lnstitut für Sensorik und Elektronik
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Publikation Convective boundary layer evolution to 4 km asl over High‐alpine terrain. Airborne lidar observations in the Alps(Wiley, 01.03.2000) Nyeki, Stephan; Kalberer, Markus; Colbeck, Ian; De Wekker, Stephan; Furger, Markus; Gäggeler, Heinz W.; Koßmann, Meinolf; Lugauer, Matthias; Steyn, Douw; Weingartner, Ernest; Wirth, Martin; Baltensperger, UrsMountain ranges have important influences on the structure and composition of the convective boundary layer (CBL) and free troposphere (FT). Evolution of the summer CBL, measured over the European Alps using airborne lidar, was clearly observed to attain a near-uniform height up to 4.2 km asl by early afternoon. A climatology of in-situ high-alpine aerosol measurements suggests that such substantial growth, corresponding to ∼ 0.3 of the mid-latitude tropopause height, often occurs during summer months. Subsequent nocturnal collapse of the CBL was estimated to result in the venting of ∼ 0.8 ± 0.3 (SO4 4) Gg/day into a FT residual layer, leeward of the Alps.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Characterization of size-fractionated aerosol from the Jungfraujoch (3580 m asl) using total reflection x-ray fluorescence (TXRF)(Taylor & Francis, 22.09.2000) Streit, Niklaus; Weingartner, Ernest; Zellweger, Christoph; Schwikowski, Margit; Gäggeler, Heinz W.; Baltensperger, UrsDuring three field campaigns at the Jungfraujoch High Alpine Research Station, Switzerland, size-fractionated aerosol was collected using a cascade impactor. The particles were impacted on silicon oil-coated quartz sampling substrates. The actual analysis was then performed directly on these quartz sampling substrates using total reflection X-ray fluorescence. The resulting size distributions of 16 elements (S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Se, Br, Rb, Sr, Y, Zr, Pb) were investigated to determine the best cut-off diameter to distinguish between geogenic and anthropogenic particles. The obtained cut-off diameter of 1 μm is an important parameter in the current world-wide measurements under the auspices of the World Meteorological Organization's Global Atmosphere Watch aerosol project.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Study on the chemical character of water soluble organic compounds in fine atmospheric aerosol at the Jungfraujoch(Springer, 07/2001) Krivácsy, Zoltán; Gelencsér, András; Kiss, Gyula; Mészáros, Ernő; Molnár, Ágnes; Hoffer, András; Mészáros, Tamás; Sárvári, Zsolt; Temesi, Dóra; Varga, Bálint; Baltensperger, Urs; Nyeki, Stephan; Weingartner, ErnestIn this study the chemical nature of the bulk of water soluble organic compounds in fine atmospheric aerosol collected during summer 1998 at the Jungfraujoch, Switzerland (3580 m asl) is characterised. The mass concentration of water soluble organic substances was similar to those of major inorganic ions, and the water soluble organic matter was found to be composed of two main fractions: (i) highly polyconjugated, acidic compounds with a varying degree of hydrophobicity and (ii) slightly polyconjugated, neutral and very hydrophilic compounds. The contribution of both fractions to the total water soluble organic carbon was about 50%. Separation into individual components was impossible either by HPLC or capillary electrophoresis which indicates the presence of a high number of chemically similar but not identical species. Results obtained by ultrafiltration and HPLC-MS have shown that the molecular weights are of the order of several hundreds. Most of the protonation constants for the acidic compounds determined by capillary electrophoresis were in the range 10⁴-10⁷.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Summertime NOy speciation at the Jungfraujoch, 3580 m above sea level, Switzerland(Wiley, 16.03.2000) Zellweger, Christoph; Ammann, Markus; Buchmann, Brigitte; Hofer, Patrick; Lugauer, Matthias; Rüttimann, Ralph; Streit, Niklaus; Weingartner, Ernest; Baltensperger, UrsDuring summer 1997, speciated reactive nitrogen (NO, NO2, peroxyacetyl nitrate (PAN), HNO3, and particulate nitrate) was measured in conjunction with total reactive nitrogen (NOy) at the high-alpine research station Jungfraujoch (JFJ), 3580 m above sea level (asl). The individually measured NOy components averaged to 82% of total NOy. PAN was the most abundant reactive nitrogen compound and composed on average 36% of NOy, followed by NOx, (22%), particulate nitrate (17%), and HNO3 (7%). The NOx/NOy ratio averaged 0.25, but significantly lower values (0.15–0.20) were observed in the presence of high NOy mixing ratios. A classification of the data by synoptic weather conditions indicated that thermally driven vertical transport has a strong impact on the mixing ratios measured at the JFJ during summer. A strong diurnal cycle with maximum mixing ratios in the late afternoon was observed for convective days with north-westerly advection at 500 hPa. In contrast, during a period of convective days with a wind speed below 7.5 m/s at 500 hPa, no obvious diurnal cycle was observed. Under these meteorological conditions the convective boundary layer can be significantly higher over the Alps (i.e., around 4 km asl) than over the surrounding lowlands. Subsequent advection may finally result in the export of reactive nitrogen reservoir compounds to the free troposphere and hence influence global atmospheric chemistry.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Separate determination of PM10 emission factors of road traffic for tailpipe emissions and emissions from abrasion and resuspension processes(Inderscience, 28.10.2004) Gehrig, Robert; Hill, Matz; Buchmann, Brigitte; Imhof, David; Weingartner, Ernest; Baltensperger, UrsLittle is known about the relevance of mechanically produced particles of road traffic from abra-sion and resuspension processes in relation to the exhaust pipe particles. In this paper, emis-sion factors of PM10 and PM1 for light and heavy-duty vehicles were derived for different repre-sentative traffic regimes from concentration differences of particles and nitrogen oxides (NOₓ) in ambient air upwind and downwind of busy roads, or alternatively of kerbsides and nearby back-ground sites. Hereby, PM1 was interpreted as direct exhaust emissions and PM10-PM1 as me-chanically produced emissions from abrasion and resuspension processes. The results show that abrasion and resuspension processes represent a significant part of the total primary PM10 emissions of road traffic. At sites with relatively undisturbed traffic flow they are in the same range as the exhaust pipe emissions. At sites with disturbed traffic flow due to traffic lights, emissions from abrasion/resuspension are even higher than those from the exhaust pipes.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation 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, Urs01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Carbon mass determinations during the AIDA soot aerosol campaign 1999(Elsevier, 10/2003) Saathoff, Harald; Naumann, Karl-Heinz; Schnaiter, Martin; Schöck, Werner; Weingartner, Ernest; Baltensperger, Urs; Krämer, Lutz; Bozoki, Zoltan; Pöschl, Ulrich; Niessner, Reinhard; Schurath, UlrichDuring the soot aerosol campaign particle carbon mass concentrations of Diesel soot, spark generated “Palas” soot, external and internal mixtures of Diesel soot with (NH4)2SO4, and particles coated with secondary organic aerosol material were determined by several different methods. Two methods were based on thermochemical filter analysis with coulometric and NDIR detection of evolved CO2 (total carbon, TC and elemental carbon, EC) and four methods employed optical techniques: aethalometry (black carbon, BC), photoacoustic soot detection (BC), photoelectron emission, and extinction measurement at 473 nm. Furthermore, β-attenuation (total particulate mass), FTIR spectroscopy (sulphate), and COSIMA model calculations were used to determine particle mass concentrations. The general agreement between most methods was good although some methods did not reach their usual performance. TC determined by coulometric filter analysis showed good correlations with optical extinction, photoacoustic BC signal, and photoelectron emission data. However, the evolution of the photoelectron emission signal correlated with changes in accessible surface area rather than mass concentration and was very sensitive to surface conditions. The BC content as measured by the aethalometers approximately equal to less than 70% of the EC content for Diesel soot and amounts to less than 25% of the EC content of “Palas” soot.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Coating of soot and (NH4)2SO4 particles by ozonolysis products of α-pinene(Elsevier, 10/2003) Saathoff, Harald; Naumann, Karl-Heinz; Schnaiter, Martin; Schöck, Werner; Möhler, Ottmar; Schurath, Ulrich; Weingartner, Ernest; Gysel, Martin; Baltensperger, UrsThe ozonolysis of α-pinene in a large aerosol chamber was used to generate secondary organic aerosol (SOA) mass by homogeneous nucleation, or by heterogeneous nucleation, either on soot, or on (NH4)2SO4 seed aerosols. The rate of the α-pinene + ozone reaction and the aerosol yield of ∼19% are in good agreement with literature data. The organic coating of soot particles leads to a compaction of the fractal agglomerates expressed by an increase in fractal dimension from 1.9 to 2.1 for Diesel soot, and from 2.0 to 2.3 for spark generated “Palas” soot. The dielectric coating of the soot particles with SOA layers between 2 to 11 nm gives rise to a substantial enhancement of their single scattering albedo, from about 0.2 to 0.5, and increases the effective absorption coefficients of both soot types by ca. 30%. The coating of both soot types increases the hygroscopic growth factors (HGF) to values close below the HGF measured for pure SOA material d/d0∼1:12 at 90% RH.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Partitioning of reactive nitrogen (NOy) and dependence on meteorological conditions in the lower free troposphere(Copernicus, 19.06.2003) Zellweger, Christoph; Forrer, Jann; Hofer, Peter; Nyeki, Stephan; Schwarzenbach, Beat; Weingartner, Ernest; Ammann, Markus; Baltensperger, UrsResults of continuous nitrogen oxide (NO), nitrogen dioxide (NO2), peroxyacetyl nitrate (PAN) and total reactive nitrogen (NOy) measurements along with seasonal field campaigns of nitric acid (HNO3) and particulate nitrate (NO3-) measurements are presented for a two-year period at the high-alpine research station Jungfraujoch (JFJ), 3580 m asl. The NOy mixing ratio and partitioning is shown to strongly depend on meteorological conditions. Knowledge of these meteorological transport processes allows discrimination between undisturbed (i.e. clean) and disturbed (i.e. influenced by regional pollution sources) free tropospheric (FT) conditions at the JFJ. Median NOy concentrations during undisturbed FT periods ranged from 350 pptv (winter, December to February) to 581 pptv (spring, March to May). PAN was found to be the dominant NOy species during spring and summer, whereas NO2 was most abundant during autumn and winter. Particulate nitrate was found to contribute significantly to total NOy during thermally induced vertical transport. Föhn events, synoptical lifting (e.g. fronts) and thermally induced vertical transport resulted in mixing ratios up to 10 times higher at the JFJ compared to undisturbed FT conditions. Furthermore, this meteorological variability of the NOy concentration and partitioning often dominated the seasonal variability. As a consequence the use of filters at the JFJ (and other mountainous sites) is crucial for the interpretation of data from such measurement sites. This study presents a further development of meteorological filters for the high-alpine site Jungfraujoch, which also could be modified and adapted to other mountainous measurement sites.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Properties of jet engine combustion particles during the PartEmis experiment: Hygroscopicity at subsaturated conditions(Wiley, 06.06.2003) Gysel, Martin; Nyeki, Stephan; Weingartner, Ernest; Baltensperger, Urs; Giebl, Heinrich; Hitzenberger, Regina; Petzold, Andreas; Wilson, C. W.Hygroscopic properties of combustion particles were measured online with a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) during PartEmis jet engine combustor experiments. The combustor was operated at old and modern cruise conditions with fuel sulfur contents (FSC) of 50, 410 and 1270 μg/g, and hygroscopic growth factors (HGF) of particles with different dry diameters were investigated at relative humidities RH ≤ 95%. HGFs increased strongly with increasing FSC (HGF[95% RH, 50 nm, modern cruise] = 1.01 and 1.16 for low and high FSC, respectively), and decreased with increasing particle size at fixed FSC, whereas no significant difference was detected between old and modern cruise. HGFs agreed well with a two-parameter theoretical model which provided an estimate of the sulfuric acid content of dry particles, indicating a nearly linear dependence on FSC.01A - Beitrag in wissenschaftlicher Zeitschrift