On the diurnal cycle of urban aerosols, black carbon and the occurrence of new particle formation events in springtime São Paulo, Brazil

On the diurnal cycle of urban aerosols, black carbon and the occurrence of new particle formation events in springtime São Paulo, Brazil

Author Backman, John Google Scholar
Rizzo, Luciana Varanda Autor UNIFESP Google Scholar
Hakala, Jani Google Scholar
Nieminen, Tuomo Google Scholar
Manninen, Hanna E. Google Scholar
Morais, Flavia Google Scholar
Aalto, Pasi P. Google Scholar
Siivola, Erkki Google Scholar
Carbone, Samara Google Scholar
Hillamo, Risto Google Scholar
Artaxo, Paulo Google Scholar
Virkkula, A. Google Scholar
Petaja, Tuukka Google Scholar
Kulmala, Markku Google Scholar
Institution Univ Helsinki
Universidade Federal de São Paulo (UNIFESP)
Universidade de São Paulo (USP)
Finnish Meteorol Inst
Abstract Large conurbations are a significant source of the anthropogenic pollution and demographic differences between cities that result in a different pollution burden. the metropolitan area of São Paulo (MASP, population 20 million) accounts for one fifth of the Brazilian vehicular fleet. A feature of MASP is the amount of ethanol used by the vehicular fleet, known to exacerbate air quality. the study describes the diurnal behaviour of the submicron aerosol and relies on total particle number concentration, particle number size distribution, light scattering and light absorption measurements. Modelled planetary boundary layer (PBL) depth and air mass movement data were used to aid the interpretation. During morning rush-hour, stagnant air and a shallow PBL height favour the accumulation of aerosol pollution. During clear-sky conditions, there was a wind shift towards the edge of the city indicating a heat island effect with implications on particulate pollution levels at the site. the median total particle number concentration for the submicron aerosol typically varied in the range 1.6 x 10(4)-3.2 x 10(4) cm(-3) frequently exceeding 4 x 10(4) cm-3 during the day. During weekdays, nucleation-mode particles are responsible for most of the particles by numbers. the highest concentrations of total particle number concentrations and black carbon (BC) were observed on Fridays. Median diurnal values for light absorption and light scattering (at 637 nm wavelength) varied in the range 12-33 Mm(-1) and 21-64 Mm(-1), respectively. the former one is equal to 1.8-5.0 mu g m(-3) of BC. the growth of the PBL, from the morning rush-hour until noon, is consistent with the diurnal cycle of BC mass concentrations. Weekday hourly median single-scattering albedo (omega(0)) varied in the range 0.59-0.76. Overall, this suggests a top of atmosphere (TOA) warming effect. However, considering the low surface reflectance of urban areas, for the given range of omega(0), the TOA radiative forcing can be either positive or negative for the sources within the MASP. On the average, weekend omega(0) values were 0.074 higher than during weekdays. During 11% of the days, new particle formation (NPF) events occurred. the analysed events growth rates ranged between 9 and 25 nm h(-1). Sulphuric acid proxy concentrations calculated for the site were less than 5% of the concentration needed to explain the observed growth. Thus, other vapours are likely contributors to the observed growth.
Language English
Sponsor Academy of Finland via the Sustainable Energy Research Programme (SusEn)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Academy of Finland Centre of Excellence program
European Research Council (ERC)
Academy of Finland
Grant number Academy of Finland via the Sustainable Energy Research Programme (SusEn): 1133603
Academy of Finland Centre of Excellence program: 1118615
Academy of Finland: 139656
Date 2012-01-01
Published in Atmospheric Chemistry and Physics. Gottingen: Copernicus Gesellschaft Mbh, v. 12, n. 23, p. 11733-11751, 2012.
ISSN 1680-7316 (Sherpa/Romeo, impact factor)
Publisher Copernicus Gesellschaft Mbh
Extent 11733-11751
Origin http://dx.doi.org/10.5194/acp-12-11733-2012
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000312665300031
URI http://repositorio.unifesp.br/handle/11600/34409

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