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1

Large particle collection characteristics of ambient aerosol samplers  

Microsoft Academic Search

Large particle collection characteristics of commercially available and prototype ambient aerosol samplers were quantitatively investigated by wind tunnel tests. The investigation was performed under conditions similar to those that the samplers would encounter in routine operation in the atmospheric boundary layer. The five samplers investigated were 1 CFM Andersen impactors, the General Metal Works Hi-Volume sampler, the Prototype Dichotomous sampler,

J. B. Wedding; A. R. McFarland; J. E. Cermak

1977-01-01

2

Collection efficiency for ambient aerosols on coarse pored nuclepore filters  

NASA Astrophysics Data System (ADS)

The stacked filter unit (SFU) with a coarse pored (5-12 ?m pore size) Nuclepore filter for collection of the "nonanthropogenic" parts of urban aerosols, is tested under ambient conditions. The PIXE method is used together with cascade impactors to separate the outdoor aerosol particles according to the aerodynamical diameter. The results are compared with results of laboratory experiments and theoretical considerations. It is shown that the collection efficiency is practically independent of the face velocity. The cutoff diameter changes almost as expected with the pore size, but the steepness of the cutoff curves are considerably less than predicted. This illustrates the insufficiency of using the single parameter "aerodynamic diameter" for describing the collection of the ambient particles with its odd shapes (fibers, conglomorates etc.).

Kemp, K.; Kownacka, L.

1987-03-01

3

Speciation of arsenic in ambient aerosols collected in Los Angeles  

SciTech Connect

The authors present measurements in the Los Angeles area, of the potentially toxic inorganic species of arsenic (arsenite and arsenate) obtained in fine and coarse atmospheric particles. A recently developed method -- which included procedures for sample collection, preparation, and analysis -- was used in this study. In this method, size-fractionated aerosol samples were collected using a high-volume dichotomous virtual impactor which employed PTFE filters. A section of each filter was leached in 10{sup -4} N HCl for 1 hour at 85{sup 0}C. The concentrations of As(III) and As(V) were then determined from a single sample aliquot by a two-step reduction procedure employing Zn metal powder and NaBH{sub 4}. The arsenic species produced during each reduction step (arsine) was then detected by flame atomic absorption spectroscopy. Using this method, results were obtained for the recovery of arsenic standards added to unexposed and collected filters. These data indicated, that this method can be used to quantitatively determine concentrations of As(III) and As(V) in atmospheric particulate matter samples collected in the Los Angeles area.

Rabano, E.S.; Castillo, N.T.; Torre, K.J. (California Air Resources Board, El Monte, CA (US)); Solomon, P.A. (California Inst. of Tech., Pasadena, CA (USA))

1987-01-01

4

Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Anions and cations  

Microsoft Academic Search

Ambient aerosol samples were collected over the Arabian Sea during the month of March 1997, aboard the German R\\/V Sonne, as part of the German JGOFS project (Joint Global Ocean Flux Study). This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high volume collector samples were

Anne M. Johansen; Michael R. Hoffmann

2004-01-01

5

Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Anions and cations  

Microsoft Academic Search

(1) Ambient aerosol samples were collected over the Arabian Sea during the month of March 1997, aboard the German R\\/V Sonne, as part of the German JGOFS project (Joint Global Ocean Flux Study). This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high volume collector samples

Anne M. Johansen

2004-01-01

6

New Portable Ambient Aerosol Sampler  

Microsoft Academic Search

The NBS portable ambient aerosol sampler is designed to collect respirable (below 3-µm) and inhalable (below 15-µm) particle size fractions for gravimetric and chemical analyses. The sampler is light, quiet and unobtrusive. We selected the components of the sampler on the basis of size, weight, price, and availability as well as performance. The inlet was intended to maintain constant collection

DAVID S. BRIGHT; ROBERT A. FLETCHER

1983-01-01

7

FOURIER TRANSFORM INFRARED SPECTROMETRY OF AMBIENT AEROSOLS  

EPA Science Inventory

Fourier transform infrared (FTIR) spectrometry has been evaluated as a method for determining the concentration of selected species present in ambient aerosols collected on Teflon filters. The filters are analyzed by transmission measurements after collection of the fine fraction...

8

Mass Spectrometric Analysis of Organic Aerosol Composition: Laboratory and Ambient  

NASA Astrophysics Data System (ADS)

Organic compounds contribute a significant mass fraction of ambient aerosol and play a role in determining the physiochemical properties of ambient aerosol. A significant fraction of organic aerosol is secondary organic aerosol (SOA), which is produced when the volatile organic compounds (VOCs) originated from various anthropogenic and biogenic sources react with atmospheric oxidants such as ozone, hydroxyl radicals, and nitrate radicals to form lower volatility organic compounds, which subsequently partition into the particle phase. Understanding the composition of ambient aerosol is crucial for identifying their sources and formation mechanisms and predicting their properties and effects on various ambient processes. This thesis focuses on investigating the composition of laboratory-generated SOA formed from the oxidation of biogenic VOCs of atmospheric importance (isoprene and beta-caryophyllene) and ambient aerosol collected in the field campaigns using advanced mass spectrometric techniques. By comparing the mass spectrometric data collected for the both laboratory-generated SOA and ambient aerosol, we propose reaction pathways and new chemical tracers for these biogenic VOCs, which enhance our knowledge of the composition, sources, and formation pathways of SOA in the atmosphere. With a better knowledge of the SOA composition, a product-specific model is proposed to predict the composition and aerosol mass yields (mass of SOA formed per mass of hydrocarbon reacted) of laboratory-generated ?-pinene SOA.

Chan, ManNin

9

FTIR (FOURIER TRANSFORM INFRARED) TRANSMISSION SPECTROMETRY FOR THE NONDESTRUCTIVE DETERMINATION OF AMMONIUM AND SULFATE IN AMBIENT AEROSOLS COLLECTED ON TEFLON FILTERS  

EPA Science Inventory

Fourier transform infrared transmission spectroscopy is used to analyze directly for sulfate and ammonium present in ambient aerosol particles deposited on Teflon filters. Integrated infrared peak areas for sulfate and ammonium are linearly related to x-ray fluorescence measureme...

10

Ambient aerosol sampling using the Aerodyne Aerosol Mass Spectrometer  

Microsoft Academic Search

The Aerodyne Aerosol Mass Spectrometer (AMS) has been designed to measure size-resolved mass distributions and total mass loadings of volatile and semivolatile chemical species in\\/on submicron particles. This paper describes the application of this instrument to ambient aerosol sampling. The AMS uses an aerodynamic lens to focus the particles into a narrow beam, a roughened cartridge heater to vaporize them

Jose L. Jimenez; John T. Jayne; Quan Shi; Charles E. Kolb; Douglas R. Worsnop; Ivan Yourshaw; John H. Seinfeld; Richard C. Flagan; Xuefeng Zhang; Kenneth A. Smith; James W. Morris; Paul Davidovits

2003-01-01

11

Characterization of Ambient Black Carbon Aerosols  

NASA Astrophysics Data System (ADS)

Because of the strong absorption over a broad range of the electromagnetic spectra, black carbon (BC) is a key short-lived climate forcer, which contributes significantly to climate change by direct radiative forcing and is the second most important component causing global warming after carbon dioxide. The impact of BC on the radiative forcing of the Earth-Atmosphere system is highly dependent of the particle properties. In this presentation, emphasis will be placed on characterizing BC containing aerosols in at the California-Mexico border to obtain a greater understanding of the atmospheric aging and properties of ambient BC aerosols. A comprehensive set of directly measured aerosol properties, including the particle size distribution, effective density, hygroscopicity, volatility, and several optical properties, will be discussed to quantify the mixing state and composition of ambient particles. In Tijuana, Mexico, submicron aerosols are strongly influenced by vehicle emissions; subsequently, the BC concentration in Tijuana is considerably higher than most US cities with an average BC concentration of 2.71 × 2.65 g cm-3. BC accounts for 24.75 % × 9.44 of the total submicron concentration on average, but periodically accounts for over 50%. This high concentration of BC strongly influences many observed aerosol properties such as single scattering albedo, hygroscopicity, effective density, and volatility.

Zhang, R.; Levy, M. E.; Zheng, J.; Molina, L. T.

2013-12-01

12

Analysis of Anions in Ambient Aerosols by Microchip Capillary Electrophoresis  

SciTech Connect

We describe a microchip capillary electrophoresis method for the analysis of nitrate and sulfate in ambient aerosols. Investigating the chemical composition of ambient aerosol particles is essential for understanding their sources and effects. Significant progress has been made towards developing mass spectrometry-based instrumentation for rapid qualitative analysis of aerosols. Alternative methods for rapid quantification of selected high abundance compounds are needed to augment the capacity for widespread routine analysis. Such methods could provide much higher temporal and spatial resolution than can be achieved currently. Inorganic anions comprise a large percentage of particulate mass with nitrate and sulfate among the most abundant species. While ion chromatography has proven very useful for analyzing extracts of time-integrated ambient aerosol samples collected on filters and for semi-continuous, on-line particle composition measurements, there is a growing need for development of new compact, inexpensive approaches to routine on-line aerosol ion analysis for deployment in spatially dense, atmospheric measurement networks. Microchip capillary electrophoresis provides the necessary speed and portability to address this need. In this report, on-column contact conductivity detection is used with hydrodynamic injection to create a simple microchip instrument for analysis of nitrate and sulfate. On-column contact conductivity detection was achieved using a Pd decoupler placed upstream from the working electrodes. Microchips containing two Au or Pd working electrodes showed a good linear range (5-500 µM) and low limits-of-detection for sulfate and nitrate with Au providing the lowest detection limits (1 µM) for both ions. The completed microchip system was used to analyze ambient aerosol filter samples. Nitrate and sulfate concentrations measured by the microchip matched the concentrations measured by ion chromatography.

Liu, Yan; MacDonald, David A.; Yu, Xiao-Ying; Hering, Susanne V.; Collett, Jeffrey L.; Henry, Charles S.

2006-10-01

13

Analysis of anions in ambient aerosols by microchip capillary electrophoresis.  

PubMed

We describe a microchip capillary electrophoresis method for the analysis of nitrate and sulfate in ambient aerosols. Investigating the chemical composition of ambient aerosol particles is essential for understanding their sources and effects. Significant progress has been made towards developing mass spectrometry-based instrumentation for rapid qualitative analysis of aerosols. Alternative methods for rapid quantification of selected high abundance compounds are needed to augment the capacity for widespread routine analysis. Such methods could provide much higher temporal and spatial resolution than can be achieved currently. Inorganic anions comprise a large percentage of particulate mass, with nitrate and sulfate among the most abundant species. While ion chromatography has proven very useful for analyzing extracts of time-integrated ambient aerosol samples collected on filters and for semi-continuous, on-line particle composition measurements, there is a growing need for development of new compact, inexpensive approaches to routine on-line aerosol ion analysis for deployment in spatially dense, atmospheric measurement networks. Microchip capillary electrophoresis provides the necessary speed and portability to address this need. In this report, on-column contact conductivity detection is used with hydrodynamic injection to create a simple microchip instrument for analysis of nitrate and sulfate. On-column contact conductivity detection was achieved using a Pd decoupler placed upstream from the working electrodes. Microchips containing two Au or Pd working electrodes showed a good linear range (5-500 microM) and low limits-of-detection for sulfate and nitrate, with Au providing the lowest detection limits (1 microM) for both ions. The completed microchip system was used to analyze ambient aerosol filter samples. Nitrate and sulfate concentrations measured by the microchip matched the concentrations measured by ion chromatography. PMID:17066191

Liu, Yan; MacDonald, David A; Yu, Xiao-Ying; Hering, Susanne V; Collett, Jeffrey L; Henry, Charles S

2006-11-01

14

DICHOTOMOUS SAMPLER - A PRACTICAL APPROACH TO AEROSOL FRACTIONATION AND COLLECTION  

EPA Science Inventory

Procedures to size fractionate, collect, and analyze ambient concentrations of particulate matter are described. Emphasis is placed on the design and characteristics of the single-stage dichotomous sampler. A new inlet is described that samples aerosol independent of wind speed a...

15

DEVELOPMENT OF A PORTABLE DEVICE TO COLLECT SULFURIC ACID AEROSOL  

EPA Science Inventory

A quantitative, interference-free method for collecting sulfuric acid aerosol on a filter was developed and field tested. Since previous research found that severe losses of sulfuric aicd were caused by ammonia, ambient particulate material, and other interferents, a method was n...

16

RADIOCARBON ANALYSIS OF PM 2.5 AMBIENT AEROSOL  

EPA Science Inventory

The radiocarbon (14C) content of an ambient aerosol sample can be directly related to the fraction of the sample's total carbon mass contributed by natural (biogenic) sources. Such knowledge is difficult to determine by other means, and important for devising ambient PM contro...

17

Characteristics of 2-methyltetrols in ambient aerosol in Beijing, China  

NASA Astrophysics Data System (ADS)

PM10 and PM2.5 samples were collected from November, 2010 to October, 2011 at Tsinghua University in Beijing. Various carbohydrates were quantified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol). A clear seasonal variation in the ambient 2-methyltetrol concentrations was observed, with the highest levels occurring in the summer, followed by autumn, spring and winter. The average concentrations of the 2-methyltetrols in PM10 and PM2.5 were 17.5 ± 15.4 ng m-3 and 13.8 ± 12.2 ng m-3, respectively. The 2-methyltetrols exhibited significant positive correlations with ambient relative humidity and temperature, likely due to the higher isoprene emission strength and enhanced formation yield under higher temperature and humidity conditions. In contrast, there was no relationship between the concentration of 2-methyltetrols and sunshine duration. The significant positive correlation (R2 = 0.76) between 2-methyltetrols and SO42- indicated that high concentrations of SO42- can increase the formation rate of 2-methyltetrols from isoprene. Moreover, 2-methyltetrols were also observed in the winter time in Beijing, illustrating the enhancement of the 2-methyltetrol formation rate by high concentrations of pollutants in ambient aerosol.

Liang, Linlin; Engling, Guenter; Duan, Fengkui; Cheng, Yuan; He, Kebin

2012-11-01

18

Contribution of woodsmoke and motor vehicle emissions to ambient aerosol mutagenicity  

Microsoft Academic Search

A multiple linear regression form of receptor modeling has been used to determine the sources of the mutagenicity of fine-particle ambient aerosol samples collected during the winter in a residential area of Albuquerque, NM. Virtually all the mutagenicity (Salmonella typhimurium TA98 + S9) could be accounted for by woodsmoke and motor vehicle emissions. Woodsmoke was found to be the greater

Charles W. Lewis; Ralph E. Baumgardner; Robert K. Stevens; Larry D. Claxton; Joellen Lewtas

1988-01-01

19

SAMPLING AND ANALYSIS METHODS FOR AMBIENT PM-10 AEROSOL  

EPA Science Inventory

Methods are described for obtaining ambient PM-10 aerosol data for use in receptor models. haracteristics of PM-10 sampling devices, filter media and laboratory analysis procedures are described. he latter include x-ray fluorescence, neutron activation, optical spectroscopy, pyro...

20

Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry Part I: quantification, shape-related collection efficiency, and comparison with collocated instruments  

NASA Astrophysics Data System (ADS)

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, while another was deployed in the Aerodyne Mobile Laboratory (AML) during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. This is the first of a series of papers reporting the AMS results from this campaign. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. For the first time, we report field results from a beam width probe, which was used to study the shape and mixing state of the particles and to quantify potential losses of irregular particles due to beam broadening inside the AMS. Data from this probe show that no significant amount of irregular particles was lost due to excessive beam broadening. A comparison of the CENICA and AML AMSs measurements is presented, being the first published intercomparison between two quadrupole AMSs. The speciation, and mass concentrations reported by the two AMSs compared relatively well. The differences found are likely due to the different inlets used in both instruments. In order to account for the refractory material in the aerosol, we also present measurements of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a Tapered Element Oscillating Microbalance (TEOM) and a DustTrak Aerosol Monitor) are also presented. The comparisons show that the AMS + BC + soil mass concentration during MCMA-2003 is a good approximation to the total PM2.5 mass concentration.

Salcedo, D.; Dzepina, K.; Onasch, T. B.; Canagaratna, M. R.; Zhang, Q.; Huffman, A.. R.; Decarlo, P. F.; Jayne, J. T.; Mortimer, P.; Worsnop, D. R.; Kolb, C. E.; Johnson, K. S.; Zuberi, B.; Marr, L. C.; Molina, L. T.; Molina, M. J.; Bernabé, R. M.; Cardenas, B.; Márquez, C.; Gaffney, J. S.; Marley, N. A.; Laskin, A.; Shutthanandan, V.; Jimenez, J. L.

2005-06-01

21

Activation of "synthetic ambient" aerosols - Relation to chemical composition of particles <100 nm  

NASA Astrophysics Data System (ADS)

Cloud condensation nuclei (CCN) are an important fraction of atmospheric aerosols because of their role in cloud formation. Experimental studies focus either on direct field measurements of complex ambient aerosols or laboratory investigations on well defined aerosols produced from single substances or substance mixtures. In this study, we focussed on the ultrafine aerosol because in terms of number concentration, the majority of the CCN are expected to have sizes in this range. A field study was performed from July 2007 to October 2008 to investigate the activation behaviour of the atmospheric aerosol in Vienna (Burkart et al., 2011). Filter samples of the aerosol <0.1 ?m aerodynamic equivalent diameter were collected, elutriated and used to generate "synthetic ambient" aerosol in a nebulizer. Chemical analyses of the ultrafine water soluble material were also performed. The CCN properties of the "synthetic ambient" aerosol were obtained using the University of Vienna CCN counter (Giebl et al., 2002; Dusek et al., 2006b) at a nominal supersaturation (SS) of 0.5%. Activation diameters dact ranged from 54.5 nm to 66 nm, were larger than dact of typical single inorganic salts and showed no seasonal pattern in contrast to the fraction of water soluble organic carbon (WSOC), which ranged from 44% in spring to 15% in winter. The average hygroscopicity parameter ? (Petters and Kreidenweis, 2007) obtained from the activation curves ranged from 0.20 to 0.30 (average 0.24), which was significantly lower than ?chem calculated from the chemical composition (0.43 ± 0.07).

Burkart, J.; Hitzenberger, R.; Reischl, G.; Bauer, H.; Leder, K.; Puxbaum, H.

2012-07-01

22

Contribution of woodsmoke and motor vehicle emissions to ambient aerosol mutagenicity  

SciTech Connect

A multiple linear regression form of receptor modeling has been used to determine the sources of the mutagenicity of fine-particle ambient aerosol samples collected during the winter in a residential area of Albuquerque, NM. Virtually all the mutagenicity (Salmonella typhimurium TA98 + S9) could be accounted for by woodsmoke and motor vehicle emissions. Woodsmoke was found to be the greater contributor to the average ambient concentrations of both extractable organ is and mutagenicity. The mutagenic potency (revertants per microgram) of extractable organics traced to motor vehicles, however, was 3 times greater than that with a woodsmoke origin. The results were confirmed by /sup 14/C measurements.

Lewis, C.W.; Baumgardner, R.E.; Stevens, R.K.; Claxton, L.D.; Lewtas, J.

1988-08-01

23

An analysis of diurnal cycles in the mass of ambient aerosols derived from biomass burning and agro-industry  

NASA Astrophysics Data System (ADS)

diurnal cycles in ambient aerosol mass were observed in a rural region of Southeast Brazil where the trace composition of the lower troposphere is governed mainly by emissions from agro-industry. An optical particle counter was used to record size-segregated aerosol number concentrations between 13 May 2010 and 15 March 2011. The data were collected every 10 min and used to calculate aerosol mass concentrations. Aerosol samples were also collected onto filters during daytime (10:00-16:00 local time) and nighttime (20:00-06:00) periods, for subsequent analysis of soluble ions and water-soluble organic carbon. Biomass burning aerosols predominated during the dry winter, while secondary aerosols were most important in the summer rainy season. In both seasons, diurnal cycles in calculated aerosol mass concentrations were due to the uptake of water by the aerosols and, to a lesser extent, to emissions and secondary aerosol formation. In neither season could the observed mass changes be explained by changes in the depth of the boundary layer. In the summer, nighttime increases in aerosol mass ranged from 2.7-fold to 81-fold, depending on particle size, while in the winter, the range was narrower, from 2.2-fold to 9.5-fold, supporting the possibility that the presence of particles derived from biomass burning reduced the overall ability of the aerosols to absorb water.

Caetano-Silva, L.; Allen, A. G.; Lima-Souza, M.; Cardoso, A. A.; Campos, M. L. A. M.; Nogueira, R. F. P.

2013-08-01

24

A New Technique for Collecting Ambient Diesel Particles for Bioassays  

Microsoft Academic Search

This paper describes a new application of a viable aerosol sampler, the Liquid Electrostatic Aerosol Precipitator (LEAP), for the collection of diesel particles for bioassays of pulmonary toxicity and mutagenicity or carcinogenicity. Currently used methods (filtration, dry electrostatic precipitation) cause agglomeration of particles and increases in particle size up to twenty-fold, which may alter particle toxicity significantly. Collection of diesel

MARILYN F. HALLOCK; THOMAS J. SMITH; S. KATHARINE HAMMOND; BARBARA D. BECK; JOSEPH D. BRAIN

1987-01-01

25

Processing of Ambient Aerosols During Fog Events: Role of Acidity  

NASA Astrophysics Data System (ADS)

Fog is a major processing and removal agent of ambient aerosols. Enhanced secondary organic aerosol (SOA) production has been reported during fog events indicating major role of aqueous processing. Present study was carried out in a heavily polluted city of Kanpur situated in Indo-Gangetic plain of India,from 02- 18 Nov, 2012 and then from 22 Dec, 2012 to 10 January, 2013. 12 fog events were identified from 22 Dec to 10 January based on low visibility (< 300 m) with high liquid water content (~ 0.04 g/m3) and termed as foggy period while remaining as non-foggy period. Foggy period typically showed very high RH (~95%), low temperatures (~2-6°C) compared to non-foggy period. An array of instruments were deployed during this campaign for real time measurement of aerosol physico-chemical properties - High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS), Scanning Mobility Particle Sizer (SMPS), Cloud Combination Probe (CCP), Cloud Condensation Nuclei counter (CCN), fog water collector and Vaisala RH & T sensor. Average aerosol loading during foggy period was 104×44 ?g/m3, much higher than 73×49 ?g/m3of non-foggy period, but during actual fog events the loading reduced to 85×23 ?g/m3 indicating overall aerosol removal by fog. Overall aerosol composition during both the period was dominated by organics which constitutes about 60-70% of the total AMS mass followed by nitrate, but during foggy period sulfate was found to be increased many fold.HR analysis of AMS data revealed noticeable differences in the diurnal average values of O:C ratio between foggy and non -foggy period. Although diurnal O:C ratio was highest around noontime for both period but during fog events, night to early morning O:C ratio was 0.51×0.04, higher than that of non-foggy period 0.44×0.07, clearly indicating enhanced oxidation. AMS data also showed that mode size of all the species specially of organics and sulphate had shifted to a higher diameter during foggy period, an indication of secondary processing. Aerosol acidity which is calculated from ratio of stoichiometric neutralization of ammonium to sulphate, nitrate and chloride, is playing a major role in aerosol processing. Highly oxidized aerosols (O:C> 0.6) in both periods were always either less acidic or completely neutralized, whereas less oxidized aerosols (O:C < 0.35) were either highly or mildly acidic in nature.Van Krevelen diagram of H/C vs O/C also showed different slopes for acidic and neutralized aerosols.Both these findings indicate that different processing mechanisms are operating under acidic and neutralized conditions.Organic hygroscopicity showed a linear relationship with oxidation level of organics or O:C ratio, which in turn depends on acidity,indicate neutralized aerosol to be most likely more CCN active than acidic aerosol.

Chakraborty, A.; Gupta, T.; Tripathi, S. N.; Bhattu, D.

2013-12-01

26

Speciation of Fe in ambient aerosol and cloudwater  

SciTech Connect

Atmospheric iron (Fe) is thought to play an important role in cloudwater chemistry (e.g., S(IV) oxidation, oxidant production, etc.), and is also an important source of Fe to certain regions of the worlds oceans where Fe is believed to be a rate-limiting nutrient for primary productivity. This thesis focuses on understanding the chemistry, speciation and abundance of Fe in cloudwater and aerosol in the troposphere, through observations of Fe speciation in the cloudwater and aerosol samples collected over the continental United States and the Arabian Sea. Different chemical species of atmospheric Fe were measured in aerosol and cloudwater samples to help assess the role of Fe in cloudwater chemistry.

Siefert, L. [California Institute of Technology, Pasadena, CA (United States)

1996-08-15

27

Studies of Ambient and Chamber Aerosol Composition using the Aerosol Mass Spectrometer  

NASA Astrophysics Data System (ADS)

This thesis presents composition measurements for atmospherically relevant inorganic and organic aerosol from laboratory and ambient measurements using the Aerodyne aerosol mass spectrometer. Studies include the oxidation of dodecane in the Caltech environmental chambers, and several aircraft- and ground-based field studies, which include the quantification of wildfire emissions off the coast of California, and Los Angeles urban emissions. The oxidation of dodecane by OH under low NO conditions and the formation of secondary organic aerosol (SOA) was explored using a gas-phase chemical model, gas-phase CIMS measurements, and high molecular weight ion traces from particlephase HR-TOF-AMS mass spectra. The combination of these measurements support the hypothesis that particle-phase chemistry leading to peroxyhemiacetal formation is important. Positive matrix factorization (PMF) was applied to the AMS mass spectra which revealed three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition. Airborne measurements of biomass burning emissions from a chaparral fire on the central Californian coast were carried out in November 2009. Physical and chemical changes were reported for smoke ages 0--4 h old. CO 2 normalized ammonium, nitrate, and sulfate increased, whereas the normalized OA decreased sharply in the first 1.5--2 h, and then slowly increased for the remaining 2 h (net decrease in normalized OA). Comparison to wildfire samples from the Yucatan revealed that factors such as relative humidity, incident UV radiation, age of smoke, and concentration of emissions are important for wildfire evolution. Ground-based aerosol composition is reported for Pasadena, CA during the sumix mer of 2009. The OA component, which dominated the submicron aerosol mass, was deconvolved into hydrocarbon-like organic aerosol (HOA), semi-volatile oxidized organic aerosol (SVOOA), and low-volatility oxidized organic aerosol (LVOOA). The HOA/OA was only 0.08--0.23, indicating that most of Pasadena OA in the summer months is dominated by oxidized OA resulting from transported emissions that have undergone photochemistry and/or moisture-influenced processing, as apposed to only primary organic aerosol emissions. Airborne measurements and model predictions of aerosol composition are reported for the 2010 CalNex field campaign.

Craven, Jill Suzanne

28

WOODSMOKE AND MOTOR VEHICLE CONTRIBUTION TO AMBIENT AEROSOL MUTAGENICITY  

EPA Science Inventory

A receptor model analysis of the mutagenicity of ambient fine particles in air samples collected under EPA's Integrated Air Cancer Project has been performed. he analysis was based on multiple linear regression, using measured concentrations of inorganic chemical elements which a...

29

A new technique for collecting ambient diesel particles for bioassays.  

PubMed

This paper describes a new application of a viable aerosol sampler, the Liquid Electrostatic Aerosol Precipitator (LEAP), for the collection of diesel particles for bioassays of pulmonary toxicity and mutagenicity or carcinogenicity. Currently used methods (filtration, dry electrostatic precipitation) cause agglomeration of particles and increases in particle size up to twenty-fold, which may alter particle toxicity significantly. Collection of diesel particles with the LEAP preserved submicronic particle size. Differences in chemical composition of extracts of surface adsorbents as compared to particles collected on filters also were observed. This technique may be applicable for collection of other types of combustion products or oil mists that agglomerate when collected by filtration. PMID:2438921

Hallock, M F; Smith, T J; Hammond, S K; Beck, B D; Brain, J D

1987-05-01

30

Investigation of thermodynamic properties of ambient and laboratory-generated multi- component organic aerosols  

NASA Astrophysics Data System (ADS)

Ambient aerosol, a significant portion of which is composed of a complex mixture of semi-volatile organic compounds, has substantial impact on human welfare via adverse health effects and global climate change. Prediction of ambient semi-volatile organic aerosol remains highly problematic and air quality models often do not agree with observations. One of the pieces of knowledge needed for better predictions of ambient semi- volatile organic aerosol is understanding of the partitioning of semi-volatile compounds between the gas and the aerosol phases. In this study the equilibrium thermodynamic properties of a number of multi-component aerosols were investigated under controlled laboratory conditions, as well as in the field. In the laboratory experiments, model mixtures of organic compounds as well as modified ambient aerosols were tested. The ambient aerosols were modified in a controlled way by adding known amounts of different organic substances of known thermodynamic properties. The equilibrium gas / aerosol partitioning in a temperature range relevant to ambient conditions was investigated using the Integrated Volume Method (IVM). The field measurements of ambient aerosol equilibrium properties were carried out during June 2007 - January 2008 at the FACTS research facility in Duke Forest (Chapel Hill, NC). The results can be used to derive equilibrium vapor pressures and activity coefficients of test compounds and to verify and improve the parameterizations used in group contribution models, such as UNFAC.

Khlystov, A.; Lin, M.; Saleh, R.

2008-12-01

31

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry  

NASA Astrophysics Data System (ADS)

The functional group composition of various organic aerosols (OA) is being investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCI-MS/MS). The determinations of the three functional groups' contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups) and precursor ion (nitro groups) scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA) produced through photo-oxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounted for 1.7% (vehicular) to 13.5% (o-xylene photo-oxidation) of the organic carbon. The diagnostic functional group ratios are then used to tentatively differentiate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France) during a strong winter pollution event. The three functional groups under study account for a total functionalisation rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to distinguish the sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assesses a wood burning organic carbon contribution of about 60%. Finally, examples of functional group mass spectra of all aerosols under study are presented, and additional perspectives offered by the mass spectra in terms of the OA characterisation are discussed.

Dron, J.; El Haddad, I.; Temime-Roussel, B.; Jaffrezo, J.-L.; Wortham, H.; Marchand, N.

2010-04-01

32

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry  

NASA Astrophysics Data System (ADS)

The functional group composition of various organic aerosols (OA) is investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCI-MS/MS). The determinations of three functional groups contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups, R-COOH and R-CO-? respectively) and precursor ion (nitro groups, R-NO2) scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA) produced through photooxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounts for 1.7% (vehicular) to 13.5% (o-xylene photooxidation) of the organic carbon. Diagnostic functional group ratios are then used to tentatively discriminate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France) during a strong winter pollution event. The three functional groups under study account for a total functionalisation rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to discriminate sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assess a wood burning organic carbon contribution of about 60%. Finally, examples of functional group mass spectra of all aerosols under study are presented, and additional perspectives offered by the mass spectra in terms of OA characterisation are discussed.

Dron, J.; El Haddad, I.; Temime-Roussel, B.; Jaffrezo, J.-L.; Wortham, H.; Marchand, N.

2010-08-01

33

On-line analysis of ambient air aerosols using laser-induced breakdown spectroscopy  

Microsoft Academic Search

Laser-induced breakdown spectroscopy is developed for the detection of aerosols in ambient air, including quantitative mass concentration measurements and size\\/composition measurements of individual aerosol particles. Data are reported for ambient air aerosols containing aluminum, calcium, magnesium and sodium for a 6-week sampling period spanning the Fourth of July holiday period. Measured mass concentrations for these four elements ranged from 1.7

J. E. Carranza; B. T. Fisher; G. D. Yoder; D. W. Hahn

2001-01-01

34

13C measurements on organic aerosol - a comparison of sources with ambient samples  

NASA Astrophysics Data System (ADS)

The stable carbon isotopes 12C and 13C can be used to get information about sources and processing of organic aerosol (OA). We developed and tested a method to measure ?13C values of OA collected on filter samples in different volatility classes. These filter samples are introduced into an oven, where organic compounds are thermally desorbed in He at different temperatures. The compounds released at each temperature step are oxidized to CO2 using a platinum catalyst at 550 °C. The CO2 is then passed on to an isotope ratio mass spectrometer (IRMS) to measure d13C ratios. With a similar setup the chemical composition at each temperature step can be determined using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS). System evaluation with controlled test compounds showed that organic compounds usually start evaporating from the filter when their melting point is reached. Isotopic fractionation occurs only if one temperature step is within a few degrees of the melting point of the substance, so that the substance only partially evaporates. However, this effect should be limited in an ambient sample containing thousands of individual chemical compounds. ?13C values of aerosol filter samples do not depend on the sample amount used, i.e. the system shows good linearity. The reproducibility depends somewhat on the sample amount and is usually < ± 0.3 ‰ for oven temperatures up to 200 °C and < ± 0.5 ‰ for oven temperatures greater than 200 °C. We analysed aerosol samples collected in a tunnel in Brazil (vehicular emissions), laboratory generated secondary organic aerosol (SOA) from alpha-pinene ozonolysis, and ambient filter samples from a regional site in the Netherlands, an urban site in Belgium, and Sao Paulo Brazil. First results show that ?13C ratios of SOA and vehicular emissions do not change strongly with oven temperature, i.e. the more refractory organic compounds have similar isotopic composition as the more volatile compounds. This is in contrast to the Dutch and Belgium ambient organic samples, where the more volatile compounds evaporating below 200°C are often depleted with respect to the refractory compounds by more than 2 permil. Ambient samples in Sao Paulo, Brazil however, are enriched in 13C compared to vehicular emissions that are the main source of urban pollutants. This indicates either an enriched background source for the aerosols or that the ambient aerosol has been strongly aged. Measurements at the Cabauw site show interesting differences between ?13C measured in polluted air masses and relatively clean air with marine air mass origin. In polluted, continental air masses ?13C is only weakly dependent on oven temperature, similar to the tunnel samples. In air masses with marine origin, organic compounds evaporating at low temperatures are strongly depleted in 13C. Possible reasons for the difference between source profiles and ambient samples (mixture of sources vs. the role of heterogeneous oxidation in the ambient filter samples vs. sampling artefacts) will be discussed and related to the chemical composition of the aerosol.

Dusek, Ulrike; Meusinger, Carl; Oyama, Beatriz; Holzinger, Rupert; Röckmann, Thomas

2014-05-01

35

Quantitative estimates of the volatility of ambient organic aerosol  

NASA Astrophysics Data System (ADS)

Measurements of the sensitivity of organic aerosol (OA, and its components) mass to changes in temperature were recently reported by Huffman et al.~(2009) using a tandem thermodenuder-aerosol mass spectrometer (TD-AMS) system in Mexico City and the Los Angeles area. Here, we use these measurements to derive quantitative estimates of aerosol volatility within the framework of absorptive partitioning theory using a kinetic model of aerosol evaporation in the TD. OA volatility distributions (or "basis-sets") are determined using several assumptions as to the enthalpy of vaporization (?Hvap). We present two definitions of "non-volatile OA," one being a global and one a local definition. Based on these definitions, our analysis indicates that a substantial fraction of the organic aerosol is comprised of non-volatile components that will not evaporate under any atmospheric conditions; on the order of 50-80% when the most realistic ?Hvap assumptions are considered. The sensitivity of the total OA mass to dilution and ambient changes in temperature has been assessed for the various ?Hvap assumptions. The temperature sensitivity is relatively independent of the particular ?Hvap assumptions whereas dilution sensitivity is found to be greatest for the low (?Hvap = 50 kJ/mol) and lowest for the high (?Hvap = 150 kJ/mol) assumptions. This difference arises from the high ?Hvap assumptions yielding volatility distributions with a greater fraction of non-volatile material than the low ?Hvap assumptions. If the observations are fit using a 1 or 2-component model the sensitivity of the OA to dilution is unrealistically high. An empirical method introduced by Faulhaber et al. (2009) has also been used to independently estimate a volatility distribution for the ambient OA and is found to give results consistent with the high and variable ?Hvap assumptions. Our results also show that the amount of semivolatile gas-phase organics in equilibrium with the OA could range from ~20% to 400% of the OA mass, with smaller values generally corresponding to the higher ?Hvap assumptions. The volatility of various OA components determined from factor analysis of AMS spectra has also been assessed. In general, it is found that the fraction of non-volatile material follows the pattern: biomass burning OA < hydrocarbon-like OA < semivolatile oxygenated OA < low-volatility oxygenated OA. Correspondingly, the sensitivity to dilution and the estimated amount of semivolatile gas-phase material for the OA factors follows the reverse order. Primary OA has a substantial semivolatile fraction, in agreement with previous results, while the non-volatile fraction appears to be dominated by oxygenated OA produced by atmospheric aging. The overall OA volatility is thus controlled by the relative contribution of each aerosol type to the total OA burden. Finally, the model/measurement comparison appears to require OA having an evaporation coefficient (?e) substantially greater than 10-2; at this point it is not possible to place firmer constraints on ?e based on the observations.

Cappa, C. D.; Jimenez, J. L.

2010-06-01

36

Quantitative estimates of the volatility of ambient organic aerosol  

NASA Astrophysics Data System (ADS)

Measurements of the sensitivity of organic aerosol (OA, and its components) mass to changes in temperature were recently reported by Huffman et al. (2009) using a tandem thermodenuder-aerosol mass spectrometer (TD-AMS) system in Mexico City and the Los Angeles area. Here, we use these measurements to derive quantitative estimates of aerosol volatility within the framework of absorptive partitioning theory using a kinetic model of aerosol evaporation in the TD. OA volatility distributions (or "basis-sets") are determined using several assumptions as to the enthalpy of vaporization (?Hvap). We present two definitions of "non-volatile OA," one being a global and one a local definition. Based on these definitions, our analysis indicates that a substantial fraction of the organic aerosol is comprised of non-volatile components that will not evaporate under any atmospheric conditions, on the order of 50-80% when the most realistic ?Hvap assumptions are considered. The sensitivity of the total OA mass to dilution and ambient changes in temperature has been assessed for the various ?Hvap assumptions. The temperature sensitivity is relatively independent of the particular ?Hvap assumptions whereas dilution sensitivity is found to be greatest for the low (?Hvap = 50 kJ/mol) and lowest for the high (?Hvap = 150 kJ/mol) assumptions. This difference arises from the high ?Hvap assumptions yielding volatility distributions with a greater fraction of non-volatile material than the low ?Hvap assumptions. If the observations are fit using a 1 or 2-component model the sensitivity of the OA to dilution is unrealistically high. An empirical method introduced by Faulhaber et al. (2009) has also been used to independently estimate a volatility distribution for the ambient OA and is found to give results consistent with the high and variable ?Hvap assumptions. Our results also show that the amount of semivolatile gas-phase organics in equilibrium with the OA could range from ~20% to 400% of the OA mass, with smaller values generally corresponding to the higher ?Hvap assumptions. The volatility of various OA components determined from factor analysis of AMS spectra has also been assessed. In general, it is found that the fraction of non-volatile material follows the pattern: biomass burning OA < hydrocarbon-like OA < semivolatile oxygenated OA < low-volatility oxygenated OA. Correspondingly, the sensitivity to dilution and the estimated amount of semivolatile gas-phase material for the OA factors follows the reverse order. Primary OA has a substantial semivolatile fraction, in agreement with previous results, while the non-volatile fraction appears to be dominated by oxygenated OA produced by atmospheric aging. The overall OA volatility is thus controlled by the relative contribution of each aerosol type to the total OA burden. Finally, the model/measurement comparison appears to require OA having an evaporation coefficient (?e) substantially greater than 10-2; at this point it is not possible to place firmer constraints on ?e based on the observations.

Cappa, C. D.; Jimenez, J. L.

2010-01-01

37

Bias in Filter-Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Ambient Measurements  

Microsoft Academic Search

During the 2006 Texas Air Quality Study\\/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS\\/GoMACCS 2006) a filter-based (Particle Soot Absorption Photometer, or PSAP) and a photoacoustic-based aerosol light absorption technique were deployed and here the data are compared. The level of agreement between the two techniques with ambient aerosol depended on the abundance of organic aerosol (OA), with the

Daniel A. Lack; Christopher D. Cappa; Tahllee Baynard; Paola Massoli; Berko Sierau; Timothy S. Bates; Patricia K. Quinn; Edward R. Lovejoy; A. R. Ravishankara

2008-01-01

38

Quantitative chemical analysis of ambient organic aerosols using high-resolution time-of-flight aerosol mass spectrometry  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols are important due to their effects on health, climate, visibility, and ecosystems. Organic aerosols (OA) comprise a large fraction of the submicron particle mass, yet their total composition, sources, and processing are not well understood. This thesis focuses on the composition and sources in order to improve the current state of knowledge on ambient OA. To analyze the composition of the total OA mass, a new elemental analysis (EA) technique for organic species (CHNO) was developed for use with the high-resolution Aerodyne Aerosol Mass Spectrometer (AMS). The method is calibrated with laboratory standards and enables fast on-line analysis (˜10 seconds) of OA from organic/inorganic mixtures. Additionally, the required sample size is reduced to ˜1 ng, approximately six orders of magnitude less than standard techniques. Elemental ratios for the total organic mass, i.e. oxygen/carbon (O/C), in addition to the organic mass to organic carbon ratio (OM/OC), are estimated with high precision (+/- 3% in the absence of air) but lower accuracy. The method is applied to both ambient and source aerosols, yielding similar results within the different OA types sampled. To characterize the sources of OA from within an urban Megacity, measurements were collected from a ground site within the Mexico City Metropolitan Area during the MILAGRO/MCMA-2006 field campaign. Standard AMS analyses, positive matrix factorization, elemental analysis, comparison with model output, and comparative analyses from different time periods, were applied to the data. The dominant OA sources identified were primary hydrocarbon-like, primary biomass burning, and secondary oxygenated OA, which were similar to source apportionment results from the chemical mass balance method using organic molecular markers. The oxygenated OA accounts for almost half of the OA on average. Biomass burning OA was heavily influenced by forest fires in the surrounding mountains, accounting for 15-23% of the OA on average, which is less than was identified in the air masses above the city. Overall, the forest fires are estimated to contribute 7-9% of the fine PM at T0 during MILAGRO and 2-3% of the fine PM as an annual average. In addition, carbon-14 analysis indicates a significant portion of the urban OA originates from modern carbon sources as has been reported for other urban locations. In summary, when compared to the 2004 Mexico City emissions inventory, the urban primary aerosol mass is underestimated by a factor of ˜3.5 (and it is ˜17x lower than afternoon concentrations when secondary species are included) and the wildfire contribution by a factor of ˜20.

Aiken, Allison Carol

39

Contribution of Woodsmoke and Motor Vehicle Emissions to Ambient Aerosol Mutagenicity (Journal Version).  

National Technical Information Service (NTIS)

Mutagenicity is frequently considered as a screening test for the carcinogenicity of compounds to which humans are exposed. Past estimates of the mutagenicity of ambient aerosol have depended on measurements of the mutagenic potency (refertants/microg) of...

C. W. Lewis R. E. Baumgardner R. K. Stevens L. D. Claxton J. Lewtas

1988-01-01

40

ANALYSIS OF RESPIRATORY DESPOSITION DOSE OF INHALED AMBIENT AEROSOLS FOR DIFFERENT SIZE FRACTIONS  

EPA Science Inventory

ANALYSIS OF RESPIRATORY DEPOSITION DOSE OF INHALED AMBIENT AEROSOLS FOR DIFFERENT SIZE FRACTIONS. Chong S. Kim, SC. Hu**, PA Jaques*, US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711; **IIT Research Institute, Chicago, IL; *S...

41

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED AMBIENT AEROSOLS FOR DIFFERENT DOSE METRICS  

EPA Science Inventory

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED AMBIENT AEROSOLS FOR DIFFERENT DOSE METRICS. Chong S. Kim, SC. Hu**, PA Jaques*, US EPA, National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711; **IIT Research Institute, Chicago, IL; *South...

42

Inhalation Exposure and Lung Dose Analysis of Multi-mode Complex Ambient Aerosols  

EPA Science Inventory

Rationale: Ambient aerosols are complex mixture of particles with different size, shape and chemical composition. Although they are known to cause health hazard, it is not fully understood about causal mechanisms and specific attributes of particles causing the effects. Internal ...

43

Combustion characteristics of water-insoluble elemental and organic carbon in size selected ambient aerosol particles  

NASA Astrophysics Data System (ADS)

Combustion of elemental carbon (EC) and organic carbon (OC) contained in ambient aerosol matter was explored using scanning electron microscopy (SEM) in combination with energy dispersive X-ray analysis (EDX). To ease identification of the particles of interest and to avoid or at least reduce interaction with simultaneously sampled inorganic oxides and salts, the approach used in this work differed in two ways from commonly applied procedures. First, rather than using a mixture of particles of vastly different sizes, as in PM10 or PM2.5, aerosol matter was collected in a 5-stage impactor. Second, the water soluble fraction of the collected matter was removed prior to analysis. Diesel soot particles, which appeared in the well-known form of chain-type aggregates, constituted the major fraction of EC. In contrast, OC containing particles were observed in a variety of shapes, including a sizable amount of bioaerosol matter appearing mostly in the size range above about 1 µm. During heating in ambient air for 1 h, diesel soot particles were found to be stable up to 480°C, but complete combustion occurred in a narrow temperature interval between about 490 and 510°C. After diesel soot combustion, minute quantities of ''ash'' were observed in the form of aggregated tiny particles with sizes less than 10 nm. These particles could be due to elemental or oxidic contaminants of diesel soot. Combustion of OC was observed over a wide range of temperatures, from well below 200°C to at least 500°C. Incompletely burnt bioaerosol matter was still found after heating to 600°C. The results imply that the EC fraction in aerosol matter can be overestimated significantly if the contribution of OC to a thermogram is not well separated.

Wittmaack, K.

2005-04-01

44

Combustion characteristics of water-insoluble elemental and organic carbon in size selected ambient aerosol particles  

NASA Astrophysics Data System (ADS)

Combustion of elemental carbon (EC) and organic carbon (OC) contained in ambient aerosol matter was explored using scanning electron microscopy (SEM) in combination with energy dispersive X-ray analysis (EDX). To ease identification of the particles of interest and to avoid or at least reduce interaction with simultaneously sampled inorganic oxides and salts, the approach used in this work differed in two ways from commonly applied procedures. First, rather than using a mixture of particles of vastly different sizes, as in PM10 or PM2.5, aerosol matter was collected in a 5-stage impactor. Second, the water soluble fraction of the collected matter was removed prior to analysis. Diesel soot particles, which appeared in the well-known form of chain-type aggregates, constituted the major fraction of EC. In contrast, OC containing particles were observed in a variety of shapes, including a sizable amount of bioaerosol matter appearing mostly in the size range above about 1 µm. During heating in ambient air for 1h, diesel soot particles were found to be stable up to 470°C, but complete combustion occurred in a narrow temperature interval between about 480 and 510°C. After diesel soot combustion, minute quantities of "ash" were observed in the form of aggregated tiny particles with sizes less than 10 nm. These particles could be due to elemental or oxidic contaminants of diesel soot. Combustion of OC was observed over a wide range of temperatures, from well below 200°C to at least 500°C. Incompletely burnt bioaerosol matter was still found after heating to 600°C. The results imply that the EC fraction in aerosol matter can be overestimated significantly if the contribution of OC to a thermogram is not well separated.

Wittmaack, K.

2005-07-01

45

Condensed Volcanic Aerosols Collected Near-Source at Poas  

Microsoft Academic Search

Volcanic plumes are mixtures of gases and liquids that react with air to form aerosols. In this study, atmospheric samples were collected near fumarolic vents at Poas Volcano inside the crater and 380m away on the crater rim. Aerosols were captured on supportive Cu grids coated by a thin C-film, encased within a sealed collector designed for this experiment. Grids

M. Pfeffer; F. Rietmeijer; A. Brearley; S. Basame; T. Fischer

2001-01-01

46

COLLECTION EFFICIENCY OF A PERSONAL SAMPLER FOR MICROBIOLOGICAL AEROSOLS  

Microsoft Academic Search

A modified personal impinger (MPI) for sampling airborne microorganisms was tested for collection efficiency with the jet nozzle placed at various positions above and below the liquid surface. The sampler was operated with 10?mL of water and sampling rates between 1.08 and 3.4?L\\/min. The collection efficiencies for a polydisperse aerosol of diethylhexyl phthalate (DEHP) and monodisperse aerosols of polystyrene latex

Ingrid Fängmark; Lars-Erik Wikström; Eva Welam Henningson

1991-01-01

47

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

NASA Astrophysics Data System (ADS)

Recently studies have shown that multivariate factor analysis of the highly time-resolved mass spectral data obtained with an Aerodyne Aerosol Mass Spectrometer (AMS) may allow the classification and simplification of complex organic aerosol (OA) mixtures into components that are chemically meaningful and can be related to different sources and transformation processes. Two factor analysis techniques, including the Multiple Component Analysis (MCA) method (Zhang et al., 2007) and the Positive Matrix Factorization (PMF) method (Paatero and Tapper, 1994), were applied to a Quadrupole-AMS dataset acquired from Chebogue Pt., Nova Scotia in summer 2004. Multiple OA components were determined, including a hydrocarbon-like OA (HOA) component similar in mass spectra to the hydrocarbon substances observed at urban locations and two oxygenated OA (OA) components that show different fragmentation patterns and oxygen-to-carbon ratios in their mass spectra. The HOA component correlates with inert primary emission tracers (e.g., EC and CO) and likely represents diluted POA transported from urban locations. The highly oxygenated component (OOA-I) correlates well with sulfate and shows a mass spectrum resembling that of fulvic acid - a model compound representative for highly processed/oxidized organics in the environment. The less oxygenated OA component (OOA-II) reveals a mass spectral pattern that compares well with those of the biogenic SOA produced from the mixture of VOCs emitted by spruce, pine and birch trees during exposure to ozone and UV-photolysis in the Jülich plant chamber. In addition, the time series of OOA-II correlates with biogenic SOA tracer compounds determined by the thermal desorption aerosol GC/MS-FID (TAG) instrument. Furthermore, the time-resolved size distributions of OOA components, their correlations with parallel gas and aerosol measurements, and backtrajectory analysis of air masses all support the association of OOA-II to biogenic sources. Finally, a case study will be presented to discuss the observation of a significant OA enhancement event likely dominated by biogenic SOA with a high-resolution AMS at Whistler Peak, Canada during Spring 2006. Comparisons will be made for the highly m/z-resolved mass spectra between this ambient OA and the biogenic SOA produced from the plant chamber experiments.

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

2008-12-01

48

The chemical characteristics of marine mineral aerosol solutions at ambient relative humidities and some effects on iron chemistry  

SciTech Connect

Iron could play a critical role as a limiting micronutrient in some ocean regions where the concentration of major nutrients is high but primary productively is low. Because aerosol iron is the predominant pathway to supply iron to the open oceans, this dissertation focuses on the factors that affect the iron solubility in aerosol particle before they enter the oceans. The thrust is the study of the mechanism of the interactions between aerosol iron and marine aerosol solutions while the particles are suspended in the marine atmosphere. Iron solubilities in marine aerosol solutions were estimated at the pH and ionic strength that are characteristic of ambient trade wind aerosol particles collected at Barbados. Under typical marine conditions, aerosol solutions could have very high ionic strength and extremely low pH even when part of the acid has been neutralized by NH[sub 3] and CaCO[sub 3]. The iron solubility in aerosol solutions is far higher than that expected for seawater and rainwater. Aerosol solution processes may be the major factor that determines how much iron will dissolve when particles enter the ocean. Iron photochemical and speciation studies indicated that about 1% of the total Fe and 7.5% of the soluble Fe in Barbados mineral aerosols was in the Fe(II) form. Although the presence of organic ligands such as oxalate can greatly increase the Fe(II) concentration during photolysis, Fe(II) levels dropped rapidly in the dark due to the oxidation of Fe(II) with H[sub 2]O[sub 2] that is also produced during irradiation. Geothite solubility studies suggested that photochemical processes affect only the soluble iron species and have no significant impact on the total iron solubility. Marine aerosol solutions are characterized by extreme conditions that can greatly affect the chemical processes that occur in the aerosol phase. The mobilization of iron and its fate in natural waters will be dependent on the history of the aerosol particles in the atmosphere.

Zhu, X.

1992-01-01

49

Formation of 2-methyl tetrols and 2-methylglyceric acid in secondary organic aerosol from laboratory irradiated isoprene\\/NO X \\/SO 2\\/air mixtures and their detection in ambient PM 2.5 samples collected in the eastern United States  

Microsoft Academic Search

Recent observations in ambient PM2.5 of 2-methylthreitol, 2-methylerythritol and 2-methylglyceric acid, proposed isoprene oxidation products, suggest the contribution of isoprene to SOA formation, long thought to be relatively unimportant, should be reexamined. To address this issue, an isoprene\\/NOX\\/air mixture was irradiated in a flow reactor smog chamber in both the absence and presence of SO2 to measure the SOA yield

E. O. Edney; T. E. Kleindienst; M. Jaoui; M. Lewandowski; J. H. Offenberg; W. Wang; M. Claeys

2005-01-01

50

Aerodynamic size associations of natural radioactivity with ambient aerosols  

SciTech Connect

The aerodynamic size of /sup 214/Pb, /sup 212/Pb, /sup 210/Pb, /sup 7/Be, /sup 32/P, /sup 35/S (as SO/sub 4//sup 2 -/), and stable SO/sub 4//sup 2 -/ was measured using cascade impactors. The activity distribution of /sup 212/Pb and /sup 214/Pb, measured by alpha spectroscopy, was largely associated with aerosols smaller than 0.52 ..mu..m. Based on 46 measurements, the activity median aerodynamic diameter of /sup 212/Pb averaged 0.13 ..mu..m (sigma/sub g/ = 2.97), while /sup 214/Pb averaged 0.16 ..mu..m (sigma/sub g/ = 2.86). The larger median size of /sup 214/Pb was attributed to ..cap alpha..-recoil depletion of smaller aerosols following decay of aerosol-associated /sup 218/Po. Subsequent /sup 214/Pb condensation on all aerosols effectively enriches larger aerosols. /sup 212/Pb does not undergo this recoil-driven redistribution. Low-pressure impactor measurements indicated that the mass median aerodynamic diameter of SO/sub 4//sup 2 -/ was about three times larger than the activity median diameter /sup 212/Pb, reflecting differences in atmospheric residence times as well as the differences in surface area and volume distributions of the atmospheric aerosol. Cosmogenic radionuclides, especially /sup 7/Be, were associated with smaller aerosols than SO/sub 4//sup 2 -/ regardless of season, while /sup 210/Pb distributions in summer measurements were similar to sulfate but smaller in winter measurements. Even considering recoil following /sup 214/Po ..cap alpha..-decay, the avervage /sup 210/Pb labeled aerosol grows by about a factor of two during its atmospheric lifetime. The presence of 5 to 10% of the /sup 7/Be on aerosols greater than 1 ..mu..m was indicative of post-condensation growth, probably either in the upper atmosphere or after mixing into the boundary layer.

Bondietti, E.A.; Papastefanou, C.; Rangarajan, C.

1986-04-01

51

Chemical characteristics of ambient aerosols contributed by cooking process at Noorpur village near Delhi (India)  

NASA Astrophysics Data System (ADS)

Combustion of fuels such as wood, crop residue and dung cakes etc. is one of the major sources of air pollution in developing countries. These fuels are still used commonly for cooking purpose in rural India. This study investigates the chemical composition of the ambient aerosols during cooking hours at a village called Noorpur (28.470 N, 77.030 E) which lies near Delhi city. Aerosol sampling was carried out during August 2011-May 2012 by using handy sampler (Envirotech model APM 821) installed at the terrace of a building (~6m). The samples were collected on 8 hourly basis using Teflon filters. The water extract of these filters was analyzed for major anions (F-, Cl-, NO3-, SO42-) and major cations (Na+, NH4+, K+, Ca2+ Mg2+) by ion chromatography (Metrohm 883 Basic IC Plus). Results highlighted that cooking process contributed significant amount of SO42- and K+.. Biomass burning is considered as a potential source of K+ in air. The high concentration of SO42- might be due to oxidation of SO2 contributed by the combustion of dung cakes. Further, the detailed results will be discussed during the conference.

Singh, Sudha; Kumar, Bablu; Gupta, Gyan Prakash; Kulshrestha, U. C.

2013-05-01

52

Single particle analysis of ambient aerosols in Shanghai during the World Exposition, 2010: two case studies  

Microsoft Academic Search

ATSI Model 3800 aerosol time-of-flight mass spectrometer (ATOFMS) was deployed for single-particle analysis in Shanghai during\\u000a the World Exposition (EXPO), 2010. Measurements on two extreme cases: polluted day (1st May) and clean day (25th September)\\u000a were compared to show how meteorological conditions affected the concentration and composition of ambient aerosols. Mass spectra\\u000a of 90496 and 50407 particles were analyzed respectively

Shikang Tao; Xinning Wang; Hong Chen; Xin Yang; Mei Li; Lei Li; Zhen Zhou

53

Temporal and spatial variation of morphological descriptors for atmospheric aerosols collected in Mexico City  

NASA Astrophysics Data System (ADS)

We present an analysis of morphological characteristics of atmospheric aerosol collected during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign that took place in Mexico City in March 2006. The sampler was installed on the Aerodyne mobile laboratory. The aerosol samples were collected on nuclepore clear polycarbonate filters mounted in Costar pop-top membrane holders. More than one hundred filters were collected at different ground sites with different atmospheric and geographical characteristics (urban, sub-urban, mountain-top, industrial, etc.) over a month period. Selected subsets of these filters were analyzed for aerosol morphology using a scanning electron microscope and image analysis techniques. In this study we investigate spatial and temporal variations of aerosol shape descriptors, morphological parameters, and fractal dimension. We also compare the morphological results with other aerosol measurements such as aerosol optical properties(scattering and absorption) and size distribution data. Atmospheric aerosols have different morphological characteristics depending on many parameters such as emission sources, atmospheric formation pathways, aging processes, and aerosol mixing state. The aerosol morphology influences aerosol chemical and mechanical interactions with the environment, physical properties, and radiative effects. In this study, ambient aerosol particles have been classified in different shape groups as spherical, irregularly shaped, and fractal-like aggregates. Different morphological parameters such as aspect ratio, roundness, feret diameter, etc. have been estimated for irregular shaped and spherical particles and for different kinds of soot particles including fresh soot, collapsed and coated soot. Fractal geometry and image processing have been used to obtain morphological characteristics of different soot particles. The number of monomers constituting each aggregate and their diameters were measured and used to estimate an ensemble three-dimensional (3-d) fractal dimension. One-dimensional (1-d) and two-dimensional (2-d) fractal geometries have been measured using a power-law scaling relationship between 1-d and 2-d properties of projected images. Temporal variations in fractal dimension of soot-like aggregates have been observed at the mountaintop site and spatial variation of fractal dimension and other morphological descriptors of different shaped particles have been investigated for the different ground sites.

China, S.; Mazzoleni, C.; Dubey, M. K.; Chakrabarty, R. K.; Moosmuller, H.; Onasch, T. B.; Herndon, S. C.

2010-12-01

54

Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw  

Microsoft Academic Search

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30-40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties - especially the aerosol light scattering - are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the

P. Zieger; E. Weingartner; J. Henzing; M. Moerman; G. de Leeuw; J. Mikkilä; M. Ehn; T. Petäjä; K. Clémer; M. van Roozendael; S. Yilmaz; U. Frieß; H. Irie; T. Wagner; R. Shaiganfar; S. Beirle; A. Apituley; K. Wilson; U. Baltensperger

2011-01-01

55

Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw  

Microsoft Academic Search

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30-40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, also their microphysical and optical properties - especially the aerosol light scattering - are strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the

P. Zieger; E. Weingartner; J. Henzing; M. Moerman; G. de Leeuw; J. Mikkilä; M. Ehn; T. Petäjä; K. Clémer; M. van Roozendael; S. Yilmaz; U. Frieß; H. Irie; T. Wagner; R. Shaiganfar; S. Beirle; A. Apituley; K. Wilson; U. Baltensperger

2010-01-01

56

Spatial variation and characterisation of ambient aerosols from domestic solid fuel burning in a New Zealand town  

Microsoft Academic Search

Here we present results of early trials of a car-borne mobile aerosol monitoring platform. The purpose of the platform is to map spatial variations of aerosols and to identify the relative contributions of different sources to the ambient aerosol. Ambient concentrations of PM10, PM2.5, PM1 and black carbon (BC) were measured in Alexandra (a town of 6,000 people in the

Gustavo Olivares; Jeff Smith; Jeff Bluett; Guy Coulson

57

CONTRIBUTION OF WOODSMOKE AND MOTOR VEHICLE EMISSIONS TO AMBIENT AEROSOL MUTAGENICITY (JOURNAL VERSION)  

EPA Science Inventory

Mutagenicity is frequently considered as a screening test for the carcinogenicity of compounds to which humans are exposed. Past estimates of the mutagenicity of ambient aerosol have depended on measurements of the mutagenic potency (refertants/microg) of the extractable organic ...

58

Tests of sampling systems for test aerosols in a dust channel and in ambient air. II  

Microsoft Academic Search

The paper reports on tests of filter devices, carried out in sampling systems by using flow of smoke, test aerosols, and ambient air, which showed that the horizontal elutriator in an optimal design was best suited for the measurement of the total respirate particulate matter. It is reported that systems that are equipped with a flow plate in front of

L. Laskus; D. Bake; L. Armbruster

1980-01-01

59

Composition and spectral characteristics of ambient aerosol at Mauna Loa Observatory  

SciTech Connect

Ambient aerosol particles were sampled continuously with a time resolution of {approximately}4 hours for a period of 8 days at the Mauna Loa Observatory, Hawaii, in August 1986. The samples were analyzed on-site for their chemical composition by attenuated total internal reflection infrared spectroscopy. The infrared absorption spectra of the samples also provided data on aerosol light absorbance characteristics at 9.1 and 10.6 {mu}m - wavelengths of interest in determining aerosol backscatter coefficients for CO{sub 2} lidars. The chemical species in the ambient aerosol varied considerably during this 8-day period. The aerosol was acidic ((NH{sub 4}){sub 3}H(SO{sub 4}){sub 2},NH{sub 4}HSO{sub 4}, or H{sub 2}SO{sub 4}) rather than neutral ((NH{sub 4}){sub 2}SO{sub 4}) for a major fraction of the sampling time. The samples generally showed much higher absorbance at 9.1 {mu}m than at 10.6 {mu}m. Changes in the chemical composition between (NH{sub 4}){sub 2}SO{sub 4} and the more acidic forms were accompanied by substantial changes in the sample's absorbance at 9.1 {mu}m but lesser changes in the absorbance at 10.6 {mu}m. These variations could have a profound effect on backscatter coefficients of atmospheric aerosol particles at CO{sub 2} wavelengths.

Johnson, S.A.; Kumar, R. (Argonne National Lab., IL (USA))

1991-03-20

60

Dependence of aerosol light absorption and single-scattering albedo on ambient relative humidity for sulfate aerosols with black carbon cores  

Microsoft Academic Search

Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of

Jens Redemann; Philip B. Russell; Patrick Hamill

2001-01-01

61

Portable Aerosol Contaminant Extractor  

DOEpatents

A compact, portable, aerosol contaminant extractor having ionization and collection sections through which ambient air may be drawn at a nominal rate so that aerosol particles ionized in the ionization section may be collected on charged plate in the collection section, the charged plate being readily removed for analyses of the particles collected thereon.

Carlson, Duane C. (N. Augusta, SC) [N. Augusta, SC; DeGange, John J. (Aiken, SC) [Aiken, SC; Cable-Dunlap, Paula (Waynesville, NC) [Waynesville, NC

2005-11-15

62

Elemental composition of urban aerosol collected in Debrecen, Hungary  

NASA Astrophysics Data System (ADS)

Aerosol samples have been collected in urban air by means of Nuclepore polycarbonate membrane filters from October 29, 1991 to October 17, 1994. Parallel sampling has been made from September 15, 1993 to October 17, 1994 with a stacked filter unit, too. The elemental composition of the samples was determined by PIXE. Yearly, winter and summer averages of elemental concentrations have been calculated together with enrichment factors. Principal components analysis has derived four factors, elemental source profiles and contributions of various sources.

Borbély-Kiss, I.; Koltay, E.; Szabó, Gy.

1996-04-01

63

Sampling and analysis methods for ambient PM-10 aerosol. Draft report  

SciTech Connect

This chapter provides information to design a measurement program to obtain ambient aerosol data for use in receptor models. Other chapters in the book show how receptor models are used in air-quality management and how species concentrations are used in receptor models. Methods are described for obtaining ambient PM-10 aerosol data for use in these receptor models. Characteristics of PM-10 sampling devices, filter media and laboratory analysis procedures are described. The latter included x-ray fluorescence, neutron activation, optical spectroscopy, pyrolysis, ion chromatography, and colorimetry. It is shown that some combinations of filter medium, sampler, and analysis method are incompatible, and information is presented so that incompatibility can be avoided. Measurement artifacts for ionic species and annular denuder systems for avoiding them are described.

Dzubay, T.G.; Stevens, R.K.

1989-08-21

64

Comparison of aerosol and bioaerosol collection on air filters.  

PubMed

Air filters efficiency is usually determined by non-biological test aerosols, such as potassium chloride particles, Arizona dust or di-ethyl-hexyl-sebacate (DEHS) oily liquid. This research was undertaken to asses, if application of non-biological aerosols reflects air filters capacity to collect particles of biological origin. The collection efficiency for non-biological aerosol was tested with the PALAS set and ISO Fine Test Dust. Flow rate during the filtration process was 720 l/h, and particles size ranged 0.246-17.165 ?m. The upstream and downstream concentration of the aerosol was measured with a laser particle counter PCS-2010. Tested bioaerosol contained 4 bacterial strains of different shape and size: Micrococcus luteus,Micrococcus varians, Pseudomonas putida and Bacillus subtilis. Number of the biological particles was estimated with a culture-based method. Results obtained with bioaerosol did not confirmed 100% filters efficiency noted for the mineral test dust of the same aerodynamic diameter. Maximum efficiency tested with bacterial cells was 99.8%. Additionally, cells reemission from filters into air was also studied. Bioaerosol contained 3 bacterial strains: Micrococcus varians, Pseudomonas putida and Bacillus subtilis. It was proved that the highest intensity of the reemission process was during the first 5 min. and reached maximum 0.63% of total number of bacteria retained in filters. Spherical cells adhered stronger to the filter fibres than cylindrical ones. It was concluded that non-biological aerosol containing particles of the same shape and surface characteristics (like DEHS spherical particles) can not give representative results for all particles present in the filtered air. PMID:22523449

Miaskiewicz-Peska, Ewa; Lebkowska, Maria

2012-06-01

65

Source apportionment of ambient aerosol applying PMF on AMS mobile and stationary data  

NASA Astrophysics Data System (ADS)

Ambient aerosols are divided into the categories "primary" and "secondary", referring to particles directly emitted into the air, or formed out of precursor species such as volatile organic compounds, respectively. Main sources for primary urban aerosol and precursor species are traffic emissions, but also wood burning for domestic heating purposes especially in winter time (Alfarra et al., 2007). The quantification of various types of aerosol components is important for source identification which in turn is the basis of all mitigation activities. Positive Matrix Factorization (PMF) is a statistical based source apportionment tool that uses constrained, weighted least squares estimation to determine source profiles and strengths. PMF has been applied recently for the first time on highly time resolved organic mass spectra (Lanz et al., 2007) measured by an Aerodyne aerosol mass spectrometer (AMS) (Canagaratna et al., 2007). For the data presented here, two AMS were deployed together with additional instrumentation in the metropolitan area of Zurich in winter 2007/2008. The high-resolution time-of-flight AMS was stationed at an urban background site in the center, 30 meters from and shielded against direct traffic emissions. The quadrupole-based AMS was deployed in a mobile van allowing for on-road submicron aerosol composition measurements, and investigations into the spatial variability of aerosol concentration and composition. Results indicate that traffic emissions are the main contributor to submicron aerosol concentrations measured on-road. Hydrocarbon-like organic aerosol (HOA), a marker for traffic emissions (Lanz et al. 2007), dominates the primary aerosol mass, together with black carbon (BC). BC was monitored with the MAAP (multi angle absorption photometer). Another significant contributor to primary organic aerosol mass in downtown Zurich is domestic wood burning for heating purposes. Traffic and wood burning emissions make up roughly 50% of the total organic mass. Oxygenated organic aerosol (OOA), most of which is secondary, represents the remaining fraction. At the background site, the measured aerosol composition is more strongly influenced by secondary species, since this site is less exposed to primary emissions. The relative OOA contribution is higher than on-road, as well are particulate sulphate, nitrate, and ammonium contributions. Calculations of particulate sulphate ratios suggest that differences in absolute background and on-road concentration levels are mostly due to meteorological transport processes, but local emissions play a major role. Additional PMF analysis of AMS data from other regions and recent mobile AMS measurements will also be presented. Alfarra, M. R., et al. (2007). Environ. Sci. Technol., 41: 5770 - 5777. Canagaratna, M. R., et al. (2007). Mass Spectrom. Rev. , 26: 185-222. Lanz, V. A., et al. (2007). Atmos. Chem. Phys., 7: 1503-1522.

Mohr, C.; Weimer, S.; Richter, R.; Decarlo, P. F.; Chirico, R.; Heringa, M. F.; Prévôt, A. S. H.; Baltensperger, U.

2009-04-01

66

Levoglucosan enhancement in ambient aerosol during springtime transport events of biomass burning smoke to Southeast China  

Microsoft Academic Search

An intensive field experiment was conducted at an urban and a rural site in Hong Kong to identify the influence of biomass burning emissions transported from distinct regions on ambient aerosol in coastal southeast China. Water-soluble ionic and carbonaceous species, specifically the biomass burning tracer levoglucosan, were analysed. Elevated levoglucosan concentrations with maxima of 91.5 and 133.7 ng m-3 and

Xue-Fang Sang; Chuen-Yu Chan; Guenter Engling; Lo-Yin Chan; Xue-Mei Wang; Yi-Nan Zhang; Si Shi; Zhi-Sheng Zhang; Ting Zhang; Ming Hu

2011-01-01

67

Estimating the toxicity of ambient fine aerosols using freshwater rotifer Brachionus calyciflorus (Rotifera: Monogononta).  

PubMed

The toxicity of atmospheric fine particulate matter (PM2.5) in Atlanta is assessed using freshwater rotifers (Brachionus calyciflorus). The PM-laden quartz filters were extracted in both water and methanol. Aerosol extracts were passed through a C-18 column to separate the PM components into hydrophobic and hydrophilic fractions. Toxicity data reported in the units of LC50 (concentration that kills 50% of the test population in 24 h) shows that ambient particles are toxic to the rotifers with LC50 values ranging from 5 to 400 ?g of PM. The methanol extract of the aerosols was substantially more toxic (8 ± 6 times) to the rotifers compared to the water extracts. A sizeable fraction (>70%) of toxicity was found to be associated with the hydrophobic fraction of PM. However, none of the bulk aerosol species was strongly correlated with the LC50 values suggesting a complicated mechanism of toxicity probably involving synergistic interactions of various PM components. PMID:23981648

Verma, Vishal; Rico-Martinez, Roberto; Kotra, Neel; Rennolds, Corey; Liu, Jiumeng; Snell, Terry W; Weber, Rodney J

2013-11-01

68

Characterization of ambient aerosols at the San Francisco International Airport using BioAerosol Mass Spectrometry  

SciTech Connect

The BioAerosol Mass Spectrometry (BAMS) system is a rapidly fieldable, fully autonomous instrument that can perform correlated measurements of multiple orthogonal properties of individual aerosol particles. The BAMS front end uses optical techniques to nondestructively measure a particle's aerodynamic diameter and fluorescence properties. Fluorescence can be excited at 266nm or 355nm and is detected in two broad wavelength bands. Individual particles with appropriate size and fluorescence properties can then be analyzed more thoroughly in a dual-polarity time-of-flight mass spectrometer. Over the course of two deployments to the San Francisco International Airport, more than 6.5 million individual aerosol particles were fully analyzed by the system. Analysis of the resulting data has provided a number of important insights relevant to rapid bioaerosol detection, which are described here.

Steele, P T; McJimpsey, E L; Coffee, K R; Fergenson, D P; Riot, V J; Tobias, H J; Woods, B W; Gard, E E; Frank, M

2006-03-16

69

Ambient Aerosol in Southeast Asia: High Resolution Aerosol Mass Spectrometer Measurements Over Oil Palm (Elaeis guineensis)  

NASA Astrophysics Data System (ADS)

The emission of organic compounds in the troposphere is important factor in the formation of secondary organic aerosol (SOA). A very large proportion of organic material emitted globally is estimated to arise from biogenic sources, with almost half coming from tropical and sub-tropical forests. Preliminary analyses of leave cuvette emission studies suggest that oil palm (Elaeis guineensis) is a significantly larger source of isoprene than tropical forest. Much larger sources of isoprene over oil palm allied with a larger anthropogenic component of local emissions contrast greatly with the remote tropical forest environment and therefore the character of SOA formed may differ significantly. These issues, allied with the high price of palm oil on international markets leading to increased use of land for oil palm production, could give rise to rapidly changing chemical and aerosol regimes in the tropics. It is therefore important to understand the current emissions and composition of organic aerosol over all important land-uses in the tropical environment. This in turn will lead to a greater understanding of the present, and to an improvement in predictive capacity for the future system. To help address these issues, a high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) was deployed in the Sabahmas (PPB OIL) oil palm plantation near Lahad Datu, in Eastern Sabah, as part of the field component of the Aerosol Coupling in the Earth System (ACES) project, part of the UK NERC APPRAISE program. This project was allied closely with measurements made of similar chemical species and aerosol components at a forest site in the Danum Valley as part of the UK Oxidant and Particle Photochemical Processes above a Southeast Asian tropical rainforest (OP3) project. Measurements of submicron non- refractory aerosol composition are presented along with some preliminary analysis of chemically resolved aerosol fluxes made with a new eddy covariance system, based on the HR-ToF-AMS. The measurements are interpreted in the context of the measurements over tropical rain forest at Danum and aircraft measurements across Sabah.

Phillips, G.; Dimarco, C.; Misztal, P.; Nemitz, E.; Farmer, D.; Kimmel, J.; Jimenez, J.

2008-12-01

70

Atmospheric 210Pb and 7Be in ambient aerosols over low- and high-altitude sites in semiarid region: Temporal variability and transport processes  

Microsoft Academic Search

Time series measurements of 210Pb and 7Be made on ambient aerosols, collected from a low-altitude urban site (Ahmedabad, 23.0°N, 72.6°E, 49 m asl) and a high-altitude station (Mt. Abu, 24.6°N, 72.7°E, 1680 m asl) located in a high-dust semiarid region of western India, reveal characteristic pattern of temporal variability consistent over three years (2000–2002). The relatively high concentrations of 210Pb

N. Rastogi; M. M. Sarin

2008-01-01

71

Contribution of Woodsmoke and Motor Vehicle Emissions to Ambient Aerosol Mutagenicity.  

National Technical Information Service (NTIS)

A receptor model analysis of the mutagenicity of ambient fine particles in air samples collected under EPA's Integrated Air Cancer Project has been performed. The analysis was based on multiple linear regression, using measured concentrations of inorganic...

C. W. Lewis R. E. Baumgardner R. K. Stevens L. D. Claxton J. Lewtas

1988-01-01

72

Aerosol Interfaces Examined with Ambient Pressure Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

Heterogeneous chemistry occurring at the liquid/vapor and solid/vapor interfaces plays a significant role in environmental and atmospheric chemistry. Despite the importance of understanding differences in chemical reactivity between surface and bulk solutions, there is a considerable lack of quantitative and chemically specific techniques that can operate under environmental and atmospherically relevant conditions. The significance of these interfacial types of measurements is becoming increasingly apparent. For example, recent studies have shown that ions can segregate to the surface in liquid salt solutions, changing the chemical reactivity of the liquid at its interface. Recent development of the ambient pressure photoelectron spectroscopy (APPES) facilitates chemical identification of molecules adsorbed onto liquid and solid surfaces at atmospherically relevant pressures. The specific advantage of this technique is that measurements can be made at pressures greater than 5 Torr, i.e. above the equilibrium vapor pressure of water at its triple point. Here, we describe the development of a novel synchrotron-based instrument that combines APPES with real-time droplet and nanoparticle surface analysis. Three experiments that address chemistry of model systems are presented: (a) the adsorption and chemical reaction of an atmospherically relevant polycyclic aromatic hydrocarbon (PAH) compound on model surfaces (b) a combined droplet train/APPES setup for the investigation of the liquid/vapor interface and (c) a particle flow reactor for the investigation of heterogeneous chemistry on liquid and solid nanoparticle surfaces. Initial results of the surface composition of methanol/water mixtures in the droplet train and oxidation of the PAH coronene by ozone on a model surface will be presented.

Mysak, E. R.; Starr, D. E.; Wilson, K. R.; Bluhm, H.

2007-12-01

73

Aerosol Optical Properties and Black Carbon Measurements (Ambient and Thermally-Denuded) from Detling, UK During the ClearfLo IOP in Winter 2012  

NASA Astrophysics Data System (ADS)

Continuous direct online aerosol and trace gas measurements were made in Delting, UK over the course of four weeks during the winter of 2012 as a part of the ClearfLo (Clean Air for London) campaign. Aerosols were sampled from the London plume (~33 miles WNW), fresh highway (~0.15 mi and 1.5 mi S, A249 and M20), urban (Maidstone; ~3 mi SW), power station (~8 mi N), and Continental European outflow (~50+ mi E/SE). LANL measurements include aerosol absorption and scattering at four wavelengths (375, 405, 532, 781 nm; PASS), aerosol extinction at 450 nm (CAPS), single particle black carbon (BC) number and mass concentrations (SP2), aerosol size distributions (LAS and SMPS), ambient and thermally-denuded aerosol filter samples for SEM and EDS analysis, PM10 C-13 aerosol filter samples, gas-phase CO2, H2O, and CH4 (Picarro). The SP2, PASS, and CAPS were located behind a valve-switching set-up to enable ambient and thermally-denuded (TD) samples to be collected at 10 minute intervals during the campaign, cycling between four temperature settings of 50, 120, 180, and 250C. Absorption from organics and coatings on BC are characterized by comparing the ambient data with the TD samples for the different aerosol sources that were sampled. Measurements from the SP2 are combined with absorption measurements from the three-wavelength photoacoustic soot spectrometer (PASS-3) at 405, 532, and 781 nm to determine wavelength-dependent mass absorption coefficients (MACs) and absorption angstrom exponents (AAEs). Extinction measurements from the CAPS compare well with the PASS using extinction angstrom exponents calculated from the PASS. BC increases with CO/CO2, a marker for inefficient combustion. We examine the mixing state of BC in the aged aerosol plumes by using the time lag between the scattering and incandescence signals measured by the SP2 and SEM analysis as a function of denuding temperature. The Detling/ClearfLo dataset is one of the most comprehensive in situ sets of aerosol optical properties to date in terms of the aerosol sources sampled and the number of measurements.

Gorkowski, K.; Aiken, A. C.; Dubey, M. K.; Herndon, S. C.; Williams, L. R.; Worsnop, D. R.; Massoli, P.; Fortner, E.; Freedman, A.; Ng, N. L.; Allan, J. D.

2012-12-01

74

Online Measurements of Water-Soluble Iron in Ambient Aerosols: A new Technique  

NASA Astrophysics Data System (ADS)

Water-soluble iron, i.e. Fe(II) (hereafter, WS-Fe), is a redox active metal that can act as a catalyst in the production of reactive oxygen species (ROS). In atmospheric aerosol particles, WS-Fe may significantly impact human health and the atmospheric oxidative capacity. Further, WS-Fe acts as a critical nutrient for marine organisms and has been hypothesized to limit phytoplankton productivity in high nitrate, low-chlorophyll ocean regions. In order to assess the role of aerosol WS-Fe on human health, atmospheric chemistry and ocean biogeochemistry, it is necessary to understand its major sources, transport, transformation processes and sinks. Filter-based measurements with several (6-24) hours integration time are predominately used to quantify WS-Fe in aerosols but provide limited insight into acute exposures that could be higher than daily averages, or sources having high temporal variability. Generally, mineral dust and its processing with acidic pollutants, is considered the dominant source of WS-Fe, however, recent studies have reported combustion emissions are also a possible source. A time-resolved data set may help in identifying WS-Fe sources, atmospheric transformations and possible sinks. We have developed a new system for online quantitative analyses of WS-Fe present in ambient aerosols with a 12-minute integration time. It mainly consists of Particle-Into-Liquid Sampler (PILS), a liquid waveguide capillary cell (LWCC) and a portable UV-Visible spectrophotometer. The complete system is automated so that first the liquid sample (water-extract of ambient aerosols from PILS) is mixed with ferrozine (complexing reagent) by pumping them simultaneously (10:1) through a serpentine reactor and a 100 turn mixing coil using a peristaltic pump. After holding the mixed solution in the mixing coil for three minutes, the sample is pumped through the LWCC and held there for two minutes to acquire the absorbance of the solution at 562 nm (for Fe(II)-ferrozine complex) and 700 nm (background). The difference in absorbance units (AU562-AU700) is used to quantify the WS-Fe concentration in the liquid sample and thus in ambient aerosols. This prototype was successfully used to measure WS-Fe in aerosols at urban sites in Atlanta during November- December, 2007 and Detroit during January-February, 2008. Preliminary results from these studies will be presented, along with data from a single particle mass spectrometer (ATOFS) and hourly-averaged fine particle Elemental and Organic Carbon (EC and OC).

Rastogi, N.; Oakes, M.; Weber, R. J.; Majestic, B. J.; Shafer, M. M.; Snyder, D. C.; Schauer, J. J.

2008-05-01

75

Structural characterization of 2-hydroxyterpenylic acid, an abundant oxygenated marker compound for ?-pinene secondary organic aerosol in ambient fine aerosol  

NASA Astrophysics Data System (ADS)

A highly hydrophilic and oxygenated MW 188 compound is commonly observed in substantial abundance in atmospheric aerosol samples and was proposed in previous studies as an ?-pinene-related marker compound that is associated with ageing processes (1). Paradoxically, the MW 188 compound is usually observed at low abundance in chamber-generated ?-pinene-secondary organic aerosol (SOA) (2), pointing to a non-achievement in crucial reaction conditions. Furthermore, the occurrence of several isobaric isomers did not lead to a complete assignment for individual MW 188 compounds from laboratory generated SOA samples in former studies. For the most abundant MW 188 compound two structures have been proposed, i.e., a C8-monohydroxycarboxylic acid structure (2-hydroxyterpenylic acid) (3), and a C8-hydroxydicarboxylic acid structure (hydroxynorpinic acid) (4). Results will be presented here from a comprehensive mass spectrometric analysis of the most abundant MW 188 compound as 2-hydroxyterpenylic acid. The application of liquid chromatographic/electrospray ionization - ion trap mass spectrometry in both negative and positive ion modes in combination with collision-induced dissociation, as well as the utilisation of a soft derivatisation technique followed by analysis of the formed methyl ester derivatives using the latter technique and gas chromatography/electron ionization mass spectrometry enabled a comprehensive characterization of MW 188 isomers. Theoretical calculations were performed to support the assignment of 2-hydroxyterpenylic acid diastereoisomers. In addition, a positional isomer of 2-hydroxyterpenylic acid, the 4-hydroxyterpenylic acid, was tentatively identified, which is also of atmospheric relevance as it could be detected in ambient fine aerosol. Results from a time-resolved ?-pinene photooxidation experiment do not support that the 2 hydroxyterpenylic acid is a marker compound for aged SOA. Compared to terpenylic acid it should rather be regarded as a higher-generation product of the ?-pinene oxidation cascade. This study presents a comprehensive chemical data set for a more complete structural characterization of hydroxyterpenylic acids in ambient fine aerosol, which sets the foundation to better understand the atmospheric fate of ?-pinene in future studies. This work was supported by the Belgian Federal Science Policy Office through the network project "Biogenic Influence on Oxidants and Secondary Organic Aerosol: theoretical, laboratory and modeling investigations (BIOSOA)", the Research Foundation - Flanders (FWO), and the European Commission through the EUROCHAMP-2 project (228335). References: (1) Gómez-González et al., Atmos. Chem. Phys, 2012, 12, (1), 125-138. (2) Vogel et al., Atmos. Chem. Phys. Discuss., 2013, 13, (7), 17901-17952. (3) Claeys et al., Environ. Sci. & Technol., 2009, 43, (18), 6976-6982. (4) Yasmeen et al., J. Mass Spectrom., 2011, 46, (4), 425-442.

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

2014-05-01

76

Temporal variability in Chemical and Stable isotopic characteristics of ambient bulk aerosols over a coastal environment of India  

NASA Astrophysics Data System (ADS)

Atmospheric carbonaceous aerosols are known to influence regional biogeochemical cycles of carbon (C) and nitrogen (N) in addition to regional radiation budgets. Owing to multiplicity of primary sources of natural and anthropogenic origin, their detailed chemical and isotopic characterization can greatly help in source apportionment and identifying secondary processes. From the roof of NIO-Goa (India) [15.46?N, 73.8oE; at ~55.8 MASL], atmospheric bulk aerosols (n=22) were collected on Quartz filters, from 2009 December to January 2011 covering entire 2010 (except monsoon period) to investigate temporal variability in their chemical and isotopic characteristics of the carbonaceous fraction i.e. TC, TOC and TN mass concentrations and their stable isotopic ratios (?13CTC, ?13CTOC and ?15NTN). Both ?13CTC and ?13CTOC varied in narrow ranges (-24.9±1.1‰, -25.7±0.9‰ respectively), but significant differences were observed between the two during pre-monsoon months (as high as 2.3‰), possibly due to mixing of inorganic mineral dust. ?15NTN values showed a wide range of variability (average = 13.6±7.2‰), with significantly lower values (~2-5‰; as reported earlier by Agnihotri et al. 2011) during pre-monsoon period compared to those during winter (as high as ~26‰). Using ?13CTC values and two end-member mixing model (assuming ?13C of marine and continental carbon as -21 and -27‰ respectively), the average marine carbon fraction for Goa aerosols was estimated as 36±18.5%, significantly higher than reported for Chennai aerosols (~19%) (Pavuluri et al., 2011), but close to the reported average for marine aerosols at Bermuda (38%) (Turekian et al., 2003). Chemical and isotopic characteristics of ambient aerosols over Goa along with contemporaneous meteorological data indicate that winter aerosols contain significant proportion of carbonaceous fraction originated from biomass burning and other anthropogenic activities carried out in northern parts of India, while local marine sources and mineral dust appear to dominate chemical composition of aerosols during pre-monsoon period. References: Agnihotri, R., Mandal, T. K., Karapurkar, S., Naja, M., Gadi, R., Ahammed, Y. N., Kumar, A., Saud, T., and Saxena, M. (2011) Stable carbon and nitrogen isotopic composition of bulk aerosols over India and Northern Indian Ocean, Atmos. Environ., 45, 2828-2835, 2011 Pavuluri, C. M., K. Kawamura, T. Swaminathan, and E. Tachibana (2011), Stable carbon isotopic compositions of total carbon, dicarboxylic acids and glyoxylic acid in the tropical Indian aerosols: Implications for sources and photochemical processing of organic aerosols, J. Geophys. Res., 116, D18307, doi:10.1029/2011JD015617 Turekian, V. C., S. A. Macko, and W. C. Keene (2003), Concentrations, isotopic compositions, and sources of size-resolved, particulate organic carbon and oxalate in near-surface marine air at Bermuda during spring, J. Geophys. Res., 108, 4157, doi:10.1029/2002JD002053

Agnihotri, R.; Karapurkar, S. G.; Sarma, V. V.; Praveen, P.; Kumar, M. D.

2012-12-01

77

Particle detection efficiencies of aerosol time of flight mass spectrometers under ambient sampling conditions  

SciTech Connect

Aerosol time-of-flight mass spectrometers (ATOFMS) measure the size and chemical composition of single aerosol particles. To date, these instruments have provided qualitative descriptions of aerosols, in part because the fraction of particles actually present in the atmosphere that is detected by these instruments has not been known. in this work, the particle detection efficiencies of three ATOFMS instruments are determined under ambient sampling conditions from the results of colocated sampling with more conventional reference samplers at three locations in southern California. ATOFMS particle detection efficiencies display a power law dependence on particle aerodynamic diameter (D{sub a}) over a calibration range of 0.32 < D{sub a} < 1.8 microns. Detection efficiencies are determined by comparison of ATOFMS data with inertial impactor data and are compared to detection efficiencies determined independently by the use of laser optical particle counters. Detection efficiencies are highest for the largest particles and decline by approximately 2 orders of magnitude for the smallest particles, depending on the ATOFMS design. Calibration functions are developed here and applied to scale ATOFMS data to yield continuous aerosol mass concentrations as a function of particle size over an extended period of time.

Allen, J.O.; Fergenson, D.P.; Gard, E.E. [and others] [and others

2000-01-01

78

Stable carbon isotope ratio analysis of biomass burning tracers in ambient aerosol  

NASA Astrophysics Data System (ADS)

Due to the potential to fingerprint emissions as well as chemical and physical processes in the atmosphere, stable isotopes are considered as a promising tool to improve our understanding of sources and atmospheric fate of organic aerosol. In this study, compound specific isotopic measurements of levoglucosan by employing Thermal Desorption - Two Dimensional Gas Chromatography - Isotopic Ratio Mass Spectrometry (TD-2DGC-IRMS) are presented for ambient aerosol sampled during biomass burning episodes at rural, suburban and urban sites in Guangdong province, China. Further, information on the origin and pathways of the probed air masses is given, based on back trajectories calculated with the Lagrangian particle dispersion model FLEXPART from ECMWF meteorological data. The results combining observed ?13C for levoglucosan with back trajectory analyses will be discussed in relation to the potential of using compound specific ?13C measurements for improved source apportionment and determining the photochemical age of organic molecular markers.

Gensch, Iulia; Sang, Xuefang; Laumer, Werner; Chan, ChuenY; Engling, Guenter; Kiendler-Scharr, Astrid

2014-05-01

79

Acute lung function responses to ambient acid aerosol exposures in children  

SciTech Connect

We examined the relationship between lung function changes and ambient acid aerosol episodes in children attending a residential summer camp. Young females (112) performed daily spirometry, and 96 were assessed on one occasion for airway hyperresponsiveness using a methacholine bronchoprovocation test. Air quality measurements were performed on site and four distinct acid aerosol episodes were observed during the 41-day study. The maximum values observed during the 41-day study were: O/sub 3/ at 143 ppb; H/sub 2/SO/sub 4/ at 47.7 micrograms/m/sup 3/; and (H+) at 550 nmole/m/sup 3/. Maximum decrements of 3.5 and 7% for FEV1 and PEF, respectively, were observed to be associated with the air pollution episodes. There was some evidence of a differential lung function response to the episodes where children with a positive response to a methacholine challenge had larger decrements compared to their nonresponsive counterparts.

Raizenne, M.E.; Burnett, R.T.; Stern, B.; Franklin, C.A.; Spengler, J.D.

1989-02-01

80

A molecular-level approach for characterizing water-insoluble components of ambient organic aerosol particulates using ultra-high resolution mass spectrometry  

NASA Astrophysics Data System (ADS)

The chemical composition of organic aerosols in the atmosphere is strongly influenced by human emissions, and the effect these have on the environment, human health, and climate change is determined by the molecular nature of these chemical species. The complexity of organic aerosol samples limits the ability to study the chemical composition, and, therefore, the associated properties and the impacts they have. Many studies address the water-soluble fraction of organic aerosols, and have had much success in identifying specific molecular formulas for thousands of compounds present. However, little attention is given to the water-insoluble portion, which can contain most of the fossil material that is emitted through human activity. Here we compare the organic aerosols present in water extracts and organic solvent extracts (pyridine and acetonitrile) of an ambient aerosol sample collected in a rural location that is impacted by natural and anthropogenic emission sources. A semi-quantitative method was developed using proton nuclear magnetic resonance spectroscopy to determine that the amount of organic matter extracted by pyridine is comparable to that of water. Electrospray ionization Fourier transform ion cyclotron resonance mass spectra show that pyridine extracts a molecularly unique fraction of organic matter compared to water or acetonitrile, which extract chemically similar organic matter components. The molecular formulas unique to pyridine were less polar, more aliphatic, and reveal formulas containing sulfur to be an important component of insoluble aerosol organic matter.

Willoughby, A. S.; Wozniak, A. S.; Hatcher, P. G.

2014-04-01

81

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols  

SciTech Connect

We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM{sub 2.5} and PM{sub 10} (particulate matter with aerodynamic diameters less than 2.5 {mu}m and 10 {mu}m, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO{sub 2}). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Angstrom exponent of absorption (AEA), and Angstrom exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.

Gyawali, Madhu S.; Arnott, W. Patrick; Zaveri, Rahul A.; Song, Chen; Moosmuller, H.; Liu, Li; Mishchenko, M.; Chen, L-W A.; Green, M.; Watson, J. G.; Chow, J. C.

2012-03-08

82

Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region  

NASA Astrophysics Data System (ADS)

airborne study of cloud microphysics provided an opportunity to collect aerosol particles in ambient and updraft conditions of natural convection systems for transmission electron microscopy (TEM). Particles were collected simultaneously on lacey carbon and calcium-coated carbon (Ca-C) TEM grids, providing information on particle morphology and chemistry and a unique record of the particle's physical state on impact. In total, 22 particle categories were identified, including single, coated, aggregate, and droplet types. The fine fraction comprised up to 90% mixed cation sulfate (MCS) droplets, while the coarse fraction comprised up to 80% mineral-containing aggregates. Insoluble (dry), partially soluble (wet), and fully soluble particles (droplets) were recorded on Ca-C grids. Dry particles were typically silicate grains; wet particles were mineral aggregates with chloride, nitrate, or sulfate components; and droplets were mainly aqueous NaCl and MCS. Higher numbers of droplets were present in updrafts (80% relative humidity (RH)) compared with ambient conditions (60% RH), and almost all particles activated at cloud base (100% RH). Greatest changes in size and shape were observed in NaCl-containing aggregates (>0.3 µm diameter) along updraft trajectories. Their abundance was associated with high numbers of cloud condensation nuclei (CCN) and cloud droplets, as well as large droplet sizes in updrafts. Thus, compositional dependence was observed in activation behavior recorded for coarse and fine fractions. Soluble salts from local pollution and natural sources clearly affected aerosol-cloud interactions, enhancing the spectrum of particles forming CCN and by forming giant CCN from aggregates, thus, making cloud seeding with hygroscopic flares ineffective in this region.

Semeniuk, T. A.; Bruintjes, R. T.; Salazar, V.; Breed, D. W.; Jensen, T. L.; Buseck, P. R.

2014-03-01

83

Secondary Organic Aerosol Formation from the Photooxidation of Complex Hydrocarbon Mixtures: Composition, effect of SO2, and Relevance to Ambient Aerosol  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) formation from single hydrocarbon precursors is commonly studied in smog chamber experiments to obtain SOA yield and organic composition data. However, very few complex air mixture experiments have been conducted to simulate possible conditions in ambient atmospheres. A six-phase experiment involving various combinations of alpha-pinene, toluene, isoprene, and SO2 were irradiated in the EPA's dynamic smog chamber at the National Exposure Research Laboratory in Raleigh, NC. Glass fiber filters and impactor plates were collected for each phase of the experiment to identify and quantify the nature of the SOA composition. The following suite of analytical techniques analyzed the resultant polar organic compounds and the high molecular weight species: liquid chromatography-electrospray ionization (ESI)-mass spectrometry, gas chromatography-mass spectrometry, ESI-ion trap mass spectrometry, matrix assisted laser desorption (MALDI)-time of flight mass spectrometry, and high-resolution mass spectrometry. When SO2 is present in the chamber, increases in the gravimetric aerosol mass concentration and in the abundance of polar organic compounds are observed, likely suggesting an acid catalysis effect stemming from the conversion of SO2 to H2SO4 that condenses onto aerosol formed. The addition of isoprene to a alpha-pinene/toluene mixture is found to lower the amount of aerosol produced and is also found to lower the abundance of organic compounds identified by the various analytical techniques. Lastly, many of the polar organic compounds identified and quantified here are also seen in the Southeastern Aerosol Research and Characterization (SEARCH) network during the summer of 2004. In particular, a sulfur and nitrogen containing organic species (MW = 295 gmol) is found to be the most abundant polar organic species identified in this field study (~28 % on average of the total identified organic mass). This species is also detected in the chamber experiment only when alpha-pinene and SO2 are both present in the chamber, suggesting that this abundant species is likely formed from monoterpene photooxidation. High-resolution mass spectrometry suggests the molecular formula for this species is C10H16NO7S.

Surratt, J. D.; Gao, S.; Knipping, E.; Edgerton, E.; Shahgoli, M.; Seinfeld, J. H.; Edney, E.; Kleindiesnt, T.; Lewandowski, M.; Offenberg, J.; Jaoui, M.

2005-12-01

84

Characterization of ambient aerosol at a remote site and twin cities of Pakistan  

NASA Astrophysics Data System (ADS)

The pollution controls have significantly decreased pollutant concentrations in the industrialized nations in the west while the concentrations are expected to grow in developing countries. In this study the concentrations of major ions i.e SO4 2 -, NO3 -, NO2 -, Cl- , NH4 + and trace metals i.e. Al, V, Cr, Mn, Cu, As, Se, Cd, Sb, Ba, Ti and Pb were determined in aerosols at a remote site of Northern Pakistan in July 1996. Later in May 1998, a comparative study of aerosols in two size fractions (bulk &PM10) at 14 sites enabled to understand the anomalous distribution of several constituents present in the ambient air of the twin cities, Islamabad / Rawalpindi 90 km from South East of earlier site. The suspended particulate matter concentrations (bulk and PM10) were 475 ug/m3, 175 ug/m3 respectively. For urban areas Pb, Cd, Zn and Ni are obviously contributed by steel and other allied industries besides vehicle's contribution of lead and cadmium. In Northern area concentrations of Al, K, Ca, and Fe exceeded 1000 ng/m3. The SO2 concentrations varied from 0.03 to 1.2 ppb. Mean SO4 2- and NO3 - concentrations were 5.2 ug/m3 and 3.6 ug/m3 respectively. Concentrations of Se, Ti, Pb, Cd, Sb, Zn and As in all aerosol samples were highly enriched relative to average crustal abundances indicating significant anthropogenic contributions. As the dominant flow pattern from the Arabian Sea through India (monsoon air pattern) this may transport pollution derived aerosol and moisture from distant sources in China or India. Key word index: Aerosol, trace metals , enrichment, anions, air pollution, Islamabad/Rawalpindi, remote site.

Ghauri, B.; Lodhi, A.

85

Characterization of plutonium aerosol collected during an accident.  

PubMed

This study determined the plutonium particle size distribution and dissolution rate of PuO2 aerosol collected during the 16 March 2000 release of an undetermined amount of PuO2 in a room within a plutonium facility at Los Alamos National Laboratory. The facility has been in operation since 1978 to support the development, fabrication, and testing of Pu heat sources for the U.S. Department of Energy. Several workers were in the room at the time of the release and in vivo study of five of the workers began the day after the exposure event. Four of the subjects subsequently received chelation therapy. Over 30 fixed air filter samplers (FASs) and four continuous air monitors (CAMs) were operating in the room during the radiological release. One 47-mm-diameter glass fiber FAS filter and one 25-cm-diameter mixed cellulose ester CAM filter containing Pu aerosol from the incident were examined in the study described here. Total alpha radioactivity on the filters was determined by gross alpha counting. Isotopic identification of the Pu was made by alpha spectrometry. Film autoradiography was used to characterize the spatial distribution of alpha-emitting particles on the filters. Track-etch autoradiography was used to estimate the distribution of alpha radioactivity in individual plutonium particles on the filters for particle size measurement. The glass fiber filter was then cut into six sections. Particles from two sections were resuspended in alcohol, dispersed as an aerosol using a Lovelace nebulizer, and characterized by aerodynamic diameter using a Lovelace Multi-jet cascade impactor. The measured activity median aerodynamic diameter from the cascade impactor was 4.8 mum with a geometric standard deviation of 1.5. That agreed with the size distribution obtained from the alpha track detection technique. The remaining four filter sections were used in an in vitro dissolution study with synthetic serum ultrafiltrate. The retention of undissolved Pu was consistent with a biphasic exponential function. The majority of the Pu dissolved with a half-time of 900 d. The information on particle size distribution and solubility from this study was useful in assigning a radiation dose to the exposed workers, supporting the decision to administer chelation therapy, and providing a model for characterizing accident-associated aerosols in the future. PMID:15545766

Cheng, Yung Sung; Guilmette, Raymond A; Zhou, Yue; Gao, Jun; Labone, Thomas; Whicker, Jeffrey J; Hoover, Mark D

2004-12-01

86

Stratospheric sulfate from the Gareloi eruption, 1980: Contribution to the ''ambient'' aerosol by a poorly documented volcanic eruption  

SciTech Connect

While sampling stratospheric aerosols during July--August 1980 a plume of ''fresh'' volcanic debris was observed in the Northern hemisphere. The origin of this material seems to be a poorly documented explosive eruption of Gareloi valcano in the Aleutian Islands. The debris was sampled at an altitude of 19.2 km: almost twice the height of observed eruption clouds. Such remote, unobserved or poorly documented eruptions may be a source that helps maintain the ''ambient'' stratospheric aerosol background.

Sedlacek, W.A.; Mroz, E.J.; Heiken, G.

1981-07-01

87

HOUSTON URBAN PLUME STUDY, 1974. MICROSCOPICAL IDENTIFICATION OF COLLECTED AEROSOLS  

EPA Science Inventory

An urban plume study was conducted in Houston during July 1974 to gain preliminary data on the concentration and composition of primary and secondary aerosols contributing to Houston's air pollution problem. Selected membrane filter samples containing urban aerosols were analyzed...

88

Phenols and hydroxy-PAHs (arylphenols) as tracers for coal smoke particulate matter: source tests and ambient aerosol assessments  

SciTech Connect

Source tests were conducted to analyze and characterize diagnostic key tracers for emissions from burning of coals with various ranks. Coal samples included lignite from Germany, semibituminous coal from Arizona, USA, bituminous coal from Wales, UK and sample from briquettes of semibituminous coal, bituminous coal and anthracite from China. Ambient aerosol particulate matter was also collected in three areas of China and a background area in Corvallis, OR (U.S.) to confirm the presence of tracers specific for coal smoke. The results showed a series of aliphatic and aromatic hydrocarbons and phenolic compounds, including PAHs and hydroxy-PAHs as the major tracers, as well as a significant unresolved complex mixture (UCM) of compounds. The tracers that were found characteristic of coal combustion processes included hydroxy-PAHs and PAHs. Atmospheric ambient samples from Beijing and Taiyuan, cities where coal is burned in northern China, revealed that the hydroxy-PAH tracers were present during the wintertime, but not in cities where coal is not commonly used (e.g., Guangzhou, South China). Thus, the mass of hydroxy-PAHs can be apportioned to coal smoke and the source strength modeled by summing the proportional contents of EC (elemental carbon), PAHs, UCM and alkanes with the hydroxy-PAHs. 36 refs., 2 figs., 3 tabs.

Bernd R.T. Simoneit; Xinhui Bi; Daniel R. Oros; Patricia M. Medeiros; Guoying Sheng; Jiamo Fu [Oregon State University, Corvallis, OR (United States). Environmental Sciences Program

2007-11-01

89

Characterization of the Changes in Hygroscopicity of Ambient Organic Aerosol due to Oxidation by Gas Phase OH  

NASA Astrophysics Data System (ADS)

Despite the ubiquitous nature of organic aerosols and their importance in climate forcing, the influence of chemical processes on their ability to act as cloud condensation nuclei (CCN) in the atmosphere remains uncertain. Changes to the hygroscopicity of ambient organic aerosol due to OH oxidation were explored at a remote forested (Whistler, British Columbia) and an urban (Toronto, Ontario) site. Organic aerosol was exposed to controlled levels of OH radicals in a portable flow tube reactor, the Toronto Photo-Oxidation Tube (TPOT). An Aerodyne Aerosol Mass Spectrometer (AMS) monitored the changes in the chemical composition due to OH-initiated oxidation. The CCN activity of size-selected particles was measured with a DMT Cloud Condensation Nuclei Counter (CCNc) to determine the hygroscopicity parameter, ?. Preliminary results suggest that gas phase OH oxidation increases the degree of oxygenation of organic aerosol, leading to increases in hygroscopicity. These results yield insights into the mechanism by which oxidation affects the hygroscopicity of ambient aerosol of various sources, and to constrain the main aging process that leads to the observation of increasing hygroscopicity with increasing oxidation of organic aerosol.

Wong, J. P.; McWhinney, R. D.; Slowik, J. G.; Abbatt, J.

2011-12-01

90

Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at a continental site (Cabauw)  

Microsoft Academic Search

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30-40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties - especially the aerosol light scattering - are strongly dependent on RH. The knowledge of this RH effect is of eminent importance for climate forcing calculations or for the comparison

P. Zieger; E. Weingartner; B. Henzing; M. Moerman; G. de Leeuw; J. Mikkilä; K. Clémer; M. van Roozendael; S. Yilmaz; U. Friess; H. Irie; T. Wagner; R. Shaiganfar; S. Beirle; A. Apituley; K. Wilson; U. Baltensperger

2010-01-01

91

Characterization of radicals and high-molecular weight species from alpha-pinene/ozone reaction and ambient aerosol samples  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol formed during oxidation of different volatile organic compounds is composed from a number of final and intermediate reaction products. The final products include compounds in both low and high molecular weight range called also oligomer species. These compounds can be highly volatile, as well as being semi- or low-volatility compounds. This study characterized intermediate reactive radical products formed from previously often studied alpha-pinene/ozone reaction. In order to passivate those radical species nitrone spin traps were used. 5,5-dimethyl-4,5-dihydro-3H-pyrrole-N-oxide (DMPO), and 5-dietoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) traps were able to successfully trap oxygen- and carbon-centered radicals produced from alpha-pinene/ozone reaction. Electrospray ionization (ESI) in negative ion mode with mass spectrometry (MS) detection was used to scan spectra of formed spin trap adducts and the tandem mass spectrometry (MSn) to elucidate its structures as well as structures of captured radicals. The same method was applied to analyze radical species present in ambient PM2.5 samples. Few carbon- (alkyl) and oxygen- (alkoxyl) centered radicals were captured with DMPO and DEPMPO traps. The second part of this study was focused on high molecular weight (high-MW) species formed from the same reaction (alpha-pinene/ozone), but found also in fine particulate matter fractions of ambient samples. LC/MS/MS analysis of dimer species from chamber study revealed fragments that can originate from peroxide structures. Proposed reaction for these peroxide dimer formation is self reaction of two peroxyl radicals, followed by the loss of oxygen molecule. These findings emphasize the role of peroxyl (ROO) radicals in formation of high-MW products and are in line with the high O:C ratio results reported in other studies. Water soluble organic carbon (WSOC) extracts of three size fractions of the ambient aerosol, PM1--2.5, PM0.1--1, and PM<0.1, were obtained. For all samples, the fine PM 1--2.5 fraction accounts for the largest WSOC content (from 37% to 47%), while the ultrafine particles in PM<0.1 contribute the least to the WSOC content (19% to 29%). Spectroscopic measurements (UV-VIS and fluorescence) confirmed structural similarities with aquatic fulvic and hulic acids. However, absorption and emission maxima were shifted to lower wavelengths compared to aquatic standards, indicating the presence of lower MW species and a lower degree of aromaticity. Results showed that the samples collected during September and especially in October had higher MW and higher percentage of aromatic carbon when compared with samples collected during summer months (July/August). Spectroscopy results were confirmed with ESI/MS analysis. That analysis also confirmed presence of four different classes of compounds in ambient aerosols: carboxylic acids, poly-carboxylic acids, organosulfates, and organonitrates.

Pavlovic, Jelica

92

Coated or Embedded? Organic Matter as a Host for Individual Ambient Atmospheric Aerosol Particles (Invited)  

NASA Astrophysics Data System (ADS)

Organic matter is a prominent form of atmospheric aerosol particle. It commonly occurs with soot, sulfate, metals, or mineral dust in individual, internally mixed particles and is important when estimating radiative and health effects of aerosols. The details of these mini-assemblages are well observed when using transmission electron microscopy (TEM). When organic matter hosts soot particles, it enhances the light absorption of the soot and thus its warming effects. We determined the shapes of organic matter embedding soot using electron tomography (ET) with a transmission electron microscope, calculated the radiative forcing of such particles, and compared them to those of various coating and mixing models. Organic matter in particles collected from the vicinity of Mexico City (as part of the MILAGRO - Megacity Initiative: Local and Global Research Observations - campaign conducted in March 2006) also hosts metal-bearing nanoparticles that can include Fe, Zn, Mn, Pb, Hg, Sn, Cr, Ni, Ti, V, or Ag as major constituents. Nanoparticles of Hg are especially abundant. The nanoparticles are interesting because of their small sizes and high surface-to-volume ratios, both of which make them highly reactive in the human body and can cause negative health effects. In these and samples from other areas, we commonly find organic matter coating or otherwise associated with (hosting) inorganic aerosol particles of all types. Although the atmospheric community commonly speaks of coatings onto aerosol particles, in the case of organic matter, a more apt term might be embedding rather than coating. Finally, such hosting by organic matter can influence the climate and health effects of aerosol particles.

Buseck, P. R.; Adachi, K.

2009-12-01

93

Chemical characterization of ambient submicron aerosol during summer 2012 in Patras, Greece  

NASA Astrophysics Data System (ADS)

Ultrafine aerosol was measured at an urban background site in Patras, Greece, during summer 2012 (8-27 June) in an effort to better understand the sources and the characteristics of atmospheric aerosols in the eastern Mediterranean. An Aerodyne High Resolution Aerosol Mass Spectrometry (HR-AMS) was employed to measure the size-resolved chemical composition of the non-refractory PM1. The average total PM1 concentration was 11 ?g m,-3with organic aerosol (OA) contributing 44.3%, sulfate 38.9%, ammonium 11.1%, nitrate 1.2%, and black carbon (BC) 4.5%. Using the algorithm of Kostenidou et al. (2007) the collection efficiency (CE) and the organic density was estimated with a 2 hour resolution. The average CE was 0.75±0.13 and the average organic density was 1.27±0.21 g cm-3. The overall organic to carbon (O:C) mass ratio was 0.64, and average fragments of m-z 44 and 57 represented 0.15 and 0.01 of the organic signal correspondingly. Positive matrix factorization (PMF) analysis was performed on the high resolution (HR) organic mass spectra. 3 sources could be identified: LV-OOA (low volatility oxygenated OA) related to aged OA, SV-OOA (semi-volatile oxygenated OA) a less oxygenated OA and HOA (hydrocarbon-like OA) associated with traffic emissions. On average the organic matter consisted of 30% LV-OOA, 50% SV-OOA and 20% HOA. The LV-OOA correlated well with sulfate and ammonium (R2=0.81 and 0.78). The SV-OOA had a good correlation with chlorobenzene and nopinone (R2=0.62 and 0.58), measured by a Proton Transfer Reaction Mass Spectrometer (PTR-MS). The HOA factor correlated well with BC (R2=0.51), nitrate (R2=0.62), NO2 (R2=0.40), benzene (R2=0.48) and toluene (R2=0.45). The mass fraction of the HOA factor anti-correlated with the organic density indicating that the density of the fresher OA is lower than the density of the oxygenated OA. During the campaign no nucleation event was observed, due to the fact that the aerosol was always acid (0.73±0.07 acidity). References: Kostenidou, E., Pathak, R. K., and Pandis, S. N.: An algorithm for the calculation of secondary organic aerosol density combining AMS and SMPS data, Aerosol Sci. Technol., 41, 1002-1010, 2007.

Kostenidou, Evangelia; Kaltsonoudis, Christos; Pandis, Spyros

2013-04-01

94

Measurement of laboratory and ambient aerosols with temperature and humidity controlled nephelometry  

NASA Astrophysics Data System (ADS)

The relationships between fine particle light scattering extinction coefficient, relative humidity and temperature can be used to quantify sulfate mass concentration and composition for laboratory generated and ambient aerosols. This measurement involves the use of an integrating nephelometer as well as a system for controlling the temperature and relative humidity of the air directly upstream of the nephelometer. Recent improvements in the control of these variables has subsequently enhanced our ability to detect the presence of sulfate compounds in complex atmospheric mixtures. Measurements at two urban sites (Seattle, WA and Riverside, CA) indicate the presence of fine presence of fine particle sulfate compounds mixed with more volatile compounds. Measurements at a 'background' site (Ozette Lake, WA) indicate a mixture of acidic sulfate compounds with compounds that are less volatile than (NH 4) 2SO 4.

Rood, M. J.; Larson, T. V.; Covert, D. S.; Ahlquist, N. C.

95

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

96

Detection of biological particles in ambient air using Bio-Aerosol Mass Spectrometry  

SciTech Connect

The Bio-Aerosol Mass Spectrometry (BAMS) system is an instrument used for the real time detection and identification of biological aerosols. Particles are drawn from the atmosphere directly into vacuum and tracked as they scatter light from several continuous wave lasers. After tracking, the fluorescence of individual particles is excited by a pulsed 266nm or 355nm laser. Molecules from those particles with appropriate fluorescence properties are subsequently desorbed and ionized using a pulsed 266nm laser. Resulting ions are analyzed in a dual polarity mass spectrometer. During two field deployments at the San Francisco International Airport, millions of ambient particles were analyzed and a small but significant fraction were found to have fluorescent properties similar to Bacillus spores and vegetative cells. Further separation of non-biological background particles from potential biological particles was accomplished using laser desorption/ionization mass spectrometry. This has been shown to enable some level of species differentiation in specific cases, but the creation and observation of higher mass ions is needed to enable a higher level of specificity across more species. A soft ionization technique, matrix-assisted laser desorption/ionization (MALDI) is being investigated for this purpose. MALDI is particularly well suited for mass analysis of biomolecules since it allows for the generation of molecular ions from large mass compounds that would fragment under normal irradiation. Some of the initial results from a modified BAMS system utilizing this technique are described.

McJimpsey, E L; Steele, P T; Coffee, K R; Fergenson, D P; Riot, V J; Woods, B W; Gard, E E; Frank, M; Tobias, H J; Lebrilla, C

2006-03-16

97

Evidence and Quantitation of Aromatic Organosulfates in Ambient Aerosols in Lahore, Pakistan  

NASA Astrophysics Data System (ADS)

Organosulfates are important components of secondary organic aerosol (SOA) in ambient atmospheres, yet their structures, abundances, and formation processes are not well understood. In this study, a new type of organosulfate with an aromatic carbon backbone is identified and quantified in fine particulate matter (PM2.5) in the heavily polluted megacity of Lahore, Pakistan. An authentic standard of benzyl sulfate was synthesized and confirmed the presence of this unique compound in aerosol samples using high-resolution time-of-flight tandem mass spectrometry. Benzyl sulfate was quantified using ultra-performance liquid chromatography (UPLC) with negative electrospray ionization triple quadrupole mass spectrometry (ESI-MS/MS). The highest monthly-average benzyl sulfate concentrations were recorded in January and November 2007 (0.50±0.11 ng m-3), whereas the lowest concentration was observed in July (0.05±0.02 ng m-3). Seasonal trends were consistent with synoptic meteorology, with maxima occurring during the dry season and minima during the monsoonal summer. Matrix effects were evaluated by comparison of results obtained by external calibration and the method of standard addition; a minor deviation was observed (<10%) and matrix effects were determined to be insignificant in benzyl sulfate quantitation. Although benzyl sulfate contributions to organic carbon were relatively small (<0.001%), it may be an important tracer for organosulfates derived from anthropogenic volatile organic compounds.

Stone, B. A.; Kundu, S.; Yu, G.; Keutsch, F. N.; Quraishi, T.

2012-12-01

98

Measurement of Fluorescence Spectra from Ambient Aerosol Particles Using Laser-induced Fluorescence Technique  

NASA Astrophysics Data System (ADS)

To obtain the information of composition of organic aerosol particles in atmosphere, we developed an instrument using laser-induced fluorescence (LIF) technique. To measure the fluorescence from a particle, we employed two lasers. Scattering light signal derived from a single particle upon crossing the 635nm-CW laser triggers the 266nm-pulsed laser to excite the particle. Fluorescence from the particle in the wavelength range 300-600nm is spectrally dispersed by a grating spectrometer and then detected by a 32-Ch photo-multiplier tube(PMT). The aerosol stream is surrounded by a coaxial sheath air flow and delivered to the optical chamber at atmospheric pressure. Using PSL particles with known sizes, we made a calibration curve to estimate particle size from scattering light intensity. With the current setup of the instrument we are able to detect both scattering and fluorescence from particles whose diameters are larger than 0.5um. Our system was able to differentiate particles composed of mono-aromatic species (e.g. Tryptophan) from those of Riboflavin, by their different fluorescence wavelengths. Also, measurements of fluorescence spectra of ambient particles were demonstrated in our campus in Yokosuka city, facing Tokyo bay in Japan. We obtained several types of florescence spectra in the 8 hours. Classification of the measured fluorescence spectra will be discussed in the presentation.

Taketani, F.; Kanaya, Y.; Nakamura, T.; Moteki, N.; Takegawa, N.

2011-12-01

99

Atmospheric 7Be in ambient aerosols: Implications to Stratosphere-Troposphere Exchange  

NASA Astrophysics Data System (ADS)

The environmental radionuclides of natural and anthropogenic origin serve as a robust tool to study various atmospheric processes. Among several of the applications, the most relevant is their ability to serve as tracers for the long-range transport of aerosols and their residence time. In this context, ^{7}Be and ^{210}Pb are of immense use for the atmospheric vertical mixing and transport of Ozone under Global Atmospheric Watch (GAW) programme. The ^{7}Be is a cosmogenic nuclide, produced in the atmosphere by spallation of oxygen and nitrogen with high-energy cosmic rays. The production of ^{7}Be is mainly confined to the lower stratosphere. Soon after its production, ^{7}Be gets attached to sub-micron size particles and transported to the lower troposphere via vertical mixing when the atmosphere is relatively thin. It is estimated that stratospheric transport contributes nearly 60% in the spring (March-April) and decreases to ˜25% in the autumn. In contrast, atmospheric ^{210}Pb (t _{1/2} = 22.3 yrs) is formed in the lower atmosphere from the radioactive decay of ^{222}Rn (t _{1/2} = 3.8 days) emanated from the Earth's surface. The relatively short half-life of ^{7}Be (t _{1/2} = 53.3 days) and its constant production serves as an efficient tracer for studying the stratosphere--troposphere exchange (STE). The downward intrusion of O _{3} by STE increases the tropospheric O _{3} concentration. The observations made on ^{7}Be from European high-altitude sites suggest that lower tropospheric O _{3} concentration is influenced by the transport of ozone from the upper troposphere/lower stratosphere. However, there is lack of systematic measurements of ^{7}Be from high-altitude sites in India. We report here on the long-term (2001-2007) measurements of ^{210}Pb and ^{7}Be in ambient aerosols (n=155) from a high-altitude site (Mt Abu; 24.6 °N and 72.7 °E; ˜1700 m asl) in western India. Bulk-aerosol samples were collected (once every week) from a high-altitude site, Mt Abu (˜1700 m asl) using a high-volume sampler. The sampler was operated at a flow rate of 1.0±0.1 m ^{3} min ^{-1} for ˜24 hrs to filter about 1500 m ^{3} of air through quartz microfiber filters (20 x 25 cm ^{2}). The ^{7}Be activities were assessed by gamma counting of 477.5 keV photo-peak on a low background high-purity Germanium (HPGe) detector; whereas ^{210}Pb activities were determined via ^{210}Po (E?= 5.33 MeV) by alpha-spectrometry using silicon surface barrier detectors. The ^{210}Pb activity ranges from (0.19±0.01) to (2.62±0.12) mBq m ^{-3} and that of ^{7}Be from (1.0±0.5) to (19.1±1.0) mBq m ^{-3}. The ^{7}Be/ ^{210}Pb activity ratios vary from 2.7 to 29.1 during the measurement period. In general, ^{7}Be activities and ^{7}Be/ ^{210}Pb ratios (˜10-14) are relatively high during March-June (spring and summer months). The relatively high ^{7}Be/ ^{210}Pb ratios are attributed to the downwelling of stratospheric air masses, enriched in ^{7}Be, when the troposphere is relatively thin and less stable. The surface air-temperature is high in the summer and lighter air-parcel moves vertically upward and drier and dense air (enriched in ^{7}Be) from the stratosphere descends to the lower troposphere. However, the S-T exchange is not observed during post-monsoon and winter months when the atmosphere is stable and stagnant. In contrast to relatively high ^{210}Pb activities, ^{7}Be activity and ^{7}Be/ ^{210}Pb ratio are lower during the post-monsoon and winter seasons (September-December). These results demonstrate the usefulness of ^{7}Be and ^{7}Be/ ^{210}Pb ratio for the S-T exchange and have implications to assess temporal variability in the tropospheric O _{3} in tropical regions.

Ram, Kirpa; Sarin, Manmohan

2012-07-01

100

WIDE RANGE AEROSOL CLASSIFIER  

EPA Science Inventory

The purpose of this project was to design, construct, calibrate, and field test a mobile ambient particulate matter sampler (Wide Range Aerosol Classifier) to collect size-classified samples of large aerosol particles. The sampler design was based on a similar stationary sampling...

101

CCN estimates from bulk hygroscopic growth factors of ambient aerosols during the pre-monsoon season over Central Nepal  

NASA Astrophysics Data System (ADS)

Aerosol size distribution (ambient and dried) and chemical composition were measured simultaneously using two Scanning Mobility Particle Sizers (SMPSs) and filters during the pre-monsoon season (April-June 2009) at two locations in Central Nepal: Dhulikhel, an urban site in the Kathmandu valley, and Besisahar, a rural village in the Marsyangdi valley. Diameter growth factors (DGF) were estimated using the larger mode (around 100 nm) of the aerosol size distributions. The measured DGF suggest that the aerosols were in metastable state below 80% RH owing to the strong diurnal cycle of relative humidity (RH) at Dhulikhel, while no discernible growth was observed for Besisahar. Assuming ideal behavior of water-soluble organic compounds and using their fraction as determined by water extraction of filters produced the best agreement for a two-component hygroscopic growth model with the observed DGFs. This finding together with the DGF and chemical composition data were used to determine the aerosol bulk hygroscopicity parameter, ?. The ? parameter suggests that aerosols in this region are less hygroscopic than aerosols reported in previous studies from other regions. The estimated ? and the vertically scaled aerosol size distribution were then used to estimate the CCN spectra. These are the first estimates of CCN spectra from ground-based observations for the Central Himalaya region.

Shrestha, Prabhakar; Barros, Ana P.; Khlystov, Andrei

2013-03-01

102

Humic-like substances in fresh emissions of rice straw burning and in ambient aerosols in the Pearl River Delta Region, China  

NASA Astrophysics Data System (ADS)

HUmic-LIke Substances (HULIS) are an abundant unresolved mixture of organic compounds present in atmospheric samples. Biomass burning (BB) has been recognized as an important primary source of HULIS, but measurements of HULIS in various fresh BB particles are lacking. In this work, HULIS in emissions of rice straw burning was measured in a number of field and chamber experiments. The average HULIS/OC ratio was 0.34±0.05 in ?g/?gC, showing small variance among emissions under different burning conditions. The influence of BB on ambient HULIS levels was investigated by examining the spatial and temporal variation of HULIS and other aerosol constituents and interspecies relations in ambient PM2.5. The PM2.5 samples were collected at an urban and a suburban location in the Pearl River Delta (PRD), China over a period of one year. The HULIS concentrations in the ambient PM2.5 were significantly higher in air masses originating from regions influenced by BB. Significant correlations between HULIS and water-soluble K+ concentrations at both sites further support that BB was an important source of HULIS. Ambient concentrations of HULIS also correlated well with those of sulfate, oxalate, and oxidant (the sum of O3 and NO2). The HULIS/OC ratios in BB-influenced ambient aerosols (~0.6) were much higher than those in the fresh BB emissions (0.34), implying that secondary formation was also an important source of HULIS in the atmosphere. The annual average HULIS concentrations were 4.9 ?g m-3 at the urban site and 7.1 ?g m-3 at the suburban site while the annual average concentrations of elemental carbon were 3.3 ?g m-3 and 2.4 ?g m-3, respectively. The urban-suburban spatial gradient of HULIS was opposite to that of elemental carbon, negating vehicular exhaust as a significant primary emission source of HULIS.

Lin, P.; Engling, G.; Yu, J. Z.

2010-07-01

103

Evaluation of a Method for Field Collection of Ultra-Low Volume-Size Aerosol Droplets.  

National Technical Information Service (NTIS)

Studies were conducted to develop practical alternates to the hand-wave method for the field collection of ULV-size aerosol droplets. A comparative evaluation between the hand-wave method and settling chambers was made using aerosol droplets of malathion ...

E. S. Evans C. D. Davenport

1974-01-01

104

X-RAY FLUORESCENCE ANALYSIS OF FILTER-COLLECTED AEROSOL PARTICLES  

EPA Science Inventory

X-ray fluorescence (XRF) has become an effective technique for determining the elemental content of aerosol samples. For quantitative analysis, the aerosol particles must be collected as uniform deposits on the surface of Teflon membrane filters. An energy dispersive XRF spectrom...

105

Characterization of Primary Organic Aerosol Emissions from Meat Cooking, Trash Burning, and Combustion Engines with High-Resolution Aerosol Mass Spectrometry and Comparison with Ambient and Chamber Observations  

NASA Astrophysics Data System (ADS)

Organic aerosol (OA) emissions from motor vehicles, meat-cooking and trash burning are analyzed here using a high-resolution aerosol mass spectrometer (AMS) and supporting instrumentation. A semi-quantitative comparison of emission factors highlights the potential importance of meat cooking as an OA source. GC-MS and AMS mass spectra are compared for the first time and show high similarity, but with more fragmentation in the AMS due to higher vaporization temperatures. High resolution data show that aerosols emitted by combustion engines and plastic burning are dominated by hydrocarbon-like organic compounds. Meat cooking and especially paper burning contain significant fractions of oxygenated organic compounds; however, their unit-resolution mass spectral signatures are very similar to mass spectral signatures from hydrocarbon-like OA or primary OA, and very different from the mass spectra of ambient secondary or oxygenated OA (OOA). Thus, primary OA from any of these sources is very unlikely to be a significant direct source of ambient OOA. There are significant differences in high-resolution tracer m/z's that may be useful for differentiating these sources from each other. Unlike in most ambient spectra, all of these sources have low total m/z 44 and this signal is not dominated by the CO2+ ion. All sources have high m/z 57, which is low during high OOA ambient periods. Spectra from paper burning are similar to some types of biomass burning OA, with elevated m/z 60. Meat cooking aerosols also have slightly elevated m/z 60, while motor vehicle emissions have very low signal at this m/z.

Mohr, C.; Huffman, J. A.; Cubison, M. J.; Aiken, A. C.; Docherty, K. S.; Kimmel, J. R.; Ulbrich, I. M.; Hannigan, M.; Garcia, J.; Jimenez, J. L.

2009-04-01

106

Composition of urban and rural aerosol samples collected in the Great Hungarian Plain  

NASA Astrophysics Data System (ADS)

Urban and rural atmospheric aerosol samples have been collected simultaneously during 1997 in the Great Hungarian Plain. The elemental composition of the coarse and fine mode aerosol have been determined by the Proton-Induced X-ray Emission method. From the observed elemental concentrations, seasonal variations and variations with the wind sector distributions were found for separate elements. Principal component analyses gave four factors in urban aerosol, and three factors in the rural one. The order of the factors in the coarse mode aerosol is different from the order, found in the fine mode.

Borbély-Kiss, I.; Kertész, Zs.; Koltay, E.; Szabó, Gy.; Tar, K.

1999-04-01

107

Real-time Characterization of Particle-bound Polycyclic Aromatic Hydrocarbons in Ambient Aerosols and From Motor-Vehicles Exhausts  

NASA Astrophysics Data System (ADS)

During the spring of 2007 a diffusion charger (DC), a photoelectric aerosol sensor (PAS), and a condensation particle counter (CPC) were operated a) in Wilmington (CA), an urban area near the Los Angeles port heavily influenced by a mix of industrial and gasoline- / diesel-fuelled vehicle emissions, and b) at the California Air Resource Board (CARB) Heavy-Duty Diesel Emissions Test Laboratory (HDETL), a dynamometer testing facility in downtown Los Angeles (CA). During the dynamometer tests, we characterized the exhausts of several individual types of vehicles, equipped with different emission control technologies, and operated under different driving conditions. Information about the chemical composition, active surface area, and particle number concentration from the PAS, DC, and CPC were combined to identify the main chemical and physical characteristics of the studied aerosols. In particular, the ratio between the PAS and the DC signals (PAS/DC) provided a reliable measurement of the amount of particle-bound Polycyclic Aromatic Hydrocarbon (pPAH) per unit area of the active surface of the particles. This quantity may be directly related to the amount of pPAHs transported into the human respiratory tract. Plots of the PAS/DC ratio versus the average surface particle diameter (Dp; estimated by combining DC and CPC measurements) were then used to distinguish between the presence/absence of nuclei mode particles and the presence/absence of an adsorbed layer on accumulation mode particles, for both ambient and dynamometer-tests data. All results were then complemented with measurements of the particle size distribution (SMPS) and of the black carbon (BC) aerosol content to obtain further insights on the pPAHs emitted by motor-vehicles and other sources. Integrated 24-h filter samples were also collected in Wilmington, solvent extracted and analyzed by GC/MS to determine the relative concentrations of the 11 most abundant pPAHs found at the urban site. Finally, these results were used to establish correlations between the concentrations of each individual PAH species and the measured PAS signal (from fA to ? g/m3).

Polidori, A.; Hu, S.; Biswas, S.; Sioutas, C.

2007-12-01

108

Dynamic Behavior of Fibrous Filters during Collection of Submicrometer Aerosols: A Dispersion Model.  

National Technical Information Service (NTIS)

A novel fundamental theory of the dynamic behavior of fibrous filters for aerosol collection is proposed. The theory is based upon an explicit and systematic procedure for calculating the filter efficiency and for qualitatively describing the filter micro...

H. Brenner M. Shapiro

1991-01-01

109

A concept of an automated function control for ambient aerosol measurements using mobility particle size spectrometers  

NASA Astrophysics Data System (ADS)

An automated function control unit was developed to regularly check the ambient particle number concentration derived from a mobility particle size spectrometer as well as its zero-point behaviour. The aim of the new feature is to conduct unattended quality control experiments under field conditions at remote air quality monitoring or research stations. The automated function control also has the advantage of being able to get a faster system stability response than the recommended on-site comparisons with reference instruments. The method is based on a comparison of the total particle number concentration measured by a mobility particle size spectrometer and a condensation particle counter removing the diffusive particles approximately smaller than 25 nm in diameter. In practice, the small particles are removed by a set of diffusion screens, as traditionally used in a diffusion battery. The other feature of the automated function control is to check the zero-point behaviour of the ambient aerosol passing through a high-efficiency particulate air (HEPA) filter. An exemplary one-year data set is presented for the measurement site Annaberg-Buchholz as part of the Saxon air quality monitoring network. The total particle number concentration derived from the mobility particle size spectrometer overestimates the particle number concentration by only 2% (grand average offset). Furthermore, tolerance criteria are presented to judge the performance of the mobility particle size spectrometer with respect to the particle number concentration. An upgrade of a mobility particle size spectrometer with an automated function control enhances the quality of long-term particle number size distribution measurements. Quality assured measurements are a precondition for intercomparison studies of different sites. Comparable measurements will improve cohort health and also climate-relevant research studies.

Schladitz, A.; Merkel, M.; Bastian, S.; Birmili, W.; Weinhold, K.; Löschau, G.; Wiedensohler, A.

2013-12-01

110

A concept of an automated function control for ambient aerosol measurements using mobility particle size spectrometers  

NASA Astrophysics Data System (ADS)

An automated function control unit was developed to regularly check the ambient particle number concentration derived from a mobility particle size spectrometer as well as its zero-point behaviour. The function control allows unattended quality assurance experiments at remote air quality monitoring or research stations under field conditions. The automated function control also has the advantage of being able to get a faster system stability response than the recommended on-site comparisons with reference instruments. The method is based on a comparison of the total particle number concentration measured by a mobility particle size spectrometer and a condensation particle counter while removing diffusive particles smaller than 20 nm in diameter. In practice, the small particles are removed by a set of diffusion screens, as traditionally used in a diffusion battery. Another feature of the automated function control is to check the zero-point behaviour of the ambient aerosol passing through a high-efficiency particulate air (HEPA) filter. The performance of the function control is illustrated with the aid of a 1-year data set recorded at Annaberg-Buchholz, a station in the Saxon air quality monitoring network. During the period of concern, the total particle number concentration derived from the mobility particle size spectrometer slightly overestimated the particle number concentration recorded by the condensation particle counter by 2 % (grand average). Based on our first year of experience with the function control, we developed tolerance criteria that allow a performance evaluation of a tested mobility particle size spectrometer with respect to the total particle number concentration. We conclude that the automated function control enhances the quality and reliability of unattended long-term particle number size distribution measurements. This will have beneficial effects for intercomparison studies involving different measurement sites, and help provide a higher data accuracy for cohort health and climate research studies.

Bastian, S.; Löschau, G.; Wiedensohler, A.

2014-04-01

111

Dependence of Aerosol Light Absorption and Single-Scattering Albedo On Ambient Relative Humidity for Sulfate Aerosols with Black Carbon Cores  

NASA Technical Reports Server (NTRS)

Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of the lack of detailed knowledge about various input parameters to models describing internally mixed aerosol particle optics, we focus on results that were aimed at determining the maximum effect that particle humidification may have on aerosol light absorption. In the wavelength range from 450 to 750 nm, maximum absorption humidification factors (ratio of wet to 'dry=30% RH' absorption) for single aerosol particles are found to be as large as 1.75 when the RH changes from 30 to 99.5%. Upon lesser humidification from 30 to 80% RH, absorption humidification for single particles is only as much as 1.2, even for the most favorable combination of initial ('dry') soot mass fraction and particle size. Integrated over monomodal lognormal particle size distributions, maximum absorption humidification factors range between 1.07 and 1.15 for humidification from 30 to 80% and between 1.1 and 1.35 for humidification from 30 to 95% RH for all species considered. The largest humidification factors at a wavelength of 450 nm are obtained for 'dry' particle size distributions that peak at a radius of 0.05 microns, while the absorption humidification factors at 700 nm are largest for 'dry' size distributions that are dominated by particles in the radius range of 0.06 to 0.08 microns. Single-scattering albedo estimates at ambient conditions are often based on absorption measurements at low RH (approx. 30%) and the assumption that aerosol absorption does not change upon humidification (i.e., absorption humidification equal to unity). Our modeling study suggests that this assumption alone can introduce absolute errors in estimates of the midvisible single-scattering albedo of up to 0.05 for realistic dry particle size distributions. Our study also indicates that this error increases with increasing wavelength. The potential errors in aerosol single-scattering albedo derived here are comparable in magnitude and in addition to uncertainties in single-scattering albedo estimates that are based on measurements of aerosol light absorption and scattering.

Redemann, Jens; Russell, Philip B.; Hamill, Patrick

2001-01-01

112

The MODIS Aerosol Algorithm: Critical Evaluation and Plans for Collection 6  

NASA Technical Reports Server (NTRS)

For ten years the MODIS aerosol algorithm has been applied to measured MODIS radiances to produce a continuous set of aerosol products, over land and ocean. The MODIS aerosol products are widely used by the scientific and applied science communities for variety of purposes that span operational air quality forecasting in estimates o[ clear-sky direct radiative effects over ocean and aerosol-cloud interactions. The products undergo continual evaluation, including self-consistency checks and comparisons with highly accurate ground-based instruments. The result of these evaluation exercises is a quantitative understanding of the strengths and weaknesses of the retrieval, where and when the products are accurate and the situations where and when accuracy degrades. We intend 10 present results of the most recent critical evaluations including the first comparison of the over ocean products against the shipboard aerosol optical depth measurements of the Marine Aerosol Network (MAN), the demonstration of the lack of sensitivity to size parameter in the over land products and identification of residual problems and regional issues. While the current data set is undergoing evaluation, we are preparing for the next data processing, labeled Collection 6. Collection 6 will include transparent Quality Flags, a 3 km aerosol product and the 500m resolution cloud mask used within the aerosol n:bicvu|. These new products and adjustments to algorithm assumptions should provide users with more options and greater control, as they adapt the product for their own purposes.

Remer, Lorraine

2010-01-01

113

The MODIS aerosol algorithm: Critical evaluation and plans for Collection 6  

NASA Astrophysics Data System (ADS)

For ten years the MODIS aerosol algorithm has been applied to measured MODIS radiances to produce a continuous set of aerosol products, over land and ocean. The MODIS aerosol products are widely used by the scientific and applied science communities for a variety of purposes that span operational air quality forecasting to estimates of clear-sky direct radiative effects over ocean and aerosol-cloud interactions. The products undergo continual evaluation, including self-consistency checks and comparisons with highly accurate ground-based instruments. The result of these evaluation exercises is a quantitative understanding of the strengths and weaknesses of the retrieval, where and when the products are accurate and the situations where and when accuracy degrades. We intend to present results of the most recent critical evaluations including the first comparison of the over ocean products against the shipboard aerosol optical depth measurements of the Marine Aerosol Network (MAN), the demonstration of the lack of sensitivity to size parameter in the over land products and identification of residual problems and regional issues. While the current data set is undergoing evaluation, we are preparing for the next data processing, labeled Collection 6. Collection 6 will include transparent Quality Flags, a 3 km aerosol product and the 500 m resolution cloud mask used within the aerosol retrieval. These new products and adjustments to algorithm assumptions should provide users with more options and greater control, as they adapt the product for their own purposes.

Remer, Lorraine; Levy, Robert; Mattoo, Shana; Kleidman, Richard; Koren, Ilan; Martins, Vanderlei

2010-05-01

114

Real-time characterization of particle-bound polycyclic aromatic hydrocarbons in ambient aerosols and from motor-vehicle exhaust  

Microsoft Academic Search

A photo-electric aerosol sensor, a diffusion charger, an Aethalometer, and a continuous particle counter were used along with other real-time instruments to characterize the particle-bound polycyclic aromatic hydrocarbon (p-PAH) content, and the physical\\/chemical characteristics of aerosols collected a) in Wilmington (CA) near the Los Angeles port and close to 2 major freeways, and b) at a dynamometer testing facility in

A. Polidori; S. Hu; S. Biswas; R. J. Delfino; C. Sioutas

2007-01-01

115

Real-time characterization of particle-bound polycyclic aromatic hydrocarbons in ambient aerosols and from motor-vehicle exhaust  

Microsoft Academic Search

A photo-electric aerosol sensor, a diffusion charger, an Aethalometer, and a continuous particle counter were used along with other real-time instruments to characterize the particle-bound polycyclic aromatic hydrocarbon (p-PAH) content, and the physical\\/chemical characteristics of aerosols collected a) in Wilmington (CA) near the Los Angeles port and close to 2 major freeways, and b) at a dynamometer testing facility in

A. Polidori; S. Hu; S. Biswas; R. J. Delfino; C. Sioutas

2008-01-01

116

Speciation of Water-Soluble Organic Carbons in Aerosols from two collecting methods: PILS and filters  

NASA Astrophysics Data System (ADS)

Total suspended particles aerosol sampling for collection of 24 h by high volume air sampler at Campus of Korea University in metropolitan city Seoul. To measure WSOC, an aliquot (2 cm2) of quartz fiber filter ( 20.3 × 25.4 cm) was extracted 5 mL Milli-Q water with hot water (80 °C) and room temperature water (25 °C) under ultrasonication (10 min, three times). Hot water extracted method was comparison with PILS samples. WSOC was quantified using a total organic carbon (TOC) analyzer. For speciation analysis of organic compounds, the extracts were concentrated to dryness using freeze dryer and then derivatized with MSTFA (N-Methyl-N-trimethy- silyltrifluoroacetamide+1% trimethylchlorosilane) and analyzed with GC-MS scan mode. In extracted with hot water, total carbon concentrations were higher than room temperature extracts. Organic compounds widely recognized to be generated from anthropogenic sources with a low solubility at ambient temperature organic were detected in both samples obtained from PILS and hot water extraction. It is demonstrating that difference between total carbon concentration and composition of sampling obtain from two different systems (i.e. PILS and filter) in analytical procedure of WSOCs. Acknowledgement This research was susported by Center for Women In Science, Engineering Technology(WISET) commissioned by the Ministry of Science, ICT & Future Planning and the National Research Foundation of korea. The authors also acknowledge the support made by a grant from the Korea Basic Science Institute.

Kim, J.; Yoon, H.; Ahn, Y.; Shin, J.; Lee, M.; Park, M.

2013-12-01

117

Modelling liquid saturation in filters collecting liquid aerosols  

Microsoft Academic Search

The removal of (oil) mists from air streams is important in many industrial applications, such as machining and cutting operations, engine closed crankcase ventilation, and compressed gas cleaning. Filters are by far the most efficient device for removing such particles, however, the filtration of liquid aerosol particles differs so greatly from dust filtration that it is almost a field in

N. Merkel; R. D Braddock; G. Kasper

2009-01-01

118

Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets  

NASA Astrophysics Data System (ADS)

The interplay between aerosol particles and water droplets in the atmosphere, especially in clouds, influences both aerosol and cloud properties. The major uncertainty in our understanding of climate arises in the indirect effect of aerosol and their ability to impact cloud formation and consequently alter the global radiative balance. The collision between a water droplet and aerosol particles that results in coalescence is termed 'collection' or 'coagulation'. Coagulation can lead to aerosol removal from the atmosphere or induce ice nucleation via contact freezing at temperatures below 0 C. Theoretical studies have shown that for aerosol particles smaller than 0.1 micrometers, Brownian motion is important, and for particles with diameters larger than 1 micrometer, inertial force dominates. There is a collection efficiency minimum for particles between 0.1-2 micrometers, called the 'Greenfield Gap'. Experimental efforts, however, have been limited to very large drizzle and rain drops until recently, and constrained parameters necessary to describe particle collection efficiency by cloud droplets have not been available. One reason is that laboratory setups that allow for coagulation to be observed on a single-particle basis have been lacking. Collection efficiency is also an important parameter for studying and assessing contact ice nucleation. Contact ice nucleation is currently the least understood ice nucleation mechanism and can be potentially important for mixed-phase cloud formation. The significance of experimentally assessing collection efficiency is therefore two-fold: to first understand the frequency of contacts and to then understand the fraction that lead to ice nucleation. We have constructed the MIT-Contact Freezing Chamber (MIT-CFC) to study collection efficiency of submicron aerosol particles by cloud droplets and contact freezing. A stream of 30-micron cloud droplets fall freely into the chamber and collide with aerosol particles. The outflow goes through a pumped counterflow virtual impactor (PCVI), which rejects aerosol particles and transmits larger particles that are either droplet residuals or coagulated particles. The larger particles are sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument for chemical composition analysis. PALMS is a true single-particle instrument and gives information on the size and the chemical composition of each particle. Coagulated particles from the MIT-CFC have mass spectral signatures from both the aerosol particles and the droplet residuals, while the droplet residual contains no signature of the aerosol particles. To our knowledge, this is the first time coagulation has been seen on a single-particle basis. We will present the collection efficiency data of a suite of dust particles with well-defined types, sizes and concentrations under atmospherically relevant temperatures and relative humidity conditions.

Huang, Y.; Ardon-Dryer, K.; Cziczo, D. J.

2013-12-01

119

China Collection 2.0: The aerosol optical depth dataset from the synergetic retrieval of aerosol properties algorithm  

NASA Astrophysics Data System (ADS)

A wide range of data products have been published since the operation of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's TERRA and AQUA satellites. Based on DarkTarget and DeepBlue method, NASA has published Aerosol Optical Depth (AOD) products Collection 5.0 and Collection 5.1 at 10 km spatial resolution. The Collection 6.0 will be published soon with spatial resolution of 3 km. Although validated globally, regional and systematic errors are still found in the MODIS-retrieved AOD products. This is especially remarkable for bright heterogeneous land surface, such as mainland China. In order to solve the aerosol retrieval problem over heterogeneous bright land surface, the Synergetic Retrieval of Aerosol Properties algorithm (SRAP) has been developed based on the synergetic use of the MODIS data of TERRA and AQUA satellites. Using the SRAP algorithm, we produced AOD dataset-China Collection 2.0, dated from August 2002 to August 2012, and compared the AOD results with AErosol Robotic NETwork (AERONET) and Chinese Meteorological Administration Aerosol Remote Sensing Network (CARSNET) measurements. We find that 62% of China Collection 2.0 AOD values are within an expected error (EE) range of ±(0.05 + 20%) and that 56% are within an EE range of ±(0.05 + 15%) when compared with AERONET-observed values. For CARSNET validation, we find that 60% of China Collection 2.0 AOD values are within an expected error (EE) range of ±(0.05 + 20%) and that 53% are within an EE range of ±(0.05 + 15%). In addition, we also compare the AOD results with MODIS aerosol products, the cross validation shows that the two AOD have good consistency. Monthly averaged AOD results show that AOD is generally high in China's eastern coastal region from March to August, and AOD is not more than 0.5 in other months. Season averaged results show that the higher values of AOD are mostly distributed in eastern and southern China.

Xue, Yong; He, Xingwei; Xu, Hui; Guang, Jie; Guo, Jianping; Mei, Linlu

2014-10-01

120

Analysis of single aerosol particles collected in urban and cave environment by proton microprobe  

NASA Astrophysics Data System (ADS)

Quantitative PIXE analysis was performed on several single aerosol particles collected with cascade impactor by the scanning proton microprobe of Debrecen. The cascade impactor samples were collected at an urban location in Debrecen and in a speleotherapeutic cave situated under Budapest during the winter of 1998. The aerosol samples have already been analysed by bulk PIXE technique. Elemental concentrations for 23 elements and also the size of the particles were determined. Cluster analysis was carried out to identify the different particle groups. The contribution of the different types of particles to each size fraction were investigated with special regard to the smaller size fractions which are interesting from the point of view of the speleotherapy. Traces of anthropogenic pollution were also shown in the cave aerosol, and the possible composition of particles containing these pollutants is given. Comparison of the urban and cave aerosol particles is also discussed.

Kertész, Zs; Borbély-Kiss, I.; Rajta, I.; Uzonyi, I.; Kiss, Á. Z.

2000-03-01

121

Aerosol collection of the (Bladewerx Corporation) breathing zone monitor and portable workplace monitor.  

PubMed

The Radiation Protection Group at the Los Alamos National Laboratory has a wind tunnel capable of measuring the aerosol collection efficiencies of air sampling devices. In the fall of 2005, the group received an internal Los Alamos request to perform aerosol collection efficiency tests on two air samplers manufactured by the Bladewerx Corporation (Rio Rancho, NM). This paper presents the results from tests performed in the wind tunnel facility at a test velocity of 0.5 m s. The SabreAlert (Portable Workplace Monitor) and the SabreBZM (Breathing Zone Monitor) are both designed to detect and measure the presence of alpha emitting isotopes in atmospheres. The SabreAlert was operated at two test air flow rates of 6 and 45 liters per minute (LPM), and the SabreBZM was operated at two test air flow rates of 3 and 19 LPM. The aerosol collection efficiencies of both samplers were evaluated with oleic acid (monodisperse) liquid droplet aerosols tagged with sodium fluorescein tracer. These test aerosols varied in size from about 2.3 to 17.2 microns (aerodynamic equivalent diameter). The SabreAlert was roughly 100% efficient in aerosol collection at a flow rate of 6 LPM, and had an aerodynamic cutpoint diameter of 11.3 microns at the 45 LPM flow rate. The SabreBZM had an aerodynamic cutpoint diameter of 6.7 microns at the 3 LPM flow rate, but the SabreBZM aerosol collection efficiency never exceeded 13.6% at the 19 LPM test flow rate condition. PMID:18049245

Moore, Murray E; Kennedy, Trevor J; Dimmerling, Paul J

2007-11-01

122

Size-resolved Measurements of Aerosol Mass and Carbon Collected During the Dry Season in the Brazilian Amazon  

Microsoft Academic Search

Aerosol samples were collected in a pasture site in the Amazon Basin as part of the project LBA-SMOCC 2002 (Large Scale Biosphere Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate) during the end of the dry season, the transition period, and the beginning of the wet season. A

O. L. Mayol-Bracero; T. W. Kirchstetter; T. Novakov; M. O. Andreae; M. Deliz-Delvalle; P. Artaxo; W. Maenhaut; T. W. Andreae

2005-01-01

123

Improved Aerosol Collection by Combined Impaction and Centrifugal Motion  

Microsoft Academic Search

A new principle for collecting airborne particles, including microorganisms, has been introduced by injecting the particles into a swirling airflow from where they are removed onto a collection surface. A dry surface, a surface coated with an adhesive substance or a surface wetted by a liquid swirled onto the collection surface from a reservoir below can be used in the

Klaus willeke; Xuejun Lin; Sergey A. Grinshpun

1998-01-01

124

Nano-sized aerosol classification, collection and analysis-method development using dental composite materials.  

PubMed

This article presents a methodical approach for generating, collecting, and analyzing nano-size (1-100 nm) aerosol from abraded dental composite materials. Existing aerosol sampling instruments were combined with a custom-made sampling chamber to create and sample a fresh, steady-state aerosol size distribution before significant Brownian coagulation. Morphological, size, and compositional information was obtained by Transmission Electron Microscopy (TEM). To create samples sizes suitable for TEM analysis, aerosol concentrations in the test chamber had to be much higher than one would typically expect in a dental office, and therefore, these results do not represent patient or dental personnel exposures. Results show that nano-size aerosol was produced by the dental drill alone, with and without cooling water drip, prior to abrasion of dental composite. During abrasion, aerosol generation seemed independent of the percent filler load of the restorative material and the operator who generated the test aerosol. TEM investigation showed that "chunks" of filler and resin were generated in the nano-size range; however, free nano-size filler particles were not observed. The majority of observed particles consisted of oil droplets, ash, and graphitic structures. PMID:24433286

Bogdan, Axel; Buckett, Mary I; Japuntich, Daniel A

2014-07-01

125

Quantitative extraction of organic tracer compounds from ambient particulate matter collected on polymer substrates.  

PubMed

Organic compounds in ambient particulate matter (PM) samples are used as tracers for PM source apportionment. These PM samples are collected using high volume samplers; one such sampler is an impactor in which polyurethane foam (PUF) and polypropylene foam (PPF) are used as the substrates. The polymer substrates have the advantage of limiting particle bounce artifacts during sampling; however these substrates may contain background organic additives. A protocol of two extractions with isopropanol followed by three extractions with dichloromethane (DCM) was developed for both substrate precleaning and analyte extraction. Some residual organic contaminants were present after precleaning; expressed as concentrations in a 24-h ambient PM sample, the residual amounts were 1 microg m(-3) for plasticizers and antioxidants, and 10 ng m(-3) for n-alkanes with carbon number lower than 26. The quantification limit for all other organic tracer compounds was approximately 0.1 ng m(-3) in a 24-h ambient PM sample. Recovery experiments were done using NIST Standard Reference Material (SRM) Urban Dust (1649a); the average recoveries for polycyclic aromatic hydrocarbons (PAHs) from PPF and PUF substrates were 117+/-8% and 107+/-11%, respectively. Replicate extractions were also done using the ambient samples collected in Nogales, Arizona. The relative differences between repeat analyses were less than 10% for 47 organic tracer compounds quantified. After the first extraction of ambient samples, less than 7% of organic tracer compounds remained in the extracted substrates. This method can be used to quantify a suite of semi- and non-polar organic tracer compounds suitable for source apportionment studies in 24-h ambient PM samples. PMID:19269480

Sun, Qinyue; Alexandrova, Olga A; Herckes, Pierre; Allen, Jonathan O

2009-05-15

126

FORMATION OF 2-METHYL TETROLS AND 2-METHYLGLYCERIC ACID IN SECONDARY ORGANIC AEROSOL FROM LABORATORY IRRADIATED ISOPRENE/NO X/SO 2/AIR MIXTURES AND THEIR DETECTION IN AMBIENT PM 2.5 SAMPLES COLLECTED IN THE EASTERN UNITED STATES  

EPA Science Inventory

A series of isoprene/NOx/air irradiation experiments, carried out in both the absence and presence of SO2, were conducted to assess whether isoprene contributes to secondary organic aerosol (SOA) formation. In the absence of SO2 , the SOA yield of 0.002 was low. However, in th...

127

Chemical and isotopic composition of humic-like substances (HULIS) in ambient aerosols in Guangzhou, South China  

Microsoft Academic Search

Humic-like substances (HULIS) constitute a class of organic compounds identified in atmospheric samples that influence many properties of aerosols in the atmosphere. In this study, six HULIS samples were isolated from atmospheric TSP samples collected at three locations in Guangzhou of China, one each in summer and in winter. On the basis of analyses by elemental analyzer, more detailed chemical

Jianzhong Song; Lulu He; Ping’an Peng; Jinping Zhao; Shexia Ma

2012-01-01

128

CHARACTERIZATION OF AMBIENT PM2.5 AEROSOL AT A SOUTHEASTERN US SITE: FOURIER TRANSFORM INFRARED ANALYSIS OR PARTICLE PHASE  

EPA Science Inventory

During a field study in the summer of 2000 in the Research Triangle Park (RTP), aerosol samples were collected using a five stage cascade impactor and subsequently analyzed using Fourier Transform Infrared Spectroscopy (FTIR). The impaction surfaces were stainless steel disks....

129

Sampler for collection and analysis of low vapor pressure chemical (LVPC) particulates/aerosols.  

PubMed

Detection of low vapor pressure chemicals (LVPCs) such as pesticides and other toxic/hazardous materials on various environmental surfaces as well as LVPC aerosols is a significant challenge for current vapor phase detectors. We describe a novel sampling device which utilizes stainless steel screens coated with a sticky polydimethylsiloxane coating for collecting LVPCs aerosolized off of a surface. Results are presented for the collection and detection of a pesticide simulant, dimethyl methylphosphonate sorbed onto silica gel (DMMP/SG), using direct analysis in real time-cylindrical ion trap mass spectrometry (DART-CITMS). PMID:24053780

Ewing, K J; Gibson, D; Sanghera, J; Miklos, F

2013-10-15

130

Advanced Analytical Microscopy Techniques for the Characterization of Ambient Particulate Matter Collected From Military Bases in the Middle East  

NASA Astrophysics Data System (ADS)

The Enhanced Particulate Matter Surveillance Program was initiated to help environmental health professionals evaluate sources of particulate matter and to assess potential health effects of troop exposure to air pollutants within the US Central Command Area of Responsibility (AOR). The study examined the concentrations and physical properties of ambient particulate matter collected at 15 deployment locations within the AOR. Ambient aerosols, including PM2.5, PM10, and total suspended particulate were collected for microscopy analysis on polycarbonate filters by Army personnel. As part of the overall effort, the PM2.5 and PM10 particle fractions were analyzed with field emission scanning electron microscopy (FESEM) and computer-controlled SEM (CCSEM). The FESEM was used to examine particle size, morphology, and chemical composition. High-resolution images, elemental spectra and x-ray maps were collected for various particles. The automated CCSEM analyses provided statistical information on particle size and mass distributions for particles greater than 0.5 microns. Data was collected for approximately 1000-2000 particles per sample. The ultrafine particle analysis was performed using a combination of CCSEM, FESEM, low-kV scanning transmission electron microscopy (STEM), and x-ray photoelectron spectroscopy (XPS). CCSEM was used to characterize particles ranging from 0.2 to 0.5 microns. FESEM was used to manually measure the diameter of particles less than 0.2 microns and collect elemental spectra. Particles less than 0.2 microns were also examined with a Hitachi S-5500 high-resolution FESEM and a K-Alpha XPS system. The Hitachi S-5500 provides simultaneous high resolution SEM and STEM imaging capabilities as well as a state-of-the-art silicon drift detector for elemental analysis. The K-Alpha XPS provides information on the elemental and chemical state surface composition of the topmost 2-10 nm of solid materials as well as chemical state surface mapping and sputter depth profiles. This presentation will discuss results from all particle size fractions, with a focus on the high-resolution SEM and XPS analyses of the ultrafine particles.

Casuccio, G. S.; Lersch, T. L.; Bunker, K. L.; Strohmeier, B. S.

2008-12-01

131

Ambient measurements of biological aerosol particles near Killarney, Ireland: a comparison between real-time fluorescence and microscopy techniques  

NASA Astrophysics Data System (ADS)

Primary biological aerosol particles (PBAP) can contribute significantly to the coarse particle burden in many environments, may thus influence climate and precipitation systems as cloud nuclei, and can spread disease to humans, animals, and plants. Measurements of PBAP in natural environments taken at high time- and size- resolution are, however, sparse and so large uncertainties remain in the role that biological particles play in the Earth system. In this study two commercial real-time fluorescence particle sensors and a Sporewatch single-stage particle impactor were operated continuously from 2 August to 2 September 2010 at a rural sampling location in Killarney National Park in south western Ireland. A cascade impactor was operated periodically to collect size-resolved particles during exemplary periods. Here we report the first ambient comparison of the waveband integrated bioaerosol sensor (WIBS-4) with the ultraviolet aerodynamic particle sizer (UV-APS) and also compare these real-time fluorescence techniques with results of fluorescence and optical microscopy of impacted samples. Both real-time instruments showed qualitatively similar behaviour, with increased fluorescent bioparticle concentrations at night when relative humidity was highest and temperature was lowest. The fluorescent particle number from the FL3 channel of the WIBS-4 and from the UV-APS were strongly correlated and dominated by a 3 ?m mode in the particle size distribution. The WIBS FL2 channel exhibited particle modes at approx. 1 and 3 ?m, and each were correlated with the concentration of fungal spores commonly observed in air samples collected at the site (ascospores, basidiospores, Ganoderma spp.). The WIBS FL1 channel exhibited variable multi-modal distributions turning into a broad featureless single mode after averaging and exhibited poor correlation with fungal spore concentrations, which may be due to the detection of bacterial and non-biological fluorescent particles. Cladosporium spp., which are among the most abundant fungal spores in many terrestrial environments, were not correlated with any of the real-time fluorescence channels, suggesting that the real-time fluorescence instruments are insensitive to PBAP classes with dark, highly absorptive cell walls. Fluorescence microscopy images of cascade impactor plates showed large numbers of coarse mode particles consistent with the morphology and weak fluorescence expected of sea salt. Some of these particles were attached to biological cells, suggesting that a marine source influenced the PBAP observed at the site and that the ocean may be an important contributor to PBAP loadings in coastal environments.

Healy, D. A.; Huffman, J. A.; O'Connor, D. J.; Pöhlker, C.; Pöschl, U.; Sodeau, J. R.

2014-02-01

132

Aerosol Sampling System for Collection of Capstone Depleted Uranium Particles in a High-Energy Environment  

SciTech Connect

The Capstone Depleted Uranium Aerosol Study was undertaken to obtain aerosol samples resulting from a kinetic-energy cartridge with a large-caliber depleted uranium (DU) penetrator striking an Abrams or Bradley test vehicle. The sampling strategy was designed to (1) optimize the performance of the samplers and maintain their integrity in the extreme environment created during perforation of an armored vehicle by a DU penetrator, (2) collect aerosols as a function of time post-impact, and (3) obtain size-classified samples for analysis of chemical composition, particle morphology, and solubility in lung fluid. This paper describes the experimental setup and sampling methodologies used to achieve these objectives. Custom-designed arrays of sampling heads were secured to the inside of the target in locations approximating the breathing zones of the vehicle commander, loader, gunner, and driver. Each array was designed to support nine filter cassettes and nine cascade impactors mounted with quick-disconnect fittings. Shielding and sampler placement strategies were used to minimize sampler loss caused by the penetrator impact and the resulting fragments of eroded penetrator and perforated armor. A cyclone train was used to collect larger quantities of DU aerosol for chemical composition and solubility. A moving filter sample was used to obtain semicontinuous samples for depleted uranium concentration determination. Control for the air samplers was provided by five remotely located valve control and pressure monitoring units located inside and around the test vehicle. These units were connected to a computer interface chassis and controlled using a customized LabVIEW engineering computer control program. The aerosol sampling arrays and control systems for the Capstone study provided the needed aerosol samples for physicochemical analysis, and the resultant data were used for risk assessment of exposure to DU aerosol.

Holmes, Thomas D.; Guilmette, Raymond A.; Cheng, Yung-Sung; Parkhurst, MaryAnn; Hoover, Mark D.

2009-03-01

133

EVALUATION OF COMPUTER-CONTROLLED SCANNING ELECTRON MICROSCOPY APPLIED TO AN AMBIENT URBAN AEROSOL SAMPLE  

EPA Science Inventory

Concerns about the environmental and public health effects of particulate matter (PM) have stimulated interest in analytical techniques capable of measuring the size and chemical composition of individual aerosol particles. Computer-controlled scanning electron microscopy (CCSE...

134

MODIS aerosol products in Collection 6:Moving towards multisensor fusion and interdisciplinary studies  

NASA Astrophysics Data System (ADS)

As the Terra satellite turns 10, so do the MODIS aerosol products. During the past ten years the MODIS products have evolved and expanded to include opportunities and capabilities nonexistent in the at-launch version. We are anticipating the next step, Collection 6, becoming available in late 2010. The new products in the Collection 6 MODIS aerosol suite of products will include: 1) Fine mode aerosol optical depth over land from the PARASOL POLDER data set, merged into the MODIS data product. This is a direct capture of the PARASOL product that will be placed in the MODIS data files. It is not a separate derivation using PARASOL radiances and polarization. The incorporation of the PARASOL product over land is collocated to the MODIS 10 km product pixel, and is provided as a convenience to MODIS users. 2) Aerosol optical depth over land at 3 km resolution for Air Quality monitoring. 3) Cloud mask and distance to the nearest cloud calculated and presented for every 500 m “cloud-free” pixel that allows better control of cloud contamination in the basic aerosol products. This information is also summarized statistically at the 10 km product resolution, and will be available for both land and ocean. 4) A Quality Assurance (QA) flag in simple plain integers that does not require a binary reader to decode.

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

2009-12-01

135

Thermophoresis and Its Thermal Parameters for Aerosol Collection  

SciTech Connect

The particle collection efficiency of a prototype environmental tobacco smoke (ETS) sampler based on the use of thermophoresis is determined by optimizing the operational voltage that determines its thermal gradient. This sampler's heating element was made of three sets of thermophoretic (TP) wires 25mu m in diameter suspended across a channel cut in a printed circuit board and mounted with collection surfaces on both sides. The separation between the heating element and the room temperature collection surface was determined in a numerical simulation based on the Brock-Talbot model. Other thermal parameters of this TP ETS sampler were predicted by the Brock-Talbot model for TP deposition. From the normalized results the optimal collection ratio was expressed in terms of operational voltage and fi lter mass. Prior to the Brock-Talbot model simulation for this sampler, 1.0V was used arbitrarily. The operational voltage was raised to 3.0V, and the collection effi ciency was increased by a factor of fi ve for both theory and experiment.

Huang, Z.; Apte, Michael; Gundel, Lara

2007-08-01

136

THERMOPHORESIS AND ITS THERMAL PARAMETERS FOR AEROSOL COLLECTION  

SciTech Connect

The particle collection effi ciency of a prototype environmental tobacco smoke (ETS) sampler based on the use of thermophoresis is determined by optimizing the operational voltage that determines its thermal gradient. This sampler’s heating element was made of three sets of thermophoretic (TP) wires 25?m in diameter suspended across a channel cut in a printed circuit board and mounted with collection surfaces on both sides. The separation between the heating element and the room temperature collection surface was determined in a numerical simulation based on the Brock-Talbot model. Other thermal parameters of this TP ETS sampler were predicted by the Brock-Talbot model for TP deposition. From the normalized results the optimal collection ratio was expressed in terms of operational voltage and fi lter mass. Prior to the Brock-Talbot model simulation for this sampler, 1.0V was used arbitrarily. The operational voltage was raised to 3.0V, and the collection effi ciency was increased by a factor of fi ve for both theory and experiment.

Huang, Z.; Apte, M.; Gundel, L.

2007-01-01

137

An assessment of the performance of the Monitor for AeRosols and GAses in ambient air (MARGA): a semi-continuous method for soluble compounds  

NASA Astrophysics Data System (ADS)

Ambient air monitoring as part of the U.S. EPA's Clean Air Status and Trends Network (CASTNet) currently uses filter packs to measure weekly integrated concentrations. The U.S. EPA is interested in supplementing CASTNet with semi-continuous monitoring systems at select sites to examine ecosystem exposure to nitrogen and sulfur compounds at higher time resolution and with greater accuracy than the filter pack. The Monitor for AeRosols and GAses in ambient air (MARGA) measures water-soluble gases and aerosols at hourly temporal resolution. The performance of the MARGA was assessed under the U.S. EPA Environmental Technology Verification (ETV) program. The assessment was conducted in Research Triangle Park, NC from September 8th-October 8th, 2010. Precision of the MARGA was evaluated by comparing duplicate units and accuracy was evaluated by comparing duplicate MARGAs to duplicate reference denuder/filter packs. The MARGA utilizes a Wet Rotating Denuder (WRD) to collect gases, while aerosols are collected by a Steam Jet Aerosol Collector (SJAC). Both the WRD and the SJAC produce aqueous sample streams, which are analyzed by online ion chromatography for anions and cations. The reference denuder/filter pack consisted of sodium carbonate (Na2CO3) and phosphorous acid (H3PO3) coated denuders followed by a Teflon filter, a nylon filter, and a citric acid coated cellulose filter. The assessment of the MARGA units focused on gaseous SO2, HNO3 and NH3 and aerosol SO4-, NO3- and NH4+. To evaluate accuracy, hourly MARGA concentrations were averaged over 12 hours to match with 12-hour integrated concentrations from the reference system. The concentrations were compared using linear regression with performance goals of slope between 0.8-1.2 and y-intercept between -10 ppb and 10 ppb. Accuracy was further quantified as the median absolute relative percent difference (MARPD) between 12-hour MARGA and reference concentrations, with a performance goal of ? 40%. The precision of the MARGA units was evaluated by calculating the MARPD between the corresponding 1 hour concentrations from the two MARGA units, also with a performance goal of ? 40%. The MARGA units performed well for SO2, SO4-, NH3 and NH4+, with these compounds meeting the accuracy and precision goals. The MARGA units did not perform as well for HNO3 and NO3-, with both species linear regression slopes not achieving the accuracy target. Furthermore, for NO3-, the MARPD between both MARGA units and the reference filter pack was greater than 40%. Comparison of total nitrate (HNO3 + NO3-) suggests that the lesser performance of the MARGA units for these compounds likely results from aerosol volatility in the MARGA inlet/tubing or the reference filter pack and exchange of HNO3 with tubing walls. In addition, the NO3- concentrations were low (<0.5 ug m-3) for significant periods of the ETV assessment. Details of the comparison will be examined and suggested instrument improvements will be discussed.

Rumsey, I. C.; Cowen, K.; Kelly, T.; Hanft, E.; Mishoe, K.; Rogers, C.; Proost, R.; Lear, G.; Frelink, T.; Walker, J. T.

2011-12-01

138

Size-selective nonrefractory ambient aerosol measurements during the Particulate Matter Technology Assessment and Characterization Study–New York 2004 Winter Intensive in New York City  

Microsoft Academic Search

During the Particulate Matter Technology Assessment and Characterization Study–New York (PMTACS-NY) in January\\/February 2004 a variety of modern aerosol measurement instruments were deployed at a field site on the campus of Queens College in Queens, New York. These instruments included the Aerodyne Aerosol Mass Spectrometer (Q-AMS), R&P Particulate Ambient Sulfate and Nitrate monitors (8400S&N), a Particle-into-liquid Sampler equipped with ion

Silke Weimer; Frank Drewnick; Olga Hogrefe; James J. Schwab; Kevin Rhoads; Douglas Orsini; Manjula Canagaratna; Douglas R. Worsnop; Kenneth L. Demerjian

2006-01-01

139

Using Thermal-Optical Analysis to Examine the OC-EC Split that Characterizes Ambient and Source Emissions Aerosols  

NASA Astrophysics Data System (ADS)

Thermal-optical analysis (TOA) is typically used to measure OC-EC (organic carbon-elemental carbon) ratio in atmospheric aerosols. The present study utilizes a single dual-optics carbon aerosol analyzer to examine the effects of temperature-programming and optics on the OC-EC ratios. The OC-EC ratios for a variety of atmospheric and source emissions aerosols were measured using a National Institute of Occupational Safety and Health method (NIOSH 5040), the Interagency Monitoring of Protected Visual Environments method (IMPROVE), and a modified NIOSH 5040 method (referred in this paper as NIST-EPA). Use of the dual-optics instrument allowed simultaneous monitoring of the reflectance (TOR) and transmission (TOT) during each thermal protocol. Results showed no statistical difference between NIST-EPA and NIOSH OC-EC ratios for residential cookstove emissions and for an urban aerosol collected in Nairobi, Kenya. However, the OC-EC ratios for diesel exhaust (NIST [TOT and TOR]) and for a denuded rural North Carolina forest aerosol (NIST [TOT]) were significantly greater than the corresponding NIOSH values. Significantly lower IMPROVE (TOT and TOR) OC-EC ratios, compared to NIST-EPA and NIOSH, may be ascribed to the lower temperature protocol of this method. The ratio of TOT-to-TOR for the OC-EC ratio ranged between 1.37 - 1.71 (residential cookstoves), 1.05 - 1.24 (diesel exhaust), 1.63 - 2.23 (rural), and 0.80 - 1.12 (urban) for the three methods. Aerosols containing components susceptible to charring (such as water soluble organic compounds typical of rural and cookstove aerosols) tend to show the higher OC-EC variability among the methods when compared to diesel-impacted aerosols, which showed little to no detectable pyrolyzed carbon (PyC). Different sample types, due to their various chemical compositions, behave differently under dissimilar thermal and optical conditions, such that the search for a “universal” thermal-optical method for all sample types remain indeterminate until a suitable standard for OC and EC particulate in atmospheric aerosols can be developed.

Khan, B.; Hays, M. D.; Geron, C.; Jetter, J.

2010-12-01

140

Water-soluble material on aerosols collected within volcanic eruption clouds ( Fuego, Pacaya, Santiaguito, Guatamala).  

USGS Publications Warehouse

In Feb. and March of 1978, filter samplers mounted on an aircraft were used to collect the aerosol fraction of the eruption clouds from three active Guatemalan volcanoes (Fuego, Pacaya, and Santiaguito). The elements dissolved in the aqueous extracts represent components of water-soluble material either formed directly in the eruption cloud or derived from interaction of ash particles and aerosol components of the plume. Calculations of enrichment factors, based upon concentration ratios, showed the elements most enriched in the extracts relative to bulk ash composition were Cd, Cu, V, F, Cl, Zn, and Pb.-from Authors

Smith, D. B.; Zielinski, R. A.; Rose, Jr, W. I.; Huebert, B. J.

1982-01-01

141

Photoacoustic and filter-based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity  

NASA Astrophysics Data System (ADS)

Ambient measurements are reported of aerosol light absorption from photoacoustic and filter-based instruments (aethalometer and a particle soot absorption photometer (PSAP)) to provide insight on the measurement science. Measurements were obtained during the Big Bend Regional Aerosol and Visibility Observational Study at the Big Bend National Park in South Texas. The aethalometer measurements of black carbon concentration at this site correlate reasonably well with photoacoustic measurements of aerosol light absorption, with a slope of 8.1 m2/g and a small offset. Light absorption at this site never exceeded 2.1 Mm-1 during the month of collocated measurements. Measurements were also obtained, as a function of controlled relative humidity between 40% and 90%, during the Photoacoustic IOP in 2000 at the Department of Energy Southern Great Plains Cloud and Radiation Testbed site (SGP). PSAP measurements of aerosol light absorption correlated very well with photoacoustic measurements, but the slope of the correlation indicated the PSAP values were larger by a factor of 1.61. The photoacoustic measurements of light absorption exhibited a systematic decrease when the RH increased beyond 70%. This apparent decrease in light absorption with RH may be due to the contribution of mass transfer to the photoacoustic signal. Model results for the limiting case of full water saturation are used to evaluate this hypothesis. A second PSAP measured the light absorption for the same humidified samples, and indicated very erratic response as the RH changed, suggesting caution when interpreting PSAP data under conditions of rapid relative humidity change.

Arnott, W. P.; Moosmüller, H.; Sheridan, P. J.; Ogren, J. A.; Raspet, R.; Slaton, W. V.; Hand, J. L.; Kreidenweis, S. M.; Collett, J. L.

2003-01-01

142

Advanced Analytical Microscopy Techniques for the Characterization of Ambient Particulate Matter Collected From Military Bases in the Middle East  

Microsoft Academic Search

The Enhanced Particulate Matter Surveillance Program was initiated to help environmental health professionals evaluate sources of particulate matter and to assess potential health effects of troop exposure to air pollutants within the US Central Command Area of Responsibility (AOR). The study examined the concentrations and physical properties of ambient particulate matter collected at 15 deployment locations within the AOR. Ambient

G. S. Casuccio; T. L. Lersch; K. L. Bunker; B. S. Strohmeier

2008-01-01

143

Molecular characterization of marine organic aerosols collected during a round-the-world cruise  

NASA Astrophysics Data System (ADS)

Organic molecular compositions of marine aerosol samples, collected at low latitudes to midlatitudes in the Northern Hemisphere during a round-the-world cruise, were studied using gas chromatography/mass spectrometry. More than 140 organic species were detected in the samples and were grouped into different compound classes based on the functionality and sources. The concentrations of total quantified organics ranged from 0.94 to 111 ng m-3 (average of 34 ng m-3). Biogenic secondary organic aerosol (SOA) tracers from the oxidation of isoprene (e.g., 2-methyltetrols), ?/?-pinene (e.g., pinonic and pinic acids), and ?-caryophyllene (?-caryophyllinic acid) were detected in all the samples. Their total concentrations ranged from 0.19 to 27 ng m-3, which account for 0.48-29% of the total identified organics and 0.05-1.5% of organic carbon in the marine aerosols. The spatial distributions of biogenic SOA tracers exhibited higher loadings over the coastal/tropical regions than the open oceans. In marine aerosols collected over the North Pacific and North Atlantic, the contributions of marine natural emissions (22-33%) were higher than those in the coastal regions (4-14%). Over the tropical regions, atmospheric oxidation products can account for 47-59% of the total organics, with biomass burning emissions of only 1-2%. However, over the western North Pacific, fossil fuel combustion (26%), atmospheric oxidation products (25%), and biomass burning (24%) were the main sources. This study indicates that long-range atmospheric transport of continental aerosols and sea-to-air emission of marine organics, as well as atmospheric oxidation and/or photochemical aging, are important factors controlling the chemical composition of organic aerosols in the marine atmosphere.

Fu, Pingqing; Kawamura, Kimitaka; Miura, Kazuhiko

2011-07-01

144

AMBIENT AMMONIA AND AMMONIUM AEROSOL ACROSS A REGION OF VARIABLE AMMONIA EMISSION DENSITY  

EPA Science Inventory

The paper presents one year of ambient ammonia (NH3), ammonium (NH4+), hydrochloric acid (HCI), chloride (CI¯), nitric acid (HNO3), nitrate (NO3¯), nitrous acid (HONO), sulfur dioxide (SO2), and sulfate (SO4...

145

Inflammatory Cytokine Response to Ambient Particles Varies due to Field Collection Procedures  

PubMed Central

In vitro assays of biological activity induced by particulate matter (PM) are a tool for investigating mechanisms of PM health effects. They have potential application to exposure assessment in chronic disease epidemiology. However, there has been little reporting of the impact of real-world PM collection techniques on assay results. Therefore, we examined the effect of sampling duration and postsampling delays in freezing on PM-induced biological activity. Duplicate samples of respirable ambient Los Angeles PM were collected on polyurethane foam filters during 17 days and during three contemporaneous consecutive shorter periods. After collection, one duplicate was stored at ambient temperature for 24 hours before freezing; the other was frozen immediately. Cytokine response (IL-1?, IL-6, IL-8, and TNF-?) to PM aqueous extract was assessed in THP-1 cells, a model for evaluating monocyte/macrophage lineage cell responses. There was consistent 3- to 4-fold variation in PM-induced cytokine levels across the three collection intervals. Compared with levels induced by PM pooled across the three periods, continuously collected PM-induced levels were reduced by 25% (IL-6) to 39% (IL-8). The pattern of cytokine gene expression response was similar. Cytokine level variation by time to freezing was not statistically significant. PM-induced inflammatory response varied substantially over a weekly time scale. We conclude that long PM sampling interval induced less activity than the average of equivalent shorter consecutive sampling intervals. Time to freezing was less important. Implications for development of metrics of long-term spatial variation in biological exposure metrics for study of chronic disease merit further investigation.

Wu, Weidong; Berhane, Kiros; Liu, Feifei; Verma, Gaurav; Peden, David; Diaz-Sanchez, David; Fruin, Scott

2013-01-01

146

TEM study of soot, organic aerosol, and sea-salt particles collected during CalNex  

NASA Astrophysics Data System (ADS)

Anthropogenic aerosol particles are emitted in abundance from megacities. Those particles can have important effects on both human health and climate. In this study, aerosol particles having aerodynamic diameters between 50 and 300 nm were collected during the CalNex campaign at the Pasadena ground site from May 15 to June 15, 2010, ~15 km northeast of downtown Los Angeles. The samples were analyzed using transmission electron microscopes (TEMs) to characterize particle shapes and compositions. Most samples are dominated by soot, organic aerosol (OA), sulfate, sea salt, or combinations thereof. Sizes and amounts of OA particles increased during the afternoons, and most soot particles were internally mixed with OA and sulfate in the afternoons. The proportion of soot to other material in individual particles increased and soot particles were more compact during the nights and early mornings. Sea-salt particles were commonly internally mixed with other materials. They have high Na contents with lesser N, Mg, S, K, and Ca and almost no Cl, suggesting that the Cl was replaced by sulfate or nitrate in the atmosphere. There is less OA and more sea salt and sulfate in the CalNex samples than in the samples from Mexico City that were collected during the MILAGRO campaign. Our study indicates that compositions of internally mixed aerosol particles and shapes of soot particles change significantly within a day. These changes probably influence the estimates of their effects on human health and climate.

Adachi, K.; Buseck, P. R.

2010-12-01

147

Library Optimization in EDXRF Spectral Deconvolution for Multi-element Analysis of Ambient Aerosols  

EPA Science Inventory

In multi-element analysis of atmospheric aerosols, attempts are made to fit overlapping elemental spectral lines for many elements that may be undetectable in samples due to low concentrations. Fitting with many library reference spectra has the unwanted effect of raising the an...

148

From molecular clusters to nanoparticles: Role of ambient ionization in tropospheric aerosol formation  

Microsoft Academic Search

We investigate the role of background ionization, associated mainly with galactic cosmic radiation, in the generation and evolution of ultrafine particles in the marine boundary layer. We follow the entire course of aerosol evolution, from the initial buildup of molecular clusters (charged and uncharged) through their growth into stable nanoparticles. The model used for this purpose is based on a

Fangqun Yu; Richard P. Turco

2001-01-01

149

AMBIENT SULFATE AEROSOL DEPOSITION IN MAN: MODELING THE INFLUENCE OF HYGROSCOPICITY  

EPA Science Inventory

Atmospheric sulfate aerosols (H2SO4, (NH4)2SO4, and NH4HSO4) are of international concern because of their global prevalence and potential irritant or toxic effects on humans. To assess hazards following inhalation exposure, the total dose delivered to the human respiratory tract...

150

SMOG CHAMBER STUDIES OF SECONDARY ORGANIC AEROSOLS FROM IRRADIATED HYDROCARBONS UNDER AMBIENT CONDITIONS  

EPA Science Inventory

Understanding the physics and chemistry of aerosols is fundamental to evaluating health risks and developing and evaluating atmospheric models. However, as noted in a recent NRC report only about 10% of the organics in PM2.5 have been identified. A significant portion of the un...

151

GROWTH LAWS FOR THE FORMATION OF SECONDARY AMBIENT AEROSOLS: IMPLICATIONS FOR CHEMICAL CONVERSION MECHANISMS  

EPA Science Inventory

The evolution of aerosol size distributions growing by gas-to-particle conversion has been observed recently in field and laboratory studies. A technique for extracting particle diameter growth rates from such data is presented. The functional dependence of these growth rates on ...

152

Particle size characteristics of levoglucosan in ambient aerosols from rice straw burning  

Microsoft Academic Search

Agricultural residue burning in Asia is an important source of atmospheric aerosol particles. This study investigates the impact of post-harvest burning of rice fields on the air quality in Taiwan, a subtropical island in East Asia. Size-resolved measurements of the anhydrosugar levoglucosan (biomass burning tracer derived from the thermal breakdown of cellulose) were conducted before, during and after an episode

James J. Lee; Guenter Engling; Shih-Chun Candice Lung; Kuo-Yang Lee

2008-01-01

153

Characterization of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique  

NASA Astrophysics Data System (ADS)

Haze is an atmospheric phenomenon that leads to low visibility, and is mostly due to elevated levels of fine particulate matter. It can have effects on cloud formation, public health, agriculture, and even the global climate. Although urban haze has been increasing in occurrence over the past several years over the Seoul-Incheon metropolis, Korea, studies of the morphology and chemical composition of ambient aerosol particles by single-particle analysis during haze episodes have rarely been conducted. Herein, a quantitative energy-dispersive electron probe microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyze individual aerosol particles collected in Incheon, Korea on 13-18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall, 3600 particles in 12 aerosol samples collected on haze and non-haze days were measured by low-Z particle EPMA. Based on quantitative X-ray analysis, together with secondary electron images of individual particles, we successfully identified the aerosol particle types as follows: elemental carbon (EC), organic carbon (OC), (NH4)2SO4/NH4HSO4-containing, genuine (fresh) and reacted (aged) sea-salt, mineral dust (such as aluminosilicate, SiO2, CaCO3/CaMg(CO3)2, etc.), and K-containing, Fe-rich, and fly ash particles. By analyzing the relative abundances of different particle types, it was concluded that (a) on non-haze days, reacted sea-salts and reacted mineral dust particles were abundant in both the PM2.5-10 and PM1.0-2.5 fractions (with relative abundances of 65.0% and 57.7%, respectively); whereas on haze days, the relative abundances of OC and (NH4)2SO4/NH4HSO4-containing particles were significantly elevated, indicating that organic matter and secondary aerosols were abundant in the atmosphere when haze occurred. (b) in PM2.5-10 fractions, sea-salt and mineral dust particles reacted with NOx/HNO3 significantly outnumbered those reacted with SO2/H2SO4, no matter whether they were collected on haze or non-haze days; but in PM1.0-2.5 fractions on non-haze days, the nitrate-containing reacted particles significantly outnumbered the sulfate-containing ones, whereas it was the reverse on haze days, implying that on haze days there were special sources or formation mechanisms for the reacted fine aerosol particles (aerodynamic diameter<2.5 ?m). It is hypothesized that motor vehicles, biomass burning from the areas surrounding Incheon, and haze transported from Eastern China are the major contributors to urban haze formation in Incheon under stagnant meteorological conditions such as low wind speed, high relative humidity, etc.

Geng, H.; Ryu, J.; Maskey, S.; Jung, H.-J.; Ro, C.-U.

2010-11-01

154

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6)  

NASA Astrophysics Data System (ADS)

Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l.) during the Cloud and Aerosol Characterization Experiment (CLACE 6) in February and March 2007. During mixed phase cloud events ice crystals from 5 ?m up to 20 ?m were separated from large ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI). During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The resulting ice and droplet residues (IR and DR) were analyzed for size and composition by two single particle mass spectrometers: a custom-built Single Particle Laser-Ablation Time-of-Flight Mass Spectrometer (SPLAT) and a commercial Aerosol Time of Flight Mass Spectrometer (ATOFMS, TSI Model 3800). During CLACE 6 the SPLAT instrument characterized 355 individual ice residues that produced a mass spectrum for at least one polarity and the ATOFMS measured 152 particles. The mass spectra were binned in classes, based on the combination of dominating substances, such as mineral dust, sulfate, potassium and elemental carbon or organic material. The derived chemical information from the ice residues is compared to the JFJ ambient aerosol that was sampled while the measurement station was out of clouds (several thousand particles analyzed by SPLAT and ATOFMS) and to the composition of the residues of supercooled cloud droplets (SPLAT: 162 cloud droplet residues analyzed, ATOFMS: 1094). The measurements showed that mineral dust particles were strongly enhanced in the ice particle residues. 57% of the SPLAT spectra from ice residues were dominated by signatures from mineral compounds, and 78% of the ATOFMS spectra. Sulfate and nitrate containing particles were strongly depleted in the ice residues. Sulfate was found to dominate the droplet residues (~90% of the particles). The results from the two different single particle mass spectrometers were generally in agreement. Differences in the results originate from several causes, such as the different wavelength of the desorption and ionisation lasers and different size-dependent particle detection efficiencies.

Kamphus, M.; Ettner-Mahl, M.; Drewnick, F.; Keller, L.; Cziczo, D. J.; Mertes, S.; Borrmann, S.; Curtius, J.

2009-07-01

155

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6)  

NASA Astrophysics Data System (ADS)

Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l.) during the Cloud and Aerosol Characterization Experiment (CLACE 6) in February and March 2007. During mixed phase cloud events ice crystals from 5-20 ?m were separated from larger ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI). During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The resulting ice and droplet residues (IR and DR) were analyzed for size and composition by the two single particle mass spectrometers: a custom-built Single Particle Laser-Ablation Time-of-Flight Mass Spectrometer (SPLAT) and a commercial Aerosol Time-of-Flight Mass Spectrometer (ATOFMS, TSI Model 3800). During CLACE 6 the SPLAT instrument characterized 355 individual IR that produced a mass spectrum for at least one polarity and the ATOFMS measured 152 IR. The mass spectra were binned in classes, based on the combination of dominating substances, such as mineral dust, sulfate, potassium and elemental carbon or organic material. The derived chemical information from the ice residues is compared to the JFJ ambient aerosol that was sampled while the measurement station was out of clouds (several thousand particles analyzed by SPLAT and ATOFMS) and to the composition of the residues of supercooled cloud droplets (SPLAT: 162 cloud droplet residues analyzed, ATOFMS: 1094). The measurements showed that mineral dust was strongly enhanced in the ice particle residues. Close to all of the SPLAT spectra from ice residues did contain signatures from mineral compounds, albeit connected with varying amounts of soluble compounds. Similarly, close to all of the ATOFMS IR spectra show a mineral or metallic component. Pure sulfate and nitrate containing particles were depleted in the ice residues. Sulfate and nitrate was found to dominate the droplet residues (~90% of the particles). The results from the two different single particle mass spectrometers were generally in agreement. Differences in the results originate from several causes, such as the different wavelength of the desorption and ionisation lasers and different size-dependent particle detection efficiencies.

Kamphus, M.; Ettner-Mahl, M.; Klimach, T.; Drewnick, F.; Keller, L.; Cziczo, D. J.; Mertes, S.; Borrmann, S.; Curtius, J.

2010-08-01

156

A novel rocket-based in-situ collection technique for mesospheric and stratospheric aerosol particles  

NASA Astrophysics Data System (ADS)

A technique for collecting aerosol particles between altitudes of 85 and 17 km is described. Collection probes are ejected from a sounding rocket allowing for multi-point measurements. Each probe is equipped with 110 collection samples that are 3 mm in diameter. The collection samples are one of three types: standard transmission electron microscopy carbon grids, glass fibre filter paper or silicone gel. Each collection sample is exposed over a 50 m to 5 km height range with a total of 45 separate ranges. Post-flight electron microscopy gives size-resolved information on particle number, shape and elemental composition. Each collection probe is equipped with a suite of sensors to capture the probe's status during the fall. Parachute recovery systems along with GPS-based localization ensure that each probe can be located and recovered for post-flight analysis.

Reid, W.; Achtert, P.; Ivchenko, N.; Magnusson, P.; Kuremyr, T.; Shepenkov, V.; Tibert, G.

2012-11-01

157

A study of the physical, chemical, and optical properties of ambient aerosol particles in Southeast Asia during hazy and nonhazy days  

Microsoft Academic Search

Many Southeast Asian countries have been constantly plagued by recurring smoke haze episodes as a result of traditional slash-and-burn practices in agricultural areas to clear crop lands or uncontrolled forest fires. However, our current knowledge on the physiochemical and optical properties of ambient aerosols associated with regional haze phenomenon is still fairly limited. Therefore a comprehensive field study was carried

S. W. See; R. Balasubramanian; W. Wang

2006-01-01

158

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED PARTICLES FOR DIFFERENT DOSE METRICS: COMPARISON OF NUMBER, SURFACE AREA AND MASS DOSE OF TYPICAL AMBIENT BI-MODAL AEROSOLS  

EPA Science Inventory

ANALYSIS OF RESPIRATORY DEPOSITION OF INHALED PARTICLES FOR DIFFERENT DOSE METRICS: COMPARISON OF NUMBER, SURFACE AREA AND MASS DOSE OF TYPICAL AMBIENT BI-MODAL AEROSOLS. Chong S. Kim, SC. Hu*, PA Jaques*, US EPA, National Health and Environmental Effects Research Laboratory, ...

159

Contribution of wood combustion in winter submicron ambient aerosols over Athens  

NASA Astrophysics Data System (ADS)

Given that a smog pollution problem, mostly attributed to wood burning in fireplaces and stoves, is currently emerging in the Athens metropolitan area, several monitoring instruments were deployed at the National Observatory of Athens facilities in the region of Thissio, downtown Athens . These included an Aerodyne Aerosol Chemical Speciation Monitor with 30 minute time resolution and a Particle Into Liquid Sampler coupled with Ion Chromatography with 15 minute time resolution. The campaign duration was from December 2013 to February 2014 and the aim was to investigate the chemical composition of ultrafine aerosols connected to biomass burning.. Many events of high particulate matter concentrations (exceeding the 50 ?g/m3 daily limit) were observed during night-time, with maximum concentrations occurring when stagnant atmospheric conditions prevailed. Potassium measured by the PILS - IC, and the m/z = 60 fragment measured by the ACSM, was initially used as a tracer of biomass burning events. A good correlation was determined for those two factors, allowing for safe conclusions concerning the identification of these aforementioned biomass burning events. For utmost certainty, Black Carbon measurements coming from three different instruments, was also used. As a second step, Positive Matrix Factorization analysis was performed, using the SoFi interface, which utilizes the generalized multilinear engine (ME-2) (Canonaco et Al., Atmos. Meas. Tech., 6, 3649-3661, 2013), for the source apportionment of the organic particulate matter, determined by the ACSM. This analysis revealed a very important Biomass Burning Organic Aerosol (BBOA) factor with a clear diurnal cycle, showing maxima in the time interval from 21:00 in the evening to 02:00 in the morning. A Hydrocarbon-like Organic Aerosol (HOA) factor is also present with a maximum during the same time interval, attributed to fossil fuel used in central heating systems, and a secondary maximum during the day, attributed to city traffic. Two more factors were determined, an Oxygenated Organic Aerosol (OOA) factor implying processing in the atmosphere and a minor Cooking Organic Aerosol (COA) factor.¬

Stavroulas, Iasonas; Fourtziou, Luciana; Zarmpas, Pavlos; Bougiatioti, Aikaterini; Liakakou, Eleni; Sciare, Jean; Mihalopoulos, Nikos

2014-05-01

160

Organic analysis of ambient samples collected near Tank 241-C-103: Results from samples collected on May 12, 1994  

SciTech Connect

This report describes organic analyses results from ambient samples collected both upwind and through the vapor sampling system (VSS) near Hanford waste storage Tank 241-C-103 (referred to as Tank C-103). The results described here were obtained to support safety and toxicological evaluations. A summary of the results for inorganic and organic analytes is listed. Quantitative results were obtained for organic compounds. Five organic tentatively identified compounds (TICS) were observed above the detection limit of (ca.) 10 ppbv, but standards for most of these were not available at the time of analysis, and the reported concentrations are semiquantitative estimates. In addition, we looked for the 40 standard TO-14 analytes. We observed 39. Of these, only one was observed above the 2-ppbv calibrated instrument detection limit. Dichloromethane was above the detection limits using both methods, but the result from the TO-14 method is traceable to a standard gas mixture and is considered more accurate. Organic analytes were found only in the sample collected through the VSS, suggesting that these compounds were residual contamination from a previous sampling job. Detailed descriptions of the results appear in the text.

Clauss, T.W.; Ligotke, M.W.; McVeety, B.D.; Lucke, R.B.; Young, J.S.; McCulloch, M.; Fruchter, J.S.; Goheen, S.C.

1995-06-01

161

Evaluation of Computer-Controlled Scanning Electron Microscopy Applied to an Ambient Urban Aerosol Sample  

Microsoft Academic Search

Concerns about the environmental and public health effects of particulate matter (PM) have stimulated interest in analytical techniques capable of measuring the size and chemical composition of individual aerosol particles. Computer-controlled scanning electron microscopy (CCSEM) coupled with energy-dispersive X-ray analysis (EDX) allows automated analysis of particle size, chemistry, and particle classification. In combination with manual SEM and bulk analytical techniques

Yaacov Mamane; Robert Willis; Teri Conner

2001-01-01

162

Chemical Analysis of Fractionated Halogens in Atmospheric Aerosols Collected in Okinawa, Japan  

NASA Astrophysics Data System (ADS)

Halogens (Cl, Br and I) play important roles in the atmosphere, e.g. ozone depletion by Br during spring in Polar Regions. Sources of halogens in atmospheric aerosols are mainly from ocean. But, for example, when we analyzed Br- with ion chromatography, its concentrations were almost always below the detection limit, which is also much lower than the estimated concentrations from sodium ion concentrations. We hypothesized that portions of halogens are escaped to the atmosphere, similar to chlorine loss, changed their chemical forms to such as BrO3- and IO3-, and/or even formed precipitates. There was few reported data so far about fractionated halogen concentrations in atmospheric aerosols. Thus, purpose of this study was to determine halogen concentrations in different fractions; free ion, water-soluble chemically transformed ions and precipitates using the authentic aerosols. Moreover, we analyzed seasonal variation for each fraction. Atmospheric aerosol samples were collected at Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) of Okinawa, Japan during January 2010 and August 2013. A high volume air sampler was used for collecting total particulate matters on quartz filters on a weekly basis. Ultrapure water was used to extract water-soluble factions of halogens. The extracted solutions were filtered with the membrane filter and used for chemical analysis with ion chromatography and ICP-MS. Moreover, the total halogens in aerosols were obtained after digesting aerosols with tetramethylammonium hydroxide (TMAH) using the microwave and analysis with ICP-MS. For Cl, water-soluble Cl- accounted for about 70% of the estimates with Na content. No other forms of water-soluble Cl were found. About 30% of Cl was assumed volatilized to the gas-phase. For Br, water-soluble Br accounted for about 43% of the estimates with Na content, and within the 43%, about 10% of Br was not in the form of Br-. About 46% of Br was assumed volatilized to the gas-phase. For I, fractioned concentrations are still under investigation, and will be reported and discussed during the meeting. For seasonal variation, in general, concentrations of halogens were the lowest in summer and higher in fall and winter, reflecting air mass movement and wind speed around Okinawa, Japan.

Tsuhako, A.; Miyagi, Y.; Somada, Y.; Azechi, S.; Handa, D.; Oshiro, Y.; Murayama, H.; Arakaki, T.

2013-12-01

163

Raman microscopy of size-segregated aerosol particles, collected at the Sonnblick Observatory in Austria  

NASA Astrophysics Data System (ADS)

Size classified aerosol samples were collected using low pressure impactors in July 2013 at the high alpine background site Sonnnblick. The Sonnblick Observatory is located in the Austrian Alps, at the summit of Sonnblick 3100 m asl. Sampling was performed in parallel on the platform of the Observatory and after the aerosol inlet. The inlet is constructed as a whole air inlet and is operated at an overall sampling flow of 137 lpm and heated to 30 °C. Size cuts of the eight stage low pressure impactors were from 0.1 to 12.8 µm a.d.. Alumina foils were used as sample substrates for the impactor stages. In addition to the size classified aerosol sampling overall aerosol mass (Sharp Monitor 5030, Thermo Scientific) and number concentrations (TSI, CPC 3022a; TCC-3, Klotz) were determined. A Horiba LabRam 800HR Raman microscope was used for vibrational mapping of an area of about 100 µm x 100 µm of the alumina foils at a resolution of about 0.5 µm. The Raman microscope is equipped with a laser with an excitation wavelength of 532 nm and a grating with 300 gr/mm. Both optical images and the related chemical images were combined and a chemometric investigation of the combined images was done using the software package Imagelab (Epina Software Labs). Based on the well-known environment, a basic assignment of Raman signals of single particles is possible at a sufficient certainty. Main aerosol constituents e.g. like sulfates, black carbon and mineral particles could be identified. First results of the chemical imaging of size-segregated aerosol, collected at the Sonnblick Observatory, will be discussed with respect to standardized long-term measurements at the sampling station. Further, advantages and disadvantages of chemical imaging with subsequent chemometric investigation of the single images will be discussed and compared to the established methods of aerosol analysis. The chemometric analysis of the dataset is focused on mixing and variation of single compounds at different stages of the impactors.

Ofner, Johannes; Kasper-Giebl, Anneliese; Kistler, Magdalena; Matzl, Julia; Schauer, Gerhard; Hitzenberger, Regina; Lohninger, Johann; Lendl, Bernhard

2014-05-01

164

Trace metal concentration in Trade Wind aerosols collected over Barbados and Miami.  

NASA Astrophysics Data System (ADS)

African mineral dust aerosols are transported by trade winds to Barbados and often reach Miami. The trace metals contained in these aerosols play an important role in biogeochemical processes and thus the global carbon cycle. High-volume bulk aerosols were collected in the summer dust season (June-September) of 2003 and 2004 in Miami and Barbados on Whatman-41 filters and microwave digested using a modified version of EPA method 3051. Aliquots of digested samples were tested for trace metal concentrations by ICP-MS. Excellent agreement with gravimetrically determined ashed weights was observed with dust concentrations calculated based on Al crustal abundance. As a major component, aluminum averaged 8.7% content in agreement to 8.1% crustal abundance, and was used to examine other trace metals. Al, Fe, V, Cr, Mn, Cu, Co, Ni, Zn, As, Tl, Ba, Cd, Pb and REE's were examined and deviations from average crustal abundance are discussed in relationship to temporal variation and meteorological conditions. In addition, trace metal pollutants in Miami aerosols were examined relative to the relatively clean samples offered by Barbados.

Trapp, J. M.; Millero, F. J.; Prospero, J. M.

2007-12-01

165

COMPARISON OF TWO PARTICLE-SIZE SPECTROMETERS FOR AMBIENT AEROSOL MEASUREMENTS. (R827354C002)  

EPA Science Inventory

There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for human health effects observed in epidemiological studies. Since there is no single instrument available for the measurement of the particle-size distribution over ...

166

Seasonal air quality profile of size-segregated aerosols in the ambient air of a central Indian region.  

PubMed

Seasonal distribution trends of size-segregated aerosols i.e. submicron (PM1), fine (PM2.5) and coarse (PM2.5-10) and their relationship with meteorological variables employing correlation analysis were studied in the ambient air of central India from July 2009 to June 2010. The annual mean concentrations of PM1, PM2.5 and PM2.5-10 were found to be 65.7, 135.0 and 118.5 ?g m(-3), respectively. The annual mean PM2.5 concentration is three times higher than the National Ambient Air Quality Standards of India (NAAQS). Higher concentrations of PM1, PM2.5 and PM2.5-10 were found during winter due to enormous biomass burning especially during night time due to the use of combustible goods like fire wood and dung cake in the open space by the peoples to keep themselves warm and lower concentrations were observed during monsoon when there were high precipitations. PM2.5 showed high positive correlation with PM1 (r = 0.69) and moderate correlation with PM2.5-10 indicating that variation in PM2.5 mass is governed by the variation in PM1 mass or vice versa. PMID:24129422

Deshmukh, Dhananjay K; Deb, Manas K; Verma, Devsharan; Nirmalkar, Jayant

2013-12-01

167

Impact of Relative Humidity and Collection Media on Mycobacteriophage D29 Aerosol  

PubMed Central

This study was conducted to evaluate the effect of aerosol generation, methods of sampling, storage conditions, and relative humidity on the culturability of the mycobacteriophage D29. The lytic phage D29 can kill Mycobacterium tuberculosis, and the phage aerosol can be treated as a potential tool for tuberculosis treatment. The culturability of D29 was tested using a test chamber designed for the bioaerosols research against three spray liquids (deionized water, phosphate-buffered saline [PBS], and normal saline), four collection media (suspension medium [SM], nutrient broth, PBS, and deionized water), two sampling systems (the all-glass impinger AGI-30 and the Biosampler) and across a range of humidities (20 to 90%). The effect of storage conditions on the culturability of collected sample was also evaluated for the AGI-30 impinger. The results proved that viable phage D29 particles generated by deionized water were approximately 30- and 300-fold higher than PBS and normal saline, respectively. As collection media, SM buffer and nutrient broth were observed to yield a higher number of plaques compared to PBS and deionized water. No difference was observed in collection efficiency between AGI-30 and Biosampler with two detection methods (culture-based technique and real-time PCR). The culturability of collected D29 in SM buffer or nutrient broth can be maintained up to 12 h irrespective of storage temperature. Relative humidity was found to strongly influence airborne D29 culturability which is 2- to 20-fold higher in low humidity (25%) than medium (55%) or high (85%) humidity. This research will help identify the optimal means for the application of D29 aerosol in animal inhalation experiments.

Liu, Keyang; Wen, Zhanbo; Li, Na; Yang, Wenhui; Wang, Jie; Hu, Lingfei; Dong, Xiaokai; Lu, Jianchun

2012-01-01

168

Characterisation of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique  

Microsoft Academic Search

A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyse individual aerosol particles collected in Incheon, Korea on 13-18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall 3600 individual particles in PM2.5-10 and PM1.0-2.5 fractions from 12 aerosol samples collected on haze and non-haze days were analysed. The analysed

H. Geng; J. Y. Ryu; S. Maskey; H.-J. Jung; C.-U. Ro

2011-01-01

169

Particle morphologies and formation mechanisms of fine volcanic ash aerosol collected from the 2006 eruption of Augustine Volcano, Alaska  

NASA Astrophysics Data System (ADS)

Fine volcanic ash aerosol (35-0.09um) erupted in 2006 by Augustine Volcano, southwest of Anchorage, Alaska was collected by a DRUM cascade impactor and analyzed by scanning electron microscopy for individual particle chemistry and morphology. Results of these analyses show ash particles occur as either individual glass shard and mineral phase (plagioclase, magnetite, ilmenite, hornblende, etc.) particles or aggregates thereof. Individual glass shard ash particles are angular, uniformly-sized, consist of calc-alkaline whole-rock elements (Si, Al, Fe, Na, and Ca) and are not collocated on the sample media with non-silicate, Cl and S bearing sea salt particles. Aggregate particles occur as two types: pure ash aggregates and sea salt-cored aggregates. Pure ash aggregates are made up of only ash particles and contain no other constituents. Sea salt-cored aggregates are ash particles commingled with sea salts. Determining the formation processes of the different ash particle types need further investigation but some possibilities are proposed here. Individual ash particles may exist when the ambient air is generally dry, little electrical charge exists on ash particles, the eruptive cloud is generally dry, or the number of individual particles exceeds the scavenging capacity of the water droplets present. Another possibility is that ash aggregates may break apart as relative humidity drops over time and causes ash-laden water droplets to evaporate and subsequently break apart. Pure ash aggregates may form when the ambient air and plume is relatively dry but the ash has a significant charge to cause ash to aggregate. Or they could form during long-range transport when turbulent or Brownian motion can cause ash particles to collide and coagulate. Pure ash aggregates could also form as a result of water droplet scavenging and subsequent evaporation of water droplets, leaving behind only ash. In this case, droplets would not have interacted with a sea salt-containing boundary layer. Sea salt-cored aggregates could form when ash particles travel over a maritime environment and sea salt aerosol could easily be incorporated in the plume from the surrounding atmosphere. When the particles are sampled, pressure drops within the DRUM impactor cause the water in the droplet to evaporate, leaving behind ash aggregated with salt

Rinkleff, P. G.; Cahill, C. F.

2010-12-01

170

Design, fabrication and testing of ambient aerosol sampler inlets. Final report May 79-Oct 80  

SciTech Connect

Data are presented on the wind tunnel performances of two prototype Inhalable Particulate Matter (IPM) inlets designed for use with a dichotomous sampler. One was developed at the Aerosol Science Laboratory (ASL) Colorado State University, while the other was developed in an independent effort at the University of Minnesota (UM) and Lawrence Berkeley Laboratory (LBL). The ASL inlet is based on a unique omnidirectional cyclone fractionator, described in detail. Over the range of wind speeds from 0.5 - 24 km/hr, its measured 50% cutpoint was virtually invariant, 14.4 - 13.7 micrometers--well within the presently proposed IPM 50% cutpoint requirement. The UMLBL inlet results indicated near compliance with the IPM performance envelope, but there remain some small differences in data generated by UM and ASL personnel. Enrichment is apparent for both inlets in the 1 - 10 micrometers particle size range at the highest wind speed.

Wedding, J.B.; Weigand, M.A.

1982-04-01

171

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

172

Size-selective nonrefractory ambient aerosol measurements during the Particulate Matter Technology Assessment and Characterization Study-New York 2004 Winter Intensive in New York City  

NASA Astrophysics Data System (ADS)

During the Particulate Matter Technology Assessment and Characterization Study-New York (PMTACS-NY) in January/February 2004 a variety of modern aerosol measurement instruments were deployed at a field site on the campus of Queens College in Queens, New York. These instruments included the Aerodyne Aerosol Mass Spectrometer (Q-AMS), R&P Particulate Ambient Sulfate and Nitrate monitors (8400S&N), a Particle-into-liquid Sampler equipped with ion chromatographs (PILS-IC), an R&P FDMS TEOM, and several other techniques to measure physical aerosol properties. The PMTACS-NY 2004 winter campaign was designed to replicate measurements performed at this site during the PMTACS-NY 2001 summer campaign. The field campaign experienced significant meteorological variability and extreme weather conditions, which together with local and regional aerosol and precursor emissions generated a wide range of PM concentrations at the site, with significant changes in physical aerosol properties as well as aerosol composition as a function of particle size. Q-AMS quantification procedures and intercomparison studies of nonrefractory species mass concentrations measured with the Q-AMS and other colocated instruments (PILS-IC, R&P 8400 S/N, FDMS TEOM, and Sunset Labs OC Analyzer) are presented. The size-resolved aerosol composition over the measurement period and its variation with time of the day, regional meteorology and local source impacts are discussed. Results obtained during this field campaign are compared to data from the PMTACS-NY 2001 summer campaign, where aerosol composition was observed to have higher sulfate, significantly lower nitrate content and overall mean aerosol mass size distributions with larger mode diameters.

Weimer, Silke; Drewnick, Frank; Hogrefe, Olga; Schwab, James J.; Rhoads, Kevin; Orsini, Douglas; Canagaratna, Manjula; Worsnop, Douglas R.; Demerjian, Kenneth L.

2006-09-01

173

a Study of the Origin of Atmospheric Organic Aerosols  

Microsoft Academic Search

The sources of ambient organic particulate matter in urban areas are investigated through a program of emission source measurements, atmospheric measurements, and mathematical modeling of source\\/receptor relationships. A dilution sampler intended to collect fine organic aerosol from combustion sources is designed to simulate atmospheric cooling and dilution processes, so that organic vapors which condense under ambient conditions will be collected

Lynn Mary Hildemann

1990-01-01

174

VERSATILE AEROSOL CONCENTRATION ENRICHMENT SYSTEM (VACES) FOR SIMULTANEOUS IN VIVO AND IN VITRO EVALUATION OF TOXIC EFFECTS OF ULTRAFINE, FINE AND COARSE AMBIENT PARTICLES. PART II: FIELD EVALUATION. (R827352C001)  

EPA Science Inventory

This study presents results from a field evaluation of a mobile versatile aerosol concentration enrichment system (VACES), designed to enhance the ambient concentrations of ultrafine (less than 0.18 ...

175

VERSATILE AEROSOL CONCENTRATION ENRICHMENT SYSTEM (VACES) FOR SIMULTANEOUS IN-VIVO AND IN-VITRO EVALUATION OF TOXIC EFFECTS OF ULTRAFINE, FINE, AND COARSE AMBIENT PARTICLES. PART II. FIELD EVALUATION. (R826232)  

EPA Science Inventory

Abstract This study presents results from a field evaluation of a mobile versatile aerosol concentration enrichment system (VACES), designed to enhance the ambient concentrations of ultrafine (less than 0.18 ...

176

Correlation between urinary 1-hydroxypyrene and ambient air pyrene measured with an inhalable aerosol sampler and a total dust sampler in an electrode paste plant  

Microsoft Academic Search

The aim of this study was to investigate whether the use of an inhalable aerosol sampler would improve the correlation between urinary 1-hydroxypyrene and occupational pyrene exposure compared to measurements with a total dust sampler in an electrode paste plant. PAHs were collected on a filter and adsorbent by a 37-mm closed-face total aerosol sampler and an open-face sampler for

R. K Bentsen; K Halgard; H Notø; H. L Daae; S Øvrebø

1998-01-01

177

Role of the ambient aerosol in the atmospheric processing of semivolatile contaminants: A parameterized numerical model (Gas-Particle Partitioning (GASPAR))  

NASA Astrophysics Data System (ADS)

A parameterized description of the ambient aerosol is the basis of a model that treats both gas-particle partitioning and aqueous phase chemical transformations of semivolatile contaminants. Dividing the aerosol population into source, size, hygroscopic, and compositional classes, it is possible to assess the importance of contaminant-aerosol interactions under varying meteorological conditions. Using mercury as a test case, the model provides not only the quantity and speciation of mercury associated with particulate matter for use in dry deposition models and in conjunction with dispersion/meteorological models, but shows conclusively that deliquesced aerosol particles are not simply transporters of adsorbed mercury, but play an active and significant role in the transformation of elemental to oxidized mercury. The sensitivity analysis carried out using a version of the Direct Decoupled Method has shown the transfer of Hg(II) to the gas phase from the aqueous phase to be highly dependent on the chloride ion concentration in the initial parameterization array which describes the ambient aerosol. The chloride ion concentration has a notable effect on the oxidized Hg that is associated with the particle when the chemistry model reaches steady state. The reason for this is clarified by the dependencies of the neutral Hg containing species concentrations on the rates of mass transfer and the initial concentrations. The presence of soot in the aerosol particles is shown to be particularly important in the partitioning of Hg(II) between the gas, aqueous and particulate phases. The implications, given the higher solubility of most oxidized mercury species compared to elemental mercury, are fundamental for the understanding of the cycling and fate of mercury in the environment.

Pirrone, Nicola; Hedgecock, Ian M.; Forlano, Luigi

2000-04-01

178

NEUTRON ACTIVATION ANALYSIS FOR SIMULTANEOUS DETERMINATION OF TRACE ELEMENTS IN AMBIENT AIR COLLECTED ON GLASS-FIBER FILTERS  

EPA Science Inventory

Arsenic with 25 other elements are simultaneously determined in ambient air samples collected on glass-fiber filter composites at 250 United States sites. The instrumental neutron activation analysis (NAA) technique combined with the power of a dedicated mini-computer resulted in...

179

Source estimation of anthropogenic aerosols collected by a DRUM sampler during spring of 2002 at Gosan, Korea  

NASA Astrophysics Data System (ADS)

Continuous measurements of trace elements in size-segregated aerosols were performed by X-ray fluorescence analysis in order to assess the transport of natural and anthropogenic aerosol sources to Gosan site in springtime 2002. Various aerosol elemental components (such as Al, Ca, Si, K, Ti, and Mn) had low enrichment factors close to one and exhibited a similar temporal variation in coarse particle range (2.5-12 ?m) indicating the dominant influence of soil dust. On the other hand, in the fine particle size range (0.09-2.5 ?m), several anthropogenic elements in ambient particles (such as As, Se, Zn, Pb, and Cu) revealed high enrichment (100aerosol composition data in order to identify anthropogenic sources of aerosols during non-Asian dust (NAD) period. As a result, it was found that the coarse particles were mainly influenced by soil, seasalt, coal combustion, and metallurgical emission and fine particles were significantly attributed to several anthropogenic sources, such as oil combustion, nonferrous metal source, and municipal incineration. Especially, submicron particles (0.09-0.56 ?m) were further impacted by motor vehicles and field burning emissions in addition to those sources.

Han, J. S.; Moon, K. J.; Ryu, S. Y.; Kim, Y. J.; Perry, Kevin D.

180

Elemental and iron isotopic composition of aerosols collected in a parking structure.  

PubMed

The trace metal contents and iron isotope composition of size-resolved aerosols were determined in a parking structure in Tempe, AZ, USA. Particulate matter (PM)<2.5 microm in diameter (the fine fraction) and PM>2.5 microm were collected. Several air toxics (e.g., arsenic, cadmium, and antimony) were enriched above the crustal average, implicating automobiles as an important source. Extremely high levels of fine copper (up to 1000 ng m(-3)) were also observed in the parking garage, likely from brake wear. The iron isotope composition of the aerosols were found to be +0.15+/-0.03 per thousand and +0.18+/-0.03 per thousand for the PM<2.5 microm and PM>2.5 microm fractions, respectively. The similarity of isotope composition indicates a common source for each size fraction. To better understand the source of iron in the parking garage, the elemental composition in four brake pads (two semi-metallic and two ceramic), two tire tread samples, and two waste oil samples were determined. Striking differences in the metallic and ceramic brake pads were observed. The ceramic brake pads contained 10-20% copper by mass, while the metallic brake pads contained about 70% iron, with very little copper. Both waste oil samples contained significant amounts of calcium, phosphorous, and zinc, consistent with the composition of some engine oil additives. Differences in iron isotope composition were observed between the source materials; most notably between the tire tread (average=+0.02 per thousand) and the ceramic brake linings (average=+0.65 per thousand). Differences in isotopic composition were also observed between the metallic (average=+0.18 per thousand) and ceramic brake pads, implying that iron isotope composition may be used to resolve these sources. The iron isotope composition of the metallic brake pads was found to be identical to the aerosols, implying that brake dust is the dominant source of iron in a parking garage. PMID:19540567

Majestic, Brian J; Anbar, Ariel D; Herckes, Pierre

2009-09-01

181

Chemical and statistical interpretation of sized aerosol particles collected at an urban site in Thessaloniki, Greece.  

PubMed

The size distribution of aerosol particles (PM0.015-PM18) in relation to their soluble inorganic species and total water soluble organic compounds (WSOC) was investigated at an urban site of Thessaloniki, Northern Greece. The sampling period was from February to July 2007. The determined compounds were compared with mass concentrations of the PM fractions for nano (N: 0.015 < Dp < 0.06), ultrafine (UFP: 0.015 < Dp < 0.125), fine (FP: 0.015 < Dp < 2.0) and coarse particles (CP: 2.0 < Dp < 8.0) in order to perform mass closure of the water soluble content for the respective fractions. Electrolytes were the dominant species in all fractions (24-27%), followed by WSOC (16-23%). The water soluble inorganic and organic content was found to account for 53% of the nanoparticle, 48% of the ultrafine particle, 45% of the fine particle and 44% of the coarse particle mass. Correlations between the analyzed species were performed and the effect of local and long-range transported emissions was examined by wind direction and backward air mass trajectories. Multivariate statistical analysis (cluster analysis and principal components analysis) of the collected data was performed in order to reveal the specific data structure. Possible sources of air pollution were identified and an attempt is made to find patterns of similarity between the different sized aerosols and the seasons of monitoring. It was proven that several major latent factors are responsible for the data structure despite the size of the aerosols - mineral (soil) dust, sea sprays, secondary emissions, combustion sources and industrial impact. The seasonal separation proved to be not very specific. PMID:24007436

Tsitouridou, Roxani; Papazova, Petia; Simeonova, Pavlina; Simeonov, Vasil

2013-01-01

182

OM/OC Ratio and Specific Attenuation Coefficient in Ambient Particulate Matter at a Rural Site in Southern Ontario: Implications for Aerosol Aging and Emission Sources  

NASA Astrophysics Data System (ADS)

Carbonaceous species (organic carbon (OC) and elemental carbon (EC)) contribute a large portion of atmospheric fine particle mass and influence air quality, human health, and climate forcing. However, their emission sources and atmospheric aging processes are not well understood. The OM/OC ratio, defined as the organic mass per unit OC mass, is useful to understand the degree of oxidation of aerosol particles in atmospheric processes. We define the modified BC/EC (mod BC/EC) ratio as the ratio of the non-scattering corrected absorption coefficient per unit mass of EC. The mod BC/EC ratio has a similar meaning as the site specific attenuation coefficient, which is an important parameter used to convert light absorption measurements to black carbon mass. The mod BC/EC ratio can vary due to light scattering effect on absorption measurements, in which the oxygenated organics may play a role. The pyrolysis organic carbon (POC) is defined as the carbon mass fraction obtained at T= 870°C under a pure helium environment using the thermal separation method [Huang et al., 2006]. Since POC mass is generally proportional to the amount of oxygenated OC, studying the relationships among OC, EC, POC, as well as OM/OC and mod BC/EC ratios may help us understand the mechanisms of aerosol aging from different emission sources. Two 1-month field studies were conducted at a rural site in southern Ontario (NW of Toronto) during fall 2005 and spring 2007. Quartz filter samples were collected and analyzed for OC, POC, and EC concentrations using a thermal/optical method [Huang et al., 2006]. Together with the total organic matter measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and the absorption coefficient obtained from a Particle Soot Absorption Photometer (PSAP), the OM/OC and mod BC/EC ratios for ambient aerosols were obtained. Our results show that when air mass was mainly from south, OC, POC, and EC were relatively high, with average ratios of OC/EC, OM/OC, and POC/EC as 1.94, 1.41, and 0.52, respectively; this indicates significant anthropogenic impacts and relatively large portion of oxygenated OC, which might be due to either primary emissions or photo-chemical reactions occurred in a short period of time. When air mass was mainly from north, OC, POC, and EC were much lower, with average ratios of OC/EC, OM/OC, and POC/EC as 3.10, 1.20, and 0.79, respectively; this suggests less influence from anthropogenic emissions and relatively aged air mass from biogenic-source dominated clean air. Using POC, we estimate the specific attenuation at the site to be 5.8 m2 g-1 independent of the air mass origin. The relationships among OM/OC, mod BC/EC, and POC will be further discussed. References: Huang, L., Brook, J.R., Zhang, W., Li, S.M., Graham, L., Ernst, D., Chivulescu, A., and Lu, G. (2006) Stable isotope measurements of carbon fractions (OC/EC) in airborne particulate: a new dimension for source characterization and apportionment, Atmospheric Environment, 40, 2690-2705.

Chan, T. W.; Huang, L.; Leaitch, R.; Sharma, S.; Brook, J.; Slowik, J.; Abbatt, J.

2008-05-01

183

Comparative gene responses to collected ambient particles in vitro: endothelial responses.  

PubMed

Epidemiologic studies associate exposure to ambient particulate matter (APM) with increased cardiovascular mortality. Since both pulmonary inflammation and systemic circulation of ultrafine particles are hypothesized as initiating cardiovascular effects, we examined responses of potential target cells in vitro. Human aortic endothelial cells (HAEC) were exposed to 10 ?g/ml fine and ultrafine APM collected in an urban setting in summer 2006 or winter 2007 in the San Joaquin Valley, California. RNA isolated after 3 h was analyzed with high-density oligonucleotide arrays. Summer APM treatment affected genes involved in xenobiotic and oxidoreductase activity, transcription factors, and inflammatory responses in HAEC, while winter APM had a robust xenobiotic but lesser inflammatory response. Real-time polymerase chain reaction analysis confirmed that particulate matter (PM)-treated HAEC increased mRNA levels of xenobiotic response enzymes CYP1A1, ALDH1A3, and TIPARP and cellular stress response transcription factor ATF3. Inflammatory response genes included E-selectin, PTGS2, CXCL-2 (MIP-2?), and CCL-2 (MCP-1). Multiplex protein assays showed secretion of IL-6 and MCP-1 by HAEC. Since induction of CYP1A1 is mediated through the ligand-activated aryl hydrocarbon receptor (AhR), we demonstrated APM induced AhR nuclear translocation by immunofluorescence and Western blotting and activation of the AhR response element using a luciferase reporter construct. Inhibitor studies suggest differential influences of polycyclic aromatic hydrocarbon signaling, ROS-mediated responses and endotoxin alter stress and proinflammatory endothelial cell responses. Our findings demonstrate gene responses correlated with current concepts that systemic inflammation drives cardiovascular effects of particulate air pollution. We also demonstrate a unique pattern of gene responses related to xenobiotic metabolism in PM-exposed HAEC. PMID:21652769

Aung, Hnin H; Lame, Michael W; Gohil, Kishorchandra; He, Guochun; Denison, Michael S; Rutledge, John C; Wilson, Dennis W

2011-08-16

184

Spectral light absorption by ambient aerosols influenced by biomass burning in the Amazon Basin. I: Comparison and field calibration of absorption measurement techniques  

NASA Astrophysics Data System (ADS)

Spectral aerosol light absorption is an important parameter for the assessment of the radiation budget of the atmosphere. Although on-line measurement techniques for aerosol light absorption, such as the Aethalometer and the Particle Soot Absorption Photometer (PSAP), have been available for two decades, they are limited in accuracy and spectral resolution because of the need to deposit the aerosol on a filter substrate before measurement. Recently, a 7-wavelength (?) Aethalometer became commercially available, which covers the visible (VIS) to near-infrared (NIR) spectral range (?=450-950 nm), and laboratory calibration studies improved the degree of confidence in these measurement techniques. However, the applicability of the laboratory calibration factors to ambient conditions has not been investigated thoroughly yet. As part of the LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia - SMOke aerosols, Clouds, rainfall and Climate) campaign from September to November 2002 in the Amazon basin we performed an extensive field calibration of a 1-? PSAP and a 7-? Aethalometer utilizing a photoacoustic spectrometer (PAS, 532 nm) as reference device. Especially during the dry period of the campaign, the aerosol population was dominated by pyrogenic emissions. The most pronounced artifact of integrating-plate type attenuation techniques (e.g. Aethalometer, PSAP) is due to multiple scattering effects within the filter matrix. For the PSAP, we essentially confirmed the laboratory calibration factor by Bond et al. (1999). On the other hand, for the Aethalometer we found a multiple scattering enhancement of 5.23 (or 4.55, if corrected for aerosol scattering), which is significantly larger than the factors previously reported (~2) for laboratory calibrations. While the exact reason for this discrepancy is unknown, the available data from the present and previous studies suggest aerosol mixing (internal versus external) as a likely cause. For Amazonian aerosol, we found no absorption enhancement due to hygroscopic particle growth in the relative humidity (RH) range between 40% and 80%. However, a substantial bias in PSAP sensitivity that correlated with both RH and temperature (T) was observed for 20%ambient sampling based on the data from the present and previous studies. For this study, the estimated accuracies of the absorption coefficients determined by the PAS, PSAP and Aethalometer were 10, 15 and 20% (95% confidence level), respectively.

Schmid, O.; Artaxo, P.; Arnott, W. P.; Chand, D.; Gatti, L. V.; Frank, G. P.; Hoffer, A.; Schnaiter, M.; Andreae, M. O.

2006-08-01

185

Spectral light absorption by ambient aerosols influenced by biomass burning in the Amazon Basin I. Comparison and field calibration of absorption measurement techniques  

NASA Astrophysics Data System (ADS)

Spectral aerosol light absorption is an important parameter for the assessment of the radiation budget of the atmosphere. Although on-line measurement techniques for aerosol light absorption, such as the Aethalometer and the Particle Soot Absorption Photometer (PSAP), have been available for two decades, they are limited in accuracy and spectral resolution because of the need to deposit the aerosol on a filter substrate before measurement. Recently, a 7-wavelength (?) Aethalometer became commercially available, which covers the visible (VIS) to near-infrared (NIR) spectral range (?=450-950 nm), and laboratory calibration studies improved the degree of confidence in these measurement techniques. However, the applicability of the laboratory calibration factors to ambient conditions has not been investigated thoroughly yet. As part of the LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia - SMOke aerosols, Clouds, rainfall and Climate) campaign from September to November 2002 in the Amazon basin we performed an extensive field calibration of a 1-? PSAP and a 7-? Aethalometer utilizing a photoacoustic spectrometer (PAS, 532 nm) as reference device. Especially during the dry period of the campaign, the aerosol population was dominated by pyrogenic emissions. The most pronounced artifact of integrating-plate type attenuation techniques is due to multiple scattering effects within the filter matrix. For the PSAP, we essentially confirmed the laboratory calibration factor by Bond (1999). On the other hand, for the Aethalometer we found a multiple scattering enhancement of 5.23 (or 4.55, if corrected for aerosol scattering), which is significantly larger than the factors previously reported (~2). While the exact reason for this discrepancy is unknown, the available data from the present and previous studies suggest aerosol mixing (internal versus external) as a likely cause. While it is well-known that RH may (moderately) affect aerosol absorption, we found no dependence of either PSAP or Aethalometer on relative humidity (RH) for 30%ambient sampling based on the data from the present and previous studies. For this study, the estimated accuracies of the absorption coefficients determined by the PAS, PSAP and Aethalometer were 10, 15 and 20%, respectively.

Schmid, O.; Artaxo, P.; Arnott, W. P.; Chand, D.; Gatti, L. V.; Frank, G. P.; Hoffer, A.; Schnaiter, M.; Andreae, M. O.

2005-09-01

186

The wedding ambient aerosol sampling inlet ( D50 = 10 ?m) for the high-volume sampler  

NASA Astrophysics Data System (ADS)

The Wedding Inlet has a nominal cutpoint of 10 ?m at the flow rate of the High-Volume Sampler (40 cfm, 1.13 m 3 min -1) and fits existing samplers. Tests were conducted in both the wind tunnel and the field essentially as specified by 40 CFR, Part 53, Subpart D delineating performance tests for "PM-10" samplers. The results of these and additional tests were: (1) D 50 values ranged from 9.6 to 9.9 ?m over a wind speed range of 2-48 km h -1 with only ? 16 changing slightly at the 48 km h -1 condition (2) D 50 was essentially invariant with a volumetric flowrate change of ±10% (3) particles do not reach the collection substrate when the sampler is inoperative (4) D 50 was essentially invariant with angle of attack (tilt) of approaching wind flow of ±21° (5) effectiveness at 20 ?m for solid ammonium fluorescein was 3% as compared with 1% for oleic acid particles (6) a consistent D0 ? 25 ?m was observed in field tests (7) the sampler duplicates the performance of the EPA "ideal Sampler" within 5%.

Wedding, James B.; Weigand, Michael A.

187

Characterizing mineral dusts and other aerosols from the Middle East--Part 1: ambient sampling.  

PubMed

The purpose of the Enhanced Particulate Matter Surveillance Program was to provide scientifically founded information on the chemical and physical properties of dust collected over a period of approximately 1 year in Djibouti, Afghanistan (Bagram, Khowst), Qatar, United Arab Emirates, Iraq (Balad, Baghdad, Tallil, Tikrit, Taji, Al Asad), and Kuwait (northern, central, coastal, and southern regions). Three collocated low-volume particulate samplers, one each for the total suspended particulate matter, < 10 micro m in aerodynamic diameter (PM(10)) particulate matter, and < 2.5 micro m in aerodynamic diameter (PM(2.5)) particulate matter, were deployed at each of the 15 sites, operating on a '1 in 6' day sampling schedule. Trace-element analysis was performed to measure levels of potentially harmful metals, while major-element and ion-chemistry analyses provided an estimate of mineral components. Scanning electron microscopy with energy dispersive spectroscopy was used to analyze the chemical composition of small individual particles. Secondary electron images provided information on particle size and shape. This study shows the three main air pollutant types to be geological dust, smoke from burn pits, and heavy metal condensates (possibly from metals smelting and battery manufacturing facilities). Non-dust storm events resulted in elevated trace metal concentrations in Baghdad, Balad, and Taji in Iraq. Scanning-electron-microscopy secondary electron images of individual particles revealed no evidence of freshly fractured quartz grains. In all instances, quartz grains had rounded edges and mineral grains were generally coated by clay minerals and iron oxides. PMID:19235610

Engelbrecht, Johann P; McDonald, Eric V; Gillies, John A; Jayanty, R K M; Casuccio, Gary; Gertler, Alan W

2009-02-01

188

Contributions of fossil fuel, biomass-burning, and biogenic emissions to carbonaceous aerosols in Zurich as traced by 14C  

Microsoft Academic Search

Many open questions exist about the importance of different sources of carbonaceous aerosol, which is a substantial contributor to the global aerosol budget and, therefore, to climate change and human mortality. In this work, 14C was determined in elemental carbon (EC) and different organic carbon (OC) fractions from ambient urban aerosols with aerodynamic diameter <10 mum collected in Zurich (Switzerland).

Sönke Szidat; Theo M. Jenk; Hans-Arno Synal; Markus Kalberer; Lukas Wacker; Irka Hajdas; Anne Kasper-Giebl; Urs Baltensperger

2006-01-01

189

Contributions of fossil fuel, biomass-burning, and biogenic emissions to carbonaceous aerosols in Zurich as traced by 14C  

Microsoft Academic Search

Many open questions exist about the importance of different sources of carbonaceous aerosol, which is a substantial contributor to the global aerosol budget and, therefore, to climate change and human mortality. In this work, 14C was determined in elemental carbon (EC) and different organic carbon (OC) fractions from ambient urban aerosols with aerodynamic diameter <10 ?m collected in Zurich (Switzerland).

Sönke Szidat; Theo M. Jenk; Hans-Arno Synal; Markus Kalberer; Lukas Wacker; Irka Hajdas; Anne Kasper-Giebl; Urs Baltensperger

2006-01-01

190

Evaporation of Liquid Semi-Volatile Aerosols Collected on Fibrous Filters  

Microsoft Academic Search

Numerous sources of liquid aerosols are to be found in industrial environments. Such aerosols may, for instance, be cutting fluids, pesticides, etc., that are harmful or even toxic to humans. To control and reduce worker exposure to potentially toxic aerosols, these latter are usually filtered through fibrous filters. When non-saturated air traverses a clogged filter, however, the drops deposited on

Benjamin Sutter; Denis Bémer; Jean-Christophe Appert-Collin; Dominique Thomas; Noël Midoux

2010-01-01

191

Vertical distribution of optical and micro-physical properties of ambient aerosols during dry haze periods in Shanghai  

NASA Astrophysics Data System (ADS)

Based on the lidar data obtained from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite of NASA (National Aeronautics and Space Administration), the vertical distributions of aerosols are revealed during dry haze periods in the Shanghai vicinity by analyzing the optical and micro-physical parameters including total attenuated backscatter coefficient (TABC), volume depolarization ratio (VDR) and total attenuated color ratio (TACR). The preliminary conclusion is that when dry haze occurs in the Shanghai vicinity, smoke and maritime aerosols are the major types in summer and autumn and aerosols might be affected by long-distance transport of dust in spring; lower troposphere below 2 km is the layer polluted most severely and aerosol scattering with relatively irregular shape is much stronger than that of aerosols with relatively regular shape within 2-10 km in middle and upper troposphere; relatively large aerosols appear more frequently in lower (0-2 km) and middle troposphere (2-6 km) than those in upper troposphere (6-10 km). In addition, HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model is applied to analyze the aerosol sources during two typical episodes. The results indicate that the middle and upper troposphere in the Shanghai vicinity are affected by the long-distance transport of dusts from northwest of China or other upstream regions. The high aerosol concentrations in the Shanghai vicinity are mainly caused not only by local human activities but also by the long-distance transport from other places.

Chen, Yonghang; Liu, Qiong; Geng, Fuhai; Zhang, Hua; Cai, Changjie; Xu, Tingting; Ma, Xiaojun; Li, Hao

2012-04-01

192

Integrated chemical species analysis with source-receptor modeling results to characterize the effects of terrain and monsoon on ambient aerosols in a basin.  

PubMed

This study integrated estimated oxidation ratio of sulfur (SOR) and oxidation ratio of nitrogen (NOR) with source-receptor modeling results to identify the effects of terrain and monsoons on ambient aerosols in an urban area (north basin) and a rural area (south basin) of the Taichung Basin. The estimated results indicate that the conversion of sulfur mainly occurs in fine particles (PM?.?), whereas the conversion of nitrogen occurs in approximately equal quantities of PM?.? and coarse particles (PM?.?-??). The results show a direct relationship for PM?.? between the modeling results with SOR and NOR. The high PM?.? SOR, NOR, and secondary aerosol values all occurred in the upwind area during both monsoons; this shows that the photochemical reaction and the terrain effect on the pollutant transmission were significant in the basin. Additionally, the urban heat island effect on the urban area and the valley effect on the rural area were significant. The results show that secondary aerosol in PM?.?-?? contributed approximately 10 % during both monsoons, and the difference in the contribution from secondary aerosol between both areas was small. Vehicle exhaust emissions and wind-borne dust were two crucial PM2.5-10 contributors during both monsoons; their average contributions in both areas were higher than 34 and 32 %, respectively. PMID:22996820

Chen, Chi-Fan; Liang, Jeng-Jong

2013-05-01

193

ANALYSIS OF SECONDARY ORGANIC AEROSOL COMPOUNDS FROM THE PHOTOOXIDATION OF D -LIMONENE IN THE PRESENCE OF NO X AND THEIR DETECTION IN AMBIENT PM 2.5  

EPA Science Inventory

Chemical analysis of secondary organic aerosol (SOA) from the photooxidation of a d -limonene/NOx/air mixture was carried out. SOA, generated in a smog chamber, was collected on Zefluor filters. To determine the structural characteristics of the compounds, the filter sample...

194

DEVELOPMENT, DESIGN, AND OPERATION OF A CASCADE IMPACTOR TO COLLECT AEROSOL SAMPLES FOR WAVELENGTH DISPERSIVE X-RAY FLUORESCENCE ANALYSIS  

EPA Science Inventory

The goal of this research project was to design and construct a particle sizing device that will collect and size source emitted aerosols on 47 mm diameter substrates for subsequent wavelength dispersive x-ray fluorescence analysis. Calibration studies were conducted with a proto...

195

Chemical compositions and XANES speciations of Fe, Mn and Zn from aerosols collected in China and Japan during dust events  

Microsoft Academic Search

Variations of the chemical composition and elemental speciation of aeolian dust transported from China to Japan were investigated in this study. During 6-12 April 2002, a large-scale dust event was observed in China, Korea, and Japan. Aerosol samples collected in Beijing, Fukuoka, Nagoya, and Tsukuba at that time were used for this study. Variations of most elemental concentrations against the

ATSUYUKI OHTA; HIROSHI TSUNO; HIROYUKI KAGI; YUTAKA KANAI; MASAHARU NOMURA; RENJIAN ZHANG; SHIGERU TERASHIMA; NOBORU IMAI

2006-01-01

196

The Chemical Characteristics of Marine Mineral Aerosol Solutions at Ambient Relative Humidities and Some Effects on Iron Chemistry  

Microsoft Academic Search

It has been suggested that iron could play a critical role as a limiting micronutrient in some ocean regions where the concentration of major nutrients is high but primary productively is low. Because aerosol iron is the predominant pathway to supply iron to the open oceans, this dissertation focuses on the factors that affect the iron solubility in aerosol particles

Xiaorong Zhu

1992-01-01

197

MONITORING SYSTEM FOR COLLECTION AND ANALYSES OF AMBIENT ETHYLENE DICHLORIDE (EDC) LEVELS IN THE URBAN ATMOSPHERE  

EPA Science Inventory

A method for the measurement of ambient levels of ethylene dichloride (EDC) was developed and field tested. A 24-hour integrated sample is taken with an activated charcoal tube, followed by desorption of the EDC with carbon disulfide. The carbon disulfide solution is then analyze...

198

Comparison of spring and autumn time collected outdoor aerosol particles analyzed with depth-resolving SNMS  

NASA Astrophysics Data System (ADS)

Aerosol particles were collected in a size-classified way at the Forschungszentrum Karlsruhe during two autumn days of fine weather in September 1997 in order to analyze the depth distribution of the chemical inventory. The fine particles (<1 ?m diameter) had a nitrogen- and sulfur-dominated shell with a thickness of 13 nm around a carbon core and mainly originate from traffic soot. The coarse particles (>1 ?m diameter) consisted of soil dust or fly ash and sodium salt containing particles. Again the particle composition in greater depth was found to be different to the surface region, where nitrogen and sulfur as well as carbon were enriched. The surface-near nitrogen and sulfur could be attributed to ammonium sulfate, maybe deposited by particulate material formed from ammonia and SO x in the atmosphere. The results agree to a large degree with the analysis of outdoor particles collected at the same location but in spring time four years ago. However, the autumn particles of 1997 exhibited with 600 nm twice the diameter for the most frequent size compared to the particles sampled in spring of 1993.

Goschnick, J.; Natzeck, C.; Sommer, M.

1999-04-01

199

N-alkanes, fatty acid esters, and fatty acid salts in size fractionated aerosols collected over the Mediterranean Sea  

SciTech Connect

The {und n}-alkanes, fatty acid esters, and fatty acid salts have been analyzed in size fractionated aerosols collected over the Mediterranean Sea using a five-stage cascade impactor. Two main sources of {und n}-alkanes have been identified: terrestrially derived {und n}-alkanes evenly distributed over the whole particle size spectrum and anthropogenic {und n}-alkanes predominantly carried by submicron particles. The comparison between the fatty acid ester (FAE) and fatty acid salt (FAS) particle size distributions allowed an important contribution to be ascertained of the marine source in aerosols ranging from 7.2 to 3.0 {mu}m under rough weather conditions that may be due to larger bubble produced particles. In contrast, FAE and FAS were evenly distributed from the first to the fifth stage, when collected during calm sea surface conditions. Higher values of the degree of unsaturation of FAE and FAS were associated with mass concentration maxima observed on stages 2 and 3 in IMP1 aerosol sample whereas lower values were found on the other stages in the same sample, and over the whole particle size spectrum in IMP2 aerosol sample collected during calm weather conditions. The data the authors present here are discussed in terms of jet and film drop ejections and degradation processes.

Sicre, M.A.; Marty, J.C.; Saliot, A. (Univ. Pierre et Marie Curie, Paris (France))

1990-03-20

200

Sugars as source indicators of biogenic organic carbon in aerosols collected above the Howland Experimental Forest, Maine  

NASA Astrophysics Data System (ADS)

Bulk aerosols (>1 ?m) were collected continuously above the canopy at the Howland Experimental Forest, Maine, USA from May to October 2002. Each sample integrated over an approximately 2-week period. Mono- and disaccharide sugars were extracted using a microscale technique and were analyzed as their TMS derivatives by gas chromatography-mass spectrometry (GC-MS). Concentrations of total aerosol sugars ranged from 10 to 180 ng m -3. Glucose was the most abundant sugar (40-75% of the total sugars). The monosaccharides arabinose, fructose, galactose, mannose, arabitol and mannitol, and the disaccharides sucrose, maltose and mycose (aka trehalose) were also present in lower concentrations. The sugar composition in the aerosols varied seasonally. Fructose and sucrose were prevalent in early spring and decreased in relative abundance as the growing season progressed. Sugar polyols (arabitol and mannitol) and the disaccharide mycose (a fungal metabolite) were more prevalent in autumn during the period of leaf senescence. The changes in the sugar composition in the aerosol samples appear to reflect the seasonality of sugar production and utilization by the ecosystem. Plant waxes were present as significant components also indicating an input from biogenic background. Smoke plumes from Quebec forest fires passed over the Howland site in early July 2002. Levoglucosan, a biomarker of biomass burning, increased by an order of magnitude in the aerosol samples collected during this time. Glucose, mannose, arabinose, galactose, and also, plant waxes increased in concentration by factors of 2-5 in the smoke-impacted samples, indicating that wildfires enhance atmospheric emissions of uncombusted organic compounds. In contrast, concentrations of fructose, sugar polyols and disaccharides were not significantly higher in the smoke-impacted samples and indicated that biomass burning was not a significant source of these compounds in the aerosols.

Medeiros, Patricia M.; Conte, Maureen H.; Weber, John C.; Simoneit, Bernd R. T.

201

Effects of aerosol collection and extraction procedures on the optical properties of water-soluble organic compounds  

NASA Astrophysics Data System (ADS)

Water-soluble organic compounds (WSOC) are routinely collected using active and passive aerosol samplers and, after extraction in water, analyzed using UV-vis absorbance and fluorescence techniques. These analyses provide important information regarding the chemical character and sources of aerosols worldwide. To evaluate the effects of various aerosol collection and processing methods on the optical properties of WSOC, two-dimensional absorption spectra from 200 to 900 nm and three-dimensional fluorescence excitation-emission spectra (EEMs) from 240 to 450 nm excitation and 300 to 560 nm emission were analyzed in samples obtained simultaneously with different procedures. Samples included: milli-Q purified water passed through 140 mm diameter glass fiber and quartz fiber filters used in high volume PM10 aerosol samplers, 47 mm glass fiber filters used for organic matter analyses, and mixed cellulose 0.2 micron and 0.015 micron filters used for bacterial and viral filtration, respectively; milli-Q purified water rinsed in plastic buckets used for passive wet and dry deposition collection; and WSOC samples extracted from filters by soaking, sonication, and agitation. Parallel factor analysis (PARAFAC) modeling of WSOC was performed to quantify the influence of various collection and extraction procedures on fluorescence signatures. All filters examined were found to leach some amount of fluorescent compounds (Figure 1). Mixed cellulose filters, especially those with small pore size, leached substantially more amino acid-like and humic-like material than other filters, whereas leaching from quartz fiber filters used for high volume aerosol collection was minimal (Figure 1). Fluorescence intensities of filter leachates decreased with increased rinsing of filters, indicating that rinsing with purified water prior to filtration is advisable, even for pre-combusted filters. Dissolved organic carbon concentrations of WSOC extracted from filters by sonication, agitation, and soaking techniques were not statistically different. The WSOC of aerosol samples collected passively (as deposition) and actively (on filters) had similar fluorescence spectra. Our results suggest that WSOC studies may be highly comparable irrespective of collection procedures, but that methodological differences related to filter use can be significant and should be reported in detail in the literature. Figure 1. Excitation-emission matrices (EEMs) of a WSOC sample extracted from a pre-combusted quartz fiber filter (left) by agitation in 60 mL milli-Q purified water and a 100 mL sample of milli-Q purified water filtered through a 0.015 ?m pore size mixed cellulose ester filter (right).

Mladenov, N.; Alados-Arboledas, L.; Olmo Reyes, F. J.; Reche, I.

2009-12-01

202

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...

203

Technical Note: A novel rocket-based in situ collection technique for mesospheric and stratospheric aerosol particles  

NASA Astrophysics Data System (ADS)

A technique for collecting aerosol particles between altitudes of 17 and 85 km is described. Spin-stabilized collection probes are ejected from a sounding rocket allowing for multi-point measurements. Each probe is equipped with 110 collection samples that are 3 mm in diameter. The collection samples are one of three types: standard transmission electron microscopy carbon grids, glass fibre filter paper or silicone gel. Collection samples are exposed over a 50 m to 5 km height range with a total of 45 separate ranges. Post-flight electron microscopy will give size-resolved information on particle number, shape and elemental composition. Each collection probe is equipped with a suite of sensors to capture the probe's status during the fall. Parachute recovery systems along with GPS-based localization will ensure that each probe can be located and recovered for post-flight analysis.

Reid, W.; Achtert, P.; Ivchenko, N.; Magnusson, P.; Kuremyr, T.; Shepenkov, V.; Tibert, G.

2013-03-01

204

Comprehensive characterization of ambient nanoparticles collected near an industrial science park: particle size distributions and relationships with environmental factors.  

PubMed

We investigated the characteristics of ambient particles and their relationships with various environmental factors, including gaseous pollutants (CH4, non-methane hydrocarbons (NMHC), total hydrocarbons (THC), NOx, CO, SO2), meteorological parameters (humidity, temperature), and time (day/night, workday/weekend). We used an electrical low-pressure cascade impactor to measure the number and size distributions of ambient particles (0.007-10 tm) that were collected approximately 1 km northwest of Hsinchu Science Park in Taiwan between February and May 2007. The number concentrations of particles were enhanced through photochemical reactions during the day. In addition, high traffic flow during workdays increased the formation of particulates. Except for SO2, all of the gaseous pollutants we studied (CH4, NMHC, THC, NOx, CO) correlated positively with the total number concentrations of ambient particles during daytime, indicating that they might contribute to the particulate burden. The poorer relationship between the SO2 level and the total number concentration of particles suggests that SO2 might participate indirectly in the nucleation process during particle formation, The high enrichment factors for Zn, Pb, Cu, and Mn, which mostly comprised the ultrafine particles (diameter: < 0.1 microm) and fine particles (diameter: 0.1-1 microm), presumably arose from emissions from traffic and high technology factories. Heterogeneous reactions on solid particles might play a role in the removal of SOx and NOx from the atmosphere. Sulfides and nitrides can further react with these local pollutants, forming specific Cu-containing compounds: CuO (39%), CuSO4 (34%), and Cu(NO3)2 (27%), within the ambient particles in this industrial area. PMID:22128541

Huang, Yuhjeen; Hsu, Lingyen; Chang, Yunghsun

2011-01-01

205

Contrasting online MSn spectra of organic acids in ambient aerosol from the boreal forest at Hyytiälä, Finland and from the mixed forest at the Taunus observatory, Germany  

NASA Astrophysics Data System (ADS)

Emission of biogenic volatile organic compounds (BVOCs) by the vegetation and subsequent atmospheric oxidation leads to the formation of secondary organic aerosol (SOA). Therefore, forests are a main source of aerosols which have significant impact on the earth's climate.[1] The oxidation of BVOCs results in a variety of mostly unidentified organic species in trace level concentrations, which partition between gas- and particle-phase. Organic acids are of particular importance for the particle-phase fraction, since the higher oxidation state and molecular mass, compared to the corresponding precursors, is accompanied by a much lower volatility. Until now, only limited instrumentation exists for the simultaneous online analysis of organic acids in gas- and particle-phase. Here we show the first field application of an Atmospheric Pressure Chemical Ionization Ion Trap Mass Spectrometer (APCI-IT-MS) in combination with a miniature Versatile Aerosol Concentration Enrichment System (mVACES) for measuring organic acids in gas- and particle-phase[2]. The benefits of the online APCI-IT-MS are soft ionization with low fragmentation, high time resolution and less sampling artifacts than in the common procedure of taking filter samples, extraction and subsequent detection with LC-MS. Furthermore, the capability to perform online MSn of isolated m/z ratios from ambient and laboratory generated aerosol leads to an improved understanding of the composition of secondary organic aerosol. The here described measurements were conducted during the HUMPPA-COPEC 2010 campaign at Hyytiälä, Finland and during the INUIT campaign 2012 on Mt. Kleiner Feldberg, Germany. By merging APCI-IT-MS data with data from the Aerodyné C-ToF-AMS, it can be observed that the gas- to particle-partitioning of organic acids strongly depends on the fraction of aerosol which is organic matter, as it is predicted by a partitioning model[3]. High observed gas-phase concentrations of organic acids at Hyytiälä are a strong hint for unidentified species. This can be supported by MSn observations, where the fragmentation pattern from Hyytiälä show different signals compared to the fragmentation pattern from the same m/z ratio at the Taunus Observatory and from chamber terpene ozonolysis. Literature: [1] Tunved, P. et al. (2006) Science 312, 261-263. [2] Vogel, A. L. et al. (2012) Atmos. Meas. Tech. Discuss. 5, 6147-6182. [3] Pankow, J. F. (1994) Atmos. Env. 28, 189-193.

Vogel, Alexander L.; Äijälä, Mikko; Ehn, Mikael; Junninen, Heikki; Petäjä, Tuukka; Worsnop, Douglas R.; Kulmala, Markku; Williams, Jonathan; Schneider, Johannes; Hoffmann, Thorsten

2013-04-01

206

Enhanced concentrations of citric acid in spring aerosols collected at the Gosan background site in East Asia  

Microsoft Academic Search

In order to investigate water-soluble dicarboxylic acids and related compounds in the aerosol samples under the Asian continent outflow, total suspended particle (TSP) samples (n = 32) were collected at the Gosan site in Jeju Island over 2–5 days integration during 23 March–1 June 2007 and 16–24 April 2008. The samples were analyzed for water-soluble dicarboxylic acids, ketocarboxylic acids, and ?-dicarbonyls using

Jinsang Jung; Kimitaka Kawamura

2011-01-01

207

PM2.5 aerosols collected in the Antarctic Peninsula with a solar powered sampler during austral summer periods  

Microsoft Academic Search

Collection of PM2.5 particles was carried out in Antarctica in the summer periods of years 2006 and 2007 using solar panels to operate the sampling unit. The unit was installed 2.5 km from the B. O'Higgins Chilean base to avoid possible air contamination from oil or gas burning electric power stations. The aerosols were analyzed by XRF identifying twenty elements between

M. Préndez; J. Wachter; C. Vega; R. G. Flocchini; P. Wakayabashi; J. R. Morales

2009-01-01

208

Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite  

Microsoft Academic Search

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and

D. Salcedo; Timothy B. Onasch; K. Dzepina; M. R. Canagaratna; Q. Zhang; J. A. Huffman; Peter DeCarlo; J. T. Jayne; P. Mortimer; Douglas R. Worsnop; C. E. Kolb; Kirsten S. Johnson; Bilal M. Zuberi; L. C. Marr; Rainer M. Volkamer; Luisa Molina; Mario J. Molina; B. Cardenas; R. M. Bernabé; C. Márquez; Jeffrey S. Gaffney; Nancy A. Marley; Alexander Laskin; V. Shutthanandan; YuLong Xie; W. H. Brune; R. Lesher; T. Shirley; J. L. Jimenez

2006-01-01

209

Chemotactic Sensing towards Ambient and Secreted Attractant Drives Collective Behaviour of E. coli  

PubMed Central

We simulate the dynamics of a suspension of bacterial swimmers, which chemotactically sense gradients in either ambient or self-secreted attractants (e.g. nutrient or aspartate respectively), or in both. Unlike previous mean field models based on a set of continuum partial differential equations, our model resolves single swimmers and therefore incorporates stochasticity and effects due to fluctuations in the bacterial density field. The algorithm we use is simple enough that we can follow the evolution of colonies of up to over a million bacteria for timescales relevant to pattern formation for E. coli growing in semisolid medium such as agar, or in confined geometries. Our results confirm previous mean field results that the patterns observed experimentally can be reproduced with a model incorporating chemoattractant secretion, chemotaxis (towards gradients in the chemoattractant field), and bacterial reproduction. They also suggest that further experiments with bacterial strains chemotactically moving up both nutrient and secreted attractant field may yield yet more dynamical patterns.

Curk, Tine; Marenduzzo, Davide; Dobnikar, Jure

2013-01-01

210

Hygroscopic and Chemical Properties of Aerosols collected near a Copper Smelter: Implications for Public and Environmental Health  

PubMed Central

Particulate matter emissions near active copper smelters and mine tailings in the southwestern United States pose a potential threat to nearby environments owing to toxic species that can be inhaled and deposited in various regions of the body depending on the composition and size of the particles, which are linked by particle hygroscopic properties. This study reports the first simultaneous measurements of size-resolved chemical and hygroscopic properties of particles next to an active copper smelter and mine tailings by the towns of Hayden and Winkelman in southern Arizona. Size-resolved particulate matter samples collected near an active copper smelter were examined with inductively coupled plasma mass spectrometry, ion chromatography, and a humidified tandem differential mobility analyzer. Aerosol particles collected at the measurement site are enriched in metals and metalloids (e.g. arsenic, lead, and cadmium) and water-uptake measurements of aqueous extracts of collected samples indicate that the particle diameter range of particles most enriched with these species (0.18–0.55 µm) overlaps with the most hygroscopic mode at a relative humidity of 90% (0.10–0.32 µm). These measurements have implications for public health, microphysical effects of aerosols, and regional impacts owing to the transport and deposition of contaminated aerosol particles.

Sorooshian, Armin; Csavina, Janae; Shingler, Taylor; Dey, Stephen; Brechtel, Fred J.; Saez, A. Eduardo; Betterton, Eric A.

2012-01-01

211

Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite  

NASA Astrophysics Data System (ADS)

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM2.5 mass concentration during MCMA-2003 within the combined uncertainties. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents, on average, 54.6% (standard deviation ?=10%) of the mass, with the rest consisting of inorganic compounds (mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5 (?=10%); BC mass concentration is about 11% (?=4%); while soil represents about 6.9% (?=4%). Size distributions are presented for the AMS species; they show an accumulation mode that contains mainly oxygenated organic and secondary inorganic compounds. The organic size distributions also contain a small organic particle mode that is likely indicative of fresh traffic emissions; small particle modes exist for the inorganic species as well. Evidence suggests that the organic and inorganic species are not always internally mixed, especially in the small modes. The aerosol seems to be neutralized most of the time; however, there were some periods when there was not enough ammonium to completely neutralize the nitrate, chloride and sulfate present. The diurnal cycle and size distributions of nitrate suggest local photochemical production. On the other hand, sulfate appears to be produced on a regional scale. There are indications of new particle formation and growth events when concentrations of SO2 were high. Although the sources of chloride are not clear, this species seems to condense as ammonium chloride early in the morning and to evaporate as the temperature increases and RH decreases. The total and speciated mass concentrations and diurnal cycles measured during MCMA-2003 are similar to measurements during a previous field campaign at a nearby location.

Salcedo, D.; Onasch, T. B.; Dzepina, K.; Canagaratna, M. R.; Zhang, Q.; Huffman, J. A.; Decarlo, P. F.; Jayne, J. T.; Mortimer, P.; Worsnop, D. R.; Kolb, C. E.; Johnson, K. S.; Zuberi, B.; Marr, L. C.; Volkamer, R.; Molina, L. T.; Molina, M. J.; Cardenas, B.; Bernabé, R. M.; Márquez, C.; Gaffney, J. S.; Marley, N. A.; Laskin, A.; Shutthanandan, V.; Xie, Y.; Brune, W.; Lesher, R.; Shirley, T.; Jimenez, J. L.

2006-03-01

212

Bromide content of sea-salt aerosol particles collected over the Indian Ocean during INDOEX 1999  

NASA Astrophysics Data System (ADS)

Bromide can be depleted from sea-salt aerosol particles in the marine boundary layer (MBL) and converted to reactive gas-phase species like Br, BrO, and HOBr, which affect ozone chemistry. Air pollution can enhance the bromine release from sea-salt aerosols and thus inject additional bromine into the MBL. During the winter monsoon the northern Indian Ocean is strongly affected by air pollution from the Indian subcontinent and Asia. As part of the Indian Ocean Experiment (INDOEX), aerosol particles were sampled with stacked filter units (SFU) on the NCAR Hercules C-130 aircraft during February-March 1999. We determined the vertical and latitudinal distribution of the major inorganic aerosol components (NH4+, Na+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42-) and the Br- content of the coarse aerosol to examine the role of the bromine release on the gas-phase chemistry in the marine boundary layer over the tropical Indian Ocean. The aerosol mass and composition varied significantly with air mass origin and sampling location. In the northern part of the Indian Ocean (5°-15°N, 66°-73°E), high concentrations of pollution-derived inorganic species were found in the marine boundary layer extending from the sea surface to about 1.2 km above sea level. In this layer, the average mass concentration of all aerosol species detected by our technique was comparable to pollution levels observed in industrialized regions. In the Southern Hemisphere (1°-9°S, 66°- 73°E), the aerosol concentrations rapidly declined to remote background levels. A chloride loss from the coarse aerosol particles was observed in parallel to the latitudinal gradient of the non sea salt SO42- burden. In most of the samples, Br- was depleted from the sea-salt aerosols. However, we found an enrichment in bromide in aerosols affected by air masses originating over strong pollution sources in India (Bombay, Calcutta). In these cases the additional pollution-derived Br from organo-halogen additives in petrol outweighs the release of sea-salt bromine.

Gabriel, R.; von Glasow, R.; Sander, R.; Andreae, M. O.; Crutzen, P. J.

2002-10-01

213

Variation of particle number and mass concentration in various size ranges of ambient aerosols in Eastern Germany  

Microsoft Academic Search

There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for short-term responses of the respiratory system as observed in several epidemiological studies. However, the available data on ambient particle concentrations in various size ranges are not sufficient to answer this question.Therefore, on 180 days during the winter 1991\\/92 daily mean

Th. Tuch; P. Brand; H. E. Wichmann; J. Heyder

1997-01-01

214

EFFECT OF AN ACTIVATED SLUDGE WASTEWATER TREATMENT PLANT ON AMBIENT AIR DENSITIES OF AEROSOLS CONTAINING BACTERIA AND VIRUSES  

EPA Science Inventory

Bacteria and virus-containing aerosols were studied during late summer and fall in a U.S. midwestern suburb before and during the start up and operation of an unenclosed activated sludge wastewater treatment plant. The air in this suburban area contained low-level densities of in...

215

Long-term observation of water-soluble chemical components in the bulk atmospheric aerosols collected at Okinawa, Japan  

NASA Astrophysics Data System (ADS)

The economic development and population growth in recent Asia spread air pollution. Emission rate of air pollutants from Asia, in particular oxides of nitrogen, surpassed those from North America and Europe and should continue to exceed them for decades. The study of the long-range transported air pollution from Asian continent has gained a special attention in Japan because of increase in photochemical oxidants in relatively remote islands. Okinawa Island is situated approximately 1500 km south of Tokyo, Japan, 2000 km southeast of Beijing, China, and 1000 km south of South Korea. Its location in Asia is well suited for studying long-range transport of air pollutants in East Asia because maritime air mass prevails during summer, while continental air mass dominates during fall, winter, and spring. The maritime air mass data can be seen as background and can be compared with continental air masses which have been affected by anthropogenic activities. Bulk aerosol samples were collected on quartz filters by using a high volume air sampler. Sampling duration was one week for each sample. We determined the concentrations of water-soluble anions, cations and dissolved organic carbon (DOC) in the bulk aerosols collected at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) using ion chromatography, atomic absorption spectrometry, and total organic carbon analyzer, respectively. We will report water-soluble chemical components data of anions, cations and DOC in bulk atmospheric aerosols collected at CHAAMS during August, 2005 to April, 2010. Seasonal variation of water-soluble chemical components showed that the concentrations were relatively low in summer, higher in fall and winter, and the highest in spring. When air mass came from Asian Continent, the concentrations of water-soluble chemical components were much higher compared to the other directions. In addition, we calculated background concentration of water-soluble chemical components at Okinawa, Japan.

Handa, Daishi; Somada, Yuka; Ijyu, Moriaki; Azechi, Sotaro; Nakaema, Fumiya; Arakaki, Takemitsu; Tanahara, Akira

2010-05-01

216

Daily long-term monitoring of organic compounds in ambient aerosol based on direct thermal desorption (DTD) and gas chromatography coupled to fast time-of-flight mass spectrometry for time-resolved source apportionment  

NASA Astrophysics Data System (ADS)

Epidemiological studies show that serious health effects are associated with the immission of anthropogenic fine and ultra-fine particles. It is likely that semi-volatile organic compounds (SVOC) are at least partly responsible for the observed health effects. Therefore a better characterization of particle associated SVOC is needed. A newly developed direct-thermal-desorption gas chromatography time of flight mass spectrometry method (DTD-GC-TOFMS) was applied for characterization of PM2.5 filters. A day-by-day analysis of SVOC in PM2.5 was performed for more than 3 years (ca. 1100 samples). The particles were collected in Augsburg, where the GSF research centre (Institute of Epidemiology and Institute of Ecological Chemistry) is operating a large aerosol measurement site in cooperation with the University of Augsburg (WZU), the school of applied sciences (FH) Augsburg and the BIfA GmbH. More than 1500 compounds are separable by the GC-TOFMS method. Selected compounds (ca. 200) are semi-quantified and used for further analysis. An additional aim is to use the data on organic constituents in epidemiological studies. The 3 year continuous monitoring data set shows long term variations (e.g. seasonal trends) as well as prominent daily fluctuations (i.e. influenced by meteorology and emission). The data set furthermore is used for a day-resolved source apportionment based on source-specific organic indicator compounds and statistical methods. A large fraction of the particle-bound SVOC, however, can not be resolved by conventional GC methods. This is due to the enormous chemical complexity of ambient particulate matter. The comprehensive two-dimensional gas chromatography (GCxGC) is a novel GC method which resolves a sample according to two chromatographic dimensions. Due to the two- dimensional chromatography the separation power is considerably increased. In a typical Augsburg PM2.5 aerosol sample, e.g., by far more than 10.000 compounds are detectable by GCxGC-TOFMS. In the contribution recent results on GCxGC-TOFMS ambient aerosol monitoring are presented and discussed.

Zimmermann, R.; Schnelle-Kreis, J.; Sklorz, M.

2006-12-01

217

Correlations between absorption Angström exponent (AAE) of wintertime ambient urban aerosol and its physical and chemical properties  

NASA Astrophysics Data System (ADS)

Based on a two-week measurement campaign in an environment heavily polluted both by transit traffic and household heating in the inner city of Szeged (Hungary), correlations between the absorption Angström exponent (AAE) fitted to the optical absorption coefficients measured with a four wavelength (1064, 532, 355 and 266 nm) photoacoustic aerosol measuring system (4?-PAS) and various aerosol parameters were identified. AAE was found to depend linearly on OCwb/EC and on NGM100/NGMD20, i.e. on the ratio of mass concentrations of elemental carbon (EC) to the fraction of organic carbon associated with wood burning (OCwb), and on the ratio of aerosol number concentrations in the 20 nm (NGMD20) to 100 nm (NGMD100) modes, with a regression coefficient of R = 0.95 and R = 0.86, respectively. In the daily fluctuation of AAE two minima were identified, which coincide with the morning and afternoon rush hours, during which NGMD20 exhibits maximum values. During the campaign the shape of the aerosol volume size distribution (dV/dlogD) was found to be largely invariant, supporting the assumption that the primary driver for the AAE variation was aerosol chemical composition rather than particle size. Furthermore, when wavelength segregated AAE values were calculated, AAE for the shorter wavelengths (AAE355-266) was also found to depend linearly on the above mentioned ratios with similar regression coefficients but with a much steeper correlation line, while the AAE for the longer wavelengths (AAE1064-532) exhibits only a considerably weaker correlation. These results prove the unique advantages of real time multi-wavelength photoacoustic measurement of optical absorption in case the wavelength range includes the ultra-violet too.

Utry, N.; Ajtai, T.; Filep, Á.; Pintér, M.; Török, Zs.; Bozóki, Z.; Szabó, G.

2014-07-01

218

DEVELOPMENT OF COLLECTION METHODS FOR SEMIVOLATILE ORGANIC COMPOUNDS IN AMBIENT AIR  

EPA Science Inventory

Cartridges containing solid adsorbents between layers of polyurethane foam (PUF) were evaluated for collecting chlorobenzenes, chlorophenols, hexachlorocyclohexanes (HCHs), and two-ring aromatic hydrocarbons. The 26-sq.cm cross-section glass cartridges, packed with Tenax (5-10 g)...

219

Semi-automated bacterial spore detection system with micro-fluidic chips for aerosol collection, spore treatment and ICAN DNA detection  

Microsoft Academic Search

A semi-automated bacterial spore detection system (BSDS) was developed to detect biological threat agents (e.g., Bacillus anthracis) on-site. The system comprised an aerosol sampler, micro-fluidic chip-A (for spore germination and cell lysis), micro-fluidic chip-B (for extraction and detection of genomic DNA) and an analyzer. An aerosol with bacterial spores was first collected in the collection chamber of chip-A with a

Hisao Inami; Kouichiro Tsuge; Mitsuhiro Matsuzawa; Yasuhiko Sasaki; Shigenori Togashi; Asuka Komano; Yasuo Seto

2009-01-01

220

Comparison Between NPP-VIIRS Aerosol Data Products and the MODIS AQUA Deep Blue Collection 6 Dataset Over Land  

NASA Technical Reports Server (NTRS)

Aerosols are small particles suspended in the atmosphere and have a variety of natural and man-made sources. Knowledge of aerosol optical depth (AOD), which is a measure of the amount of aerosol in the atmosphere, and its change over time, is important for multiple reasons. These include climate change, air quality (pollution) monitoring, monitoring hazards such as dust storms and volcanic ash, monitoring smoke from biomass burning, determining potential energy yields from solar plants, determining visibility at sea, estimating fertilization of oceans and rainforests by transported mineral dust, understanding changes in weather brought upon by the interaction of aerosols and clouds, and more. The Suomi-NPP satellite was launched late in 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP is being used, among other things, to determine AOD. This study compares the VIIRS dataset to ground-based measurements of AOD, along with a state-of-the-art satellite AOD dataset (the new version of the Moderate Resolution Imaging Spectrometer Deep Blue algorithm) to assess its reliability. The Suomi-NPP satellite was launched late in 2011, carrying several instruments designed to continue the biogeophysical data records of current and previous satellite sensors. The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP is being used, among other things, to determine aerosol optical depth (AOD), and related activities since launch have been focused towards validating and understanding this new dataset through comparisons with other satellite and ground-based products. The operational VIIRS AOD product is compared over land with AOD derived from Moderate Resolution Imaging Spectrometer (MODIS) observations using the Deep Blue (DB) algorithm from the forthcoming Collection 6 of MODIS data

Sayer, Andrew M.; Hsu, N. C.; Bettenhausen, C.; Lee, J.; Kondragunta, S.

2013-01-01

221

DEVELOPMENTS IN DIRECT THERMAL EXTRACTION GAS CHROMATOGRAPHY-MASS SPECTROMETRY OF FINE AEROSOLS  

EPA Science Inventory

This examines thermal extraction gas chromatography-mass spectrometry (TE/GC/MS) applied to aerosols collected on filters. Several different TE/GC/MS systems as a group have speciated hundreds of individual organic constituents in ambient fine aerosols. Molecular marker source ap...

222

SOURCE CHARACTERIZATION AND APPORTIONMENT OF THE HOUSTON AEROSOL BY MEANS OF X-RAY DIFFRACTION TECHNIQUES  

EPA Science Inventory

Eighteen pairs of dichotomous sampler filters (Teflon) used in collecting ambient aerosol at Houston, Texas, from 10-18 September 1980, have been studied by x-ray diffractionmetry. Although none of the filters analyzed contained aerosol loads sufficiently adequate for optimum XRD...

223

VERSATILE AEROSOL CONCENTRATION ENRICHMENT SYSTEM (VACES) FOR SIMULTANEOUS IN VIVO AND IN VITRO EVALUATION OF TOXIC EFFECTS OF ULTRAFINE, FINE AND COARSE AMBIENT PARTICLES. PART I: DEVELOPMENT AND LABORATORY CHARACTERIZATION. (R827352C001)  

EPA Science Inventory

This study presents the development and bench-testing of a versatile aerosol concentration enrichment system (VACES) capable of simultaneously concentrating ambient particles of the coarse, fine and ultrafine size fractions for conducting in vivo and in vitro studies. The VACE...

224

Evaluation of a solid matrix for collection and ambient storage of RNA from whole blood  

PubMed Central

Background Whole blood gene expression-based molecular diagnostic tests are becoming increasingly available. Conventional tube-based methods for obtaining RNA from whole blood can be limited by phlebotomy, volume requirements, and RNA stability during transport and storage. A dried blood spot matrix for collecting high-quality RNA, called RNA Stabilizing Matrix (RSM), was evaluated against PAXgene® blood collection tubes. Methods Whole blood was collected from 25 individuals and subjected to 3 sample storage conditions: 18 hours at either room temperature (baseline arm) or 37°C, and 6 days at room temperature. RNA was extracted and assessed for integrity by Agilent Bioanalyzer, and gene expression was compared by RT-qPCR across 23 mRNAs comprising a clinical test for obstructive coronary artery disease. Results RSM produced RNA of relatively high integrity across the various tested conditions (mean RIN?±?95% CI: baseline arm, 6.92?±?0.24; 37°C arm, 5.98?±?0.48; 6-day arm, 6.72?±?0.23). PAXgene samples showed comparable RNA integrity in both baseline and 37°C arms (8.42?±?0.17; 7.92?±?0.1 respectively) however significant degradation was observed in the 6-day arm (3.19?±?1.32). Gene expression scores on RSM were highly correlated between the baseline and 37°C and 6-day study arms (median r?=?0.96, 0.95 respectively), as was the correlation to PAXgene tubes (median r?=?0.95, p?collecting, shipping, and storing RNA for gene expression assays.

2014-01-01

225

Mass concentration and mineralogical characteristics of aerosol particles collected at Dunhuang during ACE-Asia  

NASA Astrophysics Data System (ADS)

Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317 mu g m(-3) and 307 mu g m(-3) respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095 mu g m(-3), while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196 mu g m(-3) on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite (K/C) ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back- trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust.

Shen, Z. X.; Cao, J. J.; Li, X. X.; Okuda, T.; Wang, Y. Q.; Zhang, X. Y.

2006-03-01

226

Spatial distribution of biogenic sulphur compounds in the Arctic aerosol collected during the AREX 2011 and 2012 Oceania ship cruises  

NASA Astrophysics Data System (ADS)

The sea area between Norway and Svalbard Islands (Norwegian and Greenland Seas) is a critical site to study the effects of the climate change on the high-latitude Northern-Hemisphere regions. In particular, changes in extension and/or in the persistence of annual sea-ice, availability of nutrients and trace-elements in the biological-active marine layers and sea surface temperatures could affect the marine primary productivity and the emission into the atmosphere of dimethylsulphide (DMS), produced by phytoplankton metabolic processes. This volatile compound is oxidised in the atmosphere mainly to sulphuric acid and Methanesulphonic acid (MSA), which undergo gas-to-particle processes and form secondary sub-micrometric aerosol particles. In this way, they play a relevant role as cloud concentration nuclei (CCN), therefore controlling the climate through scattering/absorption of solar irradiation and changes in cloud coverage (and so affecting albedo). Here, we report the spatial distribution of MSA and H2SO4 measured on 12-h aerosol samples (PM10) collected during two summer cruises of the Oceania ship (AREX 2011 and 2012 oceanographic cruises). The samples were collected on Teflon filters along several marine transects starting from Tromso (Norway) to Svalbard Island and along the Western side of Svalbard Islands. S-compounds distribution was also compared with the organic carbon (OC) aerosol fraction, determined by a EC/OC thermo-optical analyser, and with the atmospheric concentration of selected carboxylic acids (measured by ion chromatography). Preliminary results on the AREX 2011 aerosol samples show two sharp maxima of non-sea-salt sulphate and MSA in June, in phase one with each other, while lower contribution of biogenic emission are recorded in the filters collected in July. Besides, no clear trend along coastal to open-sea transects is evident. Higher MSA concentrations (up to 120 ng/m3) were measured near the Norwegian coast, along the Tromso-Svalbard route, and in the south-west coastal areas of the Svalbard Island, while the lowest values (few ng/m3) were found in the open-sea at north-west of the Islands. The Particulate Organic Matter (POM) fraction, reconstructed by the OC measurements, covers about 33% of the PM10 mass, so constituting a major component of the marine Arctic aerosol collected in this area.

Udisti, Roberto; Rugi, Francesco; Becagli, Silvia; Bolzacchini, Ezio; Calzolai, Giulia; Chiari, Massimo; Frosini, Daniele; Ghedini, Costanza; Marconi, Miriam; Grazia Perrone, Maria; Sangiorgi, Giorgia; Severi, Mirko; Traversi, Rita; Walczowski, Waldek; Zielinski, Timon

2013-04-01

227

Spatial distribution and temporal variation of chemical species in the bulk atmospheric aerosols collected at the Okinawa archipelago, Japan  

NASA Astrophysics Data System (ADS)

The economic development and population growth in recent Asia have been increasing air pollution. A computer simulation study showed that air pollutants emitted from Asian continent could spread quickly within northern hemisphere. We initiated a study to elucidate the special distribution and chemical characterization of atmospheric aerosols around Okinawa archipelago, Japan. Okinawa Island is situated approximately 1500 km south of Tokyo, Japan, 2000 km southeast of Beijing, China, and 1000 km south of South Korea. Its location in Asia is well suited for studying long-range transport of air pollutants in East Asia because maritime air mass prevails during summer, while continental air mass dominates during fall, winter, and spring. The maritime air mass data can be seen as background and can be compared with continental air masses which have been affected by anthropogenic activities. We simultaneously collected bulk aerosol samples by using the same types of high volume air samplers at Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS, Okinawa Island), Kume Island (ca. 160 km south-west of CHAAMS) and Minami-daitou Island (ca. 320 km south-east of CHAAMS). We determined the concentrations of water-soluble anions, cations and dissolved organic carbon (DOC) using ion chromatography, atomic absorption spectrometry, and total organic carbon analyzer, respectively. We report and discuss spatial distribution and temporal variation of chemical species concentrations in bulk atmospheric aerosols collected during July, 2008 to July, 2009. We determine “background” concentration of chemical components in Okinawa archipelago. We then compare each chemical component among CHAAMS, Kume Island and Minami-daito Island to elucidate the influence of the long-range transport of chemical species from Asian continent.

Handa, D.; Somada, Y.; Ijyu, M.; Azechi, S.; Nakaema, F.; Arakaki, T.; Tanahara, A.

2009-12-01

228

Chemically segregated optical and microphysical properties of ambient aerosols measured in a single-particle mass spectrometer  

NASA Astrophysics Data System (ADS)

This paper describes results from the first direct measurements of the size-resolved optical properties as a function of chemical mixing states for atmospheric particle types sampled in Mexico City and Riverside, California. The coupled size, chemistry, and optical measurements were used to derive refractive indices and effective densities for chemically distinct particle mixing states. On the basis of the measured dependence of scattering intensity as a function of relative humidity and size, the Riverside particles contained detectable amounts of liquid water, whereas the Mexico City particles were relatively dry. Aerosol particles in Mexico City were observed to exhibit a wide range of densities (1.1-3.4 g/cm3), suggesting a dynamic, externally mixed aerosol population. Daily variations were observed as the particles in Mexico City underwent photochemical aging processes leading to a diurnal variation in particle morphology. In contrast, the optical properties of the Riverside aerosol, sampled during the fall season, were strongly impacted by the condensation of water and ammonium nitrate during periods of intense pollution buildup, resulting in microphysical properties that were similar across mixing states for a specific relative humidity.

Moffet, Ryan C.; Qin, Xueying; Rebotier, Thomas; Furutani, Hiroshi; Prather, Kimberly A.

2008-06-01

229

Particle Characterization and Ice Nucleation Efficiency of Field-Collected Aerosol Particles  

NASA Astrophysics Data System (ADS)

Atmospheric ice formation by heterogeneous nucleation is one of the least understood processes resulting in cirrus and mixed-phase clouds which affect the global radiation budget, the hydrological cycle, and water vapor distribution. In particular, how organic aerosol affect ice nucleation is not well understood. Here we report on heterogeneous ice nucleation from particles collected during the CalNex campaign at the Caltech campus site, Pasadena, on May 19, 2010 at 6am-12pm (A2) and 12pm-6pm (A3) and May 23 at 6am-12pm (B2) and 6pm-12am (B4). The ice nucleation onsets and water uptake were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). The ice nucleation efficiency was related to the particle chemical composition. Single particle characterization was provided by using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The STXM/NEXAFS analysis indicates that the morning sample (A2) constitutes organic particles and organic particles with soot and inorganic inclusions. The afternoon sample (A3) is dominated by organic particles with a potentially higher degree of oxidation associated with soot. The B2 sample shows a higher number fraction of magnesium-containing particle indicative of a marine source and ~93% of the particles contained sulfur besides oxygen and carbon as derived from CCSEM/EDX analysis. The B4 sample lacks the strong marine influence and shows higher organic content. Above 230 K, we observed water uptake followed by condensation freezing at mean RH of 93-100% and 89-95% for A2 and A3, respectively. This indicates that the aged A3 particles are efficient ice nuclei (IN) for condensation freezing. Below 230 K A2 and A3 induced deposition ice nucleation between 125-155% RHice (at mean values of 134-150% RHice). The B2 and B4 samples induced deposition ice nucleation below 230 K as low as 120% RHice, took up water at about 80% RH, and nucleated subsequently via condensation freezing above 230 K at mean RH of 88-94% and 89-100%, respectively. Experimentally derived ice nucleation rate coefficients and activated IN fractions for estimation of ice crystal production rates are presented. Particles sampled in the L.A. area can induce ice formation at conditions typical for cirrus and mixed-phase clouds and exhibit significantly different ice nucleation efficiencies than particles sampled in and around Mexico City.

Wang, B.; Gilles, M. K.; Laskin, A.; Moffet, R.; Nizkorodov, S.; Roedel, T.; Sterckx, L.; Tivanski, A.; Knopf, D. A.

2011-12-01

230

A single-particle characterization of a mobile Versatile Aerosol Concentration Enrichment System for exposure studies  

Microsoft Academic Search

BACKGROUND: An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2–2.6 ?m produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL). The data were collected during a study of human exposure to CAPs, in

Evelyn J Freney; Mathew R Heal; Robert J Donovan; Nicholas L Mills; Kenneth Donaldson; David E Newby; Paul HB Fokkens; Flemming R Cassee

2006-01-01

231

An assessment of the performance of the Monitor for AeRosols and GAses in ambient air (MARGA): a semi-continuous method for soluble compounds  

NASA Astrophysics Data System (ADS)

Ambient air monitoring as part of the US Environmental Protection Agency's (US EPA's) Clean Air Status and Trends Network (CASTNet) currently uses filter packs to measure weekly integrated concentrations. The US EPA is interested in supplementing CASTNet with semi-continuous monitoring systems at select sites to characterize atmospheric chemistry and deposition of nitrogen and sulfur compounds at higher time resolution than the filter pack. The Monitor for AeRosols and GAses in ambient air (MARGA) measures water-soluble gases and aerosols at an hourly temporal resolution. The performance of the MARGA was assessed under the US EPA Environmental Technology Verification (ETV) program. The assessment was conducted in Research Triangle Park, North Carolina, from 8 September to 8 October 2010 and focused on gaseous SO2, HNO3, and NH3 and aerosol SO42-, NO3-, and NH4+. Precision of the MARGA was evaluated by calculating the median absolute relative percent difference (MARPD) between paired hourly results from duplicate MARGA units (MUs), with a performance goal of ? 25%. The accuracy of the MARGA was evaluated by calculating the MARPD for each MU relative to the average of the duplicate denuder/filter pack concentrations, with a performance goal of ? 40%. Accuracy was also evaluated by using linear regression, where MU concentrations were plotted against the average of the duplicate denuder/filter pack concentrations. From this, a linear least squares line of best fit was applied. The goal was for the slope of the line of best fit to be between 0.8 and 1.2. The MARGA performed well in comparison to the denuder/filter pack for SO2, SO42-, and NH4+, with all three compounds passing the accuracy and precision goals by a significant margin. The performance of the MARGA in measuring NO3- could not be evaluated due to the different sampling efficiency of coarse NO3- by the MUs and the filter pack. Estimates of "fine" NO3- were calculated for the MUs and the filter pack. Using this and results from a previous study, it is concluded that if the MUs and the filter pack were sampling the same particle size, the MUs would have good agreement in terms of precision and accuracy. The MARGA performed moderately well in measuring HNO3 and NH3, though neither met the linear regression slope goals. However, recommendations for improving the measurement of HNO3 and NH3 are discussed. It is concluded that SO42-, SO2, NO3-, HNO3, NH4+, and NH3 concentrations can be measured with acceptable accuracy and precision when the MARGA is operated in conjunction with the recommendations outlined in the manuscript.

Rumsey, I. C.; Cowen, K. A.; Walker, J. T.; Kelly, T. J.; Hanft, E. A.; Mishoe, K.; Rogers, C.; Proost, R.; Beachley, G. M.; Lear, G.; Frelink, T.; Otjes, R. P.

2014-06-01

232

An assessment of the performance of the Monitor for AeRosols and GAses in ambient air (MARGA): a semi-continuous method for soluble compounds  

NASA Astrophysics Data System (ADS)

Ambient air monitoring as part of the US Environmental Protection Agency's (US EPA's) Clean Air Status and Trends Network (CASTNet) currently uses filter packs to measure weekly integrated concentrations. The US EPA is interested in supplementing CASTNet with semi-continuous monitoring systems at select sites to characterize atmospheric chemistry and deposition of nitrogen and sulfur compounds at higher time resolution than the filter pack. The Monitor for AeRosols and GAses in ambient air (MARGA) measures water-soluble gases and aerosols at hourly temporal resolution. The performance of the MARGA was assessed under the US EPA Environmental Technology Verification (ETV) program. The assessment was conducted in Research Triangle Park, North Carolina from 8 September-8 October 2010 and focused on gaseous SO2, HNO3 and NH3 and aerosol SO4-, NO3- and NH4+. Precision of the MARGA was evaluated by calculating the median absolute relative percent difference (MARPD) between paired hourly results from duplicate MARGA units (MUs), with a performance goal of <25%. The accuracy of the MARGA was evaluated by calculating the median absolute relative percent difference (MARPD) for each MU relative to the average of the duplicate denuder/filter pack concentrations, with a performance goal of ?40%. Accuracy was also evaluated by using linear regression, where MU concentrations were plotted against the average of the duplicate denuder/filter pack concentrations. From this, a linear least squares line of best fit was applied. The goal was for the slope of the line of best fit to be between 0.8 and 1.2. The MARGA performed well in comparison to the denuder/filter pack for SO2, SO42- and NH4+, with all three compounds passing the accuracy and precision goals by a significant margin. The performance of the MARGA in measuring NO3- could not be evaluated due to the different sampling efficiency of coarse NO3- by the MUs and the filter pack. Estimates of "fine" NO3- were calculated for the MUs and the filter pack. Using this and results from a previous study, it is concluded that if the MUs and the filter pack were sampling the same particle size, the MUs would have good agreement in terms of precision and accuracy. The MARGA performed moderately well in measuring HNO3 and NH3, though neither met the linear regression slope goals. However, recommendations for improving the measurement of HNO3 and NH3 are discussed. It is concluded that SO42-, SO2, NO3-, HNO3, NH4+ and NH3 concentrations can be measured with acceptable accuracy and precision when the MARGA is operated in conjunction with the recommendations outlined in the manuscript.

Rumsey, I. C.; Cowen, K. A.; Walker, J. T.; Kelly, T. J.; Hanft, E. A.; Mishoe, K.; Rogers, C.; Proost, R.; Beachley, G. M.; Lear, G.; Frelink, T.; Otjes, R. P.

2013-09-01

233

DEVELOPMENT OF A TAMPER RESISTANT/INDICATING AEROSOL COLLECTION SYSTEM FOR ENVIRONMENTAL SAMPLING AT BULK HANDLING FACILITIES  

SciTech Connect

Environmental sampling has become a key component of International Atomic Energy Agency (IAEA) safeguards approaches since its approval for use in 1996. Environmental sampling supports the IAEA's mission of drawing conclusions concerning the absence of undeclared nuclear material or nuclear activities in a Nation State. Swipe sampling is the most commonly used method for the collection of environmental samples from bulk handling facilities. However, augmenting swipe samples with an air monitoring system, which could continuously draw samples from the environment of bulk handling facilities, could improve the possibility of the detection of undeclared activities. Continuous sampling offers the opportunity to collect airborne materials before they settle onto surfaces which can be decontaminated, taken into existing duct work, filtered by plant ventilation, or escape via alternate pathways (i.e. drains, doors). Researchers at the Savannah River National Laboratory and Oak Ridge National Laboratory have been working to further develop an aerosol collection technology that could be installed at IAEA safeguarded bulk handling facilities. The addition of this technology may reduce the number of IAEA inspector visits required to effectively collect samples. The principal sample collection device is a patented Aerosol Contaminant Extractor (ACE) which utilizes electrostatic precipitation principles to deposit particulates onto selected substrates. Recent work has focused on comparing traditional swipe sampling to samples collected via an ACE system, and incorporating tamper resistant and tamper indicating (TRI) technologies into the ACE system. Development of a TRI-ACE system would allow collection of samples at uranium/plutonium bulk handling facilities in a manner that ensures sample integrity and could be an important addition to the international nuclear safeguards inspector's toolkit. This work was supported by the Next Generation Safeguards Initiative (NGSI), Office of Nonproliferation and International Security (NIS), National Nuclear Security Administration (NNSA).

Sexton, L.

2012-06-06

234

Estimation of size-resolved ambient particle density based on the measurement of aerosol number, mass, and chemical size distributions in the winter in Beijing.  

PubMed

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm(-3) and 1.62 ± 0.38 g cm(-3) for PM(1.8) and 1.73 ± 0.14 g cm(-3) and 1.67 ± 0.37 g cm(-3) for PM(10). Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 ?m to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 ?m during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles. PMID:22458861

Hu, Min; Peng, Jianfei; Sun, Kang; Yue, Dingli; Guo, Song; Wiedensohler, Alfred; Wu, Zhijun

2012-09-18

235

Visible spectroscopy of aerosol particles collected on filters: iron-oxide minerals  

Microsoft Academic Search

Diffuse reflectance spectrometry was used to investigate the reflectance characteristics of aerosol particles captured on bulk filters from Bermuda, Barbados, and Izaña. First derivatives of the spectra were examined for signals from two iron-oxide minerals, hematite and goethite, at 555 and 435nm, respectively, and the spectra and peaks were evaluated relative to the iron concentrations on the filters. The percent

R. Arimoto; W. Balsam; C. Schloesslin

2002-01-01

236

SingleParticle Characterization of Atmospheric Aerosols Collected at Gosan, Korea, during the Asian Pacific Regional Aerosol Characterization Experiment Field Campaign Using Low-Z (Atomic Number) Particle Electron Probe X-ray Microanalysis  

Microsoft Academic Search

A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), namely low-Z (atomic number) particle EPMA, was used to characterize the chemical compositions of the individual aerosol particles collected at the Gosan supersite, Jeju Island, Korea, as a part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). On 4–10 April 2001 just before a severe dust storm arrived, seven sets of

Hong Geng; Fangqin Cheng; Chul-Un Ro

2011-01-01

237

Elevated nitrogen-containing particles observed in Asian dust aerosol samples collected at the marine boundary layer of the Bohai Sea and the Yellow Sea  

NASA Astrophysics Data System (ADS)

Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5-10 ?m and 1.0-2.5 ?m, respectively) in six samples collected on 28 April-1 May 2006 in the marine boundary layer (MBL) of the Bohai Sea and Yellow Sea was conducted. Three samples (D1, D2, and D3) were collected along the Bohai Bay, Bohai Straits, and Yellow Sea near Korea during an Asian dust storm event while the other three samples (N3, N2, and N1) were collected on non-Asian dust (NAD) days. Based on X-ray spectral and secondary electron image data, 15 different types of particles were identified, in which soil-derived particles were encountered with the largest frequency, followed by (C, N, O)-rich droplets (likely the mixture of organic matter and NH4NO3), particles of marine origin, and carbonaceous, Fe-rich, fly ash, and (C, N, O, S)-rich droplet particles. Results show that during the Asian dust storm event relative abundances of the (C, N, O)-rich droplets and the nitrate-containing secondary soil-derived particles were markedly increased (on average by a factor of 4.5 and 2, respectively in PM2.5-10 fraction and by a factor of 1.9 and 1.5, respectively in PM1.0-2.5 fraction) in the MBL of the Bohai Sea and Yellow Sea, implying that Asian dust aerosols in springtime are an important carrier of gaseous inorganic nitrogen species, especially NOx (or HNO3) and NH3.

Geng, H.; Park, Y.; Hwang, H.; Kang, S.; Ro, C.-U.

2009-09-01

238

Elevated nitrogen-containing particles observed in Asian dust aerosol samples collected at the marine boundary layer of the Bohai Sea and the Yellow Sea  

NASA Astrophysics Data System (ADS)

Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5-10 ?m and 1.0-2.5 ?m, respectively) in six samples collected on 28 April-1 May 2006 in the marine boundary layer (MBL) of the Bohai Sea and Yellow Sea was conducted. Three samples (D1, D2, and D3) were collected along the Bohai Bay, Bohai Straits, and Yellow Sea near Korea during an Asian dust storm event while the other three samples (N3, N2, and N1) were collected on normal days. Based on X-ray spectral and secondary electron image data, 15 different types of particles were identified, in which soil-derived particles were encountered with the largest frequency, followed by (C, N, O)-rich droplets (likely the mixture of organic matter and NH4NO3), particles of marine origin, and carbonaceous, Fe-rich, fly ash, and (C, N, O, S)-rich droplet particles. Results show that during the Asian dust storm event relative abundances of the (C, N, O)-rich droplets and the nitrate-containing secondary soil-derived particles were markedly increased (on average by a factor of 4.5 and 2, respectively in coarse fraction and by a factor of 1.9 and 1.5, respectively in fine fraction) in the MBL of the Bohai Sea and Yellow Sea, implying that Asian dust aerosols in springtime are an important carrier of gaseous inorganic nitrogen species, especially NOx (or HNO3) and NH3.

Geng, H.; Park, Y.-M.; Hwang, H.-J.; Kang, S.; Ro, C.-U.

2009-06-01

239

Evaluations of the Chemical Mass Balance Method for Determining Contributions of Gasoline and Diesel Exhaust to Ambient Carbonaceous Aerosols  

Microsoft Academic Search

The US. Department of Energy Gasoline\\/Diesel PM Split Study was conducted to assess the sources of uncertainties in using an organic compound–based chemical mass balance receptor model to quantify the relative contributions of emissions from gasoline (or spark ignition [SI]) and diesel (or compression ignition [CI]) engines to ambient concentrations of fine particulate matter (PM2.5) in California’s South Coast Air

Eric M. Fujita; David E. Campbell; William P. Arnott; Judith C. Chow; Barbara Zielinska; Jiun-Horng Tsai; Hung-Lung Chiang; Peter Gabele; William Crews; Richard Snow; Nigel Clark; W. Wayne; Douglas Lawson; Steven Brown; Anna Frankel; Sean Raffuse; Paul Roberts; Hilary Hafner; Darcy Anderson; Bart Eklund; Michelle Simon; Shekhar Regmi; Maneerat Ongwandee; Glenn Morrison; Mark Fitch; Rao Surampalli

2007-01-01

240

Summertime carbonaceous aerosols collected in the marine boundary layer of the Arctic Ocean  

Microsoft Academic Search

The chemistry, morphology, and microscale to nanoscale structures of carbonaceous aerosols from the marine boundary layer of the Arctic Ocean were investigated by a variety of electron microscopy techniques, including scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS). The relative levels of particles of black carbon (BC) were determined by electron paramagnetic resonance (EPR).

Zhouqing Xie; Joel D. Blum; Satoshi Utsunomiya; R. C. Ewing; Xinming Wang; Liguang Sun

2007-01-01

241

Study of aerosols collected in a speleotherapeutic cave situated below Budapest, Hungary  

NASA Astrophysics Data System (ADS)

The Szeml?hegy-cave is one of the well-known hydrothermal caves of the Rózsadomb area of Budapest, which have been used for speleotherapy of respiratory diseases for years. It is known from the periodically changing airborne radon activity concentration data, that airflow of seasonally reversed direction are formed along the cave passages and fissures due to the temperature difference between the surface and cave air. This means that an intensive interaction takes place between the cave and its environment. The pollution of nearby waters and the urban atmospheric air represents a real danger for these caves below Buda, which recently became the part of the UNESCO World Heritage. The study of cave aerosols should be very important from the point of view of either the control possibilities of the environmental impact or speleotherapy, and probably helps in getting acquainted with the cave-forming processes. In this work we applied our standard aerosol sampling method to the high-humidity environment of the caves, and we studied the elemental composition, size fractionation as well as the spatial distribution and the seasonal variation of cave aerosols. Thanks to the sensitivity of PIXE traces of anthropogenic pollution of the Budapest air are shown in the Szeml?hegy-cave. Measured elemental concentrations remained less than one-tenth the air quality standard valid for the increasingly protected areas.

Kertész, Zs.; Borbély-Kiss, I.; Hunyadi, I.

1999-04-01

242

Characterisation of individual aerosol particles collected during a haze episode in Incheon, Korea using the quantitative ED-EPMA technique  

NASA Astrophysics Data System (ADS)

A quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA), called low-Z particle EPMA, was used to analyse individual aerosol particles collected in Incheon, Korea on 13-18 October 2008 (a typical haze episode occurred from 15 to 18 October). Overall 3600 individual particles in PM2.5-10 and PM1.0-2.5 fractions from 12 aerosol samples collected on haze and non-haze days were analysed. The analysed particles were classified, based on their X-ray spectral data together with their secondary electron images. The major particle types included organic carbon (OC), elemental carbon (EC), sea-salt, mineral dust (such as aluminosilicate, SiO2, CaCO3/CaMgCO3, etc.), (NH4)2SO4/NH4HSO4-containing, K-containing, Fe-rich and fly ash particles. Their relative number abundance results showed that OC particles were significantly increased while sea-salts and mineral dust particles were significantly decreased (especially in PM1.0-2.5 fraction) when haze occurred. For the other particle types (except Fe-rich particles in PM2.5-10 fraction), there were no significant differences in their relative abundances between haze and non-haze samples. On non-haze days, the nitrate-containing reacted sea-salt and mineral dust particles in PM1.0-2.5 fraction significantly outnumbered the sulfate-containing ones, whereas it was the reverse on haze days, implying that on haze days there were special sources or formation mechanisms for fine aerosol particles (?2.5 ?m in aerodynamic diameter). The emission of air pollutants from motor vehicles and stagnant meteorological conditions, such as low wind speed and high relative humidity, might be responsible for the elevated level of OC particles on haze days.

Geng, H.; Ryu, J. Y.; Maskey, S.; Jung, H.-J.; Ro, C.-U.

2011-02-01

243

Monitoring of inorganic ions, carbonaceous matter and mass in ambient aerosol particles with online and offline methods  

NASA Astrophysics Data System (ADS)

Year-long high timeresolution measurements of major chemical components in atmospheric sub-micrometer particles were conducted at an urban background station in Finland 2006-2007. Ions were analyzed using a particle-into-liquid sampler combined with an ion chromatograph (PILS-IC), organic and elemental carbon (OC and EC) by using a semicontinuos OC/EC aerosol carbon analyzer (RT-OCEC), and PM2.5 mass with a tapered element oscillating microbalance (TEOM). Long time series provides information on differences between the used measurement techniques as well as information about the diurnal and seasonal changes. Chemical mass closure was constructed by comparing the identified aerosol mass with the measured PM2.5. The sum of all components measured online (ions, particulate organic matter (POM), EC) represented only 65% of the total PM2.5 mass. The difference can be explained by the difference in cutoff sizes (PM1 for online measurements, PM2.5 for total mass) and by evaporation of the semivolatile/volatile components. In general, some differences in results were observed when the results of the continuous/semicontinuous instruments were compared with those of the conventional filter samplings. For non-volatile compounds, like sulfate and potassium, correlation between the filter samples and the PILS was good but greater differences were observed for the semivolatile compounds like nitrate and ammonium. For OC the results of the RT-OCEC were on average 10% larger than those of the filters. When compared to filter measurements, high resolution measurements provide important data on short pollution plumes as well as on diurnal changes. Clear seasonal and diurnal cycles were observed for nitrate and EC.

Timonen, H.; Aurela, M.; Saarnio, K.; Frey, A.; Saarikoski, S.; Teinilä, K.; Kulmala, M.; Hillamo, R.

2011-10-01

244

Analysis of the water-soluble organic content of submicron aerosols formed from the in-situ replication of marine bubble bursting processes  

NASA Astrophysics Data System (ADS)

Both primary and secondary ocean-derived aerosols contribute significantly to the global aerosol population and thus to the Earth’s radiative budget. Primary marine aerosols are generated from sea spray. These primary marine aerosols contain sea salt as well as organic and inorganic matter from ocean biota incorporated into the aerosol during bubble-bursting processes near the ocean’s surface. Identifying and quantifying the sources and composition of the organic content in submicron primary marine aerosols will help in determining and modeling its climate impact related to aerosol direct radiative forcing and cloud nucleating properties. Onboard the RV Atlantis during the recent CalNex 2010 field mission, an attempt was made to measure in-situ the aerosols formed from bubble bursting processes in the ocean by bubbling particle-free air into the ocean through stainless steel frits. The resulting submicron aerosol samples were collected using a 2-stage impactor. Additionally, particulate organic carbon seawater samples representative of the local ocean water were collected. Both the seawater and simulated primary marine aerosol samples were analyzed for their water soluble organic content using liquid chromatography and mass spectroscopy. The results were compared to gain knowledge about the direct transfer of organic matter from the ocean to the atmosphere. Ambient submicron aerosol samples were also collected throughout the research cruise and analyzed. Specific compounds targeted were carbohydrates, organic acids, and amines. Results from the analysis of seawater, aerosol generated from bubbled seawater, and ambient aerosol samples will be presented.

Dewitt, H.; Quinn, P.; Bates, T. S.; Coffman, D. J.; Schulz, K.

2010-12-01

245

Development of infrared photothermal deflection spectroscopy (mirage effect) for analysis of condensed-phase aerosols collected in a micro-orifice uniform deposit impactor.  

PubMed

The potential of mid-infrared photothermal deflection spectrometry for aerosol analysis is demonstrated. Ammonium nitrate aerosols are deposited on a flat substrate using a micro-orifice uniform deposit impactor (MOUDI). Photothermal spectroscopy with optical beam deflection (mirage effect) is used to detect deposited aerosols. Photothermal deflection from aerosols is measured by using pulsed infrared laser light to heat up aerosols collected on the substrate. The deflection signal is obtained by measuring the position of a spot from a beam of light as it passes near the heated surface. The results indicate non-rotating impaction as the preferred MOUDI impaction method. Energy-dependent photothermal measurement shows a linear relationship between signal and laser intensity, and no loss of signal with time is observed. The detection limit from the signal-mass curve is 7.31 ng. For 30 minutes collection time and 30 L/min flow rate of the impactor, the limit of detection in terms of aerosol mass concentration is 0.65 microg m(-3). PMID:19094392

Dada, Oluwatosin O; Bialkowski, Stephen E

2008-12-01

246

Organosulfate formation in biogenic secondary organic aerosol.  

PubMed

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

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

2008-09-11

247

RADIOCARBON MEASUREMENT OF THE BIOGENIC CONTRIBUTION TO SUMMERTIME PM 2.5 AMBIENT AEROSOL IN NASHVILLE, TN  

EPA Science Inventory

Radiocarbon (14C) measurements performed on PM-2.5 samples collected near Nashville, TN from June 21 to July 13, 1999, showed high levels of modern carbon, ranging from 56 to 80% of the total carbon in the samples. Radiocarbon measurements performed on dichloromethane extracts of...

248

Spectral light absorption by ambient aerosols influenced by biomass burning in the Amazon Basin I. Comparison and field calibration of absorption measurement techniques  

Microsoft Academic Search

Spectral aerosol light absorption is an important parameter for the assessment of the radiation budget of the atmosphere. Although on-line measurement techniques for aerosol light absorption, such as the Aethalometer and the Particle Soot Absorption Photometer (PSAP), have been available for two decades, they are limited in accuracy and spectral resolution because of the need to deposit the aerosol on

O. Schmid; P. Artaxo; W. P. Arnott; D. Chand; L. V. Gatti; G. P. Frank; A. Hoffer; M. Schnaiter; M. O. Andreae

2005-01-01

249

Spectral light absorption by ambient aerosols influenced by biomass burning in the Amazon Basin. I: Comparison and field calibration of absorption measurement techniques  

Microsoft Academic Search

Spectral aerosol light absorption is an important parameter for the assessment of the radiation budget of the atmosphere. Although on-line measurement techniques for aerosol light absorption, such as the Aethalometer and the Particle Soot Absorption Photometer (PSAP), have been available for two decades, they are limited in accuracy and spectral resolution because of the need to deposit the aerosol on

O. Schmid; P. Artaxo; W. P. Arnott; D. Chand; L. V. Gatti; G. P. Frank; A. Hoffer; M. Schnaiter; M. O. Andreae

2006-01-01

250

Source estimation of anthropogenic aerosols collected by a DRUM sampler during spring of 2002 at Gosan, Korea  

Microsoft Academic Search

Continuous measurements of trace elements in size-segregated aerosols were performed by X-ray fluorescence analysis in order to assess the transport of natural and anthropogenic aerosol sources to Gosan site in springtime 2002. Various aerosol elemental components (such as Al, Ca, Si, K, Ti, and Mn) had low enrichment factors close to one and exhibited a similar temporal variation in coarse

J. S. Han; K. J. Moon; S. Y. Ryu; Y. J. Kim; Kevin D. Perry

2005-01-01

251

An investigation into the acid content of aerosols in the ambient air at the Taj Mahal, Agra.  

PubMed

A chemical analysis of suspended particulate matter (SPM) collected near the world famous Taj Mahal monument at Agra has been carried out. SPM samples collected on glass fibre filters were analysed for water-soluble sulphate, nitrate, chloride and ammonium ions. The data were derived from over 200 samples (each of 24 h), collected continuously during the winter periods (October through to March) of 1984-1985 and 1985-1986. The SO(4)(2-) and NO(3)(-) components are acidic in nature causing corrosion and effects on visibility, and so were studied in more detail. Mean values for SO(4)(2-) and NO(3)(-) derived from two-year data are 7.2 microg m(-3) and 8.2 microg m(-3), respectively. The SO(4)(2-)/SO(2) and NO(3)(-)/NO(2) ratiosobserved indicate faster conversion of SO(2) to SO(4)(2-) than NO(2) to NO(3)(-), the maximum levels being in January. Thus, both SO(4)(2-) and NO(3)(-) results appear to offer more promising indices of air quality than do SPM data alone. PMID:15092423

Joshi, S D; Pandya, G H; Phadke, K M; Tajne, D S; Jain, A K; Gajrani, C P; Yennawar, P K

1989-01-01

252

Online determination of levoglucosan in ambient aerosols with Particle-into-Liquid Sampler - High-Performance Anion-Exchange Chromatography - Mass Spectrometry (PILS-HPAEC-MS)  

NASA Astrophysics Data System (ADS)

Biomass burning, such as domestic heating, agricultural, and wild open-land fires, has a significant influence on the atmosphere at the global and, especially, at the local scale. Levoglucosan has been shown to be a good tracer for biomass burning emissions in atmospheric particulate matter and several analytical techniques have been presented for the determination of levoglucosan from filter samples. In this paper, a novel combination of a Particle-into-Liquid Sampler (PILS) to a high-performance anion-exchange chromatograph (HPAEC) with the detection by a mass spectrometer (MS) is presented for the online analysis of levoglucosan in ambient particles. The PILS-HPAEC-MS technique enables a fast online analysis of levoglucosan from the particulate samples. The method was tested at an urban background station in Helsinki, Finland, in winter 2011. A comparison with simultaneous levoglucosan measurements from filter samples by the HPAEC-MS was performed and it showed a good agreement between the online and offline methods. Additionally, the online levoglucosan data were compared with the biomass burning tracer fragments measured by a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). As there were no local biomass burning sources close to the measurement station, online levoglucosan measurements revealed that most of the particles from biomass burning were either regionally distributed or long-range transported in the urban background of Helsinki. The average levoglucosan concentrations were relatively low (average 0.083 ?g m-3) during the measurement campaign. The highest concentration peak measured for levoglucosan (1.4 ?g m-3) seemed to originate from biomass burning in Eastern Europe, likely in Estonia, that was transported to Helsinki.

Saarnio, K.; Teinilä, K.; Saarikoski, S.; Carbone, S.; Gilardoni, S.; Timonen, H.; Aurela, M.; Hillamo, R.

2013-06-01

253

Online determination of levoglucosan in ambient aerosols with particle-into-liquid sampler - high-performance anion-exchange chromatography - mass spectrometry (PILS-HPAEC-MS)  

NASA Astrophysics Data System (ADS)

Biomass burning, such as domestic heating, agricultural, and wild open-land fires, has a significant influence on the atmosphere at the global and, especially, at the local scale. Levoglucosan has been shown to be a good tracer for biomass burning emissions in atmospheric particulate matter, and several analytical techniques have been presented for the determination of levoglucosan from filter samples. In this paper, a novel combination of a particle-into-liquid sampler (PILS) to a high-performance anion-exchange chromatograph (HPAEC) with the detection by a mass spectrometer (MS) is presented for the online analysis of levoglucosan in ambient particles. The PILS-HPAEC-MS technique enables a fast online analysis of levoglucosan from the particulate samples. The method was tested at an urban background station in Helsinki, Finland, in winter 2011. A comparison with simultaneous levoglucosan measurements from filter samples by the HPAEC-MS was performed and it showed a good agreement between the online and offline methods. Additionally, the online levoglucosan data were compared with the biomass burning tracer fragments measured by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). As there were no local biomass burning sources close to the measurement station, online levoglucosan measurements revealed that most of the particles from biomass burning were either regionally distributed or long-range transported in the urban background of Helsinki. The average levoglucosan concentrations were relatively low (average 0.083 ?g m-3) during the measurement campaign. The highest concentration peak measured for levoglucosan (1.4 ?g m-3) seemed to originate from biomass burning in the Baltic countries, likely in Estonia, that was transported to Helsinki.

Saarnio, K.; Teinilä, K.; Saarikoski, S.; Carbone, S.; Gilardoni, S.; Timonen, H.; Aurela, M.; Hillamo, R.

2013-10-01

254

Atmospheric Aerosol Chemistry Analyzer: Demonstration of feasibility  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project objective was to demonstrate the technical feasibility of an Atmospheric Aerosol Chemistry Analyzer (AACA) that will provide a continuous, real-time analysis of the elemental (major, minor and trace) composition of atmospheric aerosols. The AACA concept is based on sampling the atmospheric aerosol through a wet cyclone scrubber that produces an aqueous suspension of the particles. This suspension can then be analyzed for elemental composition by ICP/MS or collected for subsequent analysis by other methods. The key technical challenge was to develop a wet cyclone aerosol sampler suitable for respirable particles found in ambient aerosols. We adapted an ultrasonic nebulizer to a conventional, commercially available, cyclone aerosol sampler and completed collection efficiency tests for the unit, which was shown to efficiently collect particles as small as 0.2 microns. We have completed the necessary basic research and have demonstrated the feasibility of the AACA concept.

Mroz, E.J.; Olivares, J.; Kok, G.

1996-04-01

255

Elemental composition of aerosol particulate matter collected on membrane filters: A comparison of results by PIXE and ICP-AES  

NASA Astrophysics Data System (ADS)

The elemental composition of aerosol matter (total suspended particles) collected on high-purity membrane filters during 24-h sampling periods with distinctly different pollution levels was analysed by proton-induced X-ray emission spectrometry (PIXE) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The mass density of the material deposited on 34-mm diameter filter areas ranged from 65 to 294 ?g/cm 2. Different spots on each sample as well as on blank reference filters were first analysed by PIXE (1.85 MeV protons, beam diameter 1.5 mm). Using a peak-fitting routine developed in-house together with an empirically determined sensitivity function, the background-corrected net spectra were converted to elemental yields. Absolute calibration was achieved by comparison against a thin-film copper standard prepared by evaporation. Following PIXE analysis, the whole filters with the aerosol deposits were digested by high-pressure ashing. A small amount of the dissolved material was analysed by ICP-AES using standard procedures. The mass fractions of elements in the particulate matter ranged from 6×10 -5 for Co to 0.1 for Ca, with significant differences between the sampling periods. For some elements the mass fractions determined by PIXE showed a spot-to-spot variation by up to 30%. In most cases the mean elemental mass per filter determined by the two techniques agreed quite well, with a slight trend towards lower values by PIXE (10-15%). The difference is within the combined uncertainty of about 20%, estimated for elemental mass ratios determined by the two techniques. The Ti content determined by ICP-AES was always about 50% lower than by PIXE, the K content sometimes up to 30% higher. The discrepancy for Ti appears to reflect a digestion problem. The enhanced K content is attributed to a rather high instrumental background in ICP-AES.

Menzel, N.; Schramel, P.; Wittmaack, K.

2002-04-01

256

AN ELECTROSTATIC PRECIPITATOR FOR THE COLLECTION OF AEROSOL SAMPLES FOR PARTICLE SIZE ANALYSIS. Technical Progress Report  

Microsoft Academic Search

An electrostatic precipitator with which a sample suitable for particle ; size analysis can be collected from a few cubic centimeters of air is described. ; It operates at a volumetric flow rate of 5 cm³\\/min, equivalent to a linear ; velocity of 4-5 cm\\/sec. The entire sample is deposited in a small area on a ; single electron microscope

T. T. Mercer; M. I. Tillery; M. A. Flores

1963-01-01

257

FEASIBILITY OF THE AEROSOL-TO-LIQUID PARTICLE EXTRACTION SYSTEM (ALPES) FOR COLLECTION OF VIABLE FRANCISELLA SP.  

SciTech Connect

Several Biowatch monitoring sites in the Houston area have tested positive for Francisella tularensis and there is a need to determine whether natural occurring Francisella-related microorganism(s) may be responsible for these observed positive reactions. The collection, culturing and characterization of Francisella-related natural microorganisms will provide the knowledge base to improve the future selectivity of Biowatch monitoring for Francisella. The aerosol-to-liquid particle extraction system (ALPES) is a high-efficiency, dual mechanism collection system that utilizes a liquid collection medium for capture of airborne microorganisms. Since the viability of microorganisms is preserved better in liquid medium than on air filters, this project was undertaken to determine whether Francisella philomiragia and Francisella tularensis LVS maintain acceptable viability in the continuous liquid recirculation, high direct current voltage and residual ozone concentrations which occur during ALPES operation. Throughout a series of preliminary trial runs with representative gram-negative and gram-positive microorganisms, several design modifications and improvements to the ALPES optimized liquid handling, electrical stability, sampling and overall performance for biological sampling. Initial testing with Francisella philomiragia showed viability was preserved better in PBS buffer than HBSS buffer. Trial runs at starting cell concentrations of 1.8 x 10{sup 6} and 2.5 x 10{sup 4} CFU/L showed less than a 1-log decrease in viability for F. philomiragia after 24 h in the ALPES. Francisella tularensis LVS (live vaccine strain) was used as a surrogate for virulent F. tularensis in ALPES trial runs conducted at starting cell concentrations of 10{sup 4}, 10{sup 5} and 10{sup 6} CFU/L. F. tularensis LVS was slow-growing and required highly selective growth media to prevent overgrowth by collected airborne microorganisms. In addition, one ALPES unit intake was HEPA filtered during the final trial runs with F. tularensis LVS to further reduce the levels of microbial background. Results from trials with F. tularensis LVS showed about a 1-log loss decrease in CFUs after 24 h, but maintained final cell concentrations in the range of 10{sup 3}-10{sup 4} CFU/L. These results indicate that the ALPES maintains acceptable viability of Francisella sp. in PBS buffer for up to 24 h and is a promising technology for the collection of viable airborne Francisella or Francisella-related cultures which may be observed at Biowatch monitoring sites in the Houston area and elsewhere.

Heitkamp, M

2006-08-07

258

HOUSTON AEROSOL CHARACTERIZATION STUDY  

EPA Science Inventory

An intensive field study of ambient aerosols was conducted in Houston between September 14 and October 14, 1978. Measurements at 12 sites were made using (1) two relocatable monitoring systems instrumented for aerosol and gaseous pollutants, (2) a network of high volume samplers ...

259

The importance of new collection efficiency values including the effect of rear capture for the below-cloud scavenging of aerosol particles  

NASA Astrophysics Data System (ADS)

A numerical study is presented to evaluate the possible impact of recently measured collection scavenging efficiencies of aerosol particles by raindrops on the calculation of wet removal of pollution plumes by rain. These new collection efficiencies cover the previously undocumented range between 0.3 ?m and 3.5 ?m diameter for the aerosol particles and 2 to 2.6 mm diameter for the drops. They show for particles between 0.3 ?m and 0.7 ?m a region of an important increase of the efficiencies with decreasing particle size probably due to the capture of particles in the rear vortex developing behind the falling drop. This hypothesis was motivated by measurements using particle image velocimetry (PIV). Also for the particles larger than 1.5 ?m the efficiencies exceed old approximations by up to a factor of two.

Quérel, Arnaud; Monier, Marie; Flossmann, Andrea I.; Lemaitre, Pascal; Porcheron, Emmanuel

2014-06-01

260

Collection efficiency of the Soot-Particle Aerosol Mass Spectrometer (SP-AMS) for internally mixed particulate black carbon  

NASA Astrophysics Data System (ADS)

The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam-laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements are used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam-particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of two. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.

Willis, M. D.; Lee, A. K. Y.; Onasch, T. B.; Fortner, E. C.; Williams, L. R.; Lambe, A. T.; Worsnop, D. R.; Abbatt, J. P. D.

2014-05-01

261

In Situ Electrostatic Separation of Ambient PM2.5 into Source-Specific Fractions During Collection in a FRM Sampler  

SciTech Connect

Coal combustion is generally viewed as a major source of PM2.5 emissions into the atmosphere. For some time, toxicologists have been asking for an exposure environment enriched with the coal combustion source specific PM{sub 2.5} to conduct meaningful exposure studies to better understand the mechanisms of the adverse health effects of coal combustion specific PM2.5 in the ambient environment. There are several unique characteristics of primary PM generated from coal combustion. In this research project, an attempt has been made to exploit some of the unique properties of PM generated from coal fired power plants to preferentially separate them out from the rest of the primary and secondary PM in the ambient environment. An existing FRM sampler used for monitoring amount of PM{sub 2.5} in the ambient air is modified to incorporate an electrostatic field. A DC corona charging device is also installed at the ambient air inlet to impart positive or negative charge to the PM. Visual Basic software has been written to simulate the lateral movement of PM as it passes through the electrostatic separator under varying operating conditions. The PM samples collected on polycarbonate filters under varying operating conditions were extensively observed for clustering and/or separation of PM in the direction parallel to the electric field. No systematic PM separation was observed under any of the operating conditions. A solution to overcome this kind of turbulence caused remixing has been offered. However, due to major programmatic changes in the DOE UCR program, there are no venues available to further pursue this research.

Naresh Shah; Frank E. Huggins; Gerald P. Huffman

2006-07-31

262

Semi-automated bacterial spore detection system with micro-fluidic chips for aerosol collection, spore treatment and ICAN DNA detection.  

PubMed

A semi-automated bacterial spore detection system (BSDS) was developed to detect biological threat agents (e.g., Bacillus anthracis) on-site. The system comprised an aerosol sampler, micro-fluidic chip-A (for spore germination and cell lysis), micro-fluidic chip-B (for extraction and detection of genomic DNA) and an analyzer. An aerosol with bacterial spores was first collected in the collection chamber of chip-A with a velocity of 300 l/min, and the chip-A was taken off from the aerosol sampler and loaded into the analyzer. Reagents packaged in the chip-A were sequentially applied into the chamber. The genomic DNA extract from spore lyzate was manually transferred from chip-A to chip-B and loaded into the analyzer. Genomic DNA in chip-B was first trapped on a glass bead column, washed with various reagents, and eluted to the detection chamber by sequential auto-dispensing. Isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN) with fluorescent measurement was adopted to amplify and detect target DNA. Bacillus subtilis was the stimulant of biological warfare agent in this experiment. Pretreatment conditions were optimized by examining bacterial target DNA recovery in the respective steps (aerosol collection, spore germination, cell lysis, and DNA extraction), by an off-chip experiment using a real-time polymerase chain reaction quantification method. Without the germination step, B. subtilis spores did not demonstrate amplification of target DNA. The detection of 10(4) spores was achieved within 2h throughout the micro-fluidic process. PMID:19450964

Inami, Hisao; Tsuge, Kouichiro; Matsuzawa, Mitsuhiro; Sasaki, Yasuhiko; Togashi, Shigenori; Komano, Asuka; Seto, Yasuo

2009-07-15

263

Spectra Aerosol Light Scattering and Absorption for Laboratory and Urban Aerosol  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols considerably influence the climate, reduce visibility, and cause problems in human health. Aerosol light absorption and scattering are the important factors in the radiation transfer models. However, these properties are associated with large uncertainties in climate modeling. In addition, atmospheric aerosols widely vary in composition and size; their optical properties are highly wavelength dependent. This work presents the spectral dependence of aerosol light absorption and scattering throughout the ultraviolet to near-infrared regions. Data were collected in Reno, NV from 2008 to 2010. Also presented in this study are the aerosol optical and physical properties during carbonaceous aerosols and radiative effects study (CARES) conducted in Sacramento area during 2010. Measurements were made using photoacoustic instruments (PA), including a novel UV 355 nm PA of our design and manufacture. Comparative analyses are presented for three main categories: (1) aerosols produced by wildfires and traffic emissions, (2) laboratory-generated and wintertime ambient urban aerosols, and (3) urban plume and biogenic emissions. In these categories, key questions regarding the light absorption by secondary organic aerosols (SOA), so-called brown carbon (BrC), and black carbon (BC) will be discussed. An effort is made to model the emission and aging of urban and biomass burning aerosol by applying shell-core calculations. Multispectral PA measurements of aerosols light absorption and scattering coefficients were used to calculate the Angstrom exponent of absorption (AEA) and single scattering albedo (SSA). The AEA and SSA values were analyzed to differentiate the aerosol sources. The California wildfire aerosols exhibited strong wavelength dependence of aerosol light absorption with AEA as lambda -1 for 405 and 870 nm, in contrast to the relatively weak wavelength dependence of traffic emissions aerosols for which AEA varied approximately as lambda-1. By using a shell-core model, we verified, for the first time, that AEA can be as high as 1.6 even for non-absorbing coating on BC, suggesting that the organic coating need not be intrinsically brown to observe effects commonly attributed to BrC absorption. Additionally, for laboratory generated incense burning aerosols, AEA varied as lambda -4.5for wavelengths ranging from 355 to 1047 nm. In contrast, the wood smoke aerosols during winter had a much weaker wavelength dependence (lambda-1.1), comparable to that of traffic emission aerosols. During these observations, the multispectral SSA decreased with the wavelength for traffic-related emissions, yet it increased for biomass and incense burning aerosol. The strong spectral dependence was due to the enhanced light absorption by BrC at UV and blue wavelengths. In all cases, results of this analysis suggested that inefficient smoldering combustion processes can emit predominantly BrC, in comparison to high-temperature and flaming burning processes. During the CARES field campaign, aerosols were dominated by biogenic emissions. Aerosol light absorption was modestly enhanced (lambda -1.6) at shorter wavelengths (355, 375, 405, and 532 nm) compared to 870 and 1047 nm, likely due to the spectral dependence of coating on BC. The secondary organic aerosol (SOA) mass concentration steadily increased in the latter half of the campaign, with strong 355 nm aerosol light scattering. Overall, results of this field campaign showed that the biogenic SOA was not BrC, i.e. it didn't have intrinsic characteristics near UV absorption. These results should be further tested and analyzed to assess the full implications of BrC aerosol light absorption.

Gyawali, Madhu S.

264

A COMPARATIVE ASSESSMENT OF BOISE, IDAHO, AMBIENT AIR FINE PARTICLE SAMPLES USING THE PLATE AND MICROSUSPENSION SALMONELLA MUTAGENICITY ASSAYS  

EPA Science Inventory

The primary objective of this study is to characterize the genotoxic potential of the ambient air aerosols collected within an air shed impacted primarily by wood smoke and automotive emissions. The study also examines the relative merits of a microsuspension assay and the standa...

265

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

EPA Science Inventory

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

266

Spatial distribution and temporal variation of chemical species in the bulk atmospheric aerosols collected at the Okinawa archipelago, Japan  

Microsoft Academic Search

The economic development and population growth in recent Asia have been increasing air pollution. A computer simulation study showed that air pollutants emitted from Asian continent could spread quickly within northern hemisphere. We initiated a study to elucidate the special distribution and chemical characterization of atmospheric aerosols around Okinawa archipelago, Japan. Okinawa Island is situated approximately 1500 km south of

D. Handa; Y. Somada; M. Ijyu; S. Azechi; F. Nakaema; T. Arakaki; A. Tanahara

2009-01-01

267

Elevated nitrogen-containing particles observed in Asian dust aerosol samples collected at the marine boundary layer of the Bohai Sea and the Yellow Sea  

Microsoft Academic Search

Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5-10 mum and 1.0-2.5 mum, respectively) in six samples collected on 28 April-1 May

H. Geng; Y.-M. Park; H.-J. Hwang; S. Kang; C.-U. Ro

2009-01-01

268

Composition of California coastal marine aerosol particles measured during CalNex 2010 and E-PEACE 2011  

NASA Astrophysics Data System (ADS)

Marine aerosol particles play an important role in the earth's radiative balance, yet the sources and composition of the organic fraction remain largely unconstrained. Recent measurements have been made in order to characterize the sources, composition, and concentration of particles in the California coastal marine boundary layer. Ambient and generated marine aerosol particles were measured on board the R/V Atlantis during the CalNex 2010 campaign in May and June 2010. Particles were collected on filters and analyzed using Fourier transform infrared (FTIR) spectroscopy to determine the functional group composition and total organic mass. Particles from two primary marine aerosol generators showed similar organic compositions, both with larger fractions of hydroxyl functional groups. Similar ambient measurements were made on board the R/V Point Sur during July 2011. Ambient marine aerosol particles were collected on filters and analyzed using FTIR spectroscopy. Samples were collected 100 miles off the coast of Monterey, CA when winds were mainly from the west and had little anthropogenic influence. Marine aerosol particles were also analyzed using a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Particles were sampled under different ambient conditions including a range of seawater chlorophyll concentrations and a range of wind speeds and directions. Changes in the ambient conditions may influence changes in the organic functional group composition of the marine particles. Simultaneously, seawater was collected and atomized onto filters to determine the functional group composition of the total organic matter in the seawater. This organic composition will be compared to the organic composition of the ambient marine particles to determine the changes upon emission and aging in the atmosphere.

Frossard, A. A.; Modini, R.; Russell, L. M.; Wonaschuetz, A.; Sorooshian, A.; Kieber, D. J.; Maben, J. R.; Keene, W. C.; Bates, T. S.; Quinn, P.

2011-12-01

269

Bacterial communities in urban aerosols collected with wetted-wall cyclonic samplers and seasonal fluctuations of live and culturable airborne bacteria.  

PubMed

Airborne transmission of bacterial pathogens from point sources (e.g., ranches, dairy waste treatment facilities) to areas of food production (farms) has been suspected. Determining the incidence, transport and viability of extremely low levels of pathogens require collection of high volumes of air and characterization of live bacteria from aerosols. We monitored the numbers of culturable bacteria in urban aerosols on 21 separate days during a 9 month period using high volume cyclonic samplers at an elevation of 6 m above ground level. Culturable bacteria in aerosols fluctuated from 3 CFU to 6 million CFU/L of air per hour and correlated significantly with changes in seasonal temperatures, but not with humidity or wind speed. Concentrations of viable bacteria determined by fluorescence staining and flow cytometry correlated significantly with culturable bacteria. Members of the phylum Proteobacteria constituted 98% of the bacterial community, which was characterized using 16S rRNA gene sequencing using DNA from aerosols. Aquabacterium sp., previously characterized from aquatic environments, represented 63% of all clones and the second most common were Burkholderia sp; these are ubiquitous in nature and some are potential human pathogens. Whole genome amplification prior to sequencing resulted in a substantial decrease in species diversity compared to characterizing culturable bacteria sorted by flow cytometry based on scatter signals. Although 27 isolated colonies were characterized, we were able to culture 38% of bacteria characterized by sequencing. The whole genome amplification method amplified DNA preferentially from Phyllobacterium myrsinacearum, a minor member of the bacterial communities, whereas Variovorax paradoxus dominated the cultured organisms. PMID:22193549

Ravva, Subbarao V; Hernlem, Bradley J; Sarreal, Chester Z; Mandrell, Robert E

2012-02-01

270

Chemical composition of size-segregated aerosol collected all year-round at Concordia Station (Dome C, Antarctica). Transport processes and climatic implications.  

NASA Astrophysics Data System (ADS)

Ice-core stratigraphies of chemical components of atmospheric gases and aerosols trapped in the snow layers by scavenging processes are a powerful tool in understanding past climatic and environmental changes. The deep ice core drilled at Dome C in the framework of the EPICA project allowed reconstructing the last 8 glacial-interglacial cycles and highlightened the complex relationships between climatic forcings and environmental feedback processes. In interpreting ice core records as a function of past climatic variations, some difficulties arise from uncertainties in considering selected chemical species as reliable markers of climatic and environmental processes and in attributing the different load and composition of aerosols over Antarctica to changes in source intensity (such as aridity, wind strength, emersion of continental platform by sea-level lowering etc..) and/or to variations in atmospheric processes (such as meridional and zonal atmospheric circulation, polar vortex intensity, scavenging efficiency, transport pathways etc..). Besides, two new aspects are actually under discussions: the possible use of Na as sea-ice cover marker (via frost flower formation on the sea-ice surface during the pack-ice formation) and the identification of continental source areas for mineral dust reaching internal regions of Antarctica during glacial and interglacial periods. In order to better address such controversial issues, since 2005 a continuous, high temporal resolution size-segregated aerosol and surface snow sampling has been performed at Dome C (central East Antarctic Plateau, 75° 06' S, 123° 23' E), in the framework of "Station Concordia" Project (a Italian PNRA- French IPEV joint program). The chemical analysis of size-segregated aerosol and daily superficial snow samples, collected all year-round for more than 4 years, can contribute to clarify some of the above mentioned topics. In particular: the possible seasonal pattern of sea spray aerosol could be related to sea-ice formation timing and/or to changes in zonal wind intensity and atmospheric pathway; the mineralogical analysis of insoluble dust particles can allow the identification of continental sources, by comparison with soils collected in the potential source areas (PSAs); finally, the seasonal pattern of biogenic markers (such as methanesulphonic acid and non-sea-salt sulphate) can be linked to sea surface temperature, sea-ice cover and southern-hemisphere circulation modes (e.g., SOI, AAO or SAM and ACW). As regard as depositional and post-depositional processes, the analysis of chemical markers in aerosol, superficial snow and hoar crystals, sampled contemporaneously, will allow understanding the key factors (e.g., snow acidity, solar irradiation) affecting the preservation of components reversibly fixed in the snow layers (such as, for instance, methanesulphonic acid, nitrate and chloride). A summary of the major results from the chemical analysis of aerosol and snow collected at Dome C is here presented.

Udisti, Roberto; Becagli, Silvia; Frosini, Daniele; Galli, Gaia; Ghedini, Costanza; Rugi, Francesco; Severi, Mirko; Traversi, Rita

2010-05-01

271

Characterization of submicron aerosol particles collected during the MEGAPOLI experiment aboard the ATR-42 in Paris, France  

NASA Astrophysics Data System (ADS)

The chemical and physical properties of submicron aerosol particles were analyzed during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) campaign onboard the French ATR-42 aircraft. A total of 11 research flights (RF) were performed from July 9 to 29, 2009. The ATR-42 was equipped with a Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS), a Proton Transfer Mass Spectrometer (PTRMS), as well as measurements of ozone (O_3), carbon monoxide (CO), and nitrogen oxides (NO, NOy, and NOx). Meteorology measurements of temperature, wind speed, relative humidity, and liquid water content were also performed for each flight. Using the ToF-AMS, size-resolved chemical composition of non-refractory submicron particles (NR-PM1) were obtained at 1-min resolution. The average composition of NR-PM1 during this study was 53% organics, 27% sulfate, 7% nitrate, 12% ammonium, and 2% chloride. Strong contributions from SO_4 bearing particles are observed outside of the pollution plume, whereas Org-bearing particles are high within the plume. The mass concentrations of SO_4 bearing particles decrease as they encounter the pollution plume and at the same time there is an increase in organic mass concentration. These patterns suggest that there is competition between the formation of SO_4 and organic- bearing particles around the Paris pollution plume. Positive matrix factorization (PMF) was performed on the ToF-AMS organic mass spectra. Three substantial organic components were resolved. Two of the components contain substantial organic oxygen and are associated with semi-volatile oxygenated organic aerosol particles (SV-OOA) and low-volatility OOA (LV-OOA). Primary hydrocarbon-like organic aerosol particles (HOA) are also resolved. The LV-OOA component is highly aged and is normally detected outside of the main pollution plume, however SV-OOA and HOA have higher mass concentrations in the pollution plume rather than outside. We observe that mass concentrations of SV-OOA increase with both photochemical age and distance from the center of Paris within the pollution plume showing that there is significant formation of secondary organic aerosols within the plume. Similarly, combining these measurements with gas-phase measurements of NOx and volatile organic carbon (VOC) allows us to associate anthropogenic precursor VOCs to the formation of secondary organic aerosols.

Freney, E. J.; Sellegri, K.; Crumeyrolle, S.; Barbet, C.; Pichon, J.; Borbon, A.; Colomb, A.; Schwarzenboeck, A.

2011-12-01

272

Ice Formation Potential of Field-Collected Marine Biogenic Particles  

NASA Astrophysics Data System (ADS)

Marine biogenic particles composed mainly of sea salt and organic material aerosolized from a mesocosm in laboratory experiments have recently been found to act as ice nuclei. How these particles relate to those collected from sea spray under ambient conditions in the field is unknown. This study reports on the heterogeneous ice nucleation potential of particles collected during the marine aerosol characterization experiment (MACE) on the south shore of Long Island, New York. Ambient aerosol size distributions were measured and particles were collected on hydrophobically coated substrates and subsequently used for ice nucleation experiments using an ice nucleation cell coupled to an optical microscope. This technique allows detection of ice formation for temperatures between 200 and 273 K and for relative humidity with respect to ice (RHice) from 100% up to water saturation. Individual ice nucleating particles were identified for subsequent chemical and physical characterization using both X-ray and electron micro-spectroscopic techniques. Concentrations of bacteria, viruses, and transparent exopolymer particles (TEP) in the bulk seawater, sea-surface microlayer (SML), and in sea spray were determined using established methods and related to airborne sea spray particles and their ice nucleation potential. Onshore aerosol size distribution measurements taken at 5 m height and 10 m away from the breaking waves, revealed a peak maximum at 100 nm and Ntot = 6.8 x 10^2 cm^-3. Bacterial, viral, and TEP were found to be enriched in the SML. Ambient particles collected during MACE were found to nucleate ice efficiently, e. g. at 215 K, ice nucleation occurred on average at 125% RHice. Results of aerosol size distributions and ice nucleation efficiencies are compared to laboratory bubble bursting experiments in which natural seawater was used. The goal of this study is to understand the connection between sea spray aerosolization and atmospheric ice cloud formation and to provide physically and chemically based descriptions of ice nucleation for implementation in aerosol-cloud interaction models.

Carrion-Matta, A.; Alpert, P. A.; Radway, J.; Kilthau, W.; Bothe, D.; Knopf, D. A.; Aller, J. Y.

2013-12-01

273

Reactions and mass spectra of complex particles using Aerosol CIMS  

NASA Astrophysics Data System (ADS)

Aerosol chemical ionization mass spectrometry (CIMS) is used both on- and off-line for the analysis of complex laboratory-generated and ambient particles. One of the primary advantages of Aerosol CIMS is the low degree of ion fragmentation, making this technique well suited for investigating the reactivity of complex particles. To demonstrate the usefulness of this "soft" ionization, particles generated from meat cooking were reacted with ozone and the composition was monitored as a function of reaction time. Two distinct kinetic regimes were observed with most of the oleic acid in these particles reacting quickly but with 30% appearing to be trapped in the complex mixture. Additionally, detection limits are measured to be sufficiently low (100-200 ng/m3) to detect some of the more abundant constituents in ambient particles, including sulfate, which is measured in real-time at 1.2 [mu]g/m3. To better characterize complex aerosols from a variety of sources, a novel off-line collection method was also developed in which non-volatile and semi-volatile organics are desorbed from particles and concentrated in a cold U-tube. Desorption from the U-tube followed by analysis with Aerosol CIMS revealed significant amounts of nicotine in cigarette smoke and levoglucosan in oak and pine smoke, suggesting that this may be a useful technique for monitoring particle tracer species. Additionally, secondary organic aerosol formed from the reaction of ozone with R-limonene and volatile organics from orange peel were analyzed off-line showing large molecular weight products (m/z > 300 amu) that may indicate the formation of oligomers. Finally, mass spectra of ambient aerosol collected offline reveal a complex mixture of what appears to be highly processed organics, some of which may contain nitrogen.

Hearn, John D.; Smith, Geoffrey D.

2006-12-01

274

The Role of Aerosol Composition in Arctic Cloud Formation  

NASA Astrophysics Data System (ADS)

While it has been shown that aerosol size has a direct correlation with its ability to act as an ice nucleus, the role of the composition of freshly emitted and evolving aerosol in nucleation is poorly understood. Here we use combined measurements of ice nucleation and high resolution single particle composition to provide insight on the connection between aerosol composition in ice nucleation. These measurements were collected during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, AK in the springtime of 2008. In-situ ice nucleation measurements were conducted using the Texas Continuous Flow Diffusion Chamber (CFDC). The composition of ambient particles as well as residuals of cloud droplets and ice crystals were studied on a particle by particle basis using computer controlled scanning electron microscopy with energy dispersive X-ray analysis (CCSEM/EDX) and scanning transmission X-Ray microscopy coupled with near edge X-ray absorption spectroscopy (STXM/NEXAFAS). Observed IN concentrations varied from frequent values of 0.01 per liter to more than 10 per liters, depending on conditions and the availability of ice-nucleating aerosols. Ice crystals residuals collected in a fully glaciated cloud demonstrate that both particle chemistry and size requirement must be met for a particle to be an efficient ice nucleus. According to the STXM/NEXAFAS spectral maps, ice crystals residuals are characterized by insoluble cores of either large brown or black carbon (BBC) or carbonates coated by water soluble organics. In contrast, in ambient air samples collected from a biomass burning plume, many organic particles were also observed, but these were smaller and did not have insoluble cores. In-situ ice nucleation measurements show that these biomass particles have inferior ice nuclei ability, relative to those collected in the glaciated cloud. Taken together our measurements suggest that two key elements, a critical size (provided by BBC and/or carbonate) and chemical (organic) component are required for an aerosol to be an effective ice nucleus.

Brooks, S. D.; Hiranuma, N.; Moffet, R.; Laskin, A.; Gilles, M. K.; Glen, A.

2010-12-01

275

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

Microsoft Academic Search

We use an inorganic aerosol thermodynamic equilibrium model in a three-dimensional chemical transport model to understand the roles of ammonia chemistry and natural aerosols on the global distribution of aerosols. The thermodynamic equilibrium model partitions gas-phase precursors among modeled aerosol species self-consistently with ambient relative humidity and natural and anthropogenic aerosol emissions during the 1990s.Model simulations show that accounting for

Chao Luo; Charles S. Zendera; Huisheng Bian; Swen Metzger

2007-01-01

276

Water-soluble dicarboxylic acids and ketocarboxylic acids in the aerosols collected during ACE-Asia/C-130 aircraft campaign 2001  

NASA Astrophysics Data System (ADS)

During the ACE-Asia campaign with C-130 aircraft, aerosol samples were collected over the western North Pacific, East China Sea, and Japan Sea, as well as over Japanese Islands and Korean Peninsula in 8 April to 3 May 2001. The filter samples (N=15) were extracted with organic-free pure water to separate water-soluble dicarboxylic acids and related compounds. The extracts were reacted with 14% BF3 in n-butanol and the dibutyl esters and other derivatives were determined using a capillary GC and GC/MS. The results showed that 14 species of diacids (C2-C11) and 4 species of ketoacids (C2-C4) were detected in the aerosols over the East Asia. Total concentrations of the diacids were 113-500 (av. 330) ng/m3 whereas those of ketoacids were 43-260 (av. 103) ng/m3. The concentrations are equivalent to or more abundant than those reported for the urban Tokyo atmosphere in this season on the ground level. All the samples showed that oxalic acid (C2) is the most abundant diacid, which accounted for 58-83% of total diacids. These values are greater than that (ca. 50%) reported in the urban air near the ground, suggesting that oxalic acid is preferentially produced and/or longer diacids are selectively decomposed in the upper troposphere. Malonic (C3) acid is the second most abundant species followed by succinic (C4) acid. Longer diacids are less abundant, but azelaic (C9) acid is generally more abundant than C6-C8 diacids. Glyoxylic acid (C2) is the most abundant ketoacid followed by pyruvic acid. However, C3 and C4 omega-oxoacids were found as minor species. Although oxalic acid is the dominant component in the aerosols, few samples showed the predominance of glyoxylic acid over oxalic acid. This feature has not been reported for the urban aerosols collected near the ground level. We will discuss a potential photochemical production of water-soluble organic acids in the upper troposphere over the eastern ridge of the Asian continent.

Kawamura, K.; Mochida, M.; Uemoto, N.; Bertram, T.; Huebert, B.

2001-12-01

277

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

278

Tracing Ambient Air Geochemistry using a Modified X-Ray Fluorescence Filter Method  

NASA Astrophysics Data System (ADS)

Modifications of x-ray fluorescence counting procedures enable tracing of aerosol dispersals related to weather fronts and local weather phenomena. Improved X-ray fluorescence methods for bulk aerosols deposited under positive air pressure conditions onto Millipore filters at 80 liters/hour enable the tracing of geological samples in periods down to one hour. Vacuum-plating aliquots of USGS standards onto 0.2 micron polycarbonate and quartz Millipore filters create standards with a shelf life of several months. The analytical system permits detection of light oxides, such as silica to 10 ppm, and heavy elements, such as iron to 0.5 ppm. These collections allow discriminations to be drawn between dominantly geological, silica-enriched air mass and dominantly iron-enriched air of possible industrial origin. These ambient air collections at 120 feet elevation at City College are used to create possible distinctions in air masses related to points of origin. Splits of aerosol examined by neutron activation and coupled plasma emission spectroscopy agree with x-ray fluorescence methods to within analytical error. Aerosol flux conditions are monitored for speciation using direct examination by scanning electron microscopy with energy dispersive analytical capability plus aerosol physical properties by sun photometry. The latter provides bulk optical transmission at six major wavelengths and estimates for bulk aerosol size properties. Preliminary data show positive photometry links with iron-aerosols with a correlation coefficient with southwesterly wind-driven conditions of seventy percent over a four hour monitoring period. Aerosol flux comparisons with heavy metal populations, Ba, Rb, Zr, La show uniform distributions with iron- and silica-enriched populations indicating a pervasive background condition in the ambient air mass over New York City.

Steiner, J. C.; Rudolph, E.; Wrice, T.

2002-12-01

279

X-ray diffraction analysis of PM-10 aerosols extracted by ultrasound  

SciTech Connect

Determination of the species of compounds present in ambient aerosols has received increasing interest in recent years, but the U.S. Environmental Protection Agency`s conversion to the PM{sub 10} standard in 1987 has made quantitative analysis of fine particle aerosols more difficult because of the much smaller deposited mass on these filters, as well as the increased proportion of carbon-bearing material naturally present in the smaller diameter portion of the atmospheric aerosol size distribution. Under the old TSP (Total Suspended Particulate) collection protocol, filter loads of 400-2000 {mu}g cm{sup -2} of 10-20 {mu}m mean diameter particles, corresponding to 24-hour collections at ambient concentrations of 100 to 500 {mu}g m{sup -3} at 40 CFM flow rates, resulted in excellent diffraction patterns scanned directly from filter segments. Our sulfate study and quartz study illustrate typical results using these filters. At the other extreme only marginal information on the major components of ambient aerosols could be obtained from dichotomous filters with an upper cutpoint of 15 {mu}m and coarse/fine split at 2.5 {mu}m in the Houston aerosol study. 10 refs., 12 figs., 4 figs., 1 tab.

Davis, B.L.; Hong Chen [South Dakota School of Mines and Technology, Rapid City, SD (United States)

1995-12-31

280

Coarse-fine and day-night differences of water-soluble ions in atmospheric aerosols collected in Christchurch and Auckland, New Zealand  

NASA Astrophysics Data System (ADS)

The water-soluble ions in fine (PM <2.5) and coarse (PM 2.5-10) atmospheric aerosols collected in Christchurch during winter 2001, spring 2000 and summer 2001, and in Auckland during winter 2001 have been studied in terms of coarse-fine and day-night differences. Although the chemical characteristics of the coarse particles were similar in both cities, those of the fine particles collected in the Christchurch winter were significantly different, as manifested by higher concentrations of nss-K +, nss-Cl -, nss-Ca 2+, nss-SO 42-, NO 3- and NH 4+. It was found that nighttime PM 10 and nss-K + concentrations were much higher than their daytime concentrations in the Christchurch winter but a clear day-night difference was not apparent in the Auckland winter. Moreover, in the winter, sea-salt ions did not show a day-night difference; however, nss-SO 42- had opposite day-night variation in the two cities. An ion balance calculation has shown that in most samples, coarse particles can be neutral or alkaline, however, fine particles can be neutral or acidic. The possibility of ammonium salts existing in the fine particles collected in the Christchurch winter is discussed and it is concluded that a variety of ammonium salts were present. Equivalent ratios suggest that the fine particles may be significantly aged in the Christchurch winter. The evidence from our soluble ion study strongly suggests that wood and coal burning and secondary aerosols make a significant contribution to fine particulate mass in the Christchurch atmosphere. Thus, home-heating, a sheltered geographic location and relatively calm atmospheric condition are thought to be the major causes for the serious atmospheric particulate pollution in the Christchurch winter.

Wang, Haobo; Shooter, David

281

Laboratory and field measurements of organic aerosols with the photoionization aerosol mass spectrometer  

NASA Astrophysics Data System (ADS)

Analytical methods developed to sample and characterize ambient organic aerosols often face the trade-off between long sampling times and the loss of detailed information regarding specific chemical species present. The soft, universal ionization scheme of the Photoionization Aerosol Mass Spectrometer (PIAMS) allows for identification of various chemical compounds by a signature ion, often the molecular ion. The goal of this thesis work is to apply PIAMS to both laboratory and field experiments to answer questions regarding the formation, composition, and behavior of organic aerosols. To achieve this goal, a variety of hardware and software upgrades were administered to PIAMS to optimize the instrument. Data collection and processing software were either refined or built from the ground up to simplify difficult or monotonous tasks. Additional components were added to PIAMS with the intent to automate the instrument, enhance the results, and make the instrument more rugged and user-friendly. These changes, combined with the application of an external particle concentration system (mini-Versatile Aerosol Concentration Enrichment System, m-VACES), allowed PIAMS to be suitable for field measurements of organic aerosols. Two such field campaigns were completed, both at the State of Delaware Air Quality Monitoring Site in Wilmington, Delaware: a one week period in June, 2006, and an 18 day period in October and November of 2007. A sampling method developed was capable of collecting sufficient ambient organic aerosol and analyzing it with a time resolution of 3.5 minutes. Because of this method, short term concentration changes of individual species can be tracked. Combined with meteorological data, the behavior of these species can be analyzed as a function of time or wind direction. Many compounds are found at enhanced levels during the evening/night-time hours; potentially due to the combined effects of temperature inversion, and fresh emissions in a cooler environment. The high-time resolution data shows that rapid concentration changes of a common individual species can be lost with traditional bulk sampling, and a time resolution of 30 minutes is suggested to accurately represent these changes. Using the mass spectra collected from the extended sampling campaign, source apportionment was performed with positive matrix factorization (PMF). The resulting model features six factors either correlated to specific sources (meat cooking, car emissions/road dust, diesel exhaust) or types of compounds (phthalates, alkanes/alkanoic acids, PAHs). The high-time resolution data allowed for the observation of specific trends in each factor's behavior as a function of time and wind direction relative to the receptor site. Elemental carbon/organic carbon (EC/OC) data is used to calculate the percentages of primary and secondary organic aerosol. Primary organic aerosol (POA) constituted the vast majority of the total carbon at 91% (an average of 2.8 +/- 1.1mug/m 3); 30% of which came from combustion, and 70% from non-combustion sources. These results can be explained by the PIAMS data: the diesel factor contributes to the combustion-related POA; the car/road dust, meat cooking, and alkane/alkanoic acid factors contribute the majority of non-combustion POA. The remaining factors represent <5% of the remaining OC. Considering the compatibility of data from the EC/OC and PIAMS, the ability of PIAMS to yield molecular species information to further define the primary and secondary organic aerosol factions is a distinct advantage in describing the behavior of the Wilmington organic aerosol. PIAMS was also applied to laboratory experiments. These experiments simulated complex environmental processes in order to focus on answering a central question. By mixing cholesterol aerosol with ozone in a smog chamber, and monitoring the concentration of cholesterol with PIAMS, the rate of reaction was determined. This rate indicates that cholesterol aerosol, which is a suggested source tracer, will remain in the ambient air for a few days under norma

Dreyfus, Matthew A.

282

Importance of aerosol composition, mixing state, and morphology for heterogeneous ice nucleation: A combined field and laboratory approach  

NASA Astrophysics Data System (ADS)

In this study chemical compositions of background aerosol and ice nuclei were examined through laboratory investigations using Raman spectroscopy and field measurements by single-particle mass spectrometry. Aerosol sampling took place at Storm Peak Laboratory in Steamboat Springs, Colorado (elevation of 3210 m). A cascade impactor was used to collect coarse-mode aerosol particles for laboratory analysis by Raman spectroscopy; the composition, mixing state, and heterogeneous ice nucleation activity of individual particles were examined. For in situ analysis of fine-mode aerosol, ice nucleation on ambient particles was observed using a compact ice nucleation chamber. Ice crystals were separated from unactivated aerosol using a pumped counterflow virtual impactor, and ice nuclei were analyzed using particle analysis by laser mass spectrometry. For both fine and coarse modes, the ice nucleating particle fractions were enriched in minerals and depleted in sulfates and nitrates, compared to the background aerosol sampled. The vast majority of particles in both the ambient and ice active aerosol fractions contained a detectable amount of organic material. Raman spectroscopy showed that organic material is sometimes present in the form of a coating on the surface of inorganic particles. We find that some organic-containing particles serve as efficient ice nuclei while others do not. For coarse-mode aerosol, organic particles were only observed to initiate ice formation when oxygen signatures were also present in their spectra.

Baustian, Kelly J.; Cziczo, Daniel J.; Wise, Matthew E.; Pratt, Kerri A.; Kulkarni, Gourihar; Hallar, A. Gannet; Tolbert, Margaret A.

2012-03-01

283

Influences of traffic volumes and wind speeds on ambient ultrafine particle levels—Observations at a highway electronic toll collection (ETC) lane  

NASA Astrophysics Data System (ADS)

The levels of ultrafine particles (UFPs) and their size distributions on a highway electronic toll collection (ETC) lane were measured from October 30 to November 1 and November 5 to November 6, 2008. The hourly UFP levels measured at the highway ETC lane were 1.3 × 10 4-1.9 × 10 5 particles cm -3 (mean = 9.4 × 10 4 particles cm -3). Compared with urban UFP levels, average UFP levels at the highway ETC lane were about 5-10 times higher than those previously measured in urban areas, indicating that a considerable amount of UFPs were exhausted from vehicles. At the highway ETC lane, the average UFP number size distribution had a dominant mode at about 10 nm and a minor mode at about 33 nm. Measurement results indicate that nucleation mode particles remained at relatively high levels compared to Aitken mode and accumulation mode particles at the highway ETC lane. This study identifies the impacts of traffic volumes and wind speeds on ambient UFP levels. Measurement results show that the elevated UFP levels resulting from traffic volume decreased exponentially as wind speed increased on the highway when wind speed was <2.0 m s -1. However, the elevated UFP levels resulting from traffic volume increased slightly when wind speed was >2.0 m s -1 due to local turbulent mixing causes UFPs at high wind speeds. According to measurement results, high levels of UFP were observed at low wind speeds and under high traffic volumes.

Cheng, Yu-Hsiang; Li, Yi-Sheng

2011-01-01

284

Selenium Aerosol  

Microsoft Academic Search

To determine the atmospheric concentrations and size distributions of particulate selenium (Se), aerosols were collected by air filtration and impactor sampling at the Kap Arkona coastal weather station on the Island of Rugen.Total reflection X-ray fluorescence analysis was used to determine Se and numerous other elements as well.The dependence of the Se concentration on the wind direction and the results

Baltic Sea

285

Optimisation of analytical procedures for the quantification of ionic and carbonaceous fractions in the atmospheric aerosol and applications to ambient samples.  

PubMed

In the last decade, our research group set up and optimised analytical techniques for the characterisation of the major components of atmospheric aerosol (i.e. secondary inorganic ions and carbonaceous material) and source markers (e.g. levoglucosan, carbonates). In this study, we present a complete overview on the most problematic aspects that can be encountered during the quantification of the two main components of aerosol, i.e. the ionic and carbonaceous fractions. More in detail, different liquid chromatographic approaches were set up for main ions and anhydrosugars determination. Quality assurance procedures (i.e. tests on data reliability) were applied during the set-up phase and they are presented in this work. As regards the carbonaceous component characterisation, two evolved gas analysis techniques were set up and applied: the thermogravimetric technique coupled to the Fourier transformed infrared spectroscopy (TGA/FTIR) and the thermal-optical transmittance method (TOT). A suitable protocol for organic and elemental carbon separation was set up for the TGA/FTIR system and a comparison with the results obtained by the TOT method was carried out. Studies on the impact of filter load, field blanks, and sample composition on OC/EC quantification by the TOT method were performed. Moreover, approaches for carbonate carbon quantification on different kinds of filters were developed. It was demonstrated that this approach allows to reach the ionic balance in samples impacted by carbonate compounds. The optimised methods have been applied for the analysis of thousands of PM filters allowing the obtainment of reliable results. PMID:23052877

Piazzalunga, Andrea; Bernardoni, Vera; Fermo, Paola; Vecchi, Roberta

2013-01-01

286

Influence of Aerosol Acidity on the Chemical Composition of Secondary Organic Aerosol from ?-caryophyllene  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) yield of ?-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of ?-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI- TOFMS). A number of first- , second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increased acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three ?-caryophyllene products (i.e., ?-nocaryophyllon aldehyde, ?-hydroxynocaryophyllon aldehyde, and ?-dihydroxynocaryophyllon aldehyde) are suggested as chemical tracers for ?-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS).

Chan, M.; Surratt, J. D.; Chan, A. W.; Schlling, K.; Offenberg, J. H.; Lewandowski, M.; Edney, E.; Kleindienst, T. E.; Jaoui, M.; Edgerton, E. S.; Tanner, R. L.; Shaw, S. L.; Zheng, M.; Knipping, E. M.; Seinfeld, J.

2011-12-01

287

Influence of aerosol acidity on the chemical composition of secondary organic aerosol from ?-caryophyllene  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) yield of ?-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of ?-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). A number of first-, second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increased acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. To our knowledge, this is the first detection of organosulfates and nitrated organosulfates derived from a sesquiterpene. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three ?-caryophyllene products (i.e., ?-nocaryophyllon aldehyde, ?-hydroxynocaryophyllon aldehyde, and ?-dihydroxynocaryophyllon aldehyde) are suggested as chemical tracers for ?-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS).

Chan, M. N.; Surratt, J. D.; Chan, A. W. H.; Schilling, K.; Offenberg, J. H.; Lewandowski, M.; Edney, E. O.; Kleindienst, T. E.; Jaoui, M.; Edgerton, E. S.; Tanner, R. L.; Shaw, S. L.; Zheng, M.; Knipping, E. M.; Seinfeld, J. H.

2011-02-01

288

Influence of aerosol acidity on the chemical composition of Secondary Organic Aerosol from ?-caryophyllene  

NASA Astrophysics Data System (ADS)

The secondary organic aerosol (SOA) yield of ?-caryophyllene photooxidation is enhanced by aerosol acidity. In the present study, the influence of aerosol acidity on the chemical composition of ?-caryophyllene SOA is investigated using ultra performance liquid chromatography/electrospray ionization-time-of-flight mass spectrometry (UPLC/ESI-TOFMS). A number of first-, second- and higher-generation gas-phase products having carbonyl and carboxylic acid functional groups are detected in the particle phase. Particle-phase reaction products formed via hydration and organosulfate formation processes are also detected. Increase of acidity leads to different effects on the abundance of individual products; significantly, abundances of organosulfates are correlated with aerosol acidity. To our knowledge, this is the first detection of organosulfates and nitrated organosulfates derived from a sesquiterpene. The increase of certain particle-phase reaction products with increased acidity provides chemical evidence to support the acid-enhanced SOA yields. Based on the agreement between the chromatographic retention times and accurate mass measurements of chamber and field samples, three ?-caryophyllene products (i.e., ?-nocaryophyllon aldehyde, ?-hydroxynocaryophyllon aldehyde, and ?-dihydroxynocaryophyllon aldehyde) are identified as chemical tracers for ?-caryophyllene SOA. These compounds are detected in both day and night ambient samples collected in downtown Atlanta, GA and rural Yorkville, GA during the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS).

Chan, M. N.; Surratt, J. D.; Chan, A. W. H.; Schilling, K.; Offenberg, J. H.; Lewandowski, M.; Edney, E. O.; Kleindienst, T. E.; Jaoui, M.; Edgerton, E. S.; Tanner, R. L.; Shaw, S. L.; Zheng, M.; Knipping, E. M.; Seinfeld, J. H.

2010-11-01

289

Characterization of individual submicrometer aerosol particles collected in Incheon, Korea, by quantitative transmission electron microscopy energy-dispersive X-ray spectrometry  

NASA Astrophysics Data System (ADS)

For the last decade the Monte Carlo calculation method has been proven to be an excellent tool for accurately simulating electron-solid interactions in atmospheric individual particles of micrometer size. Although it was designed for application to scanning electron microscopy, in the present study it is demonstrated that the Monte Carlo calculation can also be applied in a quantitative single particle analysis using transmission electron microscopy (TEM) with an ultrathin window energy-dispersive X-ray (EDX) spectrometer with a high accelerating voltage (200 kV). By utilizing an iterative reverse Monte Carlo simulation combined with successive approximation, atomic elemental concentrations (including low-Z elements) of submicrometer standard particles were determined with high accuracy for electron beam refractory particles such as NaCl, KCl, SiO2, Fe2O3, Na2SO4, K2SO4, CaCO3, and CaSO4. On the basis of quantitative X-ray analysis together with morphological information from TEM images, overall 1638 submicrometer individual particles from 10 sets of aerosol samples collected in Incheon, Korea, were identified. The most frequently encountered particle types are carbonaceous and (NH4)2SO4/NH4HSO4-containing particles, followed by mineral (e.g., aluminosilicate, SiO2, CaCO3), sea salt, K-rich (e.g., K2SO4 and KCl), Fe-rich, fly ash, and transition or heavy-metal-containing (e.g., ZnSO4, ZnCl2, PbSO4) particles. The relative abundances of the submicrometer particle types vary among samples collected in different seasons and also depend on different air mass transport routes. This study demonstrates that the quantitative TEM-EDX individual particle analysis is a useful and reliable technique in characterizing urban submicrometer aerosol particles.

Geng, Hong; Kang, Sujin; Jung, Hae-Jin; ChoëL, Marie; Kim, Hyekyeong; Ro, Chul-Un

2010-08-01

290

The effect of nonideal cascade impactor stage collection efficiency curves on the interpretation of the size of inhaler-generated aerosols.  

PubMed

Cascade impactors, operating on the principle of inertial size separation in (ideally) laminar flow, are used to determine aerodynamic particle size distributions (APSDs) of orally inhaled product (OIP) aerosols because aerodynamic diameter can be related to respiratory tract deposition. Each stage is assumed typically to be an ideal size fractionator. Thus, all particles larger than a certain size are considered collected and all finer particles are treated as penetrating to the next stage (a step function stage efficiency curve). In reality, the collection efficiency of a stage smoothly increases with particle size as an "S-shaped" curve, from approximately 0% to 100%. Consequently, in some cases substantial overlap occurs between neighboring stages. The potential for bias associated with the step-function assumption has been explored, taking full resolution and two-stage abbreviated forms of the Andersen eight-stage nonviable impactor (ACI) and the next-generation pharmaceutical impactor (NGI) as example apparatuses. The behavior of unimodal, log-normal APSDs typical of OIP-generated aerosols has been investigated, comparing known input values to calculated values of central tendency (mass median aerodynamic diameter) and spread (geometric standard deviation, GSD). These calculations show that the error introduced by the step change assumption is larger for the ACI than for the NGI. However, the error is sufficiently small to be inconsequential unless the APSD in nearly monodisperse (GSD ?1.2), a condition that is unlikely to occur with realistic OIPs. Account may need to be taken of this source of bias only for the most accurate work with abbreviated ACI systems. PMID:23508617

Roberts, D L; Mitchell, J P

2013-06-01

291

Aerosol variability in the vertical in the southwest pacific  

SciTech Connect

This paper presents information on vertical aerosol distribution measurements made in the southwest Pacific region. Data were collected for particles over the range 0.12 to 8 [mu]m in diameter. Particles in the range 0.1 to 1 [mu]m play a major role in the energy budget on the earth and its climate, because of the long lives they have, and because of scattering and absorbtion of incoming and reflected shortwave radiation, and the formation of clouds. Larger aerosols impact climate by scattering outgoing longwave radiation. The authors present new data on aerosol vertical distributions from airborne measurements, and look at questions of the impact of latitude, ambient temperature, and relative humidity on these distributions.

Kristament, I.S.; Harvey, M.J.; Liley, J.B. (New Zealand Meteorological Service, Wellington (New Zealand))

1993-04-20

292

Review of Trace-Element Field-Blank Data Collected for the California Groundwater Ambient Monitoring and Assessment (GAMA) Program, May 2004-January 2008  

USGS Publications Warehouse

Trace-element quality-control samples (for example, source-solution blanks, field blanks, and field replicates) were collected as part of a statewide investigation of groundwater quality in California, known as the Priority Basins Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basins Project is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB) to assess and monitor the quality of groundwater resources used for drinking-water supply and to improve public knowledge of groundwater quality in California. Trace-element field blanks were collected to evaluate potential bias in the corresponding environmental data. Bias in the environmental data could result from contamination in the field during sample collection, from the groundwater coming into contact with contaminants on equipment surfaces or from other sources, or from processing, shipping, or analyzing the samples. Bias affects the interpretation of environmental data, particularly if any constituents are present solely as a result of extrinsic contamination that would have otherwise been absent from the groundwater that was sampled. Field blanks were collected, analyzed, and reviewed to identify and quantify extrinsic contamination bias. Data derived from source-solution blanks and laboratory quality-control samples also were considered in evaluating potential contamination bias. Eighty-six field-blank samples collected from May 2004 to January 2008 were analyzed for the concentrations of 25 trace elements. Results from these field blanks were used to interpret the data for the 816 samples of untreated groundwater collected over the same period. Constituents analyzed were aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), tungsten (W), uranium (U), vanadium (V), and zinc (Zn). The detection frequency and the 90th percentile concentration at greater than 90 percent confidence were determined from the field-blank data for each trace element, and these results were compared to each constituent's long-term method detection level (LT-MDL) to determine whether a study reporting level (SRL) was necessary to ensure that no more than 10 percent of the detections in groundwater samples could be attributed solely to contamination bias. Only two of the trace elements analyzed, Li and Se, had zero detections in the 86 field blanks. Ten other trace elements (Sb, As, Be, B, Cd, Co, Mo, Ag, Tl, and U) were detected in fewer than 5 percent of the field blanks. The field-blank results for these constituents did not necessitate establishing SRLs. Of the 13 constituents that were detected in more than 5 percent of the field blanks, six (Al, Ba, Cr, Mn, Hg, and V) had field-blank results that indicated a need for SRLs that were at or below the highest laboratory reporting levels (LRL) used during the sampling period; these SRLs were needed for concentrations between the LT-MDLs and LRLs. The other seven constituents with detection frequencies above 5 percent (Cu, Fe, Pb, Ni, Sr, W, and Zn) had field-blank results that necessitated SRLs greater than the highest LRLs used during the study period. SRLs for these seven constituents, each set at the 90th percentile of their concentrations in the field blanks, were at least an order of magnitude below the regulatory thresholds established for drinking water for health or aesthetic purposes; therefore, reporting values below the SRLs as less than or equal to (=) the measured value would not prevent the identification of values greater than the drinking-water thresholds. The SRLs and drinking-water thresholds, respectively, for these 7 trace elements are Cu (1.7 ?g/L and 1,300

Olsen, Lisa D.; Fram, Miranda S.; Belitz, Kenneth

2010-01-01

293

Efflorescence upon humidification? X-ray microspectroscopic in situ observation of changes in aerosol microstructure and phase state upon hydration  

NASA Astrophysics Data System (ADS)

phase and mixing state of atmospheric aerosols is a central determinant of their properties and thus their role in atmospheric cycling and climate. Particularly, the hygroscopic response of aerosol particles to relative humidity (RH) variation is a key aspect of their atmospheric life cycle and impacts. Here we applied X-ray microspectroscopy under variable RH conditions to internally mixed aerosol particles from the Amazonian rain forest collected during periods with anthropogenic pollution. Upon hydration, we observed substantial and reproducible changes in particle microstructure, which appear as mainly driven by efflorescence and recrystallization of sulfate salts. Multiple solid and liquid phases were found to coexist, especially in intermediate humidity regimes. We show that X-ray microspectroscopy under variable RH is a valuable technique to analyze the hygroscopic response of individual ambient aerosol particles. Our initial results underline that RH changes can trigger strong particle restructuring, in agreement with previous studies on artificial aerosols.

Pöhlker, Christopher; Saturno, Jorge; Krüger, Mira L.; Förster, Jan-David; Weigand, Markus; Wiedemann, Kenia T.; Bechtel, Michael; Artaxo, Paulo; Andreae, Meinrat O.

2014-05-01

294

Using Satellite Aerosol Retrievals to Monitor Surface Particulate Air Quality  

NASA Technical Reports Server (NTRS)

The MODIS and MISR aerosol products were designed nearly two decades ago for the purpose of climate applications. Since launch of Terra in 1999, these two sensors have provided global, quantitative information about column-integrated aerosol properties, including aerosol optical depth (AOD) and relative aerosol type parameters (such as Angstrom exponent). Although primarily designed for climate, the air quality (AQ) community quickly recognized that passive satellite products could be used for particulate air quality monitoring and forecasting. However, AOD and particulate matter (PM) concentrations have different units, and represent aerosol conditions in different layers of the atmosphere. Also, due to low visible contrast over brighter surface conditions, satellite-derived aerosol retrievals tend to have larger uncertainty in urban or populated regions. Nonetheless, the AQ community has made significant progress in relating column-integrated AOD at ambient relative humidity (RH) to surface PM concentrations at dried RH. Knowledge of aerosol optical and microphysical properties, ambient meteorological conditions, and especially vertical profile, are critical for physically relating AOD and PM. To make urban-scale maps of PM, we also must account for spatial variability. Since surface PM may vary on a finer spatial scale than the resolution of standard MODIS (10 km) and MISR (17km) products, we test higher-resolution versions of MODIS (3km) and MISR (1km research mode) retrievals. The recent (July 2011) DISCOVER-AQ campaign in the mid-Atlantic offers a comprehensive network of sun photometers (DRAGON) and other data that we use for validating the higher resolution satellite data. In the future, we expect that the wealth of aircraft and ground-based measurements, collected during DISCOVER-AQ, will help us quantitatively link remote sensed and ground-based measurements in the urban region.

Levy, Robert C.; Remer, Lorraine A.; Kahn, Ralph A.; Chu, D. Allen; Mattoo, Shana; Holben, Brent N.; Schafer, Joel S.

2011-01-01

295

Aerosol light scattering properties at Cape Grim, Tasmania, during the First Aerosol Characterization Experiment (ACE 1)  

Microsoft Academic Search

Large uncertainties remain in understanding the effects of ambient aerosols on climate. As part of the First Aerosol Characterization Experiment (ACE 1, November 15 to December 15, 1995), the total light scattering and backscattering coefficients by particles (cysp and CYbsp) were measured at Cape Grim, Tasmania. Such measurements were made to characterize aerosol radiative forcing relevant to climate change at

Christian M. Carrico; Mark J. Rood; John A. Ogren

1998-01-01

296

Development of a capillary electrophoretic method for the analysis of low-molecular-weight amines from metal working fluid aerosols and ambient air.  

PubMed

A method for the determination of low-molecular-weight amines from indoor and ambient air was developed using a concentration device followed by CE coupled with indirect spectrophotometric and mass spectrometric detection that enables a reliable, rapid-response and easy-to-operate method. In indirect detection method, the selected amines were separated from interfering metal ions and amino alcohols present in the samples with an imidazole-based buffer with ethanol and EDTA as modifier. By replacing imidazole with ammonium, the final buffer was applicable for MS detection for the analytes with m/z higher than 50. A novel monolithic polymer material based on poly(methacrylate-acrylate) copolymer was developed for sampling short-chain amines from the gaseous phase. The selected analysis conditions were applied to quantify the selected short-chain amines with detection limits for the whole procedure determined between 1 and 2 microg/filter when 40 L air was sampled with 1 L/min velocity. Improved linearity and precision were obtained when the raw, time-scaled electropherogram data were transformed into mobility-scale applied for the determination of the performance characteristics of the methods. The applicability of the process of data transformation into the mobility scale was demonstrated by studying the matrix effect of water-miscible metal working fluid (stable water-oil emulsion) and of ambient air as real samples. CE-indirect UV and CE-MS, combined with the possibility of rapid air sampling, can be useful for the estimation of short-term exposure of the selected biogenic amines. PMID:16523461

Fekete, Agnes; Frommberger, Moritz; Ping, Guichen; Lahaniatis, Majlinda R; Lintelman, Jutta; Fekete, Jeno; Gebefugi, Istvan; Malik, Ashok Kumar; Kettrup, Antonius; Schmitt-Kopplin, Philippe

2006-03-01

297

Thermal relaxation and collective dynamics of interacting aerosol-generated hexagonal NiFe2O4 nanoparticles.  

PubMed

This article reports on the magnetic properties of interacting uncoated nickel ferrite (NiFe2O4) nanoparticles synthesized through an aerosol levitation-jet technique. A comprehensive set of samples with different compositions of background gas and metal precursors, as well as applied electric field intensities, has been studied. Nanoparticles prepared under a field of 210 kV m(-1) show moderately high-field irreversibility and shifted hysteresis loops after field-cooling, also exhibiting a joint temperature decrease of the exchange field and coercivity. The appearance of memory effects has been checked using the genuine ZFC protocol and the observed behavior cannot be fully explained in terms of thermal relaxation. Although dipolar interactions prevail, exchange interactions occur to a certain extent within a narrow range of applied fields. The origin of the slow dynamics in the system is found to be given by the interplay of the distribution of energy barriers due to size dispersion and the cooperative dynamics associated with frustrated interactions. PMID:24196451

Ortega, D; Kuznetsov, M V; Morozov, Yu G; Belousova, O V; Parkin, I P

2013-12-28

298

Characterization of nitrocatechols and related tracers in atmospheric biomass burning organic aerosol  

NASA Astrophysics Data System (ADS)

One of the largest primary sources of organic aerosols in the atmosphere is biomass burning (Laskin et al., 2009). The chemistry of compounds present in biomass burning aerosol (BBA) is diverse and directly dependent on the chemical composition of the burning material and the combustion conditions (Simoneit et al., 2002). A well-established tracer for primary BBA is levoglucosan (1,6-anhydro-?-anhydroglucose), which originates from the pyrolysis of cellulose or hemicellulose (Fine et al., 2002). Secondary BBA, which is formed after physical and chemical changes (aging) of the primary BBA in the atmosphere, contains more oxidized and polar compounds. An important class of compounds of secondary organic aerosols (SOA) is nitrocatechols, which are strong absorbers of UV and Vis light, and therefore, can affect the earth's radiative balance and climate. Recently, methyl nitrocatechols were proposed as suitable tracers for highly oxidized secondary BBA (Iinuma et al., 2010). These compounds are primarily formed from the photooxidation of m-cresol, that is emitted from biomass burning, in the presence of NOx. The objective of the present study was to characterize nitrocatechols in ambient aerosols using mass spectrometric and chromatographic techniques. Ambient aerosol samples were collected during a cold winter episode from an urban site in Maribor, Slovenia, where substantial residential wood burning for domestic purposes takes place. Emphasis was put on the development of a suitable LC-ESI-MS technique. In an initial step the chromatographic conditions were optimized for methyl nitrocatechols and related nitro-aromatic compounds using diode array UV/Vis detection. The optimized LC conditions were used for the development and validation of an LC-ESI-MS/MS method for identification and quantification of nitrocatechols in aerosol samples. LC/ESI-MS/MS data will be presented and interpreted for the nitro-aromatic compounds that are present in the collected ambient aerosols.

Grgic, I.; Kitanovski, Z.; Yasmeen, F.; Claeys, M.

2011-12-01

299

Ambient Observations of the Soot Aging Process during the SHARP Intensive Field Campaign  

NASA Astrophysics Data System (ADS)

Soot aerosols affect climate both directly through absorption of solar radiation and indirectly by potentially serving as cloud condensation nuclei. Among the sources of uncertainty surrounding the effects of soot aerosol on the environment is the lack of scientific insight into the soot aging process, in which soot particles develop a coating of secondary species such as sulfates, ammonium, nitrate, and organics. Such processes may alter the behavior of soot by modifying particle morphology over time leading to changes in chemical, physical and scattering properties of the aerosol. However, it is often difficult to quantify such processes in the ambient environment due to the complex composition and spatial and temporal variability of the atmospheric aerosol. In order to better understand the effects of the environment on soot particles, it is desirable to study the processes responsible for their transformation in the ambient air without influence from variability in source region and history prior to sampling. To achieve this, the overall soot aging process in the ambient environment was physically isolated utilizing environmental chambers. Chamber measurements were conducted on the Moody Tower at the University of Houston using The Ambient Aerosol Chamber for Evolution Studies (AACES) during the SHARP campaign. AACES is a roughly cubical chamber constructed of a rigid acrylic outer shell, which transmits UV radiation both in the UV-B and UV-A ranges. FEP Teflon lines the inside of the chamber on all sides and the top, while expanded-PTFE (ePTFE) Teflon is used on the bottom of the chamber. The fibrous structure of the ePTFE acts as a barrier to particulates, while allowing gas molecules to move virtually unimpeded from the surrounding air into the chamber, creating an environment inside the chamber that is initially free of particles and continuously mimics the local ambient air. In order to study the effects of the soot aging process, a non-premixed propane flame was used to generate a polydisperse fresh soot aerosol. Then, using a differential mobility analyzer, a monodisperse, uncharged soot aerosol was injected into the environmental chamber. Observations of particle concentration, size, hygroscopicity, effective density, and light extinction and scattering properties were carried out over time using a tandem differential mobility analyzer system, an aerosol particle mass analyzer, a nephelometer and a cavity ringdown spectrometer. Results from preliminary analysis of the data collected during the campaign will be presented.

Reed, C.; Collins, D. R.; Khalizov, A. F.; Zheng, J.; Zhang, R.

2009-12-01

300

Hourly Speciated Organic Aerosol Composition in Riverside, CA during SOAR 2005  

NASA Astrophysics Data System (ADS)

Thermal Desorption Aerosol GC/MS-FID (TAG) is a new in-situ instrument to identify and quantify organic aerosol chemical composition with one hour time resolution. Atmospheric particles are collected by means of humidification and inertial impaction. The sample is then thermally desorbed onto a GC column, where it is separated into individual compounds which are identified and quantified using a quadrupole mass spectrometer (MS) and flame ionization detector (FID). With the exception of periodic manually applied calibration standards, TAG is fully automated, offering around the clock measurements to determine diurnal, weekly, and seasonal patterns in organic aerosol composition. The summer and fall of 2005 offered a unique opportunity for TAG to operate in parallel with a large suite of organic aerosol instrumentation, including several Aerodyne AMS instruments, three ATOFMS instruments, several high volume filter samplers, two EC/OC monitors, along with other aerosol and gas phase instrumentation as part of the Study of Organic Aerosol at Riverside (SOAR) campaign at the University of California, Riverside. We will present initial TAG particle source apportionment results, including separation of the influence from particle sources such as biomass combustion, vehicle emissions, pesticides, biogenic aerosol, and oxidation of biogenic and anthropogenic precursor gases leading to secondary organic aerosol (SOA) formation. We will also present ambient air observations of gas-particle partitioning as a function of molecular size and functional groups.

Williams, B. J.; Goldstein, A. H.; Kreisberg, N. M.; Hering, S. V.

2006-12-01

301

Direct gravimetric measurements of the mass of the antarctic aerosol collected by high volume sampler: PM10 summer seasonal variation at Terra Nova Bay.  

PubMed

An on-site procedure was set up for direct gravimetric measurement of the mass of aerosol collected using high volume impactors (aerodynamic size cut point of 10 microm, PM10); this knowledge has hitherto been unavailable. Using a computerized microbalance in a clean chemistry laboratory, under controlled temperature (+/-0.5 degrees C) and relative humidity (+/-1%), continuous, long time filter mass measurements (hours) were carried out before and after exposure, after a 48 h minimun equilibration at the laboratory conditions. The effect of the electrostatic charge was exhausted in 30-60 min, after which stable measurements were obtained. Measurements of filters exposed for 7-11 days (1.13 m3 min(-1)) in a coastal site near Terra Nova Bay (December 2000 - February 2001), gave results for aerosol mass in the order of 10-20 mg (SD approximately 2 mg), corresponding to atmospheric concentrations of 0.52-1.27 microg m(-3). Data show a seasonal behaviour in the PM10 content with an increase during December - early January, followed by a net decrease. The above results compare well with estimates obtained from proxy data for the Antarctic Peninsula (0.30 microg m(-3)), the Ronne Ice Shelf (1.49 microg m(-3)), and the South Pole (0.18 microg m(-3), summer 1974-1975, and 0.37 microg m(-3), average summer seasons 1975-1976 and 1977-1978), and from direct gravimetric measurements recently obtained from medium volume samplers at McMurdo station (downwind 3.39 microg m(-3), upwind 4.15 microg m(-3)) and at King George Island (2.5 microg m(-3), summer, particle diameter <20 microm). This finding opens the way to the direct measurement of the chemical composition of the Antarctic aerosol and, in turn, to a better knowledge of the snow/air relationships as required for the reconstruction of the chemical composition of past atmospheres from deep ice core data. PMID:16398350

Truzzi, Cristina; Lambertucci, Luca; Illuminati, Silvia; Annibaldi, Anna; Scarponi, Giuseppe

2005-01-01

302

Microwave-assisted extraction of rare earth elements from petroleum refining catalysts and ambient fine aerosols prior to inductively coupled plasma-mass spectrometry.  

PubMed

A robust microwave-assisted acid digestion procedure followed by inductively coupled plasma-mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM(2.5)). High temperature (200 degrees C), high pressure (200 psig), acid digestion (HNO(3), HF and H(3)BO(3)) with 20 min dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst and PM(2.5). This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using (115)In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu and Dy in ambient PM(2.5) in an industrial area of Houston, TX. PMID:17386451

Kulkarni, Pranav; Chellam, Shankararaman; Mittlefehldt, David W

2007-01-01

303

Microwave-assisted Extraction of Rare Earth Elements from Petroleum Refining Catalysts and Ambient Fine Aerosols Prior to Inductively Coupled Plasma - Mass Spectrometry  

NASA Technical Reports Server (NTRS)

In the absence of a certified reference material, a robust microwave-assisted acid digestion procedure followed by inductively coupled plasma - mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM2.5). High temperature (200 C), high pressure (200 psig), acid digestion (HNO3, HF, and H3BO3) with 20 minute dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst, and PM2.5. This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb, and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy, and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using 115In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu, and Dy in ambient PM2.5 in an industrial area of Houston, TX.

Mittlefehldt, David W.; Kulkarni, Pranav; Chellam, Shankar

2006-01-01

304

Chemical characterization of individual particles and residuals of cloud droplets and ice crystals collected on board research aircraft in the ISDAC 2008 study  

NASA Astrophysics Data System (ADS)

Ambient particles and the dry residuals of mixed-phase cloud droplets and ice crystals were collected during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) near Barrow, Alaska, in spring of 2008. The collected particles were analyzed using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy to identify physico-chemical properties that differentiate cloud-nucleating particles from the total aerosol population. A wide range of individually mixed components was identified in the ambient particles and residuals including organic carbon compounds, inorganics, carbonates, and black carbon. Our results show that cloud droplet residuals differ from the ambient particles in both size and composition, suggesting that both properties may impact the cloud-nucleating ability of aerosols in mixed-phase clouds. The percentage of residual particles which contained carbonates (47%) was almost four times higher than those in ambient samples. Residual populations were also enhanced in sea salt and black carbon and reduced in organic compounds relative to the ambient particles. Further, our measurements suggest that chemical processing of aerosols may improve their cloud-nucleating ability. Comparison of results for various time periods within ISDAC suggests that the number and composition of cloud-nucleating particles over Alaska can be influenced by episodic events bringing aerosols from both the local vicinity and as far away as Siberia.

Hiranuma, N.; Brooks, S. D.; Moffet, R. C.; Glen, A.; Laskin, A.; Gilles, M. K.; Liu, P.; MacDonald, A. M.; Strapp, J. W.; McFarquhar, G. M.

2013-06-01

305

PHOTOACOUSTIC DETERMINATION OF OPTICAL PROPERTIES OF AEROSOL PARTICLES COLLECTED ON FILTERS: DEVELOPMENT OF A METHOD TAKING INTO ACCOUNT SUBSTRATE REFLECTIVITY  

EPA Science Inventory

The absorptivity and imaginary index of refraction for carbon and methylene blue particles were inferred from the photoacoustic spectra of samples collected on Teflon filter substrates. Three models of varying complexity were developed to describe the photoacoustic signal as a fu...

306

Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry Part II: overview of the results at the CENICA supersite and comparison to previous studies  

NASA Astrophysics Data System (ADS)

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite during the Mexico City Metropolitan Area field study from 31 March-4 May 2003. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. Measurements of Black Carbon (BC) using an aethalometer, and estimated soil concentrations from Proton-Induced X-Ray Emission (PIXE) analysis of impactor substrates are also presented and combined with the AMS in order to include refractory material and estimate the total PM2.5 mass concentration at CENICA during this campaign. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents 54.6% of the mass, with the rest consisting of inorganic compounds (mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5; BC mass concentration is about 11%; while soil represents about 6.9%. The NR species and BC have diurnal cycles that can be qualitatively interpreted as the interplay of direct emissions, photochemical production in the atmosphere followed by condensation and gas-to-particle partitioning, boundary layer dynamics, and/or advection. Bi- and trimodal size distributions are observed for the AMS species, with a small combustion (likely traffic) organic particle mode and an accumulation mode that contains mainly organic and secondary inorganic compounds. The AMS and BC mass concentrations, size distributions, and diurnal cycles are found to be qualitatively similar to those from most previous field measurements in Mexico City.

Salcedo, D.; Dzepina, K.; Onasch, T. B.; Canagaratna, M. R.; Jayne, J. T.; Worsnop, D. R.; Gaffney, J. S.; Marley, N. A.; Johnson, K. S.; Zuberi, B.; Molina, L. T.; Molina, M. J.; Shutthanandan, V.; Xie, Y.; Jimenez, J. L.

2005-06-01

307

Characterization of Ambient Aerosols in Mexico City during the MCMA-2003 Campaign with Aerosol Mass Spectrometry. Part II: Overview of the Results at the CENICA Supersite and Comparison to Previous Studies  

SciTech Connect

An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite during the Mexico City Metropolitan Area field study from March 29-May 4, 2003. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 ?m (NR PM1) with high time and size resolution. Measurements of Black Carbon (BC) using an aethalometer, and estimated soil concentrations from Proton-Induced X-Ray Emission (PIXE) analysis of impactor substrates are also presented and combined with the AMS in order to include refractory material and estimate the total PM??? mass concentration at CENICA during this campaign. In Mexico City, the organic fraction of the estimated PM??? at CENICA represents 55% of the mass, with the rest consisting of inorganic (mainly ammonium nitrate and sulfate/ammonium salts) compounds, BC, and soil. Inorganic compounds represents 27.5% of PM???; BC mass concentration is equivalent to about 11%; while soil represents about 7%. The NR species and BC have diurnal cycles that can be qualitatively interpreted as the interplay of direct emissions, photochemical production in the atmosphere followed by condensation and gas-to-particle partitioning, boundary layer dynamics, and/or advection. Bi and trimodal size distributions are observed, with a small primary organic combustion (likely traffic) particle mode and an accumulation mode that contains mainly organic and secondary inorganic compounds. The AMS and BC mass concentrations, size distributions, and diurnal cycles are found to be qualitatively similar to those from other field measurements in Mexico City.

Salcedo, D.; Dzepina, K.; Onasch, Timothy B.; Canagaratna, M. R.; Jayne, J. T.; Worsnop, Douglas R.; Gaffney, Jeffrey S.; Marley, Nancy A.; Johnson, Kirsten S.; Zuberi, Bilal M.; Molina, Luisa; Molina, Mario J.; Shutthanandan, V.; Xie, YuLong; Jimenez, J. L.

2005-06-28

308

Lignin-derived phenols in Houston aerosols: implications for natural background sources.  

PubMed

Solvent-extractable monomeric methoxyphenols in aerosol samples conventionally have been used to indicate the influence of biomass combustion. In addition, the presence of lignin oxidation products (LOP), derived from the CuO oxidation of vascular plant organic matter, can help trace the source and inputs of primary biological particles in aerosols. Ambient aerosols (coarse and fine) collected in Houston during summer 2010 were analyzed by gas chromatography-mass spectrometry to characterize monomeric and polymeric sources of LOPs. This is the first time polymeric forms of the LOPs have been characterized in ambient aerosols. The absence or small concentrations of solvent-extractable monomeric LOPs and levoglucosan isomers point to the limited influence of biomass burning during the sampling period. The trace levels of anhydrosugar concentrations most likely result from long-range transport. This observation is supported by the absence of co-occurring lignin monomers that undergo photochemical degradation during transport. The larger concentration (142 ng m(-3)) of lignin polymers in coarse aerosols shows the relative importance of primary biological aerosol particles, even in the urban atmosphere. The LOP parameters suggest a predominant influence from woody tissue of angiosperms, with minor influence from soft tissues, gymnosperms, and soil organic matter. PMID:21877739

Shakya, Kabindra M; Louchouarn, Patrick; Griffin, Robert J

2011-10-01

309

Radiative Effects of Aerosols  

NASA Technical Reports Server (NTRS)

During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size-resolved aerosol microphysics and chemistry. Both profiles included a pollution haze from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core. The soot core increased the calculated extinction by about 10% in the most polluted drier layer relative to a pure sulfate aerosol but had significantly less effect at higher humidities. A 3 km descent through a boundary layer air mass dominated by pollutant aerosol with relative humidities (RH) 10-77% yielded a close agreement between the measured and calculated aerosol optical depths (550 nm) of 0.160 (+/- 0.07) and 0. 157 (+/- 0.034) respectively. During descent the aerosol mass scattering coefficient per unit sulfate mass varied from about 5 to 16 m(exp 2)/g and primarily dependent upon ambient RH. However, the total scattering coefficient per total fine mass was far less variable at about 4+/- 0.7 m(exp 2)/g. A subsequent descent through a Saharan dust layer located above the pollution aerosol layer revealed that both layers contributed similarly to aerosol optical depth. The scattering per unit mass of the coarse aged dust was estimated at 1.1 +/- 0.2 m(exp 2)/g. The large difference (50%) in measured and calculated optical depth for the dust layer exceeded measurements.

Valero, Francisco P. J.

1996-01-01

310

Singleparticle characterization of four aerosol samples collected in ChunCheon, Korea, during Asian dust storm events in 2002  

Microsoft Academic Search

A single-particle analytical technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), employing an ultrathin window X-ray detector and enabling the quantitative determination of even low-Z elements such as C, N, and O, was applied to characterize ``Asian dust'' samples, collected in ChunCheon, Korea, during four Asian dust storm events on 21 March, 9 April, 17 April, and

HeeJin Hwang; Chul-Un Ro

2005-01-01

311

Singleparticle characterization of four aerosol samples collected in ChunCheon, Korea, during Asian dust storm events in 2002  

Microsoft Academic Search

A single-particle analytical technique, named low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), employing an ultrathin window X-ray detector and enabling the quantitative determination of even low-Z elements such as C, N, and O, was applied to characterize “Asian dust” samples, collected in ChunCheon, Korea, during four Asian dust storm events on 21 March, 9 April, 17 April, and

HeeJin Hwang; Chul-Un Ro

2005-01-01

312

Measurement of polycyclic aromatic hydrocarbons associated with size-segregated atmospheric aerosols in Massachusetts  

Microsoft Academic Search

Size-segregated atmospheric aerosols were collected from urban and rural locations in Massachusetts using a micro-orifice impactor. The samples were analyzed for polycyclic aromatic hydrocarbons (PAH) with molecular weight between 178 and 302, using gas chromatography\\/mass spectrometry. Fifteen PAH were quantified in the urban samples and nine in the rural samples. The quantification results are in good agreement with available ambient

Jonathan O. Allen; Nameeta M. Dookeran; Kenneth A. Smith; Adel F. Sarofim; Koli Taghizadeh; Arthur L. Lafleur

1996-01-01

313

Identification of source contributions to visibility-reducing organic aerosols in the vicinity of Grand Canyon National Park. Interim final report  

SciTech Connect

Sulfates and carbonaceous aerosols are the largest contributors to the fine particle burden in the atmosphere near Grand Canyon National Park. While the effects of sulfate particles on visibility at the Grand Canyon has been extensively studied, much less is known about the nature and origin of the carbonaceous aerosols that are present. This disparity in understanding arises from at least two causes: aerosol carbon data for the region are less plentiful and many of the sources that could contribute to that organic aerosol are both diverse and not well characterized. The objective of this present study is to examine the origin of the carbonaceous aerosol at Grand Canyon National Park during the summer season based on molecular tracer techniques applied to source and ambient samples collected specifically for this purpose.

Mazurek, M.A.; Hallock, K.A.; Leach, M. [Brookhaven National Lab., Upton, NY (United States); Mason-Jones, M.; Mason-Jones, H.; Salmon, L.G.; Winner, D.A.; Cass, G.R. [California Inst. of Tech., Pasadena, CA (United States). Dept. of Environmental Engineering Science

1993-06-01

314

?-caryophyllinic acid: An atmospheric tracer for ?-caryophyllene secondary organic aerosol  

NASA Astrophysics Data System (ADS)

The chemical compositions of ambient PM2.5 samples, collected in Research Triangle Park, North Carolina, USA, and a sample of secondary organic aerosol, formed by irradiating a mixture of the sesquiterpene (SQT), ?-caryophyllene, and oxides of nitrogen in a smog chamber, were chemically analyzed using derivative-based GC-MS methods. The analyses showed the presence of an oxidized compound, tentatively identified as ?-caryophyllinic acid, in both the ambient PM2.5 field samples and in the smog chamber sample. The seasonal concentrations of ?-caryophyllinic acid in the ambient PM2.5 samples were 0.5, 0.9, 7.0, and 0.5 ng m-3 during the winter, spring, summer and fall respectively. To our knowledge, this is the first time that an oxidation product of a sesquiterpene, a hydrocarbon with high secondary organic aerosol yields and emitted from plants and trees in significant quantities, has been detected in ambient PM2.5 samples.

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

2007-03-01

315

Ergosterol, arabitol and manitol as tracers for biological aerosols  

NASA Astrophysics Data System (ADS)

Airborne fungi can cause a wide array of adverse responses in humans depending on the type and quantity present. Since dose and human response is highly individual, the sensitivity of a person exposed is also an important consideration. The abundance of bioaerosols in the ambient air and their health impacts depend on the season and on the environmental conditions. In order to quantify and identify fungi bioaerosols’ contribution to atmospheric aerosols and the impact to public health, it has been suggested to use chemicals that are typical of bioaerosols as biomarkers in chemical analysis of collected aerosols. An often used biomarker for determining the fungal biomass is ergosterol. Recently, Bauer et al. (2008) found that mannitol and arabitol concentrations are correlated with the fungal spore counts in atmospheric PM10. In this study, ergosterol, arabitol and mannitol were quantified in ambient aerosols collected in the Eastern Mediterranean region for 12 months in order to understand their annual and seasonal behavior and to test whether arabitol and mannitol are good predictors of fungi. Finally, correlations between ergosterol abundances with inorganic ions, humidity, temperature, and synoptic data in order to identify dominant sources of fungal spores were also studied. We will report on the measurements and the observed correlations between the different tracers.

Rudich, Y.; Burshtein, N.; Lang-Yona, N.

2010-12-01

316

Hourly In-Situ Measurements of Organic Aerosol Speciation by Thermal desorption Aerosol GC/MS-FID (TAG): Advances in Calibration Procedures  

NASA Astrophysics Data System (ADS)

Thermal desorption Aerosol GC/MS-FID (TAG) provides a novel means of obtaining hourly in-situ measurements of organic aerosol speciation. In a typical chromatogram, hundreds to thousands of organic compounds may be present, making careful compound identification and calibration practices a critical part of obtaining reliable and useful data. This presentation will focus on a series of field calibrations performed during sampling of ambient aerosols using the TAG instrument. TAG couples inertial collection of fine particulates with diameters between 0.1 and 2.5 ?m and analysis via gas phase chromatography and mass spectrometry following thermal desorption of a sample. This combined collection and analysis system provides hourly speciation of a wide range of organic compounds that is limited only by the compatibility of the GC column (DB-5MS) and feasible temperature range (50-300 °C). The direct introduction of thermally desorbed species into the GC/MS-FID avoids sample handling artifact concerns and costly analytical sample processing. A modified collection cell was introduced to the system that allows direct, in-situ injections of compound standards to calibrate and monitor the performance of the instrument. An evaluation of this approach is presented using results from UC Berkeley laboratory studies and a 5 week urban aerosol study in Riverside, California conducted July-August, 2005 as part of the Study of Organic Aerosols in Riverside (SOAR) campaign. Examples are given where the retention times of a large selection of compounds used as injection standards assisted in the positive identification and quantitation of organic species in ambient aerosols.

Kreisberg, N. M.; Williams, B. J.; Goldstein, A. H.; Hering, S. V.

2005-12-01

317

The Juelich large Aerosol Chamber  

Microsoft Academic Search

The large Aerosol Chamber is designed for the investigation of nighttime atmospheric chemistry. The Aerosol Chamber is a dark chamber and is operated at ambient temperature and pressure conditions. It is constructed as a double wall system: a fully welded aluminum box (7m x 7m x 5.3m) and an equally sized fully heat sealed Teflon bag hanging from the ceiling.

Th. Mentel; A. Wahner; M. Folkers

2003-01-01

318

Hygroscopicity frequency distributions of secondary organic aerosols  

NASA Astrophysics Data System (ADS)

Secondary organic compounds are an important component of ambient aerosol and potentially lower the supersaturation that is required for individual particles to serve as cloud condensation nuclei (CCN). Secondary organic aerosol (SOA) formed from the oxidation of a single precursor can be composed of many different compounds and their overall CCN efficiency has been reported for many different SOA systems. An aerosol's CCN efficiency can be described by a single hygroscopicity parameter, ?. However, this ? comprises an unknown distribution of underlying ?-values resulting from each individual compound in the SOA mixture. Here we report on a new technique for characterizing this distribution of?. Precursor hydrocarbons were oxidized in an environmental chamber to form SOA, which was collected on filters and extracted using ethyl acetate. Extracts were then fractionated by reversed-phase high-performance liquid chromatography using gradient elution with acetonitrile and water. The eluate was atomized, the solvent was removed by evaporation, and the residual aerosol particles were analyzed as a function of retention time using scanning flow CCN analysis. Kappa-values generally decreased with component retention time, consistent with expected decreasing polarity. Averaged SOA?-values reconstructed by integrating over the chromatogram agreed well with values measured for SOA sampled directly from the environmental chamber, suggesting that?for SOA represents the volume-weighted average of the constituent compounds'?-values. We anticipate that our measured hygroscopicity distributions will serve as validation points for mechanistic models that seek to predict the generation and evolution of organic aerosol composition and properties in the atmosphere.

Suda, S. R.; Petters, M. D.; Matsunaga, A.; Sullivan, R. C.; Ziemann, P. J.; Kreidenweis, S. M.

2012-02-01

319

Oxygen and sulfur isotopic composition of volcanic sulfate aerosol at the point of emission  

NASA Astrophysics Data System (ADS)

Volcanic sulfate aerosol is emitted from the vents of many active volcanoes, but its origin has not yet been explained. We report the first measurements of the isotopic compositions of near-vent volcanic aerosol sulfate and use the combined sulfur and oxygen isotope systematics of the aerosol and magma at Masaya volcano, Nicaragua, to draw preliminary conclusions about the production mechanism of near-source volcanic sulfate. The sulfate aerosol does not display a significant mass-independent oxygen or sulfur isotopic signature, which suggests that primary volcanic aerosol does not contribute to the larger mass-independent anomalies found in some ambient atmospheric aerosols and as preserved in ice cores. The oxygen isotope composition of the sulfate appeared to become heavier on the particle filters with increasing amount of sample collected and suggests that the ?18O value of the sulfate aerosol is <8‰. The sulfur isotopic composition of the sulfate did not vary with sample loading on the filters and had a mean ?34S value of 7.7 ± 0.8‰, similar to that of the magma (6.6 ± 0.2‰). The low ?17O value, the ?18O value of the magma (6.6 ± 0.3‰) and the high ?18O value of atmospheric oxygen (23.5‰) suggest that known atmospheric oxidation pathways at ambient temperatures are not the major routes of production for this sulfate. Instead, the isotopic systematics of aerosol and magma are consistent with sulfate production either by high-temperature equilibration of the magmatic gas mixture with small amounts of atmospheric oxygen or by direct emission of SO42- from the magma.

Mather, T. A.; McCabe, J. R.; Rai, V. K.; Thiemens, M. H.; Pyle, D. M.; Heaton, T. H. E.; Sloane, H. J.; Fern, G. R.

2006-09-01

320

Radioactive Aerosols as an Index of Air Pollution in the City of Thessaloniki, Greece  

SciTech Connect

This study summarizes results of an investigation done in order to find out how the radioactive aerosols of {sup 7}Be could serve as indicators of air pollution conditions. Beryllium-7 is a cosmic-ray produced radionuclide with an important fraction of its production to take place in the upper troposphere. Once it is formed is rapidly associated with submicron aerosol particles and participates in the formation and growth of the accumulation mode aerosols, which is a major reservoir of pollutants in the atmosphere. In order to define any influence of AMAD of {sup 7}Be aerosols by air pollution conditions, the aerodynamic size distribution of {sup 7}Be aerosols was determined by collecting samples at different locations in the suburban area of the city of Thessaloniki, including rural areas, industrial areas, high elevations, marine environment and the airport area. The aerodynamic size distribution of {sup 7}Be aerosols in different locations was obtained by using Andersen 1-ACFM cascade impactors and the Activity Median Aerodynamic Diameter (AMAD) was determined. Some dependency of the AMADs on height has been observed, while in near marine environment the {sup 7}Be activity size distribution was dominant in the upper size range of aerosol particles. Low AMADs as low as 0.62 to 0.74 {mu}m of {sup 7}Be aerosols have been observed at locations characterized with relative low pollution, while it is concluded that in the activity size distribution of ambient aerosols, {sup 7}Be changes to larger particle sizes in the presence of pollutants, since low AMADs of {sup 7}Be aerosols have been observed at low polluted locations. Preliminary data of simultaneous measurements of {sup 214}Pb and {sup 212}Pb with gaseous air pollutants CO, NO, NO{sub X}, SO{sub 2} and total suspended particulate matter (TSP) show that radon decay products near the ground could be a useful index of air pollution potential conditions and transport processes in the boundary layer.

Ioannidou, A.; Papastefanou, C. [Nuclear Physics and Elementary Particle Physics Division, Physics Department, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

2010-01-21

321

Radioactive Aerosols as an Index of Air Pollution in the City of Thessaloniki, Greece  

NASA Astrophysics Data System (ADS)

This study summarizes results of an investigation done in order to find out how the radioactive aerosols of 7Be could serve as indicators of air pollution conditions. Beryllium-7 is a cosmic-ray produced radionuclide with an important fraction of its production to take place in the upper troposphere. Once it is formed is rapidly associated with submicron aerosol particles and participates in the formation and growth of the accumulation mode aerosols, which is a major reservoir of pollutants in the atmosphere. In order to define any influence of AMAD of 7Be aerosols by air pollution conditions, the aerodynamic size distribution of 7Be aerosols was determined by collecting samples at different locations in the suburban area of the city of Thessaloniki, including rural areas, industrial areas, high elevations, marine environment and the airport area. The aerodynamic size distribution of 7Be aerosols in different locations was obtained by using Andersen 1-ACFM cascade impactors and the Activity Median Aerodynamic Diameter (AMAD) was determined. Some dependency of the AMADs on height has been observed, while in near marine environment the 7Be activity size distribution was dominant in the upper size range of aerosol particles. Low AMADs as low as 0.62 to 0.74 ?m of 7Be aerosols have been observed at locations characterized with relative low pollution, while it is concluded that in the activity size distribution of ambient aerosols, 7Be changes to larger particle sizes in the presence of pollutants, since low AMADs of 7Be aerosols have been observed at low polluted locations. Preliminary data of simultaneous measurements of 214Pb and 212Pb with gaseous air pollutants CO, NO, NOX, SO2 and total suspended particulate matter (TSP) show that radon decay products near the ground could be a useful index of air pollution potential conditions and transport processes in the boundary layer.

Ioannidou, A.; Papastefanou, C.

2010-01-01

322

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

EPA Science Inventory

Ambient sampling was conducted in Riverside, California during the 2005 Study of Organic Aerosols in Riverside to characterize the composition and sources of organic aerosol using a variety of state-of-the-art instrumentation and source apportionment techniques....

323

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

324

High energy laser beam scattering by atmospheric aerosol aureoles  

Microsoft Academic Search

The interaction of high energy laser beams with aerosols in the atmosphere produces non-uniform temperature variations in the medium surrounding the aerosols. These non-uniformities in the ambient index of refraction act as scattering centers for the laser beam. The basic thermodynamics and conservation equations are solved numerically for pulsed high energy lasers interacting with aerosol water droplet systems. The resulting

L. C. Rosen; J. Ipser

1988-01-01

325

Atmospheric aerosol measurement problems  

NASA Technical Reports Server (NTRS)

The present knowledge of the atmospheric aerosols is summarized briefly with respect to geographical distribution, time variations, optical properties, chemical nature, and natural and artificial sources. The measurement techniques for determining aerosol properties are summarized with the limitations and results from each. The problems resulting from variations in refractive index, shape, composition, volatile constituents, relative humidity and time from collection until measurement are described. Needed measurements on atmospheric aerosols are outlined with some of the latest methods for obtaining them, including the needs and goals of some world-wide programs.

Harris, F. S., Jr.

1978-01-01

326

Aerosolized avian influenza virus by laboratory manipulations  

PubMed Central

Background Avian H5N1 influenza viruses present a challenge in the laboratory environment, as they are difficult to collect from the air due to their small size and relatively low concentration. In an effort to generate effective methods of H5N1 air removal and ensure the safety of laboratory personnel, this study was designed to investigate the characteristics of aerosolized H5N1 produced by laboratory manipulations during research studies. Results Normal laboratory procedures used to process the influenza virus were carried out independently and the amount of virus polluting the on-site atmosphere was measured. In particular, zootomy, grinding, centrifugation, pipetting, magnetic stirring, egg inoculation, and experimental zoogenetic infection were performed. In addition, common accidents associated with each process were simulated, including breaking glass containers, syringe injection of influenza virus solution, and rupturing of centrifuge tubes. A micro-cluster sampling ambient air pollution collection device was used to collect air samples. The collected viruses were tested for activity by measuring their ability to induce hemagglutination with chicken red blood cells and to propagate in chicken embryos after direct inoculation, the latter being detected by reverse-transcription PCR and HA test. The results showed that the air samples from the normal centrifugal group and the negative-control group were negative, while all other groups were positive for H5N1. Conclusions Our findings suggest that there are numerous sources of aerosols in laboratory operations involving H5N1. Thus, laboratory personnel should be aware of the exposure risk that accompanies routine procedures involved in H5N1 processing and take proactive measures to prevent accidental infection and decrease the risk of virus aerosol leakage beyond the laboratory.

2012-01-01

327

Modeling of multiphase atmospheric aerosols  

NASA Astrophysics Data System (ADS)

This paper presents a mathematical model that describes the chemical composition and growth rate of atmospheric aerosols containing sulfate and nitrate, and that is applicable over the entire range of relative humidities. The model describes aerosols as consisting of an insoluble core, a soluble solid shell and an aqueous film. The chemical composition of the solid and aqueous aerosol phases in this model is governed by the following processes: (1) the chemical equilibria between the ambient gas and the aerosol liquid phases and between the aerosol liquid and the soluble solid phases; (2) the diffusion-limited condensation of H 2SO 4 and (3) the liquid-phase chemical reaction of SO 2. At low humidities the liquid phase may not be thermodynamically viable, in which case the model then treats the solid-phase/gas-phase equilibrium. Model simulations were conducted to study the effect of ambient relative humidity and gas-phase concentrations on the aerosol chemical composition and growth rate. Results indicate that (1) precipitation of (NH 4) 2SO 4 occurs at its point of deliquescence (i.e. at a relative humidity of close to 80%) even in the presence of other electrolytes; (2) within the uncertainty of the thermodynamic data, the saturation products of NH 3 and HNO 3 for a liquid-coated aerosol and a dry aerosol are in agreement with each other; (3) the aerosol concentrations correspond closely to (NH 4) 2SO 4 and NH 4NO 3 for both liquid and solid phases, i.e. NH 4HSO 4 is predicted to exist in negligible amounts under most conditions and (4) the assumption of either an ideal internal mixture or an external mixture for dry sulfates and nitrate aerosols has little effect on model predictions.

Saxena, Pradeep; Seigneur, Christian; Peterson, Thomas W.

328

COMPARISON OF PREDICTED AND MEASURED AEROSOL OPTICAL AND PHYSICAL PROPERTIES IN AUSTRALIAN CITIES  

Microsoft Academic Search

Summary Comprehensive information on the optical and physical properties of aerosol particles is important for evaluating or estimating the effects of aerosol on air quality, visibility degradation and radiative forcing. The determination of extinction of light by ambient aerosol particles can be achieved successfully by the accurate estimation of aerosol refractive index using observed and modelled size-resolved chemical composition data.

Yoshiteru Iinuma; Gail P. Box; John L. Gras; Melita Keywood; Gregory Ayers

329

Measurements at the Mt. Rainier IMPROVE Site of Aerosol Mass, Size and Composition and their Correlation with Particle Hygroscopicity  

NASA Astrophysics Data System (ADS)

We report preliminary results from an aerosol study at the Mt. Rainier (MORA) IMPROVE site, sponsored by EPRI. This collaboration involved researchers from the Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory, the Desert Research Institute (DRI) and Texas A&M University (TAMU), and was done with the cooperation of the National Park Service. The atmospheric aerosol composition at MORA is influenced by a number of anthropogenic and biogenic sources, providing a rich environment for fundamental aerosol studies. The primary purpose of this study was to use state-of-the-art aerosol instrumentation and measurement techniques to address issues related to the “IMPROVE light extinction reconstruction equation” adopted by the EPA to estimate light extinction from atmospheric aerosol concentrations. The combination of these diverse measurements also provides significant insight into fundamental aerosol properties such as aging and radiative forcing. New instrumentation included a high resolution aerosol time-of-flight mass spectrometer (Aerodyne HToF-AMS) for real-time, size resolved chemical measurements that directly address: 1) the IMPROVE assumption that sulfate, nitrate, and organic carbon (OC) concentrations vary directly with particle size as air masses age during transport, 2) the relationship between hygroscopic growth and oxygenated organic (OOA) composition, 3) the OCM (organic mass)/OC ratio, and 4) the relationship between chemical composition and the ambient hydration state. The ambient hydration state was measured in-situ by the TAMU group with an ambient state hygroscopic tandem differential mobility analyzer (AS-HTDMA)). This modification of the classic HTDMA records the changes in particle size at ambient RH from forcing sudden changes of hydration state. Aerosols were classified at ambient RH with a diameter of Da. The sample was dried to <20%, typically below the crystallization point of most aerosols and alternately returned to ambient RH (path 1) or humidified to 85-95% RH and then returned to ambient RH (path 2). The ambient hydration state is inferred from the ratio of the final diameter (Df) on paths 1 and 2 to Da. These results will be used to assess the validity of the IMPROVE assumption that hygroscopic growth follows the hysteresis branch of the ammonium sulfate growth curve and may also provide the basis for more sophisticated ambient hydration state models, representing a significant advance in the understanding of atmospheric aerosols. PM2.5 aerosol samples were collected daily by DRI for measurement of chemical composition, the water soluble organic (WSOC) fraction, the OCM/OC ratio, and separation of WSOC from inorganic constituents. Hygroscopic growth curves of isolated WSOC will be measured at TAMU by HTDMA. These results will be compared with aerosol composition (e.g., OOA/HOA ratio) measured in-situ with the HToF-AMS.

Alexander, M. L.; Newburn, M.; Lowenthal, D. H.; Zielinska, B.; Samy, S.; Collins, D. R.; Taylor, N.; Kumar, N.

2009-12-01

330

Studies of organic aerosol and aerosol-cloud interactions  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols can influence society and the environment in many ways including altering the planet's energy budget, the hydrologic cycle, and public health. However, the Fourth Assessment Report of the Intergovernmental Panel on Climate Change indicates that the anthropogenic radiative forcing associated with aerosol effects on clouds has the highest uncertainty in the future climate predictions. This thesis focuses on the nature of the organic fraction of ambient particles and how particles interact with clouds using a combination of tools including aircraft and ground measurements, models, and satellite data. Fine aerosol particles typically contain between 20 - 90% organic matter by mass and a major component of this fraction includes water soluble organic carbon (WSOC). Consequently, water-soluble organic species can strongly influence aerosol water-uptake and optical properties. However, the chemical composition of this fraction is not well-understood. PILS-TOC was used to characterize WSOC in ambient aerosol in Los Angeles, California. The spatial distribution of WSOC was found to be influenced by (i) a wide range of aerosol sources within this urban metropolitan area, (ii) transport of pollutants by the characteristic daytime sea breeze trajectory, (iii) topography, and (iv) secondary production during transport. Meteorology is linked with the strength of many of these various processes. Many methods and instruments have been used to study aerosol-cloud interactions. Each observational platform is characterized by different temporal/spatial resolutions and operational principles, and thus there are disagreements between different studies for the magnitude of mathematical constructs used to represent the strength of aerosol-cloud interactions. This work points to the sensitivity of the magnitude of aerosol-cloud interactions to cloud lifetime and spatial resolution of measurements and model simulations. Failure to account for above-cloud aerosol layers and wet scavenging are also shown to cause biases in the magnitude of aerosol-cloud interaction metrics. Air mass source origin and meteorology are also shown to be important factors that influence aerosol-cloud interactions. The results from this work contribute towards a better understanding of atmospheric aerosols and are meant to improve parameterizations that can be embedded in models that treat aerosol affects on clouds, precipitation, air quality, and public health.

Duong, Hanh To

331

AEROSOL SAMPLING INLETS AND INHALABLE PARTICLES  

EPA Science Inventory

The problem of sampling aerosols from the ambient atmosphere has been considered from a theoretical point of view. Following a review of the various samplers and inlets used in ambient sampling, the factors contributing to high sampling efficiency for large particles are discusse...

332

Fast determination of trace elements on aerosol-loaded filters by X-ray fluorescence analysis considering the inhomogeneous elemental distribution.  

PubMed

X-ray fluorescence (XRF) analysis was successfully applied for the determination of Ca, Cu, Fe, Mn, Ni, Pb, V and Zn on aerosol filters with a diameter of 150 mm. Ambient aerosol was collected on quartz-fibre filters by Digitel high-volume samplers. For XRF analysis three small filter pieces with a diameter of 32 mm were cut out of each filter, considering the radial dependence of elemental distribution on the filter. Elemental concentration decreases by 8-10% from the centre to the outer circle for coarse mode elements. Distribution of fine mode elements display only small radial dependence (2-4%). Results of quantitative analysis by XRF were compared with atomic spectrometric methods (GF-AAS, ICP-OES). The good agreement between the methods confirmed the application of XRF spectrometry for routine analysis of filter samples loaded with ambient aerosol. PMID:11225923

Steinhoff, G; Haupt, O; Dannecker, W

2000-01-01

333

Sampling, characterization, and remote sensing of aerosols formed in the atmospheric hydrolysis of uranium hexafluoride  

SciTech Connect

When gaseous uranium hexafluoride (UF/sub 6/) is released into the atmosphere, it rapidly reacts with ambient moisture to form an aerosol of uranyl fluoride (UO/sub 2/F/sub 2/) and hydrogen fluoride (HF). As part of our Safety Analysis program, we have performed several experimental releases of HF/sub 6/ in contained volumes in order to investigate techniques for sampling and characterizing the aerosol materials. The aggregate particle morphology and size distribution have been found to be dependent upon several conditions, including the temperature of the UF/sub 6/ at the time of its release, the relative humidity of the air into which it is released, and the elapsed time after the release. Aerosol composition and settling rate have been investigated using stationary samplers for the separate collection of UO/sub 2/F/sub 2/ and HF and via laser spectroscopic remote sensing (Mie scatter and infrared spectroscopy). 25 refs., 16 figs., 5 tabs.

Bostick, W.D.; McCulla, W.H.; Pickrell, P.W.

1984-05-01

334

Sampling and characterization of aerosols formed in the atmospheric hydrolysis of UF/sub 6/  

SciTech Connect

When gaseous UF/sub 6/ is released into the atmosphere, it rapidly reacts with ambient moisture to form an aerosol of uranyl fluoride and HF. As part of our Safety Analysis program, we have performed several experimental releases of UF/sub 6/ (from natural uranium) in contained volumes in order to investigate techniques for sampling and characterizing the aerosol materials. The aggregrate particle morphology and size distribution have been found to be dependent upon several conditions, including the relative humidity at the time of the release and the elapse time after the release. Aerosol composition and settling rate have been investigated using isokinetic samplers for the separate collection of UO/sub 2/F/sub 2/ and HF, and via laser spectroscopic remote sensing (Mie scatter and infrared spectroscopy). 8 references.

Bostick, W.D.; McCulla, W.H.; Pickrell, P.W.; Branam, D.A.

1983-01-01

335

Contributions of isoprene, monoterpenes, ?-caryophyllene, and toluene to secondary organic aerosols in Hong Kong during the summer of 2006  

Microsoft Academic Search

Isoprene, monoterpenes, ?-caryophyllene, and toluene are known to be important secondary organic aerosol (SOA) precursors. In this study, characteristic SOA tracers of these precursors were quantified in ambient samples of PM2.5 taken in Hong Kong and their contributions to SOA were estimated using a tracer-based method. Samples were collected every other day from four sampling sites during a field measurement

Di Hu; Qijing Bian; Teresa W. Y. Li; Alexis K. H. Lau; Jian Zhen Yu

2008-01-01

336

Mount St. Helens aerosol evolution  

SciTech Connect

Stratospheric aerosol samples were collected using a wire impactor during the year following the eruption of Mt. St. Helens. Analysis of samples show that aerosol volume increased for 6 months due to gas-to-particle conversion and then decreased to background levels in the following 6 months.

Oberbeck, V.R.; Farlow, N.H.; Fong, W.; Snetsinger, K.G.; Ferry, G.V.; Hayes, D.M.

1982-09-01

337

Atmospheric processing of organic aerosols over the Pacific ocean during the CALNEX 2010 study  

NASA Astrophysics Data System (ADS)

The sources and composition of atmospheric aerosols are important to characterize in order to improve our understanding of their impact on air quality and climate. As part of the CALNEX field study, high resolution time-of-flight aerosol mass spectrometer (HR-AMS) data were collected every 5 minutes onboard the research vessel, RV-Atlantis from May 13-June 8, 2010. Sampling was alternated between ambient air pulled through a thermal denuder and directly sampling ambient (bypass); only the bypass measurements are considered here. The measurements were made along the California coastline from the Los Angeles basin to the ship channels near San Francisco. A wide range of emission sources and atmospheric ages were encountered including emissions from ships, industrial processes, urban centres (Los Angeles, San Francisco, Sacramento), marine emissions and biogenic sources. Three airmass regions distinguished by the extent of aerosol processing were identified: LA Basin with fresh to aged aerosol; clean marine with moderate to aged aerosol and northern California with moderately aged aerosol. Positive Matrix Factorization (PMF) analysis of the HR-AMS organic aerosol (OA) resulted in the identification of four interpretable components; hydrocarbon-like OA (HOA), low-volatility oxygenated OA (LV-OOA) and two semi-volatile oxygenated OA (SV-OOA). The two SV-OOA components are similar except that one component appears to be more correlated with primary emissions and the other influenced by biogenics. Interpretation of these factors is accomplished through comparison with a comprehensive suite of other measurements and the evolution of the OA composition is demonstrated through the application of the Van Krevelen space (H/C vs O/C).

Hayden, K. L.; Massoli, P.; Canagaratna, M.; Onasch, T. B.; Li, S.; Nuaaman, I.; McLaren, R.; Vlasenko, A. L.; Worsnop, D. R.; Sueper, D.; Williams, E. J.; Quinn, P.

2012-12-01

338

Vertical Profiles of Aerosol Optical Properties Over Central Illinois and Comparison with Surface and Satellite Measurements  

NASA Technical Reports Server (NTRS)

Between June 2006 and September 2009, an instrumented light aircraft measured over 400 vertical profiles of aerosol and trace gas properties over eastern and central Illinois. The primary objectives of this program were to (1) measure the in situ aerosol properties and determine their vertical and temporal variability and (2) relate these aircraft measurements to concurrent surface and satellite measurements. Underflights of the CALIPSO satellite show reasonable agreement in a majority of retrieved profiles between aircraft-measured extinction at 532 nm (adjusted to ambient relative humidity) and CALIPSO-retrieved extinction, and suggest that routine aircraft profiling programs can be used to better understand and validate satellite retrieval algorithms. CALIPSO tended to overestimate the aerosol extinction at this location in some boundary layer flight segments when scattered or broken clouds were present, which could be related to problems with CALIPSO cloud screening methods. The in situ aircraft-collected aerosol data suggest extinction thresholds for the likelihood of aerosol layers being detected by the CALIOP lidar. These statistical data offer guidance as to the likelihood of CALIPSO's ability to retrieve aerosol extinction at various locations around the globe.

Sheridan P. J.; Andrews, E.; Ogren, J A.; Tackett, J. L.; Winker, D. M.

2012-01-01

339

Quantification and radiocarbon source apportionment of black carbon in atmospheric aerosols using the CTO-375 method  

NASA Astrophysics Data System (ADS)

To make progress towards linking the atmosphere and biogeosphere parts of the black carbon (BC) cycle, a chemothermal oxidation method (CTO-375), commonly applied for isolating BC from complex geomatrices such as soils, sediments and aquatic particles, was applied to investigate the BC also in atmospheric particles. Concentrations and 14C-based source apportionment of CTO-375 based BC was established for a reference aerosol (NIST RM-8785) and for wintertime aerosols collected in Stockholm and in a Swedish background area. The results were compared with thermal-optical (OC/EC) measurements. For NIST RM-8785, a good agreement was found between the BC CTO-375 concentration and the reported elemental carbon (EC) concentration measured by the "Speciation Trends Network—National Institute of Occupational Safety and Health" method (EC NIOSH) with BC CTO-375 of 0.054±0.002 g g -1 and EC NIOSH of 0.067±0.008 g g -1. In contrast, there was an average factor of ca. 20 difference between BC CTO-375 and EC NIOSH for the ambient Scandinavian wintertime aerosols, presumably reflecting a combination of BC CTO-375 isolating only the recalcitrant soot-BC portion of the BC continuum and the EC NIOSH metric inadvertently including some intrinsically non-pyrogenic organic matter. Isolation of BC CTO-375 with subsequent off-line radiocarbon analysis yielded fraction modern values (fM) for total organic carbon (TOC) of 0.93 (aerosols from a Swedish background area), and 0.58 (aerosols collected in Stockholm); whereas the fM for BC CTO-375 isolates were 1.08 (aerosols from a Swedish background area), and 0.87 (aerosols collected in Stockholm). This radiocarbon-based source apportionment suggests that contribution from biomass combustion to cold-season atmospheric BC CTO-375 in Stockholm was 70% and in the background area 88%.

Zencak, Zdenek; Elmquist, Marie; Gustafsson, Örjan

340

Design and testing of a shrouded probe for airborne aerosol sampling in a high velocity airstream  

NASA Astrophysics Data System (ADS)

Tropospheric aerosols play an important role in many phenomena related to global climate and climate change and two important parameters, aerosol size distribution and concentration, have been the focus of a great deal of attention. To study these parameters it is necessary to obtain a representative sample of the ambient aerosol using an airborne aerosol sampling probe mounted on a suitably equipped aircraft. Recently, however, serious questions have been raised (Huebert et al., 1990; Baumgardner et al., 1991) concerning the current procedures and techniques used in airborne aerosol sampling. We believe that these questions can be answered by: (1) use of a shrouded aerosol sampling probe, (2) proper aerodynamic sampler design using numerical simulation techniques, (3) calculation of the sampler calibration curve to be used in determining free-stream aerosol properties from measurements made with the sampler and (4) wind tunnel tests to verify the design and investigate the performance of the sampler at small angles of attack (typical in airborne sampling applications due to wind gusts and aircraft fuel consumption). Our analysis is limited to the collection of insoluble particles representative of the global tropospheric 'background aerosol' (0.1-2.6 ?m diameter) whose characteristics are least likely to be affected by the collection process. We begin with a survey of the most relevant problems associated with current airborne aerosol samplers and define the physical quantity that we wish to measure. This includes the derivation of a unique mathematical expression relating the free-stream aerosol size distribution to aerosol data obtained from the airborne measurements with the sampler. We follow with the presentation of the results of our application of Computational Fluid Dynamics (CFD) and Computational Particle Dynamics (CPD) to the design of a shrouded probe for airborne aerosol sampling of insoluble tropospheric particles in the size range 0.1 to 15 ?m diameter at an altitude of 6069 m (20,000 ft) above sea level (asl). Our aircraft of choice is the National Center for Atmospheric Research (NCAR) EC-130 Geoscience Research aircraft whose cruising speed at a sampling altitude of 6069 m asl is 100 m/s. We calculate the aspiration efficiency of the sampler and estimate the transmission efficiency of the diffuser probe based on particle trajectory simulations. We conclude by presenting the results of a series of qualitative and quantitative wind tunnel tests of the airflow through a plexiglass prototype of the sampler to verify our numerical simulations and predict the performance of the sampler at angles of attack from 0o to 15o.

Cain, Stuart Arthur

1997-07-01

341

A method for sizing submicrometer particles in air collected on formvar films and imaged by scanning electron microscope  

NASA Astrophysics Data System (ADS)

Here we present a method to systematically investigate single aerosol particles collected on formvar film supported by a copper grid, with Scanning Electron Microscopy (SEM) operating at low accelerating voltage. The method enabled us to observe the surface of the sample grid at high resolution. Subsequent processing of the images with digital image analysis provided a statistically and quantitative size resolved information on the particle population including their morphology on the film. The quality of the presented method was established using polystyrene nanospheres as standards in the size range expected for ambient aerosol particles over remote marine areas (20-900 nm in diameter). The sizing was found to be critically dependent on the contrasting properties of the particles towards the collection substrate. The relative standard deviation of the diameters of polystyrene nanospheres was better than 10% for sizes larger than 40 nm and 18% for 21 nm particles compared with the manufacturer's certificate. The size distributions derived from the microscope images of airborne aerosols collected during a research expedition to north of 80° N in the summer of 2008 were compared with simultaneously collected number particle size distributions seen by a Twin Differential Mobility Particle Sizer. We captured a representative fraction of the aerosol particles with SEM and were able to causally relate the determined morphological properties of the aerosol under investigation to aerosol transformation processes in air being advected from the marginal ice edge/open sea south of 80° N.

Hamacher-Barth, E.; Jansson, K.; Leck, C.

2013-06-01

342

Microanalysis of indoor aerosols and the impact of a compact high-efficiency particulate air (HEPA) filter system.  

PubMed

Aerosol particles in municipal atmospheres are of increasing public health concern; however, since most of our time is spent indoors, indoor aerosols must be researched in counterpart. Compact High-Efficiency Particulate Air (HEPA) filter systems are commonly employed in residences to alleviate airborne dust concentrations. In this study, a detailed and original methodology was used to determine concentrations and types of submicrometer aerosols, as well as of large (> 4 microns) dust particles. Scanning electron microscopy was used to quantify and characterize ambient aerosols collected from filtered and non-filtered rooms. Particle concentrations were significantly lower in samples collected in the presence of the filter system (mean 23 to 8 coarse particles liter-1, 63% reduction; 13 to 3 inorganic submicron particles cm-3, 76% reduction; 85 to 33 total submicron particles cm-3, 62% reduction; all P < 0.05). This study provides a new methodology for analysis of indoor aerosols and new data on their physico-chemical characteristics. Since the filter systems are effective at reducing submicron aerosol concentrations, they may improve the health of individuals such as asthmatics, who experience health problems caused by anthropogenic fine particles. PMID:10195274

Abraham, M E

1999-03-01

343

Comparison of three aerosol sampling techniques and the differences in the nitrate determined by each  

SciTech Connect

Ambient aerosol samples were collected simultaneously with three different methods, one a size fractionated impactor sampler and two filter samplers. Infrared spectroscopy was used to analyze the collected aerosol using attenuated total internal reflection for the impactor samples and direct transmission through ultra-thin teflon membrane filters for the filter samples. All samples were analyzed as soon as possible after collection; some were reanalyzed after being stored in closed petri dishes for up to 10 days. A major purpose of the study was to evaluate the neutralization of acidic sulfate aerosols after sample collection by the filtration techniques. No acidic sulfate was found in any of the samples collected during the field study. However, significant differences were observed in the nitrate content of the samples collected by the different samplers. Also, in several samples collected with the ATR impactor the nitrate content decreased upon storage. In some cases the nitrate absorbance bands diminished to zero; in other cases the nitrate initially decreased and then remained stable; in yet another case, a high level of nitrate persisted over several days. The results indicate that two different types of nitrate compounds were present in the samples, one more ''volatile'' than the other, although the infrared spectra were consistent with both of them being ammonium nitrate.

Johnson, S.A.; Kumar, R.

1987-01-01

344

Traffic emission factors of ultrafine particles: effects from ambient air.  

PubMed

Ultrafine particles have a significant detrimental effect on both human health and climate. In order to abate this problem, it is necessary to identify the sources of ultrafine particles. A parameterisation method is presented for estimating the levels of traffic-emitted ultrafine particles in terms of variables describing the ambient conditions. The method is versatile and could easily be applied to similar datasets in other environments. The data used were collected during a four-week period in February 2005, in Gothenburg, as part of the Göte-2005 campaign. The specific variables tested were temperature (T), relative humidity (RH), carbon monoxide concentration (CO), and the concentration of particles up to 10 ?m diameter (PM(10)); all indicators are of importance for aerosol processes such as coagulation and gas-particle partitioning. These variables were selected because of their direct effect on aerosol processes (T and RH) or as proxies for aerosol surface area (CO and PM(10)) and because of their availability in local monitoring programmes, increasing the usability of the parameterization. Emission factors are presented for 10-100 nm particles (ultrafine particles; EF(ufp)), for 10-40 nm particles (EF(10-40)), and for 40-100 nm particles (EF(40-100)). For EF(40-100) no effect of ambient conditions was found. The emission factor equations are calculated based on an emission factor for NO(x) of 1 g km(-1), thus the particle emission factors are easily expressed in units of particles per gram of NO(x) emitted. For 10-100 nm particles the emission factor is EF(ufp) = 1.8 × 10(15) × (1 - 0.095 × CO - 3.2 × 10(-3) × T) particles km(-1). Alternative equations for the EFs in terms of T and PM(10) concentration are also presented. PMID:22858604

Janhäll, Sara; Molnar, Peter; Hallquist, Mattias

2012-09-01

345

Secondary Organic Aerosol Formation from 2-Methyl-3-Buten-2-ol (MBO) Photooxidation: Evidence for Acid-Catalyzed Reactive Uptake of Epoxide  

NASA Astrophysics Data System (ADS)

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 aerosol acidity levels. Results indicate SOA was enhanced with increasing aerosol acidity especially under low-NO conditions. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C5H12O6S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. This organosulfate species was also observed and correlated with aerosol acidity from ambient fine aerosol (PM2.5) samples that were collected from different field campaigns where MBO emissions are important, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Importantly, this compound can account for as high as 1% of the total organic aerosol mass in the atmosphere. It is hypothesized that MBO epoxide generated under low-NO conditions is the precursor to MBO SOA based upon the above results. Thus, the MBO epoxide was synthesized in high purity to investigate its potential to form SOA via reactive uptake in a series of controlled dark chamber studies. Our results suggest the MBO epoxide substantially forms SOA only in the presence of acidic seed aerosols. The chemical characterization results of the SOA constituents are consistent with field measurements in terms of the major SOA tracers.

Surratt, J. D.; Zhang, H.; Worton, D. R.; Lewandowski, M.; Ortega, J.; Zhang, Z.; Lin, Y.; Park, J.; Kristensen, K.; Bhathela, N.; Campuzano-Jost, P.; Day, D. A.; Jimenez, J. L.; Jaoui, M.; Offenberg, J. H.; Kleindienst, T. E.; Gilman, J. B.; De Gouw, J. A.; Park, C.; Schade, G. W.; Frossard, A. A.; Russell, L. M.; Kaser, L.; Jud, W.; Hansel, A.; Karl, T.; Glasius, M.; Gold, A.; Seinfeld, J.; Guenther, A. B.

2012-12-01

346

Supercritical Fluid Extraction and Analysis of Tropospheric Aerosol Particles  

NASA Astrophysics Data System (ADS)

An integrated sampling and supercritical fluid extraction (SFE) cell has been designed for whole-sample analysis of organic compounds on tropospheric aerosol particles. The low-volume extraction cell has been interfaced with a sampling manifold for aerosol particle collection in the field. After sample collection, the entire SFE cell was coupled to a gas chromatograph; after on-line extraction, the cryogenically -focused sample was separated and the volatile compounds detected with either a mass spectrometer or a flame ionization detector. A 20-minute extraction at 450 atm and 90 ^circC with pure supercritical CO _2 is sufficient for quantitative extraction of most volatile compounds in aerosol particle samples. A comparison between SFE and thermal desorption, the traditional whole-sample technique for analyses of this type, was performed using ambient aerosol particle samples, as well as samples containing known amounts of standard analytes. The results of these studies indicate that SFE of atmospheric aerosol particles provides quantitative measurement of several classes of organic compounds. SFE provides information that is complementary to that gained by the thermal desorption analysis. The results also indicate that SFE with CO _2 can be validated as an alternative to thermal desorption for quantitative recovery of several organic compounds. In 1989, the organic constituents of atmospheric aerosol particles collected at Niwot Ridge, Colorado, along with various physical and meteorological data, were measured during a collaborative field study. Temporal changes in the composition of samples collected during summertime at the rural site were studied. Thermal desorption-GC/FID was used to quantify selected compounds in samples collected during the field study. The statistical analysis of the 1989 Niwot Ridge data set is presented in this work. Principal component analysis was performed on thirty-one variables selected from the data set in order to ascertain different source and process components, and to examine concentration changes in groups of variables with respect to time of day and meteorological conditions. Seven orthogonal groups of variables resulted from the statistical analysis; the groups serve as molecular markers for different biologic and anthropogenic emission sources. In addition, the results of the statistical analysis were used to investigate how several emission source contributions vary with respect to local atmospheric dynamics. Field studies were conducted in the urban environment in and around Boulder, CO. to characterize the dynamics, chemistry, and emission sources which affect the composition and concentration of different size-fractions of aerosol particles in the Boulder air mass. Relationships between different size fractions of particles and some gas-phase pollutants were elucidated. These field studies included an investigation of seasonal variations in the organic content and concentration of aerosol particles, and how these characteristics are related to local meteorology and to the concentration of some gas-phase pollutants. The elemental and organic composition of aerosol particles was investigated according to particle size in preliminary studies of size-differentiated samples of aerosol particles. In order to aid in future studies of urban aerosol particles, samples were collected at a forest fire near Boulder. Molecular markers specific to wood burning processes will be useful indicators of residential wood burning activities in future field studies.

Hansen, Kristen J.

347

Indian aerosols: present status.  

PubMed

This article presents the status of aerosols in India based on the research activities undertaken during last few decades in this region. Programs, like International Geophysical Year (IGY), Monsoon Experiment (MONEX), Indian Middle Atmospheric Program (IMAP) and recently conducted Indian Ocean Experiment (INDOEX), have thrown new lights on the role of aerosols in global change. INDOEX has proved that the effects of aerosols are no longer confined to the local levels but extend at regional as well as global scales due to occurrence of long range transportation of aerosols from source regions along with wind trajectories. The loading of aerosols in the atmosphere is on rising due to energy intensive activities for developmental processes and other anthropogenic activities. One of the significant observation of INDOEX is the presence of high concentrations of carbonaceous aerosols in the near persistent winter time haze layer over tropical Indian Ocean which have probably been emitted from the burning of fossil-fuels and biofuels in the source region. These have significant bearing on the radiative forcing in the region and, therefore, have potential to alter monsoon and hydrological cycles. In general, the SPM concentrations have been found to be on higher sides in ambient atmosphere in many Indian cities but the NOx concentrations have been found to be on lower side. Even in the haze layer over Indian Ocean and surrounding areas, the NOx concentrations have been reported to be low which is not conducive of O3 formation in the haze/smog layer. The acid rain problem does not seem to exist at the moment in India because of the presence of neutralizing soil dust in the atmosphere. But the high particulate concentrations in most of the cities' atmosphere in India are of concern as it can cause deteriorated health conditions. PMID:12492171

Mitra, A P; Sharma, C

2002-12-01

348

Exposures to acidic aerosols.  

PubMed Central

Ambient monitoring of acid aerosols in four U.S. cities and in a rural region of southern Ontario clearly show distinct periods of strong acidity. Measurements made in Kingston, TN, and Steubenville, OH, resulted in 24-hr H+ ion concentrations exceeding 100 nmole/m3 more than 10 times during summer months. Periods of elevated acidic aerosols occur less frequently in winter months. The H+ determined during episodic conditions in southern Ontario indicates that respiratory tract deposition can exceed the effects level reported in clinical studies. Observed 12-hr H+ concentrations exceeded 550 nmole/m3 (approximately 27 micrograms/m3 H2SO4). The maximum estimated 1-hr concentration exceeded 1500 nmole/m3 for H+ ions. At these concentrations, an active child might receive more than 2000 nmole of H+ ion in 12 hr and in excess of 900 nmole during the hour when H2SO4 exceeded 50 micrograms/m3.

Spengler, J D; Keeler, G J; Koutrakis, P; Ryan, P B; Raizenne, M; Franklin, C A

1989-01-01

349

Real-time observations of aerosol composition changes  

NASA Astrophysics Data System (ADS)

We have developed a near real-time aerosol particle analyzer that uses a combination of filtration and impaction for particle size classification and collection, and Fourier-transform infrared (FTIR) spectroscopy for analysis. This infrared aerosol analyzer (IAA) supplies full range (2.0 to 20 (mu)m) infrared absorption spectra of the ambient aerosol separated into three different size fractions. The coarse size fraction, greater than 2.5 (mu)m aerodynamic diameter (a.d.), made up largely of crustal matter, is analyzed separately from the fine (0.5 to 2.5 (mu)m a.d.) and the ultra-fine (less than 0.5 (mu)m a.d.) size fractions which contain the secondary particulate matter that is formed in the atmosphere from gaseous and condensed-phase precursors. Separating the three size fractions avoids interactions between the possibly acidic fine fractions and the possibly basic coarse fraction. The collected particulate samples are analyzed in situ by infrared spectroscopy with analytical time resolutions approaching those of trace gas analyzers.

Johnson, Stanley A.; Kumar, Romesh

1989-06-01

350

Aerosol Lidar and MODIS Satellite Comparisons for Future Aerosol Loading Forecast  

NASA Technical Reports Server (NTRS)

Knowledge of the concentration and distribution of atmospheric aerosols using both airborne lidar and satellite instruments is a field of active research. An aircraft based aerosol lidar has been used to study the distribution of atmospheric aerosols in the California Central Valley and eastern US coast. Concurrently, satellite aerosol retrievals, from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument aboard the Terra and Aqua satellites, were take over the Central Valley. The MODIS Level 2 aerosol data product provides retrieved ambient aerosol optical properties (e.g., optical depth (AOD) and size distribution) globally over ocean and land at a spatial resolution of 10 km. The Central Valley topography was overlaid with MODIS AOD (5x5 sq km resolution) and the aerosol scattering vertical profiles from a lidar flight. Backward air parcel trajectories for the lidar data show that air from the Pacific and northern part of the Central Valley converge confining the aerosols to the lower valley region and below the mixed layer. Below an altitude of 1 km, the lidar aerosol and MODIS AOD exhibit good agreement. Both data sets indicate a high presence of aerosols near Bakersfield and the Tehachapi Mountains. These and other results to be presented indicate that the majority of the aerosols are below the mixed layer such that the MODIS AOD should correspond well with surface measurements. Lidar measurements will help interpret satellite AOD retrievals so that one day they can be used on a routine basis for prediction of boundary layer aerosol pollution events.

DeYoung, Russell; Szykman, James; Severance, Kurt; Chu, D. Allen; Rosen, Rebecca; Al-Saadi, Jassim

2006-01-01

351

Aerosol lidar and MODIS satellite comparisons for future aerosol loading forecast  

NASA Astrophysics Data System (ADS)

Knowledge of the concentration and distribution of atmospheric aerosols using both airborne lidar and satellite instruments is a field of active research. An aircraft based aerosol lidar has been used to study the distribution of atmospheric aerosols in the California Central Valley and eastern US coast. Concurrently, satellite aerosol retrievals, from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument aboard the Terra and Aqua satellites, were take over the Central Valley. The MODIS Level 2 aerosol data product provides retrieved ambient aerosol optical properties (e.g., optical depth (AOD) and size distribution) globally over ocean and land at a spatial resolution of 10 km. The Central Valley topography was overlaid with MODIS AOD (5x5 km2 resolution) and the aerosol scattering vertical profiles from a lidar flight. Backward air parcel trajectories for the lidar data show that air from the Pacific and northern part of the Central Valley converge confining the aerosols to the lower valley region and below the mixed layer. Below an altitude of 1 km, the lidar aerosol and MODIS AOD exhibit good agreement. Both data sets indicate a high presence of aerosols near Bakersfield and the Tehachapi Mountains. These and other results to be presented indicate that the majority of the aerosols are below the mixed layer such that the MODIS AOD should correspond well with surface measurements. Lidar measurements will help interpret satellite AOD retrievals so that one day they can be used on a routine basis for prediction of boundary layer aerosol pollution events.

De Young, Russell; Szykman, James; Severance, Kurt; Chu, D. Allen; Rosen, Rebecca; Al-Saadi, Jassim

2006-09-01

352

Measurements of Natural Radioactivity in Submicron Aerosols in Mexico City.  

NASA Astrophysics Data System (ADS)

Natural radionuclides can be useful in evaluating the transport of ozone and aerosols in the troposphere. Beryllium-7, which is produced by cosmic ray interactions in the upper troposphere and lower stratosphere and becomes adsorbed on fine aerosols, can be a useful indicator of upper air transport into a region. Lead-210 is produced by the decay of radon-222 out-gassed into the lower atmosphere from ground-based uranium deposits. Potassium-40, found in soils, can act as a measure of wind-blown dust and also comes from burning of wood and other biomass that is enriched in this natural radioisotope. Thus, both lead-210 and potassium-40 can aid in identification of aerosols sourced in the lower atmosphere. As part of our continuing interest in the lifetimes and sources of aerosols and their radiative effects, we report here measurements of fine aerosol radioactivity in Mexico City, one of the largest megacities in the world. Samples were collected on quartz fiber filters by using cascade impactors (Sierra type, Anderson Instruments) and high-volume air samplers from the rooftop of the main laboratory of El Centro Nacional de Investigacion y Capacitacion Ambiental (CENICA). By using stage 4 of the impactor and timers, we were able to collect integrated samples of sizes > 1 micrometer and < 1 micrometer over 12-hr time periods daily for approximately one month in April 2003. Samples were counted at the University of Illinois at Chicago by using state-of-the-art gamma counting (beryllium-7, 477.6 keV; potassium-40, 1460.8 keV; lead-210, 46.5 keV). The beryllium-7 data indicate one possible upper-air transport event during April 2003. As expected, the lead-210 data indicate very little soil contribution to the fine aerosol. The potassium-40 data showed an increase in fine aerosol potassium during Holy Week that might be attributed to local combustion of biomass fuels. The data will be presented and discussed in light of future data analysis and comparison with other measurements taken during the study. The authors wish to thank the researchers at CENICA. This work was supported by the U.S. Department of Energy, Atmospheric Science Program. We also wish to acknowledge Drs. Mario and Luisa Molina for their help in organizing and directing the Mexico City Metropolitan Area 2003 field study, during which these data were collected.

Gaffney, J. S.; Marley, N. A.; Sterling, K.; Sturchio, N. C.

2003-12-01

353

The Thermodynamic Stability of Multiple Phases In The Particulate Material of Aerosols Containing Both Polar and Non-polar Compounds  

Microsoft Academic Search

Organic compounds can comprise a significant portion of ambient aerosol particulate material (PM ). Current models of organic aerosol formation based on absorptive gas\\/particle partitioning theory have frequently assumed each aerosol particle to be one liquid phase. This assumption is not always correct. Moreover, it will affect the predicted equilibrium composition of modeled aerosols. There are important cases when multiple

G. B. Erdakos; J. F. Pankow

2002-01-01

354

Primary and Secondary Contributions to the Organic Aerosol Over the Amazon Determined by STXM-NEXAFS  

NASA Astrophysics Data System (ADS)

We investigated the morphology and chemical composition of aerosol samples from a pristine tropical environment, the Amazon Basin, using Scanning Transmission X-ray Microscopy - Near Edge X-ray Absorption Fine Structure (STXMNEXAFS) analysis. The NEXAFS spectra were used to estimate the elemental ratios of C, N and O, as well as the chemical bonding state of these elements. The aim of this study was to investigate the microphysical and chemical properties of a tropical background aerosol and its internal mixing state. The samples were collected in the Amazonian rainforest during the rainy season and can be regarded as a nearly pristine background aerosol. Lab-generated SOA-samples (produced by the (photo)oxidation of isoprene, alpha-pinene and beta-caryophyllene), microtome slices of fungal spores, and aerosolized authentic organic compounds were measured as reference samples. The STXM-NEXAFS results of the lab-generated SOA have been analyzed and compared to SOA from the Amazonian region. In the lab samples, SOA occurred as droplets of different sizes, sometimes exhibiting internal structures ('raisin-like' structure). The spectral characteristics of the lab samples depend on the precursors applied for their generation. The Amazonian aerosol was found to be dominated by drop-like organic particles in the fine mode (often in internal mixture with solid particles), and Primary Biological Aerosol Particles (PBAP) in the coarse mode. Liquid organic aerosol coatings were also frequently observed on the PBAPs. Unexpectedly, many ambient SOA samples show a high content of N (around 20% or even more) as well as the frequent occurrence of potassium. Furthermore, the spectra exhibit characteristic signal patterns for different functional groups. In most cases, the spectrum near the C-edge is dominated by either the hydroxyl or the carboxylate signal, but prominent peaks for ketone carbonyls, alkanes and alkenes have also been observed. Based on these results, a new conceptual model for the origin of Amazonian aerosol will be proposed.

Andreae, M. O.; Pöhlker, C.; Wiedemann, K. T.; Sinha, B.; Artaxo, P.; Kilcoyne, D.; Smith, M. L.; Martin, S. T.; Poeschl, U.

2011-12-01

355

Apparatus for rapid measurement of aerosol bulk chemical composition  

DOEpatents

An apparatus and method for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution are provided. The apparatus includes a modified particle size magnifier for producing activated aerosol particles and a collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical methods. The method provided for on-line measurement of chemical composition of aerosol particles includes exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Lee, Yin-Nan E. (East Setauket, NY); Weber, Rodney J. (Atlanta, GA)

2003-01-01

356

Surface science with aerosols  

NASA Astrophysics Data System (ADS)

Experimental surface science with aerosol particles under atmospheric conditions is becoming a realistic possibility. The first part of this critical review focuses on nano-scopic aerosols generated in combustion of organic fuels at ambient pressures. The bizarre shape of soot agglomerates resists a simple definition of size and surface area. Yet a measure of the size known as the mobility diameter can be extracted from the mobility of the particles in their carrier gas. The total surface area must be divided into an active and a passive part. At the active surface, mass, energy, and momentum is exchanged with the molecules of the carrier gas. The active surface thus determines the dynamical properties of the particles. The passive surface is the surface enclosed in the interior as well as the surface in bays or cracks or, with larger particles, in the dead point of the laminar flow; it determines particle properties on a longer time scale. Simple automatic portable sensors measure the number density of airborne particles, their "size" and a characteristic fingerprint of the surface chemistry, making it possible to determine the source from which the particle was emitted. The response time of the sensors is ˜1 s, hence one can monitor dynamical changes of the particles such as adsorption of water in the atmosphere. In the second part we examine a number of surface science techniques that have been used to characterize surfaces important to atmospheric chemistry in more detail, in particular the uptake of water and the influence of surfactants. We illustrate the application of these techniques to the investigation of alkali halide surfaces as a function of relative humidity. Finally we give first examples on how infrared spectroscopy and synchrotron-based ambient pressure X-ray photoelectron spectroscopy have been used to study more realistic aerosol particles, under conditions of ambient humidity. These examples show that in situ chemical analysis of the particles is possible with third generation synchrotron X-ray sources. In the near future, X-ray lasers might reveal the fast dynamics of chemical processes as well. Thus it is within reach to study aerosols under the conditions of the stratosphere. Stratospheric aerosols can reduce the insolation of the earth and may become one of the last resorts of humanity to counteract the effects of global warming.

Bluhm, H.; Siegmann, H. C.

2009-06-01

357

Daily and hourly chemical impact of springtime transboundary aerosols on Japanese air quality  

NASA Astrophysics Data System (ADS)

The regular eastward drift of transboundary aerosol intrusions from the Asian mainland into the NW Pacific region has a pervasive impact on air quality in Japan, especially during springtime. Analysis of 24-h filter samples with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Mass Spectrometry (ICP-MS), and hourly Streaker with Particle Induced X-ray Emission (PIXE) samples collected continuously for six weeks reveal the chemistry of successive waves of natural mineral desert dust ("Kosa") and metalliferous sulphatic pollutants arriving in western Japan during spring 2011. The main aerosol sources recognised by Positive Matrix Factorization (PMF) analysis of Streaker data are mineral dust and fresh sea salt (both mostly in the coarser fraction PM2.5-10), As-bearing sulphatic aerosol (PM0.1-2.5), metalliferous sodic particulate matter (PM) interpreted as aged, industrially contaminated marine aerosol, and ZnCu-bearing aerosols. Whereas mineral dust arrivals are typically highly transient, peaking over a few hours, sulphatic intrusions build up and decline more slowly, and are accompanied by notable rises in ambient concentrations of metallic trace elements such as Pb, As, Zn, Sn and Cd. The magnitude of the loss in regional air quality due to the spread and persistence of pollution from mainland Asia is especially clear when cleansing oceanic air advects westward across Japan, removing the continental influence and reducing concentrations of the undesirable metalliferous pollutants by over 90%. Our new chemical database, especially the Streaker data, demonstrates the rapidly changing complexity of ambient air inhaled during these transboundary events, and implicates Chinese coal combustion as the main source of the anthropogenic aerosol component.

Moreno, T.; Kojima, T.; Amato, F.; Lucarelli, F.; de la Rosa, J.; Calzolai, G.; Nava, S.; Chiari, M.; Alastuey, A.; Querol, X.; Gibbons, W.

2013-02-01

358

Daily and hourly chemical impact of springtime transboundary aerosols on Japanese air quality  

NASA Astrophysics Data System (ADS)

The regular eastward drift of transboundary aerosol intrusions from the Asian mainland into the NW Pacific region has a~pervasive impact on air quality in Japan, especially during springtime. Analysis of 24-h filter samples (ICP-AES and ICP-MS) and hourly Streaker (PIXE) samples of particulate matter collected continuously for six weeks reveal the chemistry of successive waves of natural mineral desert dust ("Kosa") and metalliferous sulphatic pollutants arriving in Western Japan during spring 2011. The main aerosol sources recognised by PMF analysis of Streaker data are mineral dust and fresh sea salt (both mostly in the coarser fraction PM2.5-10), As-bearing sulphatic aerosol (PM0.1-2.5), metalliferous sodic PM interpreted as aged, industrially contaminated marine aerosol, and ZnCu-bearing aerosols. Whereas mineral dust arrivals are typically highly transient, peaking over a few hours, sulphatic intrusions build up and decline more slowly, and are accompanied by notable rises in ambient concentrations of metallic trace elements such as Pb, As, Zn, Sn and Cd. The magnitude of the loss in regional air quality due to the spread and persistence of pollution from mainland Asia is especially clear when cleansing oceanic air advects westward across Japan, removing the continental influence and reducing concentrations of the more undesirable metalliferous pollutants by over 90%. Our new chemical database, especially the Streaker data, demonstrates the rapidly changing complexity of ambient air inhaled during these transboundary events, and implicates Chinese coal combustion as the main source of the anthropogenic aerosol component.

Moreno, T.; Kojima, T.; Amato, F.; Lucarelli, F.; Nava, S.; de la Rosa, J.; Calzolai, G.; Chiari, M.; Alastuey, A.; Querol, X.; Gibbons, W.

2012-09-01

359

Apportionment of urban aerosol sources in Cork (Ireland) by synergistic measurement techniques.  

PubMed

The sources of ambient fine particulate matter (PM2.5) during wintertime at a background urban location in Cork city (Ireland) have been determined. Aerosol chemical analyses were performed by multiple techniques including on-line high resolution aerosol time-of-flight mass spectrometry (Aerodyne HR-ToF-AMS), on-line single particle aerosol time-of-flight mass spectrometry (TSI ATOFMS), on-line elemental carbon-organic carbon analysis (Sunset_EC-OC), and off-line gas chromatography/mass spectrometry and ion chromatography analysis of filter samples collected at 6-h resolution. Positive matrix factorization (PMF) has been carried out to better elucidate aerosol sources not clearly identified when analyzing results from individual aerosol techniques on their own. Two datasets have been considered: on-line measurements averaged over 2-h periods, and both on-line and off-line measurements averaged over 6-h periods. Five aerosol sources were identified by PMF in both datasets, with excellent agreement between the two solutions: (1) regional domestic solid fuel burning - "DSF_Regional," 24-27%; (2) local urban domestic solid fuel burning - "DSF_Urban," 22-23%; (3) road vehicle emissions - "Traffic," 15-20%; (4) secondary aerosols from regional anthropogenic sources - "SA_Regional" 9-13%; and (5) secondary aged/processed aerosols related to urban anthropogenic sources - "SA_Urban," 21-26%. The results indicate that, despite regulations for restricting the use of smoky fuels, solid fuel burning is the major source (46-50%) of PM2.5 in wintertime in Cork, and also likely other areas of Ireland. Whilst wood combustion is strongly associated with OC and EC, it was found that peat and coal combustion is linked mainly with OC and the aerosol from these latter sources appears to be more volatile than that produced by wood combustion. Ship emissions from the nearby port were found to be mixed with the SA_Regional factor. The PMF analysis allowed us to link the AMS cooking organic aerosol factor (AMS_PMF_COA) to oxidized organic aerosol, chloride and locally produced nitrate, indicating that AMS_PMF_COA cannot be attributed to primary cooking emissions only. Overall, there are clear benefits from factor analysis applied to results obtained from multiple techniques, which allows better association of aerosols with sources and atmospheric processes. PMID:24950495

Dall'Osto, Manuel; Hellebust, Stig; Healy, Robert M; O'Connor, Ian P; Kourtchev, Ivan; Sodeau, John R; Ovadnevaite, Jurgita; Ceburnis, Darius; O'Dowd, Colin D; Wenger, John C

2014-09-15

360

Optical discharge in aerosols  

NASA Astrophysics Data System (ADS)

The physical fundamentals of the optical breakdown of aerosols are examined, and a theory is developed for the seed ionization processes in inert and reacting aerosols. The properties of optical discharges of various kinds generated at isolated particles are investigated, as are the characteristics of the collective breakdown mechanism. The probabilistic criteria of the breakdown and the linear transmission dynamics of an ionized atmosphere are discussed. Some results of laboratory and full-scale experiments concerned with the optical, electrodynamic, and acoustic characteristics of an extended laser spark are presented.

Kopytin, Iurii D.; Sorokin, Iurii M.; Skripkin, Aleksandr M.; Belov, N. N.; Bukatyi, V. I.

361

Plasma lactoferrin content: differential effect of steroid administration and infective illnesses: lack of effect of ambient temperature at which specimens are collected.  

PubMed

The effect of parenteral hydrocortisone on plasma lactoferrin concentration, neutrophil count and lactoferrin:neutrophil ratio was assessed in 10 volunteer subjects. Administration of a single dose of corticosteroid was followed by a significant rise i