Aalto, Pasi Pekka

Artaxo, Paulo

Backman, John Carl Gustav

Carbone, Samara

Hakala, Jani Pietari

Hillamo, Risto

Kulmala, Markku

Manninen, Hanna Elina

Morais, Fernando G.

Nieminen, Tuomo

Petaja, Tuukka

Rizzo, Luciana V.

Siivola, Erkki

Atmospheric Chemistry and Physics Discussions

English

Helsingin yliopiston digitaalinen arkisto

The variability of urban aerosol size distributions and optical properties in São Paulo – Brazil: new particle formation events occur at the site

Abstract. The quest to reduce the dependence on fossil fuel has increased the use of bio-ethanol as an additive to gasoline. The metropolitan area of São Paulo (population 20 million) is a unique laboratory to study the ambient aerosol population caused by the use of bio-fuels because 55% of the fuel used is ethanol. The use of ethanol as an additive to fossil fuel is known to increase aldehyde emissions and when photo chemically oxidized, result in smog. In order to characterize this smog problem total particle number concentration, particle number size distribution, light scattering and light absorption measurement equipment were deployed at the University of São Paulo campus area. Here we present the results from three months of measurements from 10 October 2010 to 10 January 2011. The median total particle number concentration for the sub-micron aerosol typically varies between 1×104–3×104 cm−3 frequently exceeding 5×104 cm−3 during the day. Median diurnal values for light absorption and light scattering vary between 12–33 Mm−1 and 21–64 Mm−1, respectively. The hourly median single-scattering albedo varied between 0.63 and 0.85 indicating a net warming effect on a regional scale. A total of ten new particle formation (NPF) events were observed. During these events, growth rates ranged between 9–25 nm h−1. On average, a calculated sulphuric acid vapour abundance of 2.6× 108 cm−3 would have explained the growth with a vapour production rate of 2.8×106 cm−3 s−1 to sustain it. The estimated sulphuric acid concentration, calculated from global irradiance and sulphur dioxide measurements, accounted for only a fraction of the vapour concentration needed to explain the observed growth rates. This indicates that also other condensable vapours participate in the growth process. During the events, the condensation sink was calculated to be 12× 10−3 s−1 on average.
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J. Backman

L. V. Rizzo

J. Hakala

T. Nieminen

H. E. Manninen

F. Morais

P. P. Aalto

E. Siivola

S. Carbone

R. Hillamo

P. Artaxo

T. Petäjä

M. Kulmala

Crossref

The variability of urban aerosol size distributions and optical  properties in São Paulo – Brazil: new particle formation events occur  at the site

https://helda.helsinki.fi/bitstream/10138/162402/1/acpd_11_30419_2011.pdf

The variability of urban aerosol size distributions and optical properties in São Paulo – Brazil: new particle formation events occur at the site

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Helsingin yliopiston digitaalinen arkisto

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