Impact of the use of biofuels on the formation of ultrafine particles in southeastern Brazil

Southeastern Brazil is the most developed and populous region with 89.5 million of inhabitants, according to the Instituto Brasileiro de Geografia e Estatística (IBGE) for 2021. The main metropolitan and industrialized areas are concentrated in its four states (São Paulo, Minas Gerais, Rio de Janeiro and Espírito Santo). One of them comprises the Metropolitan Area of São Paulo (MASP) with 7.3 million vehicles that releases air pollutant -gas and ultrafine particles- to the atmosphere due to the use of different fuel types; light-duty vehicles consume ethanol, gasohol (85% gasoline and 25% hydrous ethanol) or natural gas, and heavy vehicles (i.e., buses and trucks) run on diesel. So, frequently high concentrations of air pollutants (ozone and fine particles) in urban areas are above the recommended limits suggested by the World Health Organization (WHO) with high health risk mainly for children and elderly. The biggest concern is the high health risk of exposing the population to ultrafine particles, also called nanoparticles. Consequently, it is important to understand the formation of ultrafine particles, whether they are emitted directly or formed in the atmosphere. 

We study the formation processes of ultrafine particles in the scenario of fuel change in the road transport sector, including a greater use of biofuels. The air quality modeling system will analyze the impact of different scenarios in urban areas in southeastern Brazil. We begin with the air quality simulation for the current conditions as the base case scenario using the WRF-Chem model. As the main data input, we use emission data with two temporal profile distributions (monthly and hourly time average). First, we use available monthly anthropogenic emission's data processed by the European Copernicus Atmosphere Service (CAMS). Secondly, we added hourly road transport emission calculated with the LAPAT model, which use emission factors derived from measurements in experimental campaigns in tunnels where light and heavy vehicles circulate within the MASP. This simulation test with the WRF-Chem model considers the MOZART-MOSAIC mechanism and additional emissions from other sources such as biomass burning and chemical initial and boundary conditions from the CAM-Chem model. Experimental data and measurements of meteorological and air quality parameters will support the work to evaluate the performance of the model’s results.