These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

CHEMICAL CHARACTERIZATION OF EXTRACTABLE ORGANIC MATTER FROM AMBIENT AEROSOLS COLLECTED IN BOISE, ID  

EPA Science Inventory

Fine fraction (2.5 micron) ambient air aerosols were collected in Boise, ID between November, 1986, and February, 1987. wo composite samples of extractable organic matter (EOM) were prepared with partial resolution of chemicals from Boise's wood smoke (WS) and mobile source (MS) ...

2

COMMENTS ON "SIZE DISTRIBUTION OF ORGANONITRATES IN AMBIENT AEROSOL COLLECTED IN HOUSTON, TEXAS," AEROSOL SCIENCE AND TECHNOLOGY, 36:983-992 (2002)  

EPA Science Inventory

A previous article in this journal reported the results of an FTIR analysis of the ambient aerosol collected during a file study in Houston, Texas during August and September of 2000. The emphasis of that article was on the organonitrates collected during the study. In the disc...

3

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...

4

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...

5

Analytical techniques for ambient sulfate aerosols  

SciTech Connect

Work done to further develop the infrared spectroscopic analytical method for the analysis of atmospheric aerosol particles, as well as some exploratory work on a new procedure for determining proton acidity in aerosol samples is described. Earlier work had led to the successful use of infrared (ir) spectrophotometry for the analysis of nitrate, ammonium, and neutral and acidic sulfates in aerosol samples collected by an impactor on a Mylar-film substrate. In this work, a filter-extraction method was developed to prepare filter-collected aerosol samples for ir analysis. A study was made comparing the ir analytical results on filter-collected samples with impactor-collected samples. Also, the infrared analytical technique was compared in field studies with light-scattering techniques for aerosol analysis. A highly sensitive instrument for aerosol analysis using attenuated total internal reflection (ATR) infrared spectroscopy was designed, built, and tested. This instrument provides a measurement sensitivity much greater (by a factor of 6 for SO/sub 4//sup 2 -/) than that obtainable using the KBr-pellet method. This instrument collect size- and time-resolved samples and is potentially capable of providing automated, near real-time aerosol analysis. Exploratory work on a novel approach to the determination of proton acidity in filter- or impactor-collected aerosol samples is also described. In this technique, the acidic sample is reacted with an access of a tagged, vapor-phase base. The unreacted base is flushed off and the amount of the tag retained by the sample is a direct measure of the proton acidity of the sample. The base was tagged with Ge, which can be conveniently determined by the x-ray fluorescence technique.

Johnson, S.A.; Graczyk, D.G.; Kumar, R.; Cunningham, P.T.

1981-06-01

6

Ambient Aerosol Cloud-Forming Potential: CCN Closure Analysis in Boise, Idaho  

E-print Network

Ambient Aerosol Cloud-Forming Potential: CCN Closure Analysis in Boise, Idaho Ryan Collins1 to conduct a closure analysis. The data collection for this project took place in Boise, Idaho from November ­ Aerosol data Logan Callen ­ Preliminary analysis WSU LAR Boise campaign team members Idaho Department

Collins, Gary S.

7

A Methodology to Establish the Morphology of Ambient Aerosols  

PubMed Central

The morphology of ambient particulate matter (PM) is an important characteristic that seldom is measured and reported. A study was performed to determine the viability of a method to establish the distribution of shapes and the fractal dimensions of aggregates of ambient aerosols. Particles of PM with aerodynamic diameter less than or equal to 2.5 ?m (PM2.5) were captured on different days via size-independent electrostatic precipitation at two sites in St. Louis and examined in a scanning electron microscope (SEM). Nonvolatile particles between 0.1 and 2.5 ?m were readily identified via SEM. Particle shapes were classified as fibrous, spherical, agglomerated, or other. A computer program using the nested-squares algorithm was developed and used to determine the fractal dimensions of the aggregates. More particles were collected at the St. Louis-Midwest Supersite on June 14, 2002, than were collected on the Washington University campus loading dock on May 31, 2002, but the campus samples had a higher percentage of aggregates. On one day of sampling at the Supersite, the aggregate fraction was highest in the morning (14.3% between 7:00 and 9:00 a.m.) and steadily declined during the day (1.3% between 5:00 and 7:00 p.m.). The fractal dimensions of the aerosols were 1.65 in the morning (7:00:00 a.m.), decreased to 1.49 (11:00 a.m.1:00 p.m.), and then increased to 1.87 (5:007:00 p.m.). The results show that the fractal dimension is not a static value and that ambient aerosols are not perfectly spherical. PMID:15468660

McDonald, Rafael; Biswas, Pratim

2007-01-01

8

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...

9

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...

10

AEROSOL CHARACTERIZATION OF AMBIENT AIR NEAR A COMMERCIAL LURGI COAL GASIFICATION PLANT, KOSOVO REGION, YUGOSLAVIA  

EPA Science Inventory

Ambient air samples were collected continuously from May 14-29, 1980 to determine if the emissions from a commercial Lurgi coal gasification plant could be identified downwind of the facility. Physical, inorganic, and organic analyses were carried out on the collected aerosol sam...

11

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...

12

Ambient Observations of Aerosols, Novel Aerosol Structures, And Their Engineering Applications  

NASA Astrophysics Data System (ADS)

The role of atmospheric aerosols remains a crucial issue in understanding and mitigating climate change in our world today. These particles influence the Earth by altering the Earth's delicate radiation balance, human health, and visibility. In particular, black carbon particulate matter remains the key driver in positive radiative forcing (i.e., warming) due to aerosols. Produced from the incomplete combustion of hydrocarbons, these compounds can be found in many different forms around the globe. This thesis provides an overview of three research topics: (1) the ambient characterization of aerosols in the Northern Indian Ocean, measurement techniques used, and how these aerosols influence local, regional, and global climate; (2) the exploration of novel soot superaggregate particles collected in the Northern Indian Ocean and around the globe and how the properties of these particles relate to human health and climate forcing; and (3) how aerogelated soot can be produced in a novel, one-step method utilizing an inverted flame reactor and how this material could be used in industrial settings.

Beres, Nicholas D.

13

Analysis of organic aerosols collected on filters by Aerosol Mass Spectrometry for source identification.  

PubMed

Aerosol Mass Spectrometers (AMS) are powerful tools in the analysis of the chemical composition of airborne particles, particularly organic aerosols which are gaining increasing attention. However, the advantages of AMS in providing on-line data can be outweighed by the difficulties involved in its use in field measurements at multiple sites. In contrast to the on-line measurement by AMS, a method which involves sample collection on filters followed by subsequent analysis by AMS could significantly broaden the scope of AMS application. We report the application of such an approach to field studies at multiple sites. An AMS was deployed at 5 urban schools to determine the sources of the organic aerosols at the schools directly. PM1 aerosols were also collected on filters at these and 20 other urban schools. The filters were extracted with water and the extract run through a nebulizer to generate the aerosols, which were analyzed by an AMS. The mass spectra from the samples collected on filters at the 5 schools were found to have excellent correlations with those obtained directly by AMS, with r(2) ranging from 0.89 to 0.98. Filter recoveries varied between the schools from 40 to 115%, possibly indicating that this method provides qualitative rather than quantitative information. The stability of the organic aerosols on Teflon filters was demonstrated by analysing samples stored for up to two years. Application of the procedure to the remaining 20 schools showed that secondary organic aerosols were the main source of aerosols at the majority of the schools. Overall, this procedure provides accurate representation of the mass spectra of ambient organic aerosols and could facilitate rapid data acquisition at multiple sites where AMS could not be deployed for logistical reasons. PMID:24216201

Crilley, Leigh R; Ayoko, Godwin A; Morawska, Lidia

2013-11-25

14

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...

15

Transport and characterization of ambient biological aerosol near Laurel, MD  

NASA Astrophysics Data System (ADS)

Bacterial aerosol have been observed and studied in the ambient environment since the mid nineteenth century. These studies have sought to provide a better understanding of the diversity, variability and factors that control the biological aerosol population. In this study, we show comparisons between diversity of culturable bacteria and fungi, using culture and clinical biochemical tests, and 16S rRNA diversity using Affymetrix PhyloChips. Comparing the culturable fraction and surveying the total 16S rRNA of each sample provides a comprehensive look at the bacterial population studied and allows comparison with previous studies. Thirty-six hour back-trajectories of the air parcels sampled, over the two day period beginning 4 November 2008, provide information on the sources of aerosol sampled on the campus of Johns Hopkins University Applied Physics Laboratory in Laurel, MD. This study indicates that back-trajectory modeling of air parcels may provide insights into the observed diversity of biological aerosol.

Santarpia, J. L.; Cunningham, D.; Gilberry, J.; Kim, S.; Smith, E. E.; Ratnesar-Shumate, S.; Quizon, J.

2010-09-01

16

Physical Properties of Ambient and Laboratory-Generated Secondary Organic Aerosol  

SciTech Connect

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

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

2014-06-17

17

Ambient aerosol analysis using aerosol-time-of-flight mass spectrometry  

SciTech Connect

We have recently developed a technique, Aerosol-Time-of-Flight Mass Spectrometry (ATOFMS), which is capable of real-time determination of the aerodynamic size and chemical composition of individual aerosol particles. In order to obtain such information, the techniques of aerodynamic particle sizing and time-of-flight mass spectrometry are combined in a single instrument. ATOFMS is being used for the direct analysis of ambient aerosols with the goal of establishing correlations between particle size and chemical composition. Currently, measurements are being made to establish potential links between the presence of particular types of particles with such factors as the time of day, weather conditions, and concentration levels of gaseous smog components such as NO{sub x} and ozone. This data will be used to help establish a better understanding of tropospheric gas-aerosol processes. This talk will discuss the operating principles of ATOFMS as well as present the results of ambient analysis studies performed in our laboratory.

Prather, K.A.; Noble, C.A.; Liu, D.Y.; Silva, P.J.; Fergenson, D.F.

1996-10-01

18

Separating Hazardous Aerosols from Ambient Aerosols: Role of Fluorescence-Spectral Determination, Aerodynamic Deflector and Pulse Aerodynamic Localizer (PAL)  

SciTech Connect

An aerosol deflection technique based on the single-shot UV-laser-induced fluorescence spectrum from a flowing particle is presented as a possible front-end bio-aerosol/hazardous-aerosol sensor/identifier. Cued by the fluorescence spectra, individual flowing bio-aerosol particles (1-10 {micro}m in diameter) have been successfully deflected from a stream of ambient aerosols. The electronics needed to compare the fluorescence spectrum of a particular particle with that of a pre-determined fluorescence spectrum are presented in some detail. The deflected particles, with and without going through a funnel for pulse aerodynamic localization (PAL), were collected onto a substrate for further analyses. To demonstrate how hazardous materials can be deflected, TbCl{sub 3} {center_dot} 6H{sub 2}O (a simulant material for some chemical forms of Uranium Oxide) aerosol particles (2 {micro}m in diameter) mixed with Arizona road dust was separated and deflected with our system.

Pan, Yong-Le; Cobler, Patrick J.; Rhodes, Scott A.; Halverson, Justin; Chang, Richard K.

2005-08-22

19

Cloud forming properties of ambient aerosol in the Netherlands and resultant shortwave radiative forcing of climate  

Microsoft Academic Search

This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indirect. Due to the scattering of solar light on aerosol particles the Earth surface receives less radiation

A. Khlystov

1998-01-01

20

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 (~2-6C) 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 10444 ?g/m3, much higher than 7349 ?g/m3of non-foggy period, but during actual fog events the loading reduced to 8523 ?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 0.510.04, higher than that of non-foggy period 0.440.07, 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

21

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

22

LC-MS-MS-TOF analysis of oxygenated organic compounds in ambient aerosol  

NASA Astrophysics Data System (ADS)

Ambient aerosol samples were taken at different sites across Europe. The fine mode aerosol was collected on quartz filters at flow rates of 160 L/min and 500 L/min. These samples were analyzed for organic acids (C>4) by an HPLC system coupled to a hybrid mass spectrometer. The mass spectrometer consists of a quadrupole mass analyzer, a quadrupole collision cell and a time-of-flight mass analyzer (TOF). Analytes were identified by standards when available or MS-MS experiments and exact mass measurements utilizing the high mass resolution of the TOF instrument. Monoterpenes (alpha-pinene, beta-pinene, sabinene, limonene, 3-carene) were ozonolyzed in the laboratory and compared with field samples. Besides the commonly measured organic acids (pinic, pinonic and norpinic acid) sabinic, caric and caronic acid were identified for the first time in ambient aerosol. In addition, nearly all samples showed significant concentrations of newly identified keto dicarboxylic acids (C9 - C12). Laboratory experiments were used to investigate the formation mechanisms of these compounds. By comparing laboratory measurements of wood combustion and field samples from the Eastern Mediterranean region, nitrocatechol was identified as a possible tracer for biomass burning. The data obtained is used to determine the role of biogenic sources in secondary organic aerosol formation.

Roempp, A.; Moortgat, G.

2003-04-01

23

REDOX AND ELECTROPHILIC PROPERTIES OF VAPOR- AND PARTICLE-PHASE COMPONENTS OF AMBIENT AEROSOLS  

PubMed Central

Particulate matter (PM) has been the primary focus of studies aiming to understand the relationship between the chemical properties of ambient aerosols and adverse health effects. Size and chemical composition of PM have been linked to their oxidative capacity which has been postulated to promote or exacerbate pulmonary and cardiovascular diseases. But in the last few years, new studies have suggested that volatile and semivolatile components may also contribute to many adverse health effects. The objectives of this study were: i) assess for the first time the redox and electrophilic potential of vapor-phase components of ambient aerosols, and ii) evaluate the relative contributions of particle- and vapor-fractions to the hazard of a given aerosol. To achieve these objectives vapor- and particle-phase samples collected in Riverside (CA) were subjected to three chemical assays to determine their redox and electrophilic capacities. The results indicate that redox active components are mainly associated with the particle-phase, while electrophilic compounds are found primarily in the vapor-phase. Vapor-phase organic extracts were also capable of inducing the stress responding protein, heme-oxygenase-1 (HO-1), in RAW264.7 murine macrophages. These results demonstrate the importance of volatile components in the overall oxidative and electrophilic capacity of aerosols, and point out the need for inclusion of vapors in future health and risk assessment studies. PMID:20152964

Eiguren-Fernandez, Arantzazu; Shinyashiki, Masaru; Schmitz, Debra A.; DiStefano, Emma; Hinds, William; Kumagai, Yoshito; Cho, Arthur K.; Froines, John R.

2010-01-01

24

Ambient and indoor particulate aerosols generated by dairies in the Southern High Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objectives were to quantify and size ambient aerosolized dust in and around the facilities of four Southern High Plains dairies of New Mexico and to determine where health of workers might be vulnerable to particulate aerosols, based on aerosol concentrations that exceed national air quality sta...

25

EQUILIBRIUM SIZE OF ATMOSPHERIC AEROSOL SULFATES AS A FUNCTION OF PARTICLE ACIDITY AND AMBIENT RELATIVE HUMIDITY  

EPA Science Inventory

Acid aerosol events in Uniontown, Pennsylvania, were studied during the summer of 1990. ize-fractionated acid aerosols were collected using a microorifice cascade impactor. he collected samples were analyzed for hydrogen, sulfate, nitrate, and ammonium ion concentrations. hese me...

26

An intercomparison study of analytical methods used for quantification of levoglucosan in ambient aerosol filter samples  

NASA Astrophysics Data System (ADS)

The monosaccharide anhydrides (MAs) levoglucosan, galactosan and mannosan are products of incomplete combustion and pyrolysis of cellulose and hemicelluloses, and are found to be major constituents of biomass burning (BB) aerosol particles. Hence, ambient aerosol particle concentrations of levoglucosan are commonly used to study the influence of residential wood burning, agricultural waste burning and wildfire emissions on ambient air quality. A European-wide intercomparison on the analysis of the three monosaccharide anhydrides was conducted based on ambient aerosol quartz fiber filter samples collected at a Norwegian urban background site during winter. Thus, the samples' content of MAs is representative for BB particles originating from residential wood burning. The purpose of the intercomparison was to examine the comparability of the great diversity of analytical methods used for analysis of levoglucosan, mannosan and galactosan in ambient aerosol filter samples. Thirteen laboratories participated, of which three applied high-performance anion-exchange chromatography (HPAEC), four used high-performance liquid chromatography (HPLC) or ultra-performance liquid chromatography (UPLC) and six resorted to gas chromatography (GC). The analytical methods used were of such diversity that they should be considered as thirteen different analytical methods. All of the thirteen laboratories reported levels of levoglucosan, whereas nine reported data for mannosan and/or galactosan. Eight of the thirteen laboratories reported levels for all three isomers. The accuracy for levoglucosan, presented as the mean percentage error (PE) for each participating laboratory, varied from -63 to 20%; however, for 62% of the laboratories the mean PE was within 10%, and for 85% the mean PE was within 20%. For mannosan, the corresponding range was -60 to 69%, but as for levoglucosan, the range was substantially smaller for a subselection of the laboratories; i.e. for 33% of the laboratories the mean PE was within 10%. For galactosan, the mean PE for the participating laboratories ranged from -84 to 593%, and as for mannosan 33% of the laboratories reported a mean PE within 10%. The variability of the various analytical methods, as defined by their minimum and maximum PE value, was typically better for levoglucosan than for mannosan and galactosan, ranging from 3.2 to 41% for levoglucosan, from 10 to 67% for mannosan and from 6 to 364% for galactosan. For the levoglucosan to mannosan ratio, which may be used to assess the relative importance of softwood versus hardwood burning, the variability only ranged from 3.5 to 24 . To our knowledge, this is the first major intercomparison on analytical methods used to quantify monosaccharide anhydrides in ambient aerosol filter samples conducted and reported in the scientific literature. The results show that for levoglucosan the accuracy is only slightly lower than that reported for analysis of SO42- (sulfate) on filter samples, a constituent that has been analysed by numerous laboratories for several decades, typically by ion chromatography and which is considered a fairly easy constituent to measure. Hence, the results obtained for levoglucosan with respect to accuracy are encouraging and suggest that levels of levoglucosan, and to a lesser extent mannosan and galactosan, obtained by most of the analytical methods currently used to quantify monosaccharide anhydrides in ambient aerosol filter samples, are comparable. Finally, the various analytical methods used in the current study should be tested for other aerosol matrices and concentrations as well, the most obvious being summertime aerosol samples affected by wildfires and/or agricultural fires.

Yttri, K. E.; Schnelle-Kreis, J.; Maenhaut, W.; Abbaszade, G.; Alves, C.; Bjerke, A.; Bonnier, N.; Bossi, R.; Claeys, M.; Dye, C.; Evtyugina, M.; Garca-Gacio, D.; Hillamo, R.; Hoffer, A.; Hyder, M.; Iinuma, Y.; Jaffrezo, J.-L.; Kasper-Giebl, A.; Kiss, G.; Lpez-Mahia, P. L.; Pio, C.; Piot, C.; Ramirez-Santa-Cruz, C.; Sciare, J.; Teinil, K.; Vermeylen, R.; Vicente, A.; Zimmermann, R.

2015-01-01

27

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 m. During heating in ambient air for 1h, diesel soot particles were found to be stable up to 470C, but complete combustion occurred in a narrow temperature interval between about 480 and 510C. 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 200C to at least 500C. Incompletely burnt bioaerosol matter was still found after heating to 600C. 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

28

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 m. During heating in ambient air for 1 h, diesel soot particles were found to be stable up to 480C, but complete combustion occurred in a narrow temperature interval between about 490 and 510C. 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 200C to at least 500C. Incompletely burnt bioaerosol matter was still found after heating to 600C. 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

29

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...

30

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...

31

BIOGENIC CONTRIBUTION TO PM-2.5 AMBIENT AEROSOL FROM RADIOCARBON MEASUREMENTS  

EPA Science Inventory

Knowledge of the relative contributions of biogenic versus anthropogenic sources to ambient aerosol is of great interest in the formulation of strategies to achieve nationally mandated air quality standards. Radiocarbon (Carbon-14) measurements provide a means to quantify the ...

32

Collection of Aerosolized Human Cytokines Using Teflon Filters  

PubMed Central

Background Collection of exhaled breath samples for the analysis of inflammatory biomarkers is an important area of research aimed at improving our ability to diagnose, treat and understand the mechanisms of chronic pulmonary disease. Current collection methods based on condensation of water vapor from exhaled breath yield biomarker levels at or near the detection limits of immunoassays contributing to problems with reproducibility and validity of biomarker measurements. In this study, we compare the collection efficiency of two aerosol-to-liquid sampling devices to a filter-based collection method for recovery of dilute laboratory generated aerosols of human cytokines so as to identify potential alternatives to exhaled breath condensate collection. Methodology/Principal Findings Two aerosol-to-liquid sampling devices, the SKC Biosampler and Omni 3000, as well as Teflon filters were used to collect aerosols of human cytokines generated using a HEART nebulizer and single-pass aerosol chamber setup in order to compare the collection efficiencies of these sampling methods. Additionally, methods for the use of Teflon filters to collect and measure cytokines recovered from aerosols were developed and evaluated through use of a high-sensitivity multiplex immunoassay. Our results show successful collection of cytokines from pg/m3 aerosol concentrations using Teflon filters and measurement of cytokine levels in the sub-picogram/mL concentration range using a multiplex immunoassay with sampling times less than 30 minutes. Significant degradation of cytokines was observed due to storage of cytokines in concentrated filter extract solutions as compared to storage of dry filters. Conclusions Use of filter collection methods resulted in significantly higher efficiency of collection than the two aerosol-to-liquid samplers evaluated in our study. The results of this study provide the foundation for a potential new technique to evaluate biomarkers of inflammation in exhaled breath samples. PMID:22574123

McKenzie, Jennifer H.; McDevitt, James J.; Fabian, M. Patricia; Hwang, Grace M.; Milton, Donald K.

2012-01-01

33

Aerosol physical, chemical and optical properties observed in the ambient atmosphere during haze pollution conditions  

NASA Astrophysics Data System (ADS)

Aerosols properties in the ambient atmosphere may differ significantly from sampling results due to containing of abundant water content. We performed sun-sky radiometer measurements in Beijing during 2011 and 2012 winter to obtain distribution of spectral and angular sky radiance. The measurements are then used to retrieve aerosol physical, chemical and optical properties, including single scattering albedo, size distribution, complex refractive indices and aerosol component fractions identified as black carbon, brown carbon, mineral dust, ammonium sulfate-like components and water content inside particle matters. We found that during winter haze condition aerosol is dominated by fine particles with center radius of about 0.2 micron. Fine particles contribute about 93% to total aerosol extinction of solar light, and result in serious decrease of atmospheric visibility during haze condition. The percentage of light absorption of haze aerosol can up to about 10% among its total extinction, much higher than that of unpolluted conditions, that causes significant radiative cooling effects suppressing atmospheric convection and dispersion of pollutants. Moreover, the average water content occupies about one third of the ambient aerosol in volume which suggests the important effect of ambient humidity in the formation of haze pollution.

Li, Zhengqiang; Xie, Yisong; Li, Donghui; Li, Kaitao; Zhang, Ying; Li, Li; Lv, Yang; Qie, Lili; Xu, Hua

34

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

NASA Astrophysics Data System (ADS)

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 before they enter the oceans. The major thrust is the study of the mechanisms 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_3 and CaCO_3. The iron solubility in aerosol solutions is far higher than that normally expected for seawater and even rainwater. Thus aerosol solution processes may be the major factor that determines how much iron will readily dissolve when particles enter the ocean. Iron photochemical and speciation studies indicated that only 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_2O_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. These results suggest that marine aerosol solutions are characterized by extreme conditions that can greatly affect the chemical processes that occur in the aerosol phase. As a result, the mobilization of iron and its subsequent fate in natural waters will be strongly dependent on the past history of the aerosol particles in the atmosphere.

Zhu, Xiaorong

1992-01-01

35

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

36

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

37

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

38

DESIGN, FABRICATION AND TESTING OF AMBIENT AEROSOL SAMPLER INLETS  

EPA Science Inventory

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 inde...

39

Isolation of ambient aerosols of known critical supersaturation: the differential critical supersaturation separator (DSCS)  

E-print Network

continuous flow thermal gradient diffusion cloud chambers housed within a single enclosure. Descriptions of instrument operation, construction and calibration data collected, when pure ammonium sulfate aerosols were injected into the DScS for operation at 0...

Osborn, Robert John

2007-09-17

40

Technical Note: The application of an improved gas and aerosol collector for ambient air pollutants in China  

NASA Astrophysics Data System (ADS)

An improved Gas and Aerosol Collector (GAC) equipped with a newly designed aerosol collector and a set of dull-polished wet annular denuder (WAD) was developed based on a Steam Jet Aerosol Collector (SJAC) sampler. Combined with Ion Chromatography (IC) the new sampler performed well in laboratory tests with high collection efficiencies for SO2 (above 98%) and particulate sulfate (as high as 99.5%). When applied in two major field campaigns (rural and coastal sites) in China, the GAC-IC system provided high-quality data in ambient conditions even under high loadings of pollutants. Its measurements were highly correlated with data by other commercial instruments such as the SO2 analyzer (43c, Thermo-Fisher, USA; R2 as 0.96), the HONO analyzer (LOPAP, Germany; R2 as 0.91 for nighttime samples), a filter sampler (Tianhong, China; R2 as 0.86 for SO42-), and Aerosol Mass Spectrometer (AMS, Aerodyne, USA; R2 above 0.77 for major species) over a wide range of concentrations. Through the application of the GAC-IC system, it was identified that 70% of chloride and nitrate by the filter method could be lost during daytime sampling due to high temperature in the rural site of Kaiping. In Changdao field campaign (coastal site) the comparison with the measurements by the GAC-IC suggested that the collection efficiency of AMS might be greatly influenced by high relative humidity (RH) especially in coastal or marine environment. Through laboratory and field studies, this instrument is proved highly reliable, which is particularly useful in future intensive campaigns or long-term monitoring stations to study various environmental issues such as secondary aerosol and haze formation, as well as climate change.

Dong, H.-B.; Zeng, L.-M.; Hu, M.; Wu, Y.-S.; Zhang, Y.-H.; Slanina, J.; Zheng, M.; Wang, Z.-F.; Jansen, R.

2012-03-01

41

Instrument Would Detect and Collect Biological Aerosols  

NASA Technical Reports Server (NTRS)

A proposed compact, portable instrument would sample micron-sized airborne particles, would discriminate between biological ones (e.g., bacteria) and nonbiological ones (e.g., dust particles), and would collect the detected biological particles for further analysis. The instrument is intended to satisfy a growing need for means of rapid, inexpensive collection of bioaerosols in a variety of indoor and outdoor settings. Purposes that could be served by such collection include detecting airborne pathogens inside buildings and their ventilation systems, measuring concentrations of airborne biological contaminants around municipal waste-processing facilities, monitoring airborne effluents from suspected biowarfare facilities, and warning of the presence of airborne biowarfare agents

Savoy, Steve; Mayo, Mike

2006-01-01

42

Aerosol Lifecycle Field Campaign Information Collection  

E-print Network

Sciences Division (ASD) of the Environmental Sciences Department at Brookhaven National Lab conducted was given password access to view and edit the pages. The site was formatted using language specific of this project was to keep the wiki site updated and collect information about the instruments and happenings

43

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, 23.0N, 72.6E, 49 m asl) and a high-altitude station (Mt. Abu, 24.6N, 72.7E, 1680 m asl) located in a high-dust semiarid region of western India, reveal characteristic pattern of temporal variability consistent over three years (20002002). The relatively high concentrations of 210Pb

N. Rastogi; M. M. Sarin

2008-01-01

44

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

45

Technical Note: The application of an improved gas and aerosol collector for ambient air pollutants in China  

NASA Astrophysics Data System (ADS)

An improved Gas and Aerosol Collector (GAC) equipped with a newly designed aerosol collector and a set of dull-polished wet annular denuder (WAD) was developed based on a Steam Jet Aerosol Collector (SJAC) sampler. Combined with Ion Chromatography (IC) the new sampler performed well in laboratory tests with high collection efficiencies for SO2 (above 98%) and particulate sulfate (as high as 99.5%). An inter-comparison between the GAC-IC system and the filter-pack method was performed and the results indicated that the GAC-IC system could supply reliable particulate sulfate, nitrate, chloride, and ammonium data in field measurement with a much wider range of ambient concentrations. When applied in two major field campaigns (rural and coastal sites) in China, the GAC-IC system provided high-quality data in ambient conditions even under high loadings of pollutants. Its measurements were highly correlated with data by other commercial instruments such as the SO2 analyzer (43c, Thermo-Fisher, USA; R2 as 0.96), the HONO analyzer (LOPAP, Germany; R2 as 0.91 for samples from 15:00 to 07:00), a filter sampler (Tianhong, China; R2 as 0.86 for SO42-), and Aerosol Mass Spectrometer (AMS, Aerodyne, USA; R2 above 0.77 for major species) over a wide range of concentrations. Through the application of the GAC-IC system, it was identified that 70% of chloride and nitrate by the filter method could be lost during daytime sampling due to high temperature in the rural site of Kaiping. In Changdao field campaign (coastal site), though a particle dryer was applied, its drying efficiency was not well considered for the collection efficiency of AMS seemed still interfered a bit by local high relative humidity. If the inter-comparison was done with relative humidity below 50%, the correlations ranged from 0.81 to 0.94 for major species. Through laboratory and field studies, this instrument is proved particularly useful in future intensive campaigns or long-term monitoring stations to study various environmental issues such as secondary aerosol and haze formation, as well as climate change.

Dong, H.-B.; Zeng, L.-M.; Hu, M.; Wu, Y.-S.; Zhang, Y.-H.; Slanina, J.; Zheng, M.; Wang, Z.-F.; Jansen, R.

2012-11-01

46

Hygroscopic Characteristics of Organic Laden Ambient Aerosols in Yosemite National Park  

NASA Astrophysics Data System (ADS)

Water absorption by inorganic compounds can be modeled with some degree of certainty; however, water uptake by ambient organic aerosols remains speculative. To improve the understanding of organic hygroscopicity, an aerosol characterization study was conducted at Yosemite National Park, California, starting in July and ending in the first week of September 2002. High time resolution measurement (15-minute time increments) of PM2.5 ionic species (Cl-, SO42-, NO3-, Na+, NH4+, K+, Mg2+, and Ca2+) were measured using PILS (Particle-Into-Liquid-System)/IC (Ion Chromatography). Commercially available annular denuders and a PM2.5 cyclone (URG) were used upstream of the PILS/IC to remove particles greater than 2.5 ?m and acidic and basic gases. A dual wavelength aethalometer and an R&P particulate carbon monitor were used to measure carbon on a semi-continuous basis while a DRUM sampler allowed for semi-continuous estimates of concentrations of elements associated with crustal material. Standard IMPROVE type samplers were used to measure 24-hr integrated samples of these same aerosols. Two nephelometers operated in tandem, one dry and the other with a controlled humidity environment, were used to measure f(RH) = bscat(RH)/bscat,dry, where bscat(RH) is the scattering coefficient measured at some relative humidity and bscat,dry is the scattering coefficient measured at RH <10%. The aerosol composition was highly variable in time, with a strong diurnal cycle. Organic carbon mass was observed to be, on the average, 70% of the fine mass with days where its contribution was well over 95% of the mass. Measurements of carbon isotopes revealed the fraction of carbon from biogenic sources to range from approximately 73 to 95%. Water soluble potassium was highly correlated with carbon mass, suggesting the influence of wood smoke. The ionic fraction of the aerosol consisted primarily of ammonium sulfate and in most cases nitrate was in the form of sodium nitrate. Fine soil mass was less than 1% of PM2.5 mass. The ambient aerosol was observed to deliquesce on days when the inorganic and organic aerosol were approximately equal in concentration; however, on days when the organic component was dominant, only smooth f(RH) curves were observed. Equilibrium models, exercised in combination with Mie scattering theory, were used to predict atmospheric aerosol water content and associated increases in aerosol scattering coefficient. The analyses suggest that in most cases the hygroscopic growth of inorganic salts alone could account for the observed increase in scattering as a function of relative humidity.

Malm, W. C.; Day, D. E.; Kreidenweis, S. M.; Collett, J. L.; Carrico, C. M.; Lee, T.; Bench, G.; Carrillo, J.

2003-12-01

47

Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer.  

PubMed

The application of mass spectrometric techniques to the real-time measurement and characterization of aerosols represents a significant advance in the field of atmospheric science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technology together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chemical speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diameters between approximately 50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble average data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected laboratory experiments and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum ultraviolet (VUV) photo-ionization, Li+ ion, and electron attachment) and high-resolution ToF mass spectrometers, that yield more detailed information about the organic aerosol component are also described. PMID:17230437

Canagaratna, M R; Jayne, J T; Jimenez, J L; Allan, J D; Alfarra, M R; Zhang, Q; Onasch, T B; Drewnick, F; Coe, H; Middlebrook, A; Delia, A; Williams, L R; Trimborn, A M; Northway, M J; DeCarlo, P F; Kolb, C E; Davidovits, P; Worsnop, D R

2007-01-01

48

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

49

Mass absorption efficiency of elemental carbon (EC) in ambient aerosols: Characterization from high-altitude sites in India  

NASA Astrophysics Data System (ADS)

The mass absorption efficiency (MAE, ?abs) is an important parameter for the determination of atmospheric black carbon (BC) mass concentration by optical instruments. Recent studies suggest that ?abs is highly variable in space and time depending on the type of emission sources of carbonaceous aerosols and analytical methods employed. We have studied changes in ?abs of elemental carbon (EC) from two high-altitude sites in India; Mt Abu (coordinates; 1700 m asl): located in the Thar desert of western India (dominated by mineral dust) and Manora Peak (coordinates; 2200 m asl): located in the southern slopes of Himalaya (influenced by anthropogenic sources in the Indo-Gangetic Plain. Based on the data set collected during 2005-2006, we document large temporal variability in ?abs of EC (range: 3.6-13.7 m2g-1) at Mt Abu. The average ?abs (9.82.1 m2g-1) is similar to the most accepted value of 10 m2g-1 for ambient aerosols. Analytical data suggest that mineral dust contributes ~70% of the total suspended particulate (TSP) mass. Assuming it to be externally mixed with carbonaceous species and its absorption efficiency of 0.009 m2g-1, absorption due to mineral dust is no more than ~10% at Mt Abu. In contrast, long-term (2005-2008) average of 12.82.9 m2g-1 for ?abs (range: 6.1-19.1 m2g-1) is documented at Manora Peak. We suggest that relatively high ?abs of EC at Manora Peak is attributed to the internal mixing of carbonaceous aerosols and anthropogenic species (NO3- and SO4--) during transport from the Indo-Gangetic Plain. These results have implications to large seasonal variability in the aerosol absorption properties (due to change in the morphological feature of EC) and atmospheric radiative forcing on a regional scale.

Ram, K.; Sarin, M.

2012-12-01

50

Determination of the stable carbon isotopic compositions of 2-methyltetrols in ambient aerosols from the Changbai Mountains.  

PubMed

Isoprene is one of the most important non-methane hydrocarbons (NMHCs) in the troposphere: it is a significant precursor of O(3) and it affects the oxidative state of the atmosphere. The diastereoisomeric 2-methyltetrols, 2-methylthreitol and 2-methylerythritol, are marker compounds of the photooxidation products of atmospheric isoprene. In order to obtain valuable information on the delta(13)C value of isoprene in the atmosphere, the stable carbon isotopic compositions of the 2-methyltetrols in ambient aerosols were investigated. The 2-methyltetrols were extracted from filter samples and derivatized with methylboronic acid, and the delta(13)C values of the methylboronate derivatives were determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The delta(13)C values of the 2-methyltetrols were then calculated through a simple mass balance equation between the 2-methyltetrols, methylboronic acid and the methylboronates. The delta(13)C values of the 2-methyltetrols in aerosol samples collected at the Changbai Mountain Nature Reserves in eastern China were found to be -24.66 +/- 0.90 per thousand and -24.53 +/- 1.08 per thousand for 2-methylerythritol and 2-methylthreitol, respectively. Based on the measured isotopic composition of the 2-methyltetrols, the average delta(13)C value of atmospheric isoprene is inferred to be close to or slightly heavier than -24.66 per thousand at the collection site during the sampling period. PMID:20486258

Li, Li; Deng, Shihuai; Wang, Wu; Li, Huaijian; Zhang, Xiaohong; Sheng, Guoying; Fu, Jiamo; Bi, Xinhui; Sun, Baiye

2010-06-15

51

The Collection 6 MODIS aerosol products over land and ocean  

NASA Astrophysics Data System (ADS)

The twin Moderate resolution Imaging Spectroradiometer (MODIS) sensors have been flying on Terra since 2000 and Aqua since 2002, creating an extensive data set of global Earth observations. Here, we introduce the Collection 6 (C6) algorithm to retrieve aerosol optical depth (AOD) and aerosol size parameters from MODIS-observed spectral reflectance. While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. The C6 aerosol data set will be created from three separate retrieval algorithms that operate over different surface types. These are the two "Dark Target" (DT) algorithms for retrieving (1) over ocean (dark in visible and longer wavelengths) and (2) over vegetated/dark-soiled land (dark in the visible), plus the "Deep Blue" (DB) algorithm developed originally for retrieving (3) over desert/arid land (bright in the visible). Here, we focus on DT-ocean and DT-land (#1 and #2). We have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to ? 84) to increase poleward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season/location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence on the surface reflectance, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. At the same time, we quantified how "upstream" changes to instrument calibration, land/sea masking and cloud masking will also impact the statistics of global AOD, and affect Terra and Aqua differently. For Aqua, all changes will result in reduced global AOD (by 0.02) over ocean and increased AOD (by 0.02) over land, along with changes in spatial coverage. We compared preliminary data to surface-based sun photometer data, and show that C6 should improve upon C5. C6 will include a merged DT/DB product over semi-arid land surfaces for reduced-gap coverage and better visualization, and new information about clouds in the aerosol field. Responding to the needs of the air quality community, in addition to the standard 10 km product, C6 will include a global (DT-land and DT-ocean) aerosol product at 3 km resolution.

Levy, R. C.; Mattoo, S.; Munchak, L. A.; Remer, L. A.; Sayer, A. M.; Patadia, F.; Hsu, N. C.

2013-11-01

52

The Collection 6 MODIS aerosol products over land and ocean  

NASA Astrophysics Data System (ADS)

The twin Moderate Imaging resolution Spectroradiometer (MODIS) sensors have been flying on Terra since 2000 and Aqua since 2002, creating an incredible dataset of global Earth observations. Here, we introduce the Collection 6 (C6) algorithm to retrieve aerosol optical depth (AOD) and aerosol size parameters from MODIS-observed spectral reflectance. While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there is significant impact on the products and their interpretation. The C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties (1) over ocean (dark in visible and near-IR wavelengths), (2) over vegetated/dark-soiled land (dark in the visible) and (3) over desert/arid land (bright in the visible). Here, we focus on the changes to both "dark target" algorithms (#1 and #2; DT-ocean and DT-land). Affecting both DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, and relaxed the solar zenith angle limit (up to ? 84) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season/location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. All together, the changes to the DT algorithms result in reduced global AOD (by 0.02) over ocean and increased AOD (by 0.01) over land, along with some changes in spatial coverage. Preliminary validation shows that compared to surface-based sunphotometer data, the C6 DT-products should compare at least as well as those from C5. However, at the same time as we have introduced algorithm changes, we have also been accounting for such "upstream" changes including new instrument calibration, revised land/sea masking and changed cloud masking that has resulted in changes to the coverage and global statistics of the retrieved AOD. To satisfy users' desires for more complete global aerosol coverage, C6 will include a merged DT/DB product over semi-arid land surfaces. In addition to changes to aerosol retrieval, C6 will include diagnostic information about clouds in the aerosol field, such as an aerosol "cloud mask" at 500 m resolution, and products that describe the "distance to the nearest cloud" from clear pixels. Finally, responding to the needs of the air quality community, in addition to the standard 10 km product, C6 will include a global (DT-land and DT-ocean) aerosol product at 3 km resolution.

Levy, R. C.; Mattoo, S.; Munchak, L. A.; Remer, L. A.; Sayer, A. M.; Hsu, N. C.

2013-01-01

53

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

54

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

NASA Astrophysics Data System (ADS)

The chemical composition of organic aerosols in the atmosphere is strongly influenced by human emissions. 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 have addressed 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 semiquantitative 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.

2014-09-01

55

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 m 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

56

Photoacoustic Optical Properties at UV, VIS, and near IR Wavelengths for Laboratory Generated and Winter Time Ambient Urban Aerosols  

NASA Technical Reports Server (NTRS)

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 micrometers and 10 micrometers, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). 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, M.; Arnott, W. P.; Zaveri, R. A.; Song, C.; Moosmuller, H.; Liu, L.; Mishchenko, M. I.; Chen, L.-W.A.; Green, M. C.; Watson, J. G.; Chow, J. C.

2012-01-01

57

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

58

Chemical characteristics of ambient aerosols contributed by cooking process at Noorpur village near New Delhi  

NASA Astrophysics Data System (ADS)

Generally, industrial and transport sectors are considered as major contributors of air pollution but recently, biomass burning is also reported as a major source of atmospheric aerosols (1, 2) especially in the developing world where solid fuels such as dung cake, wood and crop residues are used in traditional cooking which are responsible for poor air quality, respiratory problems and radiative forcing etc .In India, most of the research has been focused on emission estimates from biomass burning and cooking. No effort has been made to understand the chemistry and sources of fine aerosols in rural areas during cooking hours. This study fills this knowledge gap and strengthens our understanding about abundance of various chemical constituents of atmospheric aerosols emitted during cooking hours.Aerosol samples were collected from village called Noorpur (28.470 N, 77.030 E) which lies near Delhi city. 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 aerosol samples were collected on 8 hourly basis at a flow rate of 1 LPM. Water extracts of these filters were analyzed for major anions (F-, Cl-, NO3-, SO42-) and major cations (Na+, NH4+, K+, Ca2+ Mg2+) by ion chromatography (Metrohm 883 Basic IC Plus). During cooking period, the concentration of the major ions followed the order of Ca2+> SO42-> NO3-> Cl-> K+> NH4+> Mg2+> Na2+> F-. Among anion SO42 (5 g/m3) showed highest value and in case of cations Ca2+ (7.32g/m3) has highest value.

Singh, Sudha

59

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

60

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...

61

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

62

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

EPA Science Inventory

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

63

SOURCE APPORTIONMENT METHODS APPLIED TO THE DETERMINATION OF THE ORIGIN OF AMBIENT AEROSOLS THAT AFFECT VISIBILITY IN FORESTED AREAS  

EPA Science Inventory

An aerosol characterization, visibility, and receptor modeling study was conducted in the Shenandoah Valley, VA between July 14 and August 15, 1980. The objectives of this study were to: (1) determine the origin of the ambient particles, (2) determine the major chemical species c...

64

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 0.750.13 and the average organic density was 1.270.21 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 (0.730.07 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

65

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...

66

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

NASA Astrophysics Data System (ADS)

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 overall average concentrations of 30 and 36 ng m-3 were observed at the rural and urban sites, respectively. By combining the analysed meteorological data, backward trajectories, fire counts and Aerosol Index from the Earth Probe satellite, southwest China and the northern Philippines, together with the southeast China coast, were identified for the first time as source regions of the transported biomass burning particles at the surface level in rural Hong Kong. Occasional levoglucosan enhancements observed at urban Hong Kong were attributed to local incense and joss paper burning during the Ching-Ming festival period. The contributions of transported biomass burning emissions, especially from the northern Philippines, were estimated to account for 7.5% and 2.9% of OC and PM2.5, respectively.

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

2011-02-01

67

COLLECTION, CHEMICAL FRACTIONATION, AND MUTAGENICITY BIOASSAY OF AMBIENT AIR PARTICULATE  

EPA Science Inventory

The influence of industrialization and consequent increased concentration of urban particulate matter on the incidence of cancer has long been a concern. The first bioassays used to evaluate complex ambient air samples were whole-animal carcinogenesis bioassays. In these studies,...

68

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

NASA Astrophysics Data System (ADS)

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 downtown Los Angeles (CA), where 3 diesel trucks were tested. In Wilmington, the p-PAH, surface area, particle number, and "black" carbon concentrations were 4-8 times higher at 09:00-11:00 a.m. than between 17:00 and 18:00 p.m., suggesting that during rush hour traffic people living in that area are exposed to a higher number of diesel combustion particles enriched in p-PAH coatings. Dynamometer tests revealed that the p-PAH emissions from the "baseline" truck (no catalytic converter) were up to 200 times higher than those from the 2 vehicles equipped with advanced emission control technologies, and increased when the truck was accelerating. In Wilmington, integrated filter samples were collected and analyzed to determine the concentrations of the most abundant p-PAHs. A correlation between the total p-PAH concentration (?g/m3) and the measured photo-electric aerosol sensor signal (fA) was also established. Estimated ambient p-PAH concentrations (Average=0.64 ng/m3; Standard deviation=0.46 ng/m3 were in good agreement with those reported in previous studies conducted in Los Angeles during a similar time period. Finally, we calculated the approximate theoretical lifetime (70 years per 24-h/day) lung-cancer risk in the Wilmington area due to inhalation of multi-component p-PAHs and "black" carbon. Our results indicate that the lung-cancer risk is highest during rush hour traffic and lowest in the afternoon, and that the genotoxic risk of the considered p-PAHs does not seem to contribute to a significant part of the total lung-cancer risk attributable to "black" carbon.

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

2008-03-01

69

Molecular markers in ambient aerosol in the Mahanadi Riverside Basin of eastern central India during winter.  

PubMed

Organic molecular markers are important atmospheric constituents. Their formation and sources are important aspects of the study of urban and rural air quality. We collected PM10 aerosol samples from the Mahanadi Riverside Basin (MRB), a rural part of eastern central India, during the winter of 2011. PM10 aerosols were characterized for molecular markers using ion chromatography. The concentration of PM10 ranged from 208.8 to 588.3?gm(-3) with a mean concentration of 388.9?gm(-3). Total concentration of anhydrosugars, sugar alcohols, primary sugars, and oxalate were found to be 3.25, 5.60, 10.52, and 0.37?gm(-3), respectively, during the study period. Glucose was the most abundant species followed by levoglucosan and mannitol. Significant positive correlation between the molecular markers, anhydrosugars, sugar alcohols, primary sugars, and oxalic acid confirmed that biomass burning, biogenic activity, and re-suspension of soil particles were the main sources of aerosol in the eastern central India study area. PMID:25131681

Nirmalkar, Jayant; Deb, Manas K; Deshmukh, Dhananjay K; Tsai, Ying I; Verma, Santosh K

2015-01-01

70

Evidence and quantitation of aromatic organosulfates in ambient aerosols in Lahore, Pakistan  

NASA Astrophysics Data System (ADS)

Organosulfates are important components of atmospheric organic aerosols, yet their structures, abundances, sources and formation processes are not adequately understood. This study presents the identification and quantitation of benzyl sulfate in atmospheric aerosols, which is the first reported atmospheric organosulfate with aromatic carbon backbone. Benzyl sulfate was identified and quantified in fine particulate matter (PM2.5) collected in Lahore, Pakistan during 2007-2008. An authentic standard of benzyl sulfate was synthesized, standardized, and identified in atmospheric aerosols using ultra-performance liquid chromatography (UPLC) coupled with quadrupole time-of-flight (Q-ToF) mass spectrometry (MS). Benzyl sulfate was quantified in aerosol samples using UPLC coupled to negative electrospray ionization triple quadrupole (TQ) MS. The highest benzyl sulfate concentrations were recorded in November and January 2007 (0.50 0.11 ng m-3) whereas the lowest concentration was observed in July (0.05 0.02 ng m-3). To evaluate matrix effects, benzyl sulfate concentrations were determined using external calibration and the method of standard addition; comparable concentrations were detected by the two methods, which ruled out significant matrix effects in benzyl sulfate quantitation. Three additional organosulfates with m/z 187, 201 and 215 were qualitatively identified as aromatic organosulfates with additional methyl substituents by high-resolution mass measurements and tandem MS. The observed aromatic organosulfates form a homologous series analogous to toluene, xylene, and trimethylbenzene, which are abundant anthropogenic volatile organic compounds (VOC), suggesting that aromatic organosulfates may be formed by secondary reactions. Further studies are needed to elucidate the sources and formation pathways of aromatic organosulfates in the atmosphere.

Kundu, S.; Quraishi, T. A.; Yu, G.; Suarez, C.; Keutsch, F. N.; Stone, E. A.

2012-12-01

71

Evidence and quantitation of aromatic organosulfates in ambient aerosols in Lahore, Pakistan  

NASA Astrophysics Data System (ADS)

Organosulfates are important components of atmospheric organic aerosols, yet their structures, abundances, sources and formation processes are not adequately understood. This study presents the identification and quantitation of benzyl sulfate in atmospheric aerosols, which is the first confirmed atmospheric organosulfate with aromatic carbon backbone. Benzyl sulfate was identified and quantified in fine particulate matter (PM2.5) collected in Lahore, Pakistan, during 2007-2008. An authentic standard of benzyl sulfate was synthesized, standardized, and identified in atmospheric aerosols with quadrupole time-of-flight (Q-ToF) mass spectrometry (MS). Benzyl sulfate was quantified in aerosol samples using ultra performance liquid chromatography (UPLC) coupled to negative electrospray ionization triple quadrupole (TQ) MS. The highest benzyl sulfate concentrations were recorded in November and January 2007 (0.50 0.11 ng m-3) whereas the lowest concentration was observed in July (0.05 0.02 ng m-3). To evaluate matrix effects, benzyl sulfate concentrations were determined using external calibration and the method of standard addition; comparable concentrations were detected by the two methods, which ruled out significant matrix effects in benzyl sulfate quantitation. Three additional organosulfates with m/z 187, 201 and 215 were qualitatively identified as aromatic organosulfates with additional methyl substituents by high-resolution mass measurements and tandem MS. The observed aromatic organosulfates form a homologous series analogous to toluene, xylene, and trimethylbenzene, which are abundant anthropogenic volatile organic compounds (VOC), suggesting that aromatic organosulfates may be formed by secondary reactions. However, stronger statistical correlations of benzyl sulfate with combustion tracers (EC and levoglucosan) than with secondary tracers (SO42- and ?-pinene-derived nitrooxy organosulfates) suggest that aromatic organosulfates may be emitted from the combustion sources or their subsequent atmospheric processing. Further studies are needed to elucidate the sources and formation pathways of aromatic organosulfates in the atmosphere.

Kundu, S.; Quraishi, T. A.; Yu, G.; Suarez, C.; Keutsch, F. N.; Stone, E. A.

2013-05-01

72

The application of size- resolved hygroscopicity measurements to understand the physical and chemical properties of ambient aerosol  

E-print Network

&M University Chair of Advisory Committee: Dr. Don R. Collins During the summer of 2002, a modified tandem differential mobility analyzer (TDMA) was used to examine the size-resolved hydration state of the ambient aerosol in Southeast Texas. Although... Monterey, California. These were used to examine the change in soluble mass after the aerosol had been processed by cloud. The calculated change in soluble mass after cloud-processing ranged from 0.66 g m-3 to 1.40 g m-3. Model calculations showed...

Santarpia, Joshua Lee

2005-08-29

73

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...

74

Aerosol extinction measurements with a new multipass aerosol differential optical absorption spectrometer (A-DOAS): Laboratory validation and initial ambient measurements  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols directly affect climate by scattering and absorbing incident solar radiation. The magnitude of the impact is dependent upon the wavelength of incoming light, but is typically approximated near 550 nm. As a result, climate models can have large uncertainties for aerosol contributions when considering the solar spectrum. An aerosol differential optical absorption spectrometer (A-DOAS) has been developed to address to measure aerosol extinction from mid-ultraviolet to near infrared. The instrument consists of a closed UV-Vis spectrometer coupled to a White-type multi-pass gas cell with an adjustable path length of up to 20 meters. Laboratory extinction measurements of polystyrene latex spheres, nigrosin dye, and carbon black are compared with theory to validate the new instrument. Further, the lower limit of detection for the A-DOAS is shown to be less than 1x10-7 cm-1 . Finally, ambient aerosols under a variety of conditions were monitored and future work suggestions are made.

Chartier, Ryan T.

75

PCDD\\/Fs in ambient air collected in Zagreb, Croatia  

Microsoft Academic Search

Levels of PCDD\\/Fs were measured at four different sites in Zagreb, capital of Croatia. Also one sample was taken during spontaneously initiated open fire on a landfill and one sample where garden waste of unknown content was burnt. Over period 19972000, 28 samples were collected and levels ranged between 9 and 306fgI-TEQm?3, except in the sample collected during landfill fire.

B. Krauthacker; S. Herceg Romani?; M. Wilken; Z. Milanovi?

2006-01-01

76

High-Resolution Electrospray Ionization Mass Spectrometry Analysis of Water- Soluble Organic Aerosols Collected with a Particle into Liquid Sampler  

SciTech Connect

This work demonstrates the utility of a particle-into-liquid sampler (PILS) a technique traditionally used for identification of inorganic ions present in ambient or laboratory aerosols for the analysis of water soluble organic aerosol (OA) using high resolution electrospray ionization mass spectrometry (HR ESI-MS). Secondary organic aerosol (SOA) was produced from 0.5 ppm mixing ratios of limonene and ozone in a 5 m3 Teflon chamber. SOA was collected simultaneously using a traditional filter sampler and a PILS. The filter samples were later extracted with either water or acetonitrile, while the aqueous PILS samples were analyzed directly. In terms of peak intensities, types of detectable compounds, average O:C ratios, and organic mass to organic carbon ratios, the resulting high resolution mass spectra were essentially identical for the PILS and filter based samples. SOA compounds extracted from both filter/acetonitrile extraction and PILS/water extraction accounted for >95% of the total ion current in ESI mass spectra. This similarity was attributed to high solubility of limonene SOA in water. In contrast, significant differences in detected ions and peak abundances were observed for pine needle biomass burning organic aerosol (BBOA) collected with PILS and filter sampling. The water soluble fraction of BBOA is considerably smaller than for SOA, and a number of unique peaks were detectable only by the filter/acetonitrile method. The combination of PILS collection with HR-ESI-MS analysis offers a new approach for molecular analysis of the water-soluble organic fraction in biogenic SOA, aged photochemical smog, and BBOA.

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

2010-10-01

77

First Measurements of Particle-to-Particle Variations in Single Scattering Albedo of Ambient Aerosol and Arizona Test Dust  

NASA Astrophysics Data System (ADS)

The Aerosol Scattering To Extinction Ratio (ASTER) instrument is the first instrument to measure the single scattering albedo (SSA) of individual aerosol particles. ASTER also measures particle size using a combination of forward, backward, and total scattered light signals. Previous measurements of indoor air made by ASTER showed that bulk SSA measurements less than unity were the result of a small number of highly absorbing particles mixed with purely scattering particles, rather than a homogenous mixture of slightly absorbing particles. We present the first ambient measurements made with ASTER, aimed at determining how common a mode of highly absorbing particles is in ambient aerosol. The measurement site in Boulder, CO allowed for measurement of both urban influenced and relatively clean continental background air, depending on wind direction. The observed SSAs and optical sizes of aerosol particles measured during this field deployment will be discussed. We also present measurements of the SSA and scattering properties of individual Arizona test dust particles and explore the impact of non-sphericity on the signals.

Murphy, S. M.; Murphy, D. M.; Sanford, T. J.

2009-12-01

78

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

79

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

80

Analysis of the ambient VOC data collected in the Southern California air quality study. Final report  

SciTech Connect

A detailed analysis of ambient hydrocarbon and carbonyl data collected in the Southern California Air Quality Study (SCAQS) was undertaken to develop an improved understanding of nonmethane organic compounds (NMOC) in California's South Coast Air Basin (SoCAB). The SCAQS data set, which was the most extensive ever collected in the SoCAB, was used to: (1) Characterize the spatial and temporal patterns of total NMOC concentrations and NMOC/NOx ratios; (2) Characterize the spatial and temporal patterns of individual organic compounds; (3) Assess the consistency between ambient and emissions inventory NMOC; and (4) Assess the extent of NMOC oxidation and carbonyl compound formation occurring in the atmosphere.

Lurmann, F.W.; Main, H.H.

1992-02-01

81

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.

Kertsz, Zs; Borbly-Kiss, I.; Rajta, I.; Uzonyi, I.; Kiss, . Z.

2000-03-01

82

Human health benefits of ambient sulfate aerosol reductions under Title IV of the 1990 Clean Air Act amendments  

SciTech Connect

The Acid Rain Provisions (Title IV) of the Clean Air Act Amendments of 1990 call for about a 10 million ton reduction in annual SO{sub 2} emissions in the United States by the year 2010. Although the provisions apply nationwide, most of the reduction will take place in the eastern half of the United States, where use of high sulfur coal for electricity generation is most common. One potentially large benefit of Title IV is the expected reduction in adverse human health effects associated with exposure to ambient sulfate aerosols, a secondary pollutant formed in the atmosphere when SO{sub 2} is present. Sulfate aerosols are a significant constituent of fine particulate (PM{sub 2.5}). This paper combines available epidemiologic evidence of health effects associated with sulfate aerosols and economic estimates of willingness to pay for reductions in risks or incidence of health effects with available estimates of the difference between expected ambient sulfate concentrations in the eastern United States and southeastern Canada with and without Title IV to estimate the expected health benefits of Title IV. The results suggest a mean annual benefit in the eastern United States of $10.6 billion (in 1994 dollars) in 1997 and $40.0 billion in 2010, with an additional $1 billion benefit each year in Ontario and Quebec provinces.

Chestnut, L.G. [Hagler Bailly Consulting, Inc., Boulder, CO (United States); Watkins, A.M. [Environmental Protection Agency, Washington, DC (United States)

1997-12-31

83

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

EPA Science Inventory

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

84

Analysis of secondary organic aerosol compounds from the photooxidation of d-limonene in the presence of NOx and their detection in ambient PM2.5.  

PubMed

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 samples were solvent extracted and derivatized using analytical techniques that characterize functional groups contained in the compound: BF3-methanol derivatization was used for carboxylic groups, BSTFA for acidic and nonacidic hydroxyl groups, and PFBHA for ketone and aldehyde groups. The resulting derivative compounds were analyzed by GC-MS in the methane Cl and El modes. GC-MS analysis showed the occurrence of 103 oxygenated organic compounds in the filter extracts, 28 of which were identified. The major components include five tracer compounds previously identified from the photooxidation of alpha-pinene/NOx or beta-pinene/NOx systems, C4-C6 linear dicarboxylic acids, ketolimononaldehyde, limonic acid, and ketolimonic acid. Time profiles, yields, and proposed reaction schemes are provided for selected compounds. The laboratory SOA yield was 0.51 at a SOA concentration of 1470 microg m(-3). To determine the contributions of SOA products from d-limonene to ambient PM2.5, an analysis was performed for eight ambient PM2.5 samples collected in the southeastern United States in summer 2003. GC-MS analysis showed the occurrence of 21 d-limonene SOA compounds, indicating the impact of d-limonene on the regional aerosol burden. Based on our analysis, two compounds (nos. 55 and 69), not observed from the photooxidation of alpha-pinene or beta-pinene, are candidate tracers for d-limonene in atmospheric particulate matter. PMID:16830548

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

2006-06-15

85

First Field Deployments of an Aerodyne AMS Using Lithium Ion Attachment Ionization to Characterize Ambient Organic Aerosol Particles  

NASA Astrophysics Data System (ADS)

The Aerodyne Aerosol Mass Spectrometer (AMS) is a widely used instrument to determine the size-resolved chemical composition of nonrefractory aerosol particles. In the standard AMS, particles are flash vaporized and ionized by standard 70 eV electron impact. This `hard' ionization of organic molecules results in extensive fragmentation and makes it difficult to determine the molecular composition of complex mixtures. Previous AMS studies have been limited to classifying organics in broad categories such as "oxidized" and "hydrocarbon-like". Here we present results from the first field deployments of the Aerodyne AMS with a lithium ion (6Li+) attachment ionization source. The ionizer geometry (modified cross beam ionizer) is similar to that used in the standard electron impact version of the instrument with the Li+ source attached to the bottom of the original AMS ionizer cage. This setup enables the potential application of both ionization techniques. The Li ion attachment ionization scheme was successfully employed during the MCMA-2006/MILAGRO field campaign in Mexico City and the FLAME chamber study on wood burning in Missoula, Montana. Data from Mexico City show enough sensitivity to measure ambient aerosol particles with a time resolution of several minutes. Different mass spectra were observed, indicating aerosol particles from various sources. The biomass burning study results showed distinct mass spectra (i.e. molecular markers) for burns of different wood types. In particular, levoglucosan was observed and quantified. The amount of generated levoglucosan varied greatly for different biomass fuel types. The identification and quantification of specific molecular markers by Li ion attachment and a comparison with other techniques will be presented for both studies. The results obtained from these initial field deployments represent the successful application of Li ion attachment in the Aerodyne AMS, providing a new `soft' ionization method for the characterization of ambient organic particles.

Trimborn, A.; Jayne, J.; Northway, M.; Onasch, T.; Akiama, K.; Worsnop, D.

2006-12-01

86

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

PubMed

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

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

2013-04-01

87

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

88

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...

89

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

90

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

91

Ambient sulfate aerosol deposition in man: modeling the influence of hygroscopicity.  

PubMed Central

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 and its regional distribution must be determined. The mass median aerodynamic diameter of the inhaled aerosol will influence the sites of deposition in the respiratory tract. Atmospheric sulfate aerosols are hygroscopic and will have changing particle sizes and densities as they absorb water vapor in the humid environment of the human respiratory tract. Experimental and theoretical data that describe particle size as a function of temperature and relative humidity were used in computer subroutines of an aerosol deposition model in order to calculate the dose dispersion of H2SO4, (NH4)2SO4, and NH4HSO4 aerosols in man. Different temperature and relative humidity environments that approximately correspond to nasal and oral breathing were studied. The predicted deposition patterns are very different from those of nonhygroscopic aerosols with identical inhaled mass median aerodynamic diameter values. PMID:4076076

Martonen, T B; Barnett, A E; Miller, F J

1985-01-01

92

Single particle characterization, source apportionment, and aging effects of ambient aerosols in Southern California  

E-print Network

Metal-rich ambient particles (particulate matter(2.5)) cause airway inflammation in healthy subjects, American Journal of Respiratory and Critical Care Medicine,Metal-rich ambient particles (Particulate Matter(2.5)) cause airway inflammation in healthy subjects, American Journal of Respiratory and Critical Care Medicine,

Shields, Laura Grace

2008-01-01

93

952 IEEE SENSORS JOURNAL, VOL. 10, NO. 5, MAY 2010 Collection of Gaseous and Aerosolized Samples  

E-print Network

and separate multiple analytes at a time. Both structures were tested with ammonia as a gaseous sample and Kool Using Microfluidic Devices With Gas­Liquid Interfaces Jason D. Greenwood, Ye Liu, Student Member, IEEE methods for collecting gaseous samples and aerosolized particles into microfluidic channels. Gas

Jiang, Hongrui

94

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

95

Application of Pixe Analysis to Urban Aerosol Samples Collected on Whatman 41 Filters  

Microsoft Academic Search

The applicability of the Proton Induced X-Ray Emission (PIXE) technique to multi-elemental analysis of PM10 aerosol samples collected on Whatman 41 cellulose fibrous filters is investigated using concurrent samples collected on teflon membrane filters as references. The elemental levels measured on the two types of filter samples are highly correlated and the ratio of the elemental levels is related to

Y. C. Chan; G. H. McTainsh; P. D. Vowles; R. W. Simpson; D. D. Cohen; G. M. Bailey

1997-01-01

96

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

97

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 samplers 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

98

Design of an ambient aerosol sampling system for high and medium speed applications  

E-print Network

of COV is not acceptable in the wind tunnel used for aerosol testing. In order to reduce the COV an industrial gas blender (AirBlender, Model ABG 34 C8F-AL, Blender Products, Denver, CO) was installed downsheam of the plenum chamber to improve...

Irshad, Hammad

2012-06-07

99

Ambient particle characterization by single particle aerosol mass spectrometry in an urban area of Beijing  

NASA Astrophysics Data System (ADS)

To investigate the composition and possible sources of aerosol particles in Beijing urban area, a single particle aerosol mass spectrometer (SPAMS) was deployed from April 22 to May 4, 2011. 510,341 particles out of 2,953,200 sized particles were characterized by SPAMS in combination with the ART-2a neural network algorithm. The particles were classified as rich-K (39.79%), carbonaceous species (32.7%), industry metal (19.2%), dust (5.7%), and rich-Na (1.76%). Industrial emissions related particles, rich-Fe, rich-Pb, and K-nitrate, were the major components of aerosol particles during haze periods, which were mainly from the steel plants and metal smelting processes around Beijing. Under stagnant meterological conditions, these regional emissions have a vital effect on haze formation. Organic carbon (OC) particles were attributed to biomass burning. NaK-EC was likely to come from local traffic emissions. Internally mixed organic and elemental carbon (OCEC) was found to be from possible sources of local traffic emission and biomass burning. It was found that coarse dust particles were mainly composed of four different types of dust particles, dust-Si, dust-Ca, dust-Al, and dust-Ti. It is the first time that SPAMS was used to study a dust storm in Beijing. Our results showed that SPAMS could be a powerful tool in the identification and apportionment of aerosol sources in Beijing, providing useful reference information for environmental control and management.

Li, Lei; Li, Mei; Huang, Zhengxu; Gao, Wei; Nian, Huiqing; Fu, Zhong; Gao, Jian; Chai, Fahe; Zhou, Zhen

2014-09-01

100

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...

101

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 ...

102

Analysis of allergens in ambient aerosols: Comparison of areas subjected to different levels of air pollution  

Microsoft Academic Search

Recent studies describe interactions of pollen surfaces with aerosol particles; pollen surfaces undergo morphological changes and the release of allergens and allergenic fragments from the pollen can be enhanced. Thus allergens from pollen can be found in particle size fractions much smaller than undamaged pollen (?m). This may explain allergic reactions in parts of the lungs which cannot be reached

Georg F. Schppi; Christian Monn; Brunello Wthrich; Hans-Urs Wanner

1996-01-01

103

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...

104

Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory: a case study with long range transported biomass burning plumes  

NASA Astrophysics Data System (ADS)

Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m a.m.s.l. on Pico Island of the Azores archipelago in the North Atlantic. The observatory (3828'15'' N; 2824'14'' W) is located ∼3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances, mainly from North America. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon and inorganic ion species. The average ambient concentration of aerosol was 0.9 ?g m-3; on average organic aerosol contributes the majority of mass (57%), followed by sulfate (21%) and nitrate (17%). Filter-collected aerosol measurements were positively correlated (with an r2 ? 0.80) with continuous aerosol measurements of black carbon, aerosol light scattering and number concentration. Water-soluble organic carbon (WSOC) species extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. FLEXPART retroplume analysis shows the sampled air masses were very aged (average plume age > 12 days). Approximately 4000 molecular formulas were assigned to each of the mass spectra in the range of m/z 100-1000. The majority of the assigned molecular formulas have unsaturated structures with CHO and CHNO elemental compositions. These aged WSOC compounds have an average O / C ratio of ∼0.45, which is relatively low compared to O / C ratios of other aged aerosol and might be the result of evaporation and increased fragmentation during long-range transport. The increase in aerosol loading during the measurement period of 9/24 was linked to biomass burning emissions from North America by FLEXPART retroplume analysis and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts. This was confirmed with biomass burning markers detected in WSOC species and with the morphology and mixing state of particles as determined by scanning electron microscopy. The presence of markers characteristic of aqueous-phase reactions of biomass burning phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses on 9/25 were more aged (∼15 days) and influenced by marine emissions, as indicated by organosulfates and other species characteristic for marine aerosol such as fatty acids. The change in air masses for the two samples was corroborated by the changes in ozone and the non-methane hydrocarbons ethane and propane, morphology of particles, as well as by the FLEXPART retroplume simulations. This manuscript presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location in the North Atlantic.

Dzepina, K.; Mazzoleni, C.; Fialho, P.; China, S.; Zhang, B.; Owen, R. C.; Helmig, D.; Hueber, J.; Kumar, S.; Perlinger, J. A.; Kramer, L.; Dziobak, M. P.; Ampadu, M. T.; Olsen, S.; Wuebbles, D. J.; Mazzoleni, L. R.

2014-09-01

105

Direct measurement of the impact of the reactive uptake of ammonia and alkylamines on the CCN activity of ambient aerosol sampled during SOAS 2013  

NASA Astrophysics Data System (ADS)

The neutralization of condensed-phase organic acids via reaction with gas-phase ammonia or alkylamines to form ammonium and amminium salts, respectively, has been shown to change the supersaturated hygroscopicity (CCN activity) of laboratory generated organic aerosol (1). Understanding the extent to which CCN activity is perturbed by the reactive uptake of reduced nitrogen gases permits us to assess the sensitivity of current models of hygroscopicity to future changes in the concentration of ammonia and alkylamines. Data presented will focus on the measurement of ambient aerosol CCN activity during the 2013 Southern Oxidant and Aerosol Study (SOAS) campaign at Look Rock, TN, as well as changes in CCN activity following the reactive uptake of gas-phase methylamine, dimethylamine, and ammonia. Ambient CCN measurements are compared with literature values from laboratory studies focusing on SOA formed via isoprene oxidation. Implications for the effect of these multi-phase reactions on the cloud formation properties of ambient aerosols and the comparison of field measurements with laboratory-based studies of model compounds will be discussed. References: 1. Dinar, E. et al., CCN Activity and Hygroscopic growth of organic aerosols following reactive uptake of ammonia, Environ. Sci. Technol., 42, 793-799, 2008.

Zimmermann, K.; Ryder, O. S.; Corrigan, A. L.; Guzman, J. M.; Russell, L. M.; Budisulistiorini, S.; Surratt, J. D.; Zhang, X.; Cappa, C. D.; Bairai, S. T.; Hicks, W.; Renfro, J.; Brady, J.; Schill, S.; Bertram, T. H.

2013-12-01

106

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

107

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

108

Analysis of allergens in ambient aerosols: Comparison of areas subjected to different levels of air pollution  

Microsoft Academic Search

Recent studies describe interactions of pollen surfaces with aerosol particles; pollen surfaces undergo morphological changes\\u000a and the release of allergens and allergenic fragments from the pollen can be enhanced. Thus allergens from pollen can be found\\u000a in particle size fractions much smaller than undamaged pollen (<5 ?m). This may explain allergic reactions in parts of the\\u000a lungs which cannot be

Georg F. Schppi; Christian Monn; Brunello Wthrich; Hans-Urs Wanner

1996-01-01

109

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

110

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 m 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 m x 100 m of the alumina foils at a resolution of about 0.5 m. 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

111

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

112

Quantifying the sources of hazardous elements of suspended particulate matter aerosol collected in Yokohama, Japan  

NASA Astrophysics Data System (ADS)

We analyzed metals (Mg, Al, Ca, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb and Bi), water-soluble ions (Na +, NH 4+, K +, Ca 2+, Cl -, NO 3- and SO 42-) and carbonaceous mass (EC and OC) in SPM aerosol samples using an ICP-MS, ion chromatograph and CHN corder, respectively. The SPM samples were collected from 1999 to 2005 at two locations (urban site A and industrial site B) of Yokohama, Japan with concentrations in mean and ranges of 34.2 and 19.7-50.3 ?g m -3 and 22.9 and 12.7-35.1 ?g m -3 for the respective location. Source apportionment of SPM aerosol was conducted appropriately for the first time to these locations employing PCA-APCS technique. Major sources of SPM at site A were a) crustal source, b) urban origin, c) undefined, and d) mineral rock. At site B, the sources were predicted as a) urban origin, b) undefined, c) crustal source, and d) secondarily formed aerosol. The tracers and nature of the source related to urban origin at both sites were similar but retaining different source strength. Secondarily formed aerosol was quite unique at site B. However, mineral rock was remarkable at site A.

Khan, Md. Firoz; Hirano, Koichiro; Masunaga, Shigeki

2010-07-01

113

Mass loading of size-segregated atmospheric aerosols in the ambient air during fireworks episodes in eastern Central India.  

PubMed

The effects of combustion of the fire crackers on the air quality in eastern Central India were studied for the first time during Diwali festival. This case study analyzes the size distribution and temporal variation of aerosols collected in the rural area of eastern Central India during pre-diwali, Diwali and post-diwali period for the year of 2011. Fifteen aerosol samples were collected during the special case study of Diwali period using Andersen sampler. The mean concentrations of PM10 (respirable particulate matter) were found to be 212.8 4.2, 555.5 20.2 and 284.4 5.8 during pre-diwali, Diwali and post-diwali period, respectively. During Diwali festival PM10 concentration was about 2.6 and 1.9 times higher than pre-diwali and post-diwali period, respectively. PM2.5 (fine) and PM1 (submicron) concentrations during Diwali festival were more than 2 times higher than pre-diwali and post-diwali. PMID:23287842

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

2013-04-01

114

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

115

The chemical composition of fine ambient aerosol particles in the Beijing area  

NASA Astrophysics Data System (ADS)

The strong economical growth in China during the last few decades led to heavy air pollution caused by significantly increased particle emissions. The aerosol particles affect not only the regional air quality and visibility, but can also influence cloud formation processes and the radiative balance of the atmosphere by their optical and microphysical properties. The ability to act as Cloud Condensation Nuclei (CCN) is related to microphysical properties like the hygroscopic growth or the cloud droplet activation. The chemical composition of CCN plays an important role on these properties and varies strongly with the particle size and the time of day. Hygroscopic or surface active substances can increase the hygroscopicity and lower the surface tension of the particle liquid phase, respectively. The presence of such compounds may result in faster cloud droplet activation by faster water uptake. The DFG project HaChi (Haze in China) aimed at studying physical and chemical parameters of urban aerosol particles in the Beijing area in order to associate the chemical composition of aerosol particles with their ability to act as CCN. To this end, two measurement campaigns were performed at the Wuqing National Ordinary Meteorological Observing Station, which is a background site near Beijing. The winter campaign was realized in March 2009 and the summer campaign took place from mid July 2009 to mid August 2009. Fine particles with an aerodynamic diameter smaller than or equal 1 ?m were continuously sampled for 24h over the two campaigns using a DIGITEL high volume sampler (DHA-80). The present contribution presents and discusses the results of the chemical characterization of the DIGITEL filters samples. The filters were analyzed for the mass concentration, inorganic ions and carbon sum parameters like elemental (EC), organic (OC) and water soluble organic carbon (WSOC). The WSOC fraction was further characterized for hygroscopic substances like low molecular dicarboxylic acids as well as sugars and sugar related compounds. Additionally fatty acids were analyzed to investigate surface active substances. Usually, the highest PM1 concentrations were observed during periods with prevailing wind directions from southern areas, while northern wind directions led to significantly lower concentrations. The main components of the fine particles are inorganic ions like the secondary formed ammonium nitrate und ammonium sulphate, as well as carbonaceous material. The organic carbon fraction is mostly dominated by water soluble organic carbon (80% in average). High concentrations of tracers like the anhydrosugar levoglucosan (Iinuma et al., 2007) suggest biomass burning emissions as a dominant source of organic particles in the area. A significant fraction of PM1 remains unidentified and most likely consists of crust material like dust as well as water. Iinuma, Y., E. Brggemann, T. Gnauk, K. Mller, M. O. Andreae, G. Helas, R. Parmar, and H. Herrmann (2007), Source characterization of biomass burning particles: The combustion of selected European conifers, African hardwood, savanna grass, and German and Indonesian peat, J. Geophys. Res. [Atmos.], 112(D8), Doi 10.1029/2006jd007120.

Nekat, Bettina; van Pinxteren, Dominik; Iinuma, Yoshiteru; Gnauk, Thomas; Mller, Konrad; Herrmann, Hartmut

2010-05-01

116

Evidence of high PM 2.5 strong acidity in ammonia-rich atmosphere of Guangzhou, China: Transition in pathways of ambient ammonia to form aerosol ammonium at [NH 4+]/[SO 42-] = 1.5  

NASA Astrophysics Data System (ADS)

In this study, 24-h PM2.5 samples were collected using Harvard Honeycomb denuder/filter-pack system during different seasons in 2006 and 2007 at an urban site in Guangzhou, China. The particles collected in this study were generally acidic (average strong acidity ([H+]) ~ 70 nmol m- 3). Interestingly, aerosol sulfate was not fully neutralized in the ammonia-rich atmosphere (NH3 ~ 30 ppb) and even when NH4+]/[SO42-] was larger than 2. Consequently, strong acidity ([H+]) as high as 170 nmol m- 3 was observed in these samples. The kinetic rate of neutralization of acidity (acidic sulfate) by ambient ammonia was significantly higher than the rate of formation of ammonium nitrate involving HNO3 and NH3 for [NH4+]/[SO42-] ? 1.5 and much lower for NH4+]/[SO42-] > 1.5. Therefore, higher nitrate principally formed via homogeneous gas phase reactions involving ammonia and nitric acid were observed for [NH4+]/[SO42-] > 1.5. However, little nitrate, probably formed via heterogeneous processes e.g. reaction of HNO3 with sea salt or crustal species, was observed for [NH4+]/[SO42-] ? 1.5. These demonstrate a clear transition in the pathways of ambient ammonia to form aerosol ammonium at [NH4+]/[SO42-] = 1.5 and evidently explain the observed high acidity due to the unneutralized sulfate in the ammonium-rich aerosol (NH4+]/[SO42-] > 1.5). In fact, the measured acidity was almost similar to the excess acid defined as the acid that remains at [NH4+]/[SO42-] = 1.5 due to the un-neutralized fraction of sulfate ([H+] = 0.5[SO42-]). The presence of high excess acid and ammonium nitrate significantly lowered the deliquescence relative humidity of ammonium sulfate (from 80% to 40%) in the ammonium-rich samples.

Huang, X.; Qiu, R.; Chan, Chak K.; Ravi Kant, Pathak

2011-03-01

117

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 ...

118

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 ...

119

Collection and characterization of aerosols from metal cutting techniques typically used in decommissioning nuclear facilities.  

PubMed

This study was designed to collect and characterize aerosols released during metal cutting activities typically used in decommissioning radioactively contaminated facilities. Such information can guide in the selection of appropriate control technologies for these airborne materials. Mechanical cutting tools evaluated included a multi-wheel pipe cutter, reciprocating saw, band saw, chop saw, and large and small grinding wheels. Melting-vaporization cutting techniques included an oxy-acetylene torch, electric arc cut rod and plasma torch. With the exception of the multi-wheel pipe cutter, all devices created aerosols in the respirable size range (less than 10 micron aerodynamic diameter). Time required to cut 2-in. (5-cm) Schedule 40, Type 304L, stainless steel ranged from about 0.6 min for the plasma torch to about 3.0 min for the reciprocating saw. Aerosol production rate ranged from less than 10 mg/min for the reciprocating saw to more than 3000 mg/min for the electric arc cut rod. Particles from mechanical tools were irregular in shape, whereas particles from vaporization tools were spheres and ultrafine branched-chain aggregates. PMID:3425551

Newton, G J; Hoover, M D; Barr, E B; Wong, B A; Ritter, P D

1987-11-01

120

Predicting ambient aerosol Thermal Optical Reflectance (TOR) measurements from infrared spectra: organic carbon  

NASA Astrophysics Data System (ADS)

Organic carbon (OC) can constitute 50% or more of the mass of atmospheric particulate matter. Typically, the organic carbon concentration is measured using thermal methods such as Thermal-Optical Reflectance (TOR) from quartz fiber filters. Here, methods are presented whereby Fourier Transform Infrared (FT-IR) absorbance spectra from polytetrafluoroethylene (PTFE or Teflon) filters are used to accurately predict TOR OC. Transmittance FT-IR analysis is rapid, inexpensive, and non-destructive to the PTFE filters. To develop and test the method, FT-IR absorbance spectra are obtained from 794 samples from seven Interagency Monitoring of PROtected Visual Environment (IMPROVE) sites sampled during 2011. Partial least squares regression is used to calibrate sample FT-IR absorbance spectra to artifact-corrected TOR OC. The FTIR spectra are divided into calibration and test sets by sampling site and date which leads to precise and accurate OC predictions by FT-IR as indicated by high coefficient of determination (R2; 0.96), low bias (0.02 ?g m-3, all ?g m-3 values based on the nominal IMPROVE sample volume of 32.8 m-3), low error (0.08 ?g m-3) and low normalized error (11%). These performance metrics can be achieved with various degrees of spectral pretreatment (e.g., including or excluding substrate contributions to the absorbances) and are comparable in precision and accuracy to collocated TOR measurements. FT-IR spectra are also divided into calibration and test sets by OC mass and by OM / OC which reflects the organic composition of the particulate matter and is obtained from organic functional group composition; this division also leads to precise and accurate OC predictions. Low OC concentrations have higher bias and normalized error due to TOR analytical errors and artifact correction errors, not due to the range of OC mass of the samples in the calibration set. However, samples with low OC mass can be used to predict samples with high OC mass indicating that the calibration is linear. Using samples in the calibration set that have a different OM / OC or ammonium / OC distributions than the test set leads to only a modest increase in bias and normalized error in the predicted samples. We conclude that FT-IR analysis with partial least squares regression is a robust method for accurately predicting TOR OC in IMPROVE network samples; providing complementary information to the organic functional group composition and organic aerosol mass estimated previously from the same set of sample spectra (Ruthenburg et al., 2014).

Dillner, A. M.; Takahama, S.

2014-11-01

121

AMBIENT AEROSOL CONCENTRATION BY CONDENSATION AND VIRTUAL IMPACTION FOR COLLECTION AND CHEMICAL ANALYSIS. (R825269)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

122

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...

123

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

124

Molecular Characterization of S- and N-containing Organic Constituents in Ambient Aerosols by negative ion mode High-Resolution Nanospray Desorption Electrospray Ionization Mass Spectrometry: CalNex 2010 field study  

SciTech Connect

Samples of ambient aerosols from the 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study were analyzed using Nanospray Desorption Electrospray Ionization High Resolution Mass Spectrometry (nano-DESI/MS). Four samples per day were collected in Bakersfield, CA on June 20-24 with a collection time of 6 hours per sample. Four characteristic groups of organic constituents were identified in the samples: compounds containing carbon, hydrogen, and oxygen only (CHO), sulfur- (CHOS), nitrogen-(CHON), and both nitrogen- and sulfur-containing organics (CHONS). Within the groups, organonitrates, organosulfates, and nitroxy organosulfates were assigned based on accurate mass measurements and elemental ratio comparisons. Changes in the chemical composition of the aerosol samples were observed throughout the day. The number of observed CHO compounds increased in the afternoon samples, suggesting regional photochemical processing as a source. The average number of CHOS compounds had the smallest changes throughout the day, consistent with a more broadly distributed source. Both of the nitrogen-containing groups (CHON and CHONS) had greater numbers of compounds in the night and morning samples, indicating that nitrate radical chemistry was likely a source for those compounds. Most of the compounds were found in submicron particles. The size distribution of CHON compounds was bimodal. We conclude that the majority of the compounds observed were secondary in nature with both biogenic and anthropogenic sources.

O'Brien, Rachel E.; Laskin, Alexander; Laskin, Julia; Rubitschun, Caitlin L.; Surratt, Jason D.; Goldstein, Allen H.

2014-11-19

125

PIXE analysis of size-fractionated aerosol samples collected at birkenes, Norway, during spring 1987  

NASA Astrophysics Data System (ADS)

A single orifice cascade impactor was used to collect size-fractionated aerosol samples in Birkenes, Southern Norway, during the spring of 1987. The samples were analyzed for about 20 elements by particle-induced X-ray emission (PIXE). On the basis of the average size distributions and mass median diameters (MMDs), the elements could be classified in three different groups. Mg, Al, Cl, Ca, Ti, and Fe exhibited a unimodal size distribution, with a MMD of about 4 ?m equivalent aerodynamic diameter (EAD); for Si, K, Cr, Mn, Ni, and Cu the distribution was rather flat or bimodal; and S, V, Br, Zn, and Pb were predominantly associated with < 1 ?m EAD particles. The elemental concentrations and aerosol composition (interelement ratios) were examined in relation to the origin of the sampled air masses, as determined from air mass back-trajectories, and substantial differences were observed. Certain samples exhibited enhanced concentrations of fine Si which probably originated from Si and SiC industries in Southern Norway. High crustal enrichment factors were observed for Mn in northern and northwestern air masses, suggesting contributions from Norwegian sources for this element.

Cornille, P.; Maenhaut, W.; Pacyna, J. M.

1990-04-01

126

COMPOSITION AND ORIGINS OF AEROSOL AT A FORESTED MOUNTAIN IN SOVIET GEORGIA  

EPA Science Inventory

Ambient aerosol particles were collected by means of dichotomous samplers during July, 1979, at Abastumani Astrophysical Observatory, which is in a remote forested area of Georgia, USSR. Samples were analyzed for mass, elemental, crystalline, and ionic species concentrations and ...

127

78 FR 57631 - Information Collection Request Submitted to OMB for Review and Approval; Comment Request; Ambient...  

Federal Register 2010, 2011, 2012, 2013

...EPA ICR No. 0940.27, OMB Control No. 2060-0084) to the Office of Management and...Nitrogen Oxides Ambient Monitoring ICR (OMB 2060-0638, EPA ICR Number 2358.03) and...Dioxides Ambient Monitoring ICR (OMB 2060-0642, EPA ICR Number...

2013-09-19

128

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...

129

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

130

Differences in the OC/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis  

EPA Science Inventory

Thermal-optical analysis (TOA) is typically used to measure the OC/EC (organic carbon/elemental carbon) and EC/TC (elemental carbon/total carbon) ratios in source and atmospheric aerosols. The present study utilizes a dual-optical carbon aerosol analyzer to examine the effects of...

131

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

132

Aerosols Collected at a Tropical Marine Environment: Size-Resolved Chemical Composition Using IC, TOC, and Thermal-Optical Analyses  

NASA Astrophysics Data System (ADS)

Size-resolved chemical characterization was performed on aerosol samples collected at two different marine sites in the tropics: Dian Point (DP), Antigua and Cape San Juan (CSJ), Puerto Rico. A 13-stage Dekati low- pressure impactor (Dp 0.1 to 10 ?m), a 10-stage micro-orifice uniform deposit impactor (Dp 0.054 to 18 ?m), and stacked-filter units (Dp < 1.7 ?m) were used to collect the samples. Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO2-, NO3-, SO42-, acetate, formate, malonate, and oxalate were determined using ion chromatography (IC). Thermal-optical analysis (TOA) was used to determine the concentrations of aerosol total carbon (TC), organic carbon (OC), and elemental carbon (EC). Five-day back trajectories calculated using NOAA's HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model identified air masses coming from the North Atlantic (maritime air), Northwest Africa (desert dust), and North America (anthropogenic pollution). Size-resolved chemical characterization of aerosol samples using IC and TOA confirmed that aerosols become aged as they are transported to the Caribbean and their composition depends on the air mass origin. Gravimetric analyses showed that average fine mass concentrations for CSJ station were higher than for DP station (CSJ: 1.9 ?g m-3; DP: 1.2 ?g m-3). The aerosol chemical composition changed with air masses of different origin and with different pollution levels. In both locations the predominant water-soluble ions in the fine aerosol fraction were Cl-, Na+, and SO42-. Sulphate was observed in higher concentrations during the polluted case and particulate organic matter concentrations were higher for the maritime case. During desert dust events an increase in Ca2+ and Mg2+ of 4 and 2 times, respectively, was observed mainly in the coarse mode. Results for the size-resolved chemical composition and complete aerosol chemical apportionment including the residual mass will be presented.

Morales-Garca, F.; Mayol-Bracero, O. L.; Repollet-Pedrosa, M.; Kasper-Giebl, A.; Ramrez-Santa Cruz, C.; Puxbaum, H.

2009-05-01

133

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

PubMed

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

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

2014-03-01

134

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...

135

Differences in the OC\\/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis  

Microsoft Academic Search

Different thermal-optical methods used to measure OC\\/EC and EC\\/TC ratios in atmospheric aerosols often produce significantly different results due to variations within the temperature programming and optical techniques of each method. To quantify the thermal and optical effects on these ratios, various source (residential cookstoves and diesel exhaust) and atmospheric (rural and urban) aerosols were analyzed using 3 thermal protocols:

Bernine Khan; Michael D. Hays; Chris Geron; James Jetter

2012-01-01

136

Contributions of modern and dead organic carbon to individual fatty acid homologues in spring aerosols collected from northern Japan  

NASA Astrophysics Data System (ADS)

Radiocarbon (14C) and stable carbon isotope ratios (?13C) have been used as proxies to evaluate the contributions of modern/fossil carbon and marine/terrestrial organic matter, respectively, in geochemical samples. However, there are few such studies in atmospheric aerosols. Here, we measured 14C contents and ?13C of individual n-fatty acids in an aerosol sample collected from northern Japan in spring 2001 during Asian dust season. Our results show that the distribution of fatty acids in the spring aerosols was characterized by a strong even/odd carbon number predominance with two maxima at C16 and C26. Their ?13C (range: -30.6 to -20.5) showed higher values (average: -24.5) for lower molecular weight (LMW) fatty acids (C16 - C19) and lower values (average: -29.7) for higher MW (HMW) fatty acids (C20 - C32). This difference suggests that LMW acids are mainly derived from lacustrine and/or marine algal sources whereas HMW acids are predominantly from terrestrial C3 higher plants. ?14C values of fatty acids were found to range from -96.9 to +122.9 with lower values for HMW acids and higher values for LMW acids. LMW acids in the aerosols contain only modern carbon. In contrast, HMW acids ?C24 were found to contain up to 9.7 wt% dead carbon, although their major portion (up to 92.3%) is composed of modern carbon. Backward trajectory analyses indicated that the source regions of the spring aerosols were dominated by central and north China (62%). This study suggests that the old fatty acids in the spring aerosols are most likely originated from the loess deposits in China via long-range atmospheric transport over the western North Pacific, although their contribution to the aerosols was relatively small.

Kawamura, Kimitaka; Matsumoto, Kohei; Uchida, Masao; Shibata, Yasuyuki

2010-11-01

137

Aerosol-Assisted Solid Debris Collection for the National Ignition Facility  

SciTech Connect

The National Ignition Facility (NIF) has been completed and has made its first shots on-target. While upcoming experiments will be focused on achieving ignition, a variety of subsequent experiments are planned for the facility, including measurement of cross sections, astrophysical measurements, and investigation of hydrodynamic instability in the target capsule. In order to successfully execute several of these planned experiments, the ability to collect solid debris following a NIF capsule shot will be required. The ability to collect and analyze solid debris generated in a shot at the National Ignition Facility (NIF) will greatly expand the number of nuclear reactions studied for diagnostic purposes. Currently, reactions are limited to only those producing noble gases for cryogenic collection and counting with the Radchem Apparatus for Gas Sampling (RAGS). The radchem solid collection diagnostic has already been identified by NIF to be valuable for the determination and understanding of mix generated in the target capsule's ablation. LLNL is currently developing this solid debris collection capability at NIF, and is in the stage of testing credible designs. Some of these designs explore the use of x-ray generated aerosols to assist in collection of solid debris. However, the variety of harsh experimental conditions this solid collection device will encounter in NIF are challenging to replicate. Experiments performed by Gary Grim et al. at Sandia National Laboratory's RHEPP1 facility have shown that ablation causes a cloud of material removed from an exposed surface to move normal to and away from the surface. This ablation is certain to be a concern in the NIF target chamber from the prompt x-rays, gamma rays, etc. generated in the shot. The cloud of ablated material could interfere with the collection of the desired reaction debris by slowing down the debris so that the kinetic energy is too low to allow implantation, or by stopping the debris from reaching the collection device entirely. Our goal is to use this primary ablation wave to our advantage, by the creation of ionized alkali metal halide salt aerosols. This technique is similar to that used by many particle accelerator groups for gas-jet transport. Ideally the salt would be ablated from a substrate, encounter the reaction debris, agglomerate, and be collected for further study. We have done studies at laser and pulsed-power facilities (Titan laser at LLNL, Trident laser at LANL, Zebra z-pinch at Nevada Terawatt Facility) evaluating the hardiness of materials for placement in the NIF target chamber, as well as testing aerosol generation by the incident x-rays generated in device shots. To test this method's potential success in the NIF environment, we have tested KCl, KI, RbI, and CsI films of 1 and 2 um linear thickness on aluminum and silicon wafer substrates in these aforementioned facilities, at varied distances. These salts do ablate in the presence of sufficient x-ray fluence. Further analysis to quantify the final ablation depth as a function of x-ray fluence is ongoing. Half of each sample was masked with a thick tungsten foil for photon opacity. KCl was the most difficult salt to ablate, from comparing the tungsten-masked side of the samples to the unmasked side of the samples. This is likely due to KCl's absorbance peak being at lower wavelengths than that of KI, {approx}160 nm vs. {approx}220 nm, respectively. Samples with and without collimation were tested to identify if any condensation of these ablated salts occurred after ablation. Visual inspection of the silicon wafer witness plates placed parallel to the direction of the incident photons showed that a vapor was deposited on the wafers next to the collimators. Further analysis with EDS in the case of the collimated samples conclusively identified the vapor as CsI. We also intend to examine samples of bare substrate exposed to the same experimental conditions for post-shot change via SEM images, optical microscopy, and atomic force microscopy (AFM). Furthermore, tests with separated isotopes

Nelson, S L; Shaughnessy, D A; Moody, K J; Ivanov, V V; Astanovitskiy, A L; Lewis, L A; Rundberg, R S

2010-05-21

138

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

139

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...

140

Retrieval of effective complex refractive index from intensive measurements of characteristics of ambient aerosols in the boundary layer.  

PubMed

Aerosol complex refractive index (ACRI) has attracted intensive attentions due to its significance in modeling aerosol radiative effects. Determinations of ACRI from surface measurements of aerosol scattering and absorption coefficients as well as number size distributions during June, 2008 based on an iterative Mie algorithm were performed. The aim of our study was to introduce an inversion approach with the merits of high time-resolutions to retrieve the optically effective ACRI, especially its imaginary part. Based on simultaneous measurements of aerosol characteristics, mean ACRI value of 1.50 ( 0.34)-i0.025 ( 0.015) at 550 nm in Hefei in summer was deducted. The lower imaginary parts with higher single scattering albedos and lower scattering Angstrom exponents were obtained for haze periods compared with nonhaze conditions with similar air-mass back-trajectories, indicating more large and scattering particles contributing to the formation of haze episodes. The derived imaginary parts of ACRI related to agricultural biomass burning were in the range from 0.013 to 0.029 at 550 nm. Significant negative correlations between retrieved imaginary parts of ACRI and measured single scattering albedos indicate that our retrieval approach is a reasonable method for determining the imaginary parts of complex refractive indices of aerosol particles. PMID:23938658

Zhang, Xiaolin; Huang, Yinbo; Rao, Ruizhong; Wang, Zhien

2013-07-29

141

Contrasting online MSn spectra of organic acids in ambient aerosol from the boreal forest at Hyytil, 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 Hyytil, Finland and during the INUIT campaign 2012 on Mt. Kleiner Feldberg, Germany. By merging APCI-IT-MS data with data from the Aerodyn 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 Hyytil are a strong hint for unidentified species. This can be supported by MSn observations, where the fragmentation pattern from Hyytil 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.; ijl, Mikko; Ehn, Mikael; Junninen, Heikki; Petj, Tuukka; Worsnop, Douglas R.; Kulmala, Markku; Williams, Jonathan; Schneider, Johannes; Hoffmann, Thorsten

2013-04-01

142

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

Microsoft Academic Search

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

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

2009-01-01

143

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

144

Aerosol and Plasma Measurements in Noctilucent Clouds  

NASA Technical Reports Server (NTRS)

The purpose of this project was to develop rocket-borne probes to detect charged aerosol layers in the mesosphere. These include sporadic E layers, which have their origin in meteoric dust, and noctilucent clouds, which form in the arctic summer and are composed of ice crystals. The probe being developed consists of a charge collecting patch connected to a sensitive electrometer which measures the charge deposited on the patch by impacting aerosols. The ambient electrons and light ions in the mesosphere are prevented from being collected by a magnetic field. The magnetic force causes these lighter particles to turn so that they miss the collecting patch.

Robertson, Scott

2000-01-01

145

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...

146

Correlations between absorption Angstrm 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 Angstrm 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, .; Pintr, M.; Trk, Zs.; Bozki, Z.; Szab, G.

2014-07-01

147

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...

148

Collaborative Environmental In Situ Data Collection: Experiences and Opportunities for Ambient Data Integration  

Microsoft Academic Search

\\u000a Collaborative environmental in situ data collection occurs when a team of investigators goes into the field together to collect\\u000a environmental data. These data might be necessary, e.g., for a biodiversity inventory, compilation of a soil density map,\\u000a or to estimate above-ground forest carbon stocks. Investigators will often arrive at a location and disperse, collecting data,\\u000a and then compiling it either

David Thau

2010-01-01

149

Quantitative ED-EPMA combined with morphological information for the characterization of individual aerosol particles collected in Incheon, Korea  

NASA Astrophysics Data System (ADS)

A quantitative single-particle analytical technique, called low- Z particle electron probe X-ray microanalysis, combined with the utilization of their morphological information on individual particles, was applied to characterize six aerosol samples collected in one Korean city, Incheon, during March 9-15, 2006. The collected supermicron aerosol particles were classified based on their chemical species and morphology on a single-particle basis. Many different particle types were identified and their emission source, transport, and reactivity in the air were elucidated. In the samples, particles in the "soil-derived particles" group were the most abundant, followed by "reacted sea-salts", "reacted CaCO 3-containing particles", "genuine sea-salts", "reacted sea-salts + others", "Fe-containing particles", "anthropogenic organics", (NH 4) 2SO 4, "K-containing particles", and "fly ash". The application of this single-particle analysis, fully utilizing their chemical compositional and morphological data of individual particles, clearly revealed the different characteristics of the six aerosol samples. For samples S3 and S5, which were sampled during two Asian dust storm events, almost all particles were of soil origin that had not experienced chemical modification and that did not entrain sea-salts during their long-range transport. For sample S1, collected at an episodic period of high PM 10 concentration and haze, anthropogenic, secondary, and soil-derived particles emitted from local sources were predominant. For samples S2, S4, and S6, which were collected on average spring days with respect to their PM 10 concentrations, marine originated particles were the most abundant. Sample S2 seems to have been strongly influenced by emissions from the Yellow Sea and Korean peninsula, sample S4 had the minimum anthropogenic influence among the four samples collected in the absence of any Asian dust storm event, and sample S6 seems to have entrained air pollutants that had been transported from mainland China over the Yellow Sea to Korea.

Kang, SuJin; Hwang, HeeJin; Kang, Sunni; Park, YooMyung; Kim, HyeKyeong; Ro, Chul-Un

150

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

151

EVALUATION OF SOLID ADSORBENTS FOR THE COLLECTION AND ANALYSES OF AMBIENT BIOGENIC VOLATILE ORGANICS  

EPA Science Inventory

Micrometeorological flux measurements of biogenic volatile organic compounds (BVOCs) usually require that large volumes of air be collected (whole air samples) or focused during the sampling process (cryogenic trapping or gas-solid partitioning on adsorbents) in order to achiev...

152

Molecular characterization of S- and N-containing organic constituents in ambient aerosols by negative ion mode high-resolution Nanospray Desorption Electrospray Ionization Mass Spectrometry: CalNex 2010 field study  

NASA Astrophysics Data System (ADS)

of ambient aerosols from the 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field study were analyzed using negative ion mode Nanospray Desorption Electrospray Ionization High-Resolution Mass Spectrometry (nano-DESI/MS). Four samples per day (6 h each) were collected in Bakersfield, CA on 20-24 June. Four characteristic groups were identified: molecules composed of carbon, hydrogen, and oxygen only (CHO), sulfur- (CHOS), nitrogen- (CHON), and both nitrogen- and sulfur-containing organics (CHONS). The chemical formula and elemental ratios were consistent with the presence of organonitrates, organosulfate, and nitroxy organosulfates in the negative ion mode mass spectra. The number of observed CHO compounds increased in the afternoon samples, suggesting photochemical processing as a source. The average number of CHOS compounds had the smallest changes during the day, consistent with a more broadly distributed source. Both of the nitrogen-containing groups (CHONS and CHON) had greater numbers of compounds in the early morning (midnight to 6 A.M.) and night (6 P.M. to midnight) samples, respectively, consistent with nitrate radical chemistry as a likely source for those compounds. Most of the compounds were found in submicron particles. The size distribution of the number of CHON compounds was bimodal, potentially indicating two types of sources. We conclude that the majority of the compounds observed were secondary in nature with both biogenic and anthropogenic sources. These data are complementary to previous results from positive ion mode nano-DESI/MS analysis of a subset of the same samples providing a more complete view of aerosol chemical composition at Bakersfield.

O'Brien, Rachel E.; Laskin, Alexander; Laskin, Julia; Rubitschun, Caitlin L.; Surratt, Jason D.; Goldstein, Allen H.

2014-11-01

153

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

154

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)...

155

Fine and coarse modes of dicarboxylic acids in the Arctic aerosols collected during the Polar Sunrise Experiment 1997  

NASA Astrophysics Data System (ADS)

Fine (<1 ?m) and coarse (>1 ?m) aerosol particles were collected at Alert, Canada (8227'N, 6230'W), during the Arctic spring as part of the Polar Sunrise Experiment 1997 and were analyzed for low molecular weight dicarboxylic acids (C2-C11) using gas chromatography with flame ionization detector (GC-FID) and GC/mass spectrometry (GC/MS). More than 80% of total diacids were detected in the fine fraction, suggesting the production by gas-to-particle conversion in the Arctic. In both fractions, oxalic acid was the dominant diacid species followed by succinic and malonic acids. Shorter chain diacids (C2-C5) showed the concentration maximum on 5-7 April; however, longer chain diacids (aerosols. During this event, we also observed the enhanced concentration of filterable bromine in both modes. Peaks of dicarboxylic acids in both coarse and fine aerosols during ozone depletion events indicate that heterogeneous reactions are occurring on coarse particle and possibly on fine particles as well. Dicarboxylic acids may be produced by the oxidation of precursor compounds such as glyoxal and glyoxylic and other ?-oxocarboxylic acids that contain aldehyde (hydrated form) group, being involved with ozone and halogen chemistry in the Arctic marine boundary layer.

Narukawa, M.; Kawamura, K.; Anlauf, K. G.; Barrie, L. A.

2003-09-01

156

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: 18hours at either room temperature (baseline arm) or 37C, and 6days 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; 37C arm, 5.98??0.48; 6-day arm, 6.72??0.23). PAXgene samples showed comparable RNA integrity in both baseline and 37C 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 37C 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. PMID:24855452

2014-01-01

157

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 Rzsadomb 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.

Kertsz, Zs.; Borbly-Kiss, I.; Hunyadi, I.

1999-04-01

158

Spatial and temporal variations of chemicals in the TSP aerosols simultaneously collected at three islands in Okinawa, Japan  

NASA Astrophysics Data System (ADS)

East Asia's rapid economic growth has led to concerns about the emission of air pollutants. We collected total suspended particle (TSP) aerosol samples simultaneously at three islands in Okinawa, Japan, which are downwind of East Asia, during the Asian dust season, to examine the spatial and temporal variations and chemical transformations of major chemicals in the aerosols. Weekly samples were collected from July 2008 to June 2010, and the concentrations of water-soluble cations, anions, and organic carbon (WSOC) were determined (n=303). Spatial distribution analysis showed that monthly mean concentrations of non-sea-salt (nss)-SO42- in the spring (Asian dust season) decreased with increasing distance from Asia, while the trend for NO3- was less evident, suggesting that chemical transformation affected the long-range transport of certain chemicals. Temporal variation analysis showed that concentrations of nss-SO42-, NO3-, and WSOC during the spring were about 2.0, 2.4, and 1.8 times those in the summer (cleaner air mass from the Pacific Ocean), respectively. This study demonstrated that air pollutants were transported from the Asian continent to the Okinawa islands and affected the air quality in the region. There may also be impacts on ecosystems, because increased concentrations of particulate NO3- could increase nutrient levels around the Okinawa islands.

Arakaki, Takemitsu; Azechi, Sotaro; Somada, Yuka; Ijyu, Moriaki; Nakaema, Fumiya; Hitomi, Yuya; Handa, Daishi; Oshiro, Yoshito; Miyagi, Youichi; Tsuhako, Ai; Murayama, Hitomi; Higaonna, Yumi; Tanahara, Akira; Itoh, Akihide; Fukushima, Soko; Higashi, Kazuaki; Henza, Yui; Nishikawa, Rin; Shinjo, Hibiki; Wang, Hongyan

2014-11-01

159

Trace elements in tropical African savanna biomass burning aerosols  

Microsoft Academic Search

As a part of the FOS\\/DECAFE experiment, aerosol particles emitted during prescribed savanna fires were collected in January 1991 at Lamto (Ivory Coast), either close to the emission or in ambient air. Analytical transmission electron microscopy pointed out the presence of sub-micrometer soots, salt condensates, vegetation relicts and soil derived particles. The samples were also analyzed for their total particulate

A. Gaudichet; F. Echalar; B. Chatenet; J. P. Quisefit; G. Malingre; H. Cachier; P. Buat-Menard; P. Artaxo; W. Maenhaut

1995-01-01

160

EFFECTS OF METEOROLOGY ON CONCENTRATIONS OF ACID AEROSOLS  

EPA Science Inventory

Ambient air samples of strong acid aerosol (H+), sulfate (So=4), ammonia (NH3), and ammonium (NH+4) were collected in Pittsburgh and Uniontown, Pennsylvania during the summer of 1990. igh correlations were found for both + and SO=4 concentrations between Pittsburgh and the semi-r...

161

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...

162

Use of satellite-based aerosol optical depth and spatial clustering to predict ambient PM2.5 concentrations  

PubMed Central

Satellite-based PM2.5 monitoring has the potential to complement ground PM2.5 monitoring networks, especially for regions with sparsely distributed monitors. Satellite remote sensing provides data on aerosol optical depth (AOD), which reflects particle abundance in the atmospheric column. Thus AOD has been used in statistical models to predict ground-level PM2.5 concentrations. However, previous studies have shown that AOD may not be a strong predictor of PM2.5 ground levels. Another shortcoming of remote sensing is the large number of non-retrieval days (i.e., days without satellite data available) due to clouds and snow- and ice-cover. In this paper we propose statistical approaches to overcome these two shortcomings, thereby making satellite imagery a viable method to estimate PM2.5 concentrations. First, we render AOD a robust predictor of PM2.5 mass concentration by introducing an AOD daily calibration approach through the use of mixed effects model. Second, we develop models that combine AOD and ground monitoring data to predict PM2.5 concentrations during non-retrieval days. A key feature of this approach is that we develop these prediction models separately for groups of days defined by the observed amount of spatial heterogeneity in concentrations across the study region. Subsequently, these methodologies were applied to examine the spatial and temporal patterns of daily PM2.5 concentrations for both retrieval days (i.e., days with satellite data available) and non-retrieval days in the New England region of the U.S. during the period 2000-2008. Overall, for the years 2000-2008, our statistical models predicted surface PM2.5 concentrations with reasonably high R2 (0.83) and low percent mean relative error (3.5%). Also the spatial distribution of the estimated PM2.5 levels in the study domain clearly exhibited densely populated and high traffic areas. The method we have developed demonstrates that remote sensing can have a tremendous impact on the fields of environmental monitoring and human exposure assessment. PMID:22841416

Lee, Hyung Joo; Coull, Brent A.; Bell, Michelle L.; Koutrakis, Petros

2012-01-01

163

Determinants of the Associations between Ambient Concentrations and Personal Exposures to Ambient PM2.5, NO2, and O3 during DEARS  

EPA Science Inventory

In this analysis, ambient concentrations and personal exposures to PM2.5, O3, and NO2, air exchange rates, meteorological parameters, and questionnaire survey responses collected during the Detroit Exposure and Aerosol Research Study (DEARS) are used: 1) to evaluate different met...

164

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

165

Use of a modified walkley-black method to determine the organic and elemental carbon content of urban aerosols collected on glass fibre filters  

Microsoft Academic Search

An analysis based on the Walkley-Black method is a rapid and effective means for determining the organic carbon, elemental carbon and total organic carbon content of urban aerosol samples collected on glass fibre and teflon-backed glass fibre filters. The estimated accuracy of the method is + 18%, ?33% and ?8% for OC, EC and TOC, respectively, the precision is 7%,

Y. C. Chan; P. D. Vowles; G. H. McTainsh; R. W. Simpson; D. D. Cohen; G. M. Bailey

1995-01-01

166

Aerosol Composition and Morphology during the 2005 Marine Stratus Radiation Aerosol and Drizzle Study  

NASA Astrophysics Data System (ADS)

The composition and morphology of aerosols activated within cloud droplets relative to the properties of aerosols not activated is of central importance to studies directed at improved parameterization of the treatment of aerosols in large scale models. These models have many applications, including evaluations of the impact of anthropogenic aerosols on climate. To further our understanding of these aerosol characteristics, scientists from the U.S. Department of Energy Atmospheric Sciences Program (ASP) joined forces with participants of the Atmospheric Radiation Measurement (ARM) program's `Marine Stratus Radiation Aerosol and Drizzle Study' field campaign at Pt. Reyes, CA. Observations between July 4 and July 29, 2005 from the ASP in situ aerosol instruments and from the ARM Mobile Facility will be combined in a first look at the measurements made during this period. High time resolution measurements of size-dependent particle bulk composition (sulfate, nitrate, NH4, organics, etc ) were made using a time-of-flight aerosol mass spectrometer (TOF-AMS, Aerodyne Research). Aerosols were simultaneously collected using a transient aerosol collector (TRAC, PNNL) for subsequent single particle analysis to determine elemental composition and morphology. Particle measurements and collections were made both from ambient, dried air and through a conterflow virtual impactor (CVI) to compare composition of nucleated vs., non-nucleated particles. A CCN counter was also deployed to measure the fraction of cloud droplet kernels activated as CCN over a range of super-saturations. Our presentation will partition measurements into periods of cloudy and cloud-free periods. Measurements will also be partitioned between periods associated with a) northerly back trajectories that arrived at the Pt. Reyes site after passing along the Washington-Oregon coast, b) westerly oceanic trajectories and c) a very limited number of periods when the air flow appeared to be associated with urban areas to the south and southeast.

Berkowitz, C. M.; Jobson, T.; Alexander, M. L.; Laskin, A.; Laulainen, N.

2005-12-01

167

Unattended Monitoring of HEU Production in Gaseous Centrifuge Enrichment Plants using Automated Aerosol Collection and Laser-based Enrichment Assay  

SciTech Connect

Nuclear power is enjoying rapid growth as government energy policies and public demand shift toward low carbon energy production. Pivotal to the global nuclear power renaissance is the development and deployment of robust safeguards instrumentation that allows the limited resources of the IAEA to keep pace with the expansion of the nuclear fuel cycle. Undeclared production of highly enriched uranium (HEU) remains a primary proliferation concern for modern gaseous centrifuge enrichment plants (GCEPs), due to their massive separative work unit (SWU) processing power and comparably short cascade equilibrium timescale. The Pacific Northwest National Laboratory is developing an unattended safeguards instrument, combining continuous aerosol particulate collection with uranium isotope assay, to provide timely detection of HEU production within a GCEP. This approach is based on laser vaporization of aerosol particulates, followed by laser spectroscopy to characterize the uranium enrichment level. Our prior investigation demonstrated single-shot detection sensitivity approaching the femtogram range and relative isotope ratio uncertainty better than 10% using gadolinium as a surrogate for uranium. In this paper we present measurement results on standard samples containing traces of depleted, natural, and low enriched uranium, as well as measurements on aerodynamic size uranium particles mixed in background materials (e.g., dust, minerals, soils). Improvements and optimizations in the detection electronics, signal timing, calibration, and laser alignment have lead to significant improvements in detection sensitivity and enrichment accuracy, contributing to an overall reduction in the false alarm probability. The sample substrate media was also found to play a significant role in facilitating laser-induced vaporization and the production of energetic plasma conditions, resulting in ablation optimization and further improvements in the isotope abundance sensitivity.

Anheier, Norman C.; Bushaw, Bruce A.

2010-08-11

168

AUTORAMP - an automatic unit for unattended aerosol collection, gamma-ray analysis and data transmission from remote locations  

SciTech Connect

The Environmental Measurements Laboratory has designed, developed and field tested a fully automated and completely unattended multisample, surface-air monitoring system. This system, AUTORAMP, collects large-volume aerosol samples on discrete pleated cartridge filters, measures these samples in a near ideal geometry with a refrigerator-cooled Germanium gamma-ray detector, and immediately transmits the resulting spectra through a telephone/modem connection or a satellite link. Using a sample tray loaded with 31 filters, the system will allow for more than six months of unattended operation with weekly sampling, or one month of daily sampling. Remote control of all operating functions is possible through the communications link. For a 24-h collection, at 12,000 m{sup 3} d{sup -1} and a 18-h gamma-ray count, this system can detect as little as 2.7 {mu}Bq m{sup -3} of the short-lived {sup 140}Ba and 5.4 {mu}Bq m{sup -3} of {sup 137}Cs.

Latner, N.; Sanderson, C.G.; Negro, V.C. [and others

1997-12-31

169

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 ...

170

Effects of Electrostatic Charge on Aerosol Collection with Polystyrene Filter Cassettes  

Microsoft Academic Search

Electrostatic fields are present on polystyrene cassette filter holders commonly used to measure the concentration of particles in air. Beryllium concentrations were determined at a beryllium refinery using neutral, and positively and negatively charged cassettes. In laboratory experiments, tobacco smoke, magnetite and polyvinyltoluene latex spheres were collected by both charged and neutral cassettes. No differences in concentration measurements were observed

SCOTT TURNER; BEVERLY S. COHEN

1984-01-01

171

Study Of The Elemental Composition Of Atmospheric Aerosols Collected In The Auger South Observatory Of Cosmic Rays, By Using The PIXE Technique  

NASA Astrophysics Data System (ADS)

We applied the PIXE (Particle-Induced X-ray Emission) technique to samples of atmospheric aerosols collected in filters in the Auger South Observatory, Malarge, Argentina, with instrument Andersen Graseby 240. We analyzed the concentration PM2.5, PM2.5-10 and PM10 by gravimetric analysis and the elemental composition of fine (size <2.5 ?m) and coarse (size between 2.5 ?m and 10 ?m) particles by PIXE technique. We complemented the elemental study with microscopic analysis, SEM/EDX. We discuss the concentration levels in the region, which in general are very low. We focus our analysis in winter and spring results. We find that concentration levels increase with increasing temperatures in the region. Most chemical elements have higher elemental concentrations in the coarse aerosols, but sulfur has higher elemental concentrations in fine aerosols.

Micheletti, M. I.; Graf, M.; Debray, M.; Murruni, L.; vila Cadena, G.; Vitale, P.; Davidson, J.; Piacentini, R. D.; Rosenbusch, M.; Somacal, H.

2010-08-01

172

Mass closure on the chemical species in size-segregated atmospheric aerosol collected in an urban area of the Po Valley, Italy  

NASA Astrophysics Data System (ADS)

A complete size segregated chemical characterisation was carried out for aerosol samples collected in the urban area of Bologna over a period of one year, using five-stage low pressure Berner impactors. An original dual-substrate technique was adopted to obtain samples suitable for a complete chemical characterisation. Total mass, inorganic, and organic components were analysed as a function of size, and a detailed characterisation of the water soluble organic compounds was also performed by means of a previously developed methodology, based on HPLC separation of organic compounds according to their acid character and functional group analysis by Proton Nuclear Magnetic Resonance. Chemical mass closure of the collected samples was reached to within a few percent on average in the submicron aerosol range, while a higher unknown fraction in the coarse aerosol range was attributed to soil-derived species not analysed in this experiment. Comparison of the functional group analysis results with model results simulating water soluble organic compound production by gas-to-particle conversion of anthropogenic VOCs showed that this pathway provides a minor contribution to the organic composition of the aerosol samples in the urban area of Bologna.

Matta, E.; Facchini, M. C.; Decesari, S.; Mircea, M.; Cavalli, F.; Fuzzi, S.; Putaud, J.-P.; Dell'Acqua, A.

2003-06-01

173

A thermal desorption mass spectrometer for freshly nucleated secondary aerosol particles  

NASA Astrophysics Data System (ADS)

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

Held, A.; Gonser, S. G.

2012-04-01

174

Comparative in vitro toxicity profile of electronic and tobacco cigarettes, smokeless tobacco and nicotine replacement therapy products: e-liquids, extracts and collected aerosols.  

PubMed

The use of electronic cigarettes (e-cigs) continues to increase worldwide in parallel with accumulating information on their potential toxicity and safety. In this study, an in vitro battery of established assays was used to examine the cytotoxicity, mutagenicity, genotoxicity and inflammatory responses of certain commercial e-cigs and compared to tobacco burning cigarettes, smokeless tobacco (SLT) products and a nicotine replacement therapy (NRT) product. The toxicity evaluation was performed on e-liquids and pad-collected aerosols of e-cigs, pad-collected smoke condensates of tobacco cigarettes and extracts of SLT and NRT products. In all assays, exposures with e-cig liquids and collected aerosols, at the doses tested, showed no significant activity when compared to tobacco burning cigarettes. Results for the e-cigs, with and without nicotine in two evaluated flavor variants, were very similar in all assays, indicating that the presence of nicotine and flavors, at the levels tested, did not induce any cytotoxic, genotoxic or inflammatory effects. The present findings indicate that neither the e-cig liquids and collected aerosols, nor the extracts of the SLT and NRT products produce any meaningful toxic effects in four widely-applied in vitro test systems, in which the conventional cigarette smoke preparations, at comparable exposures, are markedly cytotoxic and genotoxic. PMID:25361047

Misra, Manoj; Leverette, Robert D; Cooper, Bethany T; Bennett, Melanee B; Brown, Steven E

2014-11-01

175

Comparative In Vitro Toxicity Profile of Electronic and Tobacco Cigarettes, Smokeless Tobacco and Nicotine Replacement Therapy Products: E-Liquids, Extracts and Collected Aerosols  

PubMed Central

The use of electronic cigarettes (e-cigs) continues to increase worldwide in parallel with accumulating information on their potential toxicity and safety. In this study, an in vitro battery of established assays was used to examine the cytotoxicity, mutagenicity, genotoxicity and inflammatory responses of certain commercial e-cigs and compared to tobacco burning cigarettes, smokeless tobacco (SLT) products and a nicotine replacement therapy (NRT) product. The toxicity evaluation was performed on e-liquids and pad-collected aerosols of e-cigs, pad-collected smoke condensates of tobacco cigarettes and extracts of SLT and NRT products. In all assays, exposures with e-cig liquids and collected aerosols, at the doses tested, showed no significant activity when compared to tobacco burning cigarettes. Results for the e-cigs, with and without nicotine in two evaluated flavor variants, were very similar in all assays, indicating that the presence of nicotine and flavors, at the levels tested, did not induce any cytotoxic, genotoxic or inflammatory effects. The present findings indicate that neither the e-cig liquids and collected aerosols, nor the extracts of the SLT and NRT products produce any meaningful toxic effects in four widely-applied in vitro test systems, in which the conventional cigarette smoke preparations, at comparable exposures, are markedly cytotoxic and genotoxic. PMID:25361047

Misra, Manoj; Leverette, Robert D.; Cooper, Bethany T.; Bennett, Melanee B.; Brown, Steven E.

2014-01-01

176

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

NASA Astrophysics Data System (ADS)

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 a capillary gas chromatography technique. We found elevated concentrations of atmospheric citric acid (range: 20-320 ng m -3) in the TSP samples during mid- to late April of 2007 and 2008. To specify the sources of citric acid, dicarboxylic acids and related compounds were measured in the pollen sample collected at the Gosan site (Pollen_Gosan), authentic pollen samples from Japanese cedar ( Cryptomeria) (Pollen_cedar) and Japanese cypress ( Chamaecyparis obtusa) (Pollen_cypress), and tangerine fruit produced from Jeju Island. Citric acid (2790 ng in unit mg of pollen mass) was found as most abundant species in the Pollen_Gosan, followed by oxalic acid (2390 ng mg -1). Although citric acid was not detected in the Pollen_cedar and Pollen_cypress as major species, it was found as a dominant species in the tangerine juice while malic acid was detected as major species in the tangerine peel, followed by oxalic and citric acids. Since Japanese cedar trees are planted around tangerine farms to prevent strong winds from the Pacific Ocean, citric acid that may be directly emitted from tangerine is likely adsorbed on pollens emitted from Japanese cedar and then transported to the Gosan site. Much lower malic/citric acid ratios obtained under cloudy condition than clear condition suggest that malic acid may rapidly decompose to lower molecular weight compounds such as oxalic and malonic acids (

Jung, Jinsang; Kawamura, Kimitaka

2011-09-01

177

Characterization of Heavy Metal Contents in the Bulk Atmospheric Aerosols Simultaneously Collected at Three Islands in Okinawa, Japan by X-ray fluorescence spectrometric method (XRF)  

NASA Astrophysics Data System (ADS)

We studied heavy metal contents of atmospheric aerosols using an X-ray fluorescence spectrometric method (XRF). The XRF method enables us to analyze heavy metal contents of bulk aerosols rapidly without any chemical pretreatments. We used an energy dispersive X-ray fluorescence spectrometer that is compact and portable. We prepared several different amounts of standard reference materials (NIES No.28) of Japanese National Institute of Environmental Studies on quartz filters for calibration curves. Then, we evaluated quantitative responses of XRF method by comparing with the metal contents determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after acid-digestion. Good linear relationships between X-ray intensity and amount of aerosol on filter were seen in the following 10 metals; Al, K, Ti, V, Fe, Ni, Rb, Ba, Pb and As. We then used XRF method to determine heavy metal contents in authentic atmospheric aerosols collected in Okinawa islands, Japan. Okinawa islands, consisting of many small islands, are situated east of Asian continent, and its location in Asian is well suited for studying long-range transport of air pollutants. Also, in Okinawa islands, maritime air mass prevails during summer, while Asian continental air mass dominates during fall, winter, and spring. The maritime air mass data can be seen as background clean air and can be compared with continental air mass which has been affected by anthropogenic activities such as industries and automobiles. Therefore, Okinawa region is suitable area for studying impacts of air pollutants from East Asia. We simultaneously collected bulk aerosol samples by using identical high-volume air samplers at 3 islands; Cape Hedo Atmospheric 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 report and discuss spatial and temporal distribution of heavy metals determined by the XRF method in the bulk atmospheric aerosols collected at the three islands during June 2008 to June 2010, and for CHAAMS during June 2008 to September 2011.

Oshiro, Y.; ITOH, A.; Azechi, S.; Somada, Y.; Handa, D.; Miyagi, Y.; Arakaki, T.; Tanahara, A.

2011-12-01

178

Comparison between XRF and IBA techniques in analysis of fine aerosols collected in Rijeka, Croatia  

NASA Astrophysics Data System (ADS)

The new system for energy dispersive X-ray fluorescence (EDXRF) analysis has been installed at the Laboratory for Elemental Micro-Analysis (LEMA) at the University of Rijeka. Currently the key application of this new XRF system is in the field of environmental science, i.e. in the analysis of fine airborne particles. In this work, results of initial multi-elemental analysis of PM2.5 fraction is reported for the first time in the region of Rijeka, Croatia. Sampling was performed at the Rijeka City center, during a continuous 9-day period in February/March 2012. All samples were collected on stretched Teflon filters in 12 h periods. To check the reliability of the new XRF system, results of XRF analysis are compared with the results obtained by the well-established Ion Beam Analysis (IBA) laboratory at Australian Nuclear Science and Technology Organisation (ANSTO). The concentrations of H, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br and Pb were determined. In addition, black carbon was determined by Laser Integrating Plate Method (LIPM). Very good agreement between XRF and IBA techniques is obtained for all elements detected by both techniques. Elemental concentrations were correlated with the traffic volume and wind speed and direction. The summary of our findings is presented and discussed in this paper.

Ivoevi?, Tatjana; Mandi?, Luka; Orli?, Ivica; Stelcer, Eduard; Cohen, David D.

2014-10-01

179

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. Typical continental and maritime aerosol particle distributions were used for background and plume distributions and each time the deposited particle mass was calculated with the old and the new efficiencies for the different resulting precipitation rates. In the simulations the new efficiencies increased the calculated wet removal rate of pollution plume particles between 5% and 17%, with respect to the simulations with the old efficiencies, whereby one third of this increase could be attributed to rear capture. This phenomenon has not been observed in these size ranges before. The study also highlights the weakness of certain methods to determine the scavenging coefficient of a pollution plume by rain. Instead of linking the scavenging coefficient to the decrease of the particle spectrum in the air, an operational approach, e.g. in case of accidental releases, needs to be developed that links it to the rainfall intensity, as well as other variables like meteorological parameters, cloud size and plume characteristics. Considering the still persisting gaps of measurements in the collection efficiencies more laboratory measurements of collection scavenging efficiencies between aerosol particles and raindrops are also necessary.

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

2014-06-01

180

The effect of temperature on the gas-particle partitioning of reactive mercury in atmospheric aerosols  

NASA Astrophysics Data System (ADS)

Measurements of gas-particle-partitioning coefficients for reactive mercury in dry urban and laboratory aerosol were found to strongly depend on ambient temperature. Samples of atmospheric and laboratory aerosols (defined as both the gas and particle phases) were collected using filter and absorbent methods and analyzed for reactive mercury using thermal desorption combined with cold vapor atomic fluorescence spectroscopy. Synthetic ambient aerosols were generated in the laboratory from ammonium sulfate and adipic acid mixed with mercuric chloride in a purpose-built aerosol reactor. The aerosol reactor was operated in a temperature-controlled laboratory. Linear relationships between the logarithm of inverse gas-particle partitioning and inverse temperature were observed and parameterized for use in the atmospheric modeling of reactive mercury. Reactive mercury was observed to partition from the particle to the gas phase as ambient temperature increased. Good agreement between measurements made using urban and laboratory aerosols was seen after gas-particle-partitioning coefficients were normalized for surface area instead of mass. Thermodynamic analyses of the urban and laboratory gas-particle-partitioning measurements revealed that the strength of interaction between reactive mercury and particle surfaces was suggestive of chemisorption. Gas-particle-partitioning coefficients made with the Tekran ambient mercury analyzer (AMA) also showed a dependence on temperature. However, the Tekran AMA partitioning coefficients did not agree well with partitioning coefficients measured using the filter-based methods. The disagreement is consistent with the 50 C operational temperature of the Tekran AMA.

Rutter, Andrew P.; Schauer, James J.

181

SOURCE APPORTIONMENT OF PHOENIX PM2.5 AEROSOL WITH THE UNMIX RECEPTOR MODEL  

EPA Science Inventory

The multivariate receptor model Unmix has been used to analyze a 3-yr PM2.5 ambient aerosol data set collected in Phoenix, AZ, beginning in 1995. The analysis generated source profiles and overall percentage source contribution estimates (SCE) for five source categories: ga...

182

Evaluation of Dried Blood Spots Collected on Filter Papers from Three Manufacturers Stored at Ambient Temperature for Application in HIV-1 Drug Resistance Monitoring  

PubMed Central

As more HIV-infected people gain access to antiretroviral therapy (ART), monitoring HIV drug resistance (HIVDR) becomes essential to combat both acquired and transmitted HIVDR. Studies have demonstrated dried blood spots (DBS) are a suitable alternative in HIVDR monitoring using DBS collected on Whatman 903 (W-903). In this study, we sought to evaluate two other commercially available filter papers, Ahlstrom 226 (A-226) and Munktell TFN (M-TFN), for HIVDR genotyping following ambient temperature storage. DBS were prepared from remnant blood specimens collected from 334 ART patients and stored at ambient temperature for a median time of 30 days. HIV-1 viral load was determined using NucliSENS EasyQ HIV-1 v2.0 RUO test kits prior to genotyping of the protease and reverse transcriptase regions of the HIV-1 pol gene using an in-house assay. Among the DBS tested, 26 specimens had a viral load ?1000 copies/mL in all three types of filter paper and were included in the genotyping analysis. Genotyping efficiencies were similar between DBS collected on W-903 (92.3%), A-226 (88.5%), and M-TFN (92.3%) filter papers (P?=?1.00). We identified 50 DR-associated mutations in DBS collected on W-903, 33 in DBS collected on A-226, and 48 in DBS collected on M-TFN, resulting in mutation detection sensitivities of 66.0% for A-226 and 88.0% for M-TFN when compared to W-903. Our data indicate that differences among filter papers may exist at this storage condition and warrant further studies evaluating filter paper type for HIVDR monitoring. PMID:25303690

Rottinghaus, Erin K.; Beard, R. Suzanne; Bile, Ebi; Modukanele, Mosetsanagape; Maruping, Maruping; Mine, Madisa; Nkengasong, John; Yang, Chunfu

2014-01-01

183

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...

184

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

185

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 2. 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.

2014-12-01

186

Characteristics of regional aerosols: Southern Arizona and eastern Pacific Ocean  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5 ?m are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number concentration of giant cloud condensation nuclei (Dp > 2 microm) in ship plumes relative to the unperturbed background regions over the ocean.

Prabhakar, Gouri

187

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

188

MODIS Collection 6 aerosol products: Comparison between Aqua's e-Deep Blue, Dark Target, and "merged" data sets, and usage recommendations  

NASA Astrophysics Data System (ADS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) Atmospheres data product suite includes three algorithms applied to retrieve midvisible aerosol optical depth (AOD): the Enhanced Deep Blue (DB) and Dark Target (DT) algorithms over land, and a DT over-water algorithm. All three have been refined in the recent "Collection 6" (C6) MODIS reprocessing. In particular, DB has been expanded to cover vegetated land surfaces as well as brighter desert/urban areas. Additionally, a new "merged" data set which draws from all three algorithms is included in the C6 products. This study is intended to act as a point of reference for new and experienced MODIS data users with which to understand the global and regional characteristics of the C6 DB, DT, and merged data sets, based on MODIS Aqua data. This includes validation against Aerosol Robotic Network (AERONET) observations at 111 sites, focused toward regional and categorical (surface/aerosol type) analysis. Neither algorithm consistently outperforms the other, although in many cases the retrieved AOD and the level of its agreement with AERONET are very similar. In many regions the DB, DT, and merged data sets are all suitable for quantitative applications, bearing in mind that they cannot be considered independent, while in other cases one algorithm does consistently outperform the other. Usage recommendations and caveats are thus somewhat complicated and regionally dependent.

Sayer, A. M.; Munchak, L. A.; Hsu, N. C.; Levy, R. C.; Bettenhausen, C.; Jeong, M.-J.

2014-12-01

189

Classification of collective behavior: a comparison of tracking and machine learning methods to study the effect of ambient light on fish shoaling.  

PubMed

Traditional approaches for the analysis of collective behavior entail digitizing the position of each individual, followed by evaluation of pertinent group observables, such as cohesion and polarization. Machine learning may enable considerable advancements in this area by affording the classification of these observables directly from images. While such methods have been successfully implemented in the classification of individual behavior, their potential in the study collective behavior is largely untested. In this paper, we compare three methods for the analysis of collective behavior: simple tracking (ST) without resolving occlusions, machine learning with real data (MLR), and machine learning with synthetic data (MLS). These methods are evaluated on videos recorded from an experiment studying the effect of ambient light on the shoaling tendency of Giant danios. In particular, we compute average nearest-neighbor distance (ANND) and polarization using the three methods and compare the values with manually-verified ground-truth data. To further assess possible dependence on sampling rate for computing ANND, the comparison is also performed at a low frame rate. Results show that while ST is the most accurate at higher frame rate for both ANND and polarization, at low frame rate for ANND there is no significant difference in accuracy between the three methods. In terms of computational speed, MLR and MLS take significantly less time to process an image, with MLS better addressing constraints related to generation of training data. Finally, all methods are able to successfully detect a significant difference in ANND as the ambient light intensity is varied irrespective of the direction of intensity change. PMID:25294042

Butail, Sachit; Salerno, Philip; Bollt, Erik M; Porfiri, Maurizio

2014-10-01

190

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

191

Single-particle 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.  

PubMed

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 aerosol samples were obtained by a seven-stage May cascade impactor with a flow rate of 20 L/min. Overall 11,200 particles on stages 1-6 with cutoff diameters of 16, 8, 4, 2, 1, and 0.5 microm, respectively, were examined and classified based on their secondary electron images and X-ray spectra. In general, sea salt particles were the most frequently encountered, followed by mineral dust, organic carbon (OC)-like, (NH4)2SO4/NH4HSO4-containing, elemental carbon (EC)-like, Fe-rich, and K-rich particles. Sea salt and mineral dust particles had a higher relative abundance on stages 1-5, whereas OC-like, (NH4)2SO4/NH4HSO4-containing, Fe-rich, and K-rich particles were relatively abundant on stage 6. The analysis on relative number abundances of various particle types combined with 72-hr backward air mass trajectories indicated that a lot of reacted sea salt and reacted mineral dust (with airborne NOx and SO2 or their acidic products) and OC-like particles were carried by the air masses passing over the Yellow Sea (for sample "10 April") and many NH4HSO4/ (NH4)2SO4-containing particles were carried by the air masses passing over the Sea of Japan and Korea Strait (for samples "4-9 April"). It was concluded that the atmosphere over Jeju Island was influenced by anthropogenic SO2 and NOx, organic compounds, and secondary aerosols when Asian dust was absent. PMID:22168102

Geng, Hong; Cheng, Fangqin; Ro, Chul-Un

2011-11-01

192

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

193

Effects of operating conditions on a heat transfer fluid aerosol  

E-print Network

of heat transfer fluid aerosols from process leaks. To simulate industrial leaks, aerosol formation from a plain orifice into ambient air is studied by measuring liquid drop sizes and size distributions at various distances from an orifice. Measurements...

Sukmarg, Passaporn

2012-06-07

194

Non-ammonium reduced nitrogen species in atmospheric aerosol particles  

SciTech Connect

The traditional belief that ambient aerosol particles contain nitrogen predominantly in the form of inorganic ionic species such as NH/sub 4//sup +/ and NO/sub 3//sup -/ was challenged about 10 years ago by results from x-ray photoelectron spectroscopic analysis (ESCA) of California aerosol particles. A significant fraction (approx. 50%) of the reduced nitrogen was observed to have an oxidation state more reduced than ammonium, characteristic of organic nitrogen species. We have used a recently developed thermal evolved gas analysis method (NO/sub x/) in conjunction with ESCA to confirm the existence of these species in aerosol particles collected in both the United States and Europe. The agreement of EGA and ESCA analyses indicates that these species are found not only on the surface but also throughout the particles. 9 references, 6 figures.

Dod, R.L.; Gundel, L.A.; Benner, W.H.; Novakov, T.

1983-08-01

195

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.

Phlker, Christopher; Saturno, Jorge; Krger, Mira L.; Frster, Jan-David; Weigand, Markus; Wiedemann, Kenia T.; Bechtel, Michael; Artaxo, Paulo; Andreae, Meinrat O.

2014-05-01

196

EXPOSURES TO ACIDIC AEROSOLS  

EPA Science Inventory

Ambient monitoring of acid aerosol in four U.S. cities and in a rural region of southern Ontario clearly show distinct periods of strong acidity. easurements made in Kingston, TN, and Stuebenville, OH, resulted in 24-hr H+ ion concentrations exceeding 100 nmole/m3 more than 10 ti...

197

FORMATION OF PHOTOCHEMICAL AEROSOLS  

EPA Science Inventory

The objective was to develop a better understanding of smog aerosol formation with particular reference to haze in the Southern California area. This study combined laboratory work with ambient air studies. Counting of particles by light scattering was the principle physical tech...

198

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

199

The impact of changing surface ocean conditions on the dissolution of aerosol iron  

NASA Astrophysics Data System (ADS)

proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 m) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 m). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

Fishwick, Matthew P.; Sedwick, Peter N.; Lohan, Maeve C.; Worsfold, Paul J.; Buck, Kristen N.; Church, Thomas M.; Ussher, Simon J.

2014-11-01

200

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

201

Aerosol Mass Spectrometer measurements on board the DOE G1 during NEAQS  

NASA Astrophysics Data System (ADS)

An Aerosol Mass Spectrometer (AMS) was successfully deployed on board the DOE G1 research aircraft during the New England Air Quality Study (NEAQS), a multi agency campaign designed to characterize gas and aerosol pollutants passing through the northeastern U.S. and the outflow over the Atlantic Ocean. The addition of the AMS to the G1 instrument payload added the capability to collect real-time (seconds timescale) data on size and chemically speciated aerosol mass loadings for aerosol containing nitrate, sulfate, ammonium, chloride and organic species. Flight tracks were chosen to provide reasonable lateral coverage of the North Eastern region and important vertical profiles of ambient aerosol. Comparisons between the aerosol chemical properties measured from the G1 platform and similar aerosol properties measured at several ground sites, including on the Ron Brown research vessel, illustrate the layering of air masses and the varying sources and transportation pathways for particulate pollution. Ground level particulate measurements appear significantly influenced by regional sources. For example, bimodal organic carbon dominated size distributions consistent with freshly generated (automobile) emission were observed on flights that passed over NY city metropolitan area. In contrast, vertical profiles identify layers of high mass loadings of monomodal particulate sulfate aerosol accompanied by low SO2 levels that are consistent with aged/transported air. Back trajectory analyses correlate these observations with source emitters outside of the North Eastern region.

Onasch, T.; Jayne, J.; Canagaratna, M.; Worsnop, D.; Laskin, A.

2003-12-01

202

In Situ Aerosol Optical Thickness Collected by the SIMBIOS Program (1997-2000): Protocols, and and Data QC and Analysis  

NASA Technical Reports Server (NTRS)

The purpose of this technical report is to provide current documentation of the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project Office activities on in situ aerosol optical thickness (i.e., protocols, and data QC and analysis). This documentation is necessary to ensure that critical information is related to the scientific community and NASA management. This critical information includes the technical difficulties and challenges of validating and combining ocean color data from an array of independent satellite systems to form consistent and accurate global bio-optical time series products. This technical report is not meant as a substitute for scientific literature. Instead, it will provide a ready and responsive vehicle for the multitude of technical reports issued by an operational project.

Fargion, Giulietta S.; Barnes, Robert; McClain, Charles

2001-01-01

203

Chemical characterization of the ambient organic aerosol soluble in water: 1. Isolation of hydrophobic and hydrophilic fractions with a XAD-8 resin  

NASA Astrophysics Data System (ADS)

Group separation of the aqueous extract of fine particles bearing water-soluble organic carbon (WSOC) provides unique insights into the sources of organic carbon (OC). XAD-8 resin coupled with a Total Organic Carbon analyzer allows for direct quantification. We term the fraction of WSOC not retained by a XAD-8 resin column at pH 2 as hydrophilic WSOC (WSOCxp); this includes saccharides, amines, and carbonyls and aliphatic monocarboxylic/dicarboxylic/oxocarboxylic acids with less than 4 or 5 carbons. The fraction of WSOC retained by XAD-8, termed the hydrophobic fraction (WSOCxr), include aromatic acids, phenols, organic nitrates, cyclic acids, and carbonyls and monocarboxylic/dicarboxylic acids with greater than 3 or 4 carbons. However, only aromatic compounds (or aromatic-like compounds with similar properties) can subsequently be extracted from XAD-8 with high efficiency. By coupling a Particle-into-Liquid Sampler with this technique, online measurements of WSOC, WSOCxp, and WSOCxr are possible. Urban measurements from St. Louis and Atlanta, on a carbon mass basis, show an increase in the mean WSOC fraction from winter (51%) to summer (61%), due to increases in the WSOCxp/OC from 0.25 to 0.35. During a summer Atlanta PM event, WSOC to OC was 0.75, driven largely by increases in the WSOCxp. The results are consistent with the view that in the summer, there are increased amounts of oxygenated polar compounds, possibly from secondary organic aerosol production, and that these compounds account for an even larger fraction of OC during stagnation events. A companion paper describes a method to further group speciate these XAD-8 isolated fractions.

Sullivan, Amy P.; Weber, Rodney J.

2006-03-01

204

Updated study reporting levels (SRLs) for trace-element data collected for the California Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project, October 2009-March 2013  

USGS Publications Warehouse

Groundwater samples have been collected in California as part of statewide investigations of groundwater quality conducted by the U.S. Geological Survey for the Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project (PBP). The GAMA-PBP is being conducted in cooperation with the California State Water Resources Control Board to assess and monitor the quality of groundwater resources used for drinking-water supply and to improve public knowledge of groundwater quality in California. Quality-control samples (source-solution blanks, equipment blanks, and field blanks) were collected in order to ensure the quality of the groundwater sample results. Olsen and others (2010) previously determined study reporting levels (SRLs) for trace-element results based primarily on field blanks collected in California from May 2004 through January 2008. SRLs are raised reporting levels used to reduce the likelihood of reporting false detections attributable to contamination bias. The purpose of this report is to identify any changes in the frequency and concentrations of detections in field blanks since the last evaluation and update the SRLs for more recent data accordingly. 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), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), tungsten (W), uranium (U), vanadium (V), and zinc (Zn). Data from 179 field blanks and equipment blanks collected from March 2006 through March 2013 by the GAMA-PBP indicated that for trace elements that had a change in detection frequency and concentration since the previous review, the shift occurred near October 2009, in conjunction with a change in the capsule filters used by the study. Results for 89 field blanks and equipment blanks collected from October 2009 through March 2013 were evaluated for potential contamination bias by using the same approach developed by Olsen and others (2010). Some data collected by the National Water-Quality Assessment (NAWQA) Program for the Southern California Coastal Drainages study unit were included to supplement the GAMA-PBP data. The detection frequency and upper threshold of potential contamination bias (BD-90/90) were determined from field-blank and equipment-blank data for each trace element. The BD-90/90 is the 90th percentile concentration of potential extrinsic contamination calculated by using the binomial probability distribution for greater than 90 percent confidence. Additionally, data from laboratory blanks and blind blanks analyzed by the National Water Quality Laboratory (NWQL) during water years 2010 through 2013, and compiled by the USGS Branch of Quality Systems (BQS), were considered for each trace element. These results were compared to each constituents reporting level to determine whether an SRL was necessary to minimize the potential for detections in the groundwater samples, attributed principally to contamination bias. Results of the evaluation were used to set SRLs for trace-element data for about 1,135 samples of groundwater collected by the GAMA-PBP between October 2009 and March 2013. Ten trace elements analyzed (Sb, As, Be, B, Cd, Li, Se, Ag, Tl, and U) had blank results that did not necessitate establishing SRLs during this review or the review by Olsen and others (2010). Five trace elements analyzed (Al, Ba, Cr, Sr, and V) had blank results that necessitated establishing an SRL during the previous review but did not need an SRL starting October 2009. One trace element (Fe) had field and laboratory-blank results that necessitated keeping the previous SRL (6 micrograms per liter [?g/L]). Two trace elements (Ni and W) had quality-control results that warranted decreasing the previous SRL, and five trace elements (Cu, Pb, Mn, Mo, and Zn) had field, laboratory, or blind blank results that warranted establishing an SRL for the first time or increasing the previous SRL. SRLs fo

Davis, Tracy A.; Olsen, Lisa D.; Fram, Miranda S.; Belitz, Kenneth

2014-01-01

205

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

206

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

207

Physicochemical Characterization of Capstone Depleted Uranium Aerosols I: Uranium Concentration in Aerosols as a Function of Time and Particle Size  

Microsoft Academic Search

During the Capstone Depleted Uranium (DU) Aerosol Study, aerosols containing depleted uranium were produced inside unventilated armored vehicles (i.e., Abrams tanks and Bradley Fighting Vehicles) by perforation with large-caliber DU penetrators. These aerosols were collected and characterized, and the data were subsequently used to assess human health risks to personnel exposed to DU aerosols. The DU content of each aerosol

MaryAnn Parkhurst; Yung-Sung Cheng; Judson L. Kenoyer; Richard J. Traub

2009-01-01

208

Cooling the NGI - an approach to size a nebulised aerosol more accurately.  

PubMed

The European Pharmaceutical Aerosol Group (EPAG) has undertaken investigations with the aim of developing robust methods for the droplet size analysis of nebuliser-produced aerosols in support of the proposed European Pharmacopeia general chapter 2.9.44 covering preparations for nebulisation. A multi-centre study was designed to investigate the effects of cooling the Next Generation pharmaceutical Impactor (NGI) before sample collection, as a means of reducing bias and variability caused by heat transfer-related evaporation. Droplets containing salbutamol were sized from 3 different nebulisers chosen to offer fundamentally different modes of aerosol generation: AeroNeb Go, a vibrating mesh nebuliser; PARI LC Plus, a breath-enhanced jet nebuliser; and MistyMax, a constant-output jet nebuliser. Each laboratory undertook determinations at ambient temperature, using an NGI pre-cooled in a refrigerator (5 degrees C for at least 90 min). The corresponding measurements were made using an ambient NGI as a benchmark. Salbutamol solution 5 mg/2 ml (Teva, Runcorn, UK) was used throughout the study. Analysis of individual and pooled results from 5 of the participants showed a similar trend insofar as the cooled NGI yielded a coarser nebulised aerosol than that obtained by the ambient NGI. Mass Median Aerodynamic Diameter (MMAD) was on average reduced by 9.5-21.9 % and the Fine Droplet Fraction < 5 microm (FDF) increased on average by 5.5-17.4 % for all the nebuliser designs when comparing ambient to cooled NGI. Despite the more laborious procedure of cooling the NGI, variability in data was generally similar to that obtained with the ambient NGI. We conclude that it is beneficial to cool the NGI when sizing nebulised aerosol. Furthermore, occasional findings during this study revealed a build-up of solute deposits within the interior of the NGI, and a more rigorous impactor cleaning/drying procedure is therefore recommended. PMID:18430404

Dennis, J; Berg, E; Sandell, D; Ali, A; Lamb, P; Tservistas, M; Karlsson, M; Mitchell, J

2008-02-01

209

Effect of particle loading on the collection performance of an electret cabin air filter for submicron aerosols  

Microsoft Academic Search

Electret filters are composed of permanently charged electret fibers and are widely used in applications requiring high collection efficiency and low-pressure drop. We tested electret filter media used in manufacturing cabin air filters by applying two different charging states to the test particles. These charging states were achieved by spray electrification through the atomization process and by bipolar ionization with

J. H. Ji; G. N. Bae; S. H. Kang; J. Hwang

2003-01-01

210

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...

211

The SPARC Aerosol Assessment  

NASA Astrophysics Data System (ADS)

Stratospheric Processes and their Role in Climate (SPARC), a project of the WMO/ICSU/IOC World Climate Research Programme, was responsible for the recent SPARC Assessment of Upper Tropospheric and Stratospheric Water Vapour. SPARC has now decided to generate an analogous document for the stratospheric aerosol, using many of the measurements that have been developed in the last twenty years, but relying heavily on the SAGE II data set. The stratospheric aerosol assessment involves a large international collection of atmospheric scientists whose special area of expertise is the stratospheric aerosol. Key questions that have been identified as requiring answers include: How have aerosol properties such as surface area density varied with time? How representative are satellite-based climatologies? What is the non-volcanic bacground for stratospheric aerosol and can a trend in it be detected? How well can models reproduce observed aerosol properties? We report on the ``kickoff" workshop that was held at the CNES headquarters in Paris on November 4-6, 2001. We shall describe some of the interesting results that were based on the SAGE II data set. The assessment will be carried out by five working groups each focussing on one of the following aspects: processes, aerosol precursors, climatology, trends and modeling. The long records from SAGE II, HALOE and other space based instruments will play a prominent role in construction of a climatology. It is expected that a valuable result of this assessment will be a set of ``standard" stratospheric aerosol parameters for use by modelers.

Hamill, P.; Thomason, L. W.; Peter, T.

2002-05-01

212

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

213

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

PubMed Central

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

2012-01-01

214

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

215

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....

216

Aerosol composition and source apportionment in Santiago de Chile  

Microsoft Academic Search

Santiago de Chile, So Paulo and Mexico City are Latin American urban areas that suffer from heavy air pollution. In order to study air pollution in Santiago area, an aerosol source apportionment study was designed to measure ambient aerosol composition and size distribution for two downtown sampling sites in Santiago. The aerosol monitoring stations were operated in Gotuzo and Las

Paulo Artaxo; Pedro Oyola; Roberto Martinez

1999-01-01

217

5, 41434182, 2005 Mexico City aerosol  

E-print Network

ACPD 5, 4143­4182, 2005 Mexico City aerosol during MCMA-2003 using an AMS ­ Part I D. Salcedo et al and Physics Discussions Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign Morelos, Cuernavaca, Morelos, Mexico 2 Cooperative Institute for Research in the Environmental Sciences

Paris-Sud XI, Université de

218

5, 41834221, 2005 Mexico City aerosol  

E-print Network

ACPD 5, 4183­4221, 2005 Mexico City aerosol during MCMA-2003 using an AMS ­ Part II D. Salcedo et and Physics Discussions Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign´imicas, Universidad Aut´onoma del Estado de Morelos, Cuernavaca, Mexico 2 Cooperative Institute for Research

Paris-Sud XI, Université de

219

Oxodicarboxylic acids in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Fine mode aerosol was collected on quartz fiber filters at several sites across Europe. These samples were analyzed for carboxylic acids by liquid chromatography coupled to a hybrid (quadrupole and time-of-flight) mass spectrometer (LC/MS/MS-TOF). A series of oxodicarboxylic acids (C 7-C 11) was detected. Oxodicarboxylic acids are linear dicarboxylic acids with an additional carbonyl group. Previous measurements of these acids are scarce and their sources are largely unknown. Several structural isomers (different positions of the carbonyl group within the molecule) could be identified and differentiated by the combination of laboratory experiments and high mass accuracy measurements. The homologs with 9-11 carbon atoms were identified for the first time in atmospheric aerosol particles. The concentrations of oxodicarboxylic acids in ambient aerosol samples frequently exceeded those of the corresponding unsubstituted dicarboxylic acids. Oxodicarboxylic acids have been shown to be products of the reaction of dicarboxylic acids with OH radicals in chamber experiments and a reaction mechanism is proposed. Good correlation of oxodicarboxylic acid and hydroxyl radical concentrations was found at two measurement sites (Finland and Crete) of different geographic location and meteorological conditions. The ratios of individual isomers from the field samples are comparable to those of the laboratory experiments. The results of this study imply that the reaction of OH radicals and dicarboxylic acids is an important pathway for the production of oxodicarboxylic acids in the atmosphere. Oxodicarboxylic acids seem to be important intermediates in atmospheric oxidation processes of organic compounds.

Rmpp, Andreas; Winterhalter, Richard; Moortgat, Geert K.

220

The use of multi-band transmission data collected at Scripps pier in November 2006 for the investigation of aerosol characteristics  

Microsoft Academic Search

The knowledge of the atmospheric aerosol characteristics is of great importance for the range performance of Infrared and Electro-Optical sensor systems. The composition, the concentration and the size distribution of aerosols determine their scattering behavior as function of wavelength and thus their attenuation of light beams. When studies are made on this attenuation, it is considered to be very useful

Arie N. de Jong; Alexander M. J. van Eijk; Peter J. Fritz; Leo H. Cohen; Marcel M. Moerman

2007-01-01

221

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...

222

Heterogeneous Surface-Based Freezing of Atmospheric Aerosols Containing Ash, Soot, and Soil  

E-print Network

Nucleation of ice crystals in the atmosphere often occurs through heterogeneous freezing processes facilitated by an atmospheric aerosol that acts as the ice nuclei (IN). Depending on ambient conditions and aerosol composition, heterogeneous...

Fornea, Adam P.

2010-07-14

223

Aerosol Science and Technology, 39:760770, 2005 Copyright c American Association for Aerosol Research  

E-print Network

of the AMS with a Particle-Into-Liquid Sampler combined with an Ion Chromatography analyzer (PILS-refractory (vaporized at 600 C under vacuum) submicron aerosols with a time resolution of the order of minutes. Ambient s at 600 C under high vacuum) submicron aerosols, with an integration time of the order of seconds

Jimenez, Jose-Luis

224

Size distribution, shape, and composition of mineral dust aerosols collected during the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass-Burning Experiment field campaign in Niger, January 2006  

NASA Astrophysics Data System (ADS)

Dust samples were collected onboard the UK community BAe-146 research aircraft of the Facility for Airborne Atmospheric Measurements (FAAM) operated over Niger during the winter Special Observation Period of the African Monsoon Multidisciplinary Analysis project (AMMA SOP0/DABEX). Particle size, morphology, and composition were assessed using single-particle analysis by analytical scanning and transmission electron microscopy. The aerosol was found to be composed of externally mixed mineral dust and biomass burning particles. Mineral dust consists mainly of aluminosilicates in the form of illite and kaolinite and quartz, accounting for up to 80% of the aerosol number. Fe-rich particles (iron oxides) represented 4% of the particle number in the submicron fraction. Diatoms were found on all the samples, suggesting that emissions from the Bodl depression were also contributing to the aerosol load. Satellite images confirm that the Bodl source was active during the period of investigation. Biomass burning aerosols accounted for about 15% of the particle number of 0.1-0.6 ?m diameter and were composed almost exclusively of particles containing potassium and sulfur. Soot particles were very rare. The aspect ratio AR is a measure of particle elongation. The upper limit of the AR value distribution is 5 and the median is 1.7, which suggests that mineral dust particles could be described as ellipsoids whose major axis never exceeds 1.9 Dp (the spherical geometric diameter). This is consistent with other published values for mineral dust, including the recent Aerosol Robotic Network retrieval results of Dubovik et al. (2006).

Chou, CDric; Formenti, Paola; Maille, Michel; Ausset, Patrick; Helas, Gnter; Harrison, Mark; Osborne, Simon

2008-12-01

225

Calculating Capstone Depleted Uranium Aerosol Concentrations from Beta Activity Measurements  

Microsoft Academic Search

Beta activity measurements were used as surrogate measurements of uranium mass in aerosol samples collected during the field testing phase of the Capstone Depleted Uranium (DU) Aerosol Study. These aerosol samples generated by the perforation of armored combat vehicles were used to characterize the depleted uranium (DU) source term for the subsequent human health risk assessment (HHRA) of Capstone aerosols.

Frances Szrom; Gerald A. Falo; MaryAnn Parkhurst; Jeffrey J. Whicker; David P. Alberth

2009-01-01

226

Mobile Ambients  

Microsoft Academic Search

There are two distinct areas of work in mobility: mobile computing, concerning computation that is carried out in mobile devices (laptops, personal digital assistants, etc.), and mobile computation, concerning mobile code that moves between devices (applets, agents, etc.). We aim to describe all these aspects of mobility within a single framework that encompasses mobile agents, the ambients where agents interact

Luca Cardelli; Andrew D. Gordon

1998-01-01

227

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

2006-08-01

228

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

229

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

230

Chemical characteristics of aerosols involved in Asian dust of March 2002 collected at Rokkasho Village, Aomori, in northern part of Japan  

Microsoft Academic Search

The Asian dust (Kosa), generated when the surface soil in the arid and semi-arid region of the Asian continental landmass is lifted by winds, is the major mineral aerosol transported from East Asia to the Pacific region. The Kosa particles are thought to be an important factor in the earth_fs climate via radiative forcing. The frequency of dust events giving

N. Akata; H. Hasegawa; H. Kawabata; Y. Chikuchi; Y. Takaku; T. Sato; K. Kondo; J. Inaba

2004-01-01

231

Characterization and source apportionment of aerosol light extinction in Chengdu, southwest China  

NASA Astrophysics Data System (ADS)

To investigate aerosol properties in the Sichuan Basin of China, field aerosol sampling was carried out in Chengdu, China during four one-month periods, each in a different season in 2011. Aerosol scattering coefficient (bsp) at dry (RH<40%) and wet (40% < RH<90%) conditions and aerosol absorption coefficient (bap) were measured. Additionally, daily PM2.5 and PM10 samples were also collected. PM2.5 samples were subject to chemical analysis for various chemical components including major water-soluble ions, organic and elemental carbon (OC and EC), trace elements, as well as anhydrosugar Levoglucosan (LG) and Mannosan (MN). A multiple linear regression analysis was applied to the measured dry bsp against (NH4)2SO4, NH4NO3, organic mass (OM), fine soil (FS), and coarse mass (CM, PM2.5-10), and to the measured bap against EC in all the four seasons to evaluate the impact of individual chemical components of PM2.5 and CM on aerosol light extinction (bext = bsp + bap). Mass scattering efficiency (MSE) and mass absorption efficiency (MAE) of the individual chemical components of PM2.5 were estimated based on seasonal regression equations and were then used for estimating bext. The annual bsp, bap and single scattering albedo (SSA) at dry conditions were 456 237 Mm-1, 96 48 Mm-1 and 0.82 0.05, respectively. The annual average bsp at ambient conditions estimated through hygroscopic curve of aerosol (f(RH)) was 763 415 Mm-1, which was 1.7 times of the dry bsp. The annual average SSA at ambient conditions also increased to 0.88 0.04. The estimated dry bext was only 2 9% higher than the measurements and the estimated ambient bext from individual chemical components was only 1 10% lower, on an annual basis, than that estimated from using f(RH). Secondary inorganic aerosols, coal combustion, biomass burning, iron and steel industry, Mo-related industry, soil dust, and CM to bext were estimated to account for 41 19%, 18 12%, 14 13%, 13 11%, 5 4%, 5 7% and 4 3%, respectively, of the estimated ambient bext.

Tao, Jun; Zhang, Leiming; Cao, Junji; Hsu, Shih-Chieh; Xia, Xiangao; Zhang, Zhisheng; Lin, Zejian; Cheng, Tiantao; Zhang, Renjian

2014-10-01

232

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

233

AEROSOL SOURCE CHARACTERIZATION STUDY IN MIAMI, FLORIDA. MICROSCOPICAL ANALYSIS  

EPA Science Inventory

In June 1975 the U.S. Environmental Protection Agency conducted an experimental program in the Miami metropolitan area to collect atmospheric aerosols for the purpose of identifying aerosol composition and determing aerosol sources. Samples were collected for mass, trace metals, ...

234

Interlaboratory Comparison of Ambient Air Samples  

Microsoft Academic Search

The California Air Resources Board (CARB) has developed a specialized sampling technique to collect ambient air samples that are used to evaluate the relative differences in non-methane hydrocarbon (NMHC) species among Photochemical Assessment Monitoring Station (PAMS) laboratories and toxics species amid toxics laboratories. The sampling system is engineered to simultaneously collect several ambient air samples from a site with historically

Charles L Pearson

235

Near real time vapor detection and enhancement using aerosol adsorption  

DOEpatents

A vapor sample detection method is described where the vapor sample contains vapor and ambient air and surrounding natural background particles. The vapor sample detection method includes the steps of generating a supply of aerosol that have a particular effective median particle size, mixing the aerosol with the vapor sample forming aerosol and adsorbed vapor suspended in an air stream, impacting the suspended aerosol and adsorbed vapor upon a reflecting element, alternatively directing infrared light to the impacted aerosol and adsorbed vapor, detecting and analyzing the alternatively directed infrared light in essentially real time using a spectrometer and a microcomputer and identifying the vapor sample. 13 figs.

Novick, V.J.; Johnson, S.A.

1999-08-03

236

Near real time vapor detection and enhancement using aerosol adsorption  

DOEpatents

A vapor sample detection method where the vapor sample contains vapor and ambient air and surrounding natural background particles. The vapor sample detection method includes the steps of generating a supply of aerosol that have a particular effective median particle size, mixing the aerosol with the vapor sample forming aerosol and adsorbed vapor suspended in an air stream, impacting the suspended aerosol and adsorbed vapor upon a reflecting element, alternatively directing infrared light to the impacted aerosol and adsorbed vapor, detecting and analyzing the alternatively directed infrared light in essentially real time using a spectrometer and a microcomputer and identifying the vapor sample.

Novick, Vincent J. (Downers Grove, IL); Johnson, Stanley A. (Countryside, IL)

1999-01-01

237

Apparatus for sampling and characterizing aerosols  

DOEpatents

Apparatus for sampling and characterizing aerosols having a wide particle size range at relatively low velocities may comprise a chamber having an inlet and an outlet, the chamber including: a plurality of vertically stacked, successive particle collection stages; each collection stage includes a separator plate and a channel guide mounted transverse to the separator plate, defining a labyrinthine flow path across the collection stage. An opening in each separator plate provides a path for the aerosols from one collection stage t

Dunn, P.F.; Herceg, J.E.; Klocksieben, R.H.

1984-04-11

238

Ambient Intelligence: Science or Fad? 1.1. Ambient intelligence: still young at 20 years  

E-print Network

Ambient intelligence concerns the use of emerging technologies for computing, sensing, displaying Advisory Group (ISTAG) put forth its vision of ambient intelligence [STA 03], leading to the creation have also been explored, including collectives of artificial agents for ambient intelligence4

Paris-Sud XI, Université de

239

Tropospheric Aerosols  

NASA Astrophysics Data System (ADS)

It is widely believed that "On a clear day you can see forever," as proclaimed in the 1965 Broadway musical of the same name. While an admittedly beautiful thought, we all know that this concept is only figurative. Aside from Earth's curvature and Rayleigh scattering by air molecules, aerosols - colloidal suspensions of solid or liquid particles in a gas - limit our vision. Even on the clearest day, there are billions of aerosol particles per cubic meter of air.Atmospheric aerosols are commonly referred to as smoke, dust, haze, and smog, terms that are loosely reflective of their origin and composition. Aerosol particles have arisen naturally for eons from sea spray, volcanic emissions, wind entrainment of mineral dust, wildfires, and gas-to-particle conversion of hydrocarbons from plants and dimethylsulfide from the oceans. However, over the industrial period, the natural background aerosol has been greatly augmented by anthropogenic contributions, i.e., those produced by human activities. One manifestation of this impact is reduced visibility (Figure 1). Thus, perhaps more than in other realms of geochemistry, when considering the composition of the troposphere one must consider the effects of these activities. The atmosphere has become a reservoir for vast quantities of anthropogenic emissions that exert important perturbations on it and on the planetary ecosystem in general. Consequently, much recent research focuses on the effects of human activities on the atmosphere and, through them, on the environment and Earth's climate. For these reasons consideration of the geochemistry of the atmosphere, and of atmospheric aerosols in particular, must include the effects of human activities. (201K)Figure 1. Impairment of visibility by aerosols. Photographs at Yosemite National Park, California, USA. (a) Low aerosol concentration (particulate matter of aerodynamic diameter less than 2.5 ?m, PM2.5=0.3 ?g m-3; particulate matter of aerodynamic diameter less than 10 ?m, PM10=1.1 ?g m-3; estimated coefficient of light scattering by particulate matter, ?ep, at 570 nm=12 Mm-1). (b) High aerosol concentration (PM2.5=43.9 ?g m-3; PM10=83.4 ?g m-3; estimated ?ep at 570 nm=245 Mm-1) (reproduced by permission of National Park Service, 2002). Although comprising only a small fraction of the mass of Earth's atmosphere, aerosol particles are highly important constituents of the atmosphere. Special interest has focused on aerosols in the troposphere, the lowest part of the atmosphere, extending from the land or ocean surface typically to 8 km at high latitudes, 12 km in mid-latitudes, and 16 km at low latitudes. That interest arises in large part because of the importance of aerosol particles in geophysical processes, human health impairment through inhalation, environmental effects through deposition, visibility degradation, and influences on atmospheric radiation and climate.Anthropogenic aerosols are thought to exert a substantial influence on Earth's climate, and the need to quantify this influence has sparked much of the current interest in and research on tropospheric aerosols. The principal mechanisms by which aerosols influence the Earth radiation budget are scattering and absorbing solar radiation (the so-called "direct effects") and modifying clouds and precipitation, thereby affecting both radiation and hydrology (the so-called "indirect effects"). Light scattering by aerosols increases the brightness of the planet, producing a cooling influence. Light-absorbing aerosols such as black carbon exert a warming influence. Aerosols increase the reflectivity of clouds, another cooling influence. These radiative influences are quantified as forcings, where a forcing is a perturbation to the energy balance of the atmosphere-Earth system, expressed in units of watts per square meter, W m-2. A warming influence is denoted a positive forcing, and a cooling influence, negative. The radiative direct and indirect forcings by anthropogenic aerosols are thought to be of comparable magnitude to the posi

Buseck, P. R.; Schwartz, S. E.

2003-12-01

240

Elucidating the Chemical Complexity of Organic Aerosol Constituents Measured During the Southeastern Oxidant and Aerosol Study (SOAS)  

NASA Astrophysics Data System (ADS)

Thousands of volatile organic compounds are uniquely created in the atmosphere, many of which undergo chemical transformations that result in more highly-oxidized and often lower vapor pressure species. These species can contribute to secondary organic aerosol, a complex mixture of organic compounds that is still not chemically well-resolved. Organic aerosol collected on filters taken during the Southeastern Oxidant and Aerosol Study (SOAS) constitute hundreds of unique chemical compounds. Some of these include known anthropogenic and biogenic tracers characterized using standardized analytical techniques (e.g. GC-MS, UPLC, LC-MS), but the majority of the chemical diversity has yet to be explored. By employing analytical techniques involving sample derivatization and comprehensive two-dimensional gas chromatography (GC x GC) with high-resolution-time-of-flight mass spectrometry (HR-ToF-MS), we elucidate the chemical complexity of the organic aerosol matrix along the volatility and polarity grids. Further, by utilizing both electron impact (EI) and novel soft vacuum ultraviolet (VUV) ionization mass spectrometry, a greater fraction of the organic mass is fully speciated. The GC x GC-HR-ToF-MS with EI/VUV technique efficiently provides an unprecedented level of speciation for complex ambient samples. We present an extensive chemical characterization and quantification of organic species that goes beyond typical atmospheric tracers in the SOAS samples. We further demonstrate that complex organic mixtures can be chemically deconvoluted by elucidation of chemical formulae, volatility, functionality, and polarity. These parameters provide insight into the sources (anthropogenic vs. biogenic), chemical processes (oxidation pathways), and environmental factors (temperature, humidity), controlling organic aerosol growth in the Southeastern United States.

Yee, L.; Isaacman, G. A.; Spielman, S. R.; Worton, D. R.; Zhang, H.; Kreisberg, N. M.; Wilson, K. R.; Hering, S. V.; Goldstein, A. H.

2013-12-01

241

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

Microsoft Academic Search

Inorganic compounds account for a significant mass of the ambient aerosol. However this contribution varies with time and aerosol size fraction, depending on the influence of source emissions and ambient conditions, which can be relevant in the formation processes of secondary species. Time series of particulate nitrate, 10 m time resolution, have been obtained during the February-March and July 2009

Javier Plaza; Francisco J. Gmez-Moreno; M. Arnzazu Revuelta; Esther Coz; Natalia Moreno; Manuel Pujadas; Begoa. Artano

2010-01-01

242

Aerosol Optical Properties of Smoke from the Las Conchas Wildfire, Los Alamos, NM  

NASA Astrophysics Data System (ADS)

The Las Conchas wildfire in Northern New Mexico started on June, 26 2011 and spread rapidly, eventually burning an area of 634 km2 (245 mi2). Due to the close proximity to the fire, the Los Alamos National Laboratory (LANL) was shut down and the town evacuated for several days. Immediately after LANL reopened (7/6/2011) the Earth and Environmental Sciences Division (EES-14) attained unique measurements of the smoke by sampling the ambient air. Three Integrated Photoacoustic/Nephelometer Spectrometers (DMT Inc.) were set up to measure aerosol light absorption and scattering coefficients. A University of Northwest Switzerland thermodenuder was used to remove compounds that are volatile at temperatures up to 200C. The aerosol's optical properties were measured before and after denuding the sample at 405nm (blue), 532nm (green), 781nm (red), and for non-denuded particles also at 375nm (ultraviolet). The aerosol size distributions were measured after the denuder with a Laser Aerosol Spectrometer (LAS, TSI Inc.) and black carbon was measured with a Single Particle Soot Photometer (SP2, DMT Inc.). Additionally, ambient measurements of Total Particulate Matter (PM2.5 and PM10) were collected continuously at the LANL air monitoring stations. These measurements are used in conjunction with numerical simulations to determine the bulk optical properties of the aerosol. Aerosols in wildfire smoke are composed of organic and black carbon (soot) particles that are formed during wood combustion and pyrolysis. The optical properties of the smoke particles are complex and lead to large uncertainties in assessing the global climate. During the measurement period, the Las Conchas fire provided very high particle concentrations (up to 200 ?g/m3) that were exploited to investigate their optical properties. By heating the particles to temperatures ranging from 75 to 200C in the denuder, volatile organics were removed and the optical properties of the remaining particles were measured. Denuding of the aerosols, removed the outer organic coatings leaving behind the inner core of black carbon (soot) and any compounds that did not volatize completely. By simultaneously measuring the optical properties of the non-denuded as well as the denuded aerosol, we can study how the coatings affect the optical properties. The absorption coefficient measurements showed that coatings can cause an increase or decrease in absorption. The photoacoustic measurements were also combined with SP2 measurements to gain a mechanistic understanding of the effect of composition on the mass light absorption cross-sections of carbonaceous aerosols emitted by fires.

Gorkowski, K.; Dubey, M. K.; Flowers, B. A.; Aiken, A. C.; Klein, B. Z.; Mazzoleni, C.; Sharma, N.; China`, S.

2011-12-01

243

An approach to measure trace elements in particles collected on fiber filters using EDXRF.  

PubMed

A method developed for analyzes of large number of aerosol samples using Energy Dispersive X-Ray Fluorescence (EDXRF) and its performance were discussed in this manuscript. Atmospheric aerosol samples evaluated in this study were collected on cellulose fiber (Whatman-41) filters, employing a Hi-Vol sampler, at a monitoring station located on the Mediterranean coast of Turkey, between 1993 and 2001. Approximately 1700 samples were collected in this period. Six-hundred of these samples were analyzed by instrumental neutron activation (INAA), and the rest were archived. EDXRF was selected as an analytical technique to analyze 1700 aerosol samples because of its speed and non-destructive nature. However, analysis of aerosol samples collected on fiber filters with a surface technique such as EDXRF was a challenge. Penetration depth calculation performed in this study revealed that EDXRF can obtain information from top 150?m of our fiber filter material. Calibration of the instrument with currently available thin film standards caused unsatisfactory results since the actual penetration depth of particles into fiber filters were much deeper than 150?m. A method was developed in this manuscript to analyze fiber filter samples quickly with XRF. Two hundred samples that were analyzed by INAA were divided into two equal batches. One of these batches was used to calibrate the XRF and the second batch was used for verification. The results showed that developed method can be reliably used for routine analysis of fiber samples loaded with ambient aerosol. PMID:21147325

Oztrk, Fatma; Zararsiz, Abdullah; Kirmaz, Ridvan; Tuncel, Grdal

2011-01-15

244

Remote Sensing of Aerosol and Non-Aerosol Absorption  

NASA Technical Reports Server (NTRS)

Remote sensing of aerosol from the new satellite instruments (e.g. MODIS from Terra) and ground based radiometers (e.g. the AERONET) provides the opportunity to measure the absorption characteristics of the ambient undisturbed aerosol in the entire atmospheric column. For example Landsat and AERONET data are used to measure spectral absorption of sunlight by dust from West Africa. Both Application of the Landsat and AERONET data demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards. This is due to difficulties of measuring dust absorption in situ, and due to the often contamination of dust properties by the presence of air pollution or smoke. We use the remotely sensed aerosol absorption properties described by the spectral sin le scattering albedo, together with statistics of the monthly optical thickness for the fine and coarse aerosol derived from the MODIS data. The result is an estimate of the flux of solar radiation absorbed by the aerosol layer in different regions around the globe where aerosol is prevalent. If this aerosol forcing through absorption is not included in global circulation models, it may be interpreted as anomalous absorption in these regions. In a preliminary exercise we also use the absorption measurements by AERONET, to derive the non-aerosol absorption of the atmosphere in cloud free conditions. The results are obtained for the atmospheric windows: 0.44 microns, 0.66 microns, 0.86 microns and 1.05 microns. In all the locations over the land and ocean that were tested no anomalous absorption in these wavelengths, was found within absorption optical thickness of +/- 0.005.

Kaufman, Y. J.; Dubovik, O.; Holben, B. N.; Remer, L. A.; Tanre, D.; Lau, William K. M. (Technical Monitor)

2001-01-01

245

Molecular composition of biogenic secondary organic aerosols using ultrahigh resolution mass spectrometry: comparing laboratory and field studies  

NASA Astrophysics Data System (ADS)

Numerous laboratory experiments have been performed in an attempt to mimic atmospheric secondary organic aerosol (SOA) formation. However, it is still unclear how close the aerosol particles generated in laboratory experiments resemble atmospheric SOA with respect to their detailed chemical composition. In this study, we generated SOA in a simulation chamber from the ozonolysis of ?-pinene and a biogenic volatile organic compound (BVOC) mixture containing ?- and ?-pinene, ?3-carene, and isoprene. The detailed molecular composition of laboratory-generated SOA was compared with that of background ambient aerosol collected at a boreal forest site (Hyytil, Finland) and an urban location (Cork, Ireland) using direct infusion nanoelectrospray ultrahigh resolution mass spectrometry. Kendrick Mass Defect and Van Krevelen approaches were used to identify and compare compound classes and distributions of the detected species. The laboratory-generated SOA contained a distinguishable group of dimers that was not observed in the ambient samples. The presence of dimers was found to be less pronounced in the SOA from the VOC mixtures when compared to the one component precursor system. The elemental composition of the compounds identified in the monomeric region from the ozonolysis of both ?-pinene and VOC mixtures represented the ambient organic composition of particles collected at the boreal forest site reasonably well, with about 70% of common molecular formulae. In contrast, large differences were found between the laboratory-generated BVOC samples and the ambient urban sample. To our knowledge this is the first direct comparison of molecular composition of laboratory-generated SOA from BVOC mixtures and ambient samples.

Kourtchev, I.; Fuller, S. J.; Giorio, C.; Healy, R. M.; Wilson, E.; O'Connor, I. P.; Wenger, J. C.; McLeod, M.; Aalto, J.; Ruuskanen, T. M.; Maenhaut, W.; Jones, R.; Venables, D. S.; Sodeau, J. R.; Kulmala, M.; Kalberer, M.

2013-11-01

246

Mesospheric aerosol sampling spectrometer  

NASA Astrophysics Data System (ADS)

. The Mesospheric Aerosol Sampling Spectrometer (MASS) instrument has been launched on two sounding rockets in August, 2007 from Andoya, Norway to detect charged sub-visible aerosol particles in the polar mesosphere. The MASS instrument is designed to collect charged aerosols, cluster ions, and electrons on four pairs of graphite electrodes, three of which are biased with increasing voltage. The design of the MASS instrument was complicated by the short mean free path in the mesosphere. The opening to MASS was deliberately built to increase the mean free path and to reduce the shock wave within the instrument. The design procedure began with aerodynamics simulations of the flow through the instrument using Direct Simulation Monte Carlo (DSMC) in 3-D. The electric fields within the instrument were calculated using a Laplace solver in 3-D. With the aerodynamic and electric field simulations completed, an algorithm was created to find the trajectories of charged aerosols including collisions within MASS. Using this algorithm the collection efficiencies for each electrode was calculated as a function of the charge to mass ratio of the incoming particle. The simulation results have been confirmed experimentally using an Argon RF ion beam. The data from the August launches have been analyzed and the initial results show the MASS instrument operated as expected. Additional studies are underway to determine if there were effects from payload charging or spurious charge generation within the instrument. This project is supported by NASA.

Knappmiller, Scott; Robertson, Scott; Sternovsky, Zoltan; Horanyi, Mihaly; Kohnert, Rick

247

A Multiphase Study of the Chemical Composition of Air, Aerosol Particles, Snow, and Ice Forms Collected Near Barrow, Alaska Provides Information on Bromine Activation  

NASA Astrophysics Data System (ADS)

Unique chemistry that releases halogens from sea salts into the atmosphere depletes ozone and deposits mercury in the springtime in the Arctic. It is believed that Br(-) is present in the snow pack and other ice reservoirs over the ice-covered ocean during winter, and is liberated by poorly understood chemistry in the springtime. We undertook a study of halogens in different ice reservoirs like snow, aerosol particles, and in the gas phase in the vicinity of Barrow, Alaska in the springtime of 2007. For the first time, we observed a time series of most of the relevant bromine reservoirs simultaneously. The size and time-resolved aerosol data help us to complete a picture of what ice reservoirs are involved in releasing Br(-) into the gas phase. The smallest particles sampled with a 3-stage DRUM impactor contain a larger fraction of sulfate than the larger particles, and probably are the result of Arctic Haze sulfate pollution overlaid on a background of mostly larger sea-salt particles. The smallest particles are mostly enhanced in Br(-) (as compared to sea salt reference) while larger-sized particles could show near sea-salt Br(-) enrichment factors or slight Br- depletions. Enhancement in Br(-) can come from termination of halogen activation chemistry, which produces HBr. These HBr molecules would then be scavenged efficiently by the smaller particles due to their high surface area, which is consistent with our data. Depletion of Br(-) indicates halogen activation to the gas phase. During halogen activation events, surface snow shows higher depletions than the aerosol particles. Because the surface snow received its salts from the sea-salt aerosol that is mostly enhanced in Br(-) or is comparable to sea salt, and we observe depletions in snow, this indicates that snowpack is releasing halogens to the atmosphere. Knowing what ice surfaces contribute more to active Br(-) species can help us to predict ozone depletion and mercury deposition events. This mechanistic understanding is needed to make meaningful predictions of how Arctic pollution and Arctic atmospheric chemistry will respond to the drastic changes in sea ice.

Alvarez-Aviles, L.; Simpson, W. R.; Carlson, D. A.; Sturm, M.; Douglas, T. A.; Laskin, A.

2007-12-01

248

Estimating marine aerosol particle volume and number from Maritime Aerosol Network data  

NASA Astrophysics Data System (ADS)

As well as spectral aerosol optical depth (AOD), aerosol composition and concentration (number, volume, or mass) are of interest for a variety of applications. However, remote sensing of these quantities is more difficult than for AOD, as it is more sensitive to assumptions relating to aerosol composition. This study uses spectral AOD measured on Maritime Aerosol Network (MAN) cruises, with the additional constraint of a microphysical model for unpolluted maritime aerosol based on analysis of Aerosol Robotic Network (AERONET) inversions, to estimate these quantities over open ocean. When the MAN data are subset to those likely to be comprised of maritime aerosol, number and volume concentrations obtained are physically reasonable. Attempts to estimate surface concentration from columnar abundance, however, are shown to be limited by uncertainties in vertical distribution. Columnar AOD at 550 nm and aerosol number for unpolluted maritime cases are also compared with Moderate Resolution Imaging Spectroradiometer (MODIS) data, for both the present Collection 5.1 and forthcoming Collection 6. MODIS provides a best-fitting retrieval solution, as well as the average for several different solutions, with different aerosol microphysical models. The "average solution" MODIS dataset agrees more closely with MAN than the "best solution" dataset. Terra tends to retrieve lower aerosol number than MAN, and Aqua higher, linked with differences in the aerosol models commonly chosen. Collection 6 AOD is likely to agree more closely with MAN over open ocean than Collection 5.1. In situations where spectral AOD is measured accurately, and aerosol microphysical properties are reasonably well-constrained, estimates of aerosol number and volume using MAN or similar data would provide for a greater variety of potential comparisons with aerosol properties derived from satellite or chemistry transport model data.

Sayer, A. M.; Smirnov, A.; Hsu, N. C.; Munchak, L. A.; Holben, B. N.

2012-06-01

249

Estimating marine aerosol particle volume and number from Maritime Aerosol Network data  

NASA Astrophysics Data System (ADS)

As well as spectral aerosol optical depth (AOD), aerosol composition and concentration (number, volume, or mass) are of interest for a variety of applications. However, remote sensing of these quantities is more difficult than for AOD, as it is more sensitive to assumptions relating to aerosol composition. This study uses spectral AOD measured on Maritime Aerosol Network (MAN) cruises, with the additional constraint of a microphysical model for unpolluted maritime aerosol based on analysis of Aerosol Robotic Network (AERONET) inversions, to estimate these quantities over open ocean. When the MAN data are subset to those likely to be comprised of maritime aerosol, number and volume concentrations obtained are physically reasonable. Attempts to estimate surface concentration from columnar abundance, however, are shown to be limited by uncertainties in vertical distribution. Columnar AOD at 550 nm and aerosol number for unpolluted maritime cases are also compared with Moderate Resolution Imaging Spectroradiometer (MODIS) data, for both the present Collection 5.1 and forthcoming Collection 6. MODIS provides a best-fitting retrieval solution, as well as the average for several different solutions, with different aerosol microphysical models. The "average solution" MODIS dataset agrees more closely with MAN than the "best solution" dataset. Terra tends to retrieve lower aerosol number than MAN, and Aqua higher, linked with differences in the aerosol models commonly chosen. Collection 6 AOD is likely to agree more closely with MAN over open ocean than Collection 5.1. In situations where spectral AOD is measured accurately, and aerosol microphysical properties are reasonably well-constrained, estimates of aerosol number and volume using MAN or similar data would provide for a greater variety of potential comparisons with aerosol properties derived from satellite or chemistry transport model data. However, without accurate AOD data and prior knowledge of microphysical properties, such attempts are fraught with high uncertainties.

Sayer, A. M.; Smirnov, A.; Hsu, N. C.; Munchak, L. A.; Holben, B. N.

2012-09-01

250

Exposure of acid aerosol for schoolchildren in metropolitan Taipei  

NASA Astrophysics Data System (ADS)

Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO 2, SO 2, HNO 3, NO 3-, SO 42-, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 ?g m -3, 18.5 ?g m -3, and 49.5 nmol m -3 in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 ?g m -3, 8.8 ?g m -3 and 14.7 nmol m -3 in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO 2 levels were low (0.13-8.03 ppb) in the metropolitan Taipei. However, the SO 42- concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed.

Mao, I.-Fang; Lin, Chih-Hung; Lin, Chun-Ji; Chen, Yi-Ju; Sung, Fung-Chang; Chen, Mei-Lien

251

Modeling of growth and evaporation effects on the extinction of 1.0-micron solar radiation traversing stratospheric sulfuric acid aerosols  

NASA Technical Reports Server (NTRS)

The effects of growth and evaporation of stratospheric sulfuric acid aerosols on the extinction of solar radiation traversing such an aerosol medium are reported for the case of 1.0-micron solar radiation. Modeling results show that aerosol extinction is not very sensitive to the change of ambient water vapor concentration, but is sensitive to ambient temperature changes, especially at low ambient temperatures and high ambient water vapor concentration. A clarification is given of the effects of initial aerosol size distribution and composition on the change of aerosol extinction due to growth and evaporation processes. It is shown that experiments designed to observe solar radiation extinction of aerosols may also be applied to the determination of observed changes in aerosol optical properties, environmental parameters, or the physical and optical characteristics of sulfate aerosols.

Yue, G. K.; Deepak, A.

1981-01-01

252

Aerosol Optical Depth Measurements in the Southern Ocean Within the Framework of Maritime Aerosol Network  

NASA Astrophysics Data System (ADS)

Aerosol production sources over the World Ocean and various factors determining aerosol spatial and temporal distribution are important for understanding the Earth's radiation budget and aerosol-cloud interactions. The Maritime Aerosol Network (MAN) as a component of AERONET has been collecting aerosol optical depth data over the oceans since 2006. A significant progress has been made in data acquisition over areas that previously had very little or no coverage. Data collection included intensive study areas in the Southern Ocean and off the coast of Antarctica including a number of circumnavigation cruises in high southern latitudes. It made an important contribution to MAN and provided a valuable reference point in atmospheric aerosol optical studies. The paper presents results of this international and multi-agency effort in studying aerosol optical properties over Southern Ocean and adjacent areas. The ship-borne aerosol optical depth measurements offer an excellent opportunity for comparison with global aerosol transport models, satellite retrievals and provide useful information on aerosol distribution over the World Ocean. A public domain web-based database dedicated to the MAN activity can be found at http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html.

Smirnov, A.; Holben, B. N.; Sayer, A. M.; Sakerin, S. M.; Radionov, V. F.; Courcoux, Y.; Broccardo, S. P.; Evangelista, H.; Croot, P. L.; Disterhoft, P.; Piketh, S.; Milinevsky, G. P.; O'Neill, N. T.; Slutsker, I.; Giles, D. M.

2013-12-01

253

Consistency of Global Modis Aerosol Optical Depths over Ocean on Terra and Aqua Ceres SSF Datasets  

NASA Technical Reports Server (NTRS)

Aerosol retrievals over ocean from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua platforms are available from the Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) datasets generated at NASA Langley Research Center (LaRC). Two aerosol products are reported side-by-side. The primary M product is generated by sub-setting and remapping the multi-spectral (0.47-2.1 micrometer) MODIS produced oceanic aerosol (MOD04/MYD04 for Terra/Aqua) onto CERES footprints. M*D04 processing uses cloud screening and aerosol algorithms developed by the MODIS science team. The secondary AVHRR-like A product is generated in only two MODIS bands 1 and 6 (on Aqua, bands 1 and 7). The A processing uses the CERES cloud screening algorithm, and NOAA/NESDIS glint identification, and single-channel aerosol retrieval algorithms. The M and A products have been documented elsewhere and preliminarily compared using 2 weeks of global Terra CERES SSF Edition 1A data in which the M product was based on MOD04 collection 3. In this study, the comparisons between the M and A aerosol optical depths (AOD) in MODIS band 1 (0.64 micrometers), tau(sub 1M) and tau(sub 1A) are re-examined using 9 days of global CERES SSF Terra Edition 2A and Aqua Edition 1B data from 13 - 21 October 2002, and extended to include cross-platform comparisons. The M and A products on the new CERES SSF release are generated using the same aerosol algorithms as before, but with different preprocessing and sampling procedures, lending themselves to a simple sensitivity check to non-aerosol factors. Both tau(sub 1M) and tau(sub 1A) generally compare well across platforms. However, the M product shows some differences, which increase with ambient cloud amount and towards the solar side of the orbit. Three types of comparisons conducted in this study - cross-platform, cross-product, and cross-release confirm the previously made observation that the major area for improvement in the current aerosol processing lies in a more formalized and standardized sampling (and most importantly, cloud screening) whereas optimization of the aerosol algorithm is deemed to be an important yet less critical element.

Ignatov, Alexander; Minnis, Patrick; Miller, Walter F.; Wielicki, Bruce A.; Remer, Lorraine

2006-01-01

254

Mesospheric Aerosol Sampling Spectrometer  

NASA Astrophysics Data System (ADS)

An instrument has been developed to detect charged, sub-visible aerosol particles in the polar mesosphere. Two of these instruments were launched in August, 2007 from Andoya, Norway as part of the Mesospheric Aerosol Sampling Spectrometer (MASS) campaign and both detected charged aerosols. These in-situ measurements coincided with measurements by the Aeronomy of Ice in the Mesosphere (AIM) satellite and the German/Norwegian Existence and Charge state Of Meteoric dust grains in the middle Atmosphere (ECOMA) rocket campaign. This instrument has a 25 square centimeter entrance slit that admits a continuous flow of air. Venting ports are placed lower on the detector in order to reduce pressure buildup. The air sample flows between three pairs of graphite electrodes biased symmetrically with increasing bias potentials. Electrons, light ions, cluster ions and heavy charged aerosol particles of both polarities are collected mass-selectively on the electrodes that are connected to sensitive electrometers. Direct Simulation Monte Carlo (DSMC) codes have been used to optimize the supersonic airflow within and around the instrument. The calibration of the MASS instrument as well as preliminary results will be shown. Acknowledgement: This project is supported by NASA.

Knappmiller, S.; Robertson, S.; Horanyi, M.; Kohnert, R.; Sternovsky, Z.; Baumgarten, G.; Latteck, R.; Rapp, M.

2007-12-01

255

Comparison of dicarboxylic acids and related compounds in aerosol samples collected in Xi'an, China during haze and clean periods  

NASA Astrophysics Data System (ADS)

PM10 aerosols from Xi'an, a mega city of China in winter and summer, 2009 were measured for secondary organic aerosols (SOA) (i.e., dicarboxylic acids (DCA), keto-carboxylic acids, and ?-dicarbonyls), water-soluble organic (WSOC) and inorganic carbon (WSIC), elemental carbon (EC) and organic carbon (OC). Molecular compositions of SOA on haze and clean days in both seasons were compared to investigate their sources and formation mechanisms. DCA in the samples were 1843 810 ng m-3 in winter and 1259 781 ng m-3 in summer, respectively, which is similar and even higher than those measured in 2003. Oxalic acid (C2, 1162 570 ng m-3 in winter and 1907 707 ng m-3 in summer) is the predominant species of DCA, followed by t-phthalic (tPh) in winter and phthalic (Ph) in summer. Such a molecular composition is different from those in other Asian cities where succinic acid (C4) or malonic acid (C3) is the second highest species, which is mostly due to significant emissions from household combustion of coal and open burning of waste material in Xi'an. Mass ratios of C2/diacids, diacids/WSOC, WSOC/OC and individual diacid-C/WSOC are higher on the haze days than on the clean days in both seasons, suggesting an enhanced SOA production under the haze condition. We also found that the haze samples are acidic while the clean samples are almost neutral. Such a difference in particle acidity is consistent with the enhanced SOA production, because acid-catalysis is an important aqueous-phase formation pathway of SOA. Gly/mGly mass ratio showed higher values on haze days than on clean day in both seasons. We comprehensively investigated the ratio in literature and found a consistent pattern. Based on our observation results and those documented data we proposed for the first time that concentration ratio of Gly/mGly can be taken as an indicator of aerosol ageing.

Cheng, Chunlei; Wang, Gehui; Zhou, Bianhong; Meng, Jingjing; Li, Jianjun; Cao, Junji; Xiao, Shun

2013-12-01

256

Remote sensing of aerosol properties over oceans using the MODIS\\/EOS spectral radiances  

Microsoft Academic Search

Spectral radiances measured at the top of the atmosphere in a wide spectral range (0.55-2.13mum) are used to monitor the aerosol optical thickness and the aerosol size distribution (integrated on the vertical column) of the ambient (undisturbed) aerosol over the oceans. Even for the moderate resolution imaging spectrometer (MODIS) wide spectral range, only three parameters that describe the aerosol loading

D. Tanr; Y. J. Kaufman; M. Herman; S. Mattoo

1997-01-01

257

Attachment of radon progeny to cigarette-smoke aerosols  

SciTech Connect

The daughter products of radon gas are now recognized as a significant contributor to radiation exposure to the general public. It is also suspected that a synergistic effect exists with the combination cigarette smoking and radon exposure. We have conducted an experimental investigation to determine the physical nature of radon progeny interactions with cigarette smoke aerosols. The size distributions of the aerosols are characterized and attachment rates of radon progeny to cigarette-smoke aerosols are determined. Both the mainstream and sidestream portions of the smoke aerosol are investigated. Unattached radon progeny are very mobile and, in the presence of aerosols, readily attach to the particle surfaces. In this study, an aerosol chamber is used to contain the radon gas, progeny and aerosol mixture while allowing the attachment process to occur. The rate of attachment is dependent on the size distribution, or diffusion coefficient, of the radon progeny as well as the aerosol size distribution. The size distribution of the radon daughter products is monitored using a graded-screen diffusion battery. The diffusion battery also enables separation of the unattached radon progeny from those attached to the aerosol particles. Analysis of the radon decay products is accomplished using alpha spectrometry. The aerosols of interest are size fractionated with the aid of a differential mobility analyzer and cascade impactor. The measured attachment rates of progeny to the cigarette smoke are compared to those found in similar experiments using an ambient aerosol. The lowest attachment coefficients observed, {approximately}10{sup {minus}6} cm{sup 3}/s, occurred for the ambient aerosol. The sidestream and mainstream smoke aerosols exhibited higher attachment rates in that order. The results compared favorably with theories describing the coagulation process of aerosols.

Biermann, A.H.; Sawyer, S.R.

1995-05-01

258

METHODS OF CALCULATINAG LUNG DELIVERY AND DEPOSITION OF AEROSOL PARTICLES  

EPA Science Inventory

Lung deposition of aerosol is measured by a variety of methods. Total lung deposition can be measured by monitoring inhaled and exhaled aerosols in situ by laser photometry or by collecting the aerosols on filters. The measurements can be performed accurately for stable monod...

259

Molecular composition of biogenic secondary organic aerosols using ultrahigh-resolution mass spectrometry: comparing laboratory and field studies  

NASA Astrophysics Data System (ADS)

Numerous laboratory experiments have been performed in an attempt to mimic atmospheric secondary organic aerosol (SOA) formation. However, it is still unclear how close the aerosol particles generated in laboratory experiments resemble atmospheric SOA with respect to their detailed chemical composition. In this study, we generated SOA in a simulation chamber from the ozonolysis of ?-pinene and a biogenic volatile organic compound (BVOC) mixture containing ?- and ?-pinene, ?3-carene, and isoprene. The detailed molecular composition of laboratory-generated SOA was compared with that of background ambient aerosol collected at a boreal forest site (Hyytil, Finland) and an urban location (Cork, Ireland) using direct infusion nanoelectrospray ultrahigh-resolution mass spectrometry. Kendrick mass defect and van Krevelen approaches were used to identify and compare compound classes and distributions of the detected species. The laboratory-generated SOA contained a distinguishable group of dimers that was not observed in the ambient samples. The presence of dimers was found to be less pronounced in the SOA from the BVOC mixtures when compared to the one component precursor system. The molecular composition of SOA from both the BVOC mixture and ?-pinene represented the overall composition of the ambient sample from the boreal forest site reasonably well, with 72.3 2.5% (n = 3) and 69.1 3.0% (n = 3) common ions, respectively. In contrast, large differences were found between the laboratory-generated BVOC samples and the ambient urban sample. To our knowledge this is the first direct comparison of molecular composition of laboratory-generated SOA from BVOC mixtures and ambient samples.

Kourtchev, I.; Fuller, S. J.; Giorio, C.; Healy, R. M.; Wilson, E.; O'Connor, I.; Wenger, J. C.; McLeod, M.; Aalto, J.; Ruuskanen, T. M.; Maenhaut, W.; Jones, R.; Venables, D. S.; Sodeau, J. R.; Kulmala, M.; Kalberer, M.

2014-02-01

260

Organosulfate Formation in Biogenic Secondary Organic Aerosol  

EPA Science Inventory

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

261

AERODYNAMIC CLASSIFICATION OF FIBERS WITH AEROSOL CENTRIFUGES  

EPA Science Inventory

The constituent particles of many ambient and workplace aerosols of health effects concerns are of fibrous and aggregate geometric shapes. he sites of deposition in the human respiratory system are primarily related to the mass median aerodynamic diameters of inhaled particle siz...

262

Apparatus for sampling and characterizing aerosols  

DOEpatents

Apparatus for sampling and characterizing aerosols having a wide particle size range at relatively low velocities may comprise a chamber having an inlet and an outlet, the chamber including: a plurality of vertically stacked, successive particle collection stages; each collection stage includes a separator plate and a channel guide mounted transverse to the separator plate, defining a labyrinthine flow path across the collection stage. An opening in each separator plate provides a path for the aerosols from one collection stage to the next. Mounted within each collection stage are one or more particle collection frames.

Dunn, Patrick F. (Downers Grove, IL); Herceg, Joseph E. (Naperville, IL); Klocksieben, Robert H. (Park Forest, IL)

1986-01-01

263

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

NASA Astrophysics Data System (ADS)

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). This enabled a more detailed source attribution of the carbonaceous aerosol mass than is possible with other currently available methods. The three major sources, fossil fuel, wood combustion (both anthropogenic emissions), and biogenic emissions, were quantified, making specific regulatory air quality management measures possible. EC originates nearly exclusively from fossil fuel usage during summer, whereas biomass-burning emissions become substantial during winter with 25%, even though this source contributes only marginally to the local energy consumption. For OC, biogenic sources are dominant in summer with 60%, where secondary organic aerosol prevails. Wood combustion accounts for up to 41% of OC in winter. Fossil fuels represent 30% of OC throughout the year.

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

2006-04-01

264

Aerosol volatility in a boreal forest environment  

NASA Astrophysics Data System (ADS)

Climate and health effects of atmospheric aerosols are determined by their properties such as their chemical composition. Aerosol chemical composition can be studied indirectly by measuring volatility of aerosol particles. The volatility of submicron aerosol particles (20-500 nm) was studied in a boreal forest site at SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations II) station (Vesala et al., 1998) in Hyytil, Finland, during 01/2008-05/2010. The instrument used for the measurements was VDMPS (Volatility Differential Mobility Particle Sizer), which consists of two separate instruments: DMPS (Differential Mobility Particle Sizer, Aalto et al., 2001) and TD (Thermodenuder, Wehner et al., 2002). Aerosol evaporation was examined by heating the aerosol and comparing the total aerosol mass before and after heating. In the VDMPS system ambient aerosol sample was heated up to temperatures ranging from 80 C to 280 C. The higher the heating temperature was the more aerosol material was evaporated. There was a non-volatile residual present in aerosol particles when heated up to 280 C. This residual explained (208)% of the total aerosol mass. Aerosol non-volatile mass fraction was highest during winter and smallest during summer months. The role of black carbon in the observed non-volatile residual was determined. Black carbon explained 40 to 90% of the non-volatile mass. Especially during colder seasons noticeable amount of non-volatile material, something else than black carbon, was observed. According to Kalberer et al. (2004) some atmospheric organic species can form polymers that have high evaporation temperatures. Also low-volatile organic salts may contribute to the non-volatile aerosol (Smith et al., 2010). Aerosol mass composition measured directly with AMS (Aerosol Mass Spectrometer, Jayne et al., 2000) was analyzed in order to examine the properties of the non-volatile material (other than black carbon). The AMS measurements were performed during spring and autumn 2008. Results from the aerosol mass spectrometry indicate that the non-volatile residual consists of nitrate and organic compounds, especially during autumn. These compounds may be low-volatile organic nitrates or salts. During winter and spring the non-volatile core (black carbon removed) correlated markedly with carbon monoxide, which is a tracer of anthropogenic emissions. Due to this, the non-volatile residual may also contain other pollutants in addition to black carbon. Thus, it seems that the amount of different compounds in submicron aerosol particles varies with season and as a result the chemical composition of the non-volatile residual changes within a year. This work was supported by University of Helsinki three-year research grant No 490082 and Maj and Tor Nessling Foundation grant No 2010143. Aalto et al., (2001). Physical characterization of aerosol particles during nucleation events. Tellus B, 53, 344-358. Jayne, et al., (2000). Development of an aerosol mass spectrometer for size and composition analysis of submicron particles. Aerosol Sci. Technol., 33(1-2), 49-70. Kalberer et al., (2004). Identification of Polymers as Major Components of Atmospheric Organic Aerosols. Science, 303, 1659-1662. Smith et al., (2010). Observations of aminium salts in atmospheric nanoparticles and possible climatic implications. P. Natl. Acad. Sci., 107(15). Vesala et al., (1998). Long-term field measurements of atmosphere-surface interactions in boreal forest combining forest ecology, micrometeorology, aerosol physics and atmospheric chemistry. Trends Heat, Mass Mom. Trans., 4, 17-35. Wehner et al., (2002). Design and calibration of a thermodenuder with an improved heating unit to measure the size-dependent volatile fraction of aerosol particles. J. Aerosol Sci., 33, 1087-1093.

Hkkinen, S. A. K.; ?ijl, M.; Lehtipalo, K.; Junninen, H.; Virkkula, A.; Worsnop, D. R.; Kulmala, M.; Petj, T.; Riipinen, I.

2012-04-01

265

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

PubMed

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

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

2014-05-01

266

Analysis of Aerosol Mass Spectrometer Data in Pittsburgh, Mexico City, and Blodgett Forest by Positive Matrix Factorization  

NASA Astrophysics Data System (ADS)

Mass spectrometric measurements of ambient aerosols yield organic spectra that are a mix of nucleated particles, freshly emitted particles from many sources, and particles which have undergone some amount of processing (condensation, oxidative reaction, cloud processing, etc.). Further understanding of the important sources and processes for organic aerosols requires deconvolution of the organic fraction of ambient aerosols. A well-known source apportionment technique, Positive Matrix Factorization (PMF), has been applied to Aerodyne aerosol mass spectrometer (Q-AMS and HR-ToF-AMS) datasets acquired in Pittsburgh (2002), Mexico City (2003), Blodgett Forest (2007) and other sites. Sensitivity analysis of the Pittsburgh case is performed with synthetic datasets and characterizes the behaviour of PMF with AMS datasets. PMF is a least-squares fitting method for source apportionment commonly applied to speciated aerosol datasets (Paatero, Chemomet. Intell. Lab. Sys. 1997, 37, 23-35). The structure and precision of the AMS dataset are significantly different from datasets compiled from previous measurements of multiple aerosol components (metals, organic and elemental carbon, ions, etc.), are very large (~300 points per sample, with ~3000-10,000 samples for these campaigns), and fragmentation of molecules during ionization gives each mass spectrum strongly interrelated data. Additionally, because the Aerodyne AMS does not detect elemental carbon or metals (common and important in most PMF analyses), application of this technique to AMS data yields significantly different source profiles than in previous PMF studies. Each site has a hydrocarbon-like organic aerosol (HOA) factor that is likely primary OA and multiple oxygenated organic aerosol (OOA) factors that are likely secondary OA, and biomass burning organic aerosol (BBOA) can be separated in some locations. The OOA factors always include one highly-oxygenated factor (OOA-I) that resembles the spectrum of fulvic acid and less-oxygenated factors that resemble spectra from chamber studies of SOA. Assignment of factor spectra to these categories is aided by comparison to spectra collected by many research groups using the Aerodyne AMS to measure individual compounds, reactions in smog chambers, and primary emission sources. These spectra have been compiled in a publicly-available database (http://cires.colorado.edu/jimenez-group/AMSsd/spectra.html).

Ulbrich, I. M.; Zhang, Q.; Canagaratna, M.; Salcedo, D.; Dzepina, K.; Farmer, D.; Docherty, K.; Worsnop, D. R.; Jimenez, J. L.

2007-12-01

267

Maritime Aerosol Network as a component of Aerosol Robotic Network  

NASA Astrophysics Data System (ADS)

The paper presents the current status of the Maritime Aerosol Network (MAN), which has been developed as a component of the Aerosol Robotic Network (AERONET). MAN deploys Microtops handheld Sun photometers and utilizes the calibration procedure and data processing (Version 2) traceable to AERONET. A web site dedicated to the MAN activity is described. A brief historical perspective is given to aerosol optical depth (AOD) measurements over the oceans. A short summary of the existing data, collected on board ships of opportunity during the NASA Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project is presented. Globally averaged oceanic aerosol optical depth (derived from island-based AERONET measurements) at 500 nm is 0.11 and Angstrom parameter (computed within spectral range 440-870 nm) is calculated to be 0.6. First results from the cruises contributing to the Maritime Aerosol Network are shown. MAN ship-based aerosol optical depth compares well to simultaneous island and near-coastal AERONET site AOD.

Smirnov, A.; Holben, B. N.; Slutsker, I.; Giles, D. M.; McClain, C. R.; Eck, T. F.; Sakerin, S. M.; Macke, A.; Croot, P.; Zibordi, G.; Quinn, P. K.; Sciare, J.; Kinne, S.; Harvey, M.; Smyth, T. J.; Piketh, S.; Zielinski, T.; Proshutinsky, A.; Goes, J. I.; Nelson, N. B.; Larouche, P.; Radionov, V. F.; Goloub, P.; Krishna Moorthy, K.; Matarrese, R.; Robertson, E. J.; Jourdin, F.

2009-03-01

268

Selected water-soluble organic compounds found in size-resolved aerosols collected from urban, mountain and marine atmospheres over East Asia  

NASA Astrophysics Data System (ADS)

Primary (i.e. sugars and sugar-alcohols) and secondary (i.e. carboxylic acids) water-soluble organic compounds (WSOCs) in size-segregated aerosols from the urban and mountain atmosphere of China and from the marine atmosphere in the outflow region of East Asia were characterized on a molecular level. Levoglucosan is the most abundant compound among the quantified WSOCs in the urban and mountain atmosphere, whose concentration at the urban site was 1-2 orders of magnitude higher than that at the mountain and marine sites. In contrast, malic, succinic and phthalic acids were dominant among the measured WSOCs at the marine site. In the urban air, sugars except levoglucosan gave a bimodal size distribution with a large peak in fine range (<2.1 ?m) and a small peak in coarse range (?2.1 ?m) during winter, being opposite to those in spring. In contrast, these WSOCs at the mountain and marine sites dominated in the coarse range but diminished and even disappeared in the fine range. Geometric mean diameters (GMDs) of the measured WSOCs in the fine mode at the urban site were larger in winter than in spring. Levoglucosan and carboxylic acids except for azelaic and benzoic acids showed a larger GMD in the coarse mode at the marine site probably due to an increased hygroscopic growth.

Wang, Gehui; Kawamura, Kimitaka; Xie, Mingjie; Hu, Shuyuan; Li, Jianjun; Zhou, Bianhong; Cao, Junji; An, Zhisheng

2011-07-01

269

Investigating the CCN Activation Kinetics of Aerosol in Arctic Haze and Canadian Boreal Forest Fires  

NASA Astrophysics Data System (ADS)

It has long been hypothesized that the existence of (organic) hydrophobic films and slowly-dissolving compounds may impact the droplet activation kinetics of ambient Cloud Condensation Nuclei (CCN). This compositional effect on droplet formation may have an important impact on droplet number and size distribution, but is largely unconstrained to date. Measurements with a continuous flow CCN instrument that sizes the activated droplets can be used to identify whether composition affects droplet activation kinetics. The method used, termed Threshold Droplet Growth Analysis (TDGA) looks for evidence of delayed growth kinetics by comparing the droplet sizes of activated ambient particles against a standard that represents CCN with rapid activation kinetics. The standard we use is ammonium sulfate particles activated at a critical supersaturation equal to that of the instrument (for the same flow/temperature conditions as in the ambient measurements). This standard provides the smallest droplet size possible that corresponds to rapid activation kinetics. Particles with lower critical supersaturation will activate earlier in the instrument and grow to larger sizes than the standard, while particles with higher critical supersaturation will not activate and remain undetected. If ambient particles form droplets smaller than the calibration aerosol over the measured range of supersaturation, the ambient aerosol is said to exhibit kinetic limitations (delayed droplet growth). We apply TDGA on CCN activation data collected for Arctic haze and Canadian boreal forest fires sampled during the 2008 NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) campaign. Within biomass burning plumes, we find evidence of significant kinetic limitations coincident with high organic mass fractions. In the Arctic, where organic mass fractions are lower and the air masses are more aged, we find little to no kinetic limitations. To further explore the influence of organics, we infer an optimum water vapor uptake coefficient by explicitly simulating the observed activated droplet distribution using the measured aerosol size distributions and chemical composition. This water vapor uptake coefficient is then correlated with aerosol properties to gain insight on the mechanisms responsible for creating and controlling CCN activation kinetics.

Lathem, T. L.; Nenes, A.; Moore, R.; Anderson, B.; Beyersdorf, A. J.; Thornhill, K. L.; Winstead, E. L.; Cubison, M.; Jimenez, J. L.; Weber, R.; Hecobian, A.; Clarke, A. D.; McNaughton, C. S.; Howell, S.

2009-12-01

270

Exposures to acidic aerosols  

SciTech Connect

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/cu m 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/cu m (approximately 27 microgram/cu m H{sub 2}SO{sub 4}). The maximum estimated 1-hr concentration exceeded 1500 nmole/cu m 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 H{sub 2}SO{sub 4} exceeded 50 microgram/cu m.

Spengler, J.D.; Keeler, G.J.; Koutrakis, P.; Ryan, P.B.; Raizenne, M.

1989-01-01

271

Exposures to acidic aerosols  

SciTech Connect

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/m/sup 3/ 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/m/sup 3/ (approximately 27 micrograms/m/sup 3/ H/sub 2/SO/sub 4/). The maximum estimated 1-hr concentration exceeded 1500 nmole/m/sup 3/ 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 H/sub 2/SO/sub 4/ exceeded 50 micrograms/m/sup 3/.

Spengler, J.D.; Keeler, G.J.; Koutrakis, P.; Ryan, P.B.; Raizenne, M.; Franklin, C.A.

1989-02-01

272

Aerosol Impacts on Microphysical and Radiative Properties of Stratocumulus Clouds in the Southeast Pacific  

NASA Astrophysics Data System (ADS)

The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, cloud droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties along an E-W track from near the Chilean coast to remote areas offshore. Mean statistics from seven flights were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. The effect extends ~800 to 1000 km from shore. The additional particles are mainly sulfates from anthropogenic sources. Liquid water content and drizzle concentration tended to increase with distance from shore, but exhibited much greater variability. Analysis of the droplet residual measurements showed that not only were there more residual nuclei near shore, but that they tended to be larger than those offshore. Single particle analysis over a broad particle size range was used to reveal types and sources of CCN, which were primarily sulfates near shore. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed due to the preferential activation of large aerosol particles. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, which initiate drizzle, contain the largest aerosol particles. However, the scavenging efficiency is not sharp as expected from a simple parcel activation model. A wide range of particle sizes, down to at least 55 nm in size, act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show this can occur without invoking differences in chemical composition. Aerosol number concentration in the >0.05 and >0.1 ?m size ranges was correlated with droplet number concentration, and anti-correlated with droplet effective radius, and the effect is statistically significant. The impact of aerosol pollutants was to increase droplet number and decrease droplet size within a region extending about 1000 km offshore. Cloud droplets were more numerous and smaller near shore, and there was less drizzle. However, MODIS satellite measurements were used to show that despite the smaller droplets near shore, cloud albedo is not higher near shore than offshore. This is due to the generally thinner clouds and lower liquid water path near shore.

Twohy, C. H.; Toohey, D. W.; Andrejczuk, M.; Anderson, J. R.; Adams, A.; Lytle, M.; George, R.; Wood, R.; Zuidema, P.; Leon, D.

2011-12-01

273

Capstone Depleted Uranium Aerosols: Generation and Characterization  

SciTech Connect

In a study designed to provide an improved scientific basis for assessing possible health effects from inhaling depleted uranium (DU) aerosols, a series of DU penetrators was fired at an Abrams tank and a Bradley fighting vehicle. A robust sampling system was designed to collect aerosols in this difficult environment and continuously monitor the sampler flow rates. Aerosols collected were analyzed for uranium concentration and particle size distribution as a function of time. They were also analyzed for uranium oxide phases, particle morphology, and dissolution in vitro. The resulting data provide input useful in human health risk assessments.

Parkhurst, MaryAnn; Szrom, Fran; Guilmette, Ray; Holmes, Tom; Cheng, Yung-Sung; Kenoyer, Judson L.; Collins, John W.; Sanderson, T. Ellory; Fliszar, Richard W.; Gold, Kenneth; Beckman, John C.; Long, Julie

2004-10-19

274

Photoformation Rate of OH radical in Water-Extract of Atmospheric Aerosol and Water-Soluble Gases Collected in Higashi-Hiroshima, Japan  

NASA Astrophysics Data System (ADS)

The hydroxyl radical (?OH) photoformation rate (ROH), chemical composition and primary generation sources of ?OH in the atmospheric water-extract of aerosol (WEA) and water-soluble gaseous (WSG) fractions were studied at Higashi-Hiroshima from June 2008 to June 2010. Among the major anions being present in the WSG samples, the SO42- concentration was highest (9.82.9 nmol m-3), followed by NO3- and Cl-, while for WEA fractions the mean concentration of SO42- was 8133 nmol m-3. The concentration of H2O2 was 0.20.3 and 0.92.3 nmol m-3 in the WSG and WEA, respectively. Using a solar simulator, the extracted sample was irradiated and the ROH was determined and normalized based on the air-volume, which revealed values of 1.4 and 0.5 nmol h-1 m-3 for the WEA and WSG, respectively. Linear relationship between irradiation time and production of ?OH in both fractions suggested high capacity or similar efficiency of ?OH generation. The contribution of NO3-, NO2- and H2O2 to the formation of ?OH via photolysis were 4.5, 0.7 and 1.2%, respectively, for the WSG fraction, while in the WEA fraction, NO3-, NO2- and H2O2 contributed 8.9, 1.2 and 2.5%, respectively. The photo-Fenton reaction contributed 42% of the total ?OH formation in the WSG fraction, while unknown sources that might be humic-like substances (HULIS) accounted for the remaining 52%.

Nomi, S. N.; Sakugawa, H. H.; Kondo, H.

2011-12-01

275

Volatile Organic Compounds in Untreated Ambient Groundwater of  

E-print Network

Volatile Organic Compounds in Untreated Ambient Groundwater of the United States, 1985-1995 P A U L, ambient groundwater of the conterminous United States was conducted based on samples collected from 2948-chloropropane, which had a reporting level of 1.0 µg/L. Because ambient groundwater was targeted, areas of known

276

Assessment of fine and sub-micrometer aerosols at an urban environment of Argentina  

NASA Astrophysics Data System (ADS)

Bulk aerosol samples collected during 2010 and 2011 at one receptor site in Crdoba City, Argentina, have been quantitatively analyzed to determine aerosol elemental composition by using SR-XRF. A receptor model analysis has been applied to ambient PM2.5 measurements. Four sources have been identified being their contributions: traffic: (13 2) ?g m-3, SO2-/combustion processes, including biomass burning: (15 1) ?g m-3, mineral dust: (7 2) ?g m-3 and industry: (8 1) ?g m-3. Source identification was carried out by inspection of key species in source profiles, seasonality of source contributions, comparison with literature data and the knowledge of the city; for the biomass burning contribution the MODIS burned area daily product was used to confirm wildfire events along the year. In addition, from May to August 2011, aerosols were collected in two additional size fractions (PM0.25-0.5, PM0.5-1) to investigate the toxic metal contributions to the finer fractions. An important result of this work is that toxic metals make an important contribution to the finest (PM0.25-0.5) size fraction. The results of the present analysis can help to demonstrate to local and national authorities the urgent need to carry out emission inventories, to implement air quality monitoring systems and to set regulations for PM2.5.

Achad, Mariana; Lpez, Mara Laura; Ceppi, Sergio; Palancar, Gustavo G.; Tirao, Germn; Toselli, Beatriz M.

2014-08-01

277

Aerosol Science and Technology, 42:10331041, 2008 Copyright c American Association for Aerosol Research  

E-print Network

and here the data are compared. The level of agreement between the two techniques with ambient aerosol de results from a bias in the filter-based measurements due to (a) the redistribution of liquid-like organic particulate matter (PM) around the fiber fil- ters thereby modifying the filter surface and subsequent light

278

Coastal Antarctic aerosol and snowfall chemistry  

Microsoft Academic Search

Aerosol samples have been collected at three stations on the coast of Antarctica. At Dumont d'Urville Station, samples have been collected for 4 years, at Halley Station for 2 years, and at Neumayer Station for 12 years. Fresh snow samples have also been collected at the three sites. At Halley, daily surface snow samples were taken, as well as firn

Eric W. Wolff; Michel R. Legrand; Dietmar Wagenbach

1998-01-01

279

Stable Carbon Fractionation In Size Segregated Aerosol Particles Produced By Controlled Biomass Burning  

NASA Astrophysics Data System (ADS)

Biomass burning is the largest source of primary fine fraction carbonaceous particles and the second largest source of trace gases in the global atmosphere with a strong effect not only on the regional scale but also in areas distant from the source . Many studies have often assumed no significant carbon isotope fractionation occurring between black carbon and the original vegetation during combustion. However, other studies suggested that stable carbon isotope ratios of char or BC may not reliably reflect carbon isotopic signatures of the source vegetation. Overall, the apparently conflicting results throughout the literature regarding the observed fractionation suggest that combustion conditions may be responsible for the observed effects. The purpose of the present study was to gather more quantitative information on carbonaceous aerosols produced in controlled biomass burning, thereby having a potential impact on interpreting ambient atmospheric observations. Seven different biomass fuel types were burned under controlled conditions to determine the effect of the biomass type on the emitted particulate matter mass and stable carbon isotope composition of bulk and size segregated particles. Size segregated aerosol particles were collected using the total suspended particle (TSP) sampler and a micro-orifice uniform deposit impactor (MOUDI). The results demonstrated that particle emissions were dominated by the submicron particles in all biomass types. However, significant differences in emissions of submicron particles and their dominant sizes were found between different biomass fuels. The largest negative fractionation was obtained for the wood pellet fuel type while the largest positive isotopic fractionation was observed during the buckwheat shells combustion. The carbon isotope composition of MOUDI samples compared very well with isotope composition of TSP samples indicating consistency of the results. The measurements of the stable carbon isotope ratio in size segregated aerosol particles suggested that combustion processes could strongly affect isotopic fractionation in aerosol particles of different sizes thereby potentially affecting an interpretation of ambient atmospheric observations.

Masalaite, Agne; Garbaras, Andrius; Garbariene, Inga; Ceburnis, Darius; Martuzevicius, Dainius; Puida, Egidijus; Kvietkus, Kestutis; Remeikis, Vidmantas

2014-05-01

280

COMBINED RECEPTOR MODEL FOR AMBIENT AND PERSONAL EXPOSURE SAMPLES  

EPA Science Inventory

Results from the Combined Receptor Model for Ambient and Personal Exposure Samples analysis will be presented at the American Association for Aerosol Research (AAAR) 24th Annual Conference in Austin, Texas (Oct 17 - 21, 2005). Receptor modeling approaches and results from EPA R...

281

Ambient Intelligence: Science or Fad? 1.1. Ambient intelligence: still young at 20 years  

E-print Network

Ambient intelligence concerns the use of emerging technologies for computing, sensing, displaying intelligence [STA 03], leading to the creation of the Disappearing Computer program within the European Union collectives of artificial agents for ambient intelligence4 , the internet of things5 and Machine-to-Machine (M

282

Generation of a monodispersed aerosol  

NASA Technical Reports Server (NTRS)

The identity and laboratory test methods for the generation of a monodispersed aerosol are reported on, and are subjected to the following constraints and parameters; (1) size distribution; (2) specific gravity; (3) scattering properties; (4) costs; (5) production. The procedure called for the collection of information from the literature, commercial available products, and experts working in the field. The following topics were investigated: (1) aerosols; (2) air pollution -- analysis; (3) atomizers; (4) dispersion; (5) particles -- optics, size analysis; (6) smoke -- generators, density measurements; (7) sprays; (8) wind tunnels -- visualization.

Schenck, H.; Mikasa, M.; Devicariis, R.

1974-01-01

283

Aerosol Chemistry of Furfural and Sugars  

NASA Astrophysics Data System (ADS)

Furfural and sugars (as levoglucosan equivalent) are derived from biomass burning and contribute to aerosol composition. This study examined the potential of furfural and levoglucosan to be tracers of biomass burning. Furfural is likely to be oxidized quickly so comparison with levoglucosan may give a sense of the age of the aerosols in forest fire smoke. However, few furfural emissions are available for biomass combustion. Furfural and sugars were determined in coarse aerosols (>2.4?m aerodynamic diameter) and fine aerosols (<2.4?m aerodynamic diameter) collected in 24 hour periods during different seasons in the United Kingdom and PM10 collected from Thailand and Malaysia including haze episodes. Also total suspended particulate matter (TSP) samples were collected from Taiwan. Furfural and sugars dominated in fine fractions, especially in the UK autumn. Sugars were found at 5.96-18.37 nmol m-3 in fine mode and 1.36-5.75 nmol m-3 in coarse mode aerosols in the UK. Furfural was found at 0.18-0.91 nmol m-3 and 0.05-0.51 nmol m-3 respectively in the same aerosols. Sugars were a dominant contributor to aerosol derived from biomass burning. Sugars and furfural were about 10 and 20 times higher during haze episodes in Malaysia. Laboratory experimental simulation suggested furfural is more rapid destroyed by UV and sunlight than levoglucosan.

Srithawirat, T.; Brimblecombe, P.

2008-12-01

284

Development of a cavity enhanced aerosol albedometer  

NASA Astrophysics Data System (ADS)

We report on the development of a cavity enhanced aerosol single scattering albedometer incorporating incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach and an integrating sphere (IS) for simultaneous in situ measurements of aerosol scattering and extinction coefficients in the exact same sample volume. The cavity enhanced albedometer employed a blue light-emitting diode (LED) based IBBCEAS approach for the measurement of wavelength-resolved aerosol optical extinction over the spectral range of 445-480 nm. An integrating sphere nephelometer coupled to the IBBCEAS setup was used for the measurement of aerosol scattering. The scattering signal was measured with a single channel photomultiplier tube (PMT), providing an integrated value over a narrow bandwidth (FWHM ~ 9 nm) in the spectral region of 465-474 nm. A scattering coefficient at a wavelength of 470 nm was deduced as an averaged scattering value and used for data analysis and instrumental performance comparison. Performance evaluation of the albedometer was carried out using laboratory-generated particles and ambient aerosol. The scattering and extinction measurements of monodisperse polystyrene latex (PSL) spheres generated in laboratory proved excellent correlation between two channels of the albedometer. The retrieved refractive index (RI) from the measured scattering and extinction efficiencies agreed well with the values reported in previously published papers. Aerosol light scattering and extinction coefficients, single scattering albedo (SSA) and NO2 concentrations in an ambient sample were directly and simultaneously measured using the developed albedometer. The developed instrument was validated via an intercomparison of the measured aerosol scattering coefficient and NO2 trace concentration against a TSI 3563 integrating nephelometer and a chemiluminescence detector, respectively.

Zhao, W.; Xu, X.; Dong, M.; Chen, W.; Gu, X.; Hu, C.; Huang, Y.; Gao, X.; Huang, W.; Zhang, W.

2014-03-01

285

Identification of the mass spectral signature of organic aerosols from wood burning emissions.  

PubMed

Throughout the winter months, the village of Roveredo, Switzerland, frequently experiences strong temperature inversions that contribute to elevated levels of particulate matter. Wood is used as fuel for 75% of the domestic heating installations in Roveredo, which makes it a suitable location to study wood burning emissions in the atmosphere in winter. An Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) was used to characterize the composition of the submicrometer, non-refractory aerosol particles at this location during two field campaigns in March and December 2005. Wood burning was found to be a major source of aerosols at this location in winter. Organics dominated the composition of the aerosols from this source, contributing up to 85% of the total AMS measured mass during the afternoon and evening hours. Carbonaceous particle analysis showed that organic carbon composed up to 86% of the total carbon mass collected at evening times. Results from 14C isotope determination revealed that up to 94% of the organic mass came from non-fossil sources, which can be attributed mostlyto wood burning. The unique combination of off-line 14C isotope analysis and on-line aerosol mass spectrometry was used to identify periods during which organic mass was mainly from wood burning emissions and allowed for the identification of the AMS spectral signature of this source in the atmosphere. The identified ambient signature of wood burning was found to be very similar to the mass spectral signature obtained during the burning of chestnut wood samples in a small stove and also to the spectrum of levoglucosan. Particles from wood burning appeared to be composed of highly oxygenated organic compounds, and mass fragments 60, 73, and 137 have been suggested as marker fragments for wood burning aerosols. Mass fragment 44, which is used as a marker for oxygenated organic aerosols (OOA), contributed about 5% to the total organic signal from primary wood burning sources. The ratio of the organic mass emitted from wood burning to m/z 60 in Roveredo is 36. This ratio may be used to provide an estimate of the organic aerosol mass emitted from wood burning in other locations. PMID:17874785

Alfarra, M Rami; Prevot, Andre S H; Szidat, Snke; Sandradewi, Jisca; Weimer, Silke; Lanz, Valentin A; Schreiber, Daniel; Mohr, Martin; Baltensperger, Urs

2007-08-15

286

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

NASA Astrophysics Data System (ADS)

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 11 November in 2002. In this study, it is demonstrated that single-particle analysis using the low-Z particle EPMA provides detailed information on various types of chemical species in the samples. The most abundantly encountered particles, both in coarse and fine fractions, are soil-derived particles such as aluminosilicates and silicon dioxide, except for the sample collected on 11 November 2002, where reacted CaCO3 particles are the most abundantly encountered. All four samples are found to have experienced chemical modifications during long-range transport because the samples contain a significant number of particles composed of chemical species, such as nitrate and sulfate, which resulted from atmospheric reactions of CaCO3 and sea-salt particles. This finding implies that CaCO3 and sea-salt particles reacted with sulfur and nitrogen oxide species during long-range transport. The sample collected on 11 November 2002 experienced the most extensive chemical modification during its transport. For this sample, the overall relative abundances of reacted CaCO3 and reacted sea-salt particles are 29.9% and 23.2%, respectively. In addition to the observation of the reacted CaCO3 and sea-salt particles, reacted K-containing particles are also encountered in this sample. In this work, it is observed that chemical modification of sea-salt particles was more extensive than that of CaCO3 particles. By considering the relative abundances of nitrate- and sulfate-containing particles, nitrate formation from CaCO3 and sea-salt particles in the air is found to be more favorable than sulfate formation.

Hwang, Heejin; Ro, Chul-Un

2005-12-01

287

A Computational Study of Acid Catalyzed Aerosol Reactions of Atmospherically Relevant Epoxides  

EPA Science Inventory

Epoxides are important intermediates of atmospheric isoprene oxidation. Their subsequent reactions in the particle phase lead to the production of organic compounds detected in ambient aerosols. We apply density functional theory to determine the important kinetic factors that ...

288

Investigation of the optical and cloud forming properties of pollution, biomass burning, and mineral dust aerosols  

E-print Network

the optical and cloud forming properties of a range of ambient aerosol types measured in a number of different locations. The tool used for most of these analyses is a differential mobility analyzer / tandem differential mobility analyzer (DMA / TDMA) system...

Lee, Yong Seob

2006-08-16

289

The Evolution of the Physicochemical Properties of Aerosols in the Atmosphere  

E-print Network

A Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system was used to measure simultaneously the size distribution and hygroscopicity of the ambient aerosol population. The system was operated aboard the National...

Tomlinson, Jason

2011-02-22

290

Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and ?-dicarbonyls  

NASA Astrophysics Data System (ADS)

To better understand the photochemical processing of dicarboxylic acids and related polar compounds, we conducted batch UV irradiation experiments on two types of aerosol samples collected from India, which represent anthropogenic (AA) and biogenic aerosols (BA), for time periods of 0.5 to 120 h. The irradiated samples were analyzed for molecular compositions of diacids, oxoacids and ?-dicarbonyls. The results show that photochemical degradation of oxalic (C2) and malonic (C3) and other C8-C12 diacids overwhelmed their production in aqueous aerosols whereas succinic acid (C4) and C5-C7 diacids showed a significant increase (ca. 10 times) during the course of irradiation experiments. The photochemical formation of oxoacids and ?-dicarbonyls overwhelmed their degradation during the early stages of experiment, except for ?-oxooctanoic acid (?C8) that showed a similar pattern to that of C4. We also found a gradual decrease in the relative abundance of C2 to total diacids and an increase in the relative abundance of C4 during prolonged experiment. Based on the changes in concentrations and mass ratios of selected species with the irradiation time, we hypothesize that iron-catalyzed photolysis of C2 and C3 diacids dominates their concentrations in Fe-rich atmospheric waters, whereas photochemical formation of C4 diacid (via ?C8) is enhanced with photochemical processing of aqueous aerosols in the atmosphere. This study demonstrates that the ambient aerosols contain abundant precursors that produce diacids, oxoacids and ?-dicarbonyls, although some species such as oxalic acid decompose extensively during an early stage of photochemical processing.

Pavuluri, C. M.; Kawamura, K.; Mihalopoulos, N.; Swaminathan, T.

2015-01-01

291

The Aerosol Modeling Testbed: A Tool to Facilitate Improved Aerosol Process Modules  

NASA Astrophysics Data System (ADS)

Predictions of aerosol mass, composition, size distribution, hygroscopicity, and optical properties still contain large uncertainties. For example, the formation and transformation of secondary organic aerosols and the nature of many cloud-aerosol interactions are still poorly understood and consequently inadequately represented in models. When new aerosol treatments are developed, they are usually implemented into an existing aerosol model and evaluated using a limited number of measurements from a specific case study. One consequence of the current modeling paradigm is that the performance and computational efficiency of several treatments for a specific aerosol process cannot be adequately quantified because many other processes among aerosol models are different as well. For example, predictions of aerosol properties from several models have been compared, but different grid configurations, meteorology, and emission rates are often employed so that variations in predicted aerosol properties among the models were not due entirely to the treatment of aerosol processes. Thus, these studies do not quantify the range of uncertainty associated only with the predicted aerosol properties, nor does this type of uncertainty analysis provide much information on which aerosol process needs improving the most. Reducing the uncertainties associated with aerosols predictions requires that we know the advantages and disadvantages of specific aerosol treatments when the meteorology, chemistry, and other aerosol processes are identical. To address these issues, an Aerosol Modeling Testbed (AMT) has been developed that will simplify and greatly increase the efficiency of evaluating new aerosol treatments for regional and global models. The AMT consists of a modular and user-friendly version of the Weather Research and Forecasting model (WRF-Chem), a series testbed cases consisting of extensive in situ and remote sensing measurements of meteorological, trace gas, and aerosol properties, and a suite of tools to evaluate the performance of aerosol process modules. The first testbed case completed is based on the Megacities Initiative: Local and Global Research Observations (MILAGRO) field campaign conducted in the vicinity of Mexico City during March 2006. In addition to standard in situ measurements of aerosol properties, aerosol composition from several Aerodyne Aerosol Mass Spectrometers, profiles of aerosol backscatter and extinction from the NASA High Resolution Spectral Lidar (HRSL), and aerosol optical depth from satellite instrumentation are included in the MILAGRO testbed case. Two other testbed cases are also being developed. An example of how the AMT can be used to assess the strengths and weaknesses of two aerosol models in WRF-Chem, one using a simple modal approach to represent the aerosol size distribution and the other using a more comple sectional approach, will be presented using both in situ and remote sensing data collected during MILAGRO. How the AMT can be used by the scientific community to foster collaborations and coordinate aerosol modeling research will also be discussed.

Fast, J. D.; Gustafson, W. I.; Chapman, E. G.; Easter, R. C.; Rishel, J.

2009-12-01

292

Hydrogen chloride partitioning in a Titan III exhaust cloud diluted with ambient air  

NASA Technical Reports Server (NTRS)

Measurements and analysis are presented of the partitioning of HCl between hydrochloric acid aerosol and gaseous HCl in a Titan III exhaust cloud, as the cloud is diluted with humid ambient air. Partitioning was determined by measuring the gaseous HCl concentration with a recently developed airborne Gas Filter Correlation detector and simultaneously with a chemiluminescence detector which measures total HCl. Although equilibrium predictions for HCl aerosol formation indicated that no HCl aerosol should exist in the exhaust cloud for the meteorological conditions of this launch, the measurements indicated significant HCl aerosol formation. These measurements will provide verification for advanced modeling programs now under development.

Sebacher, D. I.; Wornom, D. E.; Bendura, R. J.

1979-01-01

293

ORIGINAL ARTICLE Ambient Air Pollution  

E-print Network

ORIGINAL ARTICLE Ambient Air Pollution and Cardiovascular Emergency Department Visits Kristi Busico ambient air pollutants and cardiovascular disease (CVD), the roles of the physicochemical components the relation between ambient air pollution and cardiovascular conditions using ambient air quality data

Mulholland, James A.

294

Dicarboxylic acids, ketocarboxylic acids, ?-dicarbonyls, fatty acids and benzoic acid in PM2.5 aerosol collected during CAREBeijing-2007: an effect of traffic restriction on air quality  

NASA Astrophysics Data System (ADS)

Thirty water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids, ?-dicarbonyls, fatty acids, and benzoic acid were determined as well as organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) in PM2.5 samples collected during the Campaign of Air Quality Research in Beijing 2007 (CAREBeijing-2007) in the urban and suburban areas of Beijing. The objective of this study is to identify the influence of traffic emissions and regional transport to the atmosphere in Beijing during summer. PM2.5 samples collected with or without traffic restriction in Beijing are selected to evaluate the effectiveness of local traffic restriction measure on air pollution reduction. The average concentrations of the total quantified bifunctional organic compounds (TQBOC), total fatty acids and benzoic acid during the entire sampling period were 1184 241 ng m-3, 597 159 ng m-3 and 1496 511ng m-3 in PKU, and 1050 303 ng m-3, 475 114 ng m-3 and 1278 372 ng m-3 in Yufa. Oxalic acid (C2) was found as the most abundant dicarboxylic acid at PKU and Yufa, followed by phthalic acid (Ph). A strong even carbon number predominance with the highest level at palmitic acid (C16:0), followed by stearic acid (C18:0) was found for fatty acids. According to the back trajectories modeling results, the air masses were found to originate mainly from northeast, passing over southeast or south of Beijing (heavily populated, urbanized and industrialized areas), during heavier pollution events, whereas they are mainly from north or northwest sector (mountain areas without serious anthropogenic pollution sources) during cleaner events. The data with wind only from the same sector (minimizing the difference from regional contribution) but with and without traffic restriction in Beijing were analyzed to evaluate the effectiveness of local traffic restriction measure on the reduction of local air pollution in Beijing. The results suggested that the "traffic restriction" measure can reduce the air pollutants, but the decrease of pollutants is generally smaller in Yufa compared to that in PKU. Moreover, an enhancement of elemental carbon (EC) value indicates elevated primary emissions in Yufa during restriction period than non-restriction period. This study demonstrates that even when primary exhaust was controlled by traffic restriction, the contribution of secondary organic species formed from photochemical processes was critical with long-range atmospheric transport of pollutants.

Ho, K. F.; Huang, R.-J.; Kawamura, K.; Tachibana, E.; Lee, S. C.; Ho, S. S. H.; Zhu, T.; Tian, L.

2014-06-01

295

Global Atmospheric Aerosol Modeling  

NASA Technical Reports Server (NTRS)

Global aerosol models are used to study the distribution and properties of atmospheric aerosol particles as well as their effects on clouds, atmospheric chemistry, radiation, and climate. The present article provides an overview of the basic concepts of global atmospheric aerosol modeling and shows some examples from a global aerosol simulation. Particular emphasis is placed on the simulation of aerosol particles and their effects within global climate models.

Hendricks, Johannes; Aquila, Valentina; Righi, Mattia

2012-01-01

296

Organic Aerosol Formation in the Humid, Photochemically-Active Southeastern US: SOAS Experiments and Simulations  

NASA Astrophysics Data System (ADS)

Aqueous multiphase chemistry in the atmosphere can lead to rapid transformation of organic compounds, forming highly oxidized low volatility organic aerosol and, in some cases, light absorbing (brown) carbon. Because liquid water is globally abundant, this chemistry could substantially impact climate, air quality, health, and the environment. Gas-phase precursors released from biogenic and anthropogenic sources are oxidized and fragmented forming water-soluble gases that can undergo reactions in the aqueous phase (in clouds, fogs, and wet aerosols) leading to the formation of secondary organic aerosol (SOAAQ). Recent studies have highlighted the role of certain precursors like glyoxal, methylglyoxal, glycolaldehyde, acetic acid, acetone, and epoxides in the formation of SOAAQ. The goal of this work is to identify other precursors that are atmospherically important. In this study, ambient mixtures of water-soluble gases were scrubbed from the atmosphere at Brent, Alabama during the Southern Oxidant and Aerosol Study (SOAS). Four mist chambers in parallel collected ambient gases in a DI water medium at 20-25 LPM with a 4 hr collection time. Total organic carbon (TOC) values in daily composited samples were 64-180 ?M. Aqueous OH radical oxidation experiments were conducted with these mixtures in a newly designed cuvette chamber to understand the formation of SOA through gas followed by aqueous chemistry. OH radicals (3.5E-2 ?M [OH] s-1) were formed in-situ in the chamber, continuously by H2O2 photolysis. Precursors and products of these aqueous OH experiments were characterized using ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. ESI-MS results from a June 12th, 2013 sample showed precursors to be primarily odd, positive mode ions, indicative of the presence of non-nitrogen containing alcohols, aldehydes, organic peroxides, or epoxides. Products were seen in the negative mode and included organic acid ions like pyruvate and oxalate. The results from this study will be used to better understand aqueous chemistry in clouds/fogs and to identify precursors for laboratory study of wet aerosol, fog, and cloud chemistry.

Sareen, N.; Lim, Y. B.; Carlton, A. G.; Turpin, B. J.

2013-12-01

297

Quantitative LC-MS for water-soluble heterocyclic amines in fine aerosols (PM2.5) at Duke Forest, USA  

NASA Astrophysics Data System (ADS)

A quantitative liquid chromatography-mass spectrometry (LC-MS) technique was developed to measure the concentrations of heterocyclic nitrogen compounds in ambient fine aerosols (PM2.5). Quadrupole time-of-flight (Q-TOF) MS technology was used to provide both accurate-mass and MS/MS data for confirmation of chemical formula and nitrogen compound structure. The fine aerosol was collected over the winter and summer seasons at an experimental monitoring station at Duke Forest in North Carolina U.S.A. 3-Hydroxypyridine and two ?-carbolines, harmane, and norharmane, were observed in both campaigns at concentrations lower in summer (sum = 332 pg m-3; N = 27) than winter (554 pg m-3; N = 31). Aminopyridines, dimethylpyrazoles, and hydroxymethyl-pyridines were observed in the winter aerosols with a total estimated average concentration of 779 pg m-3. These results demonstrate the possibility of enhanced speciation and provide a first glance at heterocyclic amines in the water-soluble organic nitrogen (ON) fraction of fine aerosols collected from a forest atmosphere.

Samy, Shar; Hays, Michael D.

2013-06-01

298

ASSESSMENT OF THE LIQUID WATER CONTENT OF SUMMERTIME AEROSOL IN THE SOUTHEAST UNITED STATES  

EPA Science Inventory

The concentration of aerosol liquid water mass represents an important parameter for understanding the physical properties of PM2.5 in the atmosphere. Increases in ambient relative humidity can increase aerosol liquid water and thus the composite particle mass and particle volu...

299

The dependence of ice microphysics on aerosol concentration in arctic mixed-phase stratus clouds during ISDAC and M-PACE  

SciTech Connect

Cloud and aerosol data acquired by the National Research Council of Canada (NRC) Convair-580 aircraft in, above, and below single-layer arctic stratocumulus cloud during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in April 2008 were used to test three aerosol indirect effects hypothesized to act in mixed-phase clouds: the riming indirect effect, the glaciation indirect effect, and the cold second indirect effect. The data showed a correlation of R= 0.75 between liquid drop number concentration, Nliq, inside cloud and ambient aerosol number concentration NPCASP below cloud. This, combined with increasing liquid water content LWC with height above cloud base and the nearly constant profile of Nliq, suggested that liquid drops were nucleated from aerosol at cloud base. No strong evidence of a riming indirect effect was observed, but a strong correlation of R = 0.69 between ice crystal number concentration Ni and NPCASP above cloud was noted. Increases in ice nuclei (IN) concentration with NPCASP above cloud combined with the subadiabatic LWC profiles suggest possible mixing of IN from cloud top consistent with the glaciation indirect effect. The higher Nice and lower effective radius rel for the more polluted ISDAC cases compared to data collected in cleaner single-layer stratocumulus conditions during the Mixed-Phase Arctic Cloud Experiment is consistent with the operation of the cold second indirect effect. However, more data in a wider variety of meteorological and surface conditions, with greater variations in aerosol forcing, are required to identify the dominant aerosol forcing mechanisms in mixed-phase arctic clouds.

Jackson, Robert C.; McFarquhar, Greg; Korolev, Alexei; Earle, Michael; Liu, Peter S.; Lawson, R. P.; Brooks, Sarah D.; Wolde, Mengistu; Laskin, Alexander; Freer, Matthew

2012-08-14

300

Estimation of gas-particle partitioning coefficients (Kp) of carcinogenic polycyclic aromatic hydrocarbons in carbonaceous aerosols collected at Chiang-Mai, Bangkok and Hat-Yai, Thailand.  

PubMed

To assess environmental contamination with carcinogens, carbonaceous compounds, water-soluble ionic species and trace gaseous species were identified and quantified every three hours for three days at three different atmospheric layers at the heart of Chiang-Mai, Bangkok and Hat-Yai from December 2006 to February 2007. A DRI Model 2001 Thermal/Optical Carbon Analyzer with the IMPROVE thermal/optical reflectance (TOR) protocol was used to quantify the organic carbon (OC) and elemental carbon (EC) contents in PM10. Diurnal and vertical variability was also carefully investigated. In general, OC and EC mass concentration showed the highest values at the monitoring period of 21.00-00.00 as consequences of human activities at night bazaar coupled with reduction of mixing layer, decreased wind speed and termination of photolysis at nighttime. Morning peaks of carbonaceous compounds were observed during the sampling period of 06:00-09:00, emphasizing the main contribution of traffic emission in the three cities. The estimation of incremental lifetime particulate matter exposure (ILPE) raises concern of high risk of carbonaceous accumulation over workers and residents living close to the observatory sites. The average values of incremental lifetime particulate matter exposure (ILPE) of total carbon at Baiyoke Suit Hotel and Baiyoke Sky Hotel are approximately ten times higher than those air samples collected at Prince of Songkla University Hat-Yai campus corpse incinerator and fish-can manufacturing factory but only slightly higher than those of rice straw burning in Songkla province. This indicates a high risk of developing lung cancer and other respiratory diseases across workers and residents living in high buildings located in Pratunam area. Using knowledge of carbonaceous fractions in PM10, one can estimate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). Dachs-Eisenreich model highlights the crucial role of adsorption in gas-particle partitioning of low molecular weight PAHs, whereas both absorption and adsorption tend to account for gas-particle partitioning of high molecular weight PAHs in urban residential zones of Thailand. Interestingly, the absorption mode alone plays a minor role in gas-particle partitioning of PAHs in Chiang-Mai, Bangkok and Hat-Yai. PMID:23725158

Pongpiachan, Siwatt; Ho, Kin Fai; Cao, Junji

2013-01-01

301

A Microfluidic Paper-Based Analytical Device (?PAD) for Aerosol Oxidative Activity  

PubMed Central

Human exposure to particulate matter (PM) air pollution has been linked with respiratory, cardiovascular, and neurodegenerative diseases, in addition to various cancers. Consistent among all of these associations is the hypothesis that PM induces inflammation and oxidative stress in the affected tissue. Consequently, a variety of assays have been developed to quantify the oxidative activity of PM as a means to characterize its ability to induced oxidative stress. The vast majority of these assays rely on high-volume, fixed-location sampling methods due to limitations in assay sensitivity and detection limit. As a result, our understanding of how personal exposure contributes to the intake of oxidative air pollution is limited. To further this understanding, we present a microfluidic paper-based analytical device (?PAD) for measuring PM oxidative activity on filters collected by personal sampling. The ?PAD is inexpensive to fabricate and provides fast and sensitive analysis of aerosol oxidative activity. The oxidative activity measurement is based on the dithiothreitol assay (DTT assay), uses colorimetric detection, and can be completed in the field within 30 min following sample collection. The ?PAD assay was validated against the traditional DTT assay using 13 extracted aerosol samples including urban aerosols, biomass burning PM, cigarette smoke and incense smoke. The results showed no significant differences in DTT consumption rate measured by the two methods. To demonstrate the utility of the approach, personal samples were collected to estimate human exposures to PM from indoor air, outdoor air on a clean day, and outdoor air on a wildfire-impacted day in Fort Collins, CO. Filter samples collected on the wildfire day gave the highest oxidative activity on a mass normalized basis, whereas typical ambient background air showed the lowest oxidative activity. PMID:23227907

Sameenoi, Yupaporn; Panymeesamer, Pantila; Supalakorn, Natcha; Koehler, Kirsten; Chailapakul, Orawon; Henry, Charles S.; Volckens, John

2013-01-01

302

Aerosols of Mongolian arid area  

NASA Astrophysics Data System (ADS)

Sampling was performed in July-August 2005-2010 at Station Sain Shand (4454'N, 11007'E) in the Gobi desert (1000 m a.s.l.), West Mongolia. Aerosol samples were collected with a high volume sampler PM 10 (Andersen Instruments Inc., USA) onto Whatman-41 filters. The substance was extracted from the filters by de-ionized water. The solution was screened through an acetate-cellulose filter with 0.2 micron pore size. Ions of ammonium, sodium, potassium, magnesium, and calcium, as well as sulphate ions, nitrate ions, hydrocarbonate, chloride ions were determined in the filtrate by means of an atomic adsorption spectrometer Carl Zeiss Jena (Germany), a high performance liquid chromatographer Milichrome A-02 (Russia), and an ionic chromatographer ICS-3000 (Dionex, USA). The PAH fraction was separated from aerosol samples using hexane extraction at room temperature under UV environment. The extract was concentrated to 0.1-0.2 ml and analysed by a mass-spectrometer "Agilent, GC 6890, MSD 5973 Network". Analysis of concentrations of aerosols components, their correlation ratios, and meteorological modeling show that the main factor affecting chemical composition of aerosols is a flow of contaminants transferred by air masses to the sampling area mainly from the south and south-east, as well as wind conditions of the area, dust storms in particular. Sulphate, nitrate, and ammonium are major ions in aerosol particles at Station Sain Shand. Dust-borne aerosol is known to be a sorbent for both mineral and organic admixtures. Polycyclic aromatic hydrocarbons (PAH) being among superecotoxicants play an important role among resistant organic substances. PAH concentrations were determined in the samples collected in 2010. All aerosol samples contained dominant PAHs with 5-6 benzene rings ( (benze(k)fluoranthen, benze(b)flouranthen, benze(a)pyren, benze(?)pyren, perylene, benze(g,h,i)perylene, and indene(1,2,3-c,d)pyrene). Their total quantity varied between 42 and 90%. Compounds with low molecular weight and 3 benzene rings in its composition (phenanthrene and anthracene) amounted to 9-38% of the total PAH. PAH percentage in aerosol samples is characteristic of the warm season. Elevated fraction of low molecular weight PAHs (29-38%) was found in aerosol samples collected on 12-14 August and 18-19 August. High molecular weight PAHs were found in aerosols sampled on 14 and 16 August. Benze(g,h,i)perylene, indene(1,2,3-c,d)pyrene, and di-benze(?,h)anthracene were found in aerosols on 10, 11, 14, 15, 17, 19, and 20 August, and their fraction of total PAH amounted to 14-30%. These compounds are indicative of automotive emissions. Benze(a)pyrene is the most hazardous cancerogene from the list of the prioritized PAHs. Cases of exceeding benze(a)pyrene maximum permissible concentrations (1 ng/m3) in the air at Station Sain Shand were not recorded.

Golobokova, L.; Marinayte, I.; Zhamsueva, G.

2012-04-01

303

Development and Characterization of a Thermodenuder for Aerosol Volatility Measurements  

SciTech Connect

This SBIR Phase I project addressed the critical need for improved characterization of carbonaceous aerosol species in the atmosphere. The proposed work focused on the development of a thermodenuder (TD) system capable of systematically measuring volatility profiles of primary and secondary organic aerosol species and providing insight into the effects of absorbing and nonabsorbing organic coatings on particle absorption properties. This work provided the fundamental framework for the generation of essential information needed for improved predictions of ambient aerosol loadings and radiative properties by atmospheric chemistry models. As part of this work, Aerodyne Research, Inc. (ARI) continued to develop and test, with the final objective of commercialization, an improved thermodenuder system that can be used in series with any aerosol instrument or suite of instruments (e.g., aerosol mass spectrometers-AMS, scanning mobility particle sizers-SMPS, photoacoustic absorption spectrometers-PAS, etc.) to obtain aerosol chemical, physical, and optical properties as a function of particle volatility. In particular, we provided the proof of concept for the direct coupling of our improved TD design with a full microphysical model to obtain volatility profiles for different organic aerosol components and to allow for meaningful comparisons between different TD-derived aerosol measurements. In a TD, particles are passed through a heated zone and a denuding (activated charcoal) zone to remove semi-volatile material. Changes in particle size, number concentration, optical absorption, and chemical composition are subsequently detected with aerosol instrumentation. The aerosol volatility profiles provided by the TD will strengthen organic aerosol emission inventories, provide further insight into secondary aerosol formation mechanisms, and provide an important measure of particle absorption (including brown carbon contributions and identification, and absorption enhancements due to coatings on soot particles). The successfully completed Phase I project included construction of a prototype design for the TD with detailed physical modeling, testing with laboratory and ambient aerosol particles, and the initiation of a detailed microphysical model of the aerosol particles passing through the TD to extract vapor pressure distributions. The objective of the microphysical model is to derive vapor pressure distributions (i.e. vapor pressure ranges, including single chemical compounds, mixtures of known compounds, and complex real-world aerosols, such as SOA, and soot particles with absorbing and nonabsorbing coatings) from TD measurements of changes in particle size, mass, and chemical composition for known TD temperatures and flow rates (i.e. residence times). The proposed Phase II project was designed to optimize several TD systems for different instrument applications and to combine the hardware and modeling into a robust package for commercial sales.

Dr. Timothy Onasch

2009-09-09

304

Thermodesorption of aerosol matter on multiple filters of different materials for a more detailed evaluation of sampling artifacts  

NASA Astrophysics Data System (ADS)

Multiple, essentially identical samples of PM2.5, PM10 and TSP aerosol matter were collected on filters of cellulose acetate-nitrate membrane (CA), quartz fiber (QF) and glass fiber (GF) material. The samples were analyzed in terms of the gravimetric mass and the mass of nine inorganic ions. These parameters were also measured after step-wise thermodesorption of aerosol matter by 1-h heating in ambient air up to 350 C. The observed thermograms of the analyzed ions were compared with results obtained using pure and mixed salts on filter. In summer the apparent mass concentration of aerosol matter collected on CA was always larger than on QF and GF filter. The excess mass on CA was found to be highly volatile, i.e. completely removable at 120 C, and composed of both ionic and non-ionic matter. The apparent nitrate concentration sampled on QF and GF was almost an order of magnitude lower than on CA. The very pronounced nitrate losses from the fiber filters are attributed to volatilization of ammonium nitrate. In contrast, nitrate losses from CA were small or even negligible for two reasons, pile-up of aerosol matter predominantly on (rather than in) the filter ("cake" formation) and, more importantly, re-adsorption of volatilized ammonia and nitric acid in the filter. Sampling on GF filters was found to suffer from severe problems due to chemical reactions between Na + of the glass and SO 42- of the aerosol matter. A novel type of artifact was observed in sampling campaigns during fall. Presumably as a results of a high water content, the collected aerosol matter became liquefied and a large fraction of the water soluble components was driven through the filter into the support pad underneath. The negative "wetting artifact" was much more pronounced for the thin CA than for the relatively thick QF filters. The total amount of aerosol matter in the CA/pad and QF/pad combinations was the same, indicating that this kind of artifact can be corrected for. Ammonium nitrate-to-sulfate concentration ratios were low in summer ( 0.5 for PM2.5) but high in fall (? 2). Furthermore, the ion fractions were low in summer ( 30%), but quite high in fall (? 60%), and even higher in winter.

Wittmaack, Klaus; Keck, Lothar

305

Filtering of air through snow as a mechanism for aerosol deposition to the Antarctic ice sheet  

NASA Astrophysics Data System (ADS)

Aerosol particles serve as cloud condensation nuclei worldwide, and they affect the Earth's radiation budget both directly and indirectly. These particles consist mostly of sulfate compounds. Ice core measurements can be used to infer past variations of atmospheric sulfate concentration, but to do so requires knowledge of the deposition mechanisms. Significant "dry" deposition may occur by filtering when air moves through the snow due to changes in pressure caused by wind blowing over a rough surface (wind pumping). The filtering efficiency of snow was measured at South Pole Station, using an optical particle counter and a condensation nucleus counter. The number size-distribution of ambient aerosol peaks at a dry particle diameter of 0.13 ?m, the volume size-distribution at 0.17 ?m. Less than 5% of the particles have diameters >0.3 ?m. Diffusion from interstitial air to snow grains appears to be the primary mechanism of dry deposition for particles <0.6 ?m in diameter, but another mechanism, probably impaction, becomes significant for larger particles. Aerosol deposition by filtering occurs with an e-folding time of 1-3 s depending on particle size, corresponding to an e-folding depth of 0.5-1 cm for an estimated air velocity of 0.4 cm s-1 within the surface snow. Even for long residence times, a small number of particles (<0.1%) are found in filtered air, suggesting a small degree of new particle formation or reentrainment. However, both the e-folding depth and the reentrainment rate are small enough that smoothing of the sulfate records in ice cores should be negligible. Three mathematical models for filters agree in describing filtering by snow as dominated by diffusion, but all underpredict the filter efficiency. Capture of aerosol particles is found to be 2-3 times as rapid as that assumed by Cunningham and Waddington [1993], supporting their conclusion of nearly total removal of particles from air entering the snow. Blowing snow might also be expected to collect aerosol particles; however, a calculation suggests that deposition to blowing snow on the Antarctic Plateau is insignificant. If wind pumping and diffusion contribute significantly to total deposition, the flux of air into the snow and the residence time of the air within the snow control the deposition rate. Both air flux and residence time are functions of wind speed and surface roughness, so that the aerosol flux to the snow depends on these factors as well as atmospheric concentration, complicating the interpretation of paleoclimate records for aerosol-bound substances.

Harder, Susan L.; Warren, Stephen G.; Charlson, Robert J.; Covert, David S.

1996-08-01

306

AMBIENT AIR MONITORING STRATEGY  

EPA Science Inventory

The Clean Air Act requires EPA to establish national ambient air quality standards and to regulate as necessary, hazardous air pollutants. EPA uses ambient air monitoring to determine current air quality conditions, and to assess progress toward meeting these standards and relat...

307

Measuring the charge and size distribution of charged aerosol particles inside PMSE and NLC  

NASA Astrophysics Data System (ADS)

During the MIDAS/MacWave 2002 rocket campaign charged aerosol probes launched aboard MIDAS payloads detected positively and negatively charged aerosol particles. Two aerosol probes were used on each MIDAS payload. One probe was a collection surface shielded by a magnetic field that prevented electron collection, allowing unambiguous identification of negative aerosol particles. The other probe was a collection surface shielded by both a magnetic field and an electric field that suppressed positive ion collection, and thus allowed unambiguous identification of positive aerosol particles. During the first salvo of the campaign, there was both a noctilucent cloud (NLC) and polar mesospheric summer echo (PMSE) present above the launch site. The probes measured a distribution of charged aerosol particles in-situ: both small and large negative particles centered at the NLC altitude, and a layer of small positive aerosols across the lower half of the PMSE.

Smiley, Byron; Rapp, Markus; Blix, Tom; Robertson, Scott; Hornyi, Mihaly; Latteck, Ralph

2003-08-01

308

Analysis of Fresh and Aged Aerosols Produced by Biomass Combustion  

NASA Astrophysics Data System (ADS)

Emissions from biomass combustion are known to influence human health, visibility, the global radiation budget, and cloud properties. Much research has been done looking at the primary emissions of wild and prescribed fires. As a result, primary smoke marker compounds, such as levoglucosan (a combustion product of cellulose), have been identified and used to determine the impact of fires on ambient air quality. However, little is known about the chemical processing occurring within smoke plumes and the resulting production of secondary organic aerosols (SOA). This likely leads to an underestimation of biomass burning impacts on particulate organic carbon (OC), often used in large-scale air quality model simulations. To better understand biomass smoke aging, hi-volume PM2.5 filter samples from two studies are compared here. Data from the Fire Lab at Missoula Experiments (FLAME) represent fresh smoke, sampled at the source of the fire. Aged smoke was collected during the Yosemite Aerosol Characterization Study (YACS), where the sampling site was days downwind from forest fires. Additional samples of aged smoke were collected at Rocky Mountain National Park and the Colorado State University Atmospheric Science Department, which were both affected by transported smoke from wildfires in southern California. Aqueous extracts of these samples have been analyzed using Liquid Chromatography coupled with a Time-of-Flight Mass Spectrometer (LC-TOF-MS) with electrospray ionization, as well as with a Linear Trap Quadrupole-Orbitrap Mass Spectrometr (LTQ-Orbitrap MS). Samples of fresh and aged smoke will be compared to help identify processes occurring during biomass smoke aging and transport. Preliminary results have shown the products of monoterpene oxidation, such as limonene, in all samples. Analysis has also shown an abundance of nitrogen-containing compounds in samples affected by biomass smoke, as well as an increase in oxidation with aged smoke samples.

Holden, A. S.; Desyaterik, Y.; Laskin, A.; Laskin, J.; Schichtel, B. A.; Malm, W. C.; Kreidenweis, S. M.; Collett, J. L.

2010-12-01

309

Aerosol mobility size spectrometer  

DOEpatents

A device for measuring aerosol size distribution within a sample containing aerosol particles. The device generally includes a spectrometer housing defining an interior chamber and a camera for recording aerosol size streams exiting the chamber. The housing includes an inlet for introducing a flow medium into the chamber in a flow direction, an aerosol injection port adjacent the inlet for introducing a charged aerosol sample into the chamber, a separation section for applying an electric field to the aerosol sample across the flow direction and an outlet opposite the inlet. In the separation section, the aerosol sample becomes entrained in the flow medium and the aerosol particles within the aerosol sample are separated by size into a plurality of aerosol flow streams under the influence of the electric field. The camera is disposed adjacent the housing outlet for optically detecting a relative position of at least one aerosol flow stream exiting the outlet and for optically detecting the number of aerosol particles within the at least one aerosol flow stream.

Wang, Jian (Port Jefferson, NY); Kulkarni, Pramod (Port Jefferson Station, NY)

2007-11-20

310

BIOCHEMICAL CHANGES IN HUMANS UPON EXPOSURE TO SULFURIC ACID AEROSOL AND EXERCISE  

EPA Science Inventory

A total of 18 human subjects were exposed to ambient air for four hours on the first day of exposure and to four hours of 100 micrograms/cu. m. (0.033 micromole) sulfuric acid aerosol exposed to four hours of ambient air on both exposure days. Six biochemical blood parameters wer...

311

Carbonaceous aerosol over a Pinus taeda forest in Central North Carolina, USA  

EPA Science Inventory

Organic aerosol is the least understood component of ambient fine particulate matter (PM2.5). Presented in this study are organic and elemental carbon (OC and EC) within ambient PM2.5 over a three-year period at a forested site in the North Carolina Piedmon. EC exhibited signifi...

312

X-ray fluorescence spectrometry for high throughput analysis of atmospheric aerosol samples: The benefits of synchrotron X-rays  

NASA Astrophysics Data System (ADS)

The determination of trace element mass concentrations in ambient air with a time resolution higher than one day represents an urgent need in atmospheric research. It involves the application of a specific technique both for the aerosol sampling and the subsequent analysis of the collected particles. Beside the intrinsic sensitivity of the analytical method, the sampling interval and thus the quantity of collected material that is available for subsequent analysis is a major factor driving the overall trace element detection power. This is demonstrated for synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) of aerosol samples collected with a rotating drum impactor (RDI) in hourly intervals and three particle size ranges. The total aerosol mass on the 1-h samples is in the range of 10 g. An experimental detection of the nanogram amounts of trace elements with the help of synchrotron X-rays was only achievable by the design of a fit-for-purpose sample holder system, which considered the boundary conditions both from particle sampling and analysis. A 6-m polypropylene substrate film has evolved as substrate of choice, due to its practical applicability during sampling and its suitable spectroscopic behavior. In contrast to monochromatic excitation conditions, the application of a 'white' beam led to a better spectral signal-to-background ratio. Despite the low sample mass, a counting time of less than 30 s per 1-h aerosol sample led to sufficient counting statistics. Therefore the RDI-SR-XRF method represents a high-throughput analysis procedure without the need for any sample preparation. The analysis of a multielemental mass standard film by SR-XRF, laboratory-based wavelength-dispersive XRF spectrometry and laboratory-based micro XRF spectrometry showed that the laboratory-based methods were no alternatives to the SR-XRF method with respect to sensitivity and efficiency of analysis.

Bukowiecki, Nicolas; Lienemann, Peter; Zwicky, Christoph N.; Furger, Markus; Richard, Agnes; Falkenberg, Gerald; Rickers, Karen; Grolimund, Daniel; Borca, Camelia; Hill, Matthias; Gehrig, Robert; Baltensperger, Urs

2008-09-01

313

Monitoring biological aerosols using UV fluorescence  

NASA Astrophysics Data System (ADS)

An apparatus has been designed and constructed to continuously monitor the number density, size, and fluorescent emission of ambient aerosol particles. The application of fluorescence to biological particles suspended in the atmosphere requires laser excitation in the UV spectral region. In this study, a Nd:YAG laser is quadrupled to provide a 266 nm wavelength to excite emission from single micrometer-sized particles in air. Fluorescent emission is used to continuously identify aerosol particles of biological origin. For calibration, biological samples of Bacillus subtilis spores and vegetative cells, Esherichia coli, Bacillus thuringiensis and Erwinia herbicola vegetative cells were prepared as suspensions in water and nebulized to produce aerosols. Detection of single aerosol particles, provides elastic scattering response as well as fluorescent emission in two spectral bands simultaneously. Our efforts have focuses on empirical characterization of the emission and scattering characteristics of various bacterial samples to determine the feasibility of optical discrimination between different cell types. Preliminary spectroscopic evidence suggest that different samples can be distinguished as separate bio-aerosol groups. In addition to controlled sample results, we will also discuss the most recent result on the effectiveness of detection outdoor releases and variations in environmental backgrounds.

Eversole, Jay D.; Roselle, Dominick; Seaver, Mark E.

1999-01-01

314

Trends in aerosol abundances and distributions  

NASA Technical Reports Server (NTRS)

The properties of aerosols that reside in the upper atmosphere are described. Special emphasis is given to the influence these aerosols have on ozone observation systems, mainly through radiative effects, and on ambient ozone concentrations, mainly through chemical effects. It has long been appreciated that stratospheric particles can interfere with the remote sensing of ozone distribution. The mechanism and magnitude of this interference are evaluated. Separate sections deal with the optical properties of upper atmospheric aerosols, long-term trends in stratospheric aerosols, perturbations of the stratospheric aerosol layer by volcanic eruptions, and estimates of the impacts that such particles have on remotely measured ozone concentrations. Another section is devoted to a discussion of the polar stratospheric clouds (PSC's). These unique clouds, recently discovered by satellite observation, are now thought to be intimately connected with the Antarctic ozone hole. Accordingly, interest in PSC's has grown considerably in recent years. This chapter describes what we know about the morphology, physical chemistry, and microphysics of PSC's.

Turco, R. P.; Mccormick, M. P.; Clancy, R. T.; Curran, R.; Deluisi, J.; Hamill, P.; Kent, G.; Rosen, J. M.; Toon, O. B.; Yue, G.

1989-01-01

315

Physicochemical Characterization of Capstone Depleted Uranium Aerosols I: Uranium Concentration in Aerosols as a Function of Time and Particle Size  

SciTech Connect

During the Capstone Depleted Uranium (DU) Aerosol Study, aerosols containing depleted uranium were produced inside unventilated armored vehicles (i.e., Abrams tanks and Bradley Fighting Vehicles) by perforation with large-caliber DU penetrators. These aerosols were collected and characterized, and the data were subsequently used to assess human health risks to personnel exposed to DU aerosols. The DU content of each aerosol sample was first quantified by radioanalytical methods, and selected samples, primarily those from the cyclone separator grit chambers, were analyzed radiochemically. Deposition occurred inside the vehicles as particles settled on interior surfaces. Settling rates of uranium from the aerosols were evaluated using filter cassette samples that collected aerosol as total mass over eight sequential time intervals. A moving filter was used to collect aerosol samples over time particularly within the first minute after the shot. The results demonstrate that the peak uranium concentration in the aerosol occurred in the first 10 s, and the concentration decreased in the Abrams tank shots to about 50% within 1 min and to less than 2% 30 min after perforation. In the Bradley vehicle, the initial (and maximum) uranium concentration was lower than those observed in the Abrams tank and decreased more slowly. Uranium mass concentrations in the aerosols as a function of particle size were evaluated using samples collected in the cyclone samplers, which collected aerosol continuously for 2 h post perforation. The percentages of uranium mass in the cyclone separator stages from the Abrams tank tests ranged from 38% to 72% and, in most cases, varied with particle size, typically with less uranium associated with the smaller particle sizes. Results with the Bradley vehicle ranged from 18% to 29% and were not specifically correlated with particle size.

Parkhurst, MaryAnn; Cheng, Yung-Sung; Kenoyer, Judson L.; Traub, Richard J.

2009-03-01

316

MODAL AEROSOL DYNAMICS MODELING  

EPA Science Inventory

The report described by this Project Summary presents the governing equations for representing aerosol dynamics, based on several different representations of the aerosol size distribution. Analytical and numerical solution techniques for these governing equations are also review...

317

AEROSOL CHARACTERISTICS AND VISIBILITY  

EPA Science Inventory

This report summarizes progress in measuring the optical properties of aerosols and in relating aerosol characteristics to visibility reduction made in the author's laboratory during the period 1965-1971. An instrument, the integrating nephelometer, which measures the scattering ...

318

AEROSOL AND GAS MEASUREMENT  

EPA Science Inventory

Measurements provide fundamental information for evaluating and managing the impact of aerosols on air quality. Specific measurements of aerosol concentration and their physical and chemical properties are required by different users to meet different user-community needs. Befo...

319

Source apportionment of ambient fine particle size distribution using positive matrix factorization in Erfurt, Germany.  

PubMed

Particle size distribution data collected between September 1997 and August 2001 in Erfurt, Germany were used to investigate the sources of ambient particulate matter by positive matrix factorization (PMF). A total of 29,313 hourly averaged particle size distribution measurements covering the size range of 0.01 to 3.0 microm were included in the analysis. The particle number concentrations (cm(-3)) for the 9 channels in the ultrafine range, and mass concentrations (ng m(-3)) for the 41 size bins in the accumulation mode and particle up to 3 microm in aerodynamic diameter were used in the PMF. The analysis was performed separately for each season. Additional analyses were performed including calculations of the correlations of factor contributions with gaseous pollutants (O(3), NO, NO(2), CO and SO(2)) and particle composition data (sulfate, organic carbon and elemental carbon), estimating the contributions of each factor to the total number and mass concentration, identifying the directional locations of the sources using the conditional probability function, and examining the diurnal patterns of factor scores. These results were used to assist in the interpretation of the factors. Five factors representing particles from airborne soil, ultrafine particles from local traffic, secondary aerosols from local fuel combustion, particles from remote traffic sources, and secondary aerosols from multiple sources were identified in all seasons. PMID:18433834

Yue, Wei; Stlzel, Matthias; Cyrys, Josef; Pitz, Mike; Heinrich, Joachim; Kreyling, Wolfgang G; Wichmann, H-Erich; Peters, Annette; Wang, Sheng; Hopke, Philip K

2008-07-15

320

Diurnal Evolution of Aerosol Optical Properties and Morphology at Pico Tres Padres: A Phenomenological Analysis  

NASA Astrophysics Data System (ADS)

Aerosol optical properties affect planetary radiative balance and therefore climate. The optical properties are related to chemical composition, size distribution, and morphology, which also have implications for human health and environmental degradation. During the MILAGRO field campaign, we measured ensemble aerosol absorption and angle-integrated scattering in Mexico City. These measurements were performed using the Los Alamos aerosol photoacoustic instrument with an integrated nephelometer (LAPA) operating at 781 nm. The LAPA was mounted on-board the Aerodyne Inc. mobile laboratory, which hosted a wide variety of gaseous and aerosol instruments. During the campaign, the Aerodyne mobile laboratory was moved to different sites, capturing the influence of spatial and temporal parameters including location, aging, elevation, and sources on ambient air pollution. The LAPA operated almost continuously between the 3rd and the 28th of March 2006. During the same period we collected ambient aerosols on more than 100 Nuclepore filters for scanning electron microscopy (SEM) analysis. Filter samples were collected during specific pollution events and different times of the day. Subsequently, SEM images of selected filters were taken to study particle morphology. The elemental composition of a few individual particles was also qualitatively assessed by energy dispersive X-ray spectroscopy. Between March 7th and 19th the laboratory was sampling air close to the top of the Pico Tres Padres, a ~3000 m high mountain on the north side of the Mexico City. Daily changes of aerosol loading and pollutant concentrations followed the expected diurnal variations of the boundary layer height. Here we report a preliminary analysis of aerosol absorption, scattering, and morphology at Pico Tres Padres for three specific days (9th, 11th and 12th of March 2006). The single scattering albedo (ratio of scattering to total extinction) during these three days showed a characteristic drop in the tens-of-minutes-to-hour time frame immediately following the growth of the boundary layer above the sampling site. Later in the day the single scattering albedo grew steadily to reach a maximum in the late afternoon. The SEM images show a wide variety of aerosol shapes including fractal-like chain aggregates (possibly soot), spherical particles (possibly tar balls), cylinders, and irregular non-fractal shapes. The increased afternoon single scattering albedo in the hottest part of the day qualitatively correlated with a relative increase in spherical particles that typically are not strongly light absorbing relative to fractal-like chain aggregates that are typically strongly light absorbing. These changes in optical properties and/or morphology can be explained by multiple mechanisms such as the collapse of fractal-like chain aggregates due to thermal effects and/or condensation of volatile compounds, coating by organic compounds, and photochemical secondary organic particle formation. Elemental analysis of a few individual particles yielded a relative large carbon abundance combined with smaller fractions of oxygen, silicon, metals, and other elements.

Mazzoleni, C.; Chakrabarty, R.; Dubey, M. K.; Moosmuller, H.; Chylek, P.; Onasch, T. B.; Herndon, S.; Zavala, M.; Kolb, C.

2007-05-01

321

Aerosol Characterization Data from the Asian Pacific Regional Aerosol Characterization Project (ACE-Asia)  

DOE Data Explorer

The Aerosol Characterization Experiments (ACE) were designed to increase understanding of how atmospheric aerosol particles affect the Earth's climate system. These experiments integrated in-situ measurements, satellite observations, and models to reduce the uncertainty in calculations of the climate forcing due to aerosol particles and improve the ability of models to predict the influences of aerosols on the Earth's radiation balance. ACE-Asia was the fourth in a series of experiments organized by the International Global Atmospheric Chemistry (IGAC) Program (A Core Project of the International Geosphere Biosphere Program). The Intensive Field Phase for ACE-Asia took place during the spring of 2001 (mid-March through early May) off the coast of China, Japan and Korea. ACE-Asia pursued three specific objectives: 1) Determine the physical, chemical, and radiative properties of the major aerosol types in the Eastern Asia and Northwest Pacific region and investigate the relationships among these properties. 2) Quantify the physical and chemical processes controlling the evolution of the major aerosol types and in particular their physical, chemical, and radiative properties. 3) Develop procedures to extrapolate aerosol properties and processes from local to regional and global scales, and assess the regional direct and indirect radiative forcing by aerosols in the Eastern Asia and Northwest Pacific region [Edited and shortened version of summary at http://data.eol.ucar.edu/codiac/projs?ACE-ASIA]. The Ace-Asia collection contains 174 datasets.

322

NUMERICAL CALCULATION OF INERTIAL ASPIRATION EFFICIENCY OF AEROSOLS INTO THIN-WALLED SAMPLING INLETS  

EPA Science Inventory

Unbiased sampling of airborne particulate from a flowing stream requires that the size distribution and concentration of aerosol collected be identical to that of the aerosol in the free stream. ampling errors occur during aspiration of the aerosol from the free stream to he face...

323

Evidence that the spectral dependence of light absorption by aerosols is affected by organic carbon  

Microsoft Academic Search

The wavelength dependence of light absorption by aerosols collected on filters is investigated throughout the near-ultraviolet to near-infrared spectral region. Measurements were made using an optical transmission method. Aerosols produced by biomass combustion, including wood and savanna burning, and by motor vehicles, including diesel trucks, are included in the analysis. These aerosol types were distinguished by different wavelength (?) dependences

Thomas W. Kirchstetter; T. Novakov; Peter V. Hobbs

2004-01-01

324

Diurnal variability of dust aerosol optical thickness and Angstrom exponent over dust source regions in China  

E-print Network

Diurnal variability of dust aerosol optical thickness and Angstro¨m exponent over dust source of Sunphotometer Aerosol Optical Thickness (AOT) data collected near the Taklamakan and Gobi dust source regions (Dunhuang, 40.09°N, 94.41°E) in China; we examine the diurnal and seasonal change of dust aerosol properties

Wang, Jun

325

A semi-automated system for quantifying the oxidative potential of ambient particles in aqueous extracts using the dithiothreitol (DTT) assay: results from the Southeastern Center for Air Pollution and Epidemiology (SCAPE)  

NASA Astrophysics Data System (ADS)

A variety of methods are used to measure the capability of particulate matter (PM) to catalytically generate reactive oxygen species (ROS) in vivo, also defined as the aerosol oxidative potential. A widely used measure of aerosol oxidative potential is the dithiothreitol (DTT) assay, which monitors the depletion of DTT (a surrogate for cellular antioxidants) as catalyzed by the redox-active species in PM. However, a major constraint in the routine use of the DTT assay for integrating it with the large-scale health studies is its labor-intensive and time-consuming protocol. To specifically address this concern, we have developed a semi-automated system for quantifying the oxidative potential of aerosol liquid extracts using the DTT assay. The system, capable of unattended analysis at one sample per hour, has a high analytical precision (Coefficient of Variation of 12% for standards, 4% for ambient samples), and reasonably low limit of detection (0.31 nmol min-1). Comparison of the automated approach with the manual method conducted on ambient samples yielded good agreement (slope = 1.08 0.12, r2 = 0.92, N = 9). The system was utilized for the Southeastern Center for Air Pollution and Epidemiology (SCAPE) to generate an extensive data set on DTT activity of ambient particles collected from contrasting environments (urban, road-side, and rural) in the southeastern US. We find that water-soluble PM2.5 DTT activity on a per air volume basis was spatially uniform and often well correlated with PM2.5 mass (r = 0.49 to 0.88), suggesting regional sources contributing to the PM oxidative potential in southeast US. However, the greater heterogeneity in the intrinsic DTT activity (per PM mass basis) across seasons indicates variability in the DTT activity associated with aerosols from sources that vary with season. Although developed for the DTT assay, the instrument can also be used to determine oxidative potential with other acellular assays.

Fang, T.; Verma, V.; Guo, H.; King, L. E.; Edgerton, E. S.; Weber, R. J.

2014-07-01

326

COMPOSITION OF SIZE-FRACTIONATED AEROSOL IN CHARLESTON, WEST VIRGINIA  

EPA Science Inventory

Atmospheric aerosols were collected during a 21 day period in late summer of 1976 in Charleston, West Virginia, using five dichotomous virtual impactor samplers simultaneously. The resulting coarse and fine aerosol were analyzed with a variety of physical and chemical methods: gr...

327

Linking biogenic hydrocarbons to biogenic aerosol in the Borneo rainforest  

NASA Astrophysics Data System (ADS)

Emissions of biogenic volatile organic compounds are though to contribute significantly to secondary organic aerosol formation in the tropics, but understanding these transformation processes has proved difficult, due to the complexity of the chemistry involved and very low concentrations. Aerosols from above a Southeast Asian tropical rainforest in Borneo were characterised using liquid chromatography-ion trap mass spectrometry, high-resolution aerosol mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) techniques. Oxygenated compounds were identified in ambient organic aerosol that could be directly traced back to isoprene, monoterpenes and sesquiterpene emissions, by combining field data on chemical structures with mass spectral data generated from synthetically produced products created in a simulation chamber. Eighteen oxygenated species of biogenic origin were identified in the rainforest aerosol from the precursors isoprene, ?-pinene, limonene, ?-terpinene and ?-caryophyllene. The observations provide the unambiguous field detection of monoterpene and sesquiterpene oxidation products in SOA above a pristine tropical rainforest. The presence of 2-methyl tetrol organosulfates and an associated sulfated dimer provides direct evidence that isoprene in the presence of sulfate aerosol can make a contribution to biogenic organic aerosol above tropical forests. High-resolution mass spectrometry indicates that sulfur can also be incorporated into oxidation products arising from monoterpene precursors in tropical aerosol.

Hamilton, J. F.; Alfarra, M. R.; Robinson, N.; Ward, M. W.; Lewis, A. C.; McFiggans, G. B.; Coe, H.; Allan, J. D.

2013-11-01

328

Linking biogenic hydrocarbons to biogenic aerosol in the Borneo rainforest  

NASA Astrophysics Data System (ADS)

Emissions of biogenic volatile organic compounds are though to contribute significantly to secondary organic aerosol formation in the tropics, but understanding the process of these transformations has proved difficult, due to the complexity of the chemistry involved and very low concentrations. Aerosols from above a South East Asian tropical rainforest in Borneo were characterised using liquid chromatography-ion trap mass spectrometry, high resolution aerosol mass spectrometry and fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) techniques. Oxygenated compounds were identified in ambient organic aerosol that could be directly traced back to isoprene, monoterpenes and sesquiterpene emissions, by combining field data on chemical structures with mass spectral data generated from synthetically produced products created in a simulation chamber. Eighteen oxygenated species of biogenic origin were identified in the rainforest aerosol from the precursors isoprene, ?-pinene, limonene, ?-terpinene and ?-caryophyllene. The observations provide the unambiguous field detection of monoterpene and sesquiterpene oxidation products in SOA above a pristine tropical rainforest. The presence of 2-methyltetrol organosulfates and an associated sulfated dimer provides direct evidence that isoprene in the presence of sulfate aerosol can make a contribution to biogenic organic aerosol above tropical forests. High-resolution mass spectrometry indicates that sulfur can also be incorporated into oxidation products arising from monoterpene precursors in tropical aerosol.

Hamilton, J. F.; Alfarra, M. R.; Robinson, N.; Ward, M. W.; Lewis, A. C.; McFiggans, G. B.; Coe, H.; Allan, J. D.

2013-07-01

329

Organic and Inorganic Aerosol Below-Cloud Scavenging by  

E-print Network

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

Russell, Lynn

330

STUDY OF MICROBIAL AEROSOLS EMITTED FROM A WATER RECLAMATION PLANT  

EPA Science Inventory

The purpose of this investigation was to determine the occurrence of selected microorganisms in the air in the vicinity of the O'Hare Water Reclamation Plant (OWRP), Des Plaines, Illinois. The contribution of the OWRP to ambient microbial aerosols was determined by comparing base...

331

Aerosol and Transport Climatology at the Grand Canyon  

NASA Astrophysics Data System (ADS)

This study was carried out to establish a visibility and air quality climatology for the Grand Canyon to help evaluate the extent and conditions under which the degradation of visibility occurs in the region, and to investigate long-term relationships between airmass transport and observations at the sampling sites. The data set analyzed comes from a monitoring program called SCENES, which collected air samples during five years (1984-1989) at several sites around the Grand Canyon. The sampling and analysis of the aerosol were performed for two size fractions and various sampling schedules and analysis protocols were followed. The data set was organized according to these protocols, and then sorted according to parameters, such as the levels of haziness, humidity and a tracer for urban emissions. The aerosol composition was studied as a function of season, location, time of the day and the parameters above. A method was then devised to investigate the potential of routine ATAD back trajectory analyses to locate sources of contaminant in air at the Grand Canyon. The distribution of back trajectory segment endpoints on a latitude-longitude grid was examined as a function of the contaminant's concentration. Grid cells which were preferentially associated with high concentrations of the contaminant were identified as candidate emissions sources. Screening of chance associations due to statistical fluctuations was performed, and results were evaluated for real and hypothetical tracers with known distributions. The method was then applied to the chemical, optical and meteorological measurements made during SCENES to investigate the preferential association of these variables with regions around the Grand Canyon. Chemical mass balance calculations performed under different conditions of the atmosphere indicate that aerosols in the region exhibit substantial seasonal variation in composition and concentration, but little systematic diurnal variation. The ambient humidity affects the composition of the aerosol, but not its total concentration. Although fine mass correlated strongly with light scattering, as expected, little association between chemical composition and light scattering was seen. Results of the back trajectory analysis showed that the method was able to resolve the direction of potential sources, but with poor radial precision. In general, the lowest levels of fine-mass and sulfur concentrations, as well as of light scattering by particles, are associated with northerly flow. Airmasses from the north generally have higher speeds than the ones from the south, and are transported over regions with fewer emission sources; they are less likely to accumulate pollutants. The airmasses with the highest fine-mass concentrations and light scattering values usually come from the south, and they are consistently associated with both southern California and central and southern Arizona.

Vasconcelos, Luis Alfredo De Paula

1995-01-01

332

Characterizations of atmospheric fungal aerosol in Beijing, China  

NASA Astrophysics Data System (ADS)

Fungal aerosols constitute the most abundant fraction of biological aerosols in the atmosphere, influencing human health, the biosphere, atmospheric chemistry and climate. However, the total abundance of fungal spores in the atmosphere is still poorly understood and quantified. PM10 and PM2.5 samples were collected by high volume samplers simultaneously at a rural site (MY) and an urban site (THU) in Beijing, China. Various carbohydrates were quantified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), including the sugar alcohols mannitol and arabitol, proposed as molecular tracers for fungal aerosol. The annual average concentrations of arabitol in PM2.5 and PM10 at the THU site were 7.49.4 ng/m3 and 10.39.5 ng/m3, and the respective mannitol concentrations were 21.020.4 ng/m3 and 31.926.9 ng/m3. Compared to PM10, the monthly average concentrations of arabitol and mannitol in PM2.5 did not vary significantly and were present at nearly consistent levels in the different seasons. Moreover, during summer and autumn higher arabitol and mannitol levels than during spring and winter were observed in coarse particles, probably due to different dominant sources of fungal spores in different seasons. In the dry period (i.e., winter and spring) in Beijing, probably only the suspension from exposed surfaces, (e.g., soil resuspension, transported dust, etc.) can be regarded as the main sources for fungal aerosols. On the other hand, in summer and autumn, fungal spores in the atmosphere can be derived from more complex sources, including plants, vegetation decomposition and agricultural activity, such as ploughing; these fungal spore sources may contribute more to coarse PM. Mannitol and arabitol correlated well with each other, both in PM10 (R2 = 0.71) and PM2.5 (R2 = 0.81). Although fungal spore levels at rural sites were consistently higher than those at urban sites in other studies, the findings in our study were reversed, indicating a high abundance of fungal spores in the urban area of Beijing, China. Meteorological conditions were shown to have complex effects on the ambient concentrations of fungal spores: the concentrations of arabitol exhibited positive correlation with temperature below 30.0 C, negative correlation with wind speed higher than 0.6 m/s, no relationship with solar radiation and the highest arabitol levels were mainly associated with RH in the range of 51-70%.

Liang, Linlin; Engling, Guenter; He, Kebin; Du, Zhenyu

2013-04-01

333

MODAL AEROSOL DYNAMICS MODEL  

EPA Science Inventory

The Modal Aerosol Dynamics (MAD) model is a computationally efficient model for solving the General Dynamics Equation of Aerosols (GDE) (Friedlander, 1977). The simplifying assumption in the model is that aerosol size distributions can be approximated by overlapping modes, each r...

334

Solid aerosol generator  

DOEpatents

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration is disclosed. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

Prescott, D.S.; Schober, R.K.; Beller, J.

1992-03-17

335

Improved solid aerosol generator  

DOEpatents

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates. 2 figs.

Prescott, D.S.; Schober, R.K.; Beller, J.

1988-07-19

336

Solid aerosol generator  

DOEpatents

An improved solid aerosol generator used to produce a gas borne stream of dry, solid particles of predetermined size and concentration. The improved solid aerosol generator nebulizes a feed solution of known concentration with a flow of preheated gas and dries the resultant wet heated aerosol in a grounded, conical heating chamber, achieving high recovery and flow rates.

Prescott, Donald S. (Shelley, ID); Schober, Robert K. (Midwest City, OK); Beller, John (Idaho Falls, ID)

1992-01-01

337

METHODOLOGY FOR MEASUREMENT OF POLYCHLORINATED BIPHENYLS IN AMBIENT AIR AND STATIONARY SOURCES - A REVIEW  

EPA Science Inventory

The state of development of methodology for measurement of polychlorinated biphenyls (PCBs) in ambient air and stationary sources was reviewed. The most promising method for ambient air measurements involves collection of PCBs on polyurethane foam, extraction with an organic solv...

338

CCN activity of size-selected aerosol at a Pacific coastal location  

NASA Astrophysics Data System (ADS)

As one aspect of the NETwork on Climate and Aerosols: addressing key uncertainties in Remote Canadian Environments (NETCARE), measurements of the cloud condensation nucleation properties of 50 and 100 nm aerosol particles were conducted at Ucluelet on the west coast of Vancouver Island in August 2013. The overall hygroscopicity parameter of the aerosol (?ambient) exhibited a wide variation, ranging from 0.14 0.05 to 1.08 0.40 (where the uncertainty represents the systematic error). The highest ? values arose when the organic-to-sulfate ratio of the aerosol was lowest and when winds arrived from the west after transport through the marine boundary layer. The average ?ambient during this time was 0.57 0.16, where the uncertainty represents the standard deviation. At most other times, the air was predominantly influenced by both marine and continental emissions, which had lower average PM1 ?ambient values (max value, 0.41 0.08). The two-day average aerosol ionic composition also showed variation, but was consistently acidic and dominated by ammonium (18-56% by mole) and sulfate (19-41% by mole), with only minor levels of sodium or chloride. Average ?org (hygroscopicity parameter for the aerosol's organic component) values were estimated using PM1 aerosol composition data and by assuming that the ratio of aerosol organic to sulfate mass is related directly to the composition of the size-selected particles.

Yakobi-Hancock, J. D.; Ladino, L. A.; Bertram, A. K.; Huffman, J. A.; Jones, K.; Leaitch, W. R.; Mason, R. H.; Schiller, C. L.; Toom-Sauntry, D.; Wong, J. P. S.; Abbatt, J. P. D.

2014-11-01

339

Effects of El Chichon volcanic effluents on stratospheric aerosol dynamics  

NASA Technical Reports Server (NTRS)

The effects of El Chichon's April 1982 eruption on stratospheric aerosol dynamics are presently discussed in terms of log-normal size distributions over 15-20 km sample altitudes between 30 and 45 deg N over the contiguous U.S. After collection, samples were studied by SEM, and log-normal size distributions were fitted to the data-points obtained. It is found that stratospheric aerosol behavior is explainable by the laws of aerosol mechanics more easily than has been the case for tropospheric aerosol, for which the source-sink relationship is much more complex.

Pueschel, R. F.; Snetsinger, K. G.; Russell, P. B.; Oberbeck, V. R.; Livingston, J. M.

1988-01-01

340

Assessment of the mixing state and cloud nucleating efficiency of Asian aerosols using aircraft-based measurements of hygroscopicity  

E-print Network

particles that act as cloud condensation nuclei. This study employs Tandem Differential Mobility Analyzer (TDMA) data collected in the vicinity of Japan during the Asian Aerosol Characterization Experiment (ACE-Asia) to investigate the influence of aerosol...

Thomas, Timothy William

2006-08-16

341

SEM/EDS of Submicron and Coarse PM Using Modified Passive Aerosol Sampler Substrates  

NASA Astrophysics Data System (ADS)

Deployment of multiple UNC Passive Aerosol Samplers is an inexpensive and unobtrusive technique for assessing airborne particulate matter (PM) exposure and spatial variability. Computer-controlled SEM/EDS (Scanning Electron Microscopy / Energy-Dispersive X-ray Spectroscopy) is used to measure the deposited particle mass and chemistry. A deposition velocity model is used to obtain ambient PM and elemental size distributions. Previous results have correlated well with active sampler results in environments dominated by coarse mineral dusts. To accurately measure submicron and carbonaceous aerosols, an improved collection substrate is needed. Previous studies used a double-sided carbon adhesive tab, which was ideal for coarse PM but under-detected submicron PM. One promising alternative is polycarbonate (PC) filter substrates. Another is transmission electron microscope (TEM) grids with formvar films mounted over holes drilled in the samplers. Preliminary tests of PC filters and TEM grid substrates, including tests in areas with smoke aerosols, exhibited substantial submicron aerosol and differing elemental size distributions. Detailed qualitative and quantitative evidence shows that the PC filters retained coarse PM well and yielded improved submicron PM imaging. TEM grids yield the best imaging and chemistry of submicron carbonaceous PM, but potentially the poorest retention of coarse PM. PM and elemental size distributions are presented for collocated passive samplers using the three substrate types, in both indoor and outdoor environments. Several methods are proposed to further optimize passive sampling of both submicron and coarse PM. Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Wagner, J.; Wang, Z.; Willis, B.; Casuccio, G.

2008-12-01

342

Aerosol-Cloud Interactions during Tropical Deep Convection: Evidence for the Importance of Free Tropospheric Aerosols  

NASA Technical Reports Server (NTRS)

NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and evolution of tropical cirrus cloud systems in southern Florida. Multiple aircraft extensively sampled cumulonimbus dynamical and microphysical properties, as well as characterizing ambient aerosol populations both inside and outside the full depth of the convective column. On July 18, unique measurements were taken when a powerful updraft was traversed directly by aircraft, providing a window into the primary source region of cumulonimbus anvil crystals. Observations of the updraft, entered at approximately l0 km altitude and -34 C, indicated more than 200 cloud particles per mL at vertical velocities exceeding 20 m/s and the presence of significant condensation nuclei and liquid water within the core. In this work, aerosol and cloud phase observations are integrated by simulating the updraft conditions using a large-eddy resolving model with 3 explicit multiphase microphysics, including treatment of size-resolved aerosol fields, aerosol activation and freezing, and evaporation of cloud particles back to the aerosol phase. Simulations were initialized with observed thermodynamic and aerosol size distributions profiles and convection was driven by surface fluxes assimilated from the ARPS forecast model. Model results are consistent with the conclusions that most crystals are homogeneously frozen droplets and that entrained free tropospheric aerosols may contribute a significant fraction of the crystals. Thus most anvil crystals appear to be formed aloft in updraft cores, well above cloud base. These conclusions are supported by observations of hydrometeor size distribution made while traversing the dore, as well as aerosol and cloud particle size distributions generally observed by aircraft below 4km and crystal properties generally observed by aircraft above 12km.

Ackerman, A.; Jensen, E.; Stevens, D.; Wang, D.; Heymsfield, A.; Miloshevich, L.; Twohy, C.; Poellot, M.; VanReken, T.; Fridland, Ann

2003-01-01

343

Photochemical and other sources of organic compounds in the Canadian high arctic aerosol pollution during winter-spring.  

PubMed

Total suspended particles collected at Alert in the Canadian high Arctic (February-June) were analyzed for solvent extractable organic compounds using gas chromatography-mass spectrometry to better understand the sources and source apportionment of aerosol pollution that can affect the Arctic climate. More than 100 organic species were detected in the aerosols and were grouped into different compound classes based on the functional groups. Polyacids were found to be the most abundant compound class, followed by phthalates, aromatic acids, fatty acids, fatty alcohols, sugars/sugar alcohols, and n-alkanes, while polycyclic aromatic hydrocarbons, sterols, and lignin and resin acids were minor. Concentrations of total quantified organics seemed slightly higher in darkwinter aerosols (13.2-16.6 ng m(-3), average 14.5 ng m(-3)) than those after polar sunrise (6.70-17.7 ng m(-3), average 11.8 ng m(-3)). During dark winter, fossil fuel combustion products (30-51%), secondary oxidation products, as well as higher plant emissions were found as major contributors to the Arctic aerosols. However, after polar sunrise on 5 March, secondary oxidation products (5-53%) and plasticizer-derived phthalates became the dominant compound classes, followed by fossil fuel combustion and microbial/marine sources. Biomass burning emissions were found to contribute only 0.4-6% of the total identified organics, although they maximized in dark winter. This study demonstrates that long-range atmospheric transport, changes in the solar irradiance, and ambient temperature can significantly control the chemical composition of organic aerosols in the Arctic region. PMID:19238953

Fu, Pingqing; Kawamura, Kimitaka; Barrie, Leonard A

2009-01-15

344

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

345

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

346

COMPARISON OF AMBIENT AIR SAMPLING TECHNIQUES FOR VOLATILE ORGANIC COMPOUNDS  

EPA Science Inventory

A series of fourteen experimental sampling runs were carried out at a field site to collect data from several ambient air monitoring methods for volatile organic compounds (VOCs). Ambient air was drawn through a sampling manifold and was continuously spiked with volatile organic ...

347

A portable and inexpensive method for quantifying ambient intermediate volatility organic compounds  

NASA Astrophysics Data System (ADS)

Volatile organic compounds (VOCs) and intermediate volatility VOCs (IVOCs) are gas-phase organic compounds which may participate in chemical reactions affecting air quality and climate. The development of an inexpensive, field-portable quantification method for higher molecular weight VOCs and IVOCs utilizing commercially available components could be used as a tool to survey aerosol precursors or identify and monitor air quality in various communities. We characterized the performance characteristics for the HayeSep-Q adsorbent with a representative selection of anthropogenic and biogenic VOC standards and optimized experimental conditions and procedures for field collections followed by laboratory analysis. All VOCs were analyzed using gas chromatography coupled with mass spectrometry. Precision (average 22%) and accuracy were reasonable and the limit of detection ranged from 10 to 80 pmol/mol (ppt) for the studied compounds. The method was employed at the Los Angeles site during the CalNex campaign in summer 2010 and ambient mixing ratios agreed well (slope 0.69-1.06, R2 0.67-0.71) with measurements made using an in-situ GC-MS - a distinctly different sampling and quantification method. This new technique can be applied to quantify ambient biogenic and anthropogenic C8-C15 VOCs and IVOCs.

Bouvier-Brown, Nicole C.; Carrasco, Erica; Karz, James; Chang, Kylee; Nguyen, Theodore; Ruiz, Daniel; Okonta, Vivian; Gilman, Jessica B.; Kuster, William C.; de Gouw, Joost A.

2014-09-01

348

Indirect and Semi-Direct Aerosol Campaign (ISDAC): The Impact of Arctic Aerosols on Clouds  

NASA Astrophysics Data System (ADS)

A comprehensive dataset on arctic boundary layer cloud and aerosol microphysical and radiative properties in the vicinity of Barrow, Alaska was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) sponsored by the Department of Energy Atmospheric Radiation Measurement (ARM) and Atmospheric Science Programs (ASP). The primary aim of ISDAC was to examine the influence of aerosols on clouds influenced by ice to extend studies of aerosol indirect effects that have mainly concentrated on liquid clouds. The experiment utilized the permanent observational facilities of ARM at the North Slope of Alaska (NSA) site in Barrow which include a cloud radar, a polarized micropulse lidar and an advanced emitted radiance interferometer as well as instruments specially deployed for ISDAC including those measuring aerosol, ice fog, precipitation and shortwave spectroradiometer characteristics. The National Research Council of Canada Convair-580 flew a total of 27 sorties during ISDAC, collecting data using an unprecedented 42 cloud and aerosol instruments for more than 100 hours on 12 different days. Data obtained above, below and within single-layer stratus during two golden cases on 8 April and 26 April 2008 are allowing for a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds in different surface conditions, with data acquired on a heavily polluted day on 19 April 2008 enhancing this understanding. Data acquired in cirrus on transit flights between Fairbanks and Alaska are being used to better understand the performance of cloud probes in ice. Ultimately these data will be used to improve the representation of cloud and aerosol process in models covering a variety of spatial and temporal scales, and to determine the extent to which long-term surface-based measurements at the NSA site can provide retrievals of aerosols, clouds, precipitation and radiative heating in the Arctic.

McFarquhar, Greg

2010-05-01

349

Meteorological and Aerosol Sensing with small Unmanned Aerial Systems  

NASA Astrophysics Data System (ADS)

Unmanned Aerial Systems (UAS) facilitate the monitoring of several meteorological and aerosol parameters with high resolution in space and time. They are small, easy to operate, cost efficient and allow for flexible application during field campaigns. We present two experimental payloads for measurement of relative humidity, temperature, aerosol size distribution and the collection of aerosol samples on board the small UAS SIRIUS II. The payload modules are light weight (<1kg) and can be easily switched between two flights. All sensors can be controlled from the ground and the measured data is recorded by the autopilot together with the position data. The first module contains a sensor package for measurement of relative humidity and temperature and the Compact Lightweight Aerosol Spectrometer Prope (CLASP) for acquisition of aerosol size distributions. CLASP measures aerosol particles with diameters from 0.12?m to 9.25?m in up to 32 channels at a frequency of 10 Hz. The second module also contains a humidity and temperature sensor package and the aerosol sample collection device. The aerosol sampler collects air samples at 2 l/min onto a sample holder. After the flight the ice nuclei on the sample holder are activated in the lab and counted. In August 2012 the complete setup will be used during a measurement campaign at mount "Kleiner Feldberg" close to Frankfurt. Until then we will perform test flights and additional laboratory tests.

Born, J.; Mhler, O.; Haunold, W.; Schrod, J.; Brooks, I.; Norris, S.; Brooks, B.; Hill, M.; Leisner, T.

2012-04-01

350

MEASUREMENTS OF THE PRODUCTS OF ATMOSPHERIC PHOTOCHEMICAL REACTIONS IN LABORATORY STUDIES AND IN AMBIENT AIR-RELATIONSHIPS BETWEEN OZONE AND OTHER PRODUCTS  

EPA Science Inventory

Many inorganic and organic gaseous and aerosol products are formed in the atmosphere from atmospheric photochemical reactions. The mechanisms of formation, types of products identified, smog chamber studies, and ambient air concentrations and distributions are considered in this ...

351

Aerosol Absorption Measurements in MILAGRO.  

NASA Astrophysics Data System (ADS)

During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.

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

2007-12-01

352

Ambient Dried Aerogels  

NASA Technical Reports Server (NTRS)

A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

Jones, Steven M.; Paik, Jong-Ah

2013-01-01

353

Size-partitioning of an urban aerosol to identify particle determinants involved in the proinflammatory response induced in airway epithelial cells  

PubMed Central

Background The contribution of air particles in human cardio-respiratory diseases has been enlightened by several epidemiological studies. However the respective involvement of coarse, fine and ultrafine particles in health effects is still unclear. The aim of the present study is to determine which size fraction from a chemically characterized background aerosol has the most important short term biological effect and to decipher the determinants of such a behaviour. Results Ambient aerosols were collected at an urban background site in Paris using four 13-stage low pressure cascade impactors running in parallel (winter and summer 2005) in order to separate four size-classes (PM0.030.17 (defined here as ultrafine particles), PM0.171 (fine), PM12.5(intermediate) and PM2.510 (coarse)). Accordingly, their chemical composition and their pro-inflammatory potential on human airway epithelial cells were investigated. Considering isomass exposures (same particle concentrations for each size fractions) the pro-inflammatory response characterized by Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) release was found to decrease with aerosol size with no seasonal dependency. When cells were exposed to isovolume of particle suspensions in order to respect the particle proportions observed in ambient air, the GM-CSF release was maximal with the fine fraction. In presence of a recombinant endotoxin neutralizing protein, the GM-CSF release induced by particles is reduced for all size-fractions, with exception of the ultra-fine fraction which response is not modified. The different aerosol size-fractions were found to display important chemical differences related to the various contributing primary and secondary sources and aerosol age. The GM-CSF release was correlated to the organic component of the aerosols and especially its water soluble fraction. Finally, Cytochrome P450 1A1 activity that reflects PAH bioavailability varied as a function of the season: it was maximal for the fine fraction in winter and for the ultrafine fraction in summer. Conclusion In the frame of future regulations, a particular attention should thus be paid to the ultrafine/fine (here referred to as PM1) fraction due to their overwhelming anthropogenic origin and predominance in the urban aerosol and their pro-inflammatory potential. PMID:19302717

Ramgolam, Kiran; Favez, Olivier; Cachier, Hlne; Gaudichet, Annie; Marano, Francelyne; Martinon, Laurent; Baeza-Squiban, Armelle

2009-01-01

354

During air cool process aerosol absorption detection with photothermal interferometry  

NASA Astrophysics Data System (ADS)

This paper studies the basic principle of laser photothermal interferometry method of aerosol particles absorption coefficient. The photothermal interferometry method with higher accuracy and lower uncertainty can directly measure the absorption coefficient of atmospheric aerosols and not be affected by scattered light. With Jones matrix expression, the math expression of a special polarization interferometer is described. This paper using folded Jamin interferometer, which overcomes the influence of vibration on measuring system. Interference come from light polarization beam with two orthogonal and then combine to one beam, finally aerosol absorption induced refractive index changes can be gotten with four beam of phase orthogonal light. These kinds of styles really improve the stability of system and resolution of the system. Four-channel detections interact with interference fringes, to reduce the light intensity `zero drift' effect on the system. In the laboratory, this device typical aerosol absorption index, it shows that the result completely agrees with actual value. After heated by laser, cool process of air also show the process of aerosol absorption. This kind of instrument will be used to monitor ambient aerosol absorption and suspended particulate matter chemical component. Keywords: Aerosol absorption coefficient; Photothermal interferometry; Suspended particulate matter.

Li, Baosheng; Xu, Limei; Huang, Junling; Ma, Fei; Wang, Yicheng; Li, Zhengqiang

2014-11-01

355

Nitrosyl sulfuric acid and stratospheric aerosols  

Microsoft Academic Search

From information found in the atmospheric and chemical literature, we propose that nitrosyl sulfuric acid (NSA), NOHSO4, may play an important role in stratospheric chemistry. In one study, NSA was observed as a slurry of crystals in about a third of the aerosol particles collected between 15 and 20 km. From the chemical literature, we find that NSA is formed

Joel D. Burley; H. S. Johnston

1992-01-01

356

INDOOR CONCENTRATION MODELING OF AEROSOL STRONG ACIDITY  

EPA Science Inventory

A model for estimating indoor concentrations of acid aerosol was applied to data collected during the summer of 1989, in a densely populated location in New Jersey. he model, from a study of a semi-rural community in Pennsylvania, was used to estimate indoor concentrations of aer...

357

Aerosol deposition in the human respiratory tract  

NASA Astrophysics Data System (ADS)

Rising sulfur dioxide emissions from increased coal combustion present risks, not only of acid rain, but also to health by inhalation of the SO 2 and acid to the lung. We are investigating human inhalation of ppm SO 2 concentrations mixed with aerosol of submicrometer aqueous salt droplets to determine the effects on lung function and body chemistry. Unlike some investigators, we emphasize ammonium sulfate and trace element aerosol composition which simulates ambient air; aerosol pH, relative humidity, and temperature control to reveal gas-particle reaction mechanisms; and dose estimates from length of exposure, SO 2 concentration, and a direct measurement of respiratory deposition of aerosol as a function of particle size by cascade impactor sampling and elemental analysis by PIXE. Exposures, at rest or during exercise, are in a walk-in chamber at body temperature and high humidity to simulate Florida's summer climate. Lung function measurement by spirometry is carried out immediately after exposure. The results are significant in relating air quality to athletic performance and to public health in the southeastern United States.

Winchester, John W.; Jones, Donald L.; Mu-tian, Bi

1984-04-01

358

Overview of the Light Aircraft Aerosol Research Inlet (LAARI)  

NASA Astrophysics Data System (ADS)

Aircraft provide a mobile platform for measuring vertical profile aerosol properties. The efficacy of these measurements, however, is constrained by the aerosol inlet sampling efficiency. Larger particles are often lost to turbulent deposition and impaction inside the inlet and sampling lines, respectively. This precludes the measurement of coarse mode particles, important to visibility and radiative transfer studies. Turbulent deposition of large particles occurs when the sample air stream slows down within the inlet from the aircraft velocity to the recommended sampling velocities of the aerosol instruments (\\sim10 m s-1). Low-turbulence inlets that reduce turbulent deposition through the use of a porous diffuser cones are necessary for large aircraft with air speeds of 80 to 200 m s-1, but these are not feasible for light aircraft because of space and power requirements and may not even be necessary given the low air speeds of small aircraft. We have designed an aerosol inlet for a light aircraft platform with an average air speed of 60 m s-1 and a sample flow rate of 28.5 L min-1. The hemi-elliptical shaped, stainless steel inlet is 12.7 cm long. The front orifice has a 0.3175 cm diameter and the internal diameter expands to 0.9525 cm over a length of 9.2075 cm at an included angle of 4.3\\deg. The linear velocity of the sample stream as it exits the inlet is 6.7 m s-1. The calculated Reynolds number (Re) at the opening is 11,430 and decreases to 3,811 at the inlet terminus, with a pressure drop across the inlet opening of only 42 mb at an average flight temperature and pressure. Sampling line impaction is reduced by decreasing the number of bends upstream of the instruments. We have accomplished this by designing a parallel sampling manifold that splits the sample stream into four separate streams, three of which are split from the primary sample stream at an angle of 15\\deg. Theoretical investigations of sample flow and particle losses are underway with Computational Fluid Dynamics (CFD) software from FlowLab. Wind tunnel analyses using a Vibrating Orifice Aerosol Generator (VOAG) with optical particle counters upstream and downstream of the inlet and sampling lines will validate the theoretical calculations and provide empirical sampling efficiency values. This new inlet design will facilitate the more efficient collection of ambient particles, especially those in the coarse mode, from light aircraft. Because light aircraft are less expensive to operate than large aircraft and can make measurements in the lower atmosphere on a more routine basis, the Light Aircraft Aerosol Research Inlet (LAARI) will herald a new era of measurement capabilities in satellite validation work, column closure tests, and climate change studies.

Bueno, P. A.; Taubman, B. F.; Marufu, L. T.

2004-12-01

359

Titan's aerosols properties determined with the Aerosol Collector and Pyrolyzer experiment of the Huygens probe  

NASA Astrophysics Data System (ADS)

Titan s organic aerosols play a significant role in the physical properties of the atmosphere and the subsequent meteorology the properties of the surface where they can have accumulated in significant amounts and in the cycle of the organic matter of the Saturn s satellite which is of primary importance from an astrobiological point of view However the amount of direct data dealing with the Titan s aerosols properties is quite low and the data recovered from the Cassini and the Huygens probes should significantly enhance our knowledge about these particles Except some spectral data that should provide morphological and some indirect compositional information on the aerosols the first in situ compositional data were recovered by the Aerosol Collector and Pyrolyser ACP experiment of the Huygens probe This experiment collected two distinct atmospheric samples over separate altitude ranges 130-35 km and 25-20 km respectively during the Huygens probe descent The samples were pyrolysed heated up to 600oC separately and the gases evolved from the samples were analysed with the Gas Chromatograph Mass Spectrometer GCMS instrument of the Huygens probe primarily devoted to the analysis of atmospheric gases From the results of the chemical analysis of the collected aerosols by pyrolysis at 600oC it was clearly shown that the aerosol particles include a solid organic refractory core Moreover NH3 and HCN were the first identified fingerprints of the chemical structure of the complex organics constituting this core proving the inclusion of nitrogen in the

Israel, G.; Szopa, C.; Cabane, M.; Brun, J. F.; Coll, P.; Nguyen, M. J.; Coscia, D.; Raulin, F.; Acp Team

360

Annual cycle of Antarctic Baseline Aerosol: A Benchmark for Natural Aerosol Processes  

NASA Astrophysics Data System (ADS)

An ongoing challenge in attributing anthropogenic climate change is to distinguish anthropogenic and natural changes of atmospheric composition, e.g. concerning atmospheric aerosol and its climate effects. Aerosol properties measured at pristine locations, to the extend they still exist, can serve as a climate model benchmark for verifying the representation of natural aerosol processes in the model. To this end, a recent study (Fiebig et al., 2013) investigates the annual cycle of the baseline aerosol observed at the atmospheric observatory of the Norwegian Antarctic research station Troll (Queen Maud Land, 72.0166 S, 2.5333 E, 1309 m a.s.l.). The aerosol monitoring program at Troll observatory includes the aerosol scattering coefficient at 450, 550, and 700 nm wavelength, and the particle number size distribution (PNSD, 0.03 ?m < Dp < 0.8 ?m) (Hansen et al., 2009). The time series of both instruments, collected since Feb. 2007, show a distinct annual cycle of the aerosol properties associated with baseline air masses, i.e. those not corresponding to peaks of any origin. Comparison of the aerosol scattering coefficient measured by nephelometer and calculated from the DMPS measurements by Mie-theory assuming an (NH4)2SO4 composition show a correlation coefficient of ~ 0.8, confirming a common origin of both annual cycles. The same annual cycle in baseline aerosol scattering coefficient and particle number concentration / size distribution as found at Troll can be detected in corresponding data collected at South Pole and Dome C atmospheric observatories. This shows that the annual cycle of baseline aerosol properties at Troll isn't a local phenomenon, but common to Central Antarctic baseline air masses. Using backward plume calculation by the Lagrangian transport model FLEXPART, as well as ground-level ozone data collected at Troll, it is demonstrated that the air masses associated with baseline aerosol loadings at Troll originate from the free troposphere an lower stratospheric region and descend over the Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters

Fiebig, Markus; Hirdman, David; Lunder, Chris R.; Ogren, John A.; Solberg, Sverre; Thompson, Rona L.; Stohl, Andreas

2014-05-01

361

Aerosol MTF revisited  

NASA Astrophysics Data System (ADS)

Different views of the significance of aerosol MTF have been reported. For example, one recent paper [OE, 52(4)/2013, pp. 046201] claims that the aerosol MTF "contrast reduction is approximately independent of spatial frequency, and image blur is practically negligible". On the other hand, another recent paper [JOSA A, 11/2013, pp. 2244-2252] claims that aerosols "can have a non-negligible effect on the atmospheric point spread function". We present clear experimental evidence of common significant aerosol blur and evidence that aerosol contrast reduction can be extremely significant. In the IR, it is more appropriate to refer to such phenomena as aerosol-absorption MTF. The role of imaging system instrumentation on such MTF is addressed too.

Kopeika, Norman S.; Zilberman, Arkadi; Yitzhaky, Yitzhak

2014-05-01

362

Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean  

NASA Astrophysics Data System (ADS)

The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20 S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20 S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500-1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

Twohy, C. H.; Anderson, J. R.; Toohey, D. W.; Andrejczuk, M.; Adams, A.; Lytle, M.; George, R. C.; Wood, R.; Saide, P.; Spak, S.; Zuidema, P.; Leon, D.

2013-03-01

363

Triple Isotopic Composition of Atmospheric Carbonates: A Novel Technique to Identify Heterogeneous Chemistry on Aerosol Surfaces in Polluted Environment  

NASA Astrophysics Data System (ADS)

In the ambient atmosphere, the physical and chemical properties of aerosol vary greatly between location and time due to various heterogeneous and photochemical reactions in the atmosphere. In polluted urban environments, the aerosol and gaseous mixtures interact to produce new compounds and particulates; consequently humans are exposed to many as yet undetected species. Studies of actual chemically-active, airborne particulates can better address the interaction of complex particulate and gaseous pollutant mixtures, however, it is notoriously difficult to measure chemical transformations of aerosols. Here we describe a new technique that can be used to understand the chemical transformation occurring on the surface of aerosols and thus to quantify the interaction of gaseous species and aerosol in the atmosphere. Fine and coarse aerosol samples were collected on filter papers in La Jolla, CA, USA for one week. The aerosol samples were digested with phosphoric acid and CO2 released was purified chromatographically and analyzed for 13 C. To obtain independent measurements of oxygen isotopes, the CO2 was fluorinated and oxygen gas obtained was analyzed using Mat253 Isotope Ratio Mass Spectrometer. The data indicated an excess 17O (0.6 to 4) in atmospheric carbonates. The oxygen isotope anomaly in atmospheric carbonates has been observed for the first time and it showed a highly significant correlation (r2 = 0.90) with urban index; an indirect measure of ozone chemistry. The ?13C in atmospheric carbonates was found to vary from -18 to -40. Controlled laboratory experiments to understand the origin and variation in the C and O isotopic composition of atmospheric carbonates were conducted using various mineral surfaces. Isotopic measurements of in-situ formed carbonated on CaOH, CaO, MgO, SiO2,Cu, CuO, Ni and Fe2O3 due to chemisorbed CO2 in the presence of thin water films were performed and we found that the ?13C in these carbonates ranged from -12 to -24. These results suggests that the variation in ?13C in atmospheric carbonates may be used to assess in-situ carbonate formation as pedogenic carbonates were enriched (?13C = -4 to -16) compared to the atmospheric carbonates. The implication of oxygen isotopic anomaly and in-situ carbonate formation under various atmospheric conditions will be discussed.

Shaheen, R.; Horn, J.; Dominguez, G.; Masterson, A.; Ivanov, A. V.; Thiemens, M. H.

2009-12-01

364

Correlation of Secondary Organic Aerosol with Odd Oxygen in Mexico City  

SciTech Connect

Data collected from a mountain location within the Mexico City limits are used to demonstrate a correlation between secondary organic aerosol and odd-oxygen (O3 + NO2). Positive matrix factorization techniques are employed to separate organic aerosol components: hydrocarbon-like organic aerosol; oxidized-organic aerosol; and biomass burning organic aerosol. The measured hydrocarbon-like organic aerosol is correlated with urban CO (81) g m-3 ppmv-1. The measured oxidized-organic aerosol is associated with photochemical oxidation products and correlates with odd-oxygen with an apparent slope of (70-120) g m-3 ppmv-1. The dependence of the oxidized-organic aerosol to odd-oxygen correlation on the nature of the gas-phase hydrocarbon profile is discussed.

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

2008-08-05

365

Titan's aerosols properties determined with the Aerosol Collector and Pyrolyzer experiment of the Huygens probe  

NASA Astrophysics Data System (ADS)

Titan's organic aerosols play a significant role in the physical properties of the atmosphere, and the subsequent meteorology, the properties of the surface where they can have accumulated in significant amounts, and in the cycle of the organic matter of the Saturn's satellite which is of primary importance from an astrobiological point of view. However, the amount of direct data dealing with the Titan's aerosols properties is quite low, and the data recovered from the Cassini and the Huygens probes should significantly enhance our knowledge about these particles. Except some spectral data that should provide morphological and some indirect compositional information on the aerosols, the first in situ compositional data were recovered by the Aerosol Collector and Pyrolyser (ACP) experiment of the Huygens probe. This experiment collected two distinct atmospheric samples over separate altitude ranges (130-35 km and 25- 20 km, respectively) during the Huygens probe descent. The samples were pyrolysed (heated up to 600 C) separately and the gases evolved from the samples were analysed with the Gas Chromatograph/Mass Spectrometer (GCMS) instrument of the Huygens probe, primarily devoted to the analysis of atmospheric gases. From the results of the chemical analysis of the collected aerosols by pyrolysis at 600 C, it was clearly shown that the aerosol particles include a solid organic refractory core. Moreover NH3 and HCN were the first identified fingerprints of the chemical structure of the complex organics constituting this core, proving the inclusion of nitrogen in the process for the formation of Titan's aerosols. In this paper, we will present the results of the investigation of the pyrolysis of the aerosols at 600 C, as well as the results of further investigations led on the intermediary heating steps (at 30 C and 250 C).

Israel, G.; Szopa, C.; Cabane, M.; Brun, J. F.; Coll, P.; Nguyen, M. J.; Coscia, D.; Raulin, F.; Acp Team

366

Indirect and Semi-Direct Aerosol Campaign: The Impact of Arctic Aerosols on Clouds  

SciTech Connect

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the arctic boundary layer in the vicinity of Barrow, Alaska was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) sponsored by the Department of Energy Atmospheric Radiation Measurement (ARM) and Atmospheric Science Programs. The primary aim of ISDAC was to examine indirect effects of aerosols on clouds that contain both liquid and ice water. The experiment utilized the ARM permanent observational facilities at the North Slope of Alaska (NSA) in Barrow. These include a cloud radar, a polarized micropulse lidar, and an atmospheric emitted radiance interferometer as well as instruments specially deployed for ISDAC measuring aerosol, ice fog, precipitation and spectral shortwave radiation. The National Research Council of Canada Convair-580 flew 27 sorties during ISDAC, collecting data using an unprecedented 42 cloud and aerosol instruments for more than 100 hours on 12 different days. Data were obtained above, below and within single-layer stratus on 8 April and 26 April 2008. These data enable a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds influenced by different surface conditions. Observations acquired on a heavily polluted day, 19 April 2008, are enhancing this understanding. Data acquired in cirrus on transit flights between Fairbanks and Barrow are improving our understanding of the performance of cloud probes in ice. Ultimately the ISDAC data will be used to improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales, and to determine the extent to which long-term surface-based measurements can provide retrievals of aerosols, clouds, precipitation and radiative heating in the Arctic.

McFarquhar, Greg; Ghan, Steven J.; Verlinde, J.; Korolev, Alexei; Strapp, J. Walter; Schmid, Beat; Tomlinson, Jason M.; Wolde, Mengistu; Brooks, Sarah D.; Cziczo, Daniel J.; Dubey, Manvendra K.; Fan, Jiwen; Flynn, Connor J.; Gultepe, Ismail; Hubbe, John M.; Gilles, Mary K.; Laskin, Alexander; Lawson, Paul; Leaitch, W. R.; Liu, Peter S.; Liu, Xiaohong; Lubin, Dan; Mazzoleni, Claudio; Macdonald, A. M.; Moffet, Ryan C.; Morrison, H.; Ovchinnikov, Mikhail; Shupe, Matthew D.; Turner, David D.; Xie, Shaocheng; Zelenyuk, Alla; Bae, Kenny; Freer, Matthew; Glen, Andrew

2011-02-01

367

Atmospheric lifetime of caesium-137 as an estimate of aerosol lifetime -quantified from global measurements in the months after the Fukushima Dai-ichi nuclear accident  

NASA Astrophysics Data System (ADS)

Radionuclides like caesium-137 (137Cs) can be emitted to the atmosphere in great quantities during nuclear accidents and are of significant health impact. A global set of radionuclide measurements collected over several months after the accidental release from the Fukushima Dai-ichi nuclear power plant in March 2011 has been used to estimate the atmospheric lifetime of 137Cs. Lifetime is here defined as the e-folding time scale (the time interval in which the exponential decay of the 137Cs quantity has decreased by factor of e). The estimated atmospheric lifetime of 137Cs can also be used as an estimate of the lifetime of aerosols in the atmosphere. This is based on the fact that 137Cs attaches to the ambient accumulation-mode (AM) aerosols and trace their fate in the atmosphere. The 137Cs "tags" the AM aerosols and both the 137Cs and AM aerosols are removed simultaneously from the atmosphere by scavenging within clouds, precipitation and dry deposition. The 137Cs emitted from Fukushima attached mainly to sulphate aerosols in the size range 0.1-2 ?m diameter. Measured 137Cs activity concentrations from several stations spread mostly over the Northern Hemisphere were evaluated, and the decrease in activity concentrations over time (after correction for radioactive decay) reflects the removal of aerosols by wet and dry deposition. Corrections for air mass transport were made using measurements of the noble gas xenon-133 (133Xe) which was also released during the accident. This noble gas does not attach to the aerosols and was thus used as a passive tracer of air mass transport. The atmospheric lifetime of 137Cs was estimated to 10.0-13.9 days during April and May 2011. This represents the atmospheric lifetime of a "background" AM aerosol well mixed in the extratropical northern hemisphere troposphere. It is expected that the lifetime of this vertically mixed background aerosol is longer than the lifetime of fresh AM aerosols directly emitted from surface sources. Possible caveats like late emissions and resuspension were found not to significantly affect the results. The estimated lifetimes from this study are within the much larger and uncertain range of previously observation-based studies of aerosol lifetimes (less than 4 days to more than a month). However, modelled aerosol lifetimes from air quality and climate models typically range 3-7 days which is substantially lower than the mean AM lifetimes obtained from this study. The difference points towards a too quick removal of AM aerosol in the models and further research on the cause of this discrepancy is warranted. Too short modelled AM aerosol lifetimes would have serious implications for air quality and climate model predictions. By running several major climate and air quality models for the Fukushima case, an evaluation of the models performance compared to the measurements can be directly obtained.

Iren Kristiansen, Nina; Stohl, Andreas; Wotawa, Gerhard

2013-04-01

368

Comparison of Moderate Resolution Imaging Spectroradiometer (MODIS) and Aerosol Robotic Network (AERONET) remote-sensing retrievals of aerosol fine mode fraction over ocean  

NASA Astrophysics Data System (ADS)

Aerosol particle size is one of the fundamental quantities needed to determine the role of aerosols in forcing climate, modifying the hydrological cycle, and affecting human health and to separate natural from man-made aerosol components. Aerosol size information can be retrieved from remote-sensing instruments including satellite sensors such as Moderate Resolution Imaging Spectroradiometer (MODIS) and ground-based radiometers such as Aerosol Robotic Network (AERONET). Both satellite and ground-based instruments measure the total column ambient aerosol characteristics. Aerosol size can be characterized by a variety of parameters. Here we compare remote-sensing retrievals of aerosol fine mode fraction over ocean. AERONET retrieves fine mode fraction using two methods: the Dubovik inversion of sky radiances and the O'Neill inversion of spectral Sun measurements. Relative to the Dubovik inversion of AERONET sky measurements, MODIS slightly overestimates fine fraction for dust-dominated aerosols and underestimates in smoke- and pollution-dominated aerosol conditions. Both MODIS and the Dubovik inversion overestimate fine fraction for dust aerosols by 0.1-0.2 relative to the O'Neill method of inverting AERONET aerosol optical depth spectra. Differences between the two AERONET methods are principally the result of the different definitions of fine and coarse mode employed in their computational methodologies. These two methods should come into better agreement as a dynamic radius cutoff for fine and coarse mode is implemented for the Dubovik inversion. MODIS overestimation in dust-dominated aerosol conditions should decrease significantly with the inclusion of a nonspherical model.

Kleidman, R. G.; O'Neill, N. T.; Remer, L. A.; Kaufman, Y. J.; Eck, T. F.; Tanr, Didier; Dubovik, Oleg; Holben, B. N.

2005-11-01

369

Aerosol characteristics at a rural station in southern peninsular India during CAIPEEX-IGOC: physical and chemical properties.  

PubMed

To understand the boundary layer characteristics and pathways of aerosol-cloud interaction, an Integrated Ground Observational Campaign, concurrent with Cloud Aerosol Interaction and Precipitation Enhancement Experiment, was conducted by the Indian Institute of Tropical Meteorology, Pune, under Ministry of Earth Sciences at Mahabubnagar (a rural environment, which is ~100km away from an urban city Hyderabad in Andhra Pradesh), during the period of July-November 2011. Collected samples of PM2.5 and PM10 were analyzed for water-soluble ionic species along with organic carbon (OC) and elemental carbon (EC). During study period, the average mass concentrations of PM2.5 and PM10 were about 50(10) and 69(14)??gm(-3), respectively, which are significantly higher than the prescribed Indian National Ambient Air Quality Standards values. The chemical species such as sum of anions and cations from measured chemical constituents were contributed to be 31.27 and 38.49% in PM2.5 and 6.35 and 5.65% to the PM10, whereas carbonaceous species contributed ~17.3 and 20.47% for OC and ~3.0 and 3.10% for EC, respectively. The average ratio of PM2.5/PM10 during study period was ~0.73(0.2), indicating that the dominance of fine size particles. Carbonaceous analysis results showed that the average concentration of OC was 14 and 8.7?gm(-3), while EC was 2.1 and 1.5?gm(-3) for PM10 and PM2.5, respectively. The ratios between OC and EC were estimated, which were 6.6 and 5.7 for PM10 and PM2.5, suggesting the presence of secondary organic aerosol. Total carbonaceous aerosol accounts 23% of PM10 in which the contribution of OC is 20% and EC is 3%, while 20% of PM2.5 mass in which the contribution of OC is 17% and EC is 3%. Out of the total aerosols mass, water-soluble constituents contributed an average of 45% in PM10 and 38% in PM2.5 including about 39% anions and 6% cations in PM10, while 31% anions and 7% cations in PM2.5 aerosol mass collectively at study site. PMID:25416502

Bisht, D S; Srivastava, A K; Pipal, A S; Srivastava, M K; Pandey, A K; Tiwari, S; Pandithurai, G

2014-11-23

370

AEROSOL PARTICLE COLLECTOR DESIGN STUDY  

SciTech Connect

A computational evaluation of a particle collector design was performed to evaluate the behavior of aerosol particles in a fast flowing gas stream. The objective of the work was to improve the collection efficiency of the device while maintaining a minimum specified air throughput, nominal collector size, and minimal power requirements. The impact of a range of parameters was considered subject to constraints on gas flow rate, overall collector dimensions, and power limitations. Potential improvements were identified, some of which have already been implemented. Other more complex changes were identified and are described here for further consideration. In addition, fruitful areas for further study are proposed.

Lee, S; Richard Dimenna, R

2007-09-27

371

Yellowstone Attenuation Tomography from Ambient Seismic Noise  

NASA Astrophysics Data System (ADS)

The goal of this study is to create a tomographic attenuation image for the Yellowstone region by analyzing ambient seismic noise. An attenuation image generated from ambient noise should provide more information about the structure and properties beneath Yellowstone, especially the caldera, which is known to be active. I applied the method of Lawrence & Prieto [2011] to examine lateral variations in the attenuation structure of Yellowstone. Ambient noise data were collected from broadband seismic stations located around Yellowstone National Park from 1999-2013. Noise correlation functions derived from cross correlations of the ambient noise at two stations were used to calculate a distance dependent decay (an attenuation coefficient) at each period and distance. An inversion was then performed to isolate and localize the spatial attenuation coefficients within the study area. I observe high amplitude decay of the ambient noise at the Yellowstone caldera, most likely due to elevated temperature and crustal melts caused by volcanism, geothermal heat flow, and hydrothermal activity such as geysers.

Doungkaew, N.; Seats, K.; Lawrence, J. F.

2013-12-01

372

AMBIENT CARBON MONOXIDE MONITOR  

EPA Science Inventory

A portable instrument has been designed and two units have been built to monitor the concentration of CO in ambient air. The air flows through a sampling section that is approximately 43 cm long with a 28-pass optical system that produces a total path of 12 meters. Gas-filter cor...

373

A simple method for estimation of coagulation efficiency in mixed aerosols. [environmental pollution control  

NASA Technical Reports Server (NTRS)

Aerosols of KBr and AgNO3 were mixed, exposed to light in a glass tube and collected in the dark. About 15% of the collected material was reduced to silver upon development. Thus, two aerosols of particles that react to form a photo-reducible compound can be used to measure coagulation efficiency.

Dimmick, R. L.; Boyd, A.; Wolochow, H.

1975-01-01

374

ANALYSIS OF HOUSTON AEROSOL SAMPLES BY GC/MS (GAS CHROMATOGRAPHY-MASS SPECTROMETRY) METHODS  

EPA Science Inventory

An analysis procedure developed to give a qualitative and quantitative analysis for organic compounds adsorbed on aerosols collected by Hi-Vol filters was adapted and applied to a similar analysis of aerosols collected by dichotomous filters. Analysis was conducted for five dicho...

375

Spatial and temporal variability of sources of ambient fine particulate matter (PM2.5) in California  

NASA Astrophysics Data System (ADS)

To identify major sources of ambient fine particulate matter (PM2.5, dp < 2.5 ?m) and quantify their contributions in the state of California, a positive matrix factorization (PMF) receptor model was applied on Speciation Trends Network (STN) data, collected between 2002 and 2007 at eight distinct sampling locations, including El Cajon, Rubidoux, Los Angeles, Simi Valley, Bakersfield, Fresno, San Jose, and Sacramento. Between five to nine sources of fine PM were identified at each sampling site, several of which were common among multiple locations. Secondary aerosols, including secondary ammonium nitrate and ammonium sulfate, were the most abundant contributor to ambient PM2.5 mass at all sampling sites, except for San Jose, with an annual average cumulative contribution of 26 to 63%, across the state. On an annual average basis, vehicular emissions (including both diesel and gasoline vehicles) were the largest primary source of fine PM at all sampling sites in southern California (17-18% of total mass), whereas in Fresno and San Jose, biomass burning was the most dominant primary contributor to ambient PM2.5 (27 and 35% of total mass, respectively), in general agreement with the results of previous source apportionment studies in California. In Bakersfield and Sacramento, vehicular emissions and biomass burning displayed relatively equal annual contributions to ambient PM2.5 mass (12 and 25%, respectively). Other commonly identified sources at all sites included aged and fresh sea salt and soil, which contributed to 0.5-13%, 2-27%, and 1-19% of the total mass, respectively, across all sites and seasons. In addition, a few minor sources were identified exclusively at some of the sites (e.g., chlorine sources, sulfate-bearing road dust, and different types of industrial emissions). These sources overall accounted for a small fraction of the total PM mass across the sampling locations (1 to 15%, on an annual average basis).

Hasheminassab, S.; Daher, N.; Saffari, A.; Wang, D.; Ostro, B. D.; Sioutas, C.

2014-11-01

376

Spatial and temporal variability of sources of ambient fine particular matter (PM2.5) in California  

NASA Astrophysics Data System (ADS)

To identify major sources of ambient fine particulate matter (PM2.5, dp<2.5 ?m) and quantify their contributions in the state of California, positive matrix factorization (PMF) receptor model was applied on speciation trends network (STN) data, collected between 2002 and 2007 at 8 distinct sampling locations, including El Cajon, Rubidoux, Los Angeles, Simi Valley, Bakersfield, Fresno, San Jose, and Sacramento. Between five to nine sources of fine PM were identified at each sampling site, several of which were common among multiple locations. Secondary aerosols, including secondary ammonium nitrate and ammonium sulfate, were the most abundant contributor to ambient PM2.5 at all sampling sites, except for San Jose, with an annual average cumulative contribution of 26 to 63%, across the state. On an annual average basis, vehicular emissions (including both diesel and gasoline vehicles) were the largest primary source of fine PM at all sampling sites in southern California (17-18% of total mass), whereas in Fresno and San Jose, biomass burning was the most dominant primary contributor to ambient PM2.5 (27 and 35% of total mass, respectively), in general agreement with the results of previous source apportionment studies in California. In Bakersfield and Sacramento, vehicular emissions and biomass burning displayed relatively equal annual contributions to ambient PM2.5 mass (12 and 25%, respectively). Other commonly identified sources at all sites included aged and fresh sea salt as well as soil, which contributed to 0.5-13%, 2-27%, and 1-19% of the total mass, respectively, across all sites and seasons. In addition, few minor sources were exclusively identified at some of the sites (e.g. chlorine sources, sulfate-bearing road dust, and different types of industrial emissions). These sources overall accounted for a small fraction of the total PM mass across the sampling locations (1 to 15%, on an annual average basis).

Hasheminassab, S.; Daher, N.; Saffari, A.; Wang, D.; Ostro, B. D.; Sioutas, C.

2014-08-01

377

How Well Do State-of-the-Art Techniques Measuring the Vertical Profile of Tropospheric Aerosol Extinction Compare?  

SciTech Connect

The recent U.S. Department of Energy Atmospheric Radiation Measurements (ARM) Aerosol Intensive Observation Period (AIOP, May 2003) yielded one of the best measurement sets obtained to-date to assess our ability to measure the vertical profile of ambient aerosol extinction. During one month, a heavily instrumented aircraft with well characterized aerosol sampling ability carrying well proven and new aerosol instrumentation, devoted most of the 60 available flight hours to flying vertical profiles over the heavily instrumented ARM Southern Great Plains (SGP) Climate Research Facility (CRF). This allowed us to compare vertical extinction profiles obtained from 6 different instruments: airborne Sun photometer, airborne nephelometer/absorption photometer, airborne cavity ring-down system, ground-based Raman lidar and two ground-based elastic backscatter lidars. We find the in situ measurements to be biased low (2 - 4 Mm 1 equivalent to 12-17% in the visible, or 45% in the near-infrared) when compared to airborne sunphotometer extinction. On the other hand, we find that with respect to AATS-14, the lidar ?ep(?) are biased high. Bias differences are 0.004 Km-1 (13%) and 0.007 Km-1 (24%) for the two elastic back-scatter lidars (MPLARM and MPLNET, ? = 523 nm) and 0.029 Km-1 (54%) for the Raman lidar (? = 355 nm). An unnoticed loss of sensitivity of the Raman lidar had occurred leading up to AIOP and we expect better agreement from the recently restored system. Looking at the collective results from six field campaigns conducted since 1996, airborne in situ measurements of extinction tend to be biased slightly low (17% at visible wavelengths) when compared to airborne sunphotometer extinction. On the other hand, extinction derived from lidars tend to have no or positive biases. We conclude that the error associated with measuring the tropospheric vertical profile of the ambient aerosol extinction with current state-of-the art instrumentation is 15-20% at visible wavelengths and potentially larger in the UV near-infrared.

Schmid, Beat; Ferrare, Richard; Flynn, Connor M.; Elleman, Robert; Covert, David; Strawa, A.; Welton, E J.; Turner, David D.; Jonsson, Haf; Redemann, Jens; Eilers, J.; Ricci, K.; Hallar, A. G.; Clayton, M. B.; Michalsky, Joseph J.; Smirnov, A.; Holben, B. N.; Barnard, James C.

2006-02-01

378

How Well do State-of-the-Art Techniques Measuring the Vertical Profile of Tropospheric Aerosol Extinction Compare?  

NASA Technical Reports Server (NTRS)

The recent Department of Energy Atmospheric Radiation Measurement (ARM) Aerosol Intensive Operations Period (AIOP, May 2003) yielded one of the best measurement sets obtained to date to assess our ability to measure the vertical profile of ambient aerosol extinction sigma(ep)(lambda) in the lower troposphere. During one month, a heavily instrumented aircraft with well-characterized aerosol sampling ability carrying well-proven and new aerosol instrumentation devoted most of the 60 available flight hours to flying vertical profiles over the heavily instrumented ARM Southern Great Plains (SGP) Climate Research Facility (CRF). This allowed us to compare vertical extinction profiles obtained from six different instruments: airborne Sun photometer (AATS-14), airborne nephelometer/absorption photometer, airborne cavity ring-down system, groundbased Raman lidar, and two ground-based elastic backscatter lidars. We find the in situ measured sigma(ep)(lambda) to be lower than the AATS-14 derived values. Bias differences are 0.002-0.004 Km!1 equivalent to 13-17% in the visible, or 45% in the near-infrared. On the other hand, we find that with respect to AATS-14, the lidar sigma(ep)(lambda) are higher: Bias differences are 0.004 Km(-1) (13%) and 0.007 Km(-1) (24%) for the two elastic backscatter lidars (MPLNET and MPLARM, lambda = 523 nm) and 0.029 Km(-1) (54%) for the Raman lidar (lambda = 355 nm). An unnoticed loss of sensitivity of the Raman lidar had occurred leading up to AIOP, and we expect better agreement from the recently restored system. Looking at the collective results from six field campaigns conducted since 1996, airborne in situ measurements of sigma(ep)(lambda) tend to be biased slightly low (17% at visible wavelengths) when compared to airborne Sun photometer sigma(ep)(lambda). On the other hand, sigma(ep)(lambda) values derived from lidars tend to have no or positive biases. From the bias differences we conclude that the typical systematic error associated with measuring the tropospheric vertical profile of the ambient aerosol extinction with current state-of-the-art instrumentation is 15-20% at visible wavelengths and potentially larger in the UV and near-infrared.

Schmid, B.; Ferrare, R.; Flynn, C.; Elleman, R.; Covert, D.; Strawa, A.; Welton, E.; Turner, D.; Jonsson, H.; Redemann, J.; Eilers, J.; Ricci, K.; Hallar, A. G.; Clayton, M.; Michalsky, J.; Smirnov, A.; Holben, B.; Barnard, J.

2006-01-01

379

Physical properties, chemical composition, sources, spatial distribution and sinks of indoor aerosol particles in a university lecture hall  

NASA Astrophysics Data System (ADS)

PM10 mass, particle number (N) and CO2 concentrations, particle number size distributions and meteorological parameters were determined with high time resolution, and daily aerosol samples were collected in the PM10-2.0 and PM2.0 size fractions for chemical analysis in the middle of a university lecture hall for one week. Median concentrations for the PM10 mass and N of 15.3 ?g m-3 and 3.7 103 cm-3, respectively were derived. The data are substantially smaller than the related outdoor levels or typical values for residences. There were considerable concentration differences for workdays, weekends and various lectures. Main sources of PM10 mass include the usage of chalk sticks for writing, wiping the blackboard, ordinary movements and actions of students and cleaning. High PM10 mass concentration levels up to 100 ?g m-3 were realised for short time intervals after wiping the blackboard. The mass concentrations decreased rapidly after the emission source ceased to be active. Two classes of coarse particles were identified. General indoor dust particles exhibited a residence time of approximately 35 min, while the residence time for the chalk dust particles was approximately 20 min as lower estimates. Emission source rate for wiping the blackboard was estimated to be between 8 and 14 mg min-1. This represents a substantial emission rate but the source is active only up to 1 min. Suspension of the chalk (made mainly of gypsum) dust particles was confirmed by enrichment of Ca and S in the hall with respect to ambient urban aerosol. Contribution of ambient aerosol via the heating, ventilation and air conditioning (HVAC) facility was considerable for time intervals when the indoor sources of PM10 mass were not intensive. The HVAC facility introduces, however, the major amount of aerosol particles from the outdoors as far as their number concentration is regarded. Mean contribution of ultrafine particles to the total particle number was (69 7)%, which is smaller than for the related outdoor urban environment. This can indicate aged ultrafine aerosol. The major amounts of CO2 arrive from the corridors through open doors by infiltration. Spatial distribution of the PM10 mass concentration within the hall was derived by CFD modelling, and spatial inhomogeneities were obtained.

Salma, I.; Dosztly, K.; Borss, T.; Sveges, B.; Weidinger, T.; Kristf, G.; Pter, N.; Kertsz, Zs.

2013-01-01

380

Bacterial Communities in Aerosols and Manure Samples from Two Different Dairies in Central and Sonoma Valleys of California  

Microsoft Academic Search

Aerosols have been suspected to transport food pathogens and contaminate fruits and vegetables grown in close proximity to concentrated animal feeding operations, but studies are lacking that substantiate such transport. To monitor the potential transport of bacteria originated from fresh or dry manure through aerosols on a dairy, we identified by 16S rRNA sequencing, bacteria in aerosols collected within 2

Subbarao V. Ravva; Chester Z. Sarreal; Robert E. Mandrell

2011-01-01