Allan, J.; Mentel, Th. F.; Tiitta, P.; Laaksonen, A.; Petäjä, T.; Kulmala, M.; Worsnop, D. R.; Facchini, M. C.

2012-01-01

193

Stable carbon isotope composition of secondary organic aerosol from ?-pinene oxidation  

NASA Astrophysics Data System (ADS)

A chamber study was carried out to investigate the stable carbon isotopic composition (?13C) of secondary organic aerosol (SOA) formed from ozonolysis of ?-pinene. ?-Pinene (600 ppb) with a known ?13C value (-30.1‰) and 500 ppb ozone were injected into the chamber in the absence of light and the resulting SOA was collected on preheated quartz fiber filters. Furthermore, ?13C values of the gas-phase ?-pinene and one of its oxidation products, nopinone, were measured using a gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS). ?-Pinene was progressively enriched with the heavy carbon isotope due to the kinetic isotope effect (KIE). The KIE of the reaction of ?-pinene with ozone was measured to be 1.0026 ? 2.6 ± 1.5‰). The ?13C value of total secondary organic aerosol was very similar to that of its precursor (average = -29.6 ± 0.2‰) independent of experiment time. Nopinone, one of the major oxidation products of ?-pinene, was found in both the gas and aerosol phases. The gas-phase nopinone was heavier than the initial ?-pinene by 1.3‰ but lighter than the corresponding aerosol-phase nopinone. On average, the gas-phase nopinone was lighter by 2.3‰ than the corresponding aerosol-phase nopinone. The second product found in the SOA was detected as acetone, but it desorbed from the filter at a higher temperature than nopinone, which indicates that it is a pyrolysis product. The acetone showed a much lower ?13C (-36.6‰) compared to the initial ?-pinene ?13C.

Fisseha, Rebeka; Spahn, Holger; Wegener, Robert; Hohaus, Thorsten; Brasse, Gregor; Wissel, Holger; Tillmann, Ralf; Wahner, Andreas; Koppmann, Ralf; Kiendler-Scharr, Astrid

2009-01-01

194

Influence of Soluble Surfactant Properties on the Activation of Aerosol Particles Containing Inorganic Solute.  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles consisting of ammonium sulfate [(NH4)2SO4] or sodium chloride (NaCl) have reasonably well-defined hygroscopic properties compared to other materials in aerosol particles, such as organic material. The effect of internally mixing organic compounds with these salts is not clear when considering the hygroscopic properties of the resulting particles, including activation of particles in clouds. This research describes the activation of aerosol particles consisting of sodium dodecyl sulfate (SDS) and NaCl solute. SDS is used as a surrogate for soluble atmospheric surfactants. Köhler theory is used to model droplet activation while considering droplet properties such as surface tension (), surface excess surfactant concentration, and critical micelle concentration (CMC).Reduction in critical supersaturation (Sc) caused by the reduction in (Kelvin effect) associated with the surfactant is dominated by the increase in Sc with the decreasing number of moles of solute in the droplet (Raoult effect) as surfactant displaces NaCl solute mass. For an initially dry 0.1-m diameter particle, Sc increases from 0.10 to 0.25 as NaCl solute mass changes from 100% (0% SDS solute) to 0% (100% SDS solute). Such dependence of cloud droplet activation on mixed solute composition is important when considering atmospheric chemistry and physics. The partitioning of materials between aerosol particles and cloud drops are influenced by mixing the surfactant with NaCl. Also, inhibition of droplet activation when displacing NaCl solute with a high molecular weight soluble surfactant could significantly influence the indirect effects aerosols have on climate change.

Li, Zhidong; Williams, Allen L.; Rood, Mark J.

1998-05-01

195

Modelling of organic aerosols over Europe (2002-2007) using a volatility basis set (VBS) framework: application of different assumptions regarding the formation of secondary organic aerosol  

NASA Astrophysics Data System (ADS)

A new organic aerosol module has been implemented into the EMEP chemical transport model. Four different volatility basis set (VBS) schemes have been tested in long-term simulations for Europe, covering the six years 2002-2007. Different assumptions regarding partitioning of primary organic aerosol and aging of primary semi-volatile and intermediate volatility organic carbon (S/IVOC) species and secondary organic aerosol (SOA) have been explored. Model results are compared to filter measurements, aerosol mass spectrometry (AMS) data and source apportionment studies, as well as to other model studies. The present study indicates that many different sources contribute significantly to organic aerosol in Europe. Biogenic and anthropogenic SOA, residential wood combustion and vegetation fire emissions may all contribute more than 10% each over substantial parts of Europe. This study shows smaller contributions from biogenic SOA to organic aerosol in Europe than earlier work, but relatively greater anthropogenic SOA. Simple VBS based organic aerosol models can give reasonably good results for summer conditions but more observational studies are needed to constrain the VBS parameterisations and to help improve emission inventories. The volatility distribution of primary emissions is one important issue for further work. Emissions of volatile organic compounds from biogenic sources are also highly uncertain and need further validation. We can not reproduce winter levels of organic aerosol in Europe, and there are many indications that the present emission inventories substantially underestimate emissions from residential wood combustion in large parts of Europe.

Bergström, R.; Denier van der Gon, H. A. C.; Prévôt, A. S. H.; Yttri, K. E.; Simpson, D.

2012-09-01

196

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

197

Secondary aerosol formation from the oxidation of biogenic hydrocarbons by chlorine atoms  

NASA Astrophysics Data System (ADS)

The chlorine atom (Cl) is a potential oxidant of volatile organic compounds (VOCs) in the atmosphere and is hypothesized to lead to secondary organic aerosol (SOA) formation in coastal and industrialized areas. The purpose of this paper is to test this hypothesis and to quantify the SOA formation potentials of the common monoterpenes ?-pinene, ?-pinene, and d-limonene when oxidized by Cl in laboratory chamber experiments. Results indicate that the oxidation of these monoterpenes generates significant amounts of aerosol. The SOA yields of ?-pinene, ?-pinene, and d-limonene in this study are comparable to those when they are oxidized by ozone, by nitrate radical, and in photooxidation scenarios. For aerosol mass up to 30.0 ?g m-3, their yields reach approximately 0.20, 0.20, and 0.30, respectively. For d-limonene, data indicate two yield curves that depend on the initial concentration ratio of Cl precursor to d-limonene. It is argued theoretically that multiple SOA yield curves may be common for VOCs, depending on the initial concentration ratio of oxidant to VOC. SOA formation from the three typical monoterpenes when oxidized by Cl in the marine boundary layer, coastal areas, and inland industrialized areas could be a source of organic aerosol in the early morning.

Cai, Xuyi; Griffin, Robert J.

2006-07-01

198

Cloud condensation nucleation activity of secondary organic aerosols formed from the oxidation of alkenes and diiodomethane  

NASA Astrophysics Data System (ADS)

Recent measurements have shown that marine aerosol contains a significant fraction of organic compounds. The sources for these compounds are not yet completely understood, but are thought to be a mix of primary emissions and secondary organic aerosol (SOA) formation. Reactive alkenes with low carbon numbers (C5 and C6) and halogenated hydrocarbons emitted from phytoplankton are commonly suggested precursors. These compounds can contribute to new particle formation events and can lead to subsequent growth into the accumulation mode size range. We conducted measurements of the cloud condensation nuclei (CCN) and ice nuclei activity of SOA that was formed from the oxidation of linear, branched, and cyclic alkenes, as well as from diiodomethane. Aerosol forming reactions were carried out in a PTFE environmental chamber, involving oxidation of the precursors mostly with O3 and, for a select number of precursors, oxidation with OH in the absence of NOx. We also performed experiments on single component aerosols generated from the atomization of aqueous solutions, targeting polyalcohols commonly associated with isoprene oxidation products. Ice nucleation experiments were performed only for the O3 reactions and ice nuclei were not observed in detectable quantities for this subset of systems. From our experiments we found that CCN activity generally decreases with the precursor carbon number. When expressed as hygroscopicity parameter (kappa), CCN activity ranged from kappa ~ 0.15 to kappa 0, spanning the range from moderately CCN active to CCN inactive at atmospherically relevant sizes and supersaturations, respectively.

Petters, M. D.; Faulhaber, A.; Prenni, A. J.; Carrico, C. M.; Sullivan, R. C.; Demott, P. J.; Kreidenweis, S. M.; Ziemann, P. J.

2009-12-01

199

Secondary aerosol formation from stress-induced biogenic emissions and possible climate feedbacks  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols impact climate by scattering and absorbing solar radiation and by acting as ice and cloud condensation nuclei. Biogenic secondary organic aerosols (BSOAs) comprise an important component of atmospheric aerosols. Biogenic volatile organic compounds (BVOCs) emitted by vegetation are the source of BSOAs. Pathogens and insect attacks, heat waves and droughts can induce stress to plants that may impact their BVOC emissions, and hence the yield and type of formed BSOAs, and possibly their climatic effects. This raises questions of whether stress-induced changes in BSOA formation may attenuate or amplify effects of climate change. In this study we assess the potential impact of stress-induced BVOC emissions on BSOA formation for tree species typical for mixed deciduous and Boreal Eurasian forests. We studied the photochemical BSOA formation for plants infested by aphids in a laboratory setup under well-controlled conditions and applied in addition heat and drought stress. The results indicate that stress conditions substantially modify BSOA formation and yield. Stress-induced emissions of sesquiterpenes, methyl salicylate, and C17-BVOCs increase BSOA yields. Mixtures including these compounds exhibit BSOA yields between 17 and 33%, significantly higher than mixtures containing mainly monoterpenes (4-6% yield). Green leaf volatiles suppress SOA formation, presumably by scavenging OH, similar to isoprene. By classifying emission types, stressors and BSOA formation potential, we discuss possible climatic feedbacks regarding aerosol effects. We conclude that stress situations for plants due to climate change should be considered in climate-vegetation feedback mechanisms.

Mentel, Th. F.; Kleist, E.; Andres, S.; Dal Maso, M.; Hohaus, T.; Kiendler-Scharr, A.; Rudich, Y.; Springer, M.; Tillmann, R.; Uerlings, R.; Wahner, A.; Wildt, J.

2013-09-01

200

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

SciTech Connect

The meso-scale chemistry-transport model CHIMERE is used to assess our understanding of major sources and formation processes leading to a fairly large amount of organic aerosols [OA, including primary OA (POA) and secondary OA (SOA)] observed in Mexico City during the MILAGRO field project (March 2006). Chemical analyses of submicron aerosols from aerosol mass spectrometers (AMS) indicate that organic particles found in the Mexico City basin have a large fraction of oxygenated organic species (OOA), which have strong correspondence with SOA, and that their production actively continues downwind of the city. The SOA formation is modeled here by the first-generation oxidation of anthropogenic (i.e., aromatics, alkanes) and biogenic (i.e., monoterpenes and isoprene) precursors and their partitioning into both organic and aqueous phases. The near-surface model evaluation shows that predicted OA correlates reasonably well with measurements during the campaign, however it remains a factor of 2 lower than the measured total OA. Fairly good agreement is found between predicted and observed POA within the city suggesting that anthropogenic and biomass burning emissions are reasonably captured. Consistent with previous studies in Mexico City, large discrepancies are encountered for SOA species, with a factor of 5-10 model underestimate. When only anthropogenic SOA precursors were considered, the model was able to reproduce within a factor of two the sharp increase in SOA concentrations during the late morning at both urban and near-urban locations. However, predicted SOA concentrations were unrealistically low when photochemistry was not active, especially overnight. These nighttime discrepancies were not significantly reduced when greatly enhanced partitioning to the aerosol phase was assumed. Model sensitivity results suggest that observed nighttime SOA concentrations are strongly influenced by the regional background (~2µg/m3) from biogenic origin, which is transported from the coastal regions into the Mexico City basin. The relative contribution of biogenic SOA to monthly mean SOA levels is estimated to be more than 30% within the city and up to 65-90% at the regional scale (even in the immediate vicinity of the city), which is consistent with measurements of modern carbon during low biomass burning periods. The anthropogenic emissions of isoprene and its nighttime oxidation by NO3 were also found to enhance the SOA mean concentrations within the city by an additional 15%. Our results confirm the large underestimation of the SOA production by traditional models in polluted regions (estimated to 10-20 Tons within the Mexico City metropolitan area during the daytime), and emphasize for the first time the role of biogenic precursors in this region, indicating that they cannot be neglected in modeling studies.

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

2009-09-22

201

Secondary Aerosol Formation from Oxidation of Aromatics Hydrocarbons by Cl atoms  

NASA Astrophysics Data System (ADS)

Aerosol Formation From the Oxidation of Aromatic Hydrocarbons by Chlorine Atmospheric secondary organic aerosol (SOA) affects regional and global air quality. The formation mechanisms of SOA via the oxidation of volatile organic compounds by hydroxyl radicals, ozone, and nitrate radicals have been studied intensively during the last decade. Chlorine atoms (Cl) also have been hypothesized to be effective oxidants in marine and industrially influenced areas. Recent work by the authors has indicated that significant amounts of SOA are formed from the oxidation of monoterpenes by Cl. Aromatic hydrocarbons are important for generation of both SOA and ozone in urban areas because of their large emission rates and high reactivity. The goal of this work was to quantify the SOA formation potentials of two representative aromatic hydrocarbons through laboratory chamber experiments in which oxidation was initiated by Cl. The system constructed for this study includes an experimental chamber, a gas chromatograph for quantification of aromatic mixing ratios, a Scanning Mobility Particle Spectrometer to measure SOA size distributions, a zero air generator, and an illuminating system. The model aromatic hydrocarbons chosen for this study are toluene and m-xylene. Aerosol yields are estimated based on measured aerosol volume concentration, the concentration of consumed hydrocarbon, and estimation of wall loss of the newly formed aerosol. Toluene and m-xylene exhibit similar SOA yields from the oxidation initiated by Cl. The toluene SOA yield from Cl-initiated oxidation, however, depends on the ratio between the mixing ratios of the initial chlorine source and toluene in the chamber. For toluene experiments with higher such ratios, SOA yields vary from 0.05 to 0.079 for generated aerosol ranging from 4.2 to12.0 micrograms per cubic meter. In the lower ratio experiments, SOA yields are from 0.033 to 0.064, corresponding to generated aerosol from 3.0 to 11.0 micrograms per cubic meter. The m-xylene SOA yield ranges from 0.04 to 0.08 for aerosol in the range of 4.0 to 12.0 micrograms per cubic meter. These yields are generally comparable to those from photooxidation. In marine and industrial areas, SOA formation from the Cl- initiated oxidation of the studied common aromatics is likely to be most important in the early morning.

Cai, X.; Griffin, R.

2006-12-01

202

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

203

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

PubMed Central

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

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

2013-01-01

204

Biogenic potassium salt particles as seeds for secondary organic aerosol in the Amazon.  

PubMed

The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest. PMID:22936773

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

2012-08-31

205

Gasoline emissions dominate over diesel in formation of secondary organic aerosol mass  

NASA Astrophysics Data System (ADS)

Although laboratory experiments have shown that organic compounds in both gasoline fuel and diesel engine exhaust can form secondary organic aerosol (SOA), the fractional contribution from gasoline and diesel exhaust emissions to ambient SOA in urban environments is poorly known. Here we use airborne and ground-based measurements of organic aerosol (OA) in the Los Angeles (LA) Basin, California made during May and June 2010 to assess the amount of SOA formed from diesel emissions. Diesel emissions in the LA Basin vary between weekdays and weekends, with 54% lower diesel emissions on weekends. Despite this difference in source contributions, in air masses with similar degrees of photochemical processing, formation of OA is the same on weekends and weekdays, within the measurement uncertainties. This result indicates that the contribution from diesel emissions to SOA formation is zero within our uncertainties. Therefore, substantial reductions of SOA mass on local to global scales will be achieved by reducing gasoline vehicle emissions.

Bahreini, R.; Middlebrook, A. M.; de Gouw, J. A.; Warneke, C.; Trainer, M.; Brock, C. A.; Stark, H.; Brown, S. S.; Dube, W. P.; Gilman, J. B.; Hall, K.; Holloway, J. S.; Kuster, W. C.; Perring, A. E.; Prevot, A. S. H.; Schwarz, J. P.; Spackman, J. R.; Szidat, S.; Wagner, N. L.; Weber, R. J.; Zotter, P.; Parrish, D. D.

2012-03-01

206

Insights into the secondary fraction of the organic aerosol in a Mediterranean urban area: Marseille  

NASA Astrophysics Data System (ADS)

A comprehensive aerosol characterization was conducted at Marseille during summer, including organic (OC) and elemental carbon (EC), major ionic species, radiocarbon (14C), water-soluble OC and HULIS (HUmic LIke Substances), elemental composition and primary and secondary organic markers. This paper is the second paper of a two-part series that uses this dataset to investigate the sources of Organic Aerosol (OA). While the first paper investigates the primary sources (El Haddad et al., 2010), this second paper focuses on the secondary fraction of the organic aerosol. In the context of overall OC mass balance, primary OC (POC) contributes on average for only 22% and was dominated by vehicular emissions accounting on average for 17% of OC. As a result, 78% of OC mass cannot be attributed to the major primary sources and remains un-apportioned. Radiocarbon measurements suggest that more than 70% of this fraction is of non-fossil origin, assigned predominantly to biogenic secondary organic carbon (BSOC). Therefore, contributions from three traditional BSOC precursors, isoprene, alpha -pinene and ?-caryophyllene, were considered. These were estimated using the ambient concentrations of Secondary Organic Aerosol (SOA) markers from each precursor and laboratory-derived marker mass fraction factors. Secondary organic markers derived from isoprene photo-oxidation (ie: 2-methylglyceric acid and 2-methyltetrols) do not exhibit the same temporal trends. This variability was assigned to the influence of NOx concentration on their formation pathways and to their potential decay by further processing in the atmosphere. The influence of changes in isoprene chemistry on assessment of isoprene SOC contribution was evaluated explicitly. The results suggest a 60-fold variation between the different estimates computed using different isoprene SOC markers, implying that the available profiles do not reflect the actual isoprene SOC composition observed in Marseille. Using the marker-based approach, the aggregate contribution from traditional BSOC was estimated at only 4.2% of total OC and was dominated by ?-pinene SOC accounting on average for 3.4% of OC. As a result, these estimates underpredict the inexplicably high loadings of OC. This underestimation can be associated with (1) uncertainties underlying the marker-based approach, (2) presence of other SOC precursors and (3) further processing of fresh SOC, as indicated by organosulfates (RSO4H) and HUmic LIke Substances (HULIS) measurements.

El Haddad, I.; Marchand, N.; Temime-Roussel, B.; Wortham, H.; Piot, C.; Besombes, J.-L.; Baduel, C.; Voisin, D.; Armengaud, A.; Jaffrezo, J.-L.

2011-03-01

207

Temperature dependence of yields of secondary organic aerosols from the ozonolysis of ?-pinene and limonene  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humidity for the ozone-initiated reaction of the two monoterpenes ?-pinene (243 313 K) and limonene (253 313 K) using the 84.5 m3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parameters specifically useful for aerosol yield calculations. The ozonolysis reaction, selected oxidation products and subsequent aerosol formation were followed using several analytical techniques for both gas and condensed phase characterisation. The effective densities of the SOA were determined by comparing mass and volume size distributions to (1.25±0.10) g cm-3 for ?-pinene and (1.3±0.2) g cm-3 for limonene. The detailed aerosol dynamics code COSIMA-SOA proved to be essential for a comprehensive evaluation of the experimental results and for providing parameterisations directly applicable within atmospheric models. The COSIMA-assisted analysis succeeded to reproduce the observed time evolutions of SOA total mass, number and size distributions by adjusting the following properties of two oxidation product proxies: individual yield parameters (?i), partitioning coefficients (Ki), vapour pressures (pi) and effective accommodation coefficients (?i). For these properties temperature dependences were derived and parameterised. Vapour pressures and partitioning coefficients followed classical Clausius-Clapeyron temperature dependences. From this relationship enthalpies of vaporisation were derived for the two more and less volatile product proxies of ?-pinene: (59±8) kJ mol-1 and (24±9) kJ mol-1, and limonene: (55±14) kJ mol-1 and (25±12) kJ mol-1. The more volatile proxy components had a notably low enthalpy of vaporisation while the less volatile proxy components gave enthalpies of vaporisation comparable with those of typical products from ?-pinene oxidation, e.g. pinonaldehyde and pinonic acid.

Saathoff, H.; Naumann, K.-H.; Möhler, O.; Jonsson, Ã. M.; Hallquist, M.; Kiendler-Scharr, A.; Mentel, Th. F.; Tillmann, R.; Schurath, U.

2008-08-01

208

Temperature dependence of yields of secondary organic aerosols from the ozonolysis of ?-pinene and limonene  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation has been investigated as a function of temperature and humidity for the ozone-initiated reaction of the two monoterpenes ?-pinene (243-313 K) and limonene (253-313 K) using the 84.5 m3 aerosol chamber AIDA. This paper gives an overview of the measurements done and presents parameters specifically useful for aerosol yield calculations. The ozonolysis reaction, selected oxidation products and subsequent aerosol formation were followed using several analytical techniques for both gas and condensed phase characterisation. The effective densities of the SOA were determined by comparing mass and volume size distributions to (1.25±0.10) g cm-3 for ?-pinene and (1.3±0.2) g cm-3 for limonene. The detailed aerosol dynamics code COSIMA-SOA proved to be essential for a comprehensive evaluation of the experimental results and for providing parameterisations directly applicable within atmospheric models. The COSIMA-assisted analysis succeeded to reproduce the observed time evolutions of SOA total mass, number and size distributions by adjusting the following properties of two oxidation product proxies: individual yield parameters (?i), partitioning coefficients (Ki), vapour pressures (pi) and effective accommodation coefficients (?i). For these properties temperature dependences were derived and parameterised. Vapour pressures and partitioning coefficients followed classical Clausius - Clapeyron temperature dependences. From this relationship enthalpies of vaporisation were derived for the two more and less volatile product proxies of ?-pinene: (59±8) kJ mol-1 and (24±9) kJ mol-1, and limonene: (55±14) kJ mol-1 and (25±12) kJ mol-1. The more volatile proxy components had a notably low enthalpy of vaporisation while the less volatile proxy components gave enthalpies of vaporisation comparable with those of typical products from ?-pinene oxidation, e.g. pinonaldehyde and pinonic acid.

Saathoff, H.; Naumann, K.-H.; Möhler, O.; Jonsson, Â. M.; Hallquist, M.; Kiendler-Scharr, A.; Mentel, Th. F.; Tillmann, R.; Schurath, U.

2009-03-01

209

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

210

Apportionment of primary and secondary organic aerosols in southern California during the 2005 study of organic aerosols in riverside (SOAR-1).  

PubMed

Ambient sampling was conducted in Riverside, California during the 2005 Study of Organic Aerosols in Riverside to characterize the composition and sources of organic aerosol using a variety of state-of-the-art instrumentation and source apportionmenttechniques. 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 ofthese 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 midday periods, whereas minimum SOA contributions of approximately 45% were observed during peak morning traffic periods. These results are contraryto previous estimates of SOAthroughout 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 are discussed. PMID:18983089

Docherty, Kenneth S; Stone, Elizabeth A; Ulbrich, Ingrid M; DeCarlo, Peter F; Snyder, David C; Schauer, James J; Peltier, Richard E; Weber, Rodney J; Murphy, Shane M; Seinfeld, John H; Grover, Brett D; Eatough, Delbert J; Jimenez, Jose L

2008-10-15

211

Real-time continuous characterization of secondary organic aerosol derived from isoprene epoxydiols in downtown Atlanta, Georgia, using the Aerodyne Aerosol Chemical Speciation Monitor.  

PubMed

Real-time continuous chemical measurements of fine aerosol were made using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) during summer and fall 2011 in downtown Atlanta, Georgia. Organic mass spectra measured by the ACSM were analyzed by positive matrix factorization (PMF), yielding three conventional factors: hydrocarbon-like organic aerosol (HOA), semivolatile oxygenated organic aerosol (SV-OOA), and low-volatility oxygenated organic aerosol (LV-OOA). An additional OOA factor that contributed to 33 ± 10% of the organic mass was resolved in summer. This factor had a mass spectrum that strongly correlated (r(2) = 0.74) to that obtained from laboratory-generated secondary organic aerosol (SOA) derived from synthetic isoprene epoxydiols (IEPOX). Time series of this additional factor is also well correlated (r(2) = 0.59) with IEPOX-derived SOA tracers from filters collected in Atlanta but less correlated (r(2) < 0.3) with a methacrylic acid epoxide (MAE)-derived SOA tracer, ?-pinene SOA tracers, and a biomass burning tracer (i.e., levoglucosan), and primary emissions. Our analyses suggest IEPOX as the source of this additional factor, which has some correlation with aerosol acidity (r(2) = 0.3), measured as H(+) (nmol m(-3)), and sulfate mass loading (r(2) = 0.48), consistent with prior work showing that these two parameters promote heterogeneous chemistry of IEPOX to form SOA. PMID:23638946

Budisulistiorini, Sri Hapsari; Canagaratna, Manjula R; Croteau, Philip L; Marth, Wendy J; Baumann, Karsten; Edgerton, Eric S; Shaw, Stephanie L; Knipping, Eladio M; Worsnop, Douglas R; Jayne, John T; Gold, Avram; Surratt, Jason D

2013-05-21

212

Size distributions of dicarboxylic acids and inorganic ions in atmospheric aerosols collected during polar sunrise in the Canadian high Arctic  

NASA Astrophysics Data System (ADS)

Size-segregated atmospheric aerosols (11 stages separating particles from <0.04 to >14.2 ?m) collected in the Arctic during the polar sunrise at Alert were analyzed for aerosol mass, dicarboxylic acids, and major inorganic ions. Oxalic, malonic, succinic, and glutaric acids were detected in all size ranges, with oxalic acid being dominant. Their concentrations maximized in the accumulation mode either at 0.24-0.40 or 0.40-0.8 ?m aerodynamic diameters, suggesting that diacids were mainly formed by gas-to-particle conversion via photochemical oxidation of nonmethane hydrocarbons and oxygenated organics originated from continental pollution sources. The relative abundances of oxalic acid were higher in the 0.24- to 0.4-?m size particles (73-78%) than in supermicrometer particles (40-60%), indicating that oxalic acid is produced by gas phase oxidation of precursors followed by accumulation on preexisting particles. Mass size distributions of NH4+ and SO42- peaked in the accumulation mode similar to those of small diacids. The sea-salt enrichment factor of K+ (biomass burning tracer) relative to Na+ maximized in 0.1- to 0.8-?m sizes, whereas those of Mg2+ and Ca2+ (dust tracers) in 0.4- to 7.8-?m particles. Maximized chlorine loss and bromine enrichment were found at 0.4-0.8 and 0.24-0.4 ?m sizes, respectively. Concentrations of Br-, which typically showed a submicrometer maximum, increased significantly during an O3 depletion event having a shift of size distribution to a supermicrometer mode. During this event, oxalic acid concentration relative to succinic acid increased in submicrometer mode (0.24-0.4 ?m), adding to a growing body of evidence supporting the hypothesis that halogen chemistry is important in the production and loss of oxalic acid in the arctic atmosphere.

Kawamura, Kimitaka; Narukawa, Masahiro; Li, Shao-Meng; Barrie, Leonard A.

2007-05-01

213

Mass size distributions of water-soluble inorganic and organic ions in size-segregated aerosols over metropolitan Newark in the US east coast  

Microsoft Academic Search

To characterize the mass size distributions of water-soluble inorganic and organic ions associated with urban particulate matter, a total of 15 sets of size-segregated aerosol samples were collected by a 10-stage Micro-Orifice Uniform Deposit Impactor (MOUDI) in the urban area of Newark in New Jersey from July to December 2006. The mass concentrations of PM1.8 accounted for ?68% of the

Yunliang Zhao; Yuan Gao

2008-01-01

214

A method to quantify organic functional groups and inorganic compounds in ambient aerosols using attenuated total reflectance FTIR spectroscopy and multivariate chemometric techniques  

Microsoft Academic Search

An attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic technique and a multivariate calibration method were developed to quantify ambient aerosol organic functional groups and inorganic compounds. These methods were applied to size-resolved particulate matter samples collected in winter and summer of 2004 at three sites: a downtown Phoenix, Arizona location, a rural site near Phoenix, and an urban fringe site

Charity Coury; Ann M. Dillner

2008-01-01

215

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

216

Relating cloud condensation nuclei activity and oxidation level of ?-pinene secondary organic aerosols  

NASA Astrophysics Data System (ADS)

During a series of smog chamber experiments, the effects of chemical and photochemical aging on the ability of organic aerosols generated from ozonolysis of ?-pinene to act as cloud condensation nuclei (CCN) were investigated. In particular, the study focused on the relation between oxygenation and the CCN-derived single hygroscopicity parameter ? for different experimental conditions: varying precursor concentrations (10-40 ppb), different OH sources (photolysis of HONO either with or without the addition of NO or ozonolysis of tetramethylethylene), and exposure to light. Oxygenation was described by the contribution of the aerosol mass spectrometer (AMS) mass fragment m/z 44 to the total organic signal (f44) and the oxygen to carbon molar ratio (O/C), likewise determined with AMS. CCN activity, described by the hygroscopicity parameter ?, was determined with a CCN counter. It was found that f44 increases with decreasing precursor concentration and with chemical aging, whereas neither of these affects CCN activity. Overall, ? is largely independent of O/C in the range 0.3 < O/C < 0.6 (0.07 < f44 < 0.12), although an empirical unweighted least squares fit was determined: ? = (0.071 ± 0.02) · (O/C) + (0.0785 ± 0.009) for particles with diameter in the range 59-200 nm. Growth kinetics of activating secondary organic aerosols were found to be comparable to those of ammonium sulfate and were not influenced by chemical aging.

Frosch, M.; Bilde, M.; Decarlo, P. F.; JuráNyi, Z.; Tritscher, T.; Dommen, J.; Donahue, N. M.; Gysel, M.; Weingartner, E.; Baltensperger, U.

2011-11-01

217

The role of low volatile organics on secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

218

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

219

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

220

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

221

Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products  

NASA Astrophysics Data System (ADS)

The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs) by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS) solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS), and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. A hemiacetal sulfate ester was tentatively identified in the formaldehyde-AS system. Acetaldehyde depresses surface tension to 65(±2) dyn cm-1 in pure water and 62(±1) dyn cm-1 in AS solutions. Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9 % reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.

Li, Z.; Schwier, A. N.; Sareen, N.; McNeill, V. F.

2011-07-01

222

Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products  

NASA Astrophysics Data System (ADS)

The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs) by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS) solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS), and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. Acetaldehyde depresses surface tension to 65(±2) dyn cm-1 in pure water (a 10% surface tension reduction from that of pure water) and 62(±1) dyn cm-1 in AS solutions (a 20.6% reduction from that of a 3.1 M AS solution). Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9% reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.

Li, Z.; Schwier, A. N.; Sareen, N.; McNeill, V. F.

2011-11-01

223

[Characteristics of mass distributions of aerosol particle and its inorganic water-soluble ions in summer over a suburb farmland in Beijing].  

PubMed

Agricultural activity is one of the important sources of aerosol particle. To understand the mass distribution and sources of aerosol particle and its inorganic water-soluble ions in the suburb farmland of Beijing, particle samples were collected with a MOUDI cascade impactor in the summer of 2004 in a suburb vegetable field. The mass distributions of the particle and its inorganic water-soluble ions in the diameter range of 0.18 to approximately 18 microm were measured. The dominant ions in the fine particle were SO4(2-), NOS3(-) and NH4+. The association of day to day variation of the concentration of these ions with temperature, humidity and solar radiation suggests that they are formed by the reaction of NH3 released from the vegetable field with the acid species produced from photochemical reactions. K+ in the fine particle is likely from the vegetation emission and biomass burning. Ca2+, Mg2+, NO3(-) and SO4(2-) in the coarse particle are suggested to come from the mechanical process by which the soil particle entered the atmosphere, and from the reactions of the acid species at the surface of the soil particle. The results show that fertilizer and soil are possibly important factors determining the aerosol particle over the agricultural fields, and the vegetable fields in suburb Beijing could contribute significantly to the aerosol particle. PMID:16686174

Zhao, Peng; Zhu, Tong; Liang, Bao-sheng; Hu, Min; Kang, Ling; Gong, Ji-cheng

2006-02-01

224

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

2012-08-09

225

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

NASA Astrophysics Data System (ADS)

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 laboratory work, focusing on SOA formation via oxidation of the emissions of two dominant tree species from boreal forest area, Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies), by hydroxyl radical (OH) and ozone (O3). Oxidation of ?-pinene was also studied as a reference system. Tetramethylethylene (TME) and 2-butanol were added to control OH and O3 levels, thereby allowing SOA formation events to be categorised as resulting from either OH-dominated or O3-initiated chemistry. SOA mass yields from ?-pinene are consistent with previous studies while the yields from the real plant emissions are generally lower than that from ?-pinene, varying from 1.9% at an aerosol mass loading of 0.69 ?g m-3 to 13.6% at 32.8 ?g m-3. Mass yields from oxidation of real plant emissions are subject to the interactive effects of the molecular structures of plant emissions and their reaction chemistry with OH and O3, which lead to variations in condensable product volatility. SOA formation can be reproduced with a two-product gas-phase partitioning absorption model in spite of differences in the source of oxidant species and product volatility in the real plant emission experiments. Condensable products from OH-dominated chemistry showed a higher volatility than those from O3-initiated systems during aerosol growth stage. Particulate phase products became less volatile via aging process which continued after input gas-phase oxidants had been completely consumed.

Hao, L. Q.; Romakkaniemi, S.; Yli-Pirilä, P.; Joutsensaari, J.; Kortelainen, A.; Kroll, J. H.; Miettinen, P.; Vaattovaara, P.; Tiitta, P.; Jaatinen, A.; Kajos, M. K.; Holopainen, J. K.; Heijari, J.; Rinne, J.; Kulmala, M.; Worsnop, D. R.; Smith, J. N.; Laaksonen, A.

2010-11-01

226

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

NASA Astrophysics Data System (ADS)

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 laboratory work, focusing on SOA formation via oxidation of the emissions of two dominant tree species from boreal forest area, Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies), by hydroxyl radical (OH) and ozone (O3). Oxidation of ?-pinene was also studied as a reference system. Tetramethylethylene (TME) and 2-butanol were added to control OH and O3 levels, thereby allowing SOA formation events to be categorized as resulting from either OH-dominated or O3-initiated chemistry. SOA mass yields from ?-pinene are consistent with previous studies while the yields from the real plant emissions are generally lower than that from ?-pinene, varying from 1.9% at an aerosol mass loading of 0.69 ?g m-3 to 17.7% at 26.0 ?g m-3. Mass yields from oxidation of real plant emissions are subject to the interactive effects of the molecular structures of plant emissions and their reaction chemistry with OH and O3, which lead to variations in condensable product volatility. SOA formation can be reproduced with a two-product gas-phase partitioning absorption model in spite of differences in the source of oxidant species and product volatility in the real plant emission experiments. Condensable products from OH-dominated chemistry showed a higher volatility than those from O3-initiated systems during aerosol growth stage. Particulate phase products became less volatile via aging process which continued after input gas-phase oxidants had been completely consumed.

Hao, L. Q.; Romakkaniemi, S.; Yli-Pirilä, P.; Joutsensaari, J.; Kortelainen, A.; Kroll, J. H.; Miettinen, P.; Vaattovaara, P.; Tiitta, P.; Jaatinen, A.; Kajos, M. K.; Holopainen, J. K.; Heijari, J.; Rinne, J.; Kulmala, M.; Worsnop, D. R.; Smith, J. N.; Laaksonen, A.

2011-02-01

227

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

NASA Astrophysics Data System (ADS)

Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 ?m) 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 different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from ?-pinene. The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra showing Pearson's r values >0.94 for the correlations between the four different SOA types after five hours of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+ and CO2+, respectively, similarly to the relatively fresh semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The atomic O:C ratios were found to be in the range of 0.25-0.55 with no major increase during the first five hours of aging. On average, the diesel SOA showed the lowest O:C ratio followed by SOA from wood burning, ?-pinene and the scooter emissions. Grouping the fragment ions revealed that the SOA source with the highest O:C ratio had the largest fraction of small ions. The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended.

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

2012-02-01

228

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

NASA Astrophysics Data System (ADS)

Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 ?m) 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 different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from ?-pinene. The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra in the m/z range 12-250 showing Pearson's r values >0.94 for the correlations between the different SOA types after 5 h of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+ and CO2+, respectively, similarly to the relatively fresh semi-volatile oxidized OA (SV-OOA) observed in the ambient aerosol. The atomic O : C ratios were found to be in the range of 0.25-0.55 with no major increase during the first 5 h of aging. On average, the diesel SOA showed the lowest O : C ratio followed by SOA from wood burning, ?-pinene and the scooter emissions. Grouping the fragment ions based on their carbon number revealed that the SOA source with the highest O : C ratio had the largest fraction of small ions. Fragment ions containing up to 3 carbon atoms accounted for 66%, 68%, 72% and 76% of the organic spectrum of the SOA produced by the diesel car, wood burner, ?-pinene and the scooter, respectively. The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended.

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

2011-10-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

230

Simulation Chamber Investigations of Secondary Organic Aerosol Formation From Boreal Tree Emissions: Dependence on VOC Classes  

NASA Astrophysics Data System (ADS)

A considerable fraction of the organic aerosol component is of secondary origin, meaning it is formed through oxidation of volatile organic compounds (VOCs). Plant emissions, e.g. monoterpenes and sesquiterpenes, are a major source of VOCs in the troposphere. So far most laboratory and simulation chamber investigations on the potential to form secondary organic aerosols (SOA) from plant emissions focused on single VOCs such as a-pinene. In this study we investigated the formation and growth of SOA by ozonolysis and/or photo-oxidation of the VOCs emitted by several tree species such as spruce, pine and birch. The experiments were performed in the Plant chamber of the ICG-3 in Jülich under well defined conditions for the plant. VOC emissions were transferred to a reaction chamber which was operated as a continuously stirred tank reactor. SOA formation from the VOCs was initiated by an excess of ozone and OH radicals. The results are compared to a reference study with a-pinene as the only SOA precursor. Our results indicate that the general laboratory approach of studying the formation of SOA from single components can lead to a bias in both the mass yields and the mass spectral signatures observed. Plots of maximum SOA volumes versus the total amount of carbon fed into the reaction chamber led to approximately linear relationships. The intercepts of these plots were seen as threshold for SOA formation. It was observed that this threshold was lower for the mixture of VOCs emitted from spruce, pine, and birch than for a-pinene as single compound. We therefore conclude that the threshold for SOA formation from real plant mixtures may be much lower than the threshold obtained from laboratory experiments that were focussed on single VOCs. SOA formation from stress induced VOCs will be compared to non stress induced emissions. Possible feedbacks of climate change to VOC emissions and aerosol formation will be discussed based on our experimental observations.

Kiendler-Scharr, A.; Mentel, T. F.; Kleist, E.; Hohaus, T.; Mensah, A.; Spindler, C.; Tillmann, R.; Uerlings, R.; Dal Maso, M.; Rudich, Y.; Juergen, W.

2008-12-01

231

Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols  

NASA Astrophysics Data System (ADS)

Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of the phase diagram. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation. For simplified partitioning parametrizations, we suggest a modified definition of the effective saturation concentration, C*j, by including water and other inorganics in the absorbing phase. Such a C*j definition reduces the RH-dependency of the gas/particle partitioning of semivolatile organics in organic-inorganic aerosols by an order of magnitude as compared to the currently accepted definition, which considers the organic species only.

Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

2010-05-01

232

Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols  

NASA Astrophysics Data System (ADS)

Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation. For simplified partitioning parametrizations, we suggest a modified definition of the effective saturation concentration, Cj*, by including water and other inorganics in the absorbing phase. Such a Cj* definition reduces the RH-dependency of the gas/particle partitioning of semivolatile organics in organic-inorganic aerosols by an order of magnitude as compared to the currently accepted definition, which considers the organic species only.

Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

2010-08-01

233

Insights into the secondary fraction of the organic aerosol in a Mediterranean urban area: Marseille  

NASA Astrophysics Data System (ADS)

A comprehensive aerosol characterization was conducted at Marseille during summer, including organic (OC) and elemental carbon (EC), major ionic species, radiocarbon (14C), water soluble OC and HULIS (HUmic LIke Substances), elemental composition and primary and secondary organic markers. This paper is the second paper of a two-part series investigating the sources of organic aerosol. While the first paper investigates the primary sources of Organic Aerosol (OA) (El Haddad et al., 2010), this second paper focused on the secondary fraction of OA. In the context of overall OC mass balance, primary OC (POC) contributes on average for only 22% and was dominated by vehicular emissions accounting on average for 17% of OC. As a result, 78% of OC mass cannot be attributed to the major primary sources and remains un-apportioned. Radiocarbon measurements suggest that more than 70% of this fraction is of modern origins, assigned predominantly to biogenic secondary organic carbon (BSOC). Therefore, contributions from three traditional BSOC precursors, isoprene, ?-pinene and ?-caryophellene, were considered. These were estimated using the ambient concentrations of SOA markers from each precursor and laboratory-derived marker mass fraction factors. Secondary organic markers derived from isoprene photo-oxidation (i.e. 2-methylglyceric acid and 2-methyltetrols) do not exhibit the same temporal trends. This variability was assigned to the influence of NOx concentration on their formation pathways and to their potential decay by further processing in the atmosphere. The influence of changes in isoprene chemistry on assessment of isoprene SOC contribution was evaluated explicitly. The results suggest a 60-fold variation between the different estimates computed using different isoprene SOC markers, implying that the available profiles do not reflect the actual isoprene SOC composition observed in Marseille. Using the marker-based approach, the aggregate contribution from traditional BSOC was estimated at only 4.2% of total OC and was dominated by ?-pinene SOC accounting on average for 3.4% of OC. As a result, these estimates underpredict the inexplicably high loading of OC. This underestimation can be associated with (1) uncertainties underlying the marker-based approach, (2) presence of other SOC precursors and (3) further processing of fresh SOC, as indicated by organosulfates (RSO4) and HUmic LIke Substances (HULIS) measurements.

El Haddad, I.; Marchand, N.; Temime-Roussel, B.; Wortham, H.; Piot, C.; Besombes, J.-L.; Baduel, C.; Voisin, D.; Armengaud, A.; Jaffrezo, J.-L.

2010-11-01

234

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

235

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

236

Inorganic ion and nitrogen isotopic compositions of atmospheric aerosols at Yurihonjo, Japan: Implications for nitrogen sources  

NASA Astrophysics Data System (ADS)

We studied the suspended particulate matter (SPM) collected in Akita Prefecture, Japan from April 2008 to January 2009 for inorganic ion composition and nitrogen isotopic ratio (?15N) of NH4+ and NO3-. The results showed an average SPM concentration of 15.6 ?g m-3. The seasonal trend for SPM was higher values in the spring, lower in the winter. The major cations were Na+, NH4+, Ca2+ and major anions were SO42-, NO3-, Cl-. The annual correlation coefficient of ions indicates a very high value with NH4+ and SO42- (R = 0.93), NO3- and K+ (R = 0.65), NO3- and Ca2+ (R = 0.62). The high springtime values are the apparent result of the dust stream from Asia. Average ?15N-NH4+ and ?15N-NO3- were 16.1‰ and -0.69‰, respectively. ?15N-NH4+ increased slightly in summer, and ?15N-NO3- increased considerably in winter. The trends indicated conversely. The heavy ?15N-NH4+ in summer appears to be from agricultural sources such as animal waste and fertilizer. In addition, according to the difference in isotopes of NOx sources as the precursor of NO3-, the dominant origin of heavy ?15N-NO3- in winter could be NOx emitted from fossil fuel combustion at low temperature. Moreover, the average ?15N-NO3- seemed to be made to baseline (approximately 0%) by vehicle emissions at high temperature. These results are considered to be very reasonable.

Kawashima, Hiroto; Kurahashi, Takahiro

2011-11-01

237

Secondary organic aerosol (SOA) formation through cloud processing: Aqueous photooxidation of glyoxal and methylglyoxal  

NASA Astrophysics Data System (ADS)

This dissertation provides evidence supporting the hypothesis that secondary organic aerosol (SOA) is formed in the atmosphere through aqueous-phase reactions in clouds. Accurate prediction of SOA formation is critical because organic aerosol adversely affects health, visibility and climate. If in-cloud SOA formation is significant, then current models incorrectly predict the concentrations, atmospheric distributions, properties, behavior and effects of atmospheric organic aerosol. During cloud processing, water-soluble gas-phase oxidation products of reactive organic gases (e.g., aromatics and alkenes including, isoprene) partition into cloud droplets where they react further during regional transport to form low volatility compounds (e.g., carboxylic acids and oligomers) that remain, in part, in the particle phase upon droplet evaporation, adding to the atmospheric particulate matter (PM) burden. Batch photochemical reactions of glyoxal, methylglyoxal and pyruvic acid with hydrogen peroxide were conducted to validate and improve proposed in-cloud SOA formation pathways. This research verifies that aqueous photooxidation of these compounds yields oxalic acid and other compounds (e.g., oligomes) likely to contribute to SOA. Electro-spray ionization-mass spectrometry (ESI-MS) analysis provided evidence for oligomer formation. This work resolved a discrepancy in the literature regarding the aqueous-phase fate of methylglyoxal and pyruvic acid, providing a link between isoprene, a biogenic compound with a large (˜500 Tg yr-1) world-wide emission flux, and SOA. Experimental time series product concentrations were compared to predictions using proposed pathways and reaction rate constants from the literature. Not all products were predicted by the models and expected products did not match observed time profiles. Additional oxidation pathways for glyoxal and methylglyoxal were identified and modified aqueous-phase oxidation mechanisms were proposed. Modification led to substantially improved agreement between experimental measurements and model predictions. The improved mechanistic understanding regarding the SOA in-cloud formation pathway provided by this dissertation is needed to improve predictive air quality and climate models and to develop more effective air quality management plans. While the climactic importance of secondary sulfate production via cloud processing is well known, and organic aerosol is known to play a role in global climate, the potential importance of in-cloud SOA formation is only just beginning to be considered.

Carlton, Ann Marie Grover

238

Understanding and constraining global secondary organic aerosol amount and size-resolved condensational behavior  

NASA Astrophysics Data System (ADS)

Recent research has shown that secondary organic aerosols (SOA) are major contributors to ultrafine particle growth to climatically relevant sizes, increasing global cloud condensation nuclei (CCN) concentrations within the continental boundary layer. However, there are three recent developments regarding the condensation of SOA that lead to uncertainties in the contribution of SOA to particle growth and CCN concentrations: (1) while many global models contain only biogenic sources of SOA (with annual production rates generally 10-30 Tg yr-1), recent studies have shown that an additional source of SOA around 100 -1 correlated with anthropogenic carbon monoxide (CO) emissions may be required to match measurements. (2) Many models treat SOA solely as semivolatile, which leads to condensation of SOA proportional to the aerosol mass distribution; however, recent closure studies with field measurements show nucleation mode growth can be captured only if it is assumed that a significant fraction of SOA condenses proportional to the Fuchs aerosol surface area. This suggests a very low volatility of the condensing vapors. (3) Other recent studies of particle growth show that SOA condensation deviates from Fuchs surface-area condensation at sizes smaller than 10 nm and that size-dependent growth rate parameterizations (GRP) are needed to match measurements. We explore the significance of these three findings using GEOS-Chem-TOMAS global aerosol microphysics model and observations of aerosol size distributions around the globe. The change in the concentration of particles of size Dp > 40 nm (N40) within the BL assuming surface-area condensation compared to mass-distribution net condensation yielded a global increase of 11% but exceeded 100% in biogenically active regions. The percent change in N40 within the BL with the inclusion of the additional 100 Tg SOA yr-1 compared to the base simulation solely with biogenic SOA emissions (19 Tg yr-1) both using surface area condensation yielded a global increase of 13.7%, but exceeded 50% in regions with large CO emissions. The inclusion of two different GRPs in the additional-SOA case both yielded a global increase in N40 of <1%, however exceeded 5% in some locations in the most extreme case. All of the model simulations were compared to measured data obtained from diverse locations around the globe and the results confirmed a decrease in the model-measurement bias and improved slope for comparing modeled to measured CCN when non-volatile SOA was assumed and the extra SOA was included.

D'Andrea, S. D.; Häkkinen, S. A. K.; Westervelt, D. M.; Kuang, C.; Levin, E. J. T.; Leaitch, W. R.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

2013-07-01

239

Reduction in biomass burning aerosol light absorption upon humidification: Roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer  

SciTech Connect

Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used are Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients reveal a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: 1. Shielding of inner monomers after particle consolidation or collapse with water uptake; 2. The contribution of mass transfer through evaporation and condensation at high relative humidity to the usual heat transfer pathway for energy release by laser heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

lewis, Kristen A.; Arnott, W. P.; Moosmuller, H.; Chakrabarti, Raj; Carrico, Christian M.; Kreidenweis, Sonia M.; Day, Derek E.; Malm, William C.; Laskin, Alexander; Jimenez, Jose L.; Ulbrich, Ingrid M.; Huffman, John A.; Onasch, Timothy B.; Trimborn, Achim; Liu, Li; Mishchenko, M.

2009-11-27

240

Ozone-driven daytime formation of secondary organic aerosol containing carboxylic acid groups and alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely correlated with oxygenated organic factors from aerosol mass spectrometry measurements. The high fraction of acid groups and the high ratio of oxygen to carbon in this factor suggest that this factor is composed of secondary organic aerosol (SOA) products of combustion emissions from the upwind industrial region (the ports of Los Angeles and Long Beach). Another indication of the photochemically-driven secondary formation of this combustion-emitted organic mass (OM) was the daytime increase in the concentrations of acid groups and the combustion factors. This daytime increase closely tracked the O3 mixing ratio with a correlation coefficient of 0.7, indicating O3 was closely associated with the SOA maximum and thus likely the oxidant that resulted in acid group formation. Using a pseudo-Lagrangian framework to interpret this daytime increase of carboxylic acid groups and the combustion factors, we estimate that the carboxylic acid groups formed in a 12-h daytime period of one day ("Today's SOA") accounted for 25-33 % of the measured carboxylic acid group mass, while the remaining 67-75 % (of the carboxylic acid group mass) was likely formed 1-3 days previously (the "Background SOA"). A similar estimate of the daytime increase in the combustion factors suggests that "Today's SOA" and the "Background SOA" respectively contributed 25-50 % and 50-75 % of the combustion factor (the "Total SOA"), for a "Total SOA" contribution to the OM of 60 % for the project average. Further, size-resolved spectrometric and spectroscopic characterization of the particle OM indicate that the majority of the OM formed by condensation of gas-phase oxidation products. This unique set of measurements and methods to quantify and characterize photochemically and ozone-linked carboxylic acid group formation provide independent and consistent assessments of the secondary fraction of OM, which could result from second generation products of the oxidation of gas-phase alkane (molecules).

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-08-01

241

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

242

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

2012-08-17

243

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.

2012-01-01

244

Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber  

NASA Astrophysics Data System (ADS)

The evolution of secondary organic aerosols (SOA) during (photo-)chemical aging processes was investigated in a smog chamber. SOA from 10-40 ppb ?-pinene was formed during ozonolysis followed by aging with OH radicals. The particles' volatility and hygroscopicity (expressed as volume fraction remaining (VFR) and hygroscopicity parameter ?) were measured with a volatility and hygroscopicity tandem differential mobility analyzer (V/H-TDMA). These measurements were used as sensitive physical parameters to reveal the possible mechanisms responsible for the chemical changes in the SOA composition during aging: A change of VFR and/or ? during processing of atmospheric aerosol may occur either by addition of SOA mass (by condensation) or by an exchange of molecules in the SOA by other molecules with different properties. The former process increases the SOA mass by definition, while the latter keeps the SOA mass roughly constant and may occur either by heterogeneous reactions on the surface of the SOA particles, by homogeneous reactions like oligomerization or by an evaporation - gas-phase oxidation - recondensation cycle. Thus, when there is a substantial change in the aerosol mass with time, the condensation mechanism may be assumed to be dominant, while, when the mass stays roughly constant the exchange mechanism is likely to be dominant, a process termed ripening here. Depending on the phase of the experiment, an O3 mediated condensation, O3 mediated ripening, OH mediated condensation, and OH mediated ripening could be distinguished. During the O3 mediated condensation the particles volatility decreased (increasing VFR) while the hygroscopicity increased. Thereafter, in the course of O3 mediated ripening volatility continued to decrease, but hygroscopicity stayed roughly constant. After exposing the SOA to OH radicals an OH mediated condensation started with a significant increase of SOA mass. Concurrently, hygroscopicity and volatility increased. This phase was then followed by an OH mediated ripening with a decrease of volatility.

Tritscher, T.; Dommen, J.; Decarlo, P. F.; Barmet, P. B.; Praplan, A. P.; Weingartner, E.; Gysel, M.; Prévôt, A. S. H.; Riipinen, I.; Donahue, N. M.; Baltensperger, U.

2011-03-01

245

Secondary Organic Aerosol (SOA) production from the Aqueous Reactions of Phenols and Triplet Aromatic Carbonyls  

NASA Astrophysics Data System (ADS)

The phenolic compounds guaiacol, syringol and phenol have recently been shown to produce secondary organic aerosol (SOA) at high yields in the aqueous phase upon exposure to simulated sunlight and hydroxyl radical. These phenols are significant products from wood combustion that can readily enter atmospheric waters, such as aqueous aerosol particles and cloud/fog droplets. Once in the aqueous phase, phenols can react with the triplet excited states of non-phenolic aromatic carbonyls (NPCs), particle-bound organics that are also emitted from wood combustion. In this study, we examined the aqueous-phase production of SOA from the reaction of phenolic compounds with triplet excited state organics. These aqueous phase reactions were tested by illuminating solutions containing a phenolic compound and NPC under simulated sunlight at various concentrations and pH values. The phenolic compound is consumed during these reactions, following a first-order decay that varies with phenol concentration, phenol identity, and pH. The non-volatile product mass formed in our illuminated solutions was determined gravimetrically and by analysis with High Resolution Time of Flight Aerosol Mass Spectrometry (HR-AMS). The SOA mass yield was determined as the mass of non-volatile product formed per mass of phenolic consumed during illumination. We also used HR-AMS to analyze for elemental composition, carbon oxidation state, and oligomers in the SOA produced. Our results to date indicate that phenols can be rapidly oxidized by triplet excited states under environmentally relevant conditions and that the accompanying SOA mass yields are very high.

Smith, J.; Sun, Y.; Lu, Y.; Zhang, Q.; Anastasio, C.

2010-12-01

246

Effect of humidity on the composition of isoprene photooxidation secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The effect of relative humidity (RH) on the composition and concentrations of gas-phase products and secondary organic aerosol (SOA) generated from the photooxidation of isoprene under high-NOx conditions was investigated. Experiments were performed with hydrogen peroxide as the OH precursor and in the absence of seed aerosol. The relative yields of most gas-phase products were the same regardless of initial water vapor concentration with exception of hydroxyacetone and glycolaldehyde, which were considerably affected by RH. A significant change was observed in the SOA composition, with many unique condensed-phase products formed under humid (90 % RH) vs. dry (<2 % RH) conditions, without any detectable effect on the rate and extent of the SOA mass growth. There is a 40 % reduction in the number and relative abundance of distinct particle-phase nitrogen-containing organic compounds (NOC) detected by high resolution mass spectrometry. The suppression of condensation reactions, which produce water as a product, is the most important chemical effect of the increased RH. For example, the total signal from oligomeric esters of 2-methylglyceric acid was reduced by about 60 % under humid conditions and the maximum oligomer chain lengths were reduced by 7-11 carbons. Oligomers formed by addition mechanisms, without direct involvement of water, also decreased at elevated RH but to a much smaller extent. The observed reduction in the extent of condensation-type oligomerization at high RH may have substantial impact on the phase characteristics and hygroscopicity of the isoprene aerosol. The reduction in the amount of organic nitrates in the particle phase has implications for understanding the budget of NOC compounds.

Nguyen, T. B.; Roach, P. J.; Laskin, J.; Laskin, A.; Nizkorodov, S. A.

2011-07-01

247

Oxidative Aging and Secondary Organic Aerosol Formation from Simulated Wildfire Emissions  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

248

Formation of secondary organic aerosol from irradiated ?-pinene\\/toluene\\/NOx mixtures and the effect of isoprene and sulfur dioxide  

Microsoft Academic Search

Secondary organic aerosol (SOA) was generated by irradiating a series of ?-pinene\\/toluene\\/NOx mixtures in the absence and presence of isoprene or sulfur dioxide. The purpose of the experiment was to evaluate the extent to which chemical perturbations to this base-case (?-pinene\\/toluene) mixture led to changes in the gas-phase chemistry which strongly influences mass and composition of SOA and secondary organic

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

2008-01-01

249

Primary and secondary organic aerosol origin by combined gas-particle phase source apportionment  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA), a prominent fraction of particulate organic mass (OA), remains poorly constrained. Its formation involves several unknown precursors, formation and evolution pathways and multiple natural and anthropogenic sources. Here a combined gas-particle phase source apportionment is applied to wintertime and summertime data collected in the megacity of Paris in order to investigate SOA origin during both seasons. This was possible by combining the information provided by an aerosol mass spectrometer (AMS) and a proton transfer reaction mass spectrometer (PTR-MS). A better constrained apportionment of primary OA (POA) sources is also achieved using this methodology, making use of gas-phase tracers. These tracers made possible the discrimination between biogenic and continental/anthropogenic sources of SOA. We found that continental SOA was dominant during both seasons (24-50% of total OA), while contributions from photochemistry-driven SOA (9% of total OA) and marine emissions (13% of total OA) were also observed during summertime. A semi-volatile nighttime component was also identified (up to 18% of total OA during wintertime). This approach was successfully applied here and implemented in a new source apportionment toolkit.

Crippa, M.; Canonaco, F.; Slowik, J. G.; El Haddad, I.; DeCarlo, P. F.; Mohr, C.; Heringa, M. F.; Chirico, R.; Marchand, N.; Temime-Roussel, B.; Abidi, E.; Poulain, L.; Wiedensohler, A.; Baltensperger, U.; Prévôt, A. S. H.

2013-08-01

250

Relationship between oxidation level and optical properties of secondary organic aerosol.  

PubMed

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[5.2.1.0(2,6)]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. PMID:23701291

Lambe, Andrew T; Cappa, Christopher D; Massoli, Paola; Onasch, Timothy B; Forestieri, Sara D; Martin, Alexander T; Cummings, Molly J; Croasdale, David R; Brune, William H; Worsnop, Douglas R; Davidovits, Paul

2013-06-06

251

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

SciTech Connect

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

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

2008-10-01

252

Particle mass yield in secondary organic aerosol formed by the dark ozonolysis of ?-pinene  

NASA Astrophysics Data System (ADS)

The yield of particle mass in secondary organic aerosol (SOA) formed by dark ozonolysis was measured for 0.3-22.8 ppbv of reacted ?-pinene. Most experiments were conducted using a continuous-flow chamber, allowing nearly constant SOA concentration and chemical composition for several days. For comparison, some experiments were also conducted in batch mode. Reaction conditions were 25°C, 40% RH, dry (NH4)SO4 seed particles, and excess 1-butanol. The organic particle loading was independently measured by an aerosol mass spectrometer and a scanning mobility particle sizer, and the two measurements agreed well. The observations showed that SOA formation occurred for even the lowest reacted ?-pinene concentration of 0.3 ppbv. The particle mass yield was 0.09 at 0.15 ?g m-3, increasing to 0.27 at 40 ?g m-3. Compared to some results reported in the literature, the yields were 80 to 100% larger for loadings above 2 ?g m-3. At lower loadings, the yields had an offset of approximately +0.07 from those reported in the literature. To as low as 0.15 ?m-3, the yield curve had no inflection point toward null yield, implying the formation of one or several products having vapor pressures below this value. These observations of increased yields, especially for low loadings, are potentially important for accurate prediction by chemical transport models of organic particle concentrations in the ambient atmosphere.

Shilling, J. E.; Chen, Q.; King, S. M.; Rosenoern, T.; Kroll, J. H.; Worsnop, D. R.; McKinney, K. A.; Martin, S. T.

2008-04-01

253

Particle mass yield in secondary organic aerosol formed by the dark ozonolysis of ?-pinene  

NASA Astrophysics Data System (ADS)

The yield of particle mass in secondary organic aerosol (SOA) formed by dark ozonolysis was measured for 0.3-22.8 ppbv of reacted ?-pinene. Most experiments were conducted using a continuous-flow chamber, allowing nearly constant SOA concentration and chemical composition for several days. For comparison, some experiments were also conducted in batch mode. Reaction conditions were 25°C, 40% RH, dry (NH)4SO4 seed particles, and excess 1-butanol. The organic particle loading was independently measured by an aerosol mass spectrometer and a scanning mobility particle sizer, and the two measurements agreed well. The observations showed that SOA formation occurred for even the lowest reacted ?-pinene concentration of 0.3 ppbv. The particle mass yield was 0.09 at 0.15 ?g m-3, increasing to 0.27 at 40 ?g m-3. Compared to results reported in the literature, the yields were 80 to 100% larger for loadings above 2 ?g m-3. At lower loadings, the yields had an offset of approximately +0.07 from those reported in the literature. To as low as 0.15 ?g m-3, the yield curve had no inflection point toward null yield, implying the formation of one or several products having vapor pressures below this value. These observations of increased yields, especially for low loadings, are potentially important for accurate prediction by chemical transport models of organic particle concentrations in the ambient atmosphere.

Shilling, J. E.; Chen, Q.; King, S. M.; Rosenoern, T.; Kroll, J. H.; Worsnop, D. R.; McKinney, K. A.; Martin, S. T.

2007-12-01

254

Effect of humidity on the composition and yield of isoprene photooxidation secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The effect of relative humidity (RH) on the composition and concentrations of gas-phase products and secondary organic aerosol (SOA) generated from the photooxidation of isoprene under high-NOx conditions was investigated. The yields of most gas-phase products were the same regardless of initial water vapor concentration with exception of hydroxyacetone and glycolaldehyde, which were considerably affected by RH. A significant change was observed in the SOA composition, with many unique condensed-phase products formed under humid (90% RH) vs. dry (<2% RH) conditions, without any observable effect on the rate and extent of the SOA mass growth. There is a 40% reduction in the number and relative abundance of distinct particle-phase organic nitrogen (ON) compounds detected by high resolution mass spectrometry. The suppression of condensation reactions, which produce water as a product, is the most important chemical effect of the increased RH. For example, the total signal from oligomeric esters of 2-methylglyceric acid was reduced by about 60% under humid conditions and the maximum oligomer chain lengths were reduced by 7-11 carbons. Oligomers formed by addition mechanisms, without direct involvement of water, also decreased at elevated RH but to a much smaller extent. The observed substantial reduction in the extent of condensation-type oligomerization at high RH may have substantial impact on the phase characteristics and hygroscopicity of the isoprene aerosol. The reduction in the amount of organic nitrates in the particle phase has implications for understanding the budget of ON compounds.

Nguyen, T. B.; Roach, P. J.; Laskin, J.; Laskin, A.; Nizkorodov, S. A.

2011-03-01

255

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

256

Aerosols  

PubMed Central

We and others have recently reported that prions can be transmitted to mice via aerosols. These reports spurred a lively public discussion on the possible public-health threats represented by prion-containing aerosols. Here we offer our view on the context in which these findings should be placed. On the one hand, the fact that nebulized prions can transmit disease cannot be taken to signify that prions are airborne under natural circumstances. On the other hand, it appears important to underscore the fact that aerosols can originate very easily in a broad variety of experimental and natural environmental conditions. Aerosols are a virtually unavoidable consequence of the handling of fluids; complete prevention of the generation of aerosols is very difficult. While prions have never been found to be transmissible via aerosols under natural conditions, it appears prudent to strive to minimize exposure to potentially prion-infected aerosols whenever the latter may arise—for example in scientific and diagnostic laboratories handling brain matter, cerebrospinal fluids, and other potentially contaminated materials, as well as abattoirs. Equally important is that prion biosafety training be focused on the control of, and protection from, prion-infected aerosols.

2011-01-01

257

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...

258

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

EPA Science Inventory

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

259

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

Microsoft Academic Search

Organic particulate matter (PM) has a major impact on atmospheric chemistry, climate, and human health. Secondary organic aerosol (SOA) accounts for a rather significant fraction of organic PM; this includes SOA produced by oxidation of biogenically emitted monoterpenes. Once such SOA is formed, it is believed to undergo slow aging processes, which may have large effects on the physical and

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

2009-01-01

260

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

261

Ultrafine particles in indoor air of a school: possible role of secondary organic aerosols.  

PubMed

The aim of this work was to investigate ultrafine particles (<0.1 microm) in primary school classrooms, in relation to the classroom activities. The investigations were conducted in three classrooms during two measuring campaigns, which together encompassed a period of 60 days. Initial investigations showed that under the normal operating conditions of the school there were many occasions in all three classrooms where indoor particle concentrations increased significantly compared to outdoor levels. By far the highest increases in the classroom resulted from art activities (painting, gluing, and drawing), at times reaching over 1.4 x 10(5) particle cm(-3). The indoor particle concentrations exceeded outdoor concentrations by approximately 1 order of magnitude, with a count median diameter ranging from 20 to 50 nm. Significant increases also occurred during cleaning activities, when detergents were used. GC-MS analysis conducted on 4 samples randomly selected from about 30 different paints and glues, as well as the detergent used in the school, showed that d-limonene was one of the main organic compounds of the detergent, however, it was not detected in the samples of the paints and the glue. Controlled experiments showed that this monoterpene, emitted from the detergent, reacted with O(3) (at outdoor ambient concentrations ranging from 0.06 to 0.08 ppm) and formed secondary organic aerosols. Further investigations to identify other liquids that may be potential sources of the precursors of secondary organic aerosols were outside the scope of this project, however, it is expected that the problem identified by this study could be more widely spread, since most primary schools use liquid materials for art classes, and all schools use detergents for cleaning. Further studies are therefore recommended to better understand this phenomenon and also to minimize exposure of school children to ultrafine particles from these indoor sources. PMID:20000499

Morawska, Lidia; He, Congrong; Johnson, Graham; Guo, Hai; Uhde, Erik; Ayoko, Godwin

2009-12-15

262

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, 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 it also contributes to particle nucleation; using two organically-mediated mechanisms for new particle formation we simulate global annual mean 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 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 indirect radiative effect 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 (DRE) 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 biogenic volatile organic compounds (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.

2013-06-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

264

Secondary organic aerosol formation of relevance to the marine boundary layer  

NASA Astrophysics Data System (ADS)

The chlorine atom (Cl) is a potential oxidant of volatile organic compounds (VOCs) in the atmosphere and is hypothesized to lead to secondary organic aerosol (SOA) formation in coastal areas. The purpose of this dissertation is to test this hypothesis and quantify the SOA formation potentials of some representative biogenic and anthropogenic hydrocarbons when oxidized by Cl in laboratory chamber experiments. The chosen model compounds for biogenic and anthropogenic hydrocarbons in this study are three monoterpenes (alpha-pinene, beta-pinene, and d-limonene) and two aromatics (m-xylene and toluene), respectively. Results indicate that the oxidation of these monoterpenes and aromatics generates significant amounts of aerosol. The SOA yields of alpha-pinene, beta-pinene, and d-limonene obtained in this study are comparable to those when they are oxidized by ozone, by nitrate radical, and in photooxidation scenarios. For aerosol mass up to 30.0 mug m-3, their yields reach approximately 0.20, 0.20, and 0.30, respectively. The SOA yields for m-xylene and toluene are found to be in the range of 0.035 to 0.12 for aerosol concentrations up to 19 mug m-3. For d-limonene and toluene, data indicate two yield curves that depend on the initial concentration ratios of Cl precursor to hydrocarbon hydrocarbon. Zero-dimensional calculations based on these yields show that SOA formation from the five model compounds when oxidized by Cl in the marine boundary layer could be a significant source of SOA in the early morning. In addition, the mechanistic reaction pathways for Cl oxidation of alpha-pinene, beta-pinene, d-limonene, and toluene with Cl have been developed within the framework of the Caltech Atmospheric Chemistry Mechanisms (CACM). Output from the developed mechanisms is combined with an absorptive partitioning model to predict precursor decay curves and time-dependent SOA concentrations in experiments. Model calculations are able to match (in general within general +/- 50%) final measured SOA concentrations. Species predicted to dominate SOA composition include carboxylic acids and organic peroxides. Finally, the influence of surface tension on the formation of SOA is investigated using a size-dependent absorptive partitioning model that accounts for the influence of surface tension on the gas/particle partitioning of semi-volatile organic compounds (the Kelvin effect). Results from numerical simulations indicate that if non-polar organic species constitute a significant fraction of pre-existing aerosol (PA), the Kelvin effect on SOA formation may be negligible. However, if PA is dominated by polar organic compounds, the Kelvin effect on SUA formation is significant when the PA initial diameter is smaller than approximately 100 nm (decreasing SUA formation from specific compounds by as much as a factor of 2.5). If the PA is an aqueous aerosol, the Kelvin effect on SOA formation is most important (decreasing SOA formation from specific compounds by as much as a factor of 10).

Cai, Xuyi

265

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

266

Overview of the inorganic and organic composition of size-segregated aerosol in Rondônia, Brazil, from the biomass-burning period to the onset of the wet season  

NASA Astrophysics Data System (ADS)

The aerosol characterization experiment performed within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) field experiment carried out in Rondônia, Brazil, in the period from September to November 2002 provides a unique data set of size-resolved chemical composition of boundary layer aerosol over the Amazon Basin from the intense biomass-burning period to the onset of the wet season. Three main periods were clearly distinguished on the basis of the PM10 concentration trend during the experiment: (1) dry period, with average PM10 well above 50 ?g m-3; (2) transition period, during which the 24-hour-averaged PM10 never exceeded 40 ?g m-3 and never dropped below 10 ?g m-3; (3) and wet period, characterized by 48-hour-averaged concentrations of PM10 below 12 ?g m-3 and sometimes as low as 2 ?g m-3. The trend of PM10 reflects that of CO concentration and can be directly linked to the decreasing intensity of the biomass-burning activities from September through November, because of the progressive onset of the wet season. Two prominent aerosol modes, in the submicron and supermicron size ranges, were detected throughout the experiment. Dry period size distributions are dominated by the fine mode, while the fine and coarse modes show almost the same concentrations during the wet period. The supermicron fraction of the aerosol is composed mainly of primary particles of crustal or biological origin, whereas submicron particles are produced in high concentrations only during the biomass-burning periods and are mainly composed of organic material, mostly water-soluble, and ˜10% of soluble inorganic salts, with sulphate as the major anion. Size-resolved average aerosol chemical compositions are reported for the dry, transition, and wet periods. However, significant variations in the aerosol composition and concentrations were observed within each period, which can be classified into two categories: (1) diurnal oscillations, caused by the diurnal cycle of the boundary layer and the different combustion phase active during day (flaming) or night (smouldering); and (2) day-to-day variations, due to alternating phases of relatively wet and dry conditions. In a second part of the study, three subperiods representative of the conditions occurring in the dry, transition, and wet periods were isolated to follow the evolution of the aerosol chemical composition as a function of changes in rainfall rate and in the strength of the sources of particulate matter. The chemical data set provided by the SMOCC field experiment will be useful to characterize the aerosol hygroscopic properties and the ability of the particles to act as cloud condensation nuclei.

Fuzzi, Sandro; Decesari, Stefano; Facchini, Maria Cristina; Cavalli, Fabrizia; Emblico, Lorenza; Mircea, Mihaiela; Andreae, Meinrat O.; Trebs, Ivonne; Hoffer, AndráS.; Guyon, Pascal; Artaxo, Paulo; Rizzo, Luciana V.; Lara, Luciene L.; Pauliquevis, Theotonio; Maenhaut, Willy; Raes, Nico; Chi, Xuguang; Mayol-Bracero, Olga L.; Soto-GarcíA, Lydia L.; Claeys, Magda; Kourtchev, Ivan; Rissler, Jenny; Swietlicki, Erik; Tagliavini, Emilio; Schkolnik, Gal; Falkovich, Alla H.; Rudich, Yinon; Fisch, Gilberto; Gatti, Luciana V.

2007-01-01

267

Oxidation of gaseous elemental mercury in the presence of secondary organic aerosols  

NASA Astrophysics Data System (ADS)

Gaseous elemental mercury (GEM; Hg0(g)) was oxidized by ozone and secondary hydroxyl radicals generated by the chemistry associated with the formation of secondary organic aerosols. The reaction was investigated in a 9-m3 Teflon® batch reactor. The losses of GEM in ozone-only experiments compared well with numerical model predictions based on published reaction rates, and a second order rate analysis gave a reaction rate of (7.4 ± 0.5) × 10-19 cm3 molecules-1 s-1, which was statistically indistinct from recent publications. Furthermore, the net oxidation of GEM observed in the SOA reaction system agreed well with a numerical model based on the GEM-ozone reaction rate determined in this study and a published GEM-OH oxidation rate. Recent modeling studies of mercury atmospheric cycling have found that use of laboratory-based GEM-ozone reaction rate coefficients caused overestimation of GEM oxidation, while theoretical studies cast doubt over the viability of the GEM-ozone oxidation reaction in the real atmosphere. The results presented here suggest that the reaction is viable in the atmosphere and that recent published reaction rates for GEM and ozone are pertinent for use in atmospheric models. An average of GEM-ozone rates determined during this and recent studies was 6.9 ± 0.9 × 10-19 cm3 molecules-1 s-1. This value is recommended for use in future modeling studies.

Rutter, A. P.; Shakya, K. M.; Lehr, R.; Schauer, J. J.; Griffin, R. J.

2012-11-01

268

Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation  

Microsoft Academic Search

To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 mug\\/m3 and 78.2±58.4 mug\\/m3, with PM1.8\\/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine

S. Guo; M. Hu; Z. B. Wang; J. Slanina; Y. L. Zhao

2009-01-01

269

Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation  

Microsoft Academic Search

To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 mug\\/m3 and 78.2±58.4 mug\\/m3, with PM1.8\\/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine

S. Guo; M. Hu; Z. B. Wang; J. Slanina; Y. L. Zhao

2010-01-01

270

Inorganic, organic and macromolecular components of fine aerosol in different areas of Europe in relation to their water solubility  

Microsoft Academic Search

A chemical mass balance of fine aerosol (<1.5?m AED) collected at three European sites was performed with reference to the water solubility of the different aerosol classes of components. The sampling sites are characterised by different pollution conditions and aerosol loading in the air. Aspvreten is a background site in central Sweden, K-puszta is a rural site in the Great

S. Zappoli; A. Andracchio; S. Fuzzi; M. C. Facchini; A. Gelencsér; G. Kiss; Z. Krivácsy; Á. Molnár; E. Mészáros; H.-C. Hansson; K. Rosman; Y. Zebühr

1999-01-01

271

[Secondary aerosol formation through photochemical reactions estimated by using air quality monitoring data in the downtown of Pudong, Shanghai].  

PubMed

Analyses of diurnal patterns of PM10 in the downtown of Pudong, Shanghai have been performed in this study at different daily ozone maximum concentrations (O(3,max)) from May to October, 2010. In order to evaluate secondary aerosol formation at different ozone levels, CO was used as a tracer for primary aerosol, and 0(3, max) was used as an index for photochemical activity. Results show that along with increasing of O3 concentration, the concentration of primary and secondary aerosol was increased respectively from 0. 036 to 0.044 mg x m(-3) and from 0.018 to 0.055 mg x m(-3). The ratio of secondary to primary aerosol was increased from 49.8% to 124.5%. Furthermore, along with the increase of O(3, max) the forming time of O(3,max) and secondary aerosol was changed respectively from 13:00 to 14:00 and from 11:00-20:00 to 09:00-20:00. At the same time, the chemical composition of PM2.5 was different at different photochemical levels. PM(2.5) was composed of 12.0% organic carbon (OC), 18.7% sulfate (SO4(2-1)), 13.1% nitrate (NO3-) and 4.5% element carbon (EC) when O(3, max) was < 0.10 mg x m(-3) and PM2.5 was composed of 20.0% organic carbon (OC), 22.9% sulfate, 23.1% nitrate and 4.7% element carbon (EC) with O(3, max) > 0. 20 mg x m(-3). These results approved that the photochemical reactivity promoted the production of SO4(2-), NO3- and OC. PMID:23914560

Cui, Hu-xiong; Wu, Ya-ming; Duan, Yu-sen; Fu, Qing-yan; Zhang, Yi-hua; Wang, Dong-fang; Wang, Qian

2013-05-01

272

Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols  

NASA Astrophysics Data System (ADS)

We construct global budgets of atmospheric glyoxal and methylglyoxal with the goal of quantifying their potential for global secondary organic aerosol (SOA) formation via irreversible uptake by aqueous aerosols and clouds. We conduct a detailed simulation of glyoxal and methylglyoxal in the GEOS-Chem global 3-D chemical transport model including our best knowledge of source and sink processes. Our resulting best estimates of the global sources of glyoxal and methylglyoxal are 45 Tg a-1 and 140 Tg a-1, respectively. Oxidation of biogenic isoprene contributes globally 47% of glyoxal and 79% of methylglyoxal. The second most important precursors are acetylene (mostly anthropogenic) for glyoxal and acetone (mostly biogenic) for methylglyoxal. Both acetylene and acetone have long lifetimes and provide a source of dicarbonyls in the free troposphere. Atmospheric lifetimes of glyoxal and methylglyoxal in the model are 2.9 h and 1.6 h, respectively, mostly determined by photolysis. Simulated dicarbonyl concentrations in continental surface air at northern midlatitudes are in the range 10-100 ppt, consistent with in situ measurements. On a global scale, the highest concentrations are over biomass burning regions, in agreement with glyoxal column observations from the SCIAMACHY satellite instrument. SCIAMACHY and a few ship cruises also suggest a large marine source of dicarbonyls missing from our model. The global source of SOA from the irreversible uptake of dicarbonyls in GEOS-Chem is 11 Tg C a-1, including 2.6 Tg C a-1 from glyoxal and 8 Tg C a-1 from methylglyoxal; 90% of this source takes place in clouds. The magnitude of the global SOA source from dicarbonyls is comparable to that computed in GEOS-Chem from the standard mechanism involving reversible partitioning of semivolatile products from the oxidation of monoterpenes, sesquiterpenes, isoprene, and aromatics.

Fu, Tzung-May; Jacob, Daniel J.; Wittrock, Folkard; Burrows, John P.; Vrekoussis, Mihalis; Henze, Daven K.

2008-08-01

273

The Chemical and Microphysical Properties of Secondary Organic Aerosols from Holm Oak Emissions  

NASA Astrophysics Data System (ADS)

Plant-emitted volatile organic compounds (VOC) undergo atmospheric oxidation, which leads to the formation of secondary organic aerosols (SOA). Large uncertainties exist about possible climatic effects on SOA formation from biogenic sources. Therefore it is important to investigate the impact of environmental conditions on the plants' emissions, on the formation of biogenic SOA, and on SOA properties in order to understand possible climatic impacts. The Mediterranean region is expected to experience substantial climatic change in the next 50 years and the possible effects on biogenic emissions are yet unexplored. To address such issues, the effects of temperature and light intensity on Mediterranean Holm Oak VOC emissions, as well as on microphysical properties and chemical composition of the resulting SOA have been studied in the Jülich plant aerosol atmosphere chamber. We studied SOA formation from Holm Oak under conditions possibly simulating future climate warming. Monoterpenes dominate the VOC emissions from Holm Oak (97.5%) and temperature increase enhanced the emission strength and changed the emission pattern. Enhanced emissions lead to linearly enhanced SOA formation with a fractional mass yield of SOA (5.7±1%) independent of the detailed emission pattern. The particles are highly scattering with no absorption abilities. Their average hygroscopic growth factor was 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 were not dependent on the detailed emission pattern, in accordance with an invariant O/C ratio (0.57(+0.03/-0.1)) of the SOA as derived from high resolution aerosol mass spectrometry. The temperature increase for the plants essentially led to stronger VOC emissions with the SOA mass being linearly related to the VOC concentrations. However, the increase of Holm oak emissions with temperature (? 20 % per degree) was stronger than for Boreal tree species (? 10 % per degree). Increasing mean temperature in Mediterranean areas therefore has a stronger impact on VOC emissions than in areas with Boreal forests. Possible implications of the findings to climate-vegetation interactions are suggested.

Lang-Yona, Naama; Rudich, Yinon; Thomas, Mentel; Angela, Buchholz; Astrid, Kiendler-Scharr; Einhard, Kleist; Christian, Spindler; Ralf, Tillmann; Jürgen, Wildt

2010-05-01

274

Regional-scale modeling of secondary organic aerosol formation downwind from the DWH oil spill  

NASA Astrophysics Data System (ADS)

In response to the Deepwater Horizon (DWH) oil spill disaster in the Gulf of Mexico, the NOAA P3 aircraft performed two flights over the Gulf of Mexico during 8th and 10th of June 2010 with multiple flight legs around the DWH site to quantify the atmospheric impact of the oil spill. The measurements detected high concentrations of volatile organic compounds (VOCs) and organic aerosols (OA) downwind of the spill site. Spatial characteristics of the observed OA distribution indicated a moderate secondary organic aerosol (SOA) formation in narrow plumes coincident with high concentrations of aromatic VOCs, and also a much broader and larger SOA plume somewhat removed from the spill site. These patterns can qualitatively be explained by a dependence of VOC species volatility on the distance to the DWH spill site, and SOA yield differences associated with lower volatility (C12-C20 alkanes) versus higher volatility VOC (C7-C11 alkanes and aromatics) that comprise the bulk of the spilled oil reaching the surface. In order to test this SOA formation hypothesis the WRF-CHEM model has been applied to the Gulf of Mexico for the period of P3 aircraft operations. Modifications to the original WRF-Chem formulation include the addition of hexadecane (n-C16) within the gas-phase mechanism, and a new volatility basis set approach to simulate SOA formation using the most recent SOA yields from available literature. Emissions of NOx and C6-C11 VOC species are constrained from the P3 aircraft observations. The model has been run with different horizontal resolutions, and different emission scenarios for C12-C20 VOCs that were inferred from the composition of oil collected near the DWH. Model results for SOA and total PM2.5 aerosol are compared with the observations collected aboard the P3 aircraft, and coastal PM2.5 monitors positioned downwind of the DWH spill site, in order to test the veracity of the model formulation and help constrain the conceptual model of SOA formation from DWH outlined above.

Ahmadov, R.; McKeen, S. A.; Bahreini, R.; Brioude, J.; de Gouw, J. A.; Middlebrook, A. M.; Murphy, D. M.; Pollack, I. B.; Robinson, A. L.; Ryerson, T. B.; Trainer, M.; Warneke, C.

2010-12-01

275

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

276

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

277

Can Secondary Organic Aerosol Formed in Atmospheric Simulation Chamber Be Continuously Aging?  

Microsoft Academic Search

Recent smog chamber studies have found that the oxidative processing (i.e. aging) of organic aerosol affects the chemical and physical properties for both aromatic and terpene aerosol precursors. Evidence from laboratory experiments suggests that organic aerosol can be converted from a hydrophobic to a hydrophilic state with aging. Several possible chemical mechanisms have been proposed based on chamber studies from

L. Qi; S. Nakao; Q. Malloy; B. Warren; D. Cocker

2009-01-01

278

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

Microsoft Academic Search

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

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

2007-01-01

279

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

Microsoft Academic Search

Biogenic aerosols play important roles in atmo- spheric 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

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

2007-01-01

280

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

281

Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer  

NASA Astrophysics Data System (ADS)

Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used were Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients revealed a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: (1) shielding of inner monomers after particle consolidation or collapse with water uptake; (2) the lower case contribution of mass transfer through evaporation and condensation at high relative humidity (RH) to the usual heat transfer pathway for energy release by laser-heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

Lewis, K. A.; Arnott, W. P.; Moosmüller, H.; Chakrabarty, R. K.; Carrico, C. M.; Kreidenweis, S. M.; Day, D. E.; Malm, W. C.; Laskin, A.; Jimenez, J. L.; Ulbrich, I. M.; Huffman, J. A.; Onasch, T. B.; Trimborn, A.; Liu, L.; Mishchenko, M. I.

2009-11-01

282

Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer  

NASA Astrophysics Data System (ADS)

Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used are Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients reveal a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: 1. Shielding of inner monomers after particle consolidation or collapse with water uptake; 2. The contribution of mass transfer through evaporation and condensation at high relative humidity to the usual heat transfer pathway for energy release by laser-heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

Lewis, K. A.; Arnott, W. P.; Moosmüller, H.; Chakrabarty, R. K.; Carrico, C. M.; Kreidenweis, S. M.; Day, D. E.; Malm, W. C.; Laskin, A.; Jimenez, J. L.; Ulbrich, I. M.; Huffman, J. A.; Onasch, T. B.; Trimborn, A.; Liu, L.; Mishchenko, M. I.

2009-07-01

283

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

284

Ultrahigh mass resolution and accurate mass measurements as a tool to characterize oligomers in secondary organic aerosols.  

PubMed

Organic aerosols are a major fraction, often more than 50%, of the total atmospheric aerosol mass. The chemical composition of the total organic aerosol mass is poorly understood, although hundreds of compounds have been identified in the literature. High molecular weight compounds have recently gained much attention because this class of compounds potentially represents a major fraction of the unexplained organic aerosol mass. Here we analyze secondary organic aerosols, generated in a smog chamber from alpha-pinene ozonolysis with ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). About 450 compounds are detected in the mass range of m/z 200-700. The mass spectrum is clearly divided into a low molecular weight range (monomer) and a high molecular weight range, where dimers and trimers are distinguishable. Using the Kendrick mass analysis, the elemental composition of about 60% of all peaks could be determined throughout the whole mass range. Most compounds have high O:C ratios between 0.4 and 0.6. Small compounds (i.e., monomers) have a higher maximum O:C ratio than dimers and trimers, suggesting that condensation reactions with, for example, the loss of water are important in the oligomer formation process. A program developed in-house was used to determine exact mass differences between peaks in the monomer, dimer, and trimer mass range to identify potential monomer building blocks, which form the co-oligomers observed in the mass spectrum. A majority of the peaks measured in the low mass region of the spectrum (m/z < 300) is also found in the calculated results. For the first time the elemental composition of the majority of peaks over a wide mass range was determined using advanced data analysis methods for the analysis of ultra-high-resolution MS data. Possible oligomer formation mechanisms in secondary organic aerosols were investigated. PMID:17411016

Reinhardt, Alain; Emmenegger, Christian; Gerrits, Bertran; Panse, Christian; Dommen, Josef; Baltensperger, Urs; Zenobi, Renato; Kalberer, Markus

2007-04-06

285

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

286

AEROSOL GROWTH IN A STEADY-STATE, CONTINUOUS FLOW CHAMBER: APPLICATION TO STUDIES OF SECONDARY AEROSOL FORMATION  

EPA Science Inventory

An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The s...

287

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

288

Determination of the biogenic secondary organic aerosol fraction in the boreal forest by AMS and NMR measurements  

NASA Astrophysics Data System (ADS)

The study investigates the sources of fine organic aerosol (OA) in the boreal forest, based on measurements including both filter sampling (PM1) and online methods and carried out during a one-month campaign held in Hyytiälä, Finland, in spring 2007. Two aerosol mass spectrometers (Q-AMS, ToF-AMS) were employed to measure on-line air mass concentrations of major non-refractory aerosol species, while the water extracts of the filter samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy for organic functional group characterization of the polar organic fraction of the aerosol. AMS and NMR spectra were processed separately by non-negative factorization algorithms, in order to apportion the main components underlying the submicrometer organic aerosol composition and depict them in terms of both mass fragmentation patterns and functional group compositions. The NMR results supported the AMS speciation of oxidized organic aerosol (OOA) into two main fractions, which could be generally labelled as more and less oxidized organics. The more oxidized component was characterized by a mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR spectrum showing aromatic and aliphatic backbones highly substituted with oxygenated functional groups (carbonyls/carboxyls and hydroxyls). Such component, contributing on average 50 % of the OA mass throughout the observing period, was associated with pollution outbreaks from the Central Europe. The less oxidized component showed features consistent with less oxygenated aerosols and was enhanced in concomitance with air masses originating from the North-to-West sector, in agreement with previous investigations conducted at this site. NMR factor analysis was able to separate two distinct components under the less oxidized fraction of OA. One of these NMR-factors was associated to the formation of terrestrial biogenic secondary organic aerosol (BSOA), based on the comparison with spectral profiles obtained from laboratory experiments of terpenes photo-oxidation. The second NMR factor associated with western air masses was linked to biogenic marine sources, and was enriched in low-molecular weight aliphatic amines. Such findings provide evidence of at least two independent sources originating biogenic organic aerosols in Hyytiälä by oxidation and condensation mechanisms: reactive terpenes emitted by the boreal forest and compounds of marine origin, with the latter relatively more important when predominantly polar air masses reach the site. This study is an example of how spectroscopic techniques, such as proton NMR, can add functional group specificity for certain chemical features (like aromatics) of OA with respect to AMS. They can therefore be profitably be exploited to complement aerosol mass spectrometric measurements in organic source apportionment studies.

Finessi, E.; Decesari, S.; Paglione, M.; Giulianelli, L.; Carbone, C.; Gilardoni, S.; Fuzzi, S.; Saarikoski, S.; Raatikainen, T.; Hillamo, R.; Allan, J.; Mentel, Th. F.; Tiitta, P.; Laaksonen, A.; Petäjä, T.; Kulmala, M.; Worsnop, D. R.; Facchini, M. C.

2011-08-01

289

Impact of aftertreatment devices on primary emissions and secondary organic aerosol formation potential from in-use diesel vehicles: results from smog chamber experiments  

Microsoft Academic Search

Diesel particulate matter (DPM) is a significant source of aerosol in urban areas and has been linked to adverse health effects. Although newer European directives have introduced increasingly stringent standards for primary PM emissions, gaseous organics emitted from diesel cars can still lead to large amounts of secondary organic aerosol (SOA) in the atmosphere. Here we present results from smog

R. Chirico; P. F. Decarlo; M. F. Heringa; T. Tritscher; R. Richter; A. S. H. Prévôt; J. Dommen; E. Weingartner; G. Wehrle; M. Gysel; M. Laborde; U. Baltensperger

2010-01-01

290

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

291

Evaluation of factors controlling global secondary organic aerosol production from cloud processes  

NASA Astrophysics Data System (ADS)

Secondary organic aerosols (SOA) exert a significant influence on ambient air quality and regional climate. Recent field, laboratorial and modeling studies have confirmed that in-cloud processes contribute to a large fraction of SOA production with large space-time heterogeneity. This study evaluates the key factors that govern the production of cloud-process SOA (SOAcld) on a global scale based on the GFDL coupled chemistry-climate model AM3 in which full cloud chemistry is employed. The association between SOAcld production rate and six factors (i.e., liquid water content (LWC), total carbon chemical loss rate (TCloss), temperature, VOC/NOx, OH, and O3) is examined. We find that LWC alone determines the spatial pattern of SOAcld production, particularly over the tropical, subtropical and temperate forest regions, and is strongly correlated with SOAcld production. TCloss ranks the second and mainly represents the seasonal variability of vegetation growth. Other individual factors are essentially uncorrelated spatiotemporally to SOAcld production. We find that the rate of SOAcld production is simultaneously determined by both LWC and TCloss, but responds linearly to LWC and nonlinearly (or concavely) to TCloss. A parameterization based on LWC and TCloss can capture well the spatial and temporal variability of the process-based SOAcld formation (R2 = 0.5) and can be easily applied to global three dimensional models to represent the SOA production from cloud processes.

He, C.; Liu, J.; Carlton, A. G.; Fan, S.; Horowitz, L. W.; Levy, H., II; Tao, S.

2013-02-01

292

Synergy between secondary organic aerosols and long-range transport of polycyclic aromatic hydrocarbons.  

PubMed

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, as gas-phase PAH concentrations are depleted due to oxidation and dilution during LRT, 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 PAHs trapped inside highly viscous semisolid secondary organic aerosol (SOA) particles, during particle formation, are prevented from evaporation and shielded from oxidation. In contrast, surface-adsorbed PAHs rapidly evaporate leaving no trace. We find synergetic effects between hydrophobic organics and SOA - the presence of hydrophobic organics inside SOA particles drastically slows SOA evaporation to the point that it can almost be ignored, and the highly viscous SOA prevents PAH evaporation ensuring efficient LRT. The data show the assumptions of instantaneous reversible gas-particle equilibrium for PAHs and SOA are fundamentally flawed, providing an explanation for the persistent discrepancy between observed and predicted particle-bound PAHs. PMID:23098132

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

2012-11-07

293

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

SciTech Connect

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

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

2010-02-01

294

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

295

High-Resolution Mass Spectrometric Analysis of Secondary Organic Aerosol Produced by Ozonation of Limonene  

SciTech Connect

Secondary organic aerosol (SOA) particles formed from the ozone-initiated oxidation of limonene are characterized by high-resolution electrospray ionization mass spectrometry in both the positive and negative ion modes. The mass spectra reveal a large number of both monomeric (m/z < 300) and oligomeric (m/z > 300) products of oxidation. A combination of high resolving power (m/?m ~60,000) and Kendrick mass defect analysis makes it possible to unambiguously determine the composition for hundreds of individual compounds in SOA samples. Van Krevelen analysis shows that the SOA compounds are heavily oxidized, with average O:C ratios of 0.43 and 0.50 determined from the positive and negative ion mode spectra, respectively. An extended reaction mechanism for the formation of the first generation SOA molecular components is proposed. The mechanism includes known isomerization and addition reactions of the carbonyl oxide intermediates generated during the ozonation of limonene, and numerous isomerization pathways for alkoxy radicals resulting from the decomposition of unstable carbonyl oxides. The isomerization reactions yield numerous products with a progressively increasing number of alcohol and carbonyl groups, whereas C-C bond scission reactions in alkoxy radicals shorten the carbon chain. Together these reactions yield a large number of isomeric products with broadly distributed masses. A qualitative agreement is found between the number and degree of oxidation of the predicted and measured reaction products in the monomer range.

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

2008-02-08

296

Characterization of secondary organic aerosol generated from ozonolysis of ?-pinene mixtures  

NASA Astrophysics Data System (ADS)

In the atmosphere, multiple volatile organic compounds (VOCs) co-exist, and they can be oxidized concurrently and generate secondary organic aerosol (SOA). In this work, SOA is formed by the oxidation (in presence of excess ozone) of mixtures containing ?-pinene and other VOCs. The VOC mixtures were made so their composition approached a commercially-available ?-pinene-based essential oil, Siberian fir needle oil. The SOA products were sampled using filters, solvent extracted and analyzed by gas chromatography/mass spectrometry with trimethylsilyl derivatization. The individual product yields for SOA generated from ?-pinene changed upon the addition of other VOCs. An increase in concentration of non-reactive VOCs (bornyl acetate, camphene, and borneol) lead to a decrease in individual product yields of characteristic ?-pinene SOA products. Although these experiments were carried out under higher VOC and ozone concentrations in comparison to the atmosphere, this work suggests that the role of non-reactive VOCs should be explored in SOA products formation.

Amin, Hardik S.; Hatfield, Meagan L.; Huff Hartz, Kara E.

2013-03-01

297

Enhancement effect of relative humidity on the formation and regional respiratory deposition of secondary organic aerosol.  

PubMed

In this study, we investigated the effect of relative humidity (RH) on the formation of secondary organic aerosol (SOA) generated from the ozonolysis of d-limonene in an environmental chamber. The mass yield and the number concentration of SOA increased seven and eight times, respectively, when the RH increased from 18% to 82%. The measured total loss rates (apparent loss rates) of the number and mass concentration of SOA in the chamber ranged from 1.70 to 1.77 h(-1) and from 2.51 to 2.61 h(-1), respectively, at a controlled ventilation rate of 0.72±0.04 h(-1). The wall-deposition-loss-rate coefficient observed (1.00±0.02 h(-1)) was approximate to the estimated value based on Zhao and Wu's model which includes the factors of turbulence, Brownian diffusion, turbophoresis and surface roughness. According to the ICRP (International Commission on Radiological Protection) model, the inhaled SOA particles are deposited primarily in the alveoli of the lung. The integrated alveolar deposited dose of the mass (surface area) of SOA over 3h accounted for 74.0-74.8% (74.3-74.9%) of the total deposited dose at the investigated RH. Raising the RH resulted in the growth of SOA particle sizes and increment of the deposition dose but did not cause significant changes in the ratio of regional to the total respiratory deposition of SOA. PMID:21570180

Yu, Kuo-Pin; Lin, Chi-Chi; Yang, Shang-Chun; Zhao, Ping

2011-04-16

298

Formation of Secondary Organic Aerosol through Cloud Processing of Anthropogenic VOCs  

NASA Astrophysics Data System (ADS)

Cloud and fog processing of volatile organic carbon species (VOCs) can lead to the formation of secondary organic aerosol (SOA) mass. Biogenic species and their reaction products have received some attention recently but the present study addresses the potential of SOA formation in clouds from predominately anthropogenic VOCs, specifically benzene, toluene, ethylbenzenes, and xylenes (BTEX). Aqueous phase BTEX concentrations have been established in cloud water samples collected in Northern Arizona. While BTEX species contribute little (less than 1 percent) to the total organic carbon (TOC) in clouds, the aqueous concentrations are orders of magnitude higher than predicted by Henry’s law from ambient BTEX concentrations. Aqueous phase reactivity of BTEX has been investigated using a solar simulator set-up. BTEX reactivity studies with hydroxyl radical show that BTEX species degrade readily in deionized (18Mohm) water and simulated cloud water. The products of the reactions have been identified and quantified and include ring-retaining as well as ring-opening products. Most of the identified products have lower volatility than the parent VOC and will remain in the particle phase upon droplet evaporation. Therefore the laboratory studies show that cloud processing of anthropogenic VOCs can also lead to SOA mass formation by aqueous phase pathways.

Hutchings, J. W.; Herckes, P.

2009-12-01

299

Modeling the multiday evolution and aging of secondary organic aerosol during MILAGRO 2006.  

PubMed

In this study, we apply several recently proposed models to the evolution of secondary organic aerosols (SOA) and organic gases advected from downtown Mexico City at an altitude of ?3.5 km during three days of aging, in a way that is directly comparable to simulations in regional and global models. We constrain the model with and compare its results to available observations. The model SOA formed from oxidation of volatile organic compounds (V-SOA) when using a non-aging SOA parameterization cannot explain the observed SOA concentrations in aged pollution, despite the increasing importance of the low-NO(x) channel. However, when using an aging SOA parameterization, V-SOA alone is similar to the regional aircraft observations, highlighting the wide diversity in current V-SOA formulations. When the SOA formed from oxidation of semivolatile and intermediate volatility organic vapors (SI-SOA) is computed following Robinson et al. (2007) the model matches the observed SOA mass, but its O/C is ?2× too low. With the parameterization of Grieshop et al. (2009), the total SOA mass is ?2× too high, but O/C and volatility are closer to the observations. Heating or dilution cause the evaporation of a substantial fraction of the model SOA; this fraction is reduced by aging although differently for heating vs dilution. Lifting of the airmass to the free-troposphere during dry convection substantially increases SOA by condensation of semivolatile vapors; this effect is reduced by aging. PMID:21425791

Dzepina, Katja; Cappa, Christopher D; Volkamer, Rainer M; Madronich, Sasha; Decarlo, Peter F; Zaveri, Rahul A; Jimenez, Jose L

2011-03-22

300

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

Microsoft Academic Search

The sensitivity of secondary organic aerosol (SOA) concentration to changes in climate and emissions is investigated using a coupled global atmosphere-land model driven by the year 2100 IPCC A1B scenario predictions. The Community Atmosphere Model (CAM3) is updated with recent laboratory determined yields for SOA formation from monoterpene oxidation, isoprene photooxidation and aromatic photooxidation. Biogenic emissions of isoprene and monoterpenes

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

2008-01-01

301

Photodegradation of secondary organic aerosol generated from limonene oxidation by ozone studied with chemical ionization mass spectrometry  

Microsoft Academic Search

Photodegradation of secondary organic aerosol (SOA) prepared by ozone-initiated oxidation of D-limonene is studied with an action spectroscopy approach, which relies on detection of volatile photoproducts with chemical ionization mass-spectrometry as a function of the UV irradiation wavelength. Efficient photodegradation is observed for a broad range of ozone (0.1-300 ppm) and D-limonene (0.02-3 ppm) concentrations used in the preparation of

X. Pan; J. S. Underwood; J.-H. Xing; S. A. Mang; S. A. Nizkorodov

2009-01-01

302

Secondary organic aerosols from ozone-initiated reactions with emissions from wood-based materials and a “green” paint  

Microsoft Academic Search

This study examined the formation and growth of secondary organic aerosols (SOA) generated when ozone was added to a 1m3 glass chamber that contained either pine shelving, oriented strand board (OSB), beech boards, or beach boards painted with an “eco” paint. The experiments were conducted at close to real-world conditions; the chamber was ventilated at ?0.5 air changes\\/h; the loadings

J. Toftum; S. Freund; T. Salthammer; C. J. Weschler

2008-01-01

303

Physical parameters effect on ozone-initiated formation of indoor secondary organic aerosols with emissions from cleaning products  

Microsoft Academic Search

The effect of air exchange rate (ACH), temperature (T), and relative humidity (RH) on the formation of indoor secondary organic aerosols (SOAs) through ozonolysis of biogenic organic compounds (BVOCs) emitted from floor cleaner was investigated in this study. The total particle count (with Dp of 6–225nm) was up to 1.2×103#cm?3 with ACH of 1.08h?1, and it became much more significant

Yu Huang; Kin Fai Ho; Steven Sai Hang Ho; Shun Cheng Lee; P. S. Yau; Yan Cheng

2011-01-01

304

Formation of Nitrogen and Sulfur-Containing Light-Absorbing Compounds Accelerated by Evaporation of Water from Secondary Organic Aerosols  

Microsoft Academic Search

Aqueous extracts of secondary organic aerosols (SOA) generated from the ozonolysis of dlimonene were subjected to dissolution, evaporation, and re-dissolution in the presence and absence of ammonium sulfate (AS). Evaporation with AS at pH 4-9 produced chromophores that were stable with respect to hydrolysis and had a distinctive absorption band at 500 nm. Evaporation accelerated the rate of chromophore formation

Tran B. Nguyen; Paula B. Lee; Katelyn M. Updyke; David L. Bones; Julia Laskin; Alexander Laskin; Sergey Nizkorodov

2012-01-01

305

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

EPA Science Inventory

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

306

SEASONAL AND REGIONAL VARIATIONS OF PRIMARY AND SECONDARY ORGANIC AEROSOLS OVER THE CONTINENTAL UNITED STATES: OBSERVATION-BASED ESTIMATES AND MODEL EVALUATION  

EPA Science Inventory

Due to the lack of an analytical technique for directly quantifying the atmospheric concentrations of primary (OCpri) and secondary (OCsec) organic carbon aerosols, different indirect methods have been developed to estimate their concentrations. In this stu...

307

EFFECT OF RELATIVE HUMIDITY ON THE CHEMICAL COMPOSITION OF SECONDARY ORGANIC AEROSOL FORMED FROM REACTIONS OF 1-TETRADECENE AND O3. (R826235)  

EPA Science Inventory

The chemical composition of secondary organic aerosol formed in an environmental chamber from ozonolysis of 1-tetradecene in humid and dry air was determined using a thermal desorption particle beam mass spectrometer (TDPBMS). The major products are ...

308

Change in global aerosol composition since preindustrial times  

NASA Astrophysics Data System (ADS)

To elucidate human induced changes of aerosol load and composition in the atmosphere, a coupled aerosol and gas-phase chemistry transport model of the troposphere and lower stratosphere has been used. This is the first 3-d modeling study that focuses on aerosol chemical composition change since preindustrial times considering the secondary organic aerosol formation together with all other main aerosol components including nitrate. In particular, we evaluate non-sea-salt sulfate (nss-SO4=), ammonium (NH4+), nitrate (NO3-), black carbon (BC), sea-salt, dust, primary and secondary organics (POA and SOA) with a focus on the importance of secondary organic aerosols. Our calculations show that the aerosol optical depth (AOD) has increased by about 21% since preindustrial times. This enhancement of AOD is attributed to a rise in the atmospheric load of BC, nss-SO4=, NO3-, POA and SOA by factors of 3.3, 2.6, 2.7, 2.3 and 1.2, respectively, whereas we assumed that the natural dust and sea-salt sources remained constant. The nowadays increase in carbonaceous aerosol loading is dampened by a 34-42% faster conversion of hydrophobic to hydrophilic carbonaceous aerosol leading to higher removal rates. These changes between the various aerosol components resulted in significant modifications of the aerosol chemical composition. The relative importance of the various aerosol components is critical for the aerosol climatic effect, since atmospheric aerosols behave differently when their chemical composition changes. According to this study, the aerosol composition changed significantly over the different continents and with height since preindustrial times. The presence of anthropogenically emitted primary particles in the atmosphere facilitates the condensation of the semi-volatile species that form SOA onto the aerosol phase, particularly in the boundary layer. The SOA burden that is dominated by the natural component has increased by 24% while its contribution to the AOD has increased by 11%. The increase in oxidant levels and preexisting aerosol mass since preindustrial times is the reason of the burden change, since emissions have not changed significantly. The computed aerosol composition changes translate into about 2.5 times more water associated with non sea-salt aerosol. Additionally, aerosols contain 2.7 times more inorganic components nowadays than during the preindustrial times. We find that the increase in emissions of inorganic aerosol precursors is much larger than the corresponding aerosol increase, reflecting a non-linear atmospheric response.

Tsigaridis, K.; Krol, M.; Dentener, F. J.; Balkanski, Y.; Lathière, J.; Metzger, S.; Hauglustaine, D. A.; Kanakidou, M.

2006-06-01

309

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

310

Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols  

Microsoft Academic Search

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination

N. Jendoubi; F. Broust; J. M. Commandre; G. Mauviel; M. Sardin; J. Lédé

2011-01-01

311

Inorganic, organic and macromolecular components of fine aerosol in different areas of Europe in relation to their water solubility  

NASA Astrophysics Data System (ADS)

A chemical mass balance of fine aerosol (<1.5 ?m AED) collected at three European sites was performed with reference to the water solubility of the different aerosol classes of components. The sampling sites are characterised by different pollution conditions and aerosol loading in the air. Aspvreten is a background site in central Sweden, K-puszta is a rural site in the Great Hungarian Plain and San Pietro Capofiume is located in the polluted Po Valley, northern Italy. The average fine aerosol mass concentration was 5.9 ?g m -3 at the background site Aspvreten, 24 ?g m -3 at the rural K-puszta and 38 ?g m -3 at the polluted site San Pietro Capofiume. However, a similarly high soluble fraction of the aerosol (65-75%) was measured at the three sites, while the percentage of water soluble organic species with respect to the total soluble mass was much higher at the background site (ca. 50%) than at the other two sites (ca. 25%). A very high fraction (over 70%) of organic compounds in the aerosol consisted of polar species. The presence of water soluble macromolecular compounds was revealed in the samples from K-puszta and San Pietro Capofiume. At both sites these species accounted for between ca. 20-50% of the water soluble organic fraction. The origin of the compounds was tentatively attributed to biomass combustion.

Zappoli, S.; Andracchio, A.; Fuzzi, S.; Facchini, M. C.; Gelencsér, A.; Kiss, G.; Krivácsy, Z.; Molnár, Á.; Mészáros, E.; Hansson, H.-C.; Rosman, K.; Zebühr, Y.

312

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

313

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

314

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

315

[Forming potential of secondary organic aerosols and sources apportionment of VOCs in autumn of Shanghai, China].  

PubMed

A continuous measurement was conducted in urban area of Shanghai from 1stSeptember to 21st November, 2011. The mass concentration of PM2.5 and the mixing ratio of VOCs were obtained during the period. Four pollution episodes were observed: PD1 (20th-23th September), PD2 (5th-9th October), PD3 (13rd - 18th October), PD4 (10th - 14th November). The average mass concentrations of PM2.5 were (45+/-16), (76+/-46), (57+/-36) and (122+/-92) microg.m-3, respectively. The mixing ratio of VOCs were (30.87+/-30.77) x10(-9), (32.09+/-30.69) x10(-)9, (34.04+/-28.13) x10(-9) and (44.27+/-31.58) x10(-9). Alkane, alkene and aromatic hydrocarbons accounted for 53. 58% , 27. 89% , and 10. 96% of the total VOCs, respectively. The OH radical loss rate (LOH) and the ozone formation potential (OFP) were applied to assess the chemical reactivity of VOCs, the results showed that the alkenes and aromatics were the most important contributors to LOH and OFP in the atmosphere in the urban area of Shanghai, in autumn. Fractional aerosol coefficients (FAC) and the ratio of organic carbon to element carbon (OC/EC) were used to estimate the potential formation of secondary organic aerosols (SOA) in Shanghai, the SOA concentration values obtained by the two methods were 1.43 microg.m-3 and 4.54 microg.m-3, respectively. The value predicted by OC/EC was significantly higher, which was mainly due to the low amount of SOA precursors measured in this study. The aromatics were not only the most important contributors to OFP, but also important SOA precursors. By applying the positive matrix factorization (PMF) model, six major sources were extracted to identify the sources of VOCs in autumn in Shanghai, including vehicle exhaust (24.30%), incomplete combustion (17.39%), fuel evaporation (16.01%) , LPG/NG leakage (15.21%) , petrochemical industry (14.00% ), and paint/solvent usage (13.09%). Vehicle exhaust and paint/solvent usage contain abundant aromatics species which are the most important contributors to OFP and important SOA precursors. The above two sources contributed 37.39% of the total VOCs concentration. Hence, these sources should be listed as priority of air pollution control strategy for Shanghai in future. PMID:23668105

Wang, Qian; Chen, Chang-Hong; Wang, Hong-Li; Zhou, Min; Lou, Sheng-Rong; Qiao, Li-Ping; Huang, Cheng; Li, Li; Su, Lei-Yan; Mu, Ying-Ying; Chen, Yi-Ran; Chen, Ming-Hua

2013-02-01

316

Secondary organic aerosol formation from low-NO(x) photooxidation of dodecane: evolution of multigeneration gas-phase chemistry and aerosol composition.  

PubMed

The extended photooxidation of and secondary organic aerosol (SOA) formation from dodecane (C(12)H(26)) under low-NO(x) conditions, such that RO(2) + HO(2) chemistry dominates the fate of the peroxy radicals, is studied in the Caltech Environmental Chamber based on simultaneous gas and particle-phase measurements. A mechanism simulation indicates that greater than 67% of the initial carbon ends up as fourth and higher generation products after 10 h of reaction, and simulated trends for seven species are supported by gas-phase measurements. A characteristic set of hydroperoxide gas-phase products are formed under these low-NO(x) conditions. Production of semivolatile hydroperoxide species within three generations of chemistry is consistent with observed initial aerosol growth. Continued gas-phase oxidation of these semivolatile species produces multifunctional low volatility compounds. This study elucidates the complex evolution of the gas-phase photooxidation chemistry and subsequent SOA formation through a novel approach comparing molecular level information from a chemical ionization mass spectrometer (CIMS) and high m/z ion fragments from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Combination of these techniques reveals that particle-phase chemistry leading to peroxyhemiacetal formation is the likely mechanism by which these species are incorporated in the particle phase. The current findings are relevant toward understanding atmospheric SOA formation and aging from the "unresolved complex mixture," comprising, in part, long-chain alkanes. PMID:22424261

Yee, Lindsay D; Craven, Jill S; Loza, Christine L; Schilling, Katherine A; Ng, Nga Lee; Canagaratna, Manjula R; Ziemann, Paul J; Flagan, Richard C; Seinfeld, John H

2012-04-10

317

Detection of nitrooxypolyols in secondary organic aerosol formed from the photooxidation of conjugated dienes under high-NO x conditions  

NASA Astrophysics Data System (ADS)

2-Methyltetrols produced by the oxidation of isoprene have been recently found to contribute toward the formation of atmospheric secondary organic aerosol (SOA). However, the oxidation mechanism relevant to the formation of these polyols has not been completely understood. In this study, the photooxidation of four conjugated dienes (isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene and 2,4-hexadiene) in the presence of 0.2-1 ppmv NO was examined by a series of laboratory experiments, and the polyols, organic acids and nitric acid in an aqueous solution of the resulting SOA were analysed by using ion-exclusion liquid chromatography/mass spectrometry (LC-MS). In the experiments performed using isoprene, 2-methyltetrols (comprising 0.5-2% of aerosol mass), methylnitrooxybutanetriols (comprising 1-7% of aerosol mass), methyldinitrooxybutanediols (comprising 0.3-8% of aerosol mass) and nitric acid (comprising 4-9% of aerosol mass) were found in the aqueous solution of the SOA samples. Three days after the extraction, the concentrations of nitrooxypolyols (i.e. methylnitrooxybutanetriols and methyldinitrooxybutanediols) decreased, whereas the concentrations of polyols and nitric acid increased. Similar results were obtained for all the four dienes. Nitrooxypolyols, which are produced by the gas-phase oxidation of dienes in the presence of NO x, contribute toward the SOA formation, and these compounds can decompose to polyols and nitric acid in an aqueous solution. The polyols and the nitric acid present in the aqueous solution are hydrolysis products, and not real constituents of aerosol. The direct gas-phase formation of polyols from the diene oxidation is suppressed in the presence of NO x.

Sato, Kei

318

Large contribution of water-insoluble secondary organic aerosols in the region of Paris (France) during wintertime  

NASA Astrophysics Data System (ADS)

Near real-time measurements of carbonaceous aerosols were performed in fine aerosols for a 10-day period during winter at a suburban site of Paris (France). These measurements were performed using an OCEC Sunset Field instrument for elemental carbon (EC) and organic carbon (OC); a Particle-Into-Liquid-Sampler coupled with a Total Organic Carbon (PILS-TOC) instrument for water-soluble OC (WSOC); and a 7-? aethalometer for absorption. A successful comparison was performed with filter sampling performed in parallel for EC, OC, and WSOC, providing further confidence on the results obtained by the online analyzers. A modified version of the aethalometer model was used to derive hourly concentrations of 3 organic aerosol (OA) sources: fossil fuel, wood burning, and secondary. This source apportionment was validated for primary OA (fossil fuel, wood burning) using time-resolved measurements of specific tracers (including levoglucosan, water-soluble potassium and methanol for wood burning) and showed that secondary organic aerosols (SOA) were the most abundant OA species during our study. Water-soluble properties of these different OA sources were investigated from the reconstruction of experimentally determined water-soluble/insoluble OC. About 23% of WSOC was found to be of a secondary (photochemical) origin. A large fraction of SOA was assigned as water-insoluble and could originate from semi-volatile primary OA from wood burning and/or anthropogenic emissions. These results have been obtained at a typical suburban site in France and may be then representative of a larger European area. They bring new light on the commonly accepted idea that SOA is mainly water-soluble.

Sciare, Jean; D'Argouges, Odile; Sarda-EstèVe, Roland; Gaimoz, CéCile; Dolgorouky, Cristina; Bonnaire, Nicolas; Favez, Olivier; Bonsang, Bernard; Gros, ValéRie

2011-11-01

319

A study of the ability of pure secondary organic aerosol to act as cloud condensation nuclei  

Microsoft Academic Search

Submicron atmospheric particles that serve as cloud condensation nuclei (CCN) at low super-saturations are important for quantifying the effect of aerosols on cloud properties and global climate. In this study, we investigate experimentally the ability of model submicron aerosols consisting of pure organic species to become CCN at typical atmospheric supersaturations.The CCN activity of glutaric acid, adipic acid and dyoctylphthalate

Celia N. Cruz; Spyros N. Pandis

1997-01-01

320

Laboratory Studies of Heterogeneous Reactions of HO2 Radical with Inorganic Aerosol Particles under the Ambient Conditions  

NASA Astrophysics Data System (ADS)

The HO2 uptake coefficient for aerosol particles ((NH4)2SO4 and NaCl) under ambient conditions (760Torr and 296K) was measured using an aerosol flow tube(AFT) coupled with a chemical conversion/laser-induced fluorescence(CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere(~108 molecules cm-3). HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position dependent profiles of LIF intensity were measured as a function of aerosol concentration at various relative humilities(RH). The uptake coefficients of dry aerosol (NaCl and (NH4)2SO4) particles were < 0.05, while the uptake coefficients of wet particles of NaCl and (NH4)2SO4 were estimated to be 0.10 and 0.15, respectively, which suggested that heterogeneous loss was enhanced by the particle containing water. To estimate the contribution of heterogeneous loss of HO2 by aerosol, the diurnal variation of HO2 using a box-model calculation was demonstrated. As a result, the daytime maximum concentrations of HO2 were changed to 95 and 70 %, relative to an absence of heterogeneous loss for marine and urban areas, respectively.

Taketani, F.; Kanaya, Y.; Akimoto, H.

2007-12-01

321

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

NASA Astrophysics Data System (ADS)

Quasi-Lagrangian aircraft measurements above the Yellow Sea, East China Sea, and Sea of Japan revealed synoptic-scale secondary aerosol formation and condensational growth during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) and Transport and Chemical Evolution over the Pacific (TRACE-P) experiment. This occurred in the presence of pollution and mineral dust aerosol surface areas as high as 1200 ?m2 cm-3. Concentrations of sulfuric acid generally appeared insufficient for binary nucleation, but observations, models, and theory are consistent with a ternary nucleation mechanism involving H2SO4-H2O-NH3. Growth rates of ˜2 nm h-1 can be explained by the condensation of sulfuric acid at a rate of 2 ± 1 × 106 molecules cm-3 s-1. Aerosol volatility suggested increasing neutralization of the aerosol during growth. Size distribution measurements suggest that weak (mean condensation nuclei (CN) 3-13 nm ? 500 cm-3) new particle production was a common occurrence in the region. However, new particle production was enhanced by ˜1 order of magnitude (mean CN 3-13 nm ? 5000 cm-3) in postfrontal air masses associated with offshore flow during cloud-free conditions. Fog and clouds appear to be regionally important in modulating nucleation events through scavenging of secondary aerosol and through depletion of gas-phase precursors through enhanced heterogeneous chemistry. Our results indicate that only 10-30% of the total aerosol population consists of aged secondary aerosols after ˜2 days of transport from source regions. In spite of their high production during nucleation events, secondary aerosols advected out over the Pacific Ocean will have a small impact upon indirect forcing and a negligible impact upon direct forcing compared to primary aerosol emissions and the species that condense upon them.

McNaughton, Cameron S.; Clarke, Antony D.; Howell, Steven G.; Moore, Kenneth G.; Brekhovskikh, Vera; Weber, Rodney J.; Orsini, Douglas A.; Covert, David S.; Buzorius, Gintautas; Brechtel, Fred J.; Carmichael, Gregory R.; Tang, Youhua; Eisele, Fred L.; Mauldin, R. Lee; Bandy, Alan R.; Thornton, Donald C.; Blomquist, Byron

2004-10-01

322

Partitioning phase preference for secondary organic aerosol in an urban atmosphere  

PubMed Central

Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular matter. The impact of particular matter on both human health and global climate has long been recognized. Despite its importance, there are still many unanswered questions regarding the formation and evolution of SOA in the atmosphere. This study uses a modeling approach to understand the preferred partitioning behavior of SOA species into aqueous or organic condensed phases. More specifically, this work uses statistical analyses of approximately 24,000 data values for each variable from a state of the art 3D airshed model. Spatial and temporal distributions of fractions of SOA residing in the aqueous phase (fAQ) in the South Coast Air Basin of California are presented. Typical values of fAQ within the basin near the surface range from 5 to 80%. Results show that the likelihood of large fAQ values is inversely proportional to the total SOA loading. Analysis of various meteorological parameters indicates that large fAQ values are predicted because modeled aqueous-phase SOA formation is less sensitive than that of organic-phase SOA to atmospheric conditions that are not conducive to SOA formation. There is a diurnal variation of fAQ near the surface: It tends to be larger during daytime hours than during nighttime hours. Results also indicate that the largest fAQ values are simulated in layers above ground level at night. In summary, one must consider SOA in both organic and aqueous phases for proper regional and global SOA budget estimation.

Chang, Wayne L.; Griffin, Robert J.; Dabdub, Donald

2010-01-01

323

Oligomerization as a potential mechanism for Secondary Organic Aerosol (SOA) formation in clouds  

NASA Astrophysics Data System (ADS)

Electrospray ionization - mass spectrometry (ESI-MS) has been used to investigate oligomer formation in dark chamber experiments designed to study the polymerization conditions of common atmospheric photooxidation products without photochemical action. Methylglyoxal has been selected as the monomer considering, it is a gas-phase product from the atmospheric oxidation of isoprene and terpenes (biogenic sources) as well as of aromatic compounds (anthropogenic sources). Aqueous-phase oligomer formation of methylglyoxal has been investigated in a simulated cloud matrix, under dark conditions in view of its short life time (~1.6 hrs). A mechanistic pathway for the growth of oligomers via aldol condensation under cloud conditions and in the absence of UV-light and the OH radical is proposed here for the first time. Soluble oligomers (n=1-12) formed in the course of acid-catalyzed aldol condensation have been detected and identified by positive and negative ion ESI-MS, while their relative abundance is estimated from the full-scan mass spectra. In particular, oligomer abundances and their adduct formation was considered with special emphasis on the structural elucidation of these oligomers and their corresponding adduct products. The oligomer series starts with a ?-hydroxy ketone via aldol condensation and oligomers are formed by multiple addition of C3H4O2 units (72 Da) to the parent ?-hydroxy ketone. MS2 ion trap experiments have been performed to structurally characterize the oligomers. Oligomers could form under conditions encountered in clouds even at micromolar concentrations and thus could significantly result in secondary organic aerosol (SOA) after cloud droplet evaporation. Therefore, it is proposed that oligomer formation does not only occur during droplet evaporation when the concentrations of products increase but could as well be an in-cloud process and substantially enhance in-cloud SOA yields.

Yasmeen, F.; Sauret, N.; Claeys, M.; Maria, P. C.; Massi, L.

2009-04-01

324

Modeling the Multiday Evolution and Aging of Secondary Organic Aerosol During MILAGRO 2006  

NASA Astrophysics Data System (ADS)

In this study we apply several recently-proposed models to the evolution of secondary organic aerosols (SOA) and organic gases advected from downtown Mexico City at an altitude of ~3.5 km during three days of aging. We constrain the model with and compare its results to available observations. The model SOA formed from oxidation of volatile organic compounds (V-SOA) alone cannot explain the observed mass loadings in aged pollution. Over the regional scale ~5% of the model SOA is due to the low-NOx aromatic V-SOA pathway, which has a higher yield and produces comparably “low-volatility” species that remain in the particle phase as dilution proceeds and more volatile components evaporate. The model SOA formed from oxidation of both semivolatile and intermediate volatility organic vapors (SI-SOA) accounts for most of the predicted SOA mass concentration. With the SI-SOA parameterization of Robinson et al. (2007) the model matches the observed SOA mass, but its O/C is too low by a factor of 2. With the parameterization of Grieshop et al. (2009) the total SOA mass is overpredicted by a factor of ~2 but O/C and volatility are much closer to the observations. Heating or dilution of the air results in evaporation of a substantial fraction of the model SOA; this fraction is reduced by aging although differently for heating vs. dilution. Finally, lifting of the airmass to the free-troposphere during dry convection results in a substantial increase of SOA by condensation of semivolatile vapors, with this effect being reduced by aging.

Dzepina, K.; Cappa, C. D.; Volkamer, R.; Madronich, S.; Decarlo, P. F.; Zaveri, R. A.; Jimenez, J. L.

2010-12-01

325

The impact of recirculation, ventilation and filters on secondary organic aerosols generated by indoor chemistry  

NASA Astrophysics Data System (ADS)

This study examined the impact of recirculation rates (7 and 14 h -1), ventilation rates (1 and 2 h -1), and filtration on secondary organic aerosols (SOAs) generated by ozone of outdoor origin reacting with limonene of indoor origin. Experiments were conducted within a recirculating air handling system that serviced an unoccupied, 236 m 3 environmental chamber configured to simulate an office; either no filter, a new filter or a used filter was located downstream of where outdoor air mixed with return air. For otherwise comparable conditions, the SOA number and mass concentrations at a recirculation rate of 14 h -1 were significantly smaller than at a recirculation rate of 7 h -1. This was due primarily to lower ozone concentrations, resulting from increased surface removal, at the higher recirculation rate. Increased ventilation increased outdoor-to-indoor transport of ozone, but this was more than offset by the increased dilution of SOA derived from ozone-initiated chemistry. The presence of a particle filter (new or used) strikingly lowered SOA number and mass concentrations compared with conditions when no filter was present. Even though the particle filter in this study had only 35% single-pass removal efficiency for 100 nm particles, filtration efficiency was greatly amplified by recirculation. SOA particle levels were reduced to an even greater extent when an activated carbon filter was in the system, due to ozone removal by the carbon filter. These findings improve our understanding of the influence of commonly employed energy saving procedures on occupant exposures to ozone and ozone-derived SOA.

Fadeyi, M. O.; Weschler, C. J.; Tham, K. W.

326

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

NASA Astrophysics Data System (ADS)

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

Pan, Xiang

327

Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol  

PubMed Central

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort focused on finding additional SOA sources but leaving the fundamental assumptions used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets, forming instantaneous reversible equilibrium with gas phase. Further, they ignore the effects of adsorption of spectator organic species during SOA formation on SOA properties and fate. Using accurate and highly sensitive experimental approach for studying evaporation kinetics of size-selected single SOA particles, we characterized room-temperature evaporation kinetics of laboratory-generated ?-pinene SOA and ambient atmospheric SOA. We found that even when gas phase organics are removed, it takes ?24 h for pure ?-pinene SOA particles to evaporate 75% of their mass, which is in sharp contrast to the ?10 min time scale predicted by current kinetic models. Adsorption of “spectator” organic vapors during SOA formation, and aging of these coated SOA particles, dramatically reduced the evaporation rate, and in some cases nearly stopped it. Ambient SOA was found to exhibit evaporation behavior very similar to that of laboratory-generated coated and aged SOA. For all cases studied in this work, SOA evaporation behavior is nearly size-independent and does not follow the evaporation kinetics of liquid droplets, in sharp contrast with model assumptions. The findings about SOA phase, evaporation rates, and the importance of spectator gases and aging all indicate that there is need to reformulate the way SOA formation and evaporation are treated by models.

Vaden, Timothy D.; Imre, Dan; Beranek, Josef; Shrivastava, Manish; Zelenyuk, Alla

2011-01-01

328

Source apportionment of secondary organic aerosol during a severe photochemical smog episode  

NASA Astrophysics Data System (ADS)

The UCD/CIT air quality model was modified to predict source contributions to secondary organic aerosol (SOA) by expanding the Caltech Atmospheric Chemistry Mechanism to separately track source apportionment information through the chemical reaction system as precursor species react to form condensable products. The model was used to predict source contributions to SOA in Los Angeles from catalyst-equipped gasoline vehicles, non-catalyst equipped gasoline vehicles, diesel vehicles, combustion of high sulfur fuel, other anthropogenic sources, biogenic sources, and initial/boundary conditions during the severe photochemical smog episode that occurred on 9 September 1993. Gasoline engines (catalyst+non-catalyst equipped) were found to be the single-largest anthropogenic source of SOA averaged over the entire model domain. The region-wide 24-h average concentration of SOA produced by gasoline engines was predicted to be 0.34 ?g m -3 with a maximum 24-h average concentration of 1.81 ?g m -3 downwind of central Los Angeles. The region-wide 24-h average concentration of SOA produced by diesel engines was predicted to be 0.02 ?g m -3, with a maximum 24-h average concentration of 0.12 ?g m -3 downwind of central Los Angeles. Biogenic sources are predicted to produce a region-wide 24-h average SOA value of 0.16 ?g m -3, with a maximum 24-h average concentration of 1.37 ?g m -3 in the less-heavily populated regions at the northern and southern edges of the air basin (close to the biogenic emissions sources). SOA concentrations associated with anthropogenic sources were weakly diurnal, with slightly lower concentrations during the day as mixing depth increased. SOA concentrations associated with biogenic sources were strongly diurnal, with higher concentrations of aqueous biogenic SOA at night when relative humidity (RH) peaked and little biogenic SOA formation during the day when RH decreased.

Kleeman, Michael J.; Ying, Qi; Lu, Jin; Mysliwiec, Mitchel J.; Griffin, Robert J.; Chen, Jianjun; Clegg, Simon

329

High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene.  

PubMed

Chemical composition of secondary organic aerosol (SOA) formed from the ozone-initiated oxidation of limonene is characterized by high-resolution electrospray ionization mass spectrometry in both positive and negative ion modes. The mass spectra reveal a large number of both monomeric (m/z < 300) and oligomeric (m/z > 300) condensed products of oxidation. A combination of high resolving power (m/Deltam approximately 60,000) and Kendrick mass defect analysis makes it possible to unambiguously determine the molecular composition of hundreds of individual compounds in SOA samples. Van Krevelen analysis shows that the SOA compounds are heavily oxidized, with average O : C ratios of 0.43 and 0.50 determined from the positive and negative ion mode spectra, respectively. A possible reaction mechanism for the formation of the first generation SOA molecular components is considered. The discussed mechanism includes known isomerization and addition reactions of the carbonyl oxide intermediates generated during the ozonation of limonene. In addition, it includes isomerization and decomposition pathways for alkoxy radicals resulting from unimolecular decomposition of carbonyl oxides that have been disregarded by previous studies. The isomerization reactions yield numerous products with a progressively increasing number of alcohol and carbonyl groups, whereas C-C bond scission reactions in alkoxy radicals shorten the carbon chain. Together these reactions yield a large number of isomeric products with broadly distributed masses. A qualitative agreement is found between the number and degree of oxidation of the predicted and measured reaction products in the monomer product range. PMID:18259641

Walser, Maggie L; Desyaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A

2007-12-10

330

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

331

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

332

Effects of Precursor Concentration and Acidic Sulfate in Aqueous Glyoxal-OH Radical Oxidation and Implications for Secondary Organic Aerosol  

PubMed Central

Previous experiments demonstrated that aqueous OH radical oxidation of glyoxal yields low-volatility compounds. When this chemistry takes place in clouds and fogs, followed by droplet evaporation (or if it occurs in aerosol water), the products are expected to remain partially in the particle phase, forming secondary organic aerosol (SOA). Acidic sulfate exists ubiquitously in atmospheric water and has been shown to enhance SOA formation through aerosol phase reactions. In this work, we investigate how starting concentrations of glyoxal (30?3000 ?M) and the presence of acidic sulfate (0?840 ?M) affect product formation in the aqueous reaction between glyoxal and OH radical. The oxalic acid yield decreased with increasing precursor concentrations, and the presence of sulfuric acid did not alter oxalic acid concentrations significantly. A dilute aqueous chemistry model successfully reproduced oxalic acid concentrations, when the experiment was performed at cloud-relevant concentrations (glyoxal <300 ?M), but predictions deviated from measurements at increasing concentrations. Results elucidate similarities and differences in aqueous glyoxal chemistry in clouds and in wet aerosols. They validate for the first time the accuracy of model predictions at cloud-relevant concentrations. These results suggest that cloud processing of glyoxal could be an important source of SOA.

2009-01-01

333

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

2012-03-02

334

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

335

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

336

Secondary Organic Aerosol Produced from Non-Measured Hydrocarbons Downwind from the Oil Spill in the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

An extensively instrumented NOAA WP-3D research aircraft made airborne measurements of the gaseous and aerosol composition of air over the Deepwater Horizon (DWH) oil spill that occurred in April-July of 2010 in the Gulf of Mexico. A narrow plume of hydrocarbons was observed downwind from DWH that is attributed to the evaporation of fresh oil on the sea surface. A much wider plume of organic aerosol (OA) was attributed to secondary (SOA) formation from unmeasured, less volatile hydrocarbons that were emitted from a wider area around DWH. These observations provide compelling evidence for the importance of SOA formation from less volatile hydrocarbons, which has been proposed as a significant source of OA in the atmosphere.

de Gouw, J. A.; Middlebrook, A. M.; Warneke, C.; Ahmadov, R.; Atlas, E. L.; Bahreini, R.; Blake, D. R.; Brock, C. A.; Brioude, J.; Fahey, D. W.; Fehsenfeld, F. C.; Gao, R.; Holloway, J. S.; Lueb, R.; McKeen, S. A.; Meagher, J. F.; Murphy, D. M.; Parrish, D. D.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Robinson, A. L.; Ryerson, T. B.; Schwarz, J. P.; Spackman, J. R.; Srinivasan, A.; Watts, L.

2010-12-01

337

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

NASA Astrophysics Data System (ADS)

Particulate matter (PM) is solid particles and liquid droplets of complex composition suspended in the atmosphere. In 1997, the National Ambient Air Quality Standards (NAAQS) for PM was modified to include new standards for fine particulate (particles smaller than 2.5mum, PM2.5) because of their association with adverse health effects, mortality and visibility reduction. Fine PM may also have large impacts on the global climate. Chemically, fine particulate is a complex mixture of organic and inorganic material, from both natural and anthropogenic sources. A large fraction of PM2.5 is organic. The first objective was to investigate heterogeneous oxidation of condensed-phase molecular markers for two major organic source categories, meat-cooking emissions and motor vehicle exhaust. Effective reaction rate constants of key molecular markers were measured over a range of atmospherically relevant experimental conditions, including a range of concentrations and relative humidities, and with SOA condensed on the particles. Aerosolized meat grease was reacted with ozone to investigate the oxidation of molecular markers for meat-cooking emissions. Aerosolized motor oil, which is chemically similar to vehicle exhaust aerosol and contains the molecular markers used in source apportionment, was reacted with the hydroxyl radical (OH) to investigate oxidation of motor vehicle molecular markers. All molecular markers of interest - oleic acid, palmitoleic acid, and cholesterol for meat-cooking emissions, and hopanes and steranes for vehicle exhaust - reacted at rates that are significant for time scales on the order of days assuming typical summertime oxidant concentrations. Experimental conditions influenced the reaction rate constants. For both systems, experiments conducted at high relative humidity (RH) had smaller reaction rate constants than those at low RH. SOA coating slowed the reaction rate constants for meat-cooking markers, but had no effect on the oxidation of vehicle markers. Aerosol composition is a key influence on reaction rate constants, perhaps more significant than external influences. Alkenoic acid concentrations in the meat grease particles appear to influence cholesterol oxidation rates. Also, the reaction rate constants for new motor oil were faster than those of the more viscous used motor oil. The measured reaction rate constants were used to oxidize source profiles that were subsequently run in the Chemical Mass Balance (CMB) model. Oxidizing the molecular markers in the meat-cooking profile led to unrealistically high meat-cooking aerosol contributions to the total organic carbon (OC), often more than 100%. This suggests that there is either unaccounted for sources of meat-cooking molecular markers in the ambient samples, or there is some property of atmospheric aerosols that significantly inhibits reaction that was not captured in this study. Oxidation of motor vehicle profiles led to both higher estimates of total vehicle OC and a quadrupling of gasoline OC, while the diesel contribution changed very little. The increase in gasoline OC changes gasoline vehicle emissions from a relatively minor source to a major one. Thus, oxidation of molecular markers can have a significant impact on receptor model predictions. The second objective was to investigate SOA formation from the photo-oxidation of whole diesel exhaust. Diluted exhaust from a diesel engine was photo-oxidized in a smog chamber to investigate SOA production. Photochemical oxidation rapidly produced significant SOA, almost doubling the organic aerosol contribution of primary emissions after several hours of processing. Less than 10% of the SOA mass could be explained using a SOA model and the measured oxidation of known precursors, such as light aromatics. However, the ultimate yield of SOA is uncertain because it is sensitive to treatment of particle and vapor losses to the chamber walls. Aerosol Mass Spectrometer (AMS) mass spectra reveal that the organic aerosol becomes progressively more oxidized throughout the experiments. The data provide str

Weitkamp, Emily A.

338

Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation  

NASA Astrophysics Data System (ADS)

To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 ?g/m3 and 78.2±58.4 ?g/m3, with PM1.8/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine particles. PMF model was used to resolve the particle modes. Three modes were resolved at Yufa, representing condensation, droplet and coarse mode. However, one more droplet mode with bigger size was resolved, which was considered probably from regional transport. Condensation mode accounted for 10%-60% of the total mass at both sites, indicating it must be taken into account in summer. The formation of sulfate was mainly attributed to in-cloud or aerosol droplet process (PKU 80%, Yufa 70%) and gas condensation process (PKU 14%, Yufa 22%). According to the thermodynamic instability of NH4NO3, size distributions of nitrate were classified as three categories by RH. The existence of Ca(NO3)2 in droplet mode indicated the reaction of HNO3 with crustal particles was also important in fine particles. Linear regression gave a rough estimation that 69% of the PM10 and 87% of the PM1.8 at PKU were regional contributions. Sulfate, ammonium and oxalate were formed regionally, with the regional contributions of 90%, 87% and 95% to PM1.8. Nitrate formation was local dominant. In summary regional secondary formation led to aerosol pollution in the summer of Beijing.

Guo, S.; Hu, M.; Wang, Z. B.; Slanina, J.; Zhao, Y. L.

2009-11-01

339

Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation  

NASA Astrophysics Data System (ADS)

To characterize aerosol pollution in Beijing, size-resolved aerosols were collected by MOUDIs during CAREBEIJING-2006 field campaign at Peking University (urban site) and Yufa (upwind rural site). Fine particle concentrations (PM1.8 by MOUDI) were 99.8±77.4 ?g/m3 and 78.2±58.4 ?g/m3, with PM1.8/PM10 ratios of 0.64±0.08 and 0.76±0.08 at PKU and Yufa, respectively, and secondary compounds accounted for more than 50% in fine particles. PMF model analysis was used to resolve the particle modes. Three modes were resolved at Yufa, representing condensation, droplet and coarse mode. However, one more droplet mode with bigger size was resolved, which was considered probably from regional transport. Condensation mode accounted for 10%-60% of the total mass at both sites, indicating that the gas-to-particle condensation process was important in summer. The formation of sulfate was mainly attributed to in-cloud or aerosol droplet process (PKU 80%, Yufa 70%) and gas condensation process (PKU 14%, Yufa 22%). According to the thermodynamic instability of NH4NO3, size distributions of nitrate were classified as three categories by RH. The existence of Ca(NO3)2 in droplet mode indicated the reaction of HNO3 with crustal particles was also important in fine particles. A rough estimation was given that 69% of the PM10 and 87% of the PM1.8 in Beijing urban were regional contributions. Sulfate, ammonium and oxalate were formed regionally, with the regional contributions of 90%, 87% and 95% to PM1.8. Nitrate formation was local dominant. In summary regional secondary formation led to aerosol pollution in the summer of Beijing.

Guo, S.; Hu, M.; Wang, Z. B.; Slanina, J.; Zhao, Y. L.

2010-02-01

340

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

341

On the Evaporation Kinetics and Phase of Laboratory and Ambient Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Field measurements of secondary organic aerosol (SOA) find significantly higher mass loads than predicted by models, sparking intense effort that is focused on finding additional SOA sources, but leaves many of the fundamental assumptions that are used by models unchallenged. Current air-quality models use absorptive partitioning theory assuming SOA particles are liquid droplets that form instantaneous reversible equilibrium with gas phase. Further, they ignore the effects of adsorption of spectator organic species during SOA formation on SOA properties and fate. Using an accurate and highly sensitive experimental approach for studying evaporation kinetics of size-selected single SOA particles, we characterized room-temperature evaporation kinetics of laboratory generated ?-pinene SOA and ambient atmospheric SOA. The experimental setup was first tested by measuring the evaporation kinetics of single component organic particles of known vapor pressure. We show that, as expected for liquid droplets, smaller particles evaporate faster, and that these data yield the correct vapor pressure. We then study the evaporation kinetics of ?-pinene SOA and find that evaporation proceeds in two stages: a fast stage, during which 50% of the particle volume evaporates in ~100 minutes, followed by a slower stage, when additional 25% evaporate in 1400 minutes, which is in sharp contrast to the ~10 minutes timescale predicted by current kinetic models. ?-pinene SOA formed in the presence of “spectator” hydrophobic organic vapors like dioctyl phthalate, dioctyl sebacate, pyrene, or their mixture, were shown to adsorb noticeable amounts of these organics, forming what we term here ‘coated’ SOA particles. We show that these adsorbed coatings reduce evaporation rates of SOA particles. Moreover, aging of coated SOA particles dramatically reduces evaporation rates, and in some cases nearly stops it. For example, aging of SOA with adsorbed pyrene reduces evaporation rate to the point that only ~11% of the particle volume evaporates within 24 hrs. For all cases studied in this work, SOA evaporation behavior is size-independent and does not follow the evaporation kinetics of liquid droplets, which is in sharp contrast with model assumptions. To address the question of how closely the laboratory observations described above reflect reality in the atmosphere we characterized the evaporation kinetics of size-selected atmospheric SOA particles sampled in-situ during the recent Carbonaceous Aerosols and Radiative Effects Study (CARES) field campaign. We find that the evaporation of ambient SOA is very similar to that of coated and aged laboratory-generated ?-pinene SOA. Ambient SOA particles in Sacramento, CA lose between 17% and 25% of their volume in 6 hours. Like laboratory SOA, their evaporation is size-independent and does not follow the kinetics of liquid droplets.