Study of the Dispersion of Carbon Monoxide Associated with Vehicular Emission in the Metropolitan Region of Porto Alegre with the Numerical Modeling System CCATT - BRAMS

Abstract Air pollution directly affects the urban areas inhabitants, with a potential impact on health, especially when associated with respiratory diseases. The mobile sources are the main pollutants responsible for the primary emission and secondary formation of chemical compounds in the atmosphere, such as carbon monoxide, nitrogen oxides, particulate matter, and ozone. The local air quality continuous monitoring is extremely important for the municipal environmental policies but is not feasible due to the high cost of equipment. An alternative is the use of numerical modeling to air quality forecast at the local and regional scales. But the numerical models have a number of uncertainties and are dependent on emission inventories for good accuracy of dispersion and chemistry simulations. However, Brazil lacks local inventories, especially in high spatial resolution, which makes local modeling difficult to use in the control and mitigation of air pollution. In this context, this work aims the study of carbon monoxide dispersion in the Metropolitan Region of Porto Alegre (MRPA), in the Rio Grande do Sul state, using the CCATT-BRAMS system, with emphasis on vehicular sources. Two periods - January 2009 and January 2016 - were analyzed using the FEPAM precursor gas inventory information for the 2009 and 2013 base years respectively, spatially distributed in the PREP-CHEM-SRC emissions preprocessor. In general, the simulations consistently represented the data observed by the monitoring network, with RMSE below 0.3 in most stations evaluated. Sensitivity analyses also revealed that approximately 40% of the concentration of carbon monoxide over the municipality of Porto Alegre (Main city of MRPA) occurs due to large-scale transport.