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1

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

2

Hygroscopicity of Amine Secondary Aerosol - Mixtures of Organic and Inorganic Components  

NASA Astrophysics Data System (ADS)

Aliphatic amines are emitted from both biogenic and anthropogenic sources and contribute to the formation of secondary aerosol in reactions with atmospheric radicals. However, the cloud condensation nuclei (CCN) ability of amine aerosol has not been explored yet. Here, we study the hygroscopicity of aerosol formed from three aliphatic amines (trimethylamine, diethylamine and butylamine) in the UCR environmental chamber. Amines can react with NO3, a dominant night time oxidant in acid-base and/or oxidation reactions. The mass fraction of organic and inorganic components of formed aerosol was measured by Particle-into-Liquid Sampler coupled to dual ion chromatographs (PILS-ICs) and Scanning Mobility Particle Sizer (SMPS). CCN counter was used to measure the water-uptake ability of these particles. Significantly high hygroscopicity (?>0.3) was observed for aerosols formed from diethylamine and butylamine with NO3 radicals, which comprised >40% inorganic salt. Compared with amines oxidized by hydroxyl radicals, the presence of aminium salts formed in acid-base reactions greatly improved CCN activity of NO3-initiated aerosol. The effect of water vapor on the formation of aminium salts and aerosol hygroscopicity was also studied. Our results will significantly impact the estimation and role of amines in atmospheric chemistry and global climate models.

Tang, X.; Cocker, D. R.; Purvis-Roberts, K.; Asa-Awuku, A. A.

2012-12-01

3

Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London  

NASA Astrophysics Data System (ADS)

For the first time, the behaviour of non-refractory inorganic and organic submicron particulate through an entire annual cycle is investigated using measurements from an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) located at a UK urban background site in North Kensington, London. We show secondary aerosols account for a significant fraction of the submicron aerosol burden and that high concentration events are governed by different factors depending on season. Furthermore, we demonstrate that on an annual basis there is no variability in the extent of secondary organic aerosol (SOA) oxidation, as defined by the oxygen content, irrespective of amount. This result is surprising given the changes in precursor emissions and contributions as well as photochemical activity throughout the year; however it may make the characterisation of SOA in urban environments more straightforward than previously supposed. Organic species, nitrate, sulphate, ammonium, and chloride were measured during 2012 with average concentrations (±one standard deviation) of 4.32 (±4.42), 2.74 (±5.00), 1.39 (±1.34), 1.30 (±1.52) and 0.15 (±0.24) ?g m-3, contributing 43, 28, 14, 13 and 2% to the total submicron mass, respectively. Components of the organic aerosol fraction are determined using positive matrix factorisation (PMF) where five factors are identified and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2). OOA1 and OOA2 represent more and less oxygenated OA with average concentrations of 1.27 (±1.49) and 0.14 (±0.29) ?g m-3, respectively, where OOA1 dominates the SOA fraction (90%). Diurnal, monthly, and seasonal trends are observed in all organic and inorganic species, due to meteorological conditions, specific nature of the aerosols, and availability of precursors. Regional and transboundary pollution as well as other individual pollution events influence London's total submicron aerosol burden. High concentrations of non-refractory submicron aerosols in London are governed by particulate emissions in winter, especially nitrate and SFOA, whereas SOA formation drives the high concentrations during the summer. The findings from this work could have significant implications for modelling of urban air pollution as well as for the effects of atmospheric aerosols on health and climate.

Young, D. E.; Allan, J. D.; Williams, P. I.; Green, D. C.; Flynn, M. J.; Harrison, R. M.; Yin, J.; Gallagher, M. W.; Coe, H.

2014-07-01

4

Impact of emission changes on secondary inorganic aerosol episodes across Germany  

NASA Astrophysics Data System (ADS)

In this study, the response of secondary inorganic aerosol (SIA) concentrations to changes in precursor emissions during high PM10 episodes over central Europe in spring 2009 was investigated with the Eulerian Chemistry Transport Model (CTM) REM-Calgrid (RCG). The model performed well in capturing the temporal variation of PM10 and SIA concentrations and was used to analyse the different origin, development and characteristics of the selected high PM10 episodes. SIA concentrations, which contribute to about 50% of the PM10 concentration in northwestern Europe, have been studied by means of several model runs for different emission scenarios. SO2, NOx and NH3 emissions have been varied within a domain covering Germany and within a domain covering Europe. It was confirmed that the response of sulfate, nitrate and ammonium concentrations and deposition fluxes of S and N to SO2, NOx and NH3 emission changes is non-linear. The deviation from linearity was found to be lower for total deposition fluxes of S and N than for SIA concentrations. Furthermore, the study has shown that incorporating explicit cloud chemistry in the model adds non-linear responses to the system. It significantly modifies the response of modelled SIA concentrations and S and N deposition fluxes to changes in precursor emissions. The analysis of emission reduction scenario runs demonstrates that next to European-wide emission reductions additional national NH3 measures in Germany are more effective in reducing SIA concentrations and deposition fluxes than additional national measures on SO2 and NOx.

Banzhaf, S.; Schaap, M.; Wichink Kruit, R. J.; Denier van der Gon, H. A. C.; Stern, R.; Builtjes, P. J. H.

2013-12-01

5

Dynamic model evaluation for secondary inorganic aerosol and its precursors over Europe between 1990 and 2009  

NASA Astrophysics Data System (ADS)

In this study we present a dynamic model evaluation of the chemistry transport model LOTOS-EUROS to analyse the ability of the model to reproduce observed non-linear responses to emission changes and interannual variability of secondary inorganic aerosol (SIA) and its precursors over Europe from 1990 to 2009. The 20 year simulation was performed using a consistent set of meteorological data provided by the regional climate model RACMO2. Observations at European rural background sites have been used as reference for the model evaluation. To ensure the consistency of the used observational data stringent selection criteria were applied including a comprehensive visual screening to remove suspicious data from the analysis. The LOTOS-EUROS model was able to capture a large part of the day-to-day, seasonal and interannual variability of SIA and its precursors' concentrations. The dynamic evaluation has shown that the model is able to simulate the declining trends observed for all considered sulphur and nitrogen components following the implementation of emission abatement strategies for SIA precursors over Europe. Both, the observations and the model show the largest part of the decline in the 1990's while smaller concentration changes and an increasing number of non-significant trends are observed and modelled between 2000-2009. Furthermore, the results confirm former studies showing that the observed trends in sulphate and total nitrate concentrations from 1990 to 2009 are significantly lower than the trends in precursor emissions and precursor concentrations. The model captured these non-linear responses to the emission changes well. Using the LOTOS-EUROS source apportionment module trends in formation efficiency of SIA have been quantified for four European regions. The exercise has revealed a 20-50% more efficient sulphate formation in 2009 compared to 1990 and an up to 20% more efficient nitrate formation per unit nitrogen oxide emission, which added to the explanation of the non-linear responses. However, we have also identified some weaknesses to the model and the input data. LOTOS-EUROS underestimates the observed nitrogen dioxide concentrations throughout the whole time period, while it overestimates the observed nitrogen dioxide concentration trends. Moreover, model results suggest that the emission information of the early 1990's used in this study needs to be improved concerning magnitude and spatial distribution.

Banzhaf, S.; Schaap, M.; Kranenburg, R.; Manders, A. M. M.; Segers, A. J.; Visschedijk, A. H. J.; Denier van der Gon, H. A. C.; Kuenen, J. J. P.; van Meijgaard, E.; van Ulft, L. H.; Cofala, J.; Builtjes, P. J. H.

2014-07-01

6

The secondary formation of inorganic aerosols in the droplet mode through heterogeneous aqueous reactions under haze conditions  

NASA Astrophysics Data System (ADS)

Secondary inorganic aerosols play important roles in visibility reduction and in regional haze pollution. To investigate the characteristics of size distributions of secondary sulfates and nitrates as well as their formation mechanisms under hazes, size-resolved aerosols were collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Jinan, China, in all four seasons (December 2007-October 2008). In haze episodes, the secondary sulfates and nitrates primarily formed in fine particles, with elevated concentration peaks in the droplet mode (0.56-1.8 ?m). The fine sulfates and nitrates were completely neutralized by ammonia and existed in the forms of (NH4)2SO4 and NH4NO3, respectively. The secondary formation of sulfates, nitrates and ammonium (SNA) was found to be related to heterogeneous aqueous reactions and was largely dependent on the ambient humidity. With rising relative humidity, the droplet-mode SNA concentration, the ratio of droplet-mode SNA to the total SNA, the fraction of SNA in droplet-mode particles and the mass median aerodynamic diameter of SNA presented an exponential, logarithmic or linear increase. Two heavily polluted multi-day haze episodes in winter and summer were analyzed in detail. The secondary sulfates were linked to heterogeneous uptake of SO2 followed by the subsequent catalytic oxidation by oxygen together with iron and manganese in winter. The fine nitrate formation was strongly associated with the thermodynamic equilibrium among NH4NO3, gaseous HNO3 and NH3, and showed different temperature-dependences in winter and summer.

Wang, Xinfeng; Wang, Wenxing; Yang, Lingxiao; Gao, Xiaomei; Nie, Wei; Yu, Yangchun; Xu, Pengju; Zhou, Yang; Wang, Zhe

2012-12-01

7

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

8

Cloud condensation nuclei activity of aliphatic amine secondary aerosol  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The resulting particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate ...

9

CCN activity of aliphatic amine secondary aerosol  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

10

Assessing sensitivity regimes of secondary inorganic aerosol formation in Europe with the CALIOPE-EU modeling system  

NASA Astrophysics Data System (ADS)

Sulfur dioxide and nitrogen oxides form two of largest contributors to PM2.5 in Europe; ammonium sulfate ((NH4)2SO4) and ammonium nitrate (NH4NO3). In-situ observations of many chemical components are rather sparse, and thus neither can accurately characterize the distribution of pollutants nor predict the effectiveness of emission control. Understanding (and controlling) the formation regimes for these components is important for the achievement of the reduction objectives established in the European legislation for PM2.5 (20% of PM2.5 triennial for the mean of urban background levels between 2018 and 2020). For this purpose, the present work uses the CALIOPE high-resolution air quality modeling system (12 km × 12 km, 1 h) to investigate the formation of SIA (SO42-, NO3- and NH4+, which involve an important part of PM) and their gaseous precursors (SO2, HNO3 and NH3) over Europe during the year 2004. The CALIOPE system performs well at estimating SIAs when compared to the measurements from EMEP monitoring network, but errors are larger for gaseous precursors. NH3 is underestimated in the warmest months, HNO3 tends to be overestimated in the summer months, and SO2 appears to be systematically overestimated. The temporal treatment of ammonia emission is a probable source of uncertainty in the model representation of SIA. Furthermore, we discuss the annual pattern for each inorganic aerosol and gas precursor species over Europe estimated with the EMEP data and CALIOPE outputs, comparing the performance with other European studies. Spatial distribution of key indicators is used to characterize chemical regimes and understand the sensitivity of SIA components to their emission precursors. Results indicate that SO42- is not usually fully neutralized to ammonium sulfate in ambient measurements and is usually fully neutralized in model estimates. CALIOPE and EMEP observations agree that the continental regions in Europe tend to be HNO3-limited for nitrate formation. Regulatory strategies in such regions should focus on reductions in NOx (NO + NO2) rather than NH3 to control ammonium nitrate. This work assesses how well the CALIOPE system reproduces the spatial and temporal variability of SIAs and their gaseous precursors over Europe and complements the measurement findings.

Pay, María T.; Jiménez-Guerrero, Pedro; Baldasano, José M.

2012-05-01

11

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

SciTech Connect

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

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

1999-06-07

12

Response of secondary inorganic aerosol concentrations and deposition fluxes of S and N across Germany to emission changes during high PM10 episodes in spring 2009  

NASA Astrophysics Data System (ADS)

In this study, the response of secondary inorganic aerosol (SIA) concentrations to changes in precursor emissions during high PM10 episodes over Central Europe in spring 2009 was investigated with the Eulerian Chemistry Transport Model (CTM) REM-Calgrid (RCG). The model performed well in capturing the temporal variation of PM10 and SIA concentrations and was used to analyse the different origin, development and characteristics of the selected high PM10 episodes. SIA concentrations, which attribute to about 50% of the PM10 concentration in north-western Europe, have been studied by means of several emission scenarios varying SO2, NOx and NH3 emissions within a domain covering Germany and within a domain covering Europe. It was confirmed that the response of sulphate, nitrate and ammonium concentrations and deposition fluxes of S and N to SO2, NOx and NH3 emission changes is non-linear. The deviation from linearity was found to be lower for total deposition fluxes of S and N than for SIA concentrations. Furthermore, the study has shown that incorporating explicit cloud chemistry in the model adds non-linear responses to the system and significantly modifies the response of modelled SIA concentrations and S and N deposition fluxes to changes in precursor emissions. The analysis of emission reduction scenarios demonstrates that next to European wide emission reductions additional national NH3 measures in Germany are more effective in reducing SIA concentrations and deposition fluxes than additional national measures on SO2 and NOx.

Banzhaf, S.; Schaap, M.; Wichink Kruit, R. J.; Denier van der Gon, H. A. C.; Stern, R.; Builtjes, P. J. H.

2013-06-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

14

Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol  

NASA Astrophysics Data System (ADS)

Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, ?, ? 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; ? ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol ? values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' ? ranges within 0.2 < ? < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol, whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. The contributions of semivolatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems.

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

2014-06-01

15

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

Microsoft Academic Search

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

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

2010-01-01

16

Role of ammonia chemistry and coarse mode aerosols in global climatological inorganic aerosol distributions  

E-print Network

1 Role of ammonia chemistry and coarse mode aerosols in global in a three dimensional chemical transport model to understand the roles of ammonia chemistry and natural inorganic thermodynamic equilibrium, ammonia chemistry and dust and seasalt aerosols improve agreement

Zender, Charles

17

EVIDENCE FOR ORGANOSULFATES IN SECONDARY ORGANIC AEROSOL  

EPA Science Inventory

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

18

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

19

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

20

Organic and Inorganic Aerosol Below-Cloud Scavenging by  

E-print Network

Organic and Inorganic Aerosol Below-Cloud Scavenging by Suburban New Jersey Precipitation S T E V E removalprocessesassociatedwithprecipitation(or,ingeneral terms, scavenging). The changes in ambient particle distributions showed an average PM1.0 below-cloud scavenging coefficient of 7 Ã? 10-5 ( 3 Ã? 10-5 s-1, with variability associated

Russell, Lynn

21

Climate forcing of the secondary organic aerosols  

NASA Astrophysics Data System (ADS)

In recent years, several field measurement campaigns have highlighted the importance of the organic fraction of aerosol mass, and with such spatial diversity that one may assert that these aerosols are ubiquitous in the troposphere, with particular importance in continental areas. Investigation of the chemical composition of organic aerosol remains a work in progress, but it is now clear that a significant portion of the total organic mass is composed of secondary organic material, that is, aerosol that is not emitted to the atmosphere in particulate form, but formed in situ from gaseous volatile organic carbon (VOC) precursors. A number of such precursors, of both biogenic and anthropogenic origin, have been identified. Experimental, inventory building and modelling studies have followed, with the empirical effort elucidating the chemical pathways that lead to secondary organic aerosol (SOA) formation, and providing means to estimate the aerosol yields from a given precursor-oxidation reaction. Other empirical studies have focused on the biogenic precursors, and have found that such emissions depend upon plant species, temperature, and, in certain cases, photosynthetically active radiation. Global inventories of anthropogenic VOC emissions, and of biogenic VOC emitter species distribution and their emission potential have been constructed. Building upon the results of empirical and inventory-building efforts, global models have been developed that provide estimates of global SOA precursor VOC emissions, SOA formation and atmospheric burdens of these species. Yet few attempts have been made to estimate the climate forcing due to these aerosols. Here we describe both the direct (radiative) aerosol forcing and the indirect forcing due to changes in cloud properties as calculated with the global aerosol-climate model ECHAM5/HAM.

O'Donnell, D.; Feichter, J.

2009-04-01

22

Organosulfate Formation in Biogenic Secondary Organic Aerosol  

EPA Science Inventory

Organosulfates of isoprene, a-pinene, and ß-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...

23

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

24

Aerosol route to functional nanostructured inorganic and hybrid porous materials.  

PubMed

The major advances in the field of the designed construction of hierarchically structured porous inorganic or hybrid materials wherein multiscale texturation is obtained via the combination of aerosol or spray processing with sol-gel chemistry, self-assembly and multiple templating are the topic of this review. The available materials span a very large set of structures and chemical compositions (silicates, aluminates, transition metal oxides, nanocomposites including metallic or chalcogenides nanoparticles, hybrid organic-inorganic, biohybrids). The resulting materials are manifested as powders or smart coatings via aerosol-directed writing combine the intrinsic physical and chemical properties of the inorganic or hybrid matrices with defined multiscale porous networks having a tunable pore size and connectivity, high surface area and accessibility. Indeed the combination of soft chemical routes and spray processing provides "a wind of change" in the field of "advanced materials". These strategies give birth to a promising family of innovative materials with many actual and future potential applications in various domains such as catalysis, sensing, photonic and microelectronic devices, nano-ionics and energy, functional coatings, biomaterials, multifunctional therapeutic carriers, and microfluidics, among others. PMID:20963791

Boissiere, Cedric; Grosso, David; Chaumonnot, Alexandra; Nicole, Lionel; Sanchez, Clement

2011-02-01

25

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

26

CARES Helps Explain Secondary Organic Aerosols  

ScienceCinema

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

Zaveri, Rahul

2014-06-02

27

CARES Helps Explain Secondary Organic Aerosols  

SciTech Connect

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

Zaveri, Rahul

2014-03-28

28

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

E-print Network

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

Karydis, V. A.

29

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....

30

Gasoline contributes more than diesel to secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Gasoline-powered vehicles contribute more to secondary organic aerosol formation than diesel-fueled vehicles do, a new study shows. Organic compounds in gasoline fuel and diesel exhaust can lead to the formation of secondary organic aerosols, which negatively affect air quality, visibility, and health and have impacts on climate; however, few studies have investigated the relative contribution of gasoline and diesel to secondary aerosols. Traffic studies have found that the ratio of gasoline-to diesel-powered vehicles changes on weekends. For instance, in the Los Angeles, Calif., area, diesel emissions are about 54% lower on weekends than on weekdays, though gasoline emissions are about the same.

Balcerak, Ernie

2012-05-01

31

Evaluation of biogenic emission flux and its impact on oxidants and inorganic aerosols in East Asia  

NASA Astrophysics Data System (ADS)

As a major precursor during the summer season, biogenic species are of primary importance in the ozone and SOAs (secondary organic aerosols) formations. Isoprene and mono-terpene also influence the level of inorganic aerosols (i.e. sulfate and nitrate) by controlling OH radicals. However, biogenic emission fluxes are highly uncertain in East Asia. While isoprene emission fluxes from the GEIA (Global Emissions Inventory Activity) and POET (Precursors of Ozone and their Effects in the Troposphere) inventories estimate approximately 20 Tg yr-1 in East Asia, those from the MEGAN (Model of Emissions of Gases and Aerosols from Nature) and MOHYCAN (MOdel for Hydrocarbon emissions by the CANopy) estimate approximately 10 Tg yr-1 and 5 Tg yr-1, respectively. In order to evaluate and/or quantify the magnitude of biogenic emission fluxes over East Asia, the tropospheric HCHO columns obtained from the GOME (Global Ozone Monitoring Experiment) observations were compared with the HCHO columns from the CMAQ (Community Multi-scale Air Quality) simulations over East Asia. In this study, US EPA Models-3/CMAQ v4.5.1 model simulation using the ACE-ASIA (Asia Pacific Regional Aerosol Characterization Experiment) emission inventory for anthropogenic pollutants and GEIA, POET, MEGAN, and MOHYCAN emission inventories for biogenic species was carried out in conjunction with the Meteorological fields generated from the PSU/NCAR MM5 (Pennsylvania state University/National Center for Atmospheric Research Meso-scale Model 5) model for the summer episodes of the year 2002. In addition to an evaluation of the biogenic emission flux, we investigated the impact of the uncertainty in biogenic emission inventory on inorganic aerosol formations and variations of oxidants (OH, O3, and H2O2) in East Asia. In this study, when the GEIA and POET emission inventories are used, the CMAQ-derived HCHO columns are highly overestimated over East Asia, particularly South China compared with GOME-derived HCHO columns. The CMAQ-derived HCHO columns using the MOHYCAN emission inventory have similar values with the GOME-derived HCHO columns over East Asia. Also, differences in biogenic emission fluxes lead to changes in the levels of nitrates by changing the OH radical concentrations.

Han, K. M.; Song, C. H.; Park, R. S.; Woo, J.; Kim, H.

2010-12-01

32

A Review of Secondary Organic Aerosol (SOA) Formation from Isoprene  

EPA Science Inventory

Recent field and laboratory evidence indicates that the oxidation of isoprene forms secondary organic aerosol (SOA). Global biogenic emissions of isoprene (600 Tg yr-1) are sufficiently large the formation of SOA is even small yields results in substantial production ...

33

[Water-soluble inorganic salts in ambient aerosol particles in Tangshan].  

PubMed

To investigate the levels, seasonal variation and size distributions of water soluble inorganic components, samples were collected with an Andersen cascade sampler in Tangshan from Sep. 2010 to Aug. 2011, and were analyzed by IC. The results showed that the secondary inorganic components (SO4(2-), NO3(-) and NH4(+)) were the major contributors to PM9 and PM2.1, accounting for 68% and 77% of the total water soluble salts in PM9 and PM2.1, respectively. The total concentrations of these three ions in spring, summer, autumn, and winter were 35.0, 84.7, 67.3 and 61.6 microg x m(-3) in PM9, and 23.2, 64.8, 52.7 and 49.6 microg x m(-3) in PM2.1. About 70%, 75% and 94% of SO4(2-), NO3(-) and NH4(+) were found in the fine mode of aerosol, respectively. Ca2+ and Mg2+ were unimodal and mostly concentrated in the coarse mode. Those results indicated that the pollution caused by atmospheric particles is serious in Tangshan. It is urgent to control the anthropogenic emissions sources, such as vehicle emission, coal and biomass burning. Meanwhile, it is necessary to strengthen the greening and reinforce the management of the road construction. PMID:23798095

Miao, Hong-Yan; Wen, Tian-Xue; Wang, Li; Li, Xing-Ru; Wang, Yue-Si

2013-04-01

34

Secondary organic aerosol formation from road vehicle emissions  

NASA Astrophysics Data System (ADS)

Organic aerosol particles (OA) are a major fraction of the submicron particulate matter. OA consists of directly emitted primary (POA) and secondary OA (SOA). SOA is formed in-situ in the atmosphere via the reaction of volatile organic precursors. The partitioning of SOA species depends not only on the exposure to oxidants, but for instance also on temperature, relative humidity (RH), and the absorptive mass chemical composition (presence of inorganics) and concentration. Vehicle exhaust is a known source of POA and likely contributes to SOA formation in urban areas [1;2]. This has recently been estimated by (i) analyzing ambient data from urban areas combined with fuel consumption data [3], (ii) by examining the chemical composition of raw fuels [4], or (iii) smog chamber studies [5, 6]. Contradictory and thus somewhat controversial results in the relative quantity of SOA from diesel vs. gasoline vehicle exhaust were observed. In order to elucidate the impact of variable ambient conditions on the potential SOA formation of vehicle exhaust, and its relation to the emitted gas phase species, we studied SOA formed from the exhaust of passenger cars and trucks as a function of fuel and engine type (gasoline, diesel) at different temperatures (T 22 vs. -7oC) and RH (40 vs. 90%), as well as with different levels of inorganic salt concentrations. The exhaust was sampled at the tailpipe during regulatory driving cycles on chassis dynamometers, diluted (200 - 400x) and introduced into the PSI mobile smog chamber [6], where the emissions were subjected to simulated atmospheric ageing. Particle phase instruments (HR-ToF-AMS, aethalometers, CPC, SMPS) and gas phase instruments (PTR-TOF-MS, CO, CO2, CH4, THC, NH3 and other gases) were used online during the experiments. We found that gasoline emissions, because of cold starts, were generally larger than diesel, especially during cold temperatures driving cycles. Gasoline vehicles also showed the highest SOA formation. Furthermore, we observed that vehicle emissions and SOA are significantly affected by temperature and RH: doubling the RH in the chamber resulted in significantly increased SOA formation. Primary emissions and secondary aerosol formation from diesel and gasoline vehicles will be compared at different temperature and RH. Also the interaction and influence of inorganics on organics will be discussed. References: [1] Robinson, A.L., et al. (2007) Science 315, 1259. [2] Weitkamp, E.A., et al. (2007) Environ. Sci. Technol. 41, 6969. [3] Bahreini, R., et al. (2012) Geophys. Res. Lett. 39, L06805. [4] Gentner, D.R. et al. (2012) PNAS 109, 18318. [5] Gordon, T.D. et al. (2013) Atmos. Chem. Phys. Discuss 13, 23173. [6] Platt, S.M., et al. (2013) Atmos. Chem. Phys. Discuss. 12, 28343.

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

2014-05-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

36

A large source of low-volatility secondary organic aerosol  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

37

A large source of low-volatility secondary organic aerosol.  

PubMed

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

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

2014-02-27

38

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

NASA Astrophysics Data System (ADS)

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

He, J.; Zhang, Y.

2014-09-01

39

Secondary organic aerosol model intercomparison based on secondary organic aerosol to odd oxygen ratio in Tokyo  

NASA Astrophysics Data System (ADS)

of secondary organic aerosol (SOA) models is critical for accurate understanding of the behavior and sources of atmospheric aerosols. Over the last decade, a number of SOA production pathways were discovered, and several new SOA models have been developed. However, few comparative studies of the performances of the various SOA models have been conducted. In this study, simulation data obtained with five SOA models (two yield models, a volatility basis set (VBS) model, a mechanistic model, and a near-explicit model) were compared. The performances of the models were evaluated by comparison of the simulated data with observed ratios of the SOA concentration to odd oxygen concentration ([SOA]/[Ox], where [Ox] = [O3] + [NO2]) in the Tokyo metropolitan area. In Tokyo, SOA concentrations have been shown to correlate well with Ox concentrations; thus, Tokyo is an appropriate location for this intercomparison study. All five models showed similar results for the concentrations of gaseous species, including ozone, reactive nitrogen, hydroxy radicals, and volatile organic compounds. In contrast, the simulated SOA concentrations varied substantially among the five models. The VBS model reproduced the observed [SOA]/[Ox] ratio well, whereas the other four models substantially underestimated the ratio. The sensitivity of the ratio to various input parameters differed substantially among the models, as did the volatility distribution of SOA and the source contributions of SOA, suggesting that the choice of SOA model is critical for accurate assessment of the atmospheric behavior and sources of SOA.

Morino, Yu; Tanabe, Kiyoshi; Sato, Kei; Ohara, Toshimasa

2014-12-01

40

Persistent sensitivity of Asian aerosol to emissions of nitrogen oxides  

E-print Network

We use a chemical transport model and its adjoint to examine the sensitivity of secondary inorganic aerosol formation to emissions of precursor trace gases from Asia. Sensitivity simulations indicate that secondary inorganic ...

Kharol, S. K.

41

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

42

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

43

Effects of Organic-Inorganic Interactions on the Hygroscopicity of Aerosol Particles  

NASA Astrophysics Data System (ADS)

Aerosol hygroscopicity is an important property affecting size as well as phase transitions and viscosity of soluble or partially soluble particles following changes in ambient relative humidity (RH) and temperature. The effects of hygroscopic particle growth on the water contents and physical states of aerosol phases in turn may significantly affect multiphase chemistry, the direct effect of aerosols on climate, and the ability of specific particles to act as cloud condensation or ice nuclei. The hygroscopic growth of organic-inorganic mixtures in stable or metastable equilibrium with the RH of the surrounding air is governed by chemical thermodynamics and can be described, in principle, by adequate thermodynamic models. Organic-inorganic interactions involving dissolved ionic species in liquid (potentially highly viscous) phases tend to deviate substantially from ideal mixing and can lead to hygroscopicity behaviour deviating from simple linear additivity assumptions at given RH. The latter assumptions are employed in the Zdanovskii-Stokes-Robinson (ZSR) mixing rule, which is typically found to describe hygroscopic mass growth well in the RH range of completely liquid aerosol systems. We present a comparison and discussion of thermodynamic calculations based on the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model and hygroscopic growth factor data from new measurements with an electrodynamic balance (EDB) as well as data from the literature. We focus on the different hygroscopicity features below the full deliquescence RH of multicomponent organic-inorganic systems. Experiments and model calculations are performed for different multicomponent systems showing varying degrees of organic-inorganic miscibility, including liquid-liquid phase separation, hygroscopicity, and hysteresis effects between metastable and stable gas-aerosol equilibria. It is found that depending on the hygroscopicity of the organic aerosol fraction and its miscibility with inorganic solutes, the water uptake prior to deliquescence can be substantial due to partial dissolution of electrolytes. This behaviour is not captured with a traditional ZSR parameterization, therefore, semi-empirical hygroscopicity parameterizations have been suggested recently. We show that the AIOMFAC-based equilibrium model is able to describe the causes of the water uptake based on solid-liquid and liquid-liquid equilibria between the coexisting aerosol phases. The model furthermore correctly accounts for the shift in the deliquescence RH of ammonium sulfate and other salts in aerosol mixtures, a thermodynamic effect caused by organic-inorganic interactions.

Zuend, A.; Lienhard, D.; Krieger, U. K.

2013-12-01

44

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

PubMed

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

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

2014-10-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

46

Global modeling of secondary organic aerosol formation: from atmospheric chemistry to climate  

E-print Network

1 Global modeling of secondary organic aerosol formation: from atmospheric chemistry to climate .........................................................13 1.3 Secondary organic aerosol formation ........................................................................................................18 CHAPTER 2 Global modeling of SOA formation from dicarbonyls, epoxides, organic nitrates

Sillman, Sanford

47

SECONDARY ORGANIC AEROSOL FORMATION FROM THE IRRADIATION OF SIMULATED AUTOMOBILE EXHAUST  

EPA Science Inventory

A laboratory study was conducted to evaluate the potential for secondary organic aerosol formation from emissions from automotive exhaust. The goal was to determine to what extent photochemical oxidation products of these hydrocarbons contribute to secondary organic aerosol (SO...

48

Inorganic aerosol formation and growth in the Earth's lower and upper atmosphere  

Microsoft Academic Search

This chapter describes the photo-chemical production of aerosol particles in two very different regions of the atmosphere: iodine oxide particles in the marine boundary layer (MBL), and meteoric smoke particles that form in the upper mesosphere from the ablation of interplanetary dust. These two systems are surprisingly analogous the source of the condensable inorganic vapours is external to the atmosphere,

R. W. Saunders; J. M. C. Plane

2006-01-01

49

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...

50

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

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

52

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

53

Indoor and outdoor concentrations of inorganic acidic aerosols and gases  

SciTech Connect

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

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

1991-02-01

54

PREDICTION OF MULTICOMPONENT INORGANIC ATMOSPHERIC AEROSOL BEHAVIOR. (R824793)  

EPA Science Inventory

Many existing models calculate the composition of the atmospheric aerosol system by solving a set of algebraic equations based on reversible reactions derived from thermodynamic equilibrium. Some models rely on an a priori knowledge of the presence of components in certain relati...

55

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

SciTech Connect

We have developed the novel Aerosol Dynamics, gas- and particle- phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: 1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), 2) the slow and almost particle size independent evaporation of ?-pinene secondary organic aerosol (SOA) particles, and 3) the influence of chamber wall effects on the observed SOA formation in smog chambers.

Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, Ditte; Rusanen, A.; Boy, Michael; Swietlicki, E.; Svenningsson, Birgitta; Zelenyuk, Alla; Pagels, J.

2014-08-11

56

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

57

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

58

Equilibration timescale of atmospheric secondary organic aerosol partitioning  

NASA Astrophysics Data System (ADS)

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

Shiraiwa, Manabu; Seinfeld, John H.

2012-12-01

59

The Effect of Organic Compounds on the Hygroscopic Properties of Inorganic Aerosol  

NASA Astrophysics Data System (ADS)

The hygroscopicity of the aerosols plays a major role for the direct and indirect effect on the climate. It is known that aerosols are often a mixture of inorganic and organic matter. A significant fraction of the organic matter is water soluble (WSOC) and affects light scattering, water uptake and phase transitions of multicomponent aerosols. Additionally, organic matter can act as a surfactant around an inorganic particle, affecting the evaporation-condensation time scale. This research project benefits from the combined measurements performed by two different instrumentations: the electrodynamic trap at IACETH, Zürich, Switzerland, and a Tandem Differential Mobility Analizer (TDMA) at the Paul Scherrer Institute, Switzerland. The Electrodynamic Trap consists of a chamber in which a levitated particle can experience all the atmospherically relevant conditions of temperature, pressure, and humidity. All these parameters can be continuously varied so that the hygroscopic curve of the aerosol particle can be measured. Additional tools help to better characterize the aerosol particle: 90 degrees angular scattering of lasers (for radius measurements) and intensity fluctuation of the scattered light with time (for phase changes detection). In this poster the results obtained through the electrodynamic balance technique will be shown and compared with the TDMA. In particular, bicomponent ammonium sulphate with adipic acid bicomponent particles are studied, with different mixing ratios. Particular emphasis is put on assessing the water uptake and the phase changes of the particles.

Krieger, U. K.; Zardini, A. A.; Marcolli, C.

2006-12-01

60

A Study on the Aqueous Formation of Secondary Organic Aerosols  

NASA Astrophysics Data System (ADS)

The effect aerosols have on radiative forcing in the atmosphere is recognized as one of the largest uncertainties in the radiation budget. About 80% of organic aerosol mass in the atmosphere is estimated to be created though secondary processes. Recently, the aqueous formation of secondary organic aerosols (SOA) has become recognized as important when considering the source, transformation and radiative impacts of SOA. This work focuses on implementing a mechanism for aqueous SOA formation that can be used in atmospheric chemistry and models of all scales, from box to global. A box model containing a simplified chemical mechanism for the aqueous production of precursors of aqueous SOA (Myriokefalitakis et al. (2011) is coupled to gas-phase chemistry which uses the carbon bond mechanism (CBM) IV is presented. The model implements aqueous chemistry of soluble gases, both in-cloud and aerosol water, including organic compounds such as glyoxal and methylglyoxal, which have been shown as potentially significant sources for dissolved secondary organic aerosols. This mechanism implements aqueous phase mass transfer and molecular dissociation. The model's performance is evaluated against previous box model studies from the literature. A comparison is conducted between the detailed GAMMA model (McNeill et al., 2012), which is constrained with chamber experiments and the one developed here. The model output under different atmospheric conditions is explored and differences and sensitivities are assessed. The objective of this work is to create a robust framework for simulating aqueous phase formation of SOA and maximizing the computational efficiency of the model, while maintaining accuracy, in order to later use the exact mechanism in global climate simulations.

Sinclair, K.; Tsigaridis, K.

2013-12-01

61

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 ...

62

Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign  

NASA Astrophysics Data System (ADS)

A photoacoustic spectrometer, a nephelometer, an aethalometer, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in North East Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethalometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 07:00 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the photochemical production of secondary aerosol (inorganic and organic) is approximately 75% of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

2009-06-01

63

Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign  

NASA Astrophysics Data System (ADS)

A photoacoustic spectrometer, a nephelometer, an aetholemeter, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in north east Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethelometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 7 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the same-day photochemical production of secondary aerosol (inorganic and organic) is approximately 40 percent of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

2008-09-01

64

Atmospheric organic particulate matter: From smoke to secondary organic aerosol  

NASA Astrophysics Data System (ADS)

We present an overview of the development of our understanding of the sources, formation mechanisms, physical and chemical transformations of atmospheric organic aerosol (OA) during the last thirty years. Until recently, organic particulate material was simply classified as either primary or secondary with the primary component being treated in models as nonvolatile and inert. However, this oversimplified view fails to explain the highly oxygenated nature of ambient OA, the relatively small OA concentration gradients between urban areas and their surroundings, and the concentrations of OA during periods of high photochemical activity. A unifying framework for the description of all components based on their volatility distribution (the volatility basis set) can be used for the treatment of a wide range of processes affecting organic aerosol loadings and composition in the atmosphere. These processes include direct organic particle and vapor emissions, chemical production of organic PM from volatile precursors, chemical reactions (aging) in all phases, as well as deposition of both particles and vapors and chemical losses to volatile products. The combination of this new framework with the recent results of laboratory studies can resolve some of the discrepancies between OA observations and laboratory results. The mass balance of the organic material as a function of its volatility is investigated and used to frame the corresponding constraints on the system. Finally we revisit the traditional definitions of primary and secondary organic aerosol and propose a new set of terms and definitions based on the improvements of our understanding.

Donahue, Neil M.; Robinson, Allen L.; Pandis, Spyros N.

65

Marine Primary and Secondary Aerosol emissions related to seawater biogeochemistry  

NASA Astrophysics Data System (ADS)

Marine aerosol contributes significantly to the global aerosol load and consequently has an important impact on both the Earth's albedo and climate. Different factors influence the way they are produced from the sea water and transferred to the atmosphere. The sea state (whitecap coverage) and sea temperature influence the size and concentration of primarily produced particles but also biogeochemical characteristics of the sea water may influence both the physical and chemical fluxes. In order to study marine emissions, one approach is to use semicontrolled environments such as mesocosms. Within the SAM project (Sources of marine Aerosol in the Mediterranean), we characterize the primary Sea Salt Aerosol (SSA) and Secondary aerosol formation by nucleation during mesocosms experiments performed in May 2013 at the Oceanographic and Marine Station STARESO in western Corsica. We followed both water and air characteristics of three mesocosms containing an immerged part filled with 3,3 m3 of sea water and an emerged part filled with filtered natural air. Mesocosms were equipped with a pack of optical and physicochemical sensors and received different treatments: one of these mesocosms was left unchanged as control and the two others were enriched by addition of nitrates and phosphates respecting Redfield ratio (N:P = 16) in order to create different levels of phytoplanctonic activities. The set of sensors in each mesocosm was allowed to monitor the water temperature, conductivity, pH, incident light, fluorescence of chlorophyll a, and dissolved oxygen concentration. The mesocosms waters were daily sampled for chemical and biological (dissolved organic matter (i.e. DOC and CDOM), particulate matter and related polar compounds, transparent polysaccharides and nutrients concentration) and biological (chlorophyll a, virus, bacteria, phytoplankton and zooplankton concentrations) analyses. Secondary new particle formation was followed on-line in the emerged parts of the mesocosms, while a primary production by bubble bursting was simulated from a sample of sea water in a dedicated set-up every day. The size segregated aerosol number fluxes, cloud condensation nuclei (CCN) fluxes, and biological and organic contents were determined as a function of the sea water characteristics.

Sellegri, Karine; D'Anna, Barbara; Marchand, Nicolas; Charriere, Bruno; Sempere, Richard; Mas, Sebastien; Schwier, Allison; Rose, Clémence; Pey, Jorge; Langley Dewitt, Helen; Même, Aurélie; R'mili, Badr; George, Christian; Delmont, Anne

2014-05-01

66

Investigating hygroscopic behavior and phase separation of organic/inorganic mixed phase aerosol particles with FTIR spectroscopy  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles can be composed of inorganic salts, such as ammonium sulfate and sodium chloride, and therefore exhibit hygroscopic properties. Many inorganic salts have very well-defined deliquescence and efflorescence points at which they take up and lose water, respectively. For example, the deliquescence relative humidity of pure ammonium sulfate is about 80% and its efflorescence point is about 35%. This behavior of ammonium sulfate is important to atmospheric chemistry because some reactions, such as the hydrolysis of nitrogen pentoxide, occur on aqueous but not crystalline surfaces. Deliquescence and efflorescence of simple inorganic salt particles have been investigated by a variety of methods, such as IR spectroscopy, tandem mobility analysis and electrodynamic balance. Field measurements have shown that atmospheric aerosol are not typically a single inorganic salt, instead they often contain organic as well as inorganic species. Mixed inorganic/organic aerosol particles, while abundant in the atmosphere, have not been studied as extensively. Many recent studies have focused on microscopy techniques that require deposition of the aerosol on a glass slide, possibly changing its surface properties. This project investigates the deliquescence and efflorescence points, phase separation and ability to exchange gas-phase components of mixed organic and inorganic aerosol using a flow tube coupled with FTIR spectroscopy. Ammonium sulfate aerosol mixed with organic polyols with different O:C ratios, including glycerol, 1,2,6-hexanetriol, 1,4-butanediol and 1,5-pentanediol have been investigated. This project aims to study gas-phase exchange in these aerosol systems to determine if exchange is impacted when phase separation occurs.

Zawadowicz, M. A.; Cziczo, D. J.

2013-12-01

67

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

68

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

69

Influence of particle phase state on the hygroscopic behavior of mixed organic-inorganic aerosols  

NASA Astrophysics Data System (ADS)

Recent work has demonstrated that organic and mixed organic-inorganic particles can exhibit multiple phase states depending on their chemical composition and on ambient conditions such as relative humidity (RH). To explore the extent to which water uptake varies with particle phase behavior, hygroscopic growth factors (HGFs) of nine laboratory-generated, organic and organic-inorganic aerosol systems with physical states ranging from well-mixed liquids, to phase-separated particles, to viscous liquids or semi-solids were measured with the Differential Aerosol Sizing and Hygroscopicity Spectrometer Probe at RH values ranging from 40-90%. Water-uptake measurements were accompanied by HGF and RH-dependent thermodynamic equilibrium calculations using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model. In addition, AIOMFAC-predicted growth curves are compared to several simplified HGF modeling approaches: (1) representing particles as ideal, well-mixed liquids, (2) forcing a single phase, but accounting for non-ideal interactions through activity coefficient calculations, and (3) a Zdanovskii-Stokes-Robinson-like calculation in which complete separation between the inorganic and organic components is assumed at all RH values, with water-uptake treated separately in each of the individual phases. We observed variability in the characteristics of measured hygroscopic growth curves across aerosol systems with differing phase behaviors, with growth curves approaching smoother, more continuous water uptake with decreasing prevalence of liquid-liquid phase separation and increasing oxygen : carbon ratios of the organic aerosol components. We also observed indirect evidence for the dehydration-induced formation of highly viscous semi-solid phases and for kinetic limitations to the crystallization of ammonium sulfate at low RH for sucrose-containing particles. AIOMFAC-predicted growth curves are generally in good agreement with the HGF measurements. The performances of the simplified modeling approaches, however, differ for particles with differing phase states. This suggests that a single simplified modeling approach cannot be used to capture the water-uptake behavior for the diversity of particle phase behavior expected in the atmosphere. Errors in HGFs calculated with the simplified models are of sufficient magnitude to contribute substantially to error in estimates of particle optical and radiative properties, particularly for the assumption that water uptake is driven by absorptive equilibrium partitioning with ideal particle-phase mixing.

Hodas, N.; Zuend, A.; Mui, W.; Flagan, R. C.; Seinfeld, J. H.

2014-12-01

70

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

EPA Science Inventory

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

71

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

72

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

73

Inorganic aerosols responses to emission changes in Yangtze River Delta, China  

SciTech Connect

China announced the Chinese National Ambient Air Quality standards (CH-NAAQS) on Feb. 29th, 2012, and PM2.5 is for the very first time included in the standards as a criteria pollutant. In order to probe into PM2.5 pollution over Yangtze River Delta, which is one of the major urban clusters hosting more than 80 million people in China, the integrated MM5/CMAQ modeling system is applied for a full year simulation to examine the PM2.5 concentration and seasonality, and also the inorganic aerosols responses to precursor emission changes. Both simulation and observation demonstrated that, inorganic aerosols have substantial contributions to PM2.5 over YRD, ranging from 37.1% in November to 52.8% in May. Nocturnal production of nitrate (NO3-) through heterogeneous hydrolysis of N2O5 was found significantly contribute to high NO3-concentration throughout the year. We also found that in winter NO3- was even increased under nitrogen oxides (NOx) emission reduction due to higher production of N2O5 from the excessive ozone (O3) introduced by attenuated titration, which further lead to increase of ammonium (NH4+) and sulfate (SO42-), while other seasons showed decrease response of NO3-. Sensitivity responses of NO3- under anthropogenic VOC emission reduction was examined and demonstrated that in urban areas over YRD, NO3- formation was actually VOC sensitive due to the O3-involved nighttime chemistry of N2O5, while a reduction of NOx emission may have counter-intuitive effect by increasing concentrations of inorganic aerosols.

Dong, Xinyi; Li, Juan; Fu, Joshua S.; Gao, Yang; Huang, Kan; Zhuang, Guoshun

2014-05-15

74

Inorganic aerosols responses to emission changes in Yangtze River Delta, China.  

PubMed

The new Chinese National Ambient Air Quality standards (CH-NAAQS) published on Feb. 29th, 2012 listed PM2.5 as criteria pollutant for the very first time. In order to probe into PM2.5 pollution over Yangtze River Delta, the integrated MM5/CMAQ modeling system is applied for a full year simulation to examine the PM2.5 concentration and seasonality, and also the inorganic aerosols responses to precursor emission changes. Total PM2.5 concentration over YRD was found to have strong seasonal variation with higher values in winter months (up to 89.9 ?g/m(3) in January) and lower values in summer months (down to 28.8 ?g/m(3) in July). Inorganic aerosols were found to have substantial contribution to PM2.5 over YRD, ranging from 37.1% in November to 52.8% in May. Nocturnal production of nitrate (NO3(-)) through heterogeneous hydrolysis of N2O5 was found significantly contribute to high NO3(-) concentration throughout the year. In winter, NO3(-) was found to increase under nitrogen oxides (NOx) emission reduction due to higher production of N2O5 from the excessive ozone (O3) introduced by attenuated titration, which further lead to increase of ammonium (NH4(+)) and sulfate (SO4(2-)), while other seasons showed decrease response of NO3(-). Sensitivity responses of NO3(-) under anthropogenic VOC emission reduction was examined and demonstrated that in urban areas over YRD, NO3(-) formation was actually more sensitive to VOC than NOx due to the O3-involved nighttime chemistry of N2O5, while a reduction of NOx emission may have counter-intuitive effect by increasing concentrations of inorganic aerosols. PMID:24631615

Dong, Xinyi; Li, Juan; Fu, Joshua S; Gao, Yang; Huang, Kan; Zhuang, Guoshun

2014-05-15

75

Secondary Organic Aerosol Composition from C12 Alkanes.  

PubMed

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

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

2014-05-22

76

Modeling regional secondary organic aerosol using the Master Chemical Mechanism  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

77

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

EPA Science Inventory

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

78

Development of gas-phase chemistry, secondary organic aerosol, and aqueous-phase chemistry modules for PM modeling. Final report  

SciTech Connect

The Coordinating Research Council (CRC) is sponsoring a multi-phase study to develop improved air quality models for particulate matter (PM). Improved urban and regional scale PM air quality models are needed to develop reliable emission control strategies for areas that exceed the National Ambient Air Quality Standards (NAAQS) for PM-2.5 and PM-10, and for National Parks and other Class 1 areas with impaired visibility. This report describes the development and implementation of two process modules for PM models. These particular process modules are needed to simulate secondary aerosol species, which are often the dominate portion of PM-2.5 mass. The first module simulates the gas-phase atmospheric chemistry of the VOC/NO{sub x}/SO{sub 2}/ozone system and the formation of secondary organic aerosols. The module also simulates the formation of inorganic species, including sulfuric acid and nitric acid, that form important aerosol species: sulfate and nitrate; The second module simulates the aqueous-phase chemistry in fogs and clouds. This chemistry primarily enhances SO{sub 2} oxidation rates and leads to enhanced sulfate aerosol concentrations.

Strader, R.; Gurciullo, C.S.; Pandis, S.N.; Kumar, N.; Lurmann, F.W.

1998-10-30

79

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

E-print Network

Photochemical Aging of Secondary Organic Aerosol Particles Generated from the Oxidation of d-Limonene; In Final Form: January 13, 2007 Secondary organic aerosol (SOA) particles are generated by reacting d-limonene spectroscopy techniques. Photolysis of limonene SOA in the tropospheric actinic region ( > 295 nm) readily

Nizkorodov, Sergey

80

Secondary organic aerosol importance in the future atmosphere  

NASA Astrophysics Data System (ADS)

In order to investigate the secondary organic aerosol (SOA) response to changes in biogenic volatile organic compounds (VOC) emissions in the future atmosphere and how important will SOA be relative to the major anthropogenic aerosol component (sulfate), the global three-dimensional chemistry/transport model TM3 has been used. Emission estimates of biogenic VOC (BVOC) and anthropogenic gases and particles from the literature for the year 2100 have been adopted. According to our present-day model simulations, isoprene oxidation produces 4.6 Tg SOA yr -1, that is less than half of the 12.2 Tg SOA yr -1 formed by the oxidation of other BVOC. In the future, nitrate radicals and ozone become more important than nowadays, but remain minor oxidants for both isoprene and aromatics. SOA produced by isoprene is estimated to almost triple, whereas the production from other BVOC more than triples. The calculated future SOA burden change, from 0.8 Tg at present to 2.0 Tg in the future, is driven by changes in emissions, oxidant levels and pre-existing particles. The non-linearity in SOA formation and the involved chemical and physical feedbacks prohibit the quantitative attribution of the computed changes to the above-mentioned individual factors. In 2100, SOA burden is calculated to exceed that of sulfate, indicating that SOA might become more important than nowadays. These results critically depend on the biogenic emissions and thus are subject to the high uncertainty associated with these emissions estimated due to the insufficient knowledge on plant response to carbon dioxide changes. Nevertheless, they clearly indicate that the change in oxidants and primary aerosol caused by human activities can contribute as much as the change in BVOC emissions to the increase of the biogenic SOA production in the future atmosphere.

Tsigaridis, Kostas; Kanakidou, Maria

81

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

82

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

83

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

85

Seasonal and diurnal characteristics of water soluble inorganic compounds in the gas and aerosol phase in the Zurich area  

NASA Astrophysics Data System (ADS)

Gas and aerosol samples were taken using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography (IC) in the city of Zurich, Switzerland from August to September 2002 and in March 2003. Major water soluble inorganic ions; nitrate, sulfate, and nitrite were analyzed online with a time resolution of two hours for the gas and aerosol phase. The fraction of water soluble inorganic anions in PM10 varied from 15% in August to about 38% in March. Seasonal and diurnal variations of nitrate in the gas and aerosol phase were observed with more than 50% of the total nitrate in the gas phase during August and more than 80% of nitrate in the aerosol phase during March exceeding the concentration of sulfate by a factor of 2. Aerosol sulfate, on the other hand, did not show significant variability with season. However, in the gas phase, the SO2 concentration was 6.5 times higher in winter than in summer. Nitrous acid (HONO) also showed a diurnal variation in both the gas and aerosol phase with the lowest concentration (0.2-0.6 µg/m3) in the afternoon. The primary pollutants, NO, CO and SO2 mixing ratios were often at their highest between 04:00-10:00 local time due to the build up of fresh vehicle emission under a nocturnal inversion.

Fisseha, R.; Dommen, J.; Gutzwiller, L.; Weingartner, E.; Gysel, M.; Emmenegger, C.; Kalberer, M.; Baltensperger, U.

2006-06-01

86

Seasonal and diurnal characteristics of water soluble inorganic compounds in the gas and aerosol phase in the Zurich area  

NASA Astrophysics Data System (ADS)

Gas and aerosol samples were taken using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography (IC) in the city of Zurich, Switzerland from August to September 2002 and in March 2003. Major water soluble inorganic ions; nitrate, sulfate, and nitrite were analyzed online with a time resolution of two hours for the gas and aerosol phase. The fraction of water soluble inorganic anions in PM10 varied from 15% in August to about 38% in March. Seasonal and diurnal variations of nitrate in the gas and aerosol phase were observed with more than 50% of the total nitrate in the gas phase during August and more than 80% of nitrate in the aerosol phase during March exceeding the concentration of sulfate by a factor of 2. Aerosol sulfate, on the other hand, did not show significant variability with season. However, in the gas phase, the SO2 concentration was 6.5 times higher in winter than in summer. Nitrous acid (HONO) also showed a diurnal variation in both the gas and aerosol phase with the lowest concentration (0.2-0.6 µg/m3) in the afternoon. The primary pollutants, NO, CO and SO2 mixing ratios were often at their highest between 04:00-10:00 local time due to the build up of fresh vehicle emission under a nocturnal inversion.

Fisseha, R.; Dommen, J.; Gutzwiller, L.; Weingartner, E.; Gysel, M.; Emmenegger, C.; Kalberer, M.; Baltensperger, U.

2005-08-01

87

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

88

Oxygenated products of sesquiterpenes in secondary organic aerosol  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) has a huge impact on air quality and climate change. It influences the Earth radiative budget through absorbing, scattering and reflecting radiation as well as the formation of clouds because the particulates can act as cloud condensation nuclei (CCN). Furthermore, it plays an important role for human health. SOA is formed from gaseous precursors which get oxidized by ozone, OH- and NO3-radicals in the atmosphere. Due to their low vapor pressure these degradation products can nucleate to form new particles or they can condense on existing aerosol particles. Despite the major progress in research during the last few years the actual chemical composition as well as the contribution of various volatile organic compounds (VOCs) to the formation of secondary organic aerosol is still partially unknown. Recent studies indicate that sesquiterpenes play an important role in the formation of SOA because of the low volatility of their oxygenated products (Lee et al., 2006). Their emission is estimated to be about 14,8 Tg per year (Henze et al., 2008), however, these emission rates remain highly uncertain due to the lack of quantitative emission rate measurements. In addition, the knowledge about the actual atmospheric degradation mechanism and the main oxidation products of sesquiterpenes is quite limited. ?-Caryophyllene, ?-humulene, ?-farnesene and ?-farnesene are the most abundant sequiterpenes in many sesquiterpene emission profiles. But also aromadendren, ?-bergamotene and ?-cadinene and germacrene-D can contribute significantly to some emission profiles (Duhl et al., 2008). To determine the major oxygenated products of sesquiterpenes in SOA, reaction chamber experiments with different sesquiterpenes and ozone were performed in a 100 L reaction chamber. To measure the time dependent formation of initial oxidation products, an APCI-IT-MS was directly connected to the reaction chamber. After 2 hours the APCI-IT-MS was replaced by a filter holder and the generated aerosol was collected for 20 hours. In case of ?-caryophyllene five different acidic oxidation products were synthesized and these acids were used for quantification. Atmospheric air samples taken during the HUMPPA campaign summer 2010 in Finland were analyzed for sesquiterpene oxygenated products. The major sesquiterpene oxidation products in the ambient air samples were quantified and the correlation with temperature was analyzed. Duhl, T. R., Helmig, D. and Guenther, A. (2008) Biogeosciences 5, 761-777. Henze, D.K., Seinfeld, J.H., Ng, N.L., Kroll, J.H., Fu, T.M., Jacob, D.J. and Heald, C.L. (2008) Atmospheric Chemistry and Physics 8, 2405-2421. Lee, A., Goldstein, A.H., Kroll, J.H., Ng, N.L., Varutbangkul, V., Flagan, R.C. and Seinfeld, J.H. (2006) Journal of Geophysical Research 111, D17305.

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

2012-04-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

91

Influence of collecting substrates on the characterization of hygroscopic properties of inorganic aerosol particles.  

PubMed

The influence of six collecting substrates with different physical properties on the hygroscopicity measurement of inorganic aerosol particle surrogates and the potential applications of these substrates were examined experimentally. Laboratory-generated single salt particles, such as NaCl, KCl, and (NH4)2SO4, 1-5 ?m in size, were deposited on transmission electron microscopy grids (TEM grids), parafilm-M, Al foil, Ag foil, silicon wafer, and cover glass. The particle hygroscopic properties were examined by optical microscopy. Contact angle measurements showed that parafilm-M is hydrophobic, and cover glass, silicon wafer, Al foil, and Ag foil substrates are hydrophilic. The observed deliquescence relative humidity (DRH) values for NaCl, KCl, and (NH4)2SO4 on the TEM grids and parafilm-M substrates agreed well with the literature values, whereas the DRHs obtained on the hydrophilic substrates were consistently ?1-2% lower, compared to those on the hydrophobic substrates. The water layer adsorbed on the salt crystals prior to deliquescence increases the Gibb's free energy of the salt crystal-substrate system compared to the free energy of the salt droplet-substrate system, which in turn reduces the DRHs. The hydrophilic nature of the substrate does not affect the measured efflorescence RH (ERH) values. However, the Cl(-) or SO4(2-) ions in aqueous salt droplets seem to have reacted with Ag foil to form AgCl or Ag2SO4, respectively, which in turn acts as seeds for the heterogeneous nucleation of the original salts, leading to higher ERHs. The TEM grids were found to be most suitable for the hygroscopic measurements of individual inorganic aerosol particles by optical microscopy and when multiple analytical techniques, such as scanning electron microscopy-energy dispersive X-ray spectroscopy, TEM-EDX, and/or Raman microspectrometry, are applied to the same individual particles. PMID:24506470

Eom, Hyo-Jin; Gupta, Dhrubajyoti; Li, Xue; Jung, Hae-Jin; Kim, Hyekyeong; Ro, Chul-Un

2014-03-01

92

[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

93

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

94

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 (particulate matter with diameter less than 1 ?m) 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 (particulate matter with diameter between 1 and 10 ?m) chloride is also high and its concentration exceeds 2 ?g m-3 in Texcoco Lake. PM1 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 the T0 measurement site, located in the Mexico City urban center, the average measured values of PM1 sulfate, nitrate, ammonium, and chloride are 3.5 ?g m-3, 3.5 ?g m-3, 2.1 ?g m-3, and 0.36 ?g m-3, respectively. The corresponding predicted values are 3.7 ?g m-3, 2.7 ?g m-3, 1.7 ?g m-3, and 0.25 ?g m-3. High sulfate concentrations are associated with the transport of sulfate from the Tula vicinity, while in periods where southerly winds are dominant; the concentrations of sulfate are low. The underprediction of nitrate can be attributed to the underestimation of OH levels by the model during the early morning. Ammonium is sensitive to the predicted sulfate concentrations and the nitrate levels. The performance of the model is also evaluated against measurements taken from a suburban background site (T1) located north of Mexico City. The average predicted PM2.5 (particulate matter with diameter less than 2.5 ?m) sulfate, nitrate, ammonium, chloride, sodium, calcium, and magnesium are 3.3, 3.2, 1.4, 0.5, 0.3, 1.2, and 0.15 ?g m-3, respectively. The corresponding measured concentrations are 3.7, 2.9, 1.5, 0.3, 0.4, 0.6, and 0.15 ?g m-3. The overprediction of calcium indicates a possible overestimation of its emissions and affects the partitioning of nitric acid to the aerosol phase resulting occasionally in an overprediction of nitrate. Additional improvements are possible by improving the performance of the model regarding the oxidant levels, and revising the emissions and the chemical composition of the fugitive dust. The hybrid approach in which the mass transfer to the fine aerosol is simulated using the bulk equilibrium assumption and to the remaining aerosol sections using a dynamic approach, is needed in order to accurately simulate the size distribution of the inorganic aerosols. The bulk equilibrium approach fails to reproduce the observed coarse nitrate and overpredicts the fine nitrate. 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 o

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

2011-12-01

95

Role of isoprene in secondary organic aerosol formation on a regional Yang Zhang,1  

E-print Network

in these regions. SOA formation is highly sensitive to the value of the enthalpy of vaporization of the SOARole of isoprene in secondary organic aerosol formation on a regional scale Yang Zhang,1 Jian and chemistry of aerosol formation and removal. Citation: Zhang, Y., J.-P. Huang, D. K. Henze, and J. H

Zhang, Yang

96

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

EPA Science Inventory

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

97

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

EPA Science Inventory

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

98

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...

99

Formation of Secondary Organic Aerosol from the Direct Photolytic Generation of Organic Radicals  

E-print Network

The immense complexity inherent in the formation of secondary organic aerosol (SOA)—due primarily to the large number of oxidation steps and reaction pathways involved—has limited the detailed understanding of its underlying ...

Kessler, Sean Herbert

100

Heterogeneous ice nucleation on simulated secondary organic aerosol.  

PubMed

In this study, we have explored the phase behavior and the ice nucleation properties of secondary organic aerosol made from aqueous processing (aqSOA). AqSOA was made from the dark reactions of methylglyoxal with methylamine in simulated evaporated cloud droplets. The resulting particles were probed from 215 to 250 K using Raman spectroscopy coupled to an environmental cell. We find these particles are in a semisolid or glassy state based upon their behavior when exposed to mechanical pressure as well as their flow behavior. Further, we find that these aqSOA particles are poor depositional ice nuclei, in contrast to previous studies on simple mixtures of glassy organics. Additionally, we have studied the effect of ammonium sulfate on the phase, morphology, and ice nucleation behavior of the aqSOA. We find that the plasticizing effect of ammonium sulfate lowers the viscosity of the aqSOA, allowing the ammonium sulfate to effloresce within the aqSOA matrix. Upon humidification, the aqSOA matrix liquefies before it can depositionally nucleate ice, and the effloresced ammonium sulfate can act as an immersion mode ice nucleus. This change in the mode of nucleation is accompanied by an increase in the overall ice nucleation efficiency of the aqSOA particles. PMID:24410444

Schill, Gregory P; De Haan, David O; Tolbert, Margaret A

2014-02-01

101

Nonequilibrium Atmospheric Secondary Organic Aerosol Formation and Growth  

SciTech Connect

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

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

2012-02-21

102

Experimental Determination of Chemical Diffusion within Secondary Organic Aerosol Particles  

SciTech Connect

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

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

2013-02-28

103

Light Absorption by Secondary Organic Aerosol from ?-Pinene: Effects of Oxidants, Seed Aerosol Acidity, and Relative Humidity  

SciTech Connect

It is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOA) generated from ozonolysis or NO3 oxidation of ?-pinene in the presence of neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532 and 870 nm. Light absorption at 355 and 405 nm was observed by SOA generated from oxidation of ?-pinene in the presence of acidic sulfate seed aerosols, under dry conditions. No absorption was observed when the relative humidity was elevated to greater than 27%, or in the presence of neutral sulfate seed aerosols. The light-absorbing compounds are speculated to be aldol condensation oligomers with organosulfate and organic nitrate groups. The results of this study also indicate that organic nitrates from ?-pinene SOA formed in the presence of neutral sulfate seed aerosols do not appear to absorb near-UV and UV radiation.

Song, Chen; Gyawali, Madhu S.; Zaveri, Rahul A.; Shilling, John E.; Arnott, W. Patrick

2013-10-25

104

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

105

Reactivity of Liquid and Semisolid Secondary Organic Carbon with Chloride and Nitrate in Atmospheric Aerosols.  

PubMed

Constituents of secondary organic carbon (SOC) in atmospheric aerosols are often mixed with inorganic components and compose a significant mass fraction of fine particulate matter in the atmosphere. Interactions between SOC and other condensed-phase species are not well understood. Here, we investigate the reactions of liquid-like and semisolid SOC from ozonolysis of limonene (LSOC) and ?-pinene (PSOC) with NaCl using a set of complementary microspectroscopic analyses. These reactions result in chloride depletion in the condensed phase, release of gaseous HCl, and formation of organic salts. The reactions attributed to acid displacement by SOC acidic components are driven by the high volatility of HCl. Similar reactions can take place in SOC/NaNO3 particles. The results show that an increase in SOC mass fraction in the internally mixed SOC/NaCl particles leads to higher chloride depletion. Glass transition temperatures and viscosity of PSOC were estimated for atmospherically relevant conditions. Data show that the reaction extent depends on SOC composition, particle phase state and viscosity, mixing state, temperature, relative humidity (RH), and reaction time. LSOC shows slightly higher potential to deplete chloride than PSOC. Higher particle viscosity at low temperatures and RH can hinder these acid displacement reactions. Formation of organic salts from these overlooked reactions can alter particle physiochemical properties and may affect their reactivity and ability to act as cloud condensation and ice nuclei. The release and potential recycling of HCl and HNO3 from reacted aerosol particles may have important implications for atmospheric chemistry. PMID:25386912

Wang, Bingbing; O'Brien, Rachel E; Kelly, Stephen T; Shilling, John E; Moffet, Ryan C; Gilles, Mary K; Laskin, Alexander

2014-11-25

106

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

107

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

109

Physical state and acidity of inorganic sulfate can regulate the production of secondary organic material from isoprene photooxidation products.  

PubMed

The production of secondary organic material (SOM) by the reactive uptake of isoprene photooxidation products was investigated using partially to wholly neutralized sulfuric acid particles. The experiments were performed at a relative humidity (RH) of <5% and a temperature of 20 °C. The extent X of neutralization was adjusted from that of sulfuric acid (X = 0) to that of ammonium sulfate (X = 1). Significant SOM production was observed only for X < 0.7. The threshold of 0.7 corresponded to the transition point of the sulfate particles from aqueous to solid for <5% RH. The phase transition of inorganic sulfate therefore regulated the particle-phase reactions that produce isoprene SOM, at least for the investigated conditions. For aqueous particles, a decreasing extent of neutralization was associated with increasing production of SOM, including increased production of oligomers and organosulfates. These results can underpin treatments of phase-dependent SOM production within chemical transport models, thereby improving the accuracy of simulations of biogenic-anthropogenic interactions in the atmosphere and the associated impacts of aerosol particles on climate and air quality. PMID:25623937

Kuwata, Mikinori; Liu, Yingjun; McKinney, Karena; Martin, Scot T

2015-02-10

110

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

EPA Science Inventory

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

111

Atmospheric oxidation of isoprene and 1,3-butadiene: influence of aerosol acidity and relative humidity on secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The effects of acidic seed aerosols on the formation of secondary organic aerosol (SOA) have been examined in a number of previous studies, several of which have observed strong linear correlations between the aerosol acidity (measured as nmol H+ per m3 air sample volume) and the percent change of secondary organic carbon (SOC). The measurements have used several precursor compounds representative of different classes of biogenic hydrocarbons including isoprene, monoterpenes, and sesquiterpenes. To date, isoprene has displayed the most pronounced increase in SOC, although few measurements have been conducted with anthropogenic hydrocarbons. In the present study, we examine several aspects of the effect of aerosol acidity on the secondary organic carbon formation from the photooxidation of 1,3-butadiene, as well as extending the previous analysis of isoprene. The photooxidation products measured in the absence and presence of acidic sulfate aerosols were generated either through photochemical oxidation of SO2 or by nebulizing mixtures of ammonium sulfate and sulfuric acid into a 14.5 m3 smog chamber system. The results showed that, like isoprene and ?-caryophyllene, 1,3-butadiene SOC yields linearly correlate with increasing acidic sulfate aerosol. The observed acid sensitivity of 0.11% SOC increase per nmol m-3 increase in H+ was approximately a factor of three less than that measured for isoprene. The results also showed that the aerosol yield decreased with increasing humidity for both isoprene and 1,3-butadiene, although to different degrees. Increasing the absolute humidity from 2 to 12 g m-3 reduced the 1,3-butadiene yield by 45% and the isoprene yield by 85%.

Lewandowski, M.; Jaoui, M.; Offenberg, J. H.; Krug, J. D.; Kleindienst, T. E.

2014-11-01

112

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

PubMed

A laboratory study was conducted to evaluate the potential for secondary organic aerosol formation from emissions from automotive exhaust. The goal was to determine to what extent photochemical oxidation products of these hydrocarbons contribute to secondary organic aerosol (SOA) and how well their formation is described by recently developed models for SOA formation. The quality of a surrogate was tested by comparing its reactivity with that from irradiations of authentic automobile exhaust. Experiments for secondary particle formation using the surrogate were conducted in a fixed volume reactor operated in a dynamic mode. The mass concentration of the aerosol was determined from measurements of organic carbon collected on quartz filters and was corrected for the presence of hydrogen, nitrogen, and oxygen atoms in the organic species. A functional group analysis of the aerosol made by Fourier transform infrared (FTIR) spectroscopy indicated PMID:11924857

Kleindienst, T E; Corse, E W; Li, W; McIver, C D; Conver, T S; Edney, E O; Driscoll, D J; Speer, R E; Weathers, W S; Tejada, S B

2002-03-01

113

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

NASA Astrophysics Data System (ADS)

Aircraft-based measurements of the water-soluble fraction of fine PM organic carbon (WSOC) and inorganic salt composition in the Atlanta, GA region were conducted in the summer of 2004. Five notable plumes of SO2, apparently from coal-fired power plants, were intercepted, and had NH4 +/SO4 2- molar ratios ranging from approximately 0.8 to 1.4 compared to molar ratios near 2 outside of the plumes. Sulfate aerosol concentrations increased from a regional background of 5-8 ?g m-3 to as high as 19.5 ?g m-3 within these plumes. No increase in WSOC concentrations was observed in plumes compared to out-of-plumes within a WSOC measurement uncertainty of 8%. These measurements suggest that secondary organic aerosol formation via heterogeneous acid-catalyzed reactions within power plant plumes are not likely a significant contributor to the ambient aerosol mass loading in Atlanta and the surrounding region. Because this region is rich in both biogenic and anthropogenic volatile organic carbon (VOC), the results may be widely applicable.

Peltier, R. E.; Sullivan, A. P.; Weber, R. J.; Wollny, A. G.; Holloway, J. S.; Brock, C. A.; de Gouw, J. A.; Atlas, E. L.

2007-03-01

114

Photolytic processing of secondary organic aerosols dissolved in cloud droplets  

SciTech Connect

The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05 - 1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300 - 400 nm radiation for up to 24 hours. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly reduced by photolysis relative to the monomeric compounds. Direct pH measurements showed that compounds containing carboxylic acids increased upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonylswas confirmed by the UV-Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n??* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ~ 0.03. The concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content.

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

2011-05-26

115

Experimental determination of chemical diffusion within secondary organic aerosol particles.  

PubMed

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

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

2013-02-28

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

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

118

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

119

A thermal desorption mass spectrometer for freshly nucleated secondary aerosol particles  

NASA Astrophysics Data System (ADS)

Secondary aerosol formation in the atmosphere is observed in a large variety of locations worldwide, introducing new particles to the atmosphere which can grow to sizes relevant for health and climate effects of aerosols. The chemical reactions leading to atmospheric secondary aerosol formation are not yet fully understood. At the same time, analyzing the chemical composition of freshly nucleated particles is still a challenging task. We are currently finishing the development of a field portable aerosol mass spectrometer for nucleation particles with diameters smaller than 30 nm. This instrument consists of a custom-built aerosol sizing and collection unit coupled to a time-of-flight mass spectrometer (TOF-MS). The aerosol sizing and collection unit is composed of three major parts: (1) a unipolar corona aerosol charger, (2) a radial differential mobility analyzer (rDMA) for aerosol size separation, and (3) an electrostatic precipitator for aerosol collection. After collection, the aerosol sample is thermally desorbed, and the resulting gas sample is transferred to the TOF-MS for chemical analysis. The unipolar charger is based on corona discharge from carbon fibres (e.g. Han et al., 2008). This design allows efficient charging at voltages below 2 kV, thus eliminating the potential for ozone production which would interfere with the collected aerosol. With the current configuration the extrinsic charging efficiency for 20 nm particles is 32 %. The compact radial DMA similar to the design of Zhang et al. (1995) is optimized for a diameter range from 1 nm to 100 nm. Preliminary tests show that monodisperse aerosol samples (geometric standard deviation of 1.09) at 10 nm, 20 nm, and 30 nm can easily be separated from the ambient polydisperse aerosol population. Finally, the size-segregated aerosol sample is collected on a high-voltage biased metal filament. The collected sample is protected from contamination using a He sheath counterflow. Resistive heating of the filament allows temperature-controlled desorption of compounds of different volatility. We will present preliminary characterization experiments of the aerosol sizing and collection unit coupled to the mass spectrometer. Funding by the German Research Foundation (DFG) under grant DFG HE5214/3-1 is gratefully acknowledged. Han, B., Kim, H.J., Kim, Y.J., and Sioutas, C. (2008) Unipolar charging of ultrafine particles using carbon fiber ionizers. Aerosol Sci. Technol, 42, 793-800. Zhang, S.-H., Akutsu, Y., Russell, L.M., Flagan, R.C., and Seinfeld, J.H. (1995) Radial Differential Mobility Analyzer. Aerosol Sci. Technol, 23, 357-372.

Held, A.; Gonser, S. G.

2012-04-01

120

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

121

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

122

Determination of the age distribution of primary and secondary aerosol species using a chemical transport model  

NASA Astrophysics Data System (ADS)

A computationally efficient scheme to allow tracking of aerosol species age as a function of space and time within a three-dimensional chemical transport model (CTM) has been developed. The aerosol age distribution is calculated by utilizing the Particulate Matter Source Apportionment Technology (PSAT) algorithm which allows the calculation of different source contributions to both primary and secondary particulate matter concentrations in the modeling domain. As an example, the aerosol age in the eastern United States, including both primary and secondary species, is examined using the regional CTM PMCAMx. The average calculated ages are on the order of a few days for particulate matter near the ground but are highly variable in space and time. Primary aerosol species had average ages of approximately 24 h over this polluted continental region while the average ages for secondary species were 48-72 h near the surface. As expected, the average age of all aerosol components increases vertically in the atmosphere. Age increases rapidly away from the sources of aerosol and its precursors, and for nonvolatile species it increases with particle size.

Wagstrom, Kristina M.; Pandis, Spyros N.

2009-07-01

123

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

124

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

125

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

E-print Network

No evidence for acid-catalyzed secondary organic aerosol formation in power plant plumes over that secondary organic aerosol formation via heterogeneous acid-catalyzed reactions within power plant plumes conducted in the summer of 2004. Five notable plumes of SO2, apparently from coal-fired power plants, were

Weber, Rodney

126

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

127

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

E-print Network

ranging from 20 to 90% [Kanakidou et al., 2005]. These aerosols can be directly emitted (primary) or formed in the atmosphere (secondary) following the oxidation of volatile organic compounds (VOC). Precursors of secondary organic aerosols (SOA) include... products of VOCs have been extensively studied in laboratory chambers. Organic aerosol growth has been observed following the oxidation of biogenic terpenoid compounds (monoterpenes and sesquiterpenes) [Griffin et al., 1999; Lee et al., 2006a, 2006b...

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

2008-03-01

128

Physico-chemical properties of aerosols in Sao Paulo, Brazil and mechanisms of secondary organic aerosol formation.  

NASA Astrophysics Data System (ADS)

Megacities emissions are increasingly becoming a global issue, where emissions from the transportation sector play an increasingly important role. Sao Paulo is a megacity with a population of about 18 million people, 7 million cars and large-scale industrial emissions. As a result of the vehicular and industrial emissions, the air quality in Sao Paulo is bellow WMO standards for aerosol particles and ozone. Many uncertainties are found on gas- and particulate matter vehicular emission factors and their following atmospheric processes, e.g. secondary organic aerosol formation. Due to the uniqueness of the vehicular fuel in Brazil, largely based on ethanol use, such characterization currently holds further uncertainties. To improve the understanding of the role of this unique emission characteristics, we are running a source apportionment study in Sao Paulo focused on the mechanisms of organic aerosol formation. One of the goals of this study is a quantitative aerosol source apportionment focused on vehicular emissions, including ethanol and gasohol (both fuels used by light-duty vehicles). This study comprises four sampling sites with continuous measurements for one year, where trace elements and organic aerosol are being measured for PM2.5 and PM10 along with real-time NOx, O3, PM10 and CO measurements. Aerosol optical properties and size distribution are being measured on a rotation basis between sampling stations. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to measure in real time VOCs and aerosol composition, respectively. Trace elements were measured using XRF and OC/EC analysis was determined with a Sunset OC/EC instrument. A TSI Nephelometer with 3 wavelengths measure light scattering and a MAAP measure black carbon. Results show aerosol number concentrations ranging between 10,000 and 35,000 cm-3, mostly concentrated in the nucleation and Aitken modes, with a peak in size at 80-120 nm. Average mass concentrations were measured at 11.5 ug/m3 and 30.7 ug/m3 for fine and coarse mode, respectively. The elemental analysis shows that Fe, Si and Al dominate the coarse mode indicating strong contribution from soil dust resuspension whereas sulfur dominates the fine mode (0.8 micrograms/m3). Scattering coefficients typically range between 20 and 150 Mm-1 at 637 nm, and absorption varied between 10 to 60 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.80, indicating a significant contribution of primary soot particles to the aerosol population. Organic aerosol accounts for 70% of the aerosol mass, with nitrates accounting for 11.7%, ammonia 8.4%, sulfate 8.2% and chlorine 1.6% pf PM1 measured by AMS techniques. Most of the organic aerosol were oxygenated. Several new particle formation events were observed, with a clear increase in organic aerosol and VOCs amounts associated with new particle formation. The study allows the characterization of a unique fueled fleet emissions and its impact on atmospheric chemistry, particle formation and other atmospheric dynamic processes. This work was funded by Petrobras S/A

Artaxo, Paulo; Ferreira de Brito, Joel; Varanda Rizzo, Luciana; Luiza Godoy, Maria; Godoy, Jose Marcus

2013-04-01

129

Cloud forming potential of oligomers relevant to secondary organic aerosols  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

130

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

PubMed Central

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

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

2012-01-01

131

Cloud condensation nucleus activity of secondary organic aerosol particles mixed with sulfate  

E-print Network

Cloud condensation nucleus activity of secondary organic aerosol particles mixed with sulfate condensation nucleus (CCN) activity of organic-sulfate particles was investigated using a steady- state. Rosenoern, J. E. Shilling, Q. Chen, and S. T. Martin (2007), Cloud condensation nucleus activity

132

Yields of Secondary Organic Aerosol from Reactions between Ozone and Surface-Adsorbed d-Limonene  

E-print Network

Yields of Secondary Organic Aerosol from Reactions between Ozone and Surface-Adsorbed d-Limonene reactions with surface-adsorbed d-limonene on gas-phase SOA concentrations. 2 Background The framework we chamber with ozone and d-limonene ("terp" in our equations) to quantify Ys,m for ozone and surface

Siegel, Jeffrey

133

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

134

Carbonaceous aerosol in urban and rural European atmospheres: estimation of secondary organic carbon concentrations  

Microsoft Academic Search

Aerosol samples from urban, rural and coastal areas in Europe were analysed for carbonaceous content by a thermaloptical transmission method. The fraction of particulate organic carbon with a secondary origin in gas\\/particle conversion of volatile organic compounds was estimated from the minimum ratio between particulate organic and black carbon, which occurred during periods of reduced photochemical activity. Values calculated by

L. M. Castro; C. A. Pio; Roy M. Harrison; D. J. T. Smith

1999-01-01

135

Primary and secondary organics in the tropical Amazonian rainforest aerosols: chiral analysis of 2-methyltetraols.  

PubMed

This work presents the application of a new method to facilitate the distinction between biologically produced (primary) and atmospherically produced (secondary) organic compounds in ambient aerosols based on their chirality. The compounds chosen for this analysis were the stereomers of 2-methyltetraols, (2R,3S)- and (2S,3R)-methylerythritol, (l- and d-form, respectively), and (2S,3S)- and (2R,3R)-methylthreitol (l- and d-form), shown previously to display some enantiomeric excesses in atmospheric aerosols, thus to have at least a partial biological origin. In this work PM10 aerosol fractions were collected in a remote tropical rainforest environment near Manaus, Brazil, between June 2008 and June 2009 and analysed. Both 2-methylerythritol and 2-methylthreitol displayed a net excess of one enantiomer (either the l- or the d-form) in 60 to 72% of these samples. These net enantiomeric excesses corresponded to compounds entirely biological but accounted for only about 5% of the total 2-methyltetrol mass in all the samples. Further analysis showed that, in addition, a large mass of the racemic fractions (equal mixtures of d- and l-forms) was also biological. Estimating the contribution of secondary reactions from the isomeric ratios measured in the samples (=ratios 2-methylthreitol over 2-methylerythritol), the mass fraction of secondary methyltetrols in these samples was estimated to a maximum of 31% and their primary fraction to a minimum of 69%. Such large primary fractions could have been expected in PM10 aerosols, largely influenced by biological emissions, and would now need to be investigated in finer aerosols. This work demonstrates the effectiveness of chiral and isomeric analyses as the first direct tool to assess the primary and secondary fractions of organic aerosols. PMID:24777436

González, N J D; Borg-Karlson, A-K; Artaxo, P; Guenther, A; Krejci, R; Nozière, B; Noone, K

2014-05-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

139

The analysis of chiral methyltetrols in atmospheric aerosols: A new look at Secondary Organic Aerosols from isoprene  

NASA Astrophysics Data System (ADS)

The quantities of Secondary Organic Aerosols (SOA) produced in the atmosphere by the transformations of organic gases are difficult to estimate, isoprene having possibly and important contribution, but also containing the most uncertainties. One of the main challenges in this topic is the limited information on real atmospheric SOA, as there was, until recently, no method to distinguish unambiguously between secondary and primary organic compounds in atmospheric aerosols. We have developed a new analytical method to make this distinction, based on separating the enantiomers of organic compounds (isomers mirror images of each other) in aerosols. In this work, this method is applied to the 2-methyltetrols, 2-methylerythritol and 2-methylthreitol, present in PM2.5 aerosols collected at Aspvreten, Sweden from May to November 2008. These compounds are currently considered as the main evidence supporting the presence of SOA from isoprene in the atmosphere. The results of our analyses show that these compounds are, at least in part, from biological (or “primary”) origin. In particular, 2-C-methyl-D-erythritol was 15 % in excess of the total mass of 2-methyltetrols in May-July, clearly indicating its biological origin, and consistent with its well-documented production by plants. Furthermore, the concentrations of the remaining racemic diastereoisomers (total 2-methylerythritol and total 2-methylthreitol) did not correlate with each other, implying that at least one of them, or both, were also from biological origin. This was supported by their lack of correlation with ozone at the site. While atmospheric (abiotic) reactions might have contributed, it can not be excluded that these compounds were mostly from biological origin, thus challenging the main evidence for the existence of SOA from isoprene in the atmosphere.

Gonzalez Cantu, N. J.; Noziere, B.; Borg-Karlsson, A.; Pei, Y.; Petersson, J.; Krejci, R.; Artaxo, P.; Baltensperger, U.; Dommen, J.; Prevot, A. S.; Anthonsen, T.

2010-12-01

140

Secondary production of organic aerosols from biogenic VOCs over Mt. Fuji, Japan.  

PubMed

We investigated organic molecular compositions of summertime aerosols collected at the summit of Mt. Fuji (3776 m a.s.l.) in July-August 2009. More than 120 organic species were identified using GC/MS. Concentrations of both primary and secondary organic aerosol (SOA) tracers in whole-day samples were 4-20 times higher than those in nighttime samples, suggesting that valley breeze is an efficient mechanism to uplift the aerosols and precursors from the ground surface to mountaintop in daytime. Using a tracer-based method, we estimated the concentrations of secondary organic carbon (SOC) derived from isoprene, ?/?-pinene, and ?-caryophyllene to be 2.2-51.2 ngC m(-3) in nighttime and 227-1120 ngC m(-3) during whole-day. These biogenic SOCs correspond to 0.80-31.9% and 26.8-57.4% of aerosol organic carbon in nighttime and whole-day samples, respectively. This study demonstrates that biogenic SOA, which is controlled by the valley breeze, is a significant fraction of free tropospheric aerosols over Mt. Fuji in summer. PMID:24999968

Fu, Pingqing; Kawamura, Kimitaka; Chen, Jing; Miyazaki, Yuzo

2014-08-01

141

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

142

Closure study on measured and modeled optical properties for dry and hydrated laboratory inorganic aerosols with mixtures of dicarboxylic acids  

NASA Astrophysics Data System (ADS)

A laboratory-based closure study was completed to compare measured and modeled optical properties and their dependence on controlled relative humidity (RH) for inorganic salts, dicarboxylic acids, and their mixtures. The closure between measured and modeled values of the light scattering coefficients were evaluated by calculating the average relative difference (ARD) values, which revealed agreement within 8.0% for the total scattering (?sp) and 14.8% for the back scattering (?bsp) values at dry RH conditions for all test aerosols. These ARD values were less than the total relative uncertainty based on the measurement and modeling approaches, indicating the achievement of closure for ?sp and ?bsp. Optical properties derived from ?sp including: (1) the hygroscopic growth factor, f?sp, (2) the backscatter ratio, b, and (3) the Ångström exponent, å, were also compared with measured values. The ARD values between corresponding measured and modeled results for these derived optical parameters ranged from 0.1% to 30.8%. The impact of particulate organic matter (POM) on optical and hygroscopic properties of the aerosols tested here was also compared to the aerosol optical and composition measurements that occurred during the New England Air Quality Study-Intercontinental Transport and Chemical Transformation field campaign. Such comparison confirmed that a larger POM mass fraction resulted in less hygroscopicity for both the ambient and the laboratory aerosols. This study evaluated closure between laboratory measurements and model calculations and validated the reliability of the measured and modeled results with the closure analysis. Therefore, Mie-Lorentz model can be used to calculate the optical properties and their dependence on RH for other aerosols with more confidence.

Deng, Junjun; Du, Ke; Wang, Wei; Rood, Mark J.

2013-12-01

143

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

144

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

145

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

Microsoft Academic Search

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

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

2003-01-01

146

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

147

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

148

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

149

Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation  

NASA Astrophysics Data System (ADS)

The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of ?-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, several simplified model approaches are tested with regard to computational costs and accuracy of predictions compared to the benchmark calculation. It is shown that forcing a liquid one-phase aerosol with or without consideration of non-ideal mixing bears the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, by more than 100% at RH values of 80% and by more than 200% at RH values of 95%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and organics that cannot be ignored. Computationally much more efficient calculations relying on the assumption of a complete organic/electrolyte phase separation below a certain RH successfully reproduce gas-particle partitioning in systems in which the average oxygen-to-carbon (O:C) ratio is lower than ~0.6, as in the case of ?-pinene SOA, and bear the potential for implementation in atmospheric chemical transport models and chemistry-climate models. A full equilibrium calculation is the method of choice for accurate offline (box model) computations, where high computational costs are acceptable. Such a calculation enables the most detailed predictions of phase compositions and provides necessary information on whether assuming a complete organic/electrolyte phase separation is a good approximation for a given aerosol system. Based on the group-contribution concept of AIOMFAC and O:C ratios as a proxy for polarity and hygroscopicity of organic mixtures, the results from the ?-pinene system are also discussed from a more general point of view.

Zuend, A.; Seinfeld, J. H.

2012-05-01

150

Emissions and Secondary Organic Aerosol Production from Semivolatile and Intermediate Volatility Organic Compounds  

NASA Astrophysics Data System (ADS)

Organic aerosols are a highly-dynamic system dominated by both variable gas-particle partitioning and chemical evolution. Important classes of organics include semivolatile and intermediate volatility organic compounds (SVOC and IVOC, respectively). SVOCs are compounds that exist in both the gas and particle phases at typical atmospheric conditions while IVOC are low-volatility vapors that exist exclusively in the gas phase. Both classes have saturation concentrations that are orders of magnitude lower than volatile organic compounds (VOC) that are the traditional subjects of atmosphere chemistry, such as monoterpenes, alkyl benzenes, etc. The SVOC and IVOC are poorly represented for in current atmospheric chemistry models. Source testing indicates that SVOC and IVOC emissions from biomass combustion, diesel engines and other sources exceed the primary organic aerosol emissions; thus the oxidation of these vapors could serve as a significant source of organic aerosol in the atmosphere. The formation of secondary organic aerosol (SOA) from the reactions between OH radicals and SVOCs and IVOCs was investigated in the Carnegie Mellon University smog chamber. Experiments were conducted with n-alkanes and emission surrogates (diesel fuel and lubricating oil). SVOC oxidation produces oxidized organic aerosol but little new organic aerosol mass. This behavior can be explained by the coupled effects of partitioning and aging. Oxidation of SVOC vapors creates low volatility species that partition into the condensed phase; this oxidation also reduces the SVOC vapor concentration which, in turn, requires particle-phase SVOC to evaporate to maintain phase equilibrium. In contrast, oxidation of IVOC results in sustained production of SOA consistent with a reaction with relatively slow kinetics and high mass yield. Aerosol Mass Spectrometer data indicates that the SOA formed from IVOC has a mass spectrum that is quite similar to the oxygenated organic aerosol factor observed in field studies.

Robinson, A. L.; Presto, A. A.; Miracolo, M. A.; Donahue, N. M.; Kroll, J. H.; Worsnop, D. R.

2008-12-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

152

The Potential of Amorphous Solid Secondary Organic Aerosol to Form Mixed-Phase and Cirrus Clouds  

NASA Astrophysics Data System (ADS)

Atmospheric ice formation by heterogeneous nucleation, which results in cirrus and mixed-phase cloud formation, is one of the least understood processes affecting the global radiation budget, the hydrological cycle, and water vapor distribution. It is commonly assumed that inorganic particles such as mineral dust and solid ammonium sulfate represent important atmospheric ice nuclei (IN). However, a growing body of evidence suggests that secondary organic aerosols (SOA), which are ubiquitous in the atmosphere, exist in a solid (glassy) state. This implies that SOA may also play a role in ice cloud formation by acting as IN, but has not previously been experimentally verified. Here, we report observations of water uptake and ice nucleation via condensation, immersion, and deposition modes initiated by amorphous SOA particles at temperatures from T = 200 - 250 K and relative humidity (RH) from subsaturation conditions up to water saturation. SOA particles with oxygen-to-carbon (O/C) ratios ranging from 0.3 to 1.0 are generated from gas-phase OH oxidation of naphthalene in a flow reactor. At T > 230 K, water uptake at subsaturation conditions is correlated with SOA oxidation level (O/C ratio). This initial water uptake is followed by a moisture-induced phase transition and subsequent immersion freezing. At T < 230 K, the SOA forms ice via deposition nucleation at RH with respect to ice 10-15% below the homogeneous ice nucleation limit, with no apparent dependence on oxidation level. The SOA glass transition temperature (Tg) is estimated as a function of RH, temperature, and SOA oxidation level from corresponding measurements of particle density, hygroscopicity, and bounced fraction, the latter indicating particle phase state. Above Tg, water uptake and immersion freezing is observed when the particles are liquid or semi-solid. Below Tg, deposition ice nucleation is observed when the particles are solid. The data show that particle phase and viscosity govern the particles' response to temperature and RH and provide a straightforward interpretation for the observed different heterogeneous ice nucleation pathways and water uptake by the laboratory-generated SOA and previously investigated fulvic acid surrogate particles and organic dominated field-collected particles. These observations suggest that atmospheric ubiquitous SOA are potentially important for ice cloud formation and climate and should be investigated in future cloud resolving and climate modeling studies.

Knopf, D. A.; Wang, B.; Lambe, A. T.; Massoli, P.; Onasch, T. B.; Davidovits, P.; Worsnop, D. R.

2012-12-01

153

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

PubMed Central

Isoprene and monoterpenes are important precursors of secondary organic aerosols (SOA) in continents. However, their contributions to aerosols over oceans are still inconclusive. Here we analyzed SOA tracers from isoprene and monoterpenes in aerosol samples collected over oceans during the Chinese Arctic and Antarctic Research Expeditions. Combined with literature reports elsewhere, we found that the dominant tracers are the oxidation products of isoprene. The concentrations of tracers varied considerably. The mean average values were approximately one order of magnitude higher in the Northern Hemisphere than in the Southern Hemisphere. High values were generally observed in coastal regions. This phenomenon was ascribed to the outflow influence from continental sources. High levels of isoprene could emit from oceans and consequently have a significant impact on marine SOA as inferred from isoprene SOA during phytoplankton blooms, which may abruptly increase up to 95?ng/m3 in the boundary layer over remote oceans. PMID:23880782

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

2013-01-01

154

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

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of ?-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 ?g m-3. The yields (0.5 to 9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (?8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86-0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. The SOA yields, O/C, and f44 (the mass fraction of CO2+ ions in the mass spectra which can be considered as a measure of carboxylic groups) in the mixed photo-chemical experiments could be described as linear combinations of the corresponding properties of the pure systems. For VFR there was in addition an enhancement effect, making the mixed aerosol significantly less volatile than what could be predicted from the pure systems. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. Thus, this change in volatility under dark conditions as well as the anthropogenic enhancement is due to chemical or morphological changes not affecting O/C.

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

2013-03-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

156

Evaluating Simulated Primary Anthropogenic and Biomass Burning Organic Aerosols during MILAGRO: Implications for Assessing Treatments of Secondary Organic Aerosols  

SciTech Connect

Simulated primary organic aerosols (POA), as well as other particulates and trace gases, in the vicinity of Mexico City are evaluated using measurements collected during the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaigns. Since the emission inventories and dilution will affect predictions of total organic matter and consequently total particulate matter, our objective is to assess the uncertainties in predicted POA before testing and evaluating the performance of secondary organic aerosol (SOA) treatments. Carbon monoxide (CO) is well simulated on most days both over the city and downwind, indicating that transport and mixing processes were usually consistent with the meteorological conditions observed during MILAGRO. Predicted and observed elemental carbon (EC) in the city was similar, but larger errors occurred at remote locations since the CO/EC emission ratios in the national emission inventory were lower than in the metropolitan emission inventory. Components of organic aerosols derived from Positive Matrix Factorization and data from several Aerodyne Aerosol Mass Spectrometer instruments deployed both at ground sites and on research aircraft are used to evaluate the model. Predicted POA was consistently lower than the measured organic matter at the ground sites, which is consistent with the expectation that SOA should be a large fraction of the total organic matter mass. A much better agreement was found when predicted POA was compared with the sum of "primary anthropogenic" and "primary biomass burning" components on days with relatively low biomass burning, suggesting that the overall magnitude of primary organic particulates released was reasonable. The predicted POA was greater than the total observed organic matter when the aircraft flew directly downwind of large fires, suggesting that biomass burning emission estimates from some large fires may be too high. Predicted total observed organic carbon (TOOC) was also analyzed to assess how emission inventory estimates of volatile organic compounds may impact predictions of SOA.

Fast, Jerome D.; Aiken, Allison; Allan, James D.; Alexander, M. L.; Campos, Teresa; Canagaratna, Manjula R.; Chapman, Elaine G.; DeCarlo, Peter; de Foy, B.; Gaffney, Jeffrey; de Gouw, Joost A.; Doran, J. C.; Emmons, L.; Hodzic, Alma; Herndon, Scott C.; Huey, L. G.; Jayne, John T.; Jimenez, Jose L.; Kleinman, Lawrence I.; Kuster, W. C.; Marley, Nancy A.; Russell, Lynn M.; Ochoa, Carlos; Onasch, Timothy B.; Pekour, Mikhail S.; Song, Chen; Ulbrich, Ingrid M.; Warneke, Carsten; Welsh-Bon, Daniel; Wiedinmyer, Christine; Worsnop, Douglas R.; Yu, Xiao-Ying; Zaveri, Rahul A.

2009-08-31

157

Link between isoprene and secondary organic aerosol (SOA): Pyruvic acid oxidation yields low volatility organic acids in clouds  

E-print Network

Link between isoprene and secondary organic aerosol (SOA): Pyruvic acid oxidation yields low volatility organic acids in clouds Annmarie G. Carlton,1 Barbara J. Turpin,1 Ho-Jin Lim,2 Katye E. Altieri,3 source of organic aerosol and could explain the atmospheric presence of oxalic acid. Methylglyoxal

Seitzinger, Sybil

158

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

EPA Science Inventory

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

159

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

E-print Network

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

Silver, Whendee

160

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

EPA Science Inventory

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

161

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

162

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

163

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

164

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

165

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

NASA Astrophysics Data System (ADS)

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

Zhang, J.

2003-12-01

166

Contrasting diurnal variations in fossil and nonfossil secondary organic aerosol in urban outflow, Japan.  

PubMed

Diurnal variations of fossil secondary organic carbon (SOC) and nonfossil SOC were determined for the first time using a combination of several carbonaceous aerosol measurement techniques, including radiocarbon (¹?C) determinations by accelerator mass spectrometry, and a receptor model (chemical mass balance, CMB) at a site downwind of Tokyo during the summer of 2007. Fossil SOC showed distinct diurnal variation with a maximum during daytime, whereas diurnal variation of nonfossil SOC was relatively small. This behavior was reproduced by a chemical transport model (CTM). However, the CTM underestimated the concentration of anthropogenic secondary organic aerosol (ASOA) by a factor of 4-7, suggesting that ASOA enhancement during daytime is not explained by production from volatile organic compounds that are traditionally considered major ASOA precursors. This result suggests that unidentified semivolatile organic compounds or multiphase chemistry may contribute largely to ASOA production. As our knowledge of production pathways of secondary organic aerosol (SOA) is still limited, diurnal variations of fossil and nonfossil SOC in our estimate give an important experimental constraint for future development of SOA models. PMID:20886860

Morino, Yu; Takahashi, Katsuyuki; Fushimi, Akihiro; Tanabe, Kiyoshi; Ohara, Toshimasa; Hasegawa, Shuichi; Uchida, Masao; Takami, Akinori; Yokouchi, Yoko; Kobayashi, Shinji

2010-11-15

167

Fog scavenging of organic and inorganic aerosol in the Po Valley  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

168

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

NASA Astrophysics Data System (ADS)

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

Flores, Rosa M.; Doskey, Paul V.

2014-10-01

169

Time-resolved distributions of bulk parameters, diacids, ketoacids and ?-dicarbonyls and stable carbon and nitrogen isotope ratios of TC and TN in tropical Indian aerosols: Influence of land/sea breeze and secondary processes  

NASA Astrophysics Data System (ADS)

To better understand the photochemical production and diurnal distributions of organic and inorganic aerosols in the tropical coastal Indian atmosphere, the aerosol (TSP) samples were collected every 3 h during 30-31 January, 14-15 February and 28-29 May 2007 from Chennai and studied for total carbon (TC) and nitrogen (TN) and their stable isotope ratios (?13CTC and ?15NTN), carbonaceous components, inorganic ions, diacids, ketoacids and ?-dicarbonyls. Time-resolved distributions of bulk parameters, inorganic ions, and diacids and related compounds, except for few species, did not show any clear diurnal trend but showed peaks at 6-9 h during all the study periods, except for the peak at 15-18 h on 28 May. SO42-, C2 - C6 diacids, ketoacids and ?-dicarbonyls in February and on 29 May showed a diurnal trend. ?13CTC and ?15NTN stayed relatively constant during the study periods but showed 13C depletion (in January) and 15 N enrichment when TC and TN peaked. Based on these results together with air mass trajectories, we found that the diurnal distributions of Chennai aerosols are mainly influenced by land/sea breeze and the aged (photochemically processed) air masses, although in situ photochemical production and nighttime chemistry of secondary aerosol species, particularly C2-C4 diacids and SO42-, are significant. The characteristics of seasonal variations of carbonaceous components, and diacids and related compounds and comparisons of ?13CTC and ?15NTN of Chennai aerosols with the isotopic signatures of the point sources inferred that biofuel/biomass burning in South and Southeast Asia are the major sources of aerosols (TSP).

Pavuluri, Chandra Mouli; Kawamura, Kimitaka; Swaminathan, T.

2015-02-01

170

Particle size distribution of major inorganic species in atmospheric aerosols from Majorca (Spain)  

Microsoft Academic Search

Atmospheric aerosols collected by means of a cascade impaction system at the campus of the University of the Balearic Islands (Majorca, Spain) from November 1993 to February 1994 were analysed for chloride, nitrate, sulphate, ammonium, calcium, magnesium, sodium and potassium. Based on particle size distribution, the species studied were classified into three groups: (a) concentration decrease with particle size (sulphate

J. Mateu; R. Forteza; V. Cerdà; M. Colom-Altés

1995-01-01

171

Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores  

NASA Astrophysics Data System (ADS)

Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps), are here used to reconstruct past aerosol load and composition of the free European troposphere from before World War II to present. Available ice core records include inorganic (Na+, Ca2+, NH4+, Cl-, NO3-, and SO42-) and organic (carboxylates, HCHO, humic-like substances, dissolved organic carbon, water-insoluble organic carbon, and black carbon) compounds and fractions that permit reconstructing the key aerosol components and their changes over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921-1951 to 1971-1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). Thus, not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water-soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarios dealing with climate forcing by atmospheric aerosol.

Preunkert, S.; Legrand, M.

2013-07-01

172

Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores  

NASA Astrophysics Data System (ADS)

Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps) are here revisited in view to reconstruct past aerosol load of the free European troposphere from prior World War II to present. The extended array of inorganic (Na+, Ca2+, NH4+, Cl-, NO3-, and SO42-) and organic (carboxylates, HCHO, HUmic LIke Substances, dissolved organic carbon, water insoluble organic carbon, and black carbon) compounds and fractions already investigated permit to examine the overall aerosol composition and its change over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921-1951 to 1971-1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). It is shown that not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarii dealing with climate forcing by atmospheric aerosol.

Preunkert, S.; Legrand, M.

2013-02-01

173

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

PubMed

The presence of ice dominates the microphysics of formation of high altitude cirrus and polar stratospheric clouds, as well as the maturity of thunderstorms. We report on the hexagonal (1h) ice stability and growth in binary as well as multi-compound aerosols in atmospherically relevant conformations. The ubiquitous atmospheric trace gas glyoxal along with secondary organic aerosol (SOA) also in the presence of CO2 interacts with large ice 1h crystals of 1300-2000 water molecules. The crystals are subjected to phase transitions under superheating and supercooling conditions by Molecular Dynamics (MD) simulations. Density Functional Theory (DFT) based geometry optimization and vibrational frequency analysis are also employed for a smaller ice 1h cell of 12 water molecules. The interaction of the latter with each organic molecule reveals the extent of the mechanical stress exerted on the ordered ice structure. Full hydration of glyoxal promotes ice 1h stability and growth in wet aerosols, while partial hydration or full oxidation exerts a destabilizing effect on the ice 1h lattice. This behavior is associated with the ability of each organic phase to match the order of the ice 1h crystal. We propose that aqueous chemistry in wet aerosols may also have a strong effect on the microphysics of cloud formation. PMID:25033409

Daskalakis, Vangelis; Hadjicharalambous, Marios

2014-09-01

174

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

175

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

2014-02-01

176

Chamber studies to simulate secondary organic aerosol formation from the Deepwater Horizon oil spill  

NASA Astrophysics Data System (ADS)

Because atmospheric organic species are generally emitted from a large number of sources, over wide spatial and temporal scales, it is generally challenging to ascribe ambient organic aerosol (OA) to the oxidation of specific secondary organic aerosol (SOA) precursors. However, the Deepwater Horizon (DWH) oil spill (April 20-July 15, 2010), provided the unique circumstance of a large, well-defined source of gas-phase organics introduced into a relatively clean atmosphere. Here we describe a laboratory simulation of SOA formation downwind of the DWH spill, via the oxidation of South Louisiana-light (SL) crude oil by OH radicals in an environmental chamber. Intermediate and semi-volatile fractions of the SL crude oil are vaporized and oxidized by gas-phase OH radicals (formed from the photolysis of HONO). The chemical composition is monitored as a function of OH exposure. When OH exposures are approximately matched, laboratory-generated SOA and OA measured downwind of the oil spill exhibit extremely similar aerosol mass spectra, in strong support of the hypothesis that the OA measured downwind of the DWH oil spill was secondary in nature. More generally, this agreement indicates that in cases when SOA precursors are well-constrained, chamber experiments can reasonably reproduce key properties of ambient OA. Results of chamber studies on sub-fractions of the SL crude oil, aimed at identifying the classes of oil components most responsible for SOA formation, will be discussed.

Daumit, K. E.; Carrasquillo, A. J.; Cross, E. S.; Hunter, J. F.; Bahreini, R.; Middlebrook, A. M.; De Gouw, J. A.; Williams, L. R.; Worsnop, D. R.; Kroll, J. H.

2011-12-01

177

Partial Derivative Fitted Taylor Expansion: An efficient method for calculating gas-liquid equilibria in atmospheric aerosol particles: 1. Inorganic compounds  

NASA Astrophysics Data System (ADS)

Parameterizations for calculating the equilibrium vapor pressure of the semivolatile inorganic gases, HNO3, HCl, and NH3, above an aqueous aerosol are presented. The hybrid Partial Derivative Fitted Taylor Expansion (PD-FiTE) approach uses optimized model parameters describing the interaction between different inorganic ions, resulting in comparable computational performance with existing reduced methods while remaining accurate. Comparisons with the most accurate inorganic activity coefficient model available indicate that PD-FiTE performs very well over the parameterization space of the system H+-NH4+-Na+-SO42--HSO4--NO3--Cl- at 298.15 K. The linear additive framework allows the inclusion of further species. However, including the ability to describe the interaction between inorganic and organic components will be presented in a future publication. Coupling PD-FiTE to a coupled box model of gaseous chemistry and aerosol microphysics in a test case investigating marine aerosol passing through a polluted environment demonstrates its robustness and ability to capture fine details of important phenomena such as the outgassing of HCl in response to HNO3 uptake by sea-salt particles.

Topping, David; Lowe, Douglas; McFiggans, Gordon

2009-02-01

178

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

179

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. PMID:24115805

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

2013-01-01

180

Physical Properties of Ambient and Laboratory-Generated Secondary Organic Aerosol  

SciTech Connect

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

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

2014-06-17

181

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

182

An examination of oxidant amounts on secondary organic aerosol formation and aging  

NASA Astrophysics Data System (ADS)

The effect of HOx radicals (OH and HO2) and ozone (O3) on secondary organic aerosol (SOA) formation and aging has been studied. Experiments were performed in the presence and in the absence of oxygen in a small chamber (~18 liters) for several organic precursor gases, including m-xylene, alpha-pinene and ethylbenzene. The HOx source was the UV photolysis of humidified air or nitrogen and was measured with the Penn State GTHOS (Ground-based Tropospheric Hydrogen Oxides Sensor). The precursor gases concentration was monitored with an online GC-FID. The aerosol mass was then quantified by a Tapered Element Oscillating Microbalance (TEOM). Typical oxidant mixing ratios were (0.??? -10) ppm for O3, (10-400) pptv for OH and (0.1-4) ppb for HO2. The SOA yields for different oxidant conditions will be discussed.

Chen, Z.; Ren, X.; Brune, W. H.

2007-12-01

183

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

PubMed Central

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

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

2014-01-01

184

Comprehensive characterisation of atmospheric aerosols in Budapest, Hungary: physicochemical properties of inorganic species  

NASA Astrophysics Data System (ADS)

As part of an air pollution project in Budapest, aerosol samples were collected by stacked filter units and cascade impactors at an urban background site, two downtown sites, and within a road tunnel in field campaigns conducted in 1996, 1998 and 1999. Some criteria pollutants were also measured at one of the downtown sites. The aerosol samples were analysed by one or more of the following methods: instrumental neutron activation analysis, particle-induced X-ray emission analysis, a light reflection technique, gravimetry, thermal profiling carbon analysis and capillary electrophoresis. The quantities measured or derived include atmospheric concentrations of elements (from Na to U), of particulate matter, of black and elemental carbon, and total carbonaceous fraction, of some ionic species (e.g., nitrate and sulphate) in the fine ( <2 ?m equivalent aerodynamic diameter, EAD) or in both coarse (10- 2 ?m EAD) and fine size fractions, atmospheric concentrations of NO, NO 2, SO 2, CO and total suspended particulate matter, and meteorological parameters. The analytical results were used for characterisation of the concentration levels, elemental composition, time trends, enrichment of and relationships among the aerosol species in coarse and fine size fractions, for studying their fine-to-coarse concentration ratios, spatial and temporal variability, for determining detailed elemental mass size distributions, and for examining the extent of chemical mass closure.

Salma, Imre; Maenhaut, Willy; Zemplén-Papp, Éva; Záray, Gyula

185

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

PubMed

PM(2.5), as one of the criteria pollutants regulated in the U.S. and other countries due to its adverse health impacts, contains more than hundreds of organic pollutants with different sources and formation mechanisms. Daytime and nighttime PM2.5 samples from the August Mini-Intensive Gas and Aerosol Campaign (AMIGAS) in the southeastern U.S. were collected during summer 2008 at one urban site and one rural site, and were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and various individual organic compounds including some important tracers for carbonaceous aerosol sources by gas chromatography-mass spectrometry. Most samples exhibited higher daytime OC concentration, while higher nighttime OC was found in a few events at the urban site. Sources, formation mechanisms and composition of organic aerosol are complicated and results of this study showed that it exhibited distinct diurnal variations. With detailed organic tracer information, sources contributing to particulate OC were identified: higher nighttime OC concentration occurring in several occasions was mainly contributed by the increasing primary emissions at night, especially diesel exhaust and biomass burning; whereas sources responsible for higher daytime OC concentration included secondary organic aerosol (SOA) formation (e.g., cis-pinonic acid and non-biomass burning WSOC) together with traffic emissions especially gasoline engine exhaust. Primary tracers from combustion related sources such as EC, polycyclic aromatic hydrocarbons, and hopanes and steranes were significantly higher at the urban site with an urban to rural ratio between 5 and 8. However, this urban-rural difference for secondary components was less significant, indicating a relatively homogeneous distribution of SOA spatially. We found cholesterol concentrations, a typical tracer for meat cooking, were consistently higher at the rural site especially during the daytime, suggesting the likely additional sources for this tracer at rural site and that it should be used with caution as meat cooking tracer in rural areas in the future. PMID:24262212

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

2014-01-15

186

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

187

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

NASA Astrophysics Data System (ADS)

We present a new mobile environmental reaction chamber for the simulation of the atmospheric aging of different emission sources without limitation from the instruments or facilities available at any single site. Photochemistry is simulated using a set of 40 UV lights (total power 4 KW). Characterisation of the emission spectrum of these lights shows that atmospheric aging of emissions may be simulated over a range of temperatures (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was determined at 25 °C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total organic aerosol (OA; primary organic aerosol (POA) emission + secondary organic aerosol (SOA) formation) was (369.8-397.5)10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the composition of the gas phase emissions suggests that the observed SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.

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

2013-09-01

188

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

NASA Astrophysics Data System (ADS)

The increasing demand for palm oil for uses in biofuel and food products is leading to rapid expansion of oil palm agriculture. Methyl chavicol (also known as estragole and 1-allyl-4-methoxybenzene) is an oxygenated biogenic volatile organic compound that was recently identified as the main floral emission from an oil palm plantation in Malaysian Borneo. The emissions of methyl chavicol observed may impact regional atmospheric chemistry, but little is known of its ability to form secondary organic aerosol (SOA). The photo-oxidation of methyl chavicol was investigated at the European Photoreactor chamber as a part of the atmospheric chemistry of methyl chavicol (ATMECH) project. Aerosol samples were collected using a particle into liquid sampler (PILS) and analysed offline using an extensive range of instruments including; high performance liquid chromatography mass spectrometry (HPLC-ITMS), high performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-QTOFMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The SOA yield was determined as 18-29% depending on initial precursor (VOC : NOx) mixing ratios. In total, 59 SOA compounds were observed and the structures of 10 compounds have been identified using high resolution tandem mass spectrometry. The addition of hydroxyl and/or nitro functional groups to the aromatic ring appears to be an important mechanistic pathway for aerosol formation. This results in the formation of compounds with both low volatility and high O : C ratios, where functionalisation rather than fragmentation is mainly observed as a~result of the stability of the ring. The SOA species observed can be characterized as semi-volatile to low volatile oxygenated organic aerosol (SVOOA and LVOOA) components and therefore may be important in aerosol formation and growth.

Pereira, K. L.; Hamilton, J. F.; Rickard, A. R.; Bloss, W. J.; Alam, M. S.; Camredon, M.; Muñoz, A.; Vásquez, M.; Borrás, E.; Ródenas, M.

2013-12-01

189

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

PubMed Central

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

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

2011-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

192

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

NASA Astrophysics Data System (ADS)

A series of smog chamber experiments were conducted to investigate the transformation of primary organic aerosol (POA) and formation of secondary organic aerosol (SOA) during the photooxidation of dilute exhaust from a fleet of gasoline and diesel motor vehicles and two gas-turbine engines. In experiments where POA was present in the chamber at the onset of photooxidation, positive matrix factorization (PMF) was used to determine separate POA and SOA factors from aerosol mass spectrometer data. A 2-factor solution, with one POA factor and one SOA factor, was sufficient to describe the organic aerosol for gasoline vehicles, diesel vehicles, and one of the gas-turbine engines. Experiments with the second gas-turbine engine required a 3-factor PMF solution with a POA factor and two SOA factors. Results from the PMF analysis were compared to the residual method for determining SOA and POA mass concentrations. The residual method apportioned a larger fraction of the organic aerosol mass as POA because it assumes that all mass at m / z 57 is associated with POA. The POA mass spectrum for the gasoline and diesel vehicles exhibited high abundances of the CnH2n+1 series of ions (m / z 43, 57, etc.) and was similar to the mass spectra of the hydrocarbon-like organic aerosol factor determined from ambient data sets with one exception, a diesel vehicle equipped with a diesel oxidation catalyst. POA mass spectra for the gas-turbine engines are enriched in the CnH2n-1 series of ions (m / z 41, 55, etc.), consistent with the composition of the lubricating oil used in these engines. The SOA formed from the three sources exhibits high abundances of m / z 44 and 43, indicative of mild oxidation. The SOA mass spectra are consistent with less-oxidized ambient SV-OOA (semivolatile oxygenated organic aerosols) and fall within the triangular region of f44 versus f43 defined by ambient measurements. However there is poor absolute agreement between the experimentally derived SOA mass spectra and ambient OOA factors, though this poor agreement should be expected based on the variability of ambient OOA factors. Van Krevelen analysis of the POA and SOA factors for gasoline and diesel experiments reveal slopes of -0.50 and -0.40, respectively. This suggests that the oxidation chemistry in these experiments is a combination of carboxylic acid and alcohol/peroxide formation, consistent with ambient oxidation chemistry.

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

2014-05-01

193

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

SciTech Connect

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.

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

2011-07-18

194

Investigating Primary Marine Aerosol Properties: CCN Activity of Sea Salt and Mixed Inorganic–Organic Particles  

PubMed Central

Sea spray particles ejected as a result of bubbles bursting from artificial seawater containing salt and organic matter in a stainless steel tank were sampled for size distribution, morphology, and cloud condensation nucleus (CCN) activity. Bubbles were generated either by aeration through a diffuser or by water jet impingement on the seawater surface. Three objectives were addressed in this study. First, CCN activities of NaCl and two types of artificial sea salt containing only inorganic components were measured to establish a baseline for further measurements of mixed organic–inorganic particles. Second, the effect of varying bubble residence time in the bulk seawater solution on particle size and CCN activity was investigated and was found to be insignificant for the organic compounds studied. Finally, CCN activities of particles produced from jet impingement were compared with those produced from diffuser aeration. Analyses indicate a considerable amount of organic enrichment in the jet-produced particles relative to the bulk seawater composition when sodium laurate, an organic surfactant, is present in the seawater. In this case, the production of a thick foam layer during impingement may explain the difference in activation and supports hypotheses that particle production from the two methods of generating bubbles is not equal. PMID:22809370

2012-01-01

195

Aqueous glyoxal photooxidation in the presence of inorganic nitrogen: A potential source of organic nitrogen in aerosols and wet deposition  

NASA Astrophysics Data System (ADS)

The sources of organic nitrogen in aerosols and atmospheric wet deposition are poorly understood, yet are important when assessing potential anthropogenic impacts on global nitrogen budgets. Nitrogen-containing organics are formed through gas phase photochemistry (e.g., involving NOx and isoprene). Imidazoles have been reported to form during smog chamber experiments involving glyoxal and ammonium sulfate seed particles. We hypothesize that nitrogen-containing organic compounds also form during cloud processing of water-soluble organic gases. Specifically, in this work we examine the possibility that organic nitrogen forms from GLY and inorganic nitrogen (NO3- or NH4+) at conditions found in daytime liquid clouds. We conducted batch aqueous reactions of GLY (1 mM) and OH radical (~10^-12 M) with and without nitric acid (1.7 mM) and ammonium sulfate (0.84 mM). OH radical was formed from the continuous photolysis of H2O2. Products were analyzed by ion chromatography (IC) and electrospray ionization mass spectrometry with pre-separation by IC (IC/ESI-MS). The addition of ammonium or nitrate had little effect on the concentrations of major system species (i.e., oxalate, glycolate) in the presence and absence of OH radical. Concentrations of inorganic nitrate and sulfate showed no significant change throughout light and dark experiments. ESI mass spectra with and without pre-separation by IC and ultra high resolution Fourier transform ion cyclotron resonance mass spectral analysis of samples will be examined and any evidence of organic nitrogen products will be discussed.

Kirkland, J. R.; Tan, Y.; Altieri, K. E.; Seitzinger, S.; Turpin, B. J.

2010-12-01

196

[Characteristics of aerosol water-soluble inorganic ions in three types air-pollution incidents of Nanjing City].  

PubMed

In order to compare aerosol water-soluble inorganic species in different air-pollution periods, samples of PM10, PM2.1, PM1.1 and the main water-soluble ions (NH4+, Mg2+, Ca2+, Na+, K+, NO2(-), F(-), NO3(-), Cl(-), SO4(2-)) were measured, which were from 3 air-pollution incidents (continued pollution in October 16-30 of 2009, sandstorm pollution in April 27-30 of 2010, and crop burning pollution in June 14 of 2010. The results show that aerosol pollution of 3 periods is serious. The lowest PM2.1/PM10 is only 0.27, which is from sandstorm pollution period, while the largest is 0. 7 from crop burning pollution period. In continued pollution periods, NO3(-) and SO4(2-) are the dominant ions, and the total anions account for an average of 18.62%, 32.92% and 33.53% of PM10, PM2.1 and PM1.1. Total water-soluble ions only account for 13.36%, 23.72% and 28.54% of PM10, PM2.1 and PM1.1 due to the insoluble species is increased in sandstorm pollution period. The mass concentration of Ca2+ in sandstorm pollution period is higher than the other two pollution periods, and which is mainly in coarse particles with diameter larger than 1 microm. All the ten water-soluble ions are much higher in crop burning pollution especially K+ which is the tracer from crop burning. The peak mass concentrations of NO3(-), SO4(2-) and NH4+ are in 0.43-0.65 microm. PMID:22946180

Zhang, Qiu-Chen; Zhu, Bin; Su, Ji-Feng; Wang, Hong-Lei

2012-06-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

199

Effects of NOx on the volatility of secondary organic aerosol from isoprene photooxidation  

SciTech Connect

The effects of NOx on the volatility of the secondary organic aerosol (SOA) formed from isoprene photooxidation are investigated in environmental chamber experiments. Two types of experiments are performed. In HO2-dominant experiments, organic peroxy radicals (RO2) primarily react with HO2. In mixed experiments, RO2 reacts through multiple pathways. The volatility and oxidation state of isoprene SOA is sensitive to and displays a non-linear dependence on NOx levels. When initial NO/isoprene ratio is approximately 3 (ppbv:ppbv), SOA are shown to be most oxidized and least volatile, associated with the highest SOA yield. A High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) is applied to characterize the key chemical properties of aerosols. While the composition of SOA in mixed experiments does not change substantially over time, SOA become less volatile and more oxidized as oxidation progresses in HO2-dominant experiments. Analysis of the SOA composition suggests that the further reactions of organic peroxides and alcohols may produce carboxylic acids, which might play a strong role in SOA aging.

Xu, Lu; Kollman, Matthew S.; Song, Chen; Shilling, John E.; Ng, L. N.

2014-01-28

200

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

NASA Astrophysics Data System (ADS)

Aromatic hydrocarbons comprise a significant fraction of volatile organic compounds in the urban atmosphere and their importance as precursors to secondary organic aerosols (SOA) has been widely recognized. However, SOA formation from aromatics is one of the least understood processes among all the classes of volatile organic compounds (VOCs) due to its complex multi-generation reactions. Phenolic compounds have been identified as one of the significant products from OH-initiated reaction of aromatic hydrocarbons and are suggested to have a very high potential of SOA formation (e.g., cresol isomers having SOA yield 9~42%, Henry et al., Atmos. Environ., 2008). We examined the effect of extent of oxidation of m-xylene on chemical composition and physical properties using m-xylene and xylenol as reactants in environmental chamber experiments. Chemical composition of SOA was investigated by Liquid Chromatography / Time of Flight Mass Spectrometer (LC/ToF-MS), and Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Physical properties of SOA such as density, volatility, and hygroscopicity were investigated by Aerosol Particle Mass Analyzer - Scanning Mobility Particle Sizer (APM-SMPS), Hygroscopicity/Volatility - Tandem Differential Mobility Analyzer (H/V-TDMA), respectively. Also SOA yields were obtained to evaluate the importance of xylenol as an intermediate product.

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

2009-12-01

201

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

NASA Astrophysics Data System (ADS)

Emissions from gasoline and diesel vehicles are predominant anthropogenic sources of reactive gas-phase organic carbon and key precursors to Secondary Organic Aerosol (SOA) in urban areas. Their relative importance for aerosol formation is a controversial issue with implications for air quality control policy and public health. Using novel gas chromatography and mass spectrometry methods, we analyzed liquid gasoline and diesel fuel collected across the state of California during Summer 2010 and used it to assess field data from the CalNex (California at the Nexus of Air Quality and Climate Change) Bakersfield supersite and the Caldecott Tunnel in Oakland, CA. We present the most comprehensive data to date on the chemical composition, mass distribution, emissions, and SOA formation potential of gasoline and diesel sources. We find that diesel exhaust is 7 times more efficient at forming aerosol than gasoline exhaust and emits twice as much gas-phase organic carbon per liter of fuel burned. Yet, both sources are important for air quality; depending on a region's fuel use, diesel is responsible for 65-90% of vehicular-derived SOA, with substantial contributions from both aromatic and aliphatic hydrocarbons. We assess our results in the context of other studies and discuss their implications for regional air pollution policies, fuel regulations, and methodologies for future measurement, laboratory, and modeling studies.

Gentner, D. R.; Isaacman, G.; Worton, D. R.; Chan, A. W.; Dallmann, T. R.; Davis, L.; Liu, S.; Day, D. A.; Russell, L. M.; Wilson, K. R.; Weber, R.; Guha, A.; Harley, R. A.; Goldstein, A. H.

2012-12-01

202

Secondary organic aerosol formation and organic nitrate yield from NO3 oxidation of biogenic hydrocarbons.  

PubMed

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

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

2014-10-21

203

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

SciTech Connect

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

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

2011-04-14

204

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

PubMed Central

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

2014-01-01

205

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

206

Secondary aerosol formation from photochemical aging of aircraft exhaust in a smog chamber  

NASA Astrophysics Data System (ADS)

Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85 %). Photo-oxidation created substantial secondary particulate matter (PM), greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 for the 4, 7, 30, and 85 % load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4 % load, secondary PM was dominated by secondary organic aerosol (SOA). At higher loads, the secondary PM was mainly secondary sulfate. A traditional SOA model that accounts for SOA formation from single-ring aromatics and other volatile organic compounds underpredicts the measured SOA formation by ~60 % at 4 % load and ~40 % at 85 % load. Large amounts of lower-volatiliy organic vapors were measured in the exhaust; they represent a significant pool of SOA precursors that are not included in traditional SOA models. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels. Models that do not account for this processing will likely underpredict the contribution of aircraft emissions to local and regional air pollution.

Miracolo, M. A.; Hennigan, C. J.; Ranjan, M.; Nguyen, N. T.; Gordon, T. D.; Lipsky, E. M.; Presto, A. A.; Donahue, N. M.; Robinson, A. L.

2011-05-01

207

Secondary aerosol formation from photochemical aging of aircraft exhaust in a smog chamber  

NASA Astrophysics Data System (ADS)

Field experiments were performed to investigate the effects of photo-oxidation on fine particle emissions from an in-use CFM56-2B gas turbine engine mounted on a KC-135 Stratotanker airframe. Emissions were sampled into a portable smog chamber from a rake inlet installed one-meter downstream of the engine exit plane of a parked and chocked aircraft. The chamber was then exposed to sunlight and/or UV lights to initiate photo-oxidation. Separate tests were performed at different engine loads (4, 7, 30, 85%). Photo-oxidation created substantial secondary particulate matter (PM), greatly exceeding the direct PM emissions at each engine load after an hour or less of aging at typical summertime conditions. After several hours of photo-oxidation, the ratio of secondary-to-primary PM mass was on average 35 ± 4.1, 17 ± 2.5, 60 ± 2.2, and 2.7 ± 1.1 times the primary PM for the 4, 7, 30, and 85% load experiments, respectively. The composition of secondary PM formed strongly depended on load. At 4% load, secondary PM was dominated by secondary organic aerosol (SOA). At higher loads, the secondary PM was mainly secondary sulfate. Predictions of an SOA model are compared to the measured SOA formation. The SOA model predicts ∼40% of the SOA produced during the 4% load experiment and ∼60% for the 85% load experiment. Significant emissions of low-volatility compounds present in both the vapor- and particle-phase were measured in the exhaust and represent a significant pool of SOA precursors that appear to form SOA efficiently when oxidized. These results underscore the importance of accounting for atmospheric processing when assessing the influence of aircraft emissions on ambient PM levels.

Miracolo, M. A.; Hennigan, C. J.; Ranjan, M.; Nguyen, N. T.; Gordon, T. D.; Lipsky, E. M.; Presto, A. A.; Donahue, N. M.; Robinson, A. L.

2010-11-01

208

Characterization of the sources and processes of organic and inorganic aerosols in New York city with a high-resolution time-of-flight aerosol mass apectrometer  

NASA Astrophysics Data System (ADS)

Submicron aerosol particles (PM1) were measured in-situ using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer during the summer 2009 Field Intensive Study at Queens College in New York, NY. Organic aerosol (OA) and sulfate are the two dominant species, accounting for 54% and 24%, respectively, of the total PM1 mass. The average mass-based size distribution of OA presents a small mode peaking at ~150 nm (Dva) and an accumulation mode (~550 nm) that is internally mixed with sulfate, nitrate, and ammonium. The diurnal cycles of both sulfate and OA peak between 01:00-02:00 p.m. EST due to photochemical production. The average (±?) oxygen-to-carbon (O/C), hydrogen-to-carbon (H/C), and nitrogen-to-carbon (N/C) ratios of OA in NYC are 0.36 (±0.09), 1.49 (±0.08), and 0.012 (±0.005), respectively, corresponding to an average organic mass-to-carbon (OM/OC) ratio of 1.62 (±0.11). Positive matrix factorization (PMF) of the high resolution mass spectra identified two primary OA (POA) sources, traffic and cooking, and three secondary OA (SOA) components including a highly oxidized, regional low-volatility oxygenated OA (LV-OOA; O/C = 0.63), a less oxidized, semi-volatile SV-OOA (O/C = 0.38) and a unique nitrogen-enriched OA (NOA; N/C = 0.053) characterized with prominent CxH2x + 2N+ peaks likely from amino compounds. Our results indicate that cooking and traffic are two distinct and mass-equivalent POA sources in NYC, together contributing ~30% of the total OA mass during this study. The OA composition is dominated by secondary species, especially during high PM events. SV-OOA and LV-OOA on average account for 34% and 30%, respectively, of the total OA mass. The chemical evolution of SOA in NYC appears to progress with a continuous oxidation from SV-OOA to LV-OOA, which is further supported by a gradual increase of O/C ratio and a simultaneous decrease of H/C ratio in total OOA. Detailed analysis of NOA (5.8% of OA) presents evidence that organic nitrogen species such as amines might have played an important role in the atmospheric processing of OA in NYC, likely involving both acid-base chemistry and photochemistry. In addition, analysis of air mass trajectories and satellite imagery of aerosol optical depth (AOD) indicates that the high potential source regions of secondary sulfate and aged OA are mainly located in regions to the west and southwest of the city.

Sun, Y.-L.; Zhang, Q.; Schwab, J. J.; Demerjian, K. L.; Chen, W.-N.; Bae, M.-S.; Hung, H.-M.; Hogrefe, O.; Frank, B.; Rattigan, O. V.; Lin, Y.-C.

2011-02-01

209

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

210

Secondary aspiration of aerosol particles into thin-walled nozzles facing the wind  

NASA Astrophysics Data System (ADS)

Problems of sampling aerosols from the turbulent atmosphere have been studied experimentally. The research was carried out with such particle sizes, type of samplers and sampling conditions that relate to those encountered in practical occupational hygiene and environmental monitoring. Distortion of the aerosol initial concentration was measured in a wind tunnel by a comparison method. Such distortions were caused by the external aspiration from a turbulent down flow using a vertical thin-walled cylindrical sampler. In addition, inertial errors themselves were determined by the limiting trajectory method. The difference between the results obtained with the help of the above methods showed the presence of secondary aspiration after the particles rebound from the outer nozzle surface for anisokinetical sampling. This fact was established by means of a set of special experiments with nozzles of various properties of the outer surface. Values of the rebound coefficient for Lycopodium particles aspirated into copper samplers over a range of diameters of 0.5-1 cm and anisokinetical coefficients (velocity ratio) of 1-40 were obtained. The conditions under which the efficiency of secondary aspiration is small were also defined.

Lipatov, G. N.; Grinshpun, S. A.; Semenyuk, T. I.; Sutugin, A. G.

211

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

NASA Astrophysics Data System (ADS)

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

Sarrafzadeh, M.; Hastie, D. R.

2013-12-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

213

Evaluation of the atmospheric significance of multiphase reactions in atmospheric secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

In a simple conceptual cloud-aerosol model the mass of secondary organic aerosol (SOA) that may be formed in multiphase reaction in an idealized scenario involving two cloud cycles separated with a cloud-free period is evaluated. The conditions are set to those typical of continental clouds, and each parameter used in the model calculations is selected as a mean of available observational data of individual species for which the multiphase SOA formation route has been established. In the idealized setting gas and aqueous-phase reactions are both considered, but only the latter is expected to yield products of sufficiently low volatility to be retained by aerosol particles after the cloud dissipates. The key variable of the model is the Henry-constant which primarily determines how important multiphase reactions are relative to gas-phase photooxidation processes. The precursor considered in the model is assumed to already have some affinity to water, i.e. it is a compound having oxygen-containing functional group(s). As a principal model output an aerosol yield parameter is calculated for the multiphase SOA formation route as a function of the Henry-constant, and has been found to be significant already above H~103 M atm-1. Among the potential precursors that may be eligible for this mechanism based on their Henry constants, there are a suite of oxygenated compounds such as primary oxidation products of biogenic and anthropogenic hydrocarbons, including, for example, pinonaldehyde. Finally, the analogy of multiphase SOA formation to in-cloud sulfate production is exploited.

Gelencsér, A.; Varga, Z.

2005-07-01

214

Evaluation of the atmospheric significance of multiphase reactions in atmospheric secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

In a simple conceptual cloud-aerosol model the mass of secondary organic aerosol (SOA) that may be formed in multiphase reaction in an idealized scenario involving two cloud cycles separated with a cloud-free period is evaluated. The conditions are set to those typical of continental clouds, and each parameter used in the model calculations is selected as a mean of available observational data of individual species for which the multiphase SOA formation route has been established. In the idealized setting gas and aqueous-phase reactions are both considered, but only the latter is expected to yield products of sufficiently low volatility to be retained by aerosol particles after the cloud dissipates. The key variable of the model is the Henry-constant which primarily determines how important multiphase reactions are relative to gas-phase photooxidation processes. The precursor considered in the model is assumed to already have some affinity to water, i.e. it is a compound having oxygen-containing functional group(s). As a principal model output an aerosol yield parameter is calculated for the multiphase SOA formation route as a function of the Henry-constant, and has been found to be significant already above H~103 M atm-1. Among the potential precursors that may be eligible for this mechanism based on their Henry constants, there are a suite of oxygenated compounds such as primary oxidation products of biogenic and anthropogenic hydrocarbons, including, for example, pinonaldehyde. Finally, the analogy of multiphase SOA formation to in-cloud sulfate production is exploited.

Gelencsér; Varga

2005-10-01

215

Secondary Organic Aerosol Formation in Clouds: A Synthesis of Data From Four Field Campaigns  

NASA Astrophysics Data System (ADS)

There is growing evidence, based on laboratory and ambient measurements, that secondary organic aerosol (SOA) is formed by aqueous-phase reactions in cloud droplets. Owing to the low volatility and water-soluble nature of organic acids, these species constitute a significant fraction of SOA mass. Airborne particle-into-liquid sampler (PILS-coupled to ion chromatography) measurements made on the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter are presented from four separate field campaigns representing urban and marine atmospheres: International Consortium for Atmospheric Research on Transport and Transformation (ICARTT 2004), Marine Stratus/Stratocumulus Experiment I and II (MASE 2005, 2007), Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS 2006). Sulfate and oxalate are strongly correlated in ambient aerosols, especially evaporated cloud droplet residual particles. Since their chemical formation mechanisms are not directly linked, this correlation can be explained by a common medium necessary for production: droplets. Enhanced organic acid aerosol layers have been observed directly above cloudtops in both marine and urban atmospheres; as derived from large eddy simulations of stratocumulus under the conditions of MASE, both Lagrangian trajectory analysis and diurnal cloudtop evolution provide evidence that a significant fraction of the aerosol mass concentration above cloud can be accounted for by evaporated droplet residual particles. Predictions from a chemical cloud parcel model considering the aqueous-phase production of organic acids and sulfate show good agreement with ambient data for the relative magnitude of sulfate and organic acid growth in clouds and also the evolution of oxalic acid and its aqueous-phase precursors with increasing altitude in cloud.

Sorooshian, A.; Brechtel, F. J.; Lu, M.; Feingold, G.; Ervens, B.; Jonsson, H.; Flagan, R. C.; Seinfeld, J. H.

2007-12-01

216

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

PubMed

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

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

2012-08-21

217

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

218

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

PubMed

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

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

2014-01-28

219

Carbonaceous aerosols in China: top-down constraints on primary sources and estimation of secondary contribution  

NASA Astrophysics Data System (ADS)

We simulated elemental carbon (EC) and organic carbon (OC) aerosols in China and compared model results to surface measurements at Chinese rural and background sites, with the goal of deriving "top-down" emission estimates of EC and OC, as well as better quantifying the secondary sources of OC. We included in the model state-of-the-science Chinese "bottom-up" emission inventories for EC (1.92 TgC yr-1) and OC (3.95 TgC yr-1), as well as updated secondary OC formation pathways. The average simulated annual mean EC concentration at rural and background sites was 1.1 ?gC m-3, 56% lower than the observed 2.5 ?gC m-3. The average simulated annual mean OC concentration at rural and background sites was 3.4 ?gC m-3, 76% lower than the observed 14 ?gC m-3. Multiple regression to fit surface monthly mean EC observations at rural and background sites yielded the best estimate of Chinese EC source of 3.05 ± 0.78 TgC yr-1. Based on the top-down EC emission estimate and observed seasonal primary OC/EC ratios, we estimated Chinese OC emissions to be 6.67 ± 1.30 TgC yr-1. Using these top-down estimates, the simulated average annual mean EC concentration at rural and background sites was significantly improved to 1.9 ?gC m-3. However, the model still significantly underestimated observed OC in all seasons (simulated average annual mean OC at rural and background sites was 5.4 ?gC m-3), with little skill in capturing the spatiotemporal variability. Secondary formation accounts for 21% of Chinese annual mean surface OC in the model, with isoprene being the most important precursor. In summer, as high as 62% of the observed surface OC may be due to secondary formation in eastern China. Our analysis points to four shortcomings in the current bottom-up inventories of Chinese carbonaceous aerosols: (1) the anthropogenic source is underestimated on a national scale, particularly for OC; (2) the spatiotemporal distributions of emissions are misrepresented; (3) there is a missing source in western China, likely associated with the use of biofuels or other low-quality fuels for heating; and (4) sources in fall are not well represented, either because the seasonal shifting of emissions and/or secondary formation are poorly captured or because specific fall emission events are missing. In addition, secondary production of OC in China is severely underestimated. More regional measurements with better spatiotemporal coverage are needed to resolve these shortcomings.

Fu, T.-M.; Cao, J. J.; Zhang, X. Y.; Lee, S. C.; Zhang, Q.; Han, Y. M.; Qu, W. J.; Han, Z.; Zhang, R.; Wang, Y. X.; Chen, D.; Henze, D. K.

2012-03-01

220

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

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation from oxidation products of biogenic volatile organic compounds (BVOC) constitutes an important coupling between vegetation, atmospheric chemistry, and climate change. Such secondary organic aerosol components play an important role in particle formation in Boreal regions ((Laaksonen et al., 2008)), where biogenic secondary organic aerosols contribute to an overall negative radiative forcing, thus a negative feed back between vegetation and climate warming (Spracklen et al., 2008). Within the EUCAARI project we investigated SOA formation from mixtures of monoterpenes (and sesquiterpenes) as emitted typically from Boreal tree species in Southern Finland. The experiments were performed in the large photochemical reactor SAPHIR in Juelich at natural light and oxidant levels. Oxidation of the BVOC mixtures and SOA formation was induced by OH radicals and O3. The SOA was formed on the first day and then aged for another day. The resulting SOA was characterized by HR-ToF-AMS, APCI-MS, and filter samples with subsequent H-NMR, GC-MS and HPLC-MS analysis. The chemical evolution of the SOA is characterized by a fast increase of the O/C ratio during the formation process on the first day, stable O/C ratio during night, and a distinctive increase of O/C ratio at the second day. The increase of the O/C ratio on the second day is highly correlated to the OH dose and is accompanied by condensational growth of the particles. We will present simultaneous factor analysis of AMS times series (PMF, Ulbrich et al., 2009 ) and direct measurements of individual chemical species. We found that four factors were needed to represent the time evolution of the SOA composition (in the mass spectra) if oxidation by OH plays a mayor role. Corresponding to these factors we observed individual, representative molecules with very similar time behaviour. The correlation between tracers and AMS factors is astonishingly good as the molecular tracers represented only a very small mass fraction of the factors. There is indication that some factors grow at the cost of the other suggesting a set of successive generations of oxidation products. This conversion could proceed either by direct condensed phase processes or by an evaporation-oxidation-recondensation mechanism. On the other hand it seems that the factors evolve in parallel, representing products of multiple oxidation which appear on different time scales in the particulate phase. These findings will be discussed with respect to their importance for ageing processes of atmospheric organic aerosols. References Laaksonen, A., Kulmala, M., O'Dowd, C. D., Joutsensaari, J., Vaattovaara, P., Mikkonen, S., Lehtinen, K. E. J., Sogacheva, L., Dal Maso, M., Aalto, P., Petaja, T., Sogachev, A., Yoon, Y. J., Lihavainen, H., Nilsson, D., Facchini, M. C., Cavalli, F., Fuzzi, S., Hoffmann, T., Arnold, F., Hanke, M., Sellegri, K., Umann, B., Junkermann, W., Coe, H., Allan, J. D., Alfarra, M. R., Worsnop, D. R., Riekkola, M. L., Hyotylainen, T., and Viisanen, Y.: The role of VOC oxidation products in continental new particle formation, Atmospheric Chemistry and Physics, 8, 2657-2665, 2008 Spracklen, D. V., Bonn, B., and Carslaw, K. S.: Boreal forests, aerosols and the impacts on clouds and climate, Philosophical Transactions of the Royal Society a-Mathematical Physical and Engineering Sciences, 366, 4613-4626, 10.1098/rsta.2008.0201, 2008 Ulbrich, I. M., Canagaratna, M. R., Zhang, Q., Worsnop, D. R., and Jimenez, J. L.: Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data, Atmospheric Chemistry and Physics, 9, 2891-2918, 2009

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

2010-05-01

221

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

222

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

223

Characterization of the sources and processes of organic and inorganic aerosols in New York City with a high-resolution time-of-flight aerosol mass spectrometer  

NASA Astrophysics Data System (ADS)

Submicron aerosol particles (PM1) were measured in-situ using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) during the summer 2009 Field Intensive Study at Queens College in New York City. Organic aerosol (OA) and sulfate are the two dominant species, accounting for 54% and 24%, respectively, of total PM1 mass on average. The average mass size distribution of OA presents a small mode peaking at ~150 nm (Dva) in addition to an accumulation mode (~550 nm) that is internally mixed with sulfate, nitrate, and ammonium. The diurnal cycles of sulfate and OA both show pronounced peaks between 01:00-02:00 p.m. EST due to photochemical production. The average (±1?) oxygen-to-carbon (O/C), hydrogen-to-carbon (H/C), and nitrogen-to-carbon (N/C) ratios of OA in NYC are 0.36 (±0.09), 1.49 (±0.08), and 0.012(±0.005), respectively, corresponding to an average organic mass-to-carbon (OM/OC) ratio of 1.62(±0.11). Positive matrix factorization (PMF) of the high resolution mass spectra identified five OA components: a hydrocarbon-like OA (HOA), two types of oxygenated OA (OOA) including a low-volatility OOA (LV-OOA) and a semi-volatile OOA (SV-OOA), a cooking-emission related OA (COA), and a unique nitrogen-enriched OA (NOA). HOA appears to represent primary OA (POA) from urban traffic emissions. It comprises primarily of reduced species (H/C=1.83; O/C=0.06) and shows a mass spectral pattern very similar to those of POA from fossil fuel combustion, and correlates tightly with traffic emission tracers including elemental carbon and NOx. LV-OOA, which is highly oxidized (O/C=0.63) and correlates well with sulfate, appears to be representative for regional, aged secondary OA (SOA). SV-OOA, which is less oxidized (O/C=0.38) and correlates well with non-refractory chloride, likely represents less photo-chemically aged, semi-volatile SOA. COA shows a similar spectral pattern to the reference spectra of POA from cooking emissions and a distinct diurnal pattern peaking around local lunch and dinner times. In addition, NOA is characterized with prominent CxH2x+2N+ peaks likely from amine compounds. Our results indicate that cooking-related activities are a major source of POA in NYC, releasing comparable amounts of POA as traffic emissions. POA=HOA+COA) on average accounts for ~30% of the total OA mass during this study while SOA dominates the OA composition with SV-OOA and LV-OOA on average accounting for 34% and 30%, respectively, of the total OA mass. The chemical evolution of SOA in NYC involves a~continuous oxidation from SV-OOA to LV-OOA, which is further supported by a gradual increase of O/C ratio and a simultaneous decrease of H/C ratio in total OOA. Detailed analysis of NOA (5.8% of OA) presents evidence that nitrogen-containing organic species such as amines might have played an important role in the atmospheric processing of OA in NYC, likely involving acid-base chemistry. Analysis of air mass trajectories and satellite imagery of aerosol optical depth (AOD) indicates that the high potential source regions of secondary sulfate and aged OA are mainly located in regions to the west and southwest of the city.

Sun, Y.-L.; Zhang, Q.; Schwab, J. J.; Demerjian, K. L.; Chen, W.-N.; Bae, M.-S.; Hung, H.-M.; Hogrefe, O.; Frank, B.; Rattigan, O. V.; Lin, Y.-C.

2010-10-01

224

Secondary Organic Aerosol Formation From the Heterogeneous Chemistry of Isoprene-Derived Epoxides: Implications for Air Quality, Climate and Public Health  

E-print Network

Secondary Organic Aerosol Formation From the Heterogeneous Chemistry of Isoprene- Derived Epoxides, the largest mass fraction of PM2.5 is organic, and is mostly dominated by secondary organic aerosol (SOA underestimate observations. By combining organic synthesis, computational calculations, mass spectrometry, smog

Lin, Qiao

225

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

226

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

227

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

228

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 Tgyr-1), recent studies have shown that an additional source of SOA around 100 Tgyr-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 10nm 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 > 40nm (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 TgSOAyr-1 compared to the base simulation solely with biogenic SOA emissions (19 Tgyr-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.; Hakkinen, S.; Westervelt, D. M.; Kuang, C.; Levin, E. J.; Leaitch, W. R.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

2013-12-01

229

Understanding 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 (BL). 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 Tg yr-1 correlated with anthropogenic carbon monoxide (CO) emissions may be required to match measurements. (2) Many models treat SOA solely as semi-volatile, 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-corrected 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-corrected 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 number concentration 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.; Kanawade, V. P.; Leaitch, W. R.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

2013-11-01

230

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

PubMed

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

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

2013-01-01

231

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

NASA Astrophysics Data System (ADS)

Hydroxyl radical (OH) oxidation and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. The pure OH oxidation of monoterpenes, an important biogenic VOC class, has seldom been investigated. In order to elucidate the importance of the reaction pathyways of the OH oxidation and ozonolysis and their roles in particle formation and growth, we investigated the particle formation of several common monoterpenes (alpha-pinene, beta-pinene, and limonene) in the large atmosphere simulation chamber SAPHIR in Juelich, Germany. The experiments were conducted for both OH dominant and pure ozonolysis case (in the presence of CO as OH scavenger) at ambient relevant conditions (low OA, low VOC and low NOx concentration). OH and ozone (O3) concentrations were measured so that the oxidation rates of OH and O3 with precursors were quantified. The particle formation and growth, aerosol yield, multi-generation reaction process and aerosol composition were analyzed. Pure ozonolysis generated a large amount of particles indicating ozonolysis plays an important role in particle formation as well as OH oxidation. In individual experiments, particle growth rates did not necessarily correlate with OH or O3 oxidation rates. However, comparing the growth rates at similar OH or O3 oxidation rates shows that generally, OH oxidation and ozonolysis have similar efficiency in particle growth. Multi-generation products are shown to be important in the OH oxidation experiment based on aerosol yield "growth curve" (Ng et al., 2006). The reaction process of OH oxidation experiments was analyzed as a function of OH dose to elucidate the role of functionalization and fragmentation. A novel analysis was developed to link the particle formation with the reaction with OH, which was also used to examine the role of functionalization and fragmentation in the particle formation by OH oxidation. These analyses show that functionalization was dominant in the beginning of the reaction and fragmentation started to be dominant after that. Moreover, Aerosol Mass Spectrometer data shows that SOA from monoterpene OH oxidation follows a slope of shallower than -1 in the Van Krevelen diagram, indicative of an oxidation process of precursor without significant hydrogen loss. SOA from OH oxidation has a higher H/C than that from O3 oxidation. In ozonolysis, the process with significant hydrogen loss such as addition of carbonyl seems to play an important role in SOA formation. Reference: Ng, N. L. et al. Sci. & Tech. 40, 2283-2297, 10.1021/es052269u, 2006.

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

2014-05-01

232

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

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.

2012-10-01

233

Carbonaceous aerosols in China: top-down constraints on primary sources and estimation of secondary contribution  

NASA Astrophysics Data System (ADS)

We simulate elemental carbon (EC) and organic carbon (OC) aerosols in China and compare model results to surface measurements at Chinese rural and background sites, with the goal of deriving "top-down" emission estimates of EC and OC, as well as better quantifying the secondary sources of OC. We include in the model state-of-the-science Chinese "bottom-up" emission inventories for EC (1.92 Tg C yr-1) and OC (3.95 Tg C yr-1), as well as updated secondary OC formation pathways. The average simulated annual mean EC concentration at rural and background site is 1.1 ?g C m-3, 56% lower than the observed 2.5 ?g C m-3. The average simulated annual mean OC concentration at rural and background sites is 3.4 ?g C m-3, 76% lower than the observed 14 ?g C m-3. Multiple regression to fit surface monthly mean EC observations at rural and background sites yields best estimate of Chinese EC source of 3.05 ± 0.78 Tg C yr-1. Based on the top-down EC emission estimate and observed seasonal primary OC/EC ratios, we estimate Chinese OC total emissions to be 6.67 ± 1.30 Tg C yr-1. Using these top-down estimates, the simulated average annual mean EC concentration at rural and background sites significantly improved to 1.9 ?g C m-3. However, the model still significantly underestimates observed OC in all seasons (simulated average annual mean OC at rural and background sites is 5.4 ?g C m-3), with little skill in capturing the spatiotemporal variability. Secondary formation accounts for 21% of Chinese annual mean surface OC in the model, with isoprene being the most important precursor. In summer, as high as 62% of the observed surface OC may be due to secondary formation in eastern China. Our analysis points to three shortcomings in the current bottom-up inventories of Chinese carbonaceous aerosols: (1) the anthropogenic source is severely underestimated, particularly for OC; (2) there is a missing source in western China, likely associated with the use of biofuels or other low-quality fuels for heating; and (3) sources in fall are not well represented, either because the seasonal shifting of emissions and/or secondary formation are poorly captured or because specific fall emission events are missing. More regional measurements with better spatiotemporal coverage are needed to resolve these shortcomings.

Fu, T.-M.; Cao, J. J.; Zhang, X. Y.; Lee, S. C.; Zhang, Q.; Han, Y. M.; Qu, W. J.; Han, Z.; Zhang, R.; Wang, Y. X.; Chen, D.; Henze, D. K.

2011-10-01

234

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

235

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

236

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

237

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

238

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

239

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

PubMed Central

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

2012-01-01

240

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

PubMed

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

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

2012-09-01

241

DROPLET PHASE (HETEROGENEOUS) AND GAS PHASE (HOMOGENEOUS) CONTRIBUTIONS TO SECONDARY AMBIENT AEROSOL FORMATION AS FUNCTIONS OF RELATIVE HUMIDITY  

EPA Science Inventory

In previous publications (McMurry and Wilson, 1982; McMurry et al., 1981), techniques for determining the relative contributions of gas phase and liquid phase reactions to secondary ambient aerosol formation have been described. In this paper these methods are applied to more rec...

242

Appearance of strong absorbers and fluorophores in limonene-O3 secondary organic aerosol due to NH4  

E-print Network

Appearance of strong absorbers and fluorophores in limonene-O3 secondary organic aerosol due to NH4 and also of aqueous extracts of SOA. The addition of ammonium ions or amino acids to limonene SOA of aged limonene + NH4 + SOA were characterized by an effective base-e absorption coefficient of $3 L gÃ?1

Nizkorodov, Sergey

243

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...

244

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

E-print Network

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

Meskhidze, Nicholas

245

Secondary organic aerosol yields from cloud-processing of isoprene oxidation products  

NASA Astrophysics Data System (ADS)

While there is a growing understanding from laboratory studies of aqueous phase chemical processes that lead to secondary organic aerosol (SOA) formation in cloud droplets (SOA drop ), the contribution of aqueous phase chemistry to atmospheric SOA burden is yet unknown. Using a parcel model including a multiphase chemical mechanism, we show that SOA drop carbon yields (Y c ) from isoprene (1) depend strongly on the initial volatile organic carbon (VOC)/NOx ratio resulting in 42% > Y c > 0.4% over the atmospherically-relevant range of 0.25 < VOC/NOx < 100; (2) increase with increasing cloud-contact time; (3) are less affected by cloud liquid water content, pH, and droplet number. (4) The uncertainty associated with gas/particle-partitioning of semivolatile organics introduces a relative error of -50% <= ?Y c < +100 %. The reported yields can be applied to air quality and climate models as is done with SOA formed on/in concentrated aerosol particles (SOA aer ).

Ervens, Barbara; Carlton, Annmarie G.; Turpin, Barbara J.; Altieri, Katye E.; Kreidenweis, Sonia M.; Feingold, Graham

2008-01-01

246

Ethylene glycol emissions from on-road vehicles: implications for aqueous phase secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

Ethylene glycol (HOCH2CH2OH), used as an engine coolant for most on-road vehicles, is an intermediate volatility organic compound (IVOC) with a high Henry's Law Coefficient (kH > 10,000 M atm-1) . Oxidation of ethylene glycol, especially in the atmospheric aqueous phase (clouds, fog, wet aerosol), can lead to the formation of glycolaldehyde, oxalic acid, and ultimately secondary organic aerosol. We present measurements of unexpectedly high ethylene glycol emissions in the Caldecott Tunnel near San Francisco (Summer 2010) and the Washburn Tunnel near Houston (Spring 2009). Ethylene glycol was detected using a proton-transfer reaction mass spectrometer (PTR-MS) at m/z = 45, which is usually interpreted as acetaldehyde. Although not necessarily a tailpipe emission, effective fuel-based emission factors are calculated using the carbon balance method and range from 50 to 400 mg ethylene glycol per kg fuel. Total US and global emissions are estimated using these emission factors and fuel consumption rates and are compared to previous model estimates of ethylene glycol emissions (e.g., the Regional Atmospheric Chemistry Model). Compared to biogenically emitted isoprene, ethylene glycol is likely a minor source of glycolaldehyde globally, but may contribute significantly to glycolaldehyde, oxalate and SOA formation in areas dominated by urban emissions.

Wood, E. C.; Knighton, W. B.; Fortner, E.; Herndon, S. C.; Onasch, T. B.; Franklin, J.; Harley, R. A.; Gentner, D. R.; Goldstein, A. H.

2012-12-01

247

Formation and chemical aging of secondary organic aerosol during the ?-caryophyllene oxidation  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) production during the oxidation of ?-caryophyllene by ozone (O3) and hydroxyl radicals (OH) and the subsequent chemical aging of the products during reactions with OH were investigated. Experiments were conducted with ozone, hydroxyl radicals at low NOx (zero added NOx) and at high NOx (100s of ppb). The SOA mass yield at 10 ?g m-3 of organic aerosol is 26% for the ozonolysis, 20% for the reaction with OH at low NOx and 38% at high NOx. Parameterizations of the fresh SOA yields have been developed. The average fresh SOA atomic O : C ratio varied from 0.24 to 0.33 depending on the oxidant and the NOx level. The chemical aging of the produced ?-caryophyllene SOA was studied by exposing the fresh SOA to high concentrations (107 molecules cm-3) of hydroxyl radicals for several hours. These additional reactions increased the SOA concentration by 15-40% and the O : C by approximately 25%. It was found that the exposure to UV-light has no effect on the ?-caryophyllene SOA. Experiments suggested that there was a significant impact of the relative humidity in the chemical aging of the SOA. We quantified the evaporation rates of ?-caryophyllene SOA by using a thermodenuder. The corresponding volatility distributions and the effective vaporization enthalpies were estimated. An average density of 1.06 ± 0.1 g cm-3 of the ?-caryophyllene SOA was estimated.

Tasoglou, A.; Pandis, S. N.

2014-11-01

248

Changes in Secondary Organic Aerosol Composition and Mass due to Photolysis: Relative Humidity Dependence.  

PubMed

This study is focused on the relative humidity (RH) dependence of water-soluble secondary organic aerosol (SOA) aging by photolysis. Particles containing ?-pinene SOA and ammonium sulfate, generated by atomization, were exposed to UV radiation in an environmental chamber at three RH conditions (5, 45, and 85%), and changes in chemical composition and mass were monitored using an aerosol mass spectrometer (AMS). Under all RH conditions, photolysis leads to substantial loss of SOA mass, where the rate of mass loss decreased with decreasing RH. For all RH conditions, the less oxidized components of SOA (e.g., carbonyls) exhibited the fastest photodegradation rates, which resulted in a more oxidized SOA after photolytic aging. The photolytic reactivity of SOA material exhibited a dependence on RH likely due to moisture-induced changes in SOA morphology or phase. The results suggest that the atmospheric lifetime of SOA with respect to photolysis is dependent on its RH cycle, and that photolysis may be an important sink for some SOA components occurring on an initial time scale of a few hours under ambient conditions. PMID:25196234

Wong, Jenny P S; Zhou, Shouming; Abbatt, Jonathan P D

2014-09-23

249

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

250

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

SciTech Connect

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

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

2013-05-10

251

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

PubMed

Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines, and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of water-soluble SOA generated from two monoterpenes, limonene and ?-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ?100 ppb ammonia in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (?0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for ?excitation = 420 ± 50 nm and ?emission = 475 ± 38 nm. The window of the strongest fluorescence shifted to ?excitation = 320 ± 25 nm and ?emission = 425 ± 38 nm for the ?-pinene-derived SOA. Both regions overlap with the EEM spectra of some of the fluorophores found in primary biological aerosols. Despite the low quantum yield, the aged SOA particles may have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols. PMID:23663151

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

2013-06-01

252

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

PubMed

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

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

2015-01-01

253

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

PubMed Central

Airborne particles are important for public health, visibility, and climate. Predicting their concentrations, effects, and responses to control strategies requires accurate models of their formation and growth in air. This is challenging, as a large fraction is formed by complex reactions of volatile organic compounds, generating secondary organic aerosol (SOA), which grows to sizes important for visibility, climate, and deposition in the lung. Growth of SOA is particularly sensitive to the phase/viscosity of the particles and remains poorly understood. We report studies using a custom-designed impactor with a germanium crystal as the impaction surface to study SOA formed from the ozonolysis of ?-pinene at relative humidities (RHs) up to 87% at 297 ± 2 K (which corresponds to a maximum RH of 70–86% inside the impactor). The impaction patterns provide insight into changes in phase/viscosity as a function of RH. Attenuated total reflectance-Fourier transform infrared spectroscopy and aerosol mass spectrometry provide simultaneous information on composition changes with RH. The results show that as the RH at which the SOA is formed increases, there is a decrease in viscosity, accompanied by an increasing contribution from carboxylic acids and a decreasing contribution from higher molecular mass products. In contrast, SOA that is formed dry and subsequently humidified remains solid to high RH. The results of these studies have significant implications for modeling the growth, aging, and ultimately, lifetime of SOA in the atmosphere. PMID:24821796

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

2014-01-01

254

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

255

Secondary organic aerosol from limona ketone: insights into terpene ozonolysis via synthesis of key intermediates.  

PubMed

Limona ketone was synthesized to explore the secondary organic aerosol (SOA) formation mechanism from limonene ozonolysis and also to test group-additivity concepts describing the volatility distribution of ozonolysis products from similar precursors. Limona ketone SOA production is indistinguishable from alpha-pinene, confirming the expected similarity. However, limona ketone SOA production is significantly less intense than limonene SOA production. The very low vapor pressure of limonene ozonolysis products is consistent with full oxidation of both double bonds in limonene and furthermore with production of products other than ketones after oxidation of the exo double bond in limonene. Mass-balance constraints confirm that ketone products from exo double-bond ozonolysis have a minimal contribution to the ultimate product yield. These results serve as the foundation for an emerging framework to describe the effect on volatility of successive generations of organic compounds in the atmosphere. PMID:17551623

Donahue, Neil M; Tischuk, Joshua E; Marquis, Bryce J; Huff Hartz, Kara E

2007-06-21

256

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

257

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

SciTech Connect

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

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

2000-03-15

258

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

NASA Astrophysics Data System (ADS)

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

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

2004-02-01

259

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

SciTech Connect

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

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

2013-10-26

260

Changes in Secondary Organic Aerosol burden from 1960-2010: a model study with the climate-aerosols ECHAM6-HAM2 model  

NASA Astrophysics Data System (ADS)

Organic aerosols (OA) represent an important fraction of the total aerosol burden and include Primary Organic Aerosols (POA), which are directly emitted into the atmosphere and Secondary Organic Aerosols (SOA), which result from atmospheric oxidation of a number of gaseous precursors. Recent estimates indicate that SOA represent about 50% of the total OA burden (but only about 30 % of the OA surface concentration). In this study we explore the processes driving the changes in the production and burden of SOA from 1960 to 2010 with the global climate-aerosol model ECHAM6-HAM2. Between the 60s and 00s the global SOA production increases from 24 to 30 Tg/a, the burden increases from 0.56 Tg to 0.64 Tg. The increase takes mainly place in the main source regions of the Northern Hemisphere (tropical forested regions and highly polluted regions in Asia) and in South America. With a series of sensitivity simulations we distinguish between the roles of climate change (temperature, precipitation, radiation), land use change, changes in emissions of POA, and changes in emissions of anthropogenic precursors of SOA. We find that, while all regions show an increase in burden, the relative importance of each process is strongly region-dependent. In Europe, the increase in SOA is related to climate and land use changes. In Africa, the increase in SOA results from climate change and increase in POA emissions. In Asia, the increase is mainly due to increase in anthropogenic emissions.

Sousa Santos, Gabriela; Stanelle, Tanja; Bey, Isabelle

2014-05-01

261

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

NASA Astrophysics Data System (ADS)

One of the largest primary sources of organic aerosol in the atmosphere is biomass burning (BB) (Laskin et al. 2009); in Europe its contribution to annual mean of PM10 is between 3 and 14 % (Maenhaut et al. 2012). During the process of wood burning many different products are formed via thermal degradation of wood lignin. Hardwood burning produces mainly syringol (2,6-dimetoxyphenol) derivatives, while softwood burning exclusively guaiacol (2-methoxyphenol) and its derivatives. Taking into account physical properties of methoxyphenols only, their concentrations in atmospheric waters might be underestimated. So, their aqueous phase reactions can be an additional source of SOA, especially in regions under significant influence of wood combustion. An important class of compounds formed during physical and chemical aging of the primary BBA in the atmosphere is nitrocatechols, known as strong absorbers of UV and Vis light (Claeys et al. 2012). Very recently, methyl-nitrocatechols were proposed as suitable markers for highly oxidized secondary BBA (Iinuma et al. 2010, Kitanovski et al. 2012). In the present work, the formation of SOA through aqueous phase photooxidation and nitration of guaiacol was examined. The key objective was to chemically characterize the main low-volatility products and further to check their possible presence in the urban atmospheric aerosols. The aqueous phase reactions were performed in a thermostated reactor under simulated sunlight in the presence of H2O2 and nitrite. Guaiacol reaction products were first concentrated by solid-phase extraction (SPE) and then subjected to semi-preparative liquid chromatography.The main product compounds were fractionated and isolated as pure solids and their structure was further elucidated by using nuclear magnetic resonance spectroscopy (1H, 13C and 2D NMR) and direct infusion negative ion electro-spray ionization tandem mass spectrometry (( )ESI-MS/MS). The main photonitration products of guaiacol (4-nitroguaiacol, 6-nitroguaiacol and 4,6-dinitroguaiacol) were examined for their presence in winter aerosol samples by using an optimized HPLC-(-)ESI-MS/MS. 4-nitroguaiacol and 4,6-dinitroguaiacol were unambiguously identified in winter PM10 from Ljubljana, Slovenia, whereas the absence of 6-nitroguaiacol was further explained with the help of long-term reaction monitoring. To our knowledge, our study represents the first report on the identification of 4,6-dinitroguaiacol in ambient aerosols. Laskin, A. et al. (2009) Environ. Sci. Technol. 43, 3764-3771. Maenhaut, W. et al. (2012) Sci. Tot. Environ. 437, 226-236. Claeys, M. et al. (2012) Environ. Chem. 9, 273-284. Iinuma, Y. et al. (2010) Environ. Sci. Technol. 44, 8453-8459. Kitanovski, Z. et al. (2012)J. Chromatogr. A 1268, 35-43.

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

2014-05-01

262

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

NASA Astrophysics Data System (ADS)

Four different parameterizations for the formation and evolution of secondary organic aerosol (SOA) are evaluated using a 0-D box model representing the Los Angeles Metropolitan Region during the CalNex 2010 field campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model-measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model/measurement agreement for mass concentration. When comparing the three parameterizations, the Grieshop et al. (2009) parameterization more accurately reproduces both the SOA mass concentration and oxygen-to-carbon ratio inside the urban area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the observed SOA concentrations in Pasadena. All the parameterizations over-predict urban SOA formation at long photochemical ages (? 3 days) compared to observations from multiple sites, which can lead to problems in regional and global modeling. Among the explicitly modeled VOCs, the precursor compounds that contribute the greatest SOA mass are methylbenzenes. Polycyclic aromatic hydrocarbons (PAHs) are less important precursors and contribute less than 4% of the SOA mass. The amounts of SOA mass from diesel vehicles, gasoline vehicles, and cooking emissions are estimated to be 16-27, 35-61, and 19-35%, respectively, depending on the parameterization used, which is consistent with the observed fossil fraction of urban SOA, 71 (±3) %. In-basin biogenic VOCs are predicted to contribute only a few percent to SOA. A regional SOA background of approximately 2.1 ?g m-3 is also present due to the long distance transport of highly aged OA. The percentage of SOA from diesel vehicle emissions is the same, within the estimated uncertainty, as reported in previous work that analyzed the weekly cycles in OA concentrations (Bahreini et al., 2012; Hayes et al., 2013). However, the modeling work presented here suggests a strong anthropogenic source of modern carbon in SOA, due to cooking emissions, which was not accounted for in those previous studies. Lastly, this work adapts a simple two-parameter model to predict SOA concentration and O/C from urban emissions. This model successfully predicts SOA concentration, and the optimal parameter combination is very similar to that found for Mexico City. This approach provides a computationally inexpensive method for predicting urban SOA in global and climate models. We estimate pollution SOA to account for 26 Tg yr-1 of SOA globally, or 17% of global SOA, 1/3 of which is likely to be non-fossil.

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

2014-12-01

263

Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes  

NASA Astrophysics Data System (ADS)

Production mechanisms of aerosol chemical species, in terms of primary and secondary processes, were studied using vertical concentration gradient measurements at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WIOC) concentration profiles showed a net production at the surface (i.e. primary production), while nssSO4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. These observations indicate that WSOC was predominantly of secondary origin and that WIOC was predominantly of primary origin. Derived PM1 mass fluxes compared reasonably well with those previously obtained from an eddy covariance (EC) technique following a power law relationship with the wind speed (F PM1 = 0.000096*U 4.23). For cases with clear primary organic mass fluxes in the flux footprint WIOM mass fluxes ranged between 0.16 and 1.02 ng m-2 s-1 and WIOM/sea salt mass ratio was 0.34-3.6, in good agreement with previous measurements at Mace Head.

Ceburnis, Darius; O'Dowd, Colin D.; Jennings, Gerard S.; Facchini, Maria Cristina; Emblico, Lorenza; Decesari, Stefano; Fuzzi, Sandro; Sakalys, Jonas

2008-04-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

265

Laser desorption\\/ionization mass spectrometric study of secondary organic aerosol formed from the photooxidation of aromatics  

Microsoft Academic Search

Five aromatic hydrocarbons – benzene, toluene, ethylbenzene, p-xylene and 1,2,4-trimethylbenzene – were selected to investigate the laser desorption\\/ionization mass spectra of secondary\\u000a organic aerosols (SOA) resulting from OH-initiated photooxidation of aromatic compounds. The experiments were conducted by\\u000a irradiating aromatic hydrocarbon\\/CH3ONO\\/NO\\u000a X\\u000a mixtures in a home-made smog chamber. The aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure the aerodynamic\\u000a size

Mingqiang Huang; Weijun Zhang; Liqing Hao; Zhenya Wang; Wenwu Zhao; Xuejun Gu; Xiaoyong Guo; Xianyun Liu; Bo Long; Li Fang

2007-01-01

266

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

267

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

268

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

269

Formation of Anthropogenic and Biogenic Secondary Organic Aerosol at Bakersfield, CA  

NASA Astrophysics Data System (ADS)

The source and chemistry of secondary organic aerosol (SOA) are major challenges remaining unresolved in the atmospheric science. To address this uncertainty, measurements were conducted at the Bakersfield (California, US) supersite during the CALNEX campaign in May and June of 2010. The submicron organic mass (OM), a major component of PM1 (65%), accounted for 70% of the OM in PM2.5. A majority of this submicron OM (80-90%) was composed of SOA, which is a mixture of components formed from anthropogenic and biogenic origins. These SOA components were distinguished and consistently identified from the factor analysis applied on the independent Fourier Transform Infrared Spectroscopy and High Resolution Time-of-Flight Aerosol Mass Spectrometry measurements. The SOA formed from motor vehicular emissions dominated the OM (65%). This SOA was likely composed of oxidation products from alkane (alkane SOA; 41% of the OM) and PAH (PAH SOA; 24% of the OM) compound classes. The alkane SOA tightly tracked the ozone mixing ratios, suggesting that this component was likely formed via the ozone-driven oxidation processes. The PAH SOA was likely formed by OH radical oxidation, consistent with the good correlation of the PAH SOA to sulfate, which is a surrogate for gas-phase OH oxidation under dry conditions. The petroleum operation SOA, a nearly missing component in the source inventory of PM2.5 in San Joaquin Valley, accounted for 14% of the OM. While the anthropogenic SOA components were formed during the daytime, the biogenic SOA (10-13% of the OM) was likely the product of NO3 radical oxidation of biogenic volatile organic compounds, which transported from the nearby mountain regions to the sampling site at night. The mass concentration of the SOA components could help improve the source inventory estimation of San Joaquin Valley, and the formation pathways of distinct SOA components were suggested in this work.

Liu, S.; Russell, L. M.; Day, D. A.; Zhao, Y.; Goldstein, A. H.; Weber, R.

2011-12-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

271

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

NASA Astrophysics Data System (ADS)

In this work, we conducted aqueous photooxidation experiments with ambient samples in order to develop insights concerning the formation of secondary organic aerosol through gas followed by aqueous chemistry (SOAaq). Water-soluble organics (e.g., glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone) are formed through gas phase oxidation of alkene and aromatic emissions of anthropogenic and biogenic origin. Their further oxidation in clouds, fogs and wet aerosols can form lower volatility products (e.g., oligomers, organic acids) that remain in the particle phase after water evaporation, thus producing SOA. The aqueous OH radical oxidation of several individual potentially important precursors has been studied in the laboratory. In this work, we used a mist-chamber apparatus to collect atmospheric mixtures of water-soluble gases from the ambient air at San Pietro Capofiume, Italy during the PEGASOS field campaign. We measured the concentration dynamics after addition of OH radicals, in order to develop new insights regarding formation of SOA through aqueous chemistry. Specifically, batch aqueous reactions were conducted with 33 ml mist-chamber samples (TOC ~ 50-100?M) and OH radicals (~10-12M) in a new low-volume aqueous reaction vessel. OH radicals were formed in-situ, continuously by H2O2 photolysis. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS +/-), and ESI-MS with IC pre-separation (IC/ESI-MS-). Reproducible formation of pyruvate and oxalate were observed both by IC and ESI-MS. These compounds are known to form from aldehyde oxidation in the aqueous phase. New insights regarding the aqueous chemistry of these "more atmospherically-realistic" experiments will be discussed.

Kirkland, J. R.; Lim, Y. B.; Sullivan, A. P.; Decesari, S.; Facchini, C.; Collett, J. L.; Keutsch, F. N.; Turpin, B. J.

2012-12-01

272

Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas-Chromatography  

NASA Astrophysics Data System (ADS)

The oxidation of volatile organic compounds (VOCs) plays a role in both regional and global air quality. However, field and laboratory research indicate that the body of knowledge around the identities, quantities and oxidation processes of these compounds in the ambient atmosphere is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). VOCs emitted to the atmosphere largely are of biogenic origin (Guenther et al., 2006), and many studies of ambient secondary organic aerosol (SOA) suggest that SOA is largely of biogenic origin (albeit closely connected to anthropogenic activities, e.g., de Gouw and Jimenez, 2009). Accurate modeling of SOA levels and properties will require a more complete understanding of biogenic VOCs (BOCs) and their atmospheric oxidation products. For example, satellite measurements indicate that biogenic VOC emissions are two to three times greater than levels currently included in models (Heald et al., 2010). Two-dimensional gas chromatography (GC×GC) is a powerful analytical technique that shows much promise in advancing the state-of-knowledge regarding BVOCs and their role in SOA formation. In this work, samples were collected during BEACHON-RoMBAS (Bio-hydro-atmosphere Interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study) in July and August of 2011. The field site was a Ponderosa Pine forest near Woodland, CO, inside the Manitou Experimental Forest, which is operated by the US Forest Service. The area is characteristic of the central Rocky Mountains and trace gas monitoring indicates that little anthropogenic pollution is transported from the nearby urban areas (Kim et al. 2010 and references therein). Ambient and enclosure samples were collected on ATD (adsorption/thermal desorption) cartridges and analyzed for BVOCs using two-dimensional gas chromatography (GC×GC) with time of flight mass spectrometry (TOFMS) and flame ionized detection (FID). Measurements of BVOC species, including mono- and sesquiterpenes and oxygenated mono- and sesquiterpenes, will be presented. The results will be discussed in the context of atmospheric composition and SOA formation.

Roskamp, M.; Lou, W.; Pankow, J. F.; Harley, P. C.; Turnipseed, A.; Barsanti, K. C.

2012-12-01

273

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

274

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

275

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

277

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

278

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

279

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

280

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

281

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

282

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

NASA Astrophysics Data System (ADS)

A significant fraction of atmospheric organic compounds are predominantly found in condensed phases, such as organic phase in aerosol particles or aqueous phase in cloud droplets. The oxidation of VOCs followed by the condensation of products into particles was thought to be the main mechanism of organic aerosol (OA) formation. However, in the last several years, scientists have realized that a large fraction, if not the majority of organic particles, is produced through cloud and fog photochemical processes. Many of these organic compounds are photolabile, and can degrade through direct photolysis or indirect photooxidation processes on time scales that are comparable to the typical lifetimes of droplets (hours) and particles (days). We previously reported that compounds in secondary organic aerosol (SOA) from ozonolysis of d-limonene efficiently photodegrade in both organic (Walser et al., 2007) and aqueous phases (Bateman et al., 2011). Significant photolysis was also observed in an aqueous extract of SOA from high-NOx photooxidation of isoprene (Nguyen et al., 2012). More recent experiments studying the response to irradiation of complex aqueous mixtures (as opposed to solutions of isolated compounds) found surprising resilience to photodegradation in aqueous extracts of SOA prepared by photooxidation of alpha-pinene (Romonosky et al., unpublished). We present a systematic investigation of the extent of photochemical processing in different types of SOA from various biogenic and anthropogenic precursors. Chamber- or flowtube-generated SOA is collected on an inert substrate, extracted in a methanol/water solution (70:30), photolyzed in the aqueous solution, and the extent of change in the molecular level composition of the material is assessed with high-resolution mass spectrometry (HR-MS). The outcome of this study will be improved understanding of the role of condensed-phase photochemistry in chemical aging of aerosol particles and cloud droplets. Bateman et al. Photolytic processing of secondary organic aerosols dissolved in cloud droplets. Phys. Chem. Chem. Phys. 2011, 13, 12199. Nguyen et al. Direct aqueous photochemistry of isoprene high-NOx secondary organic aerosol. Phys. Chem. Chem. Phys. 2012, 14, 9702. Walser et al. Photochemical aging of secondary organic aerosol particles generated from the oxidation of d-limonene. J. Phys. Chem. A 2007, 111, 1907.

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

2013-12-01

283

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

284

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

285

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

286

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 ...

287

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...

288

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

289

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

2012-11-20

290

Heterogeneous Chemistry of Glyoxal on Acidic Solutions. An Oligomerization Pathway for Secondary Organic Aerosol Formation.  

PubMed

The heterogeneous chemistry of glyoxal on sulfuric acid surfaces has been investigated at various acid concentrations and temperatures, utilizing a low-pressure fast flow laminar reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS). The uptake coefficient (?) of glyoxal ranges from (1.2 ± 0.06) × 10(-2) to (2.5 ± 0.01) × 10(-3) for 60-93 wt % H2SO4 at 253-273 K. The effective Henry's Law constant (H*) ranges from (98.9 ± 4.9) × 10(5) to (1.6 ± 0.1) × 10(5) M atm(-1) for 60-93 wt % at 263-273 K. Both the uptake coefficient and Henry's Law constant increase with decreasing acid concentration and temperature. Our results reveal a reaction mechanism of hydration followed by oligomerization for glyoxal on acidic media, indicating an efficient aqueous reaction of glyoxal on hygroscopic particles leading to secondary organic aerosol formation. PMID:25369518

Gomez, Mario E; Lin, Yun; Guo, Song; Zhang, Renyi

2014-11-20

291

Effect of bark beetle infestation on secondary organic aerosol precursor emissions.  

PubMed

Bark beetles are a potentially destructive force in forest ecosystems; however, it is not known how insect attacks affect the atmosphere. The emissions of volatile organic compounds (VOCs) were sampled i.) from bark beetle infested and healthy lodgepole pine (Pinus contorta var. latifolia) trees and ii.) from sites with and without active mountain pine beetle infestation. The emissions from the trunk and the canopy were collected via sorbent traps. After collection, the sorbent traps were extracted with hexane, and the extracts were separated and detected using gas chromatography/mass spectroscopy. Canister samples were also collected and analyzed by a multicolumn gas chromatographic system. The samples from bark beetle infested lodgepole pine trees suggest a 5- to 20-fold enhancement in total VOCs emissions. Furthermore, increases in the ?-phellandrene emissions correlated with bark beetle infestation. A shift in the type and the quantity of VOC emissions can be used to identify bark beetle infestation but, more importantly, can lead to increases in secondary organic aerosol from these forests as potent SOA precursors are produced. PMID:22545866

Amin, Hardik; Atkins, P Tyson; Russo, Rachel S; Brown, Aaron W; Sive, Barkley; Hallar, A Gannet; Huff Hartz, Kara E

2012-06-01

292

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

293

Secondary organic aerosol contributions to PM2.5 in Monterrey, Mexico: Temporal and seasonal variation  

NASA Astrophysics Data System (ADS)

Air pollution caused by fine particles is a problem of great concern in the Monterrey Metropolitan Area (MMA) which is the third largest city and the second most important industrial center in Mexico. In this study, samples of fine particulate matter emissions with an aerodynamic diameter of less than 2.5 ?m (PM2.5) were collected for 12-hour periods during the spring and fall of 2011 and 2012. Eighty-three samples were analyzed for organic carbon (OC) and elemental carbon (EC). The carbonaceous fraction (OC + EC) accounted for 28-55% of the PM2.5 mass. The average OC/EC ratios ranged from 7.4 to 12.6, and OC and EC concentrations were statistically significant correlated (R2 = 0.81, p < 0.01). The secondary organic aerosol (SOA) contributions were determined using two approaches: the EC tracer method based on a primary OC/EC ratio derived from a tunnel study and the minimum observed OC/EC ratio. SOAs were determined to constitute, on average, 59-87% and 32-45% of the total OC and PM2.5, respectively. The relationship between O3 and wind speed indicated that pollutant levels were influenced by transport events during the spring, while stagnation events predominated during the fall campaigns. Statistically significant correlations were observed between OC and EC and gaseous species (CO, NOx, and SO2), indicating a contribution by combustion of fossil fuels to the carbonaceous material.

Mancilla, Yasmany; Herckes, Pierre; Fraser, Matthew P.; Mendoza, Alberto

2015-02-01

294

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

SciTech Connect

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

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

2008-01-01

295

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

SciTech Connect

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

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

2012-10-25

296

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

297

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

298

Soot aggregate restructuring due to coatings of secondary organic aerosol derived from aromatic precursors.  

PubMed

Restructuring of monodisperse soot aggregates due to coatings of secondary organic aerosol (SOA) derived from hydroxyl radical-initiated oxidation of toluene, p-xylene, ethylbenzene, and benzene was investigated in a series of photo-oxidation (smog) chamber experiments. Soot aggregates were generated by combustion of ethylene using a McKenna burner, treated by denuding, size-selected by a differential mobility analyzer, and injected into a smog chamber, where they were exposed to low vapor pressure products of aromatic hydrocarbon oxidation, which formed SOA coatings. Aggregate restructuring began once a threshold coating mass was reached, and the degree of the subsequent restructuring increased with mass growth factor. Although significantly compacted, fully processed aggregates were not spherical, with a mass-mobility exponent of 2.78, so additional SOA was required to fill indentations between collapsed branches of the restructured aggregates before the dynamic shape factor of coated particles approached 1. Trends in diameter growth factor, effective density, and dynamic shape factor with increasing mass growth factor indicate distinct stages in soot aggregate processing by SOA coatings. The final degree and coating mass dependence of soot restructuring were found to be the same for SOA coatings from all four aromatic precursors, indicating that the surface tensions of the SOA coatings are similar. PMID:25390075

Schnitzler, Elijah G; Dutt, Ashneil; Charbonneau, André M; Olfert, Jason S; Jäger, Wolfgang

2014-12-16

299

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

NASA Astrophysics Data System (ADS)

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

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

300

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

EPA Science Inventory

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

301

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...

302

Secondary organic aerosol formation from hydroxyl radical oxidation and ozonolysis of monoterpenes  

NASA Astrophysics Data System (ADS)

Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compound (BVOC) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (?-pinene, ?-pinene and limonene) by OH-dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction) chamber in Jülich, Germany, at low NOx (0.01 ~ 1 ppbV) and low ozone (O3) concentration (< 20 ppbV). OH concentration and total OH reactivity (kOH) were measured directly, and through this the overall reaction rate of total organics with OH in each reaction system was quantified. Multi-generation reaction process, particle growth, new particle formation (NPF), particle yield and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH-dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction rate of OH with total organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to play an important role after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that, generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of ?-pinene and limonene by ozonolysis was higher than that of OH oxidation. Aerosol mass spectrometry (AMS) shows SOA elemental composition from OH oxidation follows a slope shallower than -1 in the O / C vs. H / C diagram, also known as Van Krevelen diagram, indicating that oxidation proceeds without significant loss of hydrogen. SOA from OH oxidation had higher H / C ratios than SOA from ozonolysis. In ozonolysis, a process with significant hydrogen loss seemed to play an important role in SOA formation.

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

2015-01-01

303

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

NASA Astrophysics Data System (ADS)

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 and Ox measured in Mexico City in 2006 and Houston in 2000 were well correlated in air masses where both species were formed on similar timescales (less than 8 h) and not well correlated when their formation timescales or location differed greatly. When correlated, the ratio of these two species ranged from 30 ?g m-3/ppm (STP) in Houston during time periods affected by large petrochemical plant emissions to as high as 160 ?g m-3/ppm in Mexico City, where typical values were near 120 ?g m-3/ppm. On several days in Mexico City, the [OOA]/[Ox] ratio decreased by a factor of ~2 between 08:00 and 13:00 local time. This decrease is only partially attributable to evaporation of the least oxidized and most volatile components of OOA; differences in the diurnal emission trends and timescales for photochemical processing of SOA precursors compared to ozone precursors also likely contribute to the observed decrease. The extent of OOA oxidation increased with photochemical aging. Calculations of the ratio of the SOA formation rate to the Ox production rate using ambient VOC measurements and traditional laboratory SOA yields are lower than the observed [OOA]/[Ox] ratios by factors of 5 to 15, consistent with several other models' underestimates of SOA. Calculations of this ratio using emission factors for organic compounds from gasoline and diesel exhaust do not reproduce the observed ratio. Although not succesful in reproducing the atmospheric observations presented, modeling P(SOA)/P(Ox) can serve as a useful test of photochemical models using improved formulation mechanisms for SOA.

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

2010-09-01

304

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

NASA Astrophysics Data System (ADS)

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 and Ox measured in Mexico City in 2006 and Houston in 2000 were well correlated in air masses where both species were formed on similar timescales (less than 8 h) and not well correlated when their formation timescales or location differed greatly. When correlated, the ratio of these two species ranged from 30 ?g m-3 ppm-1 (STP) in Houston during time periods affected by large petrochemical plant emissions to as high as 160 ?g m-3 ppm-1 in Mexico City, where typical values were near 120 ?g m-3 ppm-1. On several days in Mexico City, the [OOA]/[Ox] ratio decreased by a factor of ~2 between 08:00 and 13:00 LT. This decrease is only partially attributable to evaporation of the least oxidized and most volatile components of OOA; differences in the diurnal emission trends and timescales for photochemical processing of SOA precursors compared to ozone precursors also likely contribute to the observed decrease. The extent of OOA oxidation increased with photochemical aging. Calculations of the ratio of the SOA formation rate to the Ox production rate using ambient VOC measurements and traditional laboratory SOA yields are lower than the observed [OOA]/[Ox] ratios by factors of 5 to 15, consistent with several other models' underestimates of SOA. Calculations of this ratio using emission factors for organic compounds from gasoline and diesel exhaust do not reproduce the observed ratio. Although not succesful in reproducing the atmospheric observations presented, modeling P(SOA)/P(Ox) can serve as a useful test of photochemical models using improved formulation mechanisms for SOA.

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

2010-02-01

305

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

306

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

307

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

NASA Astrophysics Data System (ADS)

Oxidation by hydroxyl radical (OH) and ozonolysis are the two major pathways of daytime biogenic volatile organic compounds (VOCs) oxidation and secondary organic aerosol (SOA) formation. In this study, we investigated the particle formation of several common monoterpenes (?-pinene, ?-pinene, and limonene) by OH dominated oxidation, which has seldom been investigated. OH oxidation experiments were carried out in the SAPHIR chamber in Jülich, Germany, at low NOx (0.01-1 ppbV) and low ozone (O3) concentration. OH concentration and OH reactivity were measured directly so that the overall reaction rates of organic compounds with OH were quantified. Multi-generation reaction process, particle growth, new particle formation, particle yield, and chemical composition were analyzed and compared with that of monoterpene ozonolysis. Multi-generation products were found to be important in OH dominated SOA formation. The relative role of functionalization and fragmentation in the reaction process of OH oxidation was analyzed by examining the particle mass and the particle size as a function of OH dose. We developed a novel method which quantitatively links particle growth to the reaction of OH with organics in a reaction system. This method was also used to analyze the evolution of functionalization and fragmentation of organics in the particle formation by OH oxidation. It shows that functionalization of organics was dominant in the beginning of the reaction (within two lifetimes of the monoterpene) and fragmentation started to be dominant after that. We compared particle formation from OH oxidation with that from pure ozonolysis. In individual experiments, growth rates of the particle size did not necessarily correlate with the reaction rate of monoterpene with OH and O3. Comparing the size growth rates at the similar reaction rates of monoterpene with OH or O3 indicates that generally, OH oxidation and ozonolysis had similar efficiency in particle growth. The SOA yield of ?-pinene and limonene by ozonolysis was higher than that of OH oxidation. Aerosol mass spectrometry (AMS) shows SOA elemental composition from OH oxidation follows a slope shallower than -1 in the O / C vs. H / C diagram, indicating that oxidation proceeds without significant loss of hydrogen. SOA from OH oxidation had higher H / C ratios than SOA from ozonolysis. In ozonolysis, a process with significant hydrogen loss seemed to play an important role in SOA formation.

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

2014-05-01

308

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

NASA Astrophysics Data System (ADS)

The atmospheric oxidation of Volatile Organic Compounds (VOCs) in the presence of NOx results in the formation of tropospheric ozone and Secondary Organic Aerosol (SOA) [Hallquist et al., 2009]. Whilst SOA is known to affect both climate and human health, the VOC oxidation pathways leading to SOA formation are poorly understood [Solomon et al., 2007]. This is in part due to the vast number and the low concentration of SOA species present in the ambient atmosphere. It has been estimated as many as 10,000 to 100,000 VOCs have been detected in the atmosphere, all of which can undergo photo-chemical oxidation and contribute to SOA formation [Goldstein and Galbally, 2007]. Atmospheric simulation chambers such as the EUropean PHOtoREactor (EUPHORE) in Valencia, Spain, are often used to study SOA formation from a single VOC precursor under controlled conditions. SOA composition and formation can be studied using online techniques such as Aerosol Mass Spectrometry (AMS), which provide high time resolution but limited structural information [Zhang et al., 2007]. Offline techniques, such as collection onto filters, extraction and subsequent analysis, provide detailed SOA composition but only usually one or two samples per experiment. In this work we report time resolved SOA composition analysis using a Particle into Liquid Sampler (PILS) followed by Liquid Chromatography Ion-Trap Mass Spectrometry (LC-IT-MS/MS) and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS/MS). Experiments were performed at EUPHORE investigating the formation and composition of Methyl Chavicol SOA. Methyl Chavicol (also known as Estragole) was identified as the highest floral emission from an oil palm plantation in Malaysian Borneo and has also been observed in US pine forests [Bouvier-Brown et al., 2009; Misztal et al., 2010]. Previous studies indicate a high SOA yield from Methyl Chavicol at around 40 % [Lee et al., 2006], however currently there have been very few literature reports of the atmospheric degradation of Methyl Chavicol. Methyl Chavicol oxidation was investigated using a series of photosmog and ozonolysis experiments with varying ratios of NOx:VOC. An extensive range of instruments were used to monitor radical and product formation [including: LIF (HOx intermediates), LOPAP (HONO), FT-IR, PTR-MS, GC-FID, and SMPS]. Samples were collected using the PILS at 30 minute intervals with filters taken at the end of each experiment for comparison. A number of key oxidation products have been identified. Time profiles can be used to determine the importance of first, second & higher oxidation products and may indicate which species are undergoing oxidation or heterogeneous reactions during aerosol ageing. This data will allow for modelled vs. measured SOA composition comparison, with the potential to determine the rates of reactions for the condensed phase oxidation products formed. References Bouvier-Brown et al., Atmos. Chem. Phys. 9, 2061-2074, 2009. Goldstein and Galbally, Environ. Sci. Technol. 41, 1514-1521, 2007. Hallquist et al., Atmos. Chem. Phys. 9, 5155-5236, 2009. Lee et al., J. Geophys. Res. 111, D17305, 2006. Misztal et al., Atmos. Chem. Phys. Discuss. 10, 1517-1557, 2010. Solomon et al., Climate Change 2007: IPCC Report. Cambridge, 2007. Zhang et al., Geophys. Res. Lett. 34, L13801, 2007.

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

2012-12-01

309

Improving the representation of secondary organic aerosol (SOA) in the MOZART-4 global chemical transport model  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) module in the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) was updated by replacing existing two-product (2p) parameters with those obtained from two-product volatility basis set (2p-VBS) fits (MZ4-C1), and by treating SOA formation from the following additional volatile organic compounds (VOCs): isoprene, propene and lumped alkenes (MZ4-C2). Strong seasonal and spatial variations in global SOA distributions were demonstrated, with significant differences in the predicted concentrations between the base case and updated model simulations. Updates to the model resulted in significant increases in annual average SOA mass concentrations, particularly for the MZ4-C2 simulation in which the additional SOA precursor VOCs were treated. Annual average SOA concentrations predicted by the MZ4-C2 simulation were 1.00 ± 1.04 ?g m-3 in South America, 1.57 ± 1.88 ?g m-3 in Indonesia, 0.37 ± 0.27 ?g m-3 in the USA, and 0.47 ± 0.29 ?g m-3 in Europe with corresponding increases of 178, 406, 311 and 292% over the base-case simulation, respectively, primarily due to inclusion of isoprene. The increases in predicted SOA mass concentrations resulted in corresponding increases in SOA contributions to annual average total aerosol optical depth (AOD) by ~ 1-6%. Estimated global SOA production was 5.8, 6.6 and 19.1 Tg yr-1 with corresponding burdens of 0.22, 0.24 and 0.59 Tg for the base-case, MZ4-C1 and MZ4-C2 simulations, respectively. The predicted SOA budgets fell well within reported ranges for comparable modeling studies, 6.7 to 96 Tg yr-1, but were lower than recently reported observationally constrained values, 50 to 380 Tg yr-1. For MZ4-C2, simulated SOA concentrations at the surface also were in reasonable agreement with comparable modeling studies and observations. Total organic aerosol (OA) mass concentrations at the surface, however, were slightly over-predicted in Europe, Amazonian regions and Malaysian Borneo (Southeast Asia) during certain months of the year, and under-predicted in most sites in Asia; relative to those regions, the model performed better for sites in North America. Overall, with the inclusion of additional SOA precursors (MZ4-C2), namely isoprene, MOZART-4 showed consistently better skill (NMB (normalized mean bias) of -11 vs. -26%) in predicting total OA levels and spatial distributions of SOA as compared with unmodified MOZART-4. Treatment of SOA formation by these known precursors (isoprene, propene and lumped alkenes) may be particularly important when MOZART-4 output is used to generate boundary conditions for regional air quality simulations that require more accurate representation of SOA concentrations and distributions.

Mahmud, A.; Barsanti, K.

2013-07-01

310

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

311

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

SciTech Connect

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

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

2014-05-14

312

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

313

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. PMID:20176970

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

2010-01-01

314

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

NASA Astrophysics Data System (ADS)

Glyoxal, a common organic gas in the atmosphere, has been identified in recent years as an important Secondary Organic Aerosol (SOA) precursor (Volkamer et al., 2007). But, unlike with other precursors, the SOA is largely produced by particle-phase reactions (Volkamer et al., 2009) and equilibria (Kampf et al. 2013) that are still not entirely characterized. Since 2009 series of smog chamber experiments have been performed within the Eurochamp program at the Paul Scherrer Institute, Switzerland, to investigate SOA formation from glyoxal. In these experiments, glyoxal was produced by the gas-phase oxidation of acetylene in the presence of seeds, the seed composition and other conditions being varied. The 2011 campaign resulted in the identification of salting processes controlling the glyoxal partitioning in the seeds (Kampf et al. 2013). This presentation will report results of the 2013 campaign focusing on the identification of the various reactions (ionic or photo-induced) contributing to the SOA mass. In particular, the contribution of the ionic reactions, i.e. mediated by NH4+, were investigated by quantifying the formation of imidazoles (imidazole, imidazole-2-carboxaldehyde, 2,2'-biimidazole) from the small condensation channel of glyoxal with ammonia. For this, the SOA produced were collected on quartz filters and analyzed by Orbitrap LC/MS (Q-Exactive Thermo Fisher). The formation of other products such as organic acids was also investigated to determine potential competing reactions. Time-resolved MOUDI sampling coupled with nano-DESY/ESI-MS/MS analysis was also used to identify nitrogen- and sulphur-containing products from all the reactions. The results obtained for a range of conditions will be presented and compared with recent mechanistic information on the ionic reaction channels (Nozière et al., in preparation, 2013). The implementation of all this new information into a glyoxal-SOA model will be discussed.

Maxut, Aurelia; Nozière, Barbara; Rossignol, Stéphanie; George, Christian; Waxman, Eleanor Marie; Laskin, Alexander; Slowik, Jay; Dommen, Josef; Prévôt, André; Baltensperger, Urs; Volkamer, Rainer

2014-05-01

315

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

316

Spatial distributions of secondary organic aerosols from isoprene, monoterpenes, ?-caryophyllene, and aromatics over China during summer  

NASA Astrophysics Data System (ADS)

particle samples were simultaneously collected at 14 sites across 6 regions of China during the summer of 2012. These filters were analyzed for secondary organic aerosol (SOA) tracers from biogenic precursors (isoprene, monoterpenes, and ?-caryophyllene) and anthropogenic aromatics. The sum of all SOA tracers ranged from 29.9 to 371 ng m-3 with the majority from isoprene (123 ± 78.8 ng m-3), followed by monoterpenes (10.5 ± 6.64 ng m-3), ?-caryophyllene (5.07 ± 3.99 ng m-3), and aromatics (2.90 ± 1.52 ng m-3). The highest levels of biogenic SOA tracers were observed in East China, whereas the highest concentrations of the aromatic SOA tracer, 2,3-dihydroxy-4-oxopentanoic acid (DHOPA), occurred in North China. All biogenic SOA tracers exhibited positive correlations with temperature, most likely resulting from enhanced biogenic volatile organic compounds (BVOCs) emissions and photochemistry in high-temperature regions. Among the isoprene SOA tracers, the low-NOx products 2-methyltetrols were the largest by mass concentration. However, at certain urban sites, the contribution of the high-NOx product 2-methylglyceric acid was significantly higher, implying a greater influence of NOx on isoprene SOA formation in urban areas. For the monoterpene SOA tracers, the ratio of the first-generation products (cis-pinonic acid plus pinic acid) to the high-generation product (3-methyl-1,2,3-butanetricarboxylic acid) exhibited a negative correlation with the amount of high-generation products, indicating that this ratio could serve as an indicator of the aging of monoterpene SOA. The ratio ranged from 0.89 to 21.0, with an average of 7.00 ± 6.02, among the observation sites, suggesting that monoterpene SOA was generally fresh over China during the summer. As a typical anthropogenic SOA tracer, DHOPA exhibited higher levels at urban sites than at remote sites. These SOA tracers were further used to attribute SOA origins via the SOA-tracer method. The total concentrations of secondary organic carbon (SOC) and SOA were estimated to be in the range of 0.37 to 2.47 ?gC m-3 and 0.81 to 5.44 µg m-3, respectively, with the highest levels observed in the eastern regions of China. Isoprene (46 ± 14%) and aromatics (27 ± 8%) were the two major contributors to SOC in every region. In North China, aromatics were the largest SOA contributor. Our ground-based observations suggest that anthropogenic aromatics are important SOA precursors in China.

Ding, Xiang; He, Quan-Fu; Shen, Ru-Qin; Yu, Qing-Qing; Wang, Xin-Ming

2014-10-01

317

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

318

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

319

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

320

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

321

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

322

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

EPA Science Inventory

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

323

Secondary Organic Aerosol (SOA) formation from the ?-pinene + NO3 system: effect of humidity and peroxy radical fate  

NASA Astrophysics Data System (ADS)

The formation of secondary organic aerosol (SOA) from the oxidation of ?-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber facility (GTEC). Aerosol yields are determined for experiments performed under both dry (RH < 2%) and humid (RH = 50% and RH = 70%) conditions. To probe the effects of peroxy radical (RO2) fate on aerosol formation, "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are performed. Gas-phase organic nitrate species (with molecular weights of 215, 229, 231 and 245 amu) are detected by chemical ionization mass spectrometry and their formation mechanisms are proposed. The ions at m/z 30 (NO+) and m/z 46 (NO2+) contribute about 11% to the total organics signal in the typical aerosol mass spectrum, with NO+ : NO2+ ratio ranging from 6 to 9 in all experiments conducted. The SOA yields in the "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are comparable. For a wide range of organic mass loadings (5.1-216.1 ?g m-3), the aerosol mass yield is calculated to be 27.0-104.1%. Although humidity does not appear to affect SOA yields, there is evidence of particle-phase hydrolysis of organic nitrates, which are estimated to compose 45-74% of the organic aerosol. The extent of organic nitrate hydrolysis is significantly lower than that observed in previous studies on photooxidation of volatile organic compounds in the presence of NOx. It is estimated that about 90 and 10% of the organic nitrates formed from the ?-pinene + NO3 reaction are primary organic nitrates and tertiary organic nitrates, respectively. While the primary organic nitrates do not appear to hydrolyze, the tertiary organic nitrates undergo hydrolysis with a lifetime of 3-4.5 h. Results from this laboratory chamber study provide the fundamental data to evaluate the contributions of monoterpene + NO3 reaction to ambient organic aerosol measured in the southeastern United States, including the Southern Oxidant and Aerosol Study (SOAS) and the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study.

Boyd, C. M.; Sanchez, J.; Xu, L.; Eugene, A. J.; Nah, T.; Tuet, W. Y.; Guzman, M. I.; Ng, N. L.

2015-01-01

324

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

NASA Astrophysics Data System (ADS)

The dry deposition of volatile organic compounds (VOCs) and its impact on secondary organic aerosols (SOA) are investigated in the Mexico City plume. Gas-phase chemistry and gas-particle partitioning of oxygenated VOCs are modeled with the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) from C3 to C25 alkanes, alkenes, and light aromatics. Results show that dry deposition of oxidized gases is not an efficient sink for SOA, as it removes <5% of SOA within the city's boundary layer and ~15% downwind. Dry deposition competes with the gas-particle uptake, and only gases with fewer than ~12 carbons dry deposit while longer species partition to SOA. Because dry deposition of submicron aerosols is slow, condensation onto particles protects organic gases from deposition, thus increasing their atmospheric burden and lifetime. In the absence of this condensation, ~50% of the regionally produced mass would have been dry deposited.

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

2013-06-01

325

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

326

Experimental and modeling studies of secondary organic aerosol formation and some applications to the marine boundary layer  

NASA Astrophysics Data System (ADS)

A series of controlled experiments were carried out in the Calspan Corporation's 600 m3 environmental chamber to study some secondary organic aerosol formation processes. Three precursor-ozone systems were studied: cyclopentene-ozone, cyclohexene-ozone, and ?-pineneozone. Additionally, SO2 was added to the initial gas mixture in several instances and was likely present at trace levels in the ostensibly organic-only experiments. It was found that all three systems readily formed new submicron aerosols at very low reactant levels. The chemical composition of formed aerosols was consistent with some previous studies, but the yields of organic products were found to be lower in the Calspan experiments. A three-step procedure is proposed to explain the observed particle nucleation behavior: HO · production ? H2SO4 formation ? H2SO4-H2O (perhaps together with NH3) homogeneous nucleation. It is also proposed that some soluble organic products would partition into the newly formed H2SO4-H2O nuclei, enhance water condensation, and quickly grow these nuclei into a larger size range. While the observations in the two cycloolefin-ozone systems could be well explained by these proposed mechanisms, the exact nature of the nucleation process in the ?-pinene-ozone system remains rather opaque and could be the result of nucleation involving certain organics. The results from three simple modeling studies further support these proposals. Their applicability to the marine boundary layer (MBL) is also discussed in some detail. Particularly, such a particle nucleation and growth process could play an important role in secondary aerosol formation and, quite likely, CCN formation as well in certain MBL regions.

Gao, Song; Hegg, Dean A.; Frick, Glendon; Caffrey, Peter F.; Pasternack, Louise; Cantrell, Chris; Sullivan, William; Ambrusko, John; Albrechcinski, Thomas; Kirchstetter, Thomas W.

2001-11-01

327

Organic and inorganic aerosol compositions in Ulaanbaatar, Mongolia, during the cold winter of 2007 to 2008: Dicarboxylic acids, ketocarboxylic acids, and ?-dicarbonyls  

NASA Astrophysics Data System (ADS)

To investigate the distributions and sources of water-soluble organic acids in the Mongolian atmosphere, aerosol samples (PM2.5, n = 34) were collected at an urban site (47.92°N, 106.90°E, ˜1300 m above sea level) in Ulaanbaatar, the capital of Mongolia, during the cold winter. The samples were analyzed for water-soluble dicarboxylic acids (C2-C12) and related compounds (ketocarboxylic acids and ?-dicarbonyls), as well as organic carbon (OC), elemental carbon, water-soluble OC, and inorganic ions. Distributions of dicarboxylic acids and related compounds were characterized by a predominance of terephthalic acid (tPh; 130 ± 51 ng m-3, 19% of total detected organic acids) followed by oxalic (107 ± 28 ng m-3, 15%), succinic (63 ± 20 ng m-3, 9%), glyoxylic (55 ± 18 ng m-3, 8%), and phthalic (54 ± 27 ng m-3, 8%) acids. Predominance of terephthalic acid, which has not been reported previously in atmospheric aerosols, was mainly due to uncontrolled burning of plastic bottles and bags in home stoves for heating and waste incineration during the cold winter. This study demonstrated that most of the air pollutants were directly emitted from local sources such as heat and power plants, home stoves, and automobiles. Development of an inversion layer (<700 m above ground level) over the basin of Ulaanbaatar accelerated the accumulation of pollutants, causing severe haze episodes during the winter season.

Jung, Jinsang; Tsatsral, Batmunkh; Kim, Young J.; Kawamura, Kimitaka

2010-11-01

328

Secondary Organic Aerosol Formation during Evaporation of Droplets Containing Atmospheric Aldehydes, Amines, and Ammonium Sulfate.  

PubMed

Reactions of carbonyl compounds in cloudwater produce organic aerosol mass through in-cloud oxidation and during postcloud evaporation. In this work, postcloud evaporation was simulated in laboratory experiments on evaporating droplets that contain mixtures of common atmospheric aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol diameters were measured during monodisperse droplet drying experiments and during polydisperse droplet equilibration experiments at 75% relative humidity, and condensed-phase mass was measured in bulk thermogravimetric experiments. The evaporation of water from a droplet was found to trigger aldehyde reactions that increased residual particle volumes by a similar extent in room-temperature experiments, regardless of whether AS, methylamine, or glycine was present. The production of organic aerosol volume was highest from droplets containing glyoxal, followed by similar production from methylglyoxal or hydroxyacetone. Significant organic aerosol production was observed for glycolaldehyde, acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric experiments. In many experiments, the amount of aerosol produced was greater than the sum of all solutes plus nonvolatile solvent impurities, indicating the additional presence of trapped water, likely caused by increasing aerosol-phase viscosity due to oligomer formation. PMID:25409489

Galloway, Melissa M; Powelson, Michelle H; Sedehi, Nahzaneen; Wood, Stephanie E; Millage, Katherine D; Kononenko, Julia A; Rynaski, Alec D; De Haan, David O

2014-12-16

329

Secondary Organic Aerosol from On- and Off-Road Combustion Emissions: Scientific and Policy Perspectives  

NASA Astrophysics Data System (ADS)

Combustion emissions from on-road sources such as light duty gasoline vehicles (LDGV), medium duty diesel vehicles (MDDV) and heavy duty diesel vehicles (HDDV) as well as small off-road engines (SORE) such those used in lawn and garden equipment are a major source of fine particulate matter (PM) pollution in the ambient atmosphere. Existing regulations have restricted direct PM emissions, especially for on-road sources; however, recent studies suggest that organic PM formed from the photo-oxidation of gaseous precursor emissions—so-called secondary organic aerosol (SOA)—contributes at least as much to the overall PM burden as PM "emitted from the tailpipe." A major limitation of many of these studies is that they attempt to induce from the behavior of simple emission surrogates (e.g., vaporized whole fuel) the behavior of actual combustion emissions from real world sources. This research investigates combustion emissions directly. The primary gas- and particle-phase emissions, SOA production and SOA yields from a range of different on-road and off-road combustion sources were characterized. LDGV, MDDV and HDDV were driven on chassis dynamometers over realistic, urban driving cycles. Off-road sources, including 2- and 4-stroke lawn and garden equipment and a diesel transportation refrigeration unit were tested using engine dynamometers operated over certification cycles. For nearly all gasoline engines (LDGV and SOREs), photo-oxidizing dilute combustion emissions for 3 hours produced at least as much SOA as the directly emitted primary PM. SOA increased net PM production for LDGV by a factor of 1-10, depending on the vehicle emission standard. SOA yields were found to increase with newer vehicles, which have lower primary emissions. SOA for diesel vehicles, while still large on an absolute basis, was a smaller fraction of the primary PM emissions (between 10-30%), due to the very high elemental carbon (EC) emissions from vehicles without diesel particulate filters (DPF). Aftertreatment systems utilizing a DPF and a diesel oxidation catalyst essentially eliminated primary PM and SOA. Among the off-road sources, SOA from 2-stroke emissions increased the net PM by roughly a factor of 2. Primary emission and SOA production factors from the various combustion sources tested in this work were combined with fuel consumption data for California's South Coast Air Basin (SoCAB) to determine the impact on the aggregate PM from on- and off-road sources in the region. These estimated impacts were compared to the PM values derived from the regulatory models EMFAC and OFFROAD. Our data indicate that PM from on-road gasoline sources is significantly under-represented by existing emissions models due to the dominant role of SOA. When SOA production is included, newer LDGV are one of the largest sources of PM in SoCAB. Furthermore, LDGV will become an even more important PM source once existing regulations requiring DPF retrofits on both on- and off-road diesel sources are implemented over the next few years. While on-road diesel vehicles are currently an important source of PM based on total fuel consumption, LDGV are responsible for a larger fraction of total PM. The primary and secondary PM contribution of off-road sources also appear to be high, but the magnitude remains highly uncertain, pending further experimental data. Evidence is presented that suggests that existing models may dramatically overpredict primary PM emissions from off-road sources. Regulators are strongly urged to consider the impact of SOA on net PM production.

Gordon, Timothy D.

330

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

PubMed

We conducted photo-oxidation experiments in a smog chamber to investigate secondary organic aerosol (SOA) formation from eleven different unburned fuels: commercial gasoline, three types of jet fuel, and seven different diesel fuels. The goals were to investigate the influence of fuel composition on SOA formation and to compare SOA production from unburned fuel to that from diluted exhaust. The trends in SOA production were largely consistent with differences in carbon number and molecular structure of the fuel, i.e., fuels with higher carbon numbers and/or more aromatics formed more SOA than fuels with lower carbon numbers and/or substituted alkanes. However, SOA production from different diesel fuels did not depend strongly on aromatic content, highlighting the important contribution of large alkanes to SOA formation from mixtures of high carbon number (lower volatility) precursors. In comparison to diesels, SOA production from higher volatility fuels such as gasoline appeared to be more sensitive to aromatic content. On the basis of a comparison of SOA mass yields (SOA mass formed per mass of fuel reacted) and SOA composition (as measured by an aerosol mass spectrometer) from unburned fuels and diluted exhaust, unburned fuels may be reasonable surrogates for emissions from uncontrolled engines but not for emissions from engines with after treatment devices such as catalytic converters. PMID:24144104

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

2013-11-19

331

CCN Activity, Hygroscopicity, and Droplet Activation Kinetics of Secondary Organic Aerosol Resulting from the 2010 Gulf Oil Spill  

NASA Astrophysics Data System (ADS)

We present an analysis of the hygroscopicity and droplet activation kinetics of cloud condensation nuclei (CCN) sampled onboard the National Oceanic and Atmospheric Administration WP-3D aircraft downwind of the Deepwater Horizon oil spill site on June 8th and 10th, 2010. This set of measurements provides a unique case study for assessing in-situ the impact of fresh, hydrocarbonlike aerosols, which are expected to be formed via gas-to-particle conversion of the semi-volatile vapors released from oil evaporation. Similar hydrocarbon-rich aerosols constitute an important local emissions source in urban areas, but often coexist as an external/partially-internal mixture with more-oxidized, aged organic and sulfate aerosol. The DWH site provides the means to study the hygroscopic properties of these less-oxidized organic aerosols above a cleaner environmental background typical of marine environments in order to better discern their contribution to CCN activity and droplet growth. Measurements were performed with a Droplet Measurement Technologies Streamwise, Thermal-Gradient CCN counter, operating both as a counter (s=0.3%) and as a spectrometer (s=0.2-0.6%) using the newly-developed Scanning Flow CCN Analysis (SFCA) technique [1]. The instrument measures both the number concentration of particles able to nucleate droplets and also their resulting droplet sizes. The measured size information combined with a comprehensive computational fluid dynamics instrument model enables us to determine the rate of water uptake onto the particles and parameterize it in terms of an effective mass transfer coefficient [2], a key parameter needed to predict the number of activated droplets in ambient clouds. Non-refractory aerosol chemical composition was measured with an Aerodyne compact time-of-flight aerosol mass spectrometer. It was observed that the aerosols sampled downwind of the site on both days were composed predominantly of organics with a low degree of oxidation and low hygroscopicity (? ~ 0.05-0.1). It has been previously established for secondary organic aerosol that hygroscopicity increases with increasing oxidation (as characterized by the organic oxygen:carbon ratio) [3], and vice versa, and this dataset is used to evaluate this empirical finding. Particles measured in plumes downwind of the DWH site were seen to exhibit slow activation kinetics, consistent with a tenfold decrease in the mass transfer coefficient as compared to that of pure,