Prevalence of Freshly Generated Particles during Pollution Episodes in Santiago de Chile

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 SV-OOA) 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.

Temporal evolution of main ambient PM<sub>2. 5</sub> sources in Santiago, Chile, from 1998 to 2012

“…The third source was identified as "copper smelters". It contains almost all As measured (79 %) and its S / As ratio of 23 is close to the values of 17, 15 and 18 obtained in copper smelter profiles resolved by PMF with ambient data from the cities of Rancagua (Kavouras et al, 2001), Quillota (Hedberg et al, 2005), and Las Condes (Santiago; Jorquera and Barraza, 2012), respectively. Other relevant tracer species found in this source were Cu (21.4 %) and S (18.9 %), which were also identified in a previous study on Santiago (Jorquera and Barraza, 2012).…”

Variability in the primary emissions and secondary gas and particle formation from vehicles using bioethanol mixtures

“…Primary organic carbon (OC) and black carbon (BC) are directly emitted by vehicles, whereas secondary organic aerosol is formed in the atmosphere through the reaction of volatile organic compounds (VOCs) with nitric oxide (NO), ozone (O 3 ), isoprene, 1,3-butadiene, bencene, 2,3-dimethyl-1,3-butadiene, and other radicals under the influence of solar light (Lambe et al, 2015;Sato et al, 2012;Volkamer et al, 2006). Since 2005, OC has been the only fraction of PM 2.5 that has shown a significant increase in Santiago (Gramsch et al, 2016). This increase is consistent with the growth in the number of CONTACT E. Gramsch egramsch@gmail.com Department of Physics, University of Santiago de Chile, Av.…”

Spatiotemporal Variation in Composition of Submicron Particles in Santiago Metropolitan Region, Chile

“…In Europe and the United States, research involving the ACSM has been extensively conducted in urban and rural locations, nevertheless, there is still little information on the composition of submicron particles in the main cities of the southern hemisphere. To date, measurements in Latin America have been carried out only in Sao Paulo, Brazil (Almeida et al, 2014), Mexico City (Salcedo et al, 2006), and Santiago, Chile (Carbone et al, 2013;Gramsch et al, 2016).…”

“…Further, a considerable proportion of this fraction was identified as oxidized, which supported previous studies indicating the strong photochemical potential of the local atmosphere. The following year, the composition of submicron particles during the wintertime pollution episodes was measured, evidencing a notable increase of fresh particles (non-oxidized) during the night, which were associated with recent emissions of vehicular exhaust and biomass burning (Gramsch et al, 2016).…”