10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Chemical Characterization and Source Contribution to PM2.5 Organic Fraction in Neighboring Towns of Bogota, Colombia
Felipe Villamil, Irene Rosas, James Schauer, NESTOR ROJAS, Universidad Nacional de Colombia
Abstract Number: 1474 Working Group: Source Apportionment
Abstract Fast urbanization processes have occurred in Latin America in the last four decades, making it the region with the highest urbanization rate in the world, with more than 80% of its population living in cities. Unfortunately, rapid growth has not been accompanied by long-term urban planning strategies or robust environmental controls. As a result, and despite improvements made in the last decade, cities in the region have traditionally had an obsolete vehicle fleet and highly polluting industries within densely populated areas. Recent economic growth has worsened the problem by sharply increasing motorization rates as a consequence of higher income per capita and, hence, intensifying traffic congestion and emissions. Small towns and cities within large metropolitan areas or close to larger cities in the region are now following similar processes and some of them have already suffered the impacts of these dynamics.
Air quality in Bogota’s neighboring towns is affected by their own emissions and by pollution transported from this city of more than 8 million inhabitants. However, little is known about the characteristics and sources of pollutants affecting their population. The Sabana Occidente county, with ca. 420,000 inhabitants, and the Soacha county, with ca. 550,000 inhabitants, are of special interest because of the presence of important industrial corridors in the towns of Soacha, Mosquera, Funza, Madrid and Facatativa; mining of construction materials and clay in Soacha; and national roads that connect Bogotá with western and southern cities and the Pacific coast. This work focuses on these counties, with sites in Soacha and Mosquera, where we investigated the contribution of different types of sources to PM2.5. We collected 24-h PM2.5 samples for a two-month period at each site and analyzed them for mass, elemental and organic carbon, water-soluble organic carbon and inorganic ions. We analyzed two- and three-day composites for particle-bond organic tracers. Then we used EPA’s Chemical Mass Balance (CMB) receptor model to determine the source contributions to the particulate organic fraction. Average PM2.5 mass concentrations were similar for Soacha (31 ug/m3) and Mosquera (26 ug/m3). Organic matter was the major component of PM2.5 for all sites, constituting 68% of the PM2.5 mass in Soacha and 63% in Mosquera. We identified 5 sources of the particulate organic fraction at both sites: wood smoke, diesel vehicles, gasoline vehicles, natural gas combustion and industrial coal combustion. However, the contribution differed between sites. Wood smoke was the predominant source in Soacha, accounting for 40% of the organic fraction, followed by gasoline vehicles (18%), diesel vehicles (13%), industrial coal burning (2%) and natural gas burning (1). A quarter of the organic fraction (26%) is contributed by still unidentified sources. In Mosquera, diesel and gasoline vehicles have a similar contribution (18%), followed by wood smoke (10%), industrial coal burning (7%) and natural gas burning (1%). A very significant fraction of organic matter (46%) is contributed by still unidentified sources. Secondary inorganic ions (ammonium, sulfate and nitrate) constitute about 10% of the PM2.5 mass.