Suchergebnisse

Access to detailed comparisons in air quality variations encountered when commuting through a city offers the urban traveller more informed choice on how to minimise personal exposure to inhalable pollutants. In this study we report on an experiment designed to compare atmospheric contaminants inhaled during bus, subway train, tram and walking journeys through the city of Barcelona. Average number concentrations of particles 10-300 nm in size, N, are lowest in the commute using subway trains (N5.0×104cm-3), with extreme transient peaks at busy traffic crossings commonly exceeding 1.0×105cm-3 and accompanied by peaks in Black Carbon and CO. Subway particles are coarser (mode 90nm) than in buses, trams or outdoors (1200ppm in crowded buses and trains. There are also striking differences in inhalable particle chemistry depending on the route chosen, ranging from aluminosiliceous at roadsides and near pavement works, ferruginous with enhanced Mn, Co, Zn, Sr and Ba in the subway environment, and higher levels of Sb and Cu inside the bus. We graphically display such chemical variations using a ternary diagram to emphasise how "air quality" in the city involves a consideration of both physical and chemical parameters, and is not simply a question of measuring particle number or mass. © 2015 The Authors. ; This work was supported by the ACS Foundation contributing to the dissemination of good environmental practices and environmental protection activities, the Spanish Ministry of Economy and Competitiveness and FEDER funds within the I+D Project CGL2012-33066 (METRO), and the IMPROVE LIFE project ( LIFE13 ENV/ES/000263 ). VM and ASF acknowledge funding from the European Union Seventh Framework Programme ( FP7/2007-2013 ) for a Marie Curie ITN (Grant agreement no. 315760 HEXACOMM ). Additional funding from AXA Research Fund is acknowledged. Fulvio Amato is beneficiary of the Juan de la Cierva postdoctoral Grant ( JCI-2012-13473 ) from the Spanish Ministry of Economy and Competitiveness. Appendix A ; Peer reviewed

Ground-level and vertical measurements (performed using tethered and non-tethered balloons), coupled with modelling, of ozone (O3), other gaseous pollutants (NO, NO2, CO, SO2) and aerosols were carried out in the plains (Vic Plain) and valleys of the northern region of the (BMA) in July 2015, an area typically recording the highest O3 episodes in Spain. Our results suggest that these very high O3 episodes were originated by three main contributions: (i) the surface fumigation from high O3 reservoir layers located at 1500-3000 mg-a.g.l. (according to modelling and non-tethered balloon measurements), and originated during the previous day(s) injections of polluted air masses at high altitude; (ii) local/regional photochemical production and transport (at lower heights) from the BMA and the surrounding coastal settlements, into the inland valleys; and (iii) external (to the study area) contributions of both O3 and precursors. These processes gave rise to maximal O3 levels in the inland plains and valleys northwards from the BMA when compared to the higher mountain sites. Thus, a maximum O3 concentration was observed within the lower tropospheric layer, characterised by an upward increase of O3 and black carbon (BC) up to around 100-200 m a.g.l. (reaching up to 300 μg mg-3 of O3 as a 10 s average), followed by a decrease of both pollutants at higher altitudes, where BC and O3 concentrations alternate in layers with parallel variations, probably as a consequence of the atmospheric transport from the BMA and the return flows (to the sea) of strata injected at certain heights the previous day(s). At the highest altitudes reached in this study with the tethered balloons (900-1000 m a.g.l.) during the campaign, BC and O3 were often anti-correlated or unrelated, possibly due to a prevailing regional or even hemispheric contribution of O3 at those altitudes. In the central hours of the days a homogeneous O3 distribution was evidenced for the lowest 1 km of the atmosphere, although probably important variations could be expected at higher levels, where the high O3 return strata are injected according to the modelling results and non-tethered balloon data. Relatively low concentrations of ultrafine particles (UFPs) were found during the study, and nucleation episodes were only detected in the boundary layer. Two types of O3 episodes were identified: type A with major exceedances of the O3 information threshold (180 μg mg-3 on an hourly basis) caused by a clear daily concatenation of local/regional production with accumulation (at upper levels), fumigation and direct transport from the BMA (closed circulation); and type B with regional O3 production without major recirculation (or fumigation) of the polluted BMA/regional air masses (open circulation), and relatively lower O3 levels, but still exceeding the 8 h averaged health target. To implement potential O3 control and abatement strategies two major key tasks are proposed: (i) meteorological forecasting, from June to August, to predict recirculation episodes so that NOx and VOC abatement measures can be applied before these episodes start; (ii) sensitivity analysis with high-resolution modelling to evaluate the effectiveness of these potential abatement measures of precursors for O3 reduction. © 2017 Author(s). ; The present work was supported by the Spanish Ministry of Economy and Competitiveness and FEDER funds under the project HOUSE (CGL2016-78594-R), by the Generalitat de Catalunya (AGAUR 2015 SGR33 and the DGQA). Part of this research was supported by the Korean Ministry of the Environment through "The Eco-Innovation project". The participation of University of Marseille and University of Birmingham was partially supported by two TNA actions projects carried out under the ACTRIS2 project (grant agreement No. 654109) financed by the European Union's Horizon 2020 research and innovation program. The support of the CUD of Zaragoza (project CUD 2013-18) is also acknowledged. We are very thankful to the Generalitat de Catalunya for supplying the air quality data from the XVPCA stations, to METEOCAT (the Meteorological Office of Catalonia) for providing meteorological data and to the IES J. Callís and the Meteorological Station from Vica (especially to Manel Dot) for allowing the performance of the vertical profiles and mobile unit measurements, respectively. In memoriam of Andrei Lyasota ; Peer reviewed