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21.
A single-beam photothermal interferometer for in situ measurements of aerosol light absorption
Bradley Visser, Jannis Röhrbein, Peter Steigmeier, Luka Drinovec, Griša Močnik, Ernest Weingartner, 2020, izvirni znanstveni članek

Opis: We have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.
Najdeno v: ključnih besedah
Ključne besede: aerosol, aerosol absorption, black carbon, photo-thermal interferometer, climate change
Objavljeno: 29.12.2020; Ogledov: 596; Prenosov: 16
.pdf Polno besedilo (2,44 MB)

22.
Enrichment of Organic Nitrogen in Primary Biological Particles during advection over the North Atlantic
Manuel Dall’Osto, Tina Šantl Temkiv, Colin O’Dowd, Roy M. Harrison, 2019, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...Organic nitrogen, Biological particles, ATOFMF, Single particle, Aerosol aging...
Ključne besede: Organic nitrogen, Biological particles, ATOFMF, Single particle, Aerosol aging
Objavljeno: 04.01.2021; Ogledov: 389; Prenosov: 0
.pdf Polno besedilo (1,10 MB)

23.
Aircraft vertical profiles during summertime regional and Saharan dust scenarios over the north-western Mediterranean basin: aerosol optical and physical properties
Jesus Yus-Diez, Marina Ealo, Marco Pandolfi, Noemi Perez, Gloria Titos, Griša Močnik, Xavier Querol, A. Alastuey, 2021, izvirni znanstveni članek

Opis: Accurate measurements of the horizontal and vertical distribution of atmospheric aerosol particle optical properties are key for a better understanding of their impact on the climate. Here we present the results of a measurement campaign based on instrumented flights over north-eastern Spain. We measured vertical profiles of size-segregated atmospheric particulate matter (PM) mass concentrations and multi-wavelength scattering and absorption coefficients in the western Mediterranean basin (WMB). The campaign took place during typical summer conditions, characterized by the development of a vertical multi-layer structure, under both summer regional pollution episodes (REGs) and Saharan dust events (SDEs). REG patterns in the region form under high insolation and scarce precipitation in summer, favouring layering of highly aged fine-PM strata in the lower few kma.s.l. The REG scenario prevailed during the entire measurement campaign. Additionally, African dust outbreaks and plumes from northern African wildfires influenced the study area. The vertical profiles of climate-relevant intensive optical parameters such as single-scattering albedo (SSA); the asymmetry parameter (g); scattering, absorption and SSA Ångström exponents (SAE, AAE and SSAAE); and PM mass scattering and absorption cross sections (MSC and MAC) were derived from the measurements. Moreover, we compared the aircraft measurements with those performed at two GAW–ACTRIS (Global Atmosphere Watch–Aerosol, Clouds and Trace Gases) surface measurement stations located in north-eastern Spain, namely Montseny (MSY; regional background) and Montsec d'Ares (MSA; remote site). Airborne in situ measurements and ceilometer ground-based remote measurements identified aerosol air masses at altitudes up to more than 3.5 kma.s.l. The vertical profiles of the optical properties markedly changed according to the prevailing atmospheric scenarios. During SDE the SAE was low along the profiles, reaching values < 1.0 in the dust layers. Correspondingly, SSAAE was negative, and AAE reached values up to 2.0–2.5, as a consequence of the UV absorption increased by the presence of the coarse dust particles. During REG, the SAE increased to > 2.0, and the asymmetry parameter g was rather low (0.5–0.6) due to the prevalence of fine PM, which was characterized by an AAE close to 1.0, suggesting a fossil fuel combustion origin. During REG, some of the layers featured larger AAE (> 1.5), relatively low SSA at 525 nm (< 0.85) and high MSC (> 9 m2 g−1) and were associated with the influence of PM from wildfires. Overall, the SSA and MSC near the ground ranged around 0.85 and 3 m2 g−1, respectively, and increased at higher altitudes, reaching values above 0.95 and up to 9 m2 g−1. The PM, MSC and MAC were on average larger during REG compared to SDE due to the larger scattering and absorption efficiency of fine PM compared with dust. The SSA and MSC had quite similar vertical profiles and often both increased with height indicating the progressive shift toward PM with a larger scattering efficiency with altitude. This study contributes to our understanding of regional-aerosol vertical distribution and optical properties in the WMB, and the results will be useful for improving future climate projections and remote sensing or satellite retrieval algorithms.
Najdeno v: ključnih besedah
Ključne besede: aerosol, climate change, Saharan dust, black carbon, aerosol absorption, aerosol scattering
Objavljeno: 14.01.2021; Ogledov: 453; Prenosov: 0
.pdf Polno besedilo (10,82 MB)

24.
Elucidating local pollution and site representativeness at the Jungfraujoch, Switzerland through parallel aerosol measurements at an adjacent mountain ridge
Martin Gysel, Maxime Hervo, Urs Baltensperger, Markus Christian Leuenberger, Martine Collaud Coen, Stéphane Affolter, Günther Wehrle, Griša Močnik, Benjamin Brem, Nicolas Bukowiecki, 2021, izvirni znanstveni članek

Opis: Many long-term air pollution and climate monitoring stations face the issue of increasing anthropogenic activities in their vicinity. Furthermore, the spatial representativeness of the sites is often not entirely understood especially in mountainous terrain with complex topographic features. This study presents a 5-year comparison of parallel aerosol measurements (total particle number concentration and equivalent black carbon mass concentration) at the Jungfraujoch in the Swiss Alps (JFJ, 3580 m a.s.l.), and an adjacent mountain ridge, the Jungfrau East Ridge (JER, 3705 m a.s.l.), in 1000 m air-line distance to the main site. The parallel aerosol measurements reveal characteristic differences in the diurnal variations between the two sites under certain specific meteorological conditions. Our analysis estimates that on 20-40% of the days local activities at the Jungfraujoch have a clear influence on the measured time series of the total aerosol number concentration and the equivalent black carbon mass concentration. This influence is mainly seen in form of strong isolated spikes rather than by an increase in the on-site background concentration. They can thus be flagged during the data quality assurance process and filtered from those measurement parameters available at high time resolution. Removing the spikes from the original time series results in daily mean values for the total aerosol number concentration and equivalent black carbon mass concentration that are 5-10 % lower compared to the original signals. During nighttime with hardly any local pollution sources that cause spikes this percentage decreases towards 0%. The signal baselines at the Jungfraujoch and Jungfrau East Ridge correlate well during more than 50% of the days.
Najdeno v: ključnih besedah
Ključne besede: aerosol long-term monitoring, equivalent black carbon, aerosol number concentration, spatial variation
Objavljeno: 15.03.2021; Ogledov: 290; Prenosov: 10
URL Polno besedilo (0,00 KB)
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25.
Morphology and mixing state of aged soot particles at a remote marine free troposphere site
Sumit Kumar, Katja Džepina, Michael P. Dziobak, Paulo Fialho, Judith A. Perlinger, Swarup China, Barbara Scarnato, Robert C. Owen, Bo Zhang, MarianT. Ampadu, 2015, izvirni znanstveni članek

Opis: The radiative properties of soot particles depend on their morphology and mixing state, but their evolution during transport is still elusive. Here we report observations from an electron microscopy analysis of individual particles transported in the free troposphere over long distances to the remote Pico Mountain Observatory in the Azores in the North Atlantic. Approximately 70% of the soot particles were highly compact and of those 26% were thinly coated. Discrete dipole approximation simulations indicate that this compaction results in an increase in soot single scattering albedo by a factor of <= 2.17. The top of the atmosphere direct radiative forcing is typically smaller for highly compact than mass-equivalent lacy soot. The forcing estimated using Mie theory is within 12% of the forcing estimated using the discrete dipole approximation for a high surface albedo, implying that Mie calculations may provide a reasonable approximation for compact soot above remote marine clouds.
Najdeno v: ključnih besedah
Povzetek najdenega: ...atmospheric aerosol, soot, long-range transport, free troposphere, single scattering...
Ključne besede: atmospheric aerosol, soot, long-range transport, free troposphere, single scattering albedo
Objavljeno: 11.04.2021; Ogledov: 221; Prenosov: 0
.pdf Polno besedilo (899,35 KB)

26.
Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory
J. Hueber, Sumit Kumar, J. A. Perlinger, Katja Džepina, Claudio Mazzoleni, Paulo Fialho, Swarup China, Bo Zhang, R. Chris Owen, D. Helmig, 2015, izvirni znanstveni članek

Opis: Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m above mean sea level on Pico Island of the Azores archipelago in the North Atlantic. The observatory is located ∼ 3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon, and inorganic ions. The average ambient concentration of aerosol was 0.9 ± 0.7 µg m−3 . On average, organic aerosol components represent the largest mass fraction of the total measured aerosol (60 ± 51 %), followed by sulfate (23 ± 28 %), nitrate (13 ± 10 %), chloride (2 ± 3 %), and elemental carbon (2 ± 2 %). Water-soluble organic matter (WSOM) extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. 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 had unsaturated structures with CHO and CHNO elemental compositions. FLEXPART retroplume analyses showed the sampled air masses were very aged (average plume age > 12 days). These aged aerosol WSOM compounds had an average O /C ratio of ∼ 0.45, which is relatively low compared to O /C ratios of other aged aerosol. 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 the WSOM 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 phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses of 9/25 were more aged and influenced by marine emissions, as indicated by the presence of organosulfates and other species characteristic of marine aerosol. The change in the air masses for the two samples was corroborated by the changes in ethane, propane, and ozone, morphology of particles, as well as by the FLEXPART retroplume simulations. This paper presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location and provides evidence of low oxygenation after long-range transport. We hypothesize this is a result of the selective removal of highly aged and polar species during long-range transport, because the aerosol underwent a combination of atmospheric processes during transport facilitating aqueous-phase removal (e.g., clouds processing) and fragmentation (e.g., photolysis) of components.
Najdeno v: ključnih besedah
Ključne besede: organic aerosol, ultrahigh-resolution FT-ICR MS, electron microscopy, remote marine atmosphere, Pico Mountain Observatory
Objavljeno: 11.04.2021; Ogledov: 171; Prenosov: 0
.pdf Polno besedilo (4,36 MB)

27.
Secondary organic aerosol formation from semi- and intermediate-volatility organic compounds and glyoxal
Jose L. Jimenez, Sasha Madronich, Rainer Volkamer, Eleanor M. Waxman, Katja Džepina, Barbara Ervens, Julia Lee-Taylor, Bernard Aumont, 2013, izvirni znanstveni članek

Opis: The role of aqueous multiphase chemistry in the formation of secondary organic aerosol (SOA) remains difficult to quantify. We investigate it here by testing the rapid formation of moderate oxygen-to-carbon (O/C) SOA during a case study in Mexico City. A novel laboratory-based glyoxal-SOA mechanism is applied to the field data, and explains why less gas-phase glyoxal mass is observed than predicted. Furthermore, we compare an explicit gas-phase chemical mechanism for SOA formation from semi- and intermediate-volatility organic compounds (S/IVOCs) with empirical parameterizations of S/IVOC aging. The mechanism representing our current understanding of chemical kinetics of S/IVOC oxidation combined with traditional SOA sources and mixing of background SOA underestimates the observed O/C by a factor of two at noon. Inclusion of glyoxal-SOA with O/C of 1.5 brings O/C predictions within measurement uncertainty, suggesting that field observations can be reconciled on reasonable time scales using laboratory-based empirical relationships for aqueous chemistry.
Najdeno v: ključnih besedah
Ključne besede: secondary organic aerosol, glyoxal, aqueous multiphase chemistry, oxygen-to-carbon ratio, single scattering albedo
Objavljeno: 11.04.2021; Ogledov: 186; Prenosov: 0
.pdf Polno besedilo (724,40 KB)

28.
Evolution of organic aerosols in the atmosphere
J. H. Kroll, P. F. DeCarlo, J. David Allan, H. Coe, Katja Džepina, Jose L. Jimenez, M. R. Canagaratna, N. M. Donahue, A. S. H. Prevot, Q. Zhang, 2009, izvirni znanstveni članek

Opis: Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high–time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Organic aerosol (OA) particles affect climate forcing and human...
Ključne besede: secondary organic aerosol, source apportionment, aerodyne aerosol mass spectrometer, global field measurements, laboratory experiments
Objavljeno: 11.04.2021; Ogledov: 184; Prenosov: 0
.pdf Polno besedilo (721,30 KB)

29.
Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically-influenced Northern Hemisphere midlatitudes
Q. Zhang, Jose L. Jimenez, M. R. Canagaratna, J. David Allan, H. Coe, I. M. Ulbrich, M. R. Alfarra, A. Takami, A. M. Middlebrook, Katja Džepina, 2007, izvirni znanstveni članek

Opis: Organic aerosol (OA) data acquired by the Aerosol Mass Spectrometer (AMS) in 37 field campaigns were deconvolved into hydrocarbon-like OA (HOA) and several types of oxygenated OA (OOA) components. HOA has been linked to primary combustion emissions (mainly from fossil fuel) and other primary sources such as meat cooking. OOA is ubiquitous in various atmospheric environments, on average accounting for 64%, 83% and 95% of the total OA in urban, urban downwind, and rural/remote sites, respectively. A case study analysis of a rural site shows that the OOA concentration is much greater than the advected HOA, indicating that HOA oxidation is not an important source of OOA, and that OOA increases are mainly due to SOA. Most global models lack an explicit representation of SOA which may lead to significant biases in the magnitude, spatial and temporal distributions of OA, and in aerosol hygroscopic properties.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Organic aerosol (OA) data acquired by the Aerosol Mass...
Ključne besede: atmospheric aerosol, secondary organic aerosols, primary organic aerosols, aerodyne aerosol mass spectrometer
Objavljeno: 11.04.2021; Ogledov: 225; Prenosov: 0
.pdf Polno besedilo (1,15 MB)

30.
Technical note
Dara Salcedo, T. B. Onasch, M. R. Canagaratna, Katja Džepina, J. A. Huffman, J. Jayne, D. Worsnop, C. E. Kolb, S. Weimer, F. Drewnick, 2007, izvirni znanstveni članek

Opis: Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico City, during the Mexico City Metropolitan Area field study (MCMA-2003) from 29 March - 4 May 2003 to investigate particle concentrations, sources, and processes. We report the use of a particle beam width probe (BWP) in the field to quantify potential losses of particles due to beam broadening inside the AMS caused by particle shape (nonsphericity) and particle size. Data from this probe show that no significant mass of particles was lost due to excessive beam broadening; i.e. the shape- and size-related collection efficiency (E-s) of the AMS during this campaign was approximately one. Comparison of the BWP data from MCMA-2003 with other campaigns shows that the same conclusion holds for several other urban, rural and remotes sites. This means that the aerodynamic lens in the AMS is capable of efficiently focusing ambient particles into a well defined beam and onto the AMS vaporizer for particles sampled in a wide variety of environments. All the species measured by the AMS during MCMA-2003 have similar attenuation profiles which suggests that the particles that dominate the mass concentration were internally mixed most of the time. Only for the smaller particles ( especially below 300 nm), organic and inorganic species show different attenuation versus particle size which is likely due to partial external mixing of these components. Changes observed in the focusing of the particle beam in time can be attributed, in part, to changes in particle shape (i.e. due to relative humidity) and size of the particles sampled. However, the relationships between composition, atmospheric conditions, and particle shape and size appear to be very complex and are not yet completely understood.
Najdeno v: ključnih besedah
Povzetek najdenega: ...Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico...
Ključne besede: atmospheric aerosol, organic aerosols, aerodynamic lenses, Mexico City
Objavljeno: 11.04.2021; Ogledov: 189; Prenosov: 0
.pdf Polno besedilo (341,65 KB)

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