The Experts below are selected from a list of 36684 Experts worldwide ranked by ideXlab platform

Jose L Jimenez - One of the best experts on this subject based on the ideXlab platform.

  • evaluation of the new capture vaporizer for Aerosol mass spectrometers ams through field studies of inorganic species
    Aerosol Science and Technology, 2017
    Co-Authors: Pedro Campuzanojost, Douglas A Day, Douglas R Worsnop, John T Jayne, Manjula R Canagaratna, Philip Croteau, Jose L Jimenez
    Abstract:

    The Aerosol mass spectrometer (AMS) and Aerosol chemical speciation monitor (ACSM) are widely used for quantifying Aerosol Composition. The quantification uncertainty of these instruments is domina...

  • evaluation of the new capture vaporizer for Aerosol mass spectrometers ams through field studies of inorganic species
    Aerosol Science and Technology, 2017
    Co-Authors: Weiwei Hu, Pedro Campuzanojost, Douglas R Worsnop, Manjula R Canagaratna, Philip Croteau, J T Jayne, Jose L Jimenez
    Abstract:

    ABSTRACTThe Aerosol mass spectrometer (AMS) and Aerosol chemical speciation monitor (ACSM) are widely used for quantifying Aerosol Composition. The quantification uncertainty of these instruments is dominated by the collection efficiency (CE) due to particle bounce. A new “capture vaporizer” (CV) has been recently developed to achieve unit CE. In this study, we examine the performance of the CV while sampling ambient Aerosols. AMS/ACSMs using the original standard vaporizer (SV) and CV were operated in parallel during three field studies. Concentrations measured with the CV (assuming CE = 1) and SV (using the Composition-dependent CE of Middlebrook et al.), as well as SMPS and PILS-IC are compared. Agreement is good in all cases, verifying that CE ∼ 1 in the CV when sampling ambient particles. Specific findings include: (a) The fragmentation pattern of ambient nitrate and sulfate species observed with the CV was shifted to smaller m/z, suggesting additional thermal deComposition. (b) The differences in fr...

  • size resolved Aerosol Composition and its link to hygroscopicity at a forested site in colorado
    Atmospheric Chemistry and Physics, 2014
    Co-Authors: Ezra J T Levin, Sonia M. Kreidenweis, A J Prenni, Brett B Palm, Douglas A Day, Pedro Campuzanojost, Paul M Winkler, Paul J Demott, Jose L Jimenez
    Abstract:

    Abstract. Aerosol hygroscopicity describes the ability of a particle to take up water and form a cloud droplet. Modeling studies have shown sensitivity of precipitation-producing cloud systems to the availability of Aerosol particles capable of serving as cloud condensation nuclei (CCN), and hygroscopicity is a key parameter controlling the number of available CCN. Continental Aerosol is typically assumed to have a representative hygroscopicity parameter, κ, of 0.3; however, in remote locations this value can be lower due to relatively large mass fractions of organic components. To further our understanding of Aerosol properties in remote areas, we measured size-resolved Aerosol chemical Composition and hygroscopicity in a forested, mountainous site in Colorado during the six-week BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen–Rocky Mountain Biogenic Aerosol Study) campaign. This campaign followed a year-long measurement period at this site, and results from the intensive campaign shed light on the previously reported seasonal cycle in Aerosol hygroscopicity. New particle formation events were observed routinely at this site and nucleation mode Composition measurements indicated that the newly formed particles were predominantly organic. These events likely contribute to the dominance of organic species at smaller sizes, where Aerosol organic mass fractions were between 70 and 90%. Corresponding Aerosol hygroscopicity was observed to be in the range κ = 0.15–0.22, with hygroscopicity increasing with particle size. Aerosol chemical Composition measured by an Aerosol mass spectrometer and calculated from hygroscopicity measurements agreed very well during the intensive study, with an assumed value of κorg = 0.13 resulting in the best agreement.

  • evaluation of Composition dependent collection efficiencies for the aerodyne Aerosol mass spectrometer using field data
    Aerosol Science and Technology, 2012
    Co-Authors: Ann M. Middlebrook, Roya Bahreini, Jose L Jimenez, Manjula R Canagaratna
    Abstract:

    In recent years, Aerodyne Aerosol mass spectrometers (AMS) have been used in many locations around the world to study the size-resolved, nonrefractory chemical Composition of ambient particles. In order to obtain quantitative data, the mass or (number) of particles detected by the AMS relative to the mass (or number) of particles sampled by the AMS, i.e., the AMS collection efficiency (CE) must be known. Previous studies have proposed and used parameterizations of the AMS CE based on the Aerosol Composition and sampling line relative humidity. Here, we evaluate these parameterizations by comparing AMS mass concentrations with independent measurements of fine particle volume or particle-into-liquid sampler (PILS) ion chromatography measurements for 3 field campaigns with different dominant Aerosol mixtures: (1) acidic sulfate particles, (2) Aerosol containing a high mass fraction of ammonium nitrate, and (3) Aerosol composed of primarily biomass burning emissions. The use of the default CE of 0.5 for all c...

  • ccn predictions using simplified assumptions of organic Aerosol Composition and mixing state a synthesis from six different locations
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Jose L Jimenez, Graham Feingold, M J Cubison, Barbara Ervens, Elisabeth Andrews, J A Ogren, Patricia K Quinn, T S Bates
    Abstract:

    Abstract. An accurate but simple quantification of the fraction of Aerosol particles that can act as cloud condensation nuclei (CCN) is needed for implementation in large-scale models. Data on Aerosol size distribution, chemical Composition, and CCN concentration from six different locations have been analyzed to explore the extent to which simple assumptions of Composition and mixing state of the organic fraction can reproduce measured CCN number concentrations. Fresher pollution Aerosol as encountered in Riverside, CA, and the ship channel in Houston, TX, cannot be represented without knowledge of more complex (size-resolved) Composition. For Aerosol that has experienced processing (Mexico City, Holme Moss (UK), Point Reyes (CA), and Chebogue Point (Canada)), CCN can be predicted within a factor of two assuming either externally or internally mixed soluble organics although these simplified Compositions/mixing states might not represent the actual properties of ambient Aerosol populations, in agreement with many previous CCN studies in the literature. Under typical conditions, a factor of two uncertainty in CCN concentration due to Composition assumptions translates to an uncertainty of ~15% in cloud drop concentration, which might be adequate for large-scale models given the much larger uncertainty in cloudiness.

Qi Jiang - One of the best experts on this subject based on the ideXlab platform.

  • The impact of relative humidity on Aerosol Composition and evolution processes during wintertime in
    2020
    Co-Authors: Yele Sun, Zifa Wang, Qi Jiang, Ting Yang
    Abstract:

    h i g h l i g h t s The RH impacts on Aerosol Composition and processes in Beijing were examined. The RH shows the largest impact on sulfate and coal combustion OA during wintertime. Aqueous processing appears not to significantly enhance SOA production and oxidation degree. a r t i c l e i n f o a b s t r a c t Non-refractory submicron Aerosol (NR-PM 1 ) species measured by an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) along with collocated gaseous species are used to investigate the impacts of relative humidity (RH) on Aerosol Composition and evolution processes during wintertime in Beijing, China. Aerosol species exhibit strong, yet different RH dependence between low and high RH levels. At low RH levels (<50%), all Aerosol species increase linearly as a function of RH, among which organics present the largest mass increase rate at 11.4 mg m À3 /10% RH. Because the particle liquid water predicted by E-AIM model is very low and the temperature is relatively constant, the enhancement of Aerosol species is primarily due to the decrease of wind speed. While the rates of increase for most Aerosol species are reduced at high RH levels (>50%), sulfate presents an even faster increasing rate, indicating the significant impact of liquid water on sulfate production. The RH dependence of organic Aerosol (OA) components is also quite different. Among OA components, coal combustion OA (CCOA) presents the largest enhancement in both mass concentration and contribution as a function of RH. Our results elucidate the important roles of liquid water in Aerosol processing at elevated RH levels, in particular affecting sulfate and CCOA via aqueous-phase reaction and gas-particle partitioning associated with water uptake, respectively. It is estimated that aqueous-phase processing can contribute more than 50% of secondary inorganic species production along with an increase of Aerosol particle acidity during the fog periods. However, it appears not to significantly enhance secondary organic Aerosol (SOA) formation and the oxidation degree of OA

  • Aerosol characterization over the north china plain haze life cycle and biomass burning impacts in summer
    Journal of Geophysical Research, 2016
    Co-Authors: Yele Sun, Qi Jiang, Yingjie Zhang, Xingang Liu, Fei Wang, Pucai Wang
    Abstract:

    The North China Plain experiences frequent severe haze pollution during all seasons. Here we present the results from a summer campaign that was conducted at Xianghe, a suburban site located between the megacities of Beijing and Tianjin. Aerosol particle Composition was measured in situ by an Aerosol Chemical Speciation Monitor along with a suite of collocated measurements during 1–30 June 2013. Our results showed that Aerosol Composition at the suburban site was overall similar to that observed in Beijing, which was mainly composed of organics (39%), nitrate (20%), and sulfate (18%). Positive matrix factorization of organic Aerosol (OA) identified four OA factors with different sources and processes. While secondary organic Aerosol dominated OA, on average accounting for 70%, biomass burning OA (BBOA) was also observed to have a considerable contribution (11%) for the entire study period. The contribution of BBOA was increased to 21% during the BB period in late June, indicating a large impact of agricultural burning on air pollution in summer. Biomass burning also exerted a significant impact on Aerosol optical properties. It was estimated that ~60% enhancement of absorption at the ultraviolet spectral region was caused by the organic compounds from biomass burning. The formation mechanisms and sources of severe haze pollution episodes were investigated in a case study. The results highlighted two different mechanisms, i.e., regional transport and local sources, driving the haze life cycles differently in summer in the North China Plain. While secondary Aerosol species dominated Aerosol Composition in the episode from regional transport, organics and black carbon comprised the major fraction in the locally formed haze episode.

  • chemical Composition of Aerosol particles and light extinction apportionment before and during the heating season in beijing china
    Journal of Geophysical Research, 2015
    Co-Authors: Qingqing Wang, Qi Jiang, Yele Sun, Chengzhu Sun, Zifa Wang
    Abstract:

    Despite extensive efforts into characterization of the sources and formation mechanisms of severe haze pollution in the megacity of Beijing, the response of Aerosol Composition and optical properties to coal combustion emissions in the heating season remain poorly understood. Here we conducted a 3 month real-time measurement of submicron Aerosol (PM1) Composition by an Aerosol Chemical Speciation Monitor and particle light extinction by a Cavity Attenuated Phase Shift extinction monitor in Beijing, China, from 1 October to 31 December 2012. The average (±σ) PM1 concentration was 82.4 (±73.1) µg/m3 during the heating period (HP, 15 November to 31 December), which was nearly 50% higher than that before HP (1 October to 14 November). While nitrate and secondary organic Aerosol (SOA) showed relatively small changes, organics, sulfate, and chloride were observed to have significant increases during HP, indicating the dominant impacts of coal combustion sources on these three species. The relative humidity-dependent Composition further illustrated an important role of aqueous-phase processing for the sulfate enhancement during HP. We also observed great increases of hydrocarbon-like OA (HOA) and coal combustion OA (CCOA) during HP, which was attributed to higher emissions at lower temperatures and coal combustion emissions, respectively. The relationship between light extinction and chemical Composition was investigated using a multiple linear regression model. Our results showed that the largest contributors to particle extinction were ammonium nitrate (32%) and ammonium sulfate (28%) before and during HP, respectively. In addition, the contributions of SOA and primary OA to particle light extinction were quantified. The results showed that the OA extinction was mainly caused by SOA before HP and by SOA and CCOA during HP, yet with small contributions from HOA and cooking Aerosol for the entire study period. Our results elucidate substantial changes of Aerosol Composition, formation mechanisms, and optical properties due to coal combustion emissions and meteorological changes in the heating season.

  • the impact of relative humidity on Aerosol Composition and evolution processes during wintertime in beijing china
    Atmospheric Environment, 2013
    Co-Authors: Zifa Wang, Pingqing Fu, Ting Yang, Qi Jiang, J Li, Xinlei Ge
    Abstract:

    Non-refractory submicron Aerosol (NR-PM1) species measured by an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) along with collocated gaseous species are used to investigate the impacts of relative humidity (RH) on Aerosol Composition and evolution processes during wintertime in Beijing, China. Aerosol species exhibit strong, yet different RH dependence between low and high RH levels. At low RH levels ( 50%), sulfate presents an even faster increasing rate, indicating the significant impact of liquid water on sulfate production. The RH dependence of organic Aerosol (OA) components is also quite different. Among OA components, coal combustion OA (CCOA) presents the largest enhancement in both mass concentration and contribution as a function of RH. Our results elucidate the important roles of liquid water in Aerosol processing at elevated RH levels, in particular affecting sulfate and CCOA via aqueous-phase reaction and gas-particle partitioning associated with water uptake, respectively. It is estimated that aqueous-phase processing can contribute more than 50% of secondary inorganic species production along with an increase of Aerosol particle acidity during the fog periods. However, it appears not to significantly enhance secondary organic Aerosol (SOA) formation and the oxidation degree of OA.

  • Aerosol Composition sources and processes during wintertime in beijing china
    Atmospheric Chemistry and Physics, 2013
    Co-Authors: Ziqian Wang, Pingqing Fu, Ting Yang, Qi Jiang, Huabin Dong, J Li
    Abstract:

    Abstract. Air pollution is a major environmental concern during all seasons in the megacity of Beijing, China. Here we present the results from a winter study that was conducted from 21 November 2011 to 20 January 2012 with an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) and various collocated instruments. The non-refractory submicron Aerosol (NR-PM 1 ) species vary dramatically with clean periods and pollution episodes alternating frequently. Compared to summer, wintertime submicron Aerosols show much enhanced organics and chloride, which on average account for 52% and 5%, respectively, of the total NR-PM 1 mass. All NR-PM 1 species show quite different diurnal behaviors between summer and winter. For example, the wintertime nitrate presents a gradual increase during daytime and correlates well with secondary organic Aerosol (OA), indicating a dominant role of photochemical production over gas–particle partitioning. Positive matrix factorization was performed on ACSM OA mass spectra, and identified three primary OA (POA) factors, i.e., hydrocarbon-like OA (HOA), cooking OA (COA), and coal combustion OA (CCOA), and one secondary factor, i.e., oxygenated OA (OOA). The POA dominates OA during wintertime, contributing 69%, with the other 31% being SOA. Further, all POA components show pronounced diurnal cycles with the highest concentrations occurring at nighttime. CCOA is the largest primary source during the heating season, on average accounting for 33% of OA and 17% of NR-PM 1 . CCOA also plays a significant role in chemically resolved particulate matter (PM) pollution as its mass contribution increases linearly as a function of NR-PM 1 mass loadings. The SOA, however, presents a reverse trend, which might indicate the limited SOA formation during high PM pollution episodes in winter. The effects of meteorology on PM pollution and Aerosol processing were also explored. In particular, the sulfate mass is largely enhanced during periods with high humidity because of fog processing of high concentration of precursor SO 2 . In addition, the increased traffic-related HOA emission at low temperature is also highlighted.

Kerri A Pratt - One of the best experts on this subject based on the ideXlab platform.

  • emerging investigator series influence of marine emissions and atmospheric processing on individual particle Composition of summertime arctic Aerosol over the bering strait and chukchi sea
    Environmental Science: Processes & Impacts, 2020
    Co-Authors: Rachel M Kirpes, Blanca Rodriguez, Swarup China, Alexander Laskin, Keyhong Park, Jinyoung Jung, Andrew P Ault, Kerri A Pratt
    Abstract:

    The Arctic is rapidly transforming due to sea ice loss, increasing shipping activity, and oil and gas development. Associated marine and combustion emissions influence atmospheric Aerosol Composition, impacting complex Aerosol–cloud–climate feedbacks. To improve understanding of the sources and processes determining Arctic Aerosol Composition, atmospheric particles were collected aboard the Korean icebreaker R/V Araon cruising within the Bering Strait and Chukchi Sea during August 2016. Offline analyses of individual particles by microspectroscopic techniques, including scanning electron microscopy with energy dispersive X-ray spectroscopy and atomic force microscopy with infrared spectroscopy, provided information on particle size, morphology, and chemical Composition. The most commonly observed particle types were sea spray Aerosol (SSA), comprising ∼60–90%, by number, of supermicron particles, and organic Aerosol (OA), comprising ∼50–90%, by number, of submicron particles. Sulfate and nitrate were internally mixed within both SSA and OA particles, consistent with particle multiphase reactions during atmospheric transport. Within the Bering Strait, SSA and OA particles were more aged, with greater number fractions of particles containing sulfate and/or nitrate, compared to particles collected over the Chukchi Sea. This is indicative of greater pollution influence within the Bering Strait from coastal and inland sources, while the Chukchi Sea is primarily influenced by marine sources.

  • wintertime arctic sea spray Aerosol Composition controlled by sea ice lead microbiology
    ACS central science, 2019
    Co-Authors: Rachel M Kirpes, Nathaniel W May, Andrew P Ault, Daniel Bonanno, Matthew Fraund, Anna J Barget, Ryan C Moffet, Kerri A Pratt
    Abstract:

    The Arctic is experiencing the greatest warming on Earth, as most evident by rapid sea ice loss. Delayed sea ice freeze-up in the Alaskan Arctic is decreasing wintertime sea ice extent and changing marine biological activity. However, the impacts of newly open water on wintertime sea spray Aerosol (SSA) production and atmospheric Composition are unknown. Herein, we identify SSA, produced locally from open sea ice fractures (leads), as the dominant Aerosol source in the coastal Alaskan Arctic during winter, highlighting the year-round nature of Arctic SSA emissions. Nearly all of the individual SSA featured thick organic coatings, consisting of marine saccharides, amino acids, fatty acids, and divalent cations, consistent with exopolymeric secretions produced as cryoprotectants by sea ice algae and bacteria. In contrast, local summertime SSA lacked these organic carbon coatings, or featured thin coatings, with only open water nearby. The individual SSA Composition was not consistent with frost flowers or s...

  • the importance of blowing snow to halogen containing Aerosol in coastal antarctica influence of source region versus wind speed
    Atmospheric Chemistry and Physics, 2018
    Co-Authors: M Giordano, L Kalnajs, Douglas J Goetz, Anita M Avery, Erin F Katz, Nathaniel W May, Anna Leemon, Claire N Mattson, Kerri A Pratt, P. F. Decarlo
    Abstract:

    Abstract. A fundamental understanding of the processes that control Antarctic Aerosols is necessary in determining the Aerosol impacts on climate-relevant processes from Antarctic ice cores to clouds. The first in situ observational online Composition measurements by an Aerosol mass spectrometer (AMS) of Antarctic Aerosols were only recently performed during the Two-Season Ozone Depletion and Interaction with Aerosols Campaign (2ODIAC). 2ODIAC was deployed to sea ice on the Ross Sea near McMurdo Station over two field seasons: austral spring–summer 2014 and winter–spring 2015. The results presented here focus on the overall trends in Aerosol Composition primarily as functions of air masses and local meteorological conditions. The results suggest that the impact of long-range air mass back trajectories on either the absolute or relative concentrations of the Aerosol constituents measured by (and inferred from) an AMS at a coastal location is small relative to the impact of local meteorology. However, when the data are parsed by wind speed, two observations become clear. First, a critical wind speed is required to loft snow from the surface, which, in turn, increases particle counts in all measured size bins. Second, elevated wind speeds showed increased Aerosol chloride and sodium. Further inspection of the AMS data shows that the increased chloride concentrations have more of a “fast-vaporizing” nature than chloride measured at low wind speed. Also presented are the Cl:Na ratios of snow samples and Aerosol filter samples, as measured by ion chromatography, as well as non-chloride Aerosol constituents measured by the AMS. Additionally, submicron Aerosol iodine and bromine concentrations as functions of wind speed are also presented. The results presented here suggest that Aerosol Composition in coastal Antarctica is a strong function of wind speed and that the mechanisms determining Aerosol Composition are likely linked to blowing snow.

  • the importance of blowing snow to antarctic Aerosols number distribution and more than source dependent Composition results from the 2odiac campaign
    Atmospheric Chemistry and Physics, 2018
    Co-Authors: M Giordano, L Kalnajs, Douglas J Goetz, Anita M Avery, Erin F Katz, Nathaniel W May, Anna Leemon, Claire N Mattson, Kerri A Pratt
    Abstract:

    Abstract. A fundamental understanding of the processes that control Antarctic Aerosols is necessary in determining the Aerosol impacts on climate-relevant processes from Antarctic ice cores to clouds. The first in situ observational online Composition measurements by an Aerosol mass spectrometer (AMS) of Antarctic Aerosols were only recently performed during the 2-Season Ozone Depletion and Interaction with Aerosols Campaign (2ODIAC) field campaign. 2ODIAC was deployed to sea ice on the Ross Sea near McMurdo Station over two field seasons: Austral spring-summer 2014 and winter-spring 2015. The results presented here focus on the overall trends in Aerosol Composition primarily as functions of air masses and local meteorological conditions. The results suggest that air mass back trajectories have little impact on either the absolute or relative concentrations of the Aerosol constituents measured by (and inferred from) an AMS at a coastal location. However, when the data is parsed by wind speed, two observations become clear. First, a critical wind speed is required to loft snow from the surface, which, in turn, increases particle counts in all measured size bins. Second, this lofted (blowing) snow significantly increases both Aerosol chloride and sodium. Further inspection of the AMS data shows that the increased chloride concentrations have distinctive signatures that differ from chloride measured at low wind speed. Also presented are the Cl:Na ratios of snow samples, Aerosol filter samples, and non-chloride Aerosol constituents measured by the AMS. Additionally, submicron Aerosol iodine and bromine concentrations as functions of wind speed are also presented. The results presented here suggest that Aerosol Composition in coastal Antarctica is a strong function of wind speed and that the mechanisms determining Aerosol Composition are likely linked to blowing snow.

  • importance of Aerosol Composition mixing state and morphology for heterogeneous ice nucleation a combined field and laboratory approach
    Prof. Cziczo via Chris Sherratt, 2012
    Co-Authors: Kerri A Pratt, K J Baustian, Daniel J Cziczo, Matthew E Wise, Gourihar Kulkarni, Gannet A Hallar
    Abstract:

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

P. F. Decarlo - One of the best experts on this subject based on the ideXlab platform.

  • the importance of blowing snow to halogen containing Aerosol in coastal antarctica influence of source region versus wind speed
    Atmospheric Chemistry and Physics, 2018
    Co-Authors: M Giordano, L Kalnajs, Douglas J Goetz, Anita M Avery, Erin F Katz, Nathaniel W May, Anna Leemon, Claire N Mattson, Kerri A Pratt, P. F. Decarlo
    Abstract:

    Abstract. A fundamental understanding of the processes that control Antarctic Aerosols is necessary in determining the Aerosol impacts on climate-relevant processes from Antarctic ice cores to clouds. The first in situ observational online Composition measurements by an Aerosol mass spectrometer (AMS) of Antarctic Aerosols were only recently performed during the Two-Season Ozone Depletion and Interaction with Aerosols Campaign (2ODIAC). 2ODIAC was deployed to sea ice on the Ross Sea near McMurdo Station over two field seasons: austral spring–summer 2014 and winter–spring 2015. The results presented here focus on the overall trends in Aerosol Composition primarily as functions of air masses and local meteorological conditions. The results suggest that the impact of long-range air mass back trajectories on either the absolute or relative concentrations of the Aerosol constituents measured by (and inferred from) an AMS at a coastal location is small relative to the impact of local meteorology. However, when the data are parsed by wind speed, two observations become clear. First, a critical wind speed is required to loft snow from the surface, which, in turn, increases particle counts in all measured size bins. Second, elevated wind speeds showed increased Aerosol chloride and sodium. Further inspection of the AMS data shows that the increased chloride concentrations have more of a “fast-vaporizing” nature than chloride measured at low wind speed. Also presented are the Cl:Na ratios of snow samples and Aerosol filter samples, as measured by ion chromatography, as well as non-chloride Aerosol constituents measured by the AMS. Additionally, submicron Aerosol iodine and bromine concentrations as functions of wind speed are also presented. The results presented here suggest that Aerosol Composition in coastal Antarctica is a strong function of wind speed and that the mechanisms determining Aerosol Composition are likely linked to blowing snow.

  • wintertime Aerosol chemical Composition and source apportionment of the organic fraction in the metropolitan area of paris
    Atmospheric Chemistry and Physics, 2013
    Co-Authors: Monica Crippa, Jay G Slowik, P. F. Decarlo, M. F. Heringa, R. Chirico, Claudia Mohr, Laurent Poulain
    Abstract:

    The effect of a post-industrial megacity on local and regional air quality was assessed via a month-long field measurement campaign in the Paris metropolitan area during winter 2010. Here we present source apportionment results from three Aerosol mass spectrometers and two aethalometers deployed at three measurement stations within the Paris region. Submicron Aerosol Composition is dominated by the organic fraction (30-36%) and nitrate (28-29%), with lower contributions from sulfate (14-16%), ammonium (12-14%) and black carbon (7-13%). Organic source apportionment was performed using positive matrix factorization, resulting in a set of organic factors corresponding both to primary emission sources and secondary production. The dominant primary sources are traffic (11-15% of organic mass), biomass burning (13-15%) and cooking (up to 35% during meal hours). Secondary organic Aerosol contributes more than 50% to the total organic mass and includes a highly oxidized factor from indeterminate and/or diverse sources and a less oxidized factor related to wood burning emissions. Black carbon was apportioned to traffic and wood burning sources using a model based on wavelength-dependent light absorption of these two combustion sources. The time series of organic and black carbon factors from related sources were strongly correlated. The similarities in Aerosol Composition, total mass and temporal variation between the three sites suggest that particulate pollution in Paris is dominated by regional factors, and that the emissions from Paris itself have a relatively low impact on its surroundings.

  • absorption angstrom exponent in aeronet and related data as an indicator of Aerosol Composition
    Atmospheric Chemistry and Physics, 2010
    Co-Authors: Philip B Russell, Jose L Jimenez, P. F. Decarlo, R W Bergstrom, Y Shinozuka, A D Clarke, John M Livingston, Jens Redemann, Oleg Dubovik
    Abstract:

    Abstract. Recent results from diverse air, ground, and laboratory studies using both radiometric and in situ techniques show that the fractions of black carbon, organic matter, and mineral dust in atmospheric Aerosols determine the wavelength dependence of absorption (often expressed as Absorption Angstrom Exponent, or AAE). Taken together, these results hold promise of improving information on Aerosol Composition from remote measurements. The main purpose of this paper is to show that AAE values for an Aerosol Robotic Network (AERONET) set of retrievals from Sun-sky measurements describing full Aerosol vertical columns are also strongly correlated with Aerosol Composition or type. In particular, we find AAE values near 1 (the theoretical value for black carbon) for AERONET-measured Aerosol columns dominated by urban-industrial Aerosol, larger AAE values for biomass burning Aerosols, and the largest AAE values for Sahara dust Aerosols. These AERONET results are consistent with results from other, very different, techniques, including solar flux-Aerosol optical depth (AOD) analyses and airborne in situ analyses examined in this paper, as well as many other previous results. Ambiguities in Aerosol Composition or mixtures thereof, resulting from intermediate AAE values, can be reduced via cluster analyses that supplement AAE with other variables, for example Extinction Angstrom Exponent (EAE), which is an indicator of particle size. Together with previous results, these results strengthen prospects for determining Aerosol Composition from space, for example using the Glory Aerosol Polarimetry Sensor (APS), which seeks to provide retrievals of multiwavelength single-scattering albedo (SSA) and Aerosol optical depth (and therefore Aerosol absorption optical depth (AAOD) and AAE), as well as shape and other Aerosol properties. Multidimensional cluster analyses promise additional information content, for example by using the Ozone Monitoring Instrument (OMI) to add AAOD in the near ultraviolet and CALIPSO Aerosol layer heights to reduce height-absorption ambiguity.

Rodney J Weber - One of the best experts on this subject based on the ideXlab platform.

  • variability in nocturnal nitrogen oxide processing and its role in regional air quality
    Science, 2006
    Co-Authors: S S Brown, T B Ryerson, A G Wollny, C A Brock, Richard E Peltier, Amy P Sullivan, Rodney J Weber, W P Dube, M Trainer, J F Meagher
    Abstract:

    Nitrogen oxides in the lower troposphere catalyze the photochemical production of ozone (O3) pollution during the day but react to form nitric acid, oxidize hydrocarbons, and remove O3 at night. A key nocturnal reaction is the heterogeneous hydrolysis of dinitrogen pentoxide, N2O5. We report aircraft measurements of NO3 and N2O5, which show that the N2O5 uptake coefficient, g(N2O5), on Aerosol particles is highly variable and depends strongly on Aerosol Composition, particularly sulfate content. The results have implications for the quantification of regional-scale O3 production and suggest a stronger interaction between anthropogenic sulfur and nitrogen oxide emissions than previously recognized.

  • refinements to the particle into liquid sampler pils for ground and airborne measurements of water soluble Aerosol Composition
    Atmospheric Environment, 2003
    Co-Authors: D Orsini, Amy P Sullivan, B Sierau, Karsten Baumann, Rodney J Weber
    Abstract:

    Abstract An improved particle-into-liquid sampler (PILS) has proven successful in both ground-based and aircraft experiments for rapid measurements of soluble Aerosol chemical Composition. Major modifications made to the prototype PILS (Aerosol Sci. Technol. 35 (2001) 718) improve particle collection at higher sample flow (15–17 l min−1) while maintaining minimal sample dilution. Laboratory experiments using a fluorescent calibration Aerosol aided in designing the present system and characterized the PILS collection efficiency as a function of particle size. Collection efficiency for particle diameters Dp between 0.03 and 10 μm is greater than 97%. In addition, the instrument now samples at low pressures (0.3 atmosphere) necessary for airborne measurements up to approximately 8 km in altitude. An ion chromatograph (IC) is coupled to the PILS for direct on-line analysis of the collected sample (hence the name ‘PILS-IC’). Proper selection of columns and eluants allows for 3.5–4 min separation of 9 major inorganic species (Na+, NH4+, K+, Ca2+, Mg2+, Cl−, NO3−, NO2−, SO42−), while acetate, formate, and oxalate, are also possible in 15 min. Any analytical technique capable of continuous online analysis of a liquid sample can be coupled to the PILS for quantitative semi-continuous measurements of Aerosol Composition. Changes made to the prototype are explained and data from a recent experiment are compared with standard integrated filter measurements.

  • refinements to the particle into liquid sampler pils for ground and airborne measurements of water soluble Aerosol Composition
    Atmospheric Environment, 2003
    Co-Authors: D Orsini, Amy P Sullivan, B Sierau, Karsten Baumann, Rodney J Weber
    Abstract:

    An improved particle-into-liquid sampler (PILS) has proven successful in both ground-based and aircraft experiments for rapid measurements of soluble Aerosol chemical Composition. Major modifications made to the prototype PILS (Aerosol Sci. Technol. 35 (2001) 718) improve particle collection at higher sample flow (15–17 l min � 1 ) while maintaining minimal sample dilution. Laboratory experiments using a fluorescent calibration Aerosol aided in designing the present system and characterized the PILS collection efficiency as a function of particle size. Collection efficiency for particle diameters Dp between 0.03 and 10mm is greater than 97%. In addition, the instrument now samples at low pressures (0.3 atmosphere) necessary for airborne measurements up to approximately 8 km in altitude. An ion chromatograph (IC) is coupled to the PILS for direct on-line analysis of the collected sample (hence the name ‘PILS-IC’). Proper selection of columns and eluants allows for 3.5–4 min separation of 9 major inorganic species (Na + , NH4 ,K + ,C a 2+ ,M g 2+ ,C l � ,N O 3 ,N O 2 ,S O 4� ), while acetate, formate, and oxalate, are also possible in 15 min. Any analytical technique capable of continuous online analysis of a liquid sample can be coupled to the PILS for quantitative semi-continuous measurements of Aerosol Composition. Changes made to the prototype are explained and data from a recent experiment are compared with standard integrated filter measurements. r 2003 Elsevier Science Ltd. All rights reserved.

  • measurements of the h2so4 mass accommodation coefficient onto polydisperse Aerosol
    Journal of Geophysical Research, 1997
    Co-Authors: A Jefferson, Rodney J Weber, F L Eisele, P Ziemann, James Marti, Peter H Mcmurry
    Abstract:

    The loss rate of H2SO4 vapor onto submicron particles was measured for three different particle substrates. The experimental technique involved direct flow tube measurements of H2SO4 decay rates onto a polydisperse Aerosol using chemical ionization mass spectroscopic detection. The Aerosols of this study were partially hydrated crystalline salts with diameters in the size range of 20 to 400 nm. The mass accommodation coefficients, α, were calculated from the first-order rate constants for H2SO4 loss to be 0.73±0.21 and 0.79±0.23 for loss onto (NH4)SO4 and NaCl, respectively. Measurements of the loss rate of H2SO4 onto a NaCl Aerosol coated with stearic acid resulted in lower mass accommodation coefficients with values of 0.31 and 0.19 for Aerosol with high and low stearic acid coverage, respectively. The observed decrease in α on an Aerosol with a hydrocarbon coating suggests that Aerosol Composition is a key factor in H2SO4 adsorption on to a particle surface.