Auflistung nach Autor:in "Prévôt, André S. H."

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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
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
Impact of aftertreatment devices on primary emissions and secondary organic aerosol formation potential from in-use diesel vehicles: results from smog chamber experiments
(Copernicus, 06.12.2010) Chirico, Roberto; DeCarlo, Peter F.; Heringa, Maarten F.; Tritscher, Torsten; Richter, René; Prévôt, André S. H.; Dommen, Josef; Weingartner, Ernest; Wehrle, Günther; Gysel, Martin; Laborde, Marie; Baltensperger, Urs
Diesel particulate matter (DPM) is a significant source of aerosol in urban areas and has been linked to adverse health effects. Although newer European directives have introduced increasingly stringent standards for primary PM emissions, gaseous organics emitted from diesel cars can still lead to large amounts of secondary organic aerosol (SOA) in the atmosphere. Here we present results from smog chamber investigations characterizing the primary organic aerosol (POA) and the corresponding SOA formation at atmospherically relevant concentrations for three in-use diesel vehicles with different exhaust aftertreatment systems. One vehicle lacked exhaust aftertreatment devices, one vehicle was equipped with a diesel oxidation catalyst (DOC) and the third vehicle used both a DOC and diesel particulate filter (DPF). The experiments presented here were obtained from the vehicles at conditions representative of idle mode, and for one car in addition at a speed of 60 km/h. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was used to measure the organic aerosol (OA) concentration and to obtain information on the chemical composition. For the conditions explored in this paper, primary aerosols from vehicles without a particulate filter consisted mainly of black carbon (BC) with a low fraction of organic matter (OM, OM/BC < 0.5), while the subsequent aging by photooxidation resulted in a consistent production of SOA only for the vehicles without a DOC and with a deactivated DOC. After 5 h of aging ~80% of the total organic aerosol was on average secondary and the estimated "emission factor" for SOA was 0.23–0.56 g/kg fuel burned. In presence of both a DOC and a DPF, only 0.01 g SOA per kg fuel burned was produced within 5 h after lights on. The mass spectra indicate that POA was mostly a non-oxidized OA with an oxygen to carbon atomic ratio (O/C) ranging from 0.10 to 0.19. Five hours of oxidation led to a more oxidized OA with an O/C range of 0.21 to 0.37.
01A - Beitrag in wissenschaftlicher Zeitschrift
Using aerosol light absorption measurements for the quantitative determination of wood burning and traffic emission contributions to particulate matter
(American Chemical Society, 02.04.2008) Sandradewi, Jisca; Prévôt, André S. H.; Szidat, Sönke; Perron, Nolwenn; Alfarra, M. Rami; Lanz, Valentin A.; Weingartner, Ernest; Baltensperger, Urs
A source apportionment study was performed for particulate matter in the small village of Roveredo, Switzerland, where more than 70% of the households use wood burning for heating purposes. A two-lane trans-Alpine highway passes through the village and contributes to the total aerosol burden in the area. The village is located in a steep Alpine valley characterized by strong and persistent temperature inversions during winter, especially from December to February. During two winter and one early spring campaigns, a seven-wavelength aethalometer, high volume (HIVOL) samplers, an Aerodyne quadrupole aerosol mass spectrometer (AMS), an optical particle counter (OPC), and a Sunset Laboratory OCEC analyzer were deployed to study the contribution of wood burning and traffic aerosols to particulate matter. A linear regression model of the carbonaceous particulate mass in the submicrometer size range CM(PM1) as a function of aerosol light absorption properties measured by the aethalometer is introduced to estimate the particulate mass from wood burning and traffic (PMwb, PMtraffic). This model was calibrated with analyses from the 14C method using HIVOL filter measurements. These results indicate that light absorption exponents of 1.1 for traffic and 1.8–1.9 for wood burning calculated from the light absorption at 470 and 950 nanometers should be used to obtain agreement of the two methods regarding the relative wood burning and traffic emission contributions to CM(PM1) and also to black carbon. The resulting PMwb and PMtraffic values explain 86% of the variance of the CM(PM1) and contribute, on average, 88 and 12% to CM(PM1), respectively. The black carbon is estimated to be 51% due to wood burning and 49% due to traffic emissions. The average organic carbon/total carbon (OC/TC) values were estimated to be 0.52 for traffic and 0.88 for wood burning particulate emissions.
01A - Beitrag in wissenschaftlicher Zeitschrift