IRF Auflistung nach Autor:in "Weingartner, Ernest"

Auflistung nach Autor:in "Weingartner, Ernest"

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13-month climatology of the aerosol hygroscopicity at the free tropospheric site Jungfraujoch (3580 m a.s.l.)
(Copernicus, 16.11.2010) Kammermann, Lukas; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
A hygroscopicity tandem differential mobility analyzer (HTDMA) was operated at the high-alpine site Jungfraujoch in order to characterize the hygroscopic diameter growth factors of the free tropospheric Aitken and accumulation mode aerosol. More than ~5000 h of valid data were collected for the dry diameters D0 = 35, 50, 75, 110, 165, and 265 nm during the 13-month measurement period from 1 May 2008 through 31 May 2009. No distinct seasonal variability of the hygroscopic properties was observed. Annual mean hygroscopic diameter growth factors (D/D0) at 90% relative humidity were found to be 1.34, 1.43, and 1.46 for D0 = 50, 110, and 265 nm, respectively. This size dependence can largely be attributed to the Kelvin effect because corresponding values of the hygroscopicity parameter κ are nearly independent of size. The mean hygroscopicity of the Aitken and accumulation mode aerosol at the free tropospheric site Jungfraujoch was found to be κ≈0.24 with little variability throughout the year. The impact of Saharan dust events, a frequent phenomenon at the Jungfraujoch, on aerosol hygroscopicity was shown to be negligible for D0<265 nm. Thermally driven injections of planetary boundary layer (PBL) air, particularly observed in the early afternoon of summer days with convective anticyclonic weather conditions, lead to a decrease of aerosol hygroscopicity. However, the effect of PBL influence is not seen in the annual mean hygroscopicity data because the effect is small and those conditions (weather class, season and time of day) with PBL influence are relatively rare. Aerosol hygroscopicity was found to be virtually independent of synoptic wind direction during advective weather situations, i.e. when horizontal motion of the atmosphere dominates over thermally driven convection. This indicates that the hygroscopic behavior of the aerosol observed at the Jungfraujoch can be considered representative of the lower free troposphere on at least a regional if not continental scale.
01A - Beitrag in wissenschaftlicher Zeitschrift
A 17 month climatology of the cloud condensation nuclei number concentration at the high alpine site Jungfraujoch
(Wiley, 24.05.2011) Jurányi, Zsófia; Gysel, Martin; Weingartner, Ernest; Bukowiecki, Nicolas; Kammermann, Lorenz; Baltensperger, Urs [in: Journal of Geophysical Research: Atmospheres]
Between May 2008 and September 2009 the cloud condensation nuclei (CCN) number concentration, NCCN, was measured at the high alpine site Jungfraujoch, which is located in the free troposphere most of the time. Measurements at 10 different supersaturations (0.12%–1.18%) were made using a CCN counter (CCNC). The monthly median NCCN values show a distinct seasonal variability with ∼5–12 times higher values in summer than in winter. The major part of this variation can be explained by the seasonal amplitude of total aerosol number concentration (∼4.5 times higher values in summer), but it is further amplified (factor of ∼1.1–2.6) by a shift of the particle number size distribution toward slightly larger sizes in summer. In contrast to the extensive properties, the monthly median of the critical dry diameter, above which the aerosols activate as CCN, does not show a seasonal cycle (relative standard deviations of the monthly median critical dry diameters at the different supersaturations are 4–9%) or substantial variability (relative standard deviations of individual data points at the different supersaturations are less than 18–37%). The mean CCN-derived hygroscopicity of the aerosol corresponds to a value of the hygroscopicity parameter κ of 0.20 (assuming a surface tension of pure water) with moderate supersaturation dependence. NCCN can be reliably predicted throughout the measurement period with knowledge of the above-mentioned averaged κ value and highly time-resolved (∼5 min) particle number size distribution data. The predicted NCCN was within 0.74 to 1.29 times the measured value during 80% of the time (94,499 data points in total at 10 different supersaturations).
01A - Beitrag in wissenschaftlicher Zeitschrift
A combined particle trap/HTDMA hygroscopicity study of mixed inorganic/organic aerosol particles
(Copernicus, 19.09.2008) Zardini, Alessandro A.; Sjogren, S.; Marcolli, Claudia; Krieger, Ulrich K.; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Peter, Thomas [in: Atmospheric Chemistry and Physics]
Atmospheric aerosols are often mixtures of inorganic and organic material. Organics can represent a large fraction of the total aerosol mass and are comprised of water-soluble and insoluble compounds. Increasing attention was paid in the last decade to the capability of mixed inorganic/organic aerosol particles to take up water (hygroscopicity). We performed hygroscopicity measurements of internally mixed particles containing ammonium sulfate and carboxylic acids (citric, glutaric, adipic acid) in parallel with an electrodynamic balance (EDB) and a hygroscopicity tandem differential mobility analyzer (HTDMA). The organic compounds were chosen to represent three distinct physical states. During hygroscopicity cycles covering hydration and dehydration measured by the EDB and the HTDMA, pure citric acid remained always liquid, adipic acid remained always solid, while glutaric acid could be either. We show that the hygroscopicity of mixtures of the above compounds is well described by the Zdanovskii-Stokes-Robinson (ZSR) relationship as long as the two-component particle is completely liquid in the ammonium sulfate/glutaric acid system; deviations up to 10% in mass growth factor (corresponding to deviations up to 3.5% in size growth factor) are observed for the ammonium sulfate/citric acid 1:1 mixture at 80% RH. We observe even more significant discrepancies compared to what is expected from bulk thermodynamics when a solid component is present. We explain this in terms of a complex morphology resulting from the crystallization process leading to veins, pores, and grain boundaries which allow for water sorption in excess of bulk thermodynamic predictions caused by the inverse Kelvin effect on concave surfaces.
01A - Beitrag in wissenschaftlicher Zeitschrift
A compact and portable deposition chamber to study nanoparticles in air-exposed tissue
(Mary Ann Liebert, 2013) Mertes, Peter; Praplan, Arnaud P.; Künzi, Lisa; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; Weingartner, Ernest; Ricka, Jaroslav; Fierz, Martin; Kalberer, Markus [in: Journal of Aerosol Medicine and Pulmonary Drug Delivery]
01A - Beitrag in wissenschaftlicher Zeitschrift
A dual-wavelength photothermal aerosol absorption monitor. Design, calibration and performance
(Copernicus, 2022) Drinovec, Luka; Jagodič, Uroš; Pirker, Luka; Škarabot, Miha; Kurtjak, Mario; Vidović, Kristijan; Ferrero, Luca; Visser, Bradley; Röhrbein, Jannis; Weingartner, Ernest; Kalbermatter, Daniel M.; Vasilatou, Konstantina; Bühlmann, Tobias; Pascale, Celine; Müller, Thomas; Wiedensohler, Alfred; Močnik, Griša [in: Atmospheric Measurement Techniques]
There exists a lack of aerosol absorption measurement techniques with low uncertainties and without artefacts. We have developed the two-wavelength Photothermal Aerosol Absorption Monitor (PTAAM-2λ), which measures the aerosol absorption coefficient at 532 and 1064 nm. Here we describe its design, calibration and mode of operation and evaluate its applicability, limits and uncertainties. The 532 nm channel was calibrated with ∼ 1 µmol mol−1 NO2, whereas the 1064 nm channel was calibrated using measured size distribution spectra of nigrosin particles and a Mie calculation. Since the aerosolized nigrosin used for calibration was dry, we determined the imaginary part of the refractive index of nigrosin from the absorbance measurements on solid thin film samples. The obtained refractive index differed considerably from the one determined using aqueous nigrosin solution. PTAAM-2λ has no scattering artefact and features very low uncertainties: 4 % and 6 % for the absorption coefficient at 532 and 1064 nm, respectively, and 9 % for the absorption Ångström exponent. The artefact-free nature of the measurement method allowed us to investigate the artefacts of filter photometers. Both the Aethalometer AE33 and CLAP suffer from cross sensitivity to scattering – this scattering artefact is most pronounced for particles smaller than 70 nm. We observed a strong dependence of the filter multiple scattering parameter on the particle size in the 100–500 nm range. The results from the winter ambient campaign in Ljubljana showed similar multiple scattering parameter values for ambient aerosols and laboratory experiments. The spectral dependence of this parameter resulted in AE33 reporting the absorption Ångström exponent for different soot samples with values biased 0.23–0.35 higher than the PTAAM-2λ measurement. Photothermal interferometry is a promising method for reference aerosol absorption measurements.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology - 1. physical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe
(Elsevier, 05/2004) Van Dingenen, Rita; Raes, Frank; Putaud, Jean-Philippe; Baltensperger, Urs; Charron, Aurélie; Facchini, Maria Cristina; Decesari, Stefano; Fuzzi, Sandro; Gehrig, Robert; Hansson, Hans-Christen; Harrison, Roy M.; Hüglin, Cristoph; Jones, Alan M.; Laj, Paolo; Lorbeer, Gundi; Maenhaut, Willy; Palmgren, Finn; Querol, Xavier; Rodriguez, Sergio; Schneider, Jürgen; ten Brink, Harry; Tunved, Peter; Tørseth, Kjetil; Wehner, Birgit; Weingartner, Ernest; Wiedensohler, Alfred; Wåhlin, Peter [in: Atmospheric Environment]
This paper synthesizes data on aerosol (particulate matter, PM) physical characteristics, which were obtained in European aerosol research activities at free-troposphere, natural, rural, near-city, urban, and kerbside sites over the past decade. It covers only two sites in the semi-arid Mediterranean area, and lacks data from Eastern Europe. The data include PM10 and/or PM2.5 mass concentrations, and aerosol particle size distributions. Such data sets are more comprehensive than those currently provided by air quality monitoring networks (e.g. EMEP, EUROAIRNET). Data available from 31 sites in Europe (called “The Network”) were reviewed. They were processed and plotted to allow comparisons in spite of differences in the sampling and analytical techniques used in various studies. A number of conclusions are drawn as follows: Background annual average PM10 and PM2.5 mass concentrations for continental Europe are 7.0±4.1 and 4.8±2.4 μg mˉ³, respectively. The EU 2005 annual average PM10 standard of 40 μg mˉ³ is exceeded at a few sites in The Network. At all near city, urban and kerbside sites, the EU 2010 annual average PM10 standard of 20 μg mˉ³, as well as the US-EPA annual average PM2.5 standard of 15 μg mˉ³ are exceeded. In certain regions, PM10 and PM2.5 in cities are strongly affected by the regional aerosol background. There is no “universal” (i.e. valid for all sites) ratio between PM2.5 and PM10 mass concentrations, although fairly constant ratios do exist at individual sites. There is no universal correlation between PM mass concentration on the one hand, and total particle number concentration on the other hand, although a ‘baseline’ ratio between number and mass is found for sites not affected by local emissions. This paper is the first part of two companion papers of which the second part describes chemical characteristics.
01A - Beitrag in wissenschaftlicher Zeitschrift
A European aerosol phenomenology-5. Climatology of black carbon optical properties at 9 regional background sites across Europe
(Elsevier, 2016) Zanatta, Marco; Gysel, Martin; Bukowiecki, Nicolas; Müller, Thomas; Weingartner, Ernest; Areskoug, Hans; Fiebig, Markus; Yttri, Karl Espen; Mihalopoulos, Nikolaos; Kouvarakis, Giorgos; Beddows, David; Harrison, Roy; Cavalli, Fabrizia; Putaud, Jean; Spindler, Gerald; Wiedensohler, Alfred; Alastuey, Andrés; Pandolfi, Marco; Sellegri, Karine; Swietlicki, Erik; Jaffrezo, Jean-Luc; Baltensperger, Urs; Laj, Paolo [in: Atmospheric Environment]
01A - Beitrag in wissenschaftlicher Zeitschrift
A global study of hygroscopicity-driven light-scattering enhancement in the context of other in situ aerosol optical properties
(Copernicus, 2021) Titos, Gloria; Burgos, María A.; Zieger, Paul; Alados-Arboledas, Lucas; Baltensperger, Urs; Jefferson, Anne; Sherman, James; Weingartner, Ernest; Henzing, Bas; Luoma, Krista; O'Dowd, Colin; Wiedensohler, Alfred; Andrews, Elisabeth [in: Atmospheric Chemistry and Physics]
The scattering and backscattering enhancement factors (f(RH) and fb(RH)) describe how aerosol particle light scattering and backscattering, respectively, change with relative humidity (RH). They are important parameters in estimating direct aerosol radiative forcing (DARF). In this study we use the dataset presented in Burgos et al. (2019) that compiles f(RH) and fb(RH) measurements at three wavelengths (i.e., 450, 550 and 700 nm) performed with tandem nephelometer systems at multiple sites around the world. We present an overview of f(RH) and fb(RH) based on both long-term and campaign observations from 23 sites representing a range of aerosol types. The scattering enhancement shows a strong variability from site to site, with no clear pattern with respect to the total scattering coefficient. In general, higher f(RH) is observed at Arctic and marine sites, while lower values are found at urban and desert sites, although a consistent pattern as a function of site type is not observed. The backscattering enhancement fb(RH) is consistently lower than f(RH) at all sites, with the difference between f(RH) and fb(RH) increasing for aerosol with higher f(RH). This is consistent with Mie theory, which predicts higher enhancement of the light scattering in the forward than in the backward direction as the particle takes up water. Our results show that the scattering enhancement is higher for PM1 than PM10 at most sites, which is also supported by theory due to the change in scattering efficiency with the size parameter that relates particle size and the wavelength of incident light. At marine-influenced sites this difference is enhanced when coarse particles (likely sea salt) predominate. For most sites, f(RH) is observed to increase with increasing wavelength, except at sites with a known dust influence where the spectral dependence of f(RH) is found to be low or even exhibit the opposite pattern. The impact of RH on aerosol properties used to calculate radiative forcing (e.g., single-scattering albedo, ω0, and backscattered fraction, b) is evaluated. The single-scattering albedo generally increases with RH, while b decreases. The net effect of aerosol hygroscopicity on radiative forcing efficiency (RFE) is an increase in the absolute forcing effect (negative sign) by a factor of up to 4 at RH = 90 % compared to dry conditions (RH < 40 %). Because of the scarcity of scattering enhancement measurements, an attempt was made to use other more commonly available aerosol parameters (i.e., ω0 and scattering Ångström exponent, αsp) to parameterize f(RH). The majority of sites (75 %) showed a consistent trend with ω0 (higher f(RH = 85 %) for higher ω0), while no clear pattern was observed between f(RH = 85 %) and αsp. This suggests that aerosol ω0 is more promising than αsp as a surrogate for the scattering enhancement factor, although neither parameter is ideal. Nonetheless, the qualitative relationship observed between ω0 and f(RH) could serve as a constraint on global model simulations.
01A - Beitrag in wissenschaftlicher Zeitschrift
A mobile pollutant measurement laboratory - measuring gas phase and aerosol ambient concentrations with high spatial and temporal resolution
(Elsevier, 12/2002) Bukowiecki, Nicolas; Dommen, Josef; Prévôt, André S.H.; Richter, Rene; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Environment]
A mobile pollutant measurement laboratory was designed and built at the Paul Scherrer Institute (Switzerland) for the measurement of on-road ambient concentrations of a large set of trace gases and aerosol parameters with high time resolution (<15 s for most instruments), along with geographical and meteorological information. This approach allowed for pollutant level measurements both near traffic (e.g. in urban areas or on freeways/main roads) and at rural locations far away from traffic, within short periods of time and at different times of day and year. Such measurements were performed on a regular base during the project year of gas phase and aerosol measurements (YOGAM). This paper presents data measured in the Zürich (Switzerland) area on a late autumn day (6 November) in 2001. The local urban particle background easily reached 50 000 cmˉ³, with additional peak particle number concentrations of up to 400 000 cmˉ³. The regional background of the total particle number concentration was not found to significantly correlate with the distance to traffic and anthropogenic emissions of carbon monoxide and nitrogen oxides. On the other hand, this correlation was significant for the number concentration of particles in the size range 50–150 nm, indicating that the particle number concentration in this size range is a better traffic indicator than the total number concentration. Particle number size distribution measurements showed that daytime urban ambient air is dominated by high number concentrations of ultrafine particles (nanoparticles) with diameters < 50 nm, which are immediately formed by traffic exhaust and thus belong to the primary emissions. However, significant variation of the nanoparticle mode was also observed in number size distributions measured in rural areas both at daytime and nighttime, suggesting that nanoparticles are not exclusively formed by primary traffic emissions. While urban daytime total number concentrations were increased by a factor of 10 compared to the nighttime background, corresponding factors for total surface area and total volume concentrations were 2 and 1.5, respectively.
01A - Beitrag in wissenschaftlicher Zeitschrift
A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra
(Copernicus, 2012) Heringa, Maarten F.; DeCarlo, Peter F.; Chirico, Roberto; Tritscher, Torsten; Clairotte, Michael; Mohr, Christine; Crippa, Monica; Slowik, Jay Gates; Pfaffenberger, Lisa; Dommen, Josef; Weingartner, Ernest; Prévôt, André S.H.; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
Abstract. Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 μm) mass. Secondary organic aerosol (SOA) is an important contributor to the OA and can be formed from biogenic and anthropogenic precursors. Here we present results from the characterization of SOA produced from the emissions of three different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from α-pinene. The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra showing Pearson's r values >0.94 for the correlations between the four different SOA types after five hours of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+ and CO2+, respectively, similarly to the relatively fresh semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The atomic O:C ratios were found to be in the range of 0.25–0.55 with no major increase during the first five hours of aging. On average, the diesel SOA showed the lowest O:C ratio followed by SOA from wood burning, α-pinene and the scooter emissions. Grouping the fragment ions revealed that the SOA source with the highest O:C ratio had the largest fraction of small ions. The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended.
01A - Beitrag in wissenschaftlicher Zeitschrift
A novel measurement system for unattended, in situ characterization of carbonaceous aerosols
(Copernicus, 22.12.2023) Keller, Alejandro; Specht, Patrick; Steigmeier, Peter; Weingartner, Ernest [in: Aerosol Research]
Carbonaceous aerosol is a relevant constituent of the atmosphere in terms of climate and health impacts. Nevertheless, measuring this component poses many challenges. There is currently no simple and sensitive commercial technique that can reliably capture its totality in an unattended manner, with minimal user intervention, for extended periods of time. To address this issue we have developed the fast thermal carbon totalizator (FATCAT). Our system captures an aerosol sample on a rigid metallic filter and subsequently analyses it by rapidly heating the filter directly, through induction, to a temperature around 800°C. The carbon in the filter is oxidized and quantified as CO2 in order to establish the total carbon (TC) content of the sample. The metallic filter is robust, which solves filter displacement or leakage problems, and does not require a frequent replacement like other measurement techniques. The limit of detection of our system using the 3σ criterion is TC =0.19 µg-C (micrograms of carbon). This translates to an average ambient concentration of TC =0.32 µg-C m^−3 and TC =0.16 µg-C m^−3 for sampling interval of 1 or 2 h respectively using a sampling flow rate of 10 L min^−1. We present a series of measurements using a controlled, well-defined propane flame aerosol as well as wood-burning emissions using two different wood-burning stoves. Furthermore, we complement these measurements by coating the particles with secondary organic matter by means of an oxidation flow reactor. Our device shows a good correlation (correlation coefficient, R^2>0.99) with well-established techniques, like mass measurements by means of a tapered element oscillating microbalance and TC measurements by means of thermal–optical transmittance analysis. Furthermore, the homogeneous fast-heating of the filter produces fast thermograms. This is a new feature that, to our knowledge, is exclusive of our system. The fast thermograms contain information regarding the volatility and refractoriness of the sample without imposing an artificial fraction separation like other measurement methods. Different aerosol components, like wood-burning emissions, soot from the propane flame and secondary organic matter, create diverse identifiable patterns.
01A - Beitrag in wissenschaftlicher Zeitschrift
A review of more than 20 years of aerosol observation at the high altitude research station Jungfraujoch, Switzerland (3580 m asl)
(Taiwan Association for Aerosol Research, 2016) Bukowiecki, Nicolas; Weingartner, Ernest; Gysel, Martin; Coen, Martine Collaud; Zieger, Paul; Herrmann, Erik; Steinbacher, Martin; Gäggeler, Heinz W.; Baltensperger, Urs [in: Aerosol and Air Quality Research]
01A - Beitrag in wissenschaftlicher Zeitschrift
A single-beam photothermal interferometer for in situ measurements of aerosol light absorption
(Copernicus, 2020) Visser, Bradley; Röhrbein, Jannis; Steigmeier, Peter; Drinovec, Luka; Močnik, Griša; Weingartner, Ernest [in: Atmospheric Measurement Techniques]
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.
01A - Beitrag in wissenschaftlicher Zeitschrift
A study of wood burning and traffic aerosols in an Alpine valley using a multi-wavelength aethalometer
(Elsevier, 20.09.2008) Sandradewi, Jisca; Prévôt, André S.H.; Weingartner, Ernest; Schmidhauser, Ralph; Gysel, Martin; Baltensperger, Urs [in: Atmospheric Environment]
We present a study of aerosol light absorption using a multi-wavelength Aethalometer (l ¼ 370–950 nm) in an Alpine valley where the major local emissions of aerosols in winter are from domestic wood burning and traffic. The measurements were done in winter and summer periods in 2004 and 2005. Much stronger diurnal trends in CO, NOx and aerosol light absorption parameters were observed in winter than in summer. The average (71 S.D.) PM10 concentrations measured at this site were 31.5721.7 mg m 3 in winter and 15.8710.0 mg m 3 in summer. The highest PM10 concentrations were observed between 18:00 and 22:00 h CET in both campaigns, with 45.4721.0 mg m 3 for winter and 21.079.5 mg m 3 for summer. The average (71 S.D.) power law exponents of the absorption coefficients (also called absorption exponent) with l ¼ 370–950 nm, a370–950 nm were 1.670.25 in winter and 1.170.05 in summer. The calculation of a separately for lower and higher wavelengths (i.e., a370–520 nm and a660–950 nm) provided a better description of the wavelength dependence from the UV- to the near-IR region. The highest mean values of a370–520 nm and a660–950 nm were observed between 22:00 and 02:00 h CET in winter with 2.770.4 and 1.370.1, respectively. Comparison of a370–520 nm with CO and NOx data indicated that the relative contribution of wood burning versus traffic was responsible for the seasonal and diurnal variability of a. The seasonal and diurnal trends of a were not attributed to changes in the particle size since the aerosol volume size distributions (dV/d log D) were found to be similar in both campaigns.
01A - Beitrag in wissenschaftlicher Zeitschrift
A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network
(Copernicus, 2015) Paramonov, Mikhail; Kerminen, Veli-Matti; Gysel, Martin; Aalto, Pasi Pekka; Andreae, Meinrat O.; Asmi, Eija; Baltensperger, Urs; Bougiatioti, Aikaterini; Brus, David; Frank, Göran; Good, Nicholas; Gunthe, Sachin S.; Hao, Liqing; Irwin, Martin; Jaatinen, Antti; Jurányi, Zsófia; King, S. M.; Kortelainen, Aki; Kristensson, Adam; Lihavainen, Heikki; Kulmala, Markku; Lohmann, Ulrike; Martin, Scot T.; McFiggans, Gordon; Mihalopoulos, Nikolaos; Nenes, Athanasios; O'Dowd, Colin D.; Ovadnevaite, Jurgita; Petäjä, Tuukka; Pöschl, Ulrich; Roberts, Greg; Rose, Diana; Svenningsson, Birgitta; Swietlicki, Erik; Weingartner, Ernest; Whitehead, James; Wiedensohler, Alfred; Wittbom, Cerina; Sierau, Berko [in: Atmospheric Chemistry and Physics]
Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations – exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol–cloud interactions in various environments.
01A - Beitrag in wissenschaftlicher Zeitschrift
Absorption of light by soot particles: determination of the absorption coefficient by means of aethalometers
(Elsevier, 10/2003) Weingartner, Ernest; Saathoff, Harald; Schnaiter, Martin; Streit, Niklaus; Bitnar, B.; Baltensperger, Urs [in: Journal of Aerosol Science]
01A - Beitrag in wissenschaftlicher Zeitschrift
Adaptation of dry nephelometer measurements to ambient conditions at the Jungfraujoch
(American Chemical Society, 2005) Nessler, Remo; Weingartner, Ernest; Baltensperger, Urs [in: Environmental Science & Technology]
01A - Beitrag in wissenschaftlicher Zeitschrift
Aerosol and NOx emission factors and submicron particle number size distributions in two road tunnels with different traffic regimes
(Copernicus, 21.06.2006) Imhof, David; Weingartner, Ernest; Prévôt, André S.H.; Ordóñez, Carlos; Kurtenbach, Ralf; Wiesen, Peter; Rodler, Johannes; Sturm, Peter; McCrae, Ian; Ekström, M.; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
Measurements of aerosol particle number size distributions (18–700 nm), mass concentrations (PM2.5 and PM10) and NOx were performed in the Plabutsch tunnel, Austria, and in the Kingsway tunnel, United Kingdom. These two tunnels show different characteristics regarding the roadway gradient, the composition of the vehicle fleet and the traffic frequency. The submicron particle size distributions contained a soot mode in the diameter range D=80–100 nm and a nucleation mode in the range of D=20–40 nm. In the Kingsway tunnel with a significantly lower particle number and volume concentration level than in the Plabutsch tunnel, a clear diurnal variation of nucleation and soot mode particles correlated to the traffic density was observed. In the Plabutsch tunnel, soot mode particles also revealed a diurnal variation, whereas no substantial variation was found for the nucleation mode particles. During the night a higher number concentration of nucleation mode particles were measured than soot mode particles and vice versa during the day. In this tunnel with very high soot emissions during daytime due to the heavy-duty vehicle (HDV) share of 18% and another 40% of diesel driven light-duty vehicles (LDV) semivolatile species condense on the pre-existing soot surface area rather than forming new particles by homogeneous nucleation. With the low concentration of soot mode particles in the Kingsway tunnel, also the nucleation mode particles exhibit a diurnal variation. From the measured parameters real-world traffic emission factors were estimated for the whole vehicle fleet as well as differentiated into the two categories LDV and HDV. In the particle size range D=18–700 nm, each vehicle of the mixed fleet emits (1.50±0.08)×10^14 particles km-1 (Plabutsch) and (1.26±0.10)×10^14 particles km-1 (Kingsway), while particle volume emission factors of 0.209±0.008 cm³ km-1 and 0.036±0.004 cm³ km-1, respectively, were obtained. PM1 emission factors of 104±4 mg km-1 (Plabutsch) and 41±4 mg km-1 (Kingsway) were calculated. Emission factors determined in this work were in good agreement with results from other studies.
01A - Beitrag in wissenschaftlicher Zeitschrift
Aerosol and trace gas vehicle emission factors measured in a tunnel using an Aerosol Mass Spectrometer and other on-line instrumentation
(Elsevier, 04/2011) Chirico, Roberto; Prevot, Andre S.H.; DeCarlo, Peter F.; Heringa, Maarten F.; Richter, Rene; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Environment]
In this study we present measurements of gas and aerosol phase composition for a mixed vehicle fleet in the Gubrist tunnel (Switzerland) in June 2008. PM1 composition measurements were made with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) and a Multi Angle Absorption Photometer (MAAP). Gas-phase measurements of CO, CO2, NOx and total hydrocarbons (THC) were performed with standard instrumentation. Weekdays had a characteristic diurnal pattern with 2 peaks in concentrations for all traffic related species corresponding to high vehicle density (∼300 ± 30 vehicles per 5 min) in the morning rush hour between 06:00 and 09:00 and in the afternoon rush hours from approximately 15:30 to 18:30. The emission factors (EF) of OA were heavily influenced by the OA mass loading. To exclude this partitioning effect, only organic aerosol mass concentrations from 60 μg m−3 to 90 μg m−3 were considered and for these conditions the EF(OA) value for HDV was 33.7 ± 2.3 mg km−1 for a temperature inside the tunnel of 20–25 °C. This value is not directly applicable to ambient conditions because it is derived from OA mass concentrations that are roughly a factor of 10 higher than typical ambient concentrations. An even higher EF(OA)HDV value of 47.4 ± 1.6 mg km−1 was obtained when the linear fit was applied to all data points including OA concentrations up to 120 μg m−3. Similar to the increasing EF, the OA/BC ratio in the tunnel was also affected by the organic loading and it increased by a factor of ∼3 over the OA range 10–120 μg m−3. This means that also the OA emission factors at ambient concentrations of around 5–10 μg m−3 would be 2–3 times lower than the emission factor given above. For OA concentrations lower than 40 μg m−3 the OA/BC mass ratio was below 1, while at an OA concentration of 100–120 μg m−3 the OA/BC ratio was ∼1.5. The AMS mass spectra (MS) acquired in the tunnel were highly correlated with the primary organic aerosol (POA) MS from a EURO 3 diesel vehicle with a speed similar to the average tunnel speed.
01A - Beitrag in wissenschaftlicher Zeitschrift
Aerosol climatology and planetary boundary influence at the Jungfraujoch analyzed by synoptic weather types
(Copernicus, 23.06.2011) Collaud Coen, Martine; Weingartner, Ernest; Furger, Markus; Nyeki, Stephan; Prévôt, André S. H.; Steinbacher, Matjaz; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coef-ficients, aerosol number concentration) and trace gases (CO, NOx, SO2) measured at the Jungfraujoch (JFJ, 3580 m a.s.l.) have been analyzed as a function of different synoptic weather types. The Schüepp synoptic weather type of the Alps (SYNALP) classification from the Alpine Weather Statistics (AWS) was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL) influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO2 and NOx concentrations were used as precursor tracers for new particle formation and growth, respectively. The aerosol optical parameters and number concentration show elevated loadings during advective weather types during the December–March period and for the convective anti-cyclonic and convective indifferent weather types during the April–September period. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in win-ter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The frac-tion of PBL air transported to the JFJ was estimated by the relative increase of the specific hu-midity and CO.
01A - Beitrag in wissenschaftlicher Zeitschrift

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