10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Seasonality of Air Pollution in Bogota: From Regional Biomass Burning Transport to Local Sources
RICARDO MORALES BETANCOURT, Luis Carlos Belalcazar, Juan Felipe Mendez, Maria Paula Perez-Peña, Yadert Contreras Barbosa, Juan Pablo Ayala, Universidad de los Andes
Abstract Number: 1642 Working Group: Air Quality in Megacities: from Sources to Control
Abstract In this research we determined the salient aspects controlling the seasonality of air pollution levels in the city of Bogota. Bogota is a large metropolitan area located in the northern South American Andes. With a population of nearly eight million inhabitants, Bogotá has experienced a rapid growth in motorization rates and the air pollution levels in the city very often exceed WHO limits. Many studies have focused on the large impact of local mobile and industrial sources on local air quality. However, there is a lack of understanding of the role that meteorological variables and long-range transport of pollutants can have in the seasonal variations of air pollution levels in the city. The precipitation and hence biomass burning seasons in northern South America are markedly different to those of Amazonia. Despite the fires in northern South America are not a significant contributor to global inventories, they can potentially impact regional air pollution levels. In this work we quantify the contribution of meteorological conditions and regional transport of biomass burning plumes to the seasonality of particulate matter pollution in the city. The climatology of variables impacting atmospheric stability in the northern South American Andes are determined both through a decade-long record of radiosonde data, as well as reanalysis data. The seasonal cycle of particulate pollution in the city is shown to be only partially explained by the climatology of atmospheric stability indices. The potential of biomass burning plumes transported to the city during the dry season is explored here as a candidate variable to explain the remaining unexplained seasonal variability in PM pollution. We used 10 years of MODIS Active Fire Data and HYSPLIT calculated back-trajectories. The number of fires that could impact the air quality in the city is determined by considering only those hot-spots located within a spatial buffer of the HYSPLIT simulated back-trajectory location for air masses reaching the city. In this way only, those fires that are potentially causally related to air pollution levels are accounted for. Two meteorological datasets were used to run the HYSPLIT back-trajectory model finding similar results. A strong correlation between the number of fires detected with this method and PM10 and PM2.5 levels is observed. Finally, we performed simulations with the WRF-Chem chemical transport model coupled to meteorology, to model the long-range transport of biomass burning pollutants during the dry and wet seasons. Our study suggests that a significant portion of the seasonal variations in PM pollution levels for the city of Bogota can be explained by seasonal changes in atmospheric stability and seasonal regional transport of biomass burning plumes. The contribution of local sources is isolated in the simulation performing sensitivity analysis to mobile and industrial local sources from a local emission inventory.