Abstract
A winter campaign was carried out in Santiago de Chile the year 2012 in two urban sites that can be considered representative for most of the city in order to characterize formation of primary and secondary PM_(1.0) during episodes. One site is located in the campus of the University of Santiago and measurements were carried out with an Aerosol Chemical Speciation Monitor and a black carbon monitor. Another site is located in a large park, about 2 km south-east of the first site, measurements of CO, NO_x, SO_2, O_3 were done in this site. A noticeable increase in most of the primary components of PM_(1.0) (black carbon and organics) and primary gases (CO and NO) was observed during days in which the average PM_(1.0) concentration was higher than 50 μg m^(-3) (episode). A small increase or no change was observed in the secondary pollutants (NH_4, NO_3, SO_4 and NO_2) at night during these episodes. Positive Matrix Factorization was used to extract four components from the ACSM data: hydrocarbon-like organic aerosol (HOA), biomass burning OA (BBOA), low volatility oxygenated OA (LV-OOA) and semi-volatile oxygenated OA (SV-OOA). The freshly generated components (HOA and BBOA) showed a clear increase at night during episodes, while the aged fraction of organic aerosol (LV-OOA and SVOOA) showed a smaller increase or a decrease at night during episodes. Correlation of HOA and BBOA components with primary pollutants was also high, indicating that freshly created aerosols (HOA, BBOA and BC) are in large part responsible for the increase in pollution at night during episodes in Santiago de Chile.
Highlights
Santiago, Chile’s capital is a large city (6 million of people) in South America that is surrounded by hills and experiences adverse meteorological conditions that favor high pollution during winter
A variable part of PM2.5 corresponds to black carbon (BC) and brown carbon (BrC) (Kirchstetter and Novakov, 2004), which strongly absorb light across the spectrum and are believed to be the second most important pollutant associated to global warming (Ramanathan and Carmichael, 2008; Bond et al, 2013; Liu et al, 2015)
Between 9 March and 5 July 2012 continuous measurements of non-refractory PM1.0 were done with an Aerosol Chemical Speciation Monitor (ACSM, Aerodyne Research, Inc.), black carbon was measured with an optical monitor developed at the University (Gramsch et al, 2000)
Summary
Chile’s capital is a large city (6 million of people) in South America that is surrounded by hills and experiences adverse meteorological conditions that favor high pollution during winter. A noticeable increase in most of the primary components of PM1.0 (black carbon and organics) and primary gases (CO and NO) was observed during days in which the average PM1.0 concentration was higher than 50 μg m–3 (episode).
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