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Size-Segregated Ions and Carbonaceous Fractions of Ambient Aerosol in Bogota
LADY MATEUS, Nestor Rojas, Kelly Burbano, Rodrigo Jimenez, Universidad Nacional de Colombia
Abstract Number: 671
Working Group: Urban Aerosols
Abstract
Size-segregated chemical characterization of ambient aerosol is useful to understand its sources and formation mechanisms, and complements information obtained from bulk aerosol composition. Elemental and Organic Carbon (EC/OC) make up a significant fraction of matter particulate emitted by combustion processes, and water-soluble ions provide an important information about the origin of ambient aerosols. Previous studies have determined the chemical composition and source contribution of PM10 and the temporal and spatial variability of polycyclic aromatic hydrocarbons (PAH) in Bogota, one of the main megacities of Latin America. However, the size-segregated chemical composition of ambient aerosol has not been studied. This work aims to better understand the size-segregated variability of the aerosol chemical composition in this city. A Tisch® 8-Stage Cascade Andersen Impactor was used to collect the samples of ambient aerosol in the southwest area of the city, which usually show the highest concentrations of PM2.5. Eight sets of size-segregated ambient aerosol samples were collected over two periods in 2018 to quantify the concentration of OC/EC and water-soluble ions (ammonium, sodium, potassium, magnesium, calcium, chloride, nitrate, sulfate and oxalate). The average PM1 concentration during the sampling campaign was 20.8 ±12.5 µg/m3 (70.8 ± 10.7 % of PM2.5). The mass size distribution was bimodal, with a coarse mode between 5.8 and 4.7 µm, and an accumulation mode between 0.43 and 0.65 µm. The carbonaceous fraction constituted over 75 % of PM1 mass. The main component of the finest particles was EC, which can penetrate and deposit on alveolar sacs of people exposed to air pollution in this area of the city. The main inorganic ions were sulfate, nitrate, and ammonium, which had the maximum concentration in the range of 0.65 - 1.1 µm. The PM1 concentration showed a moderate correlation with the concentrations of OC, EC, nitrate, calcium, and ammonium.