Study of light volatile organic compounds composition: vehicle contribution impact in air pollution in São Paulo Metropolitan Region

Abstract

The Metropolitan Area of São Paulo (MASP), a megacity located in southeastern Brazil with a population about 20 million inhabitants in an area of 8,511 km2, is one of the largest megacities in the world, containing the city of São Paulo and 38 more cities. In the MASP, there are approximately 6.7 million passenger and commercial vehicles being 85% light-duty vehicles (LDVs), 3% heavy-duty vehicles (HDVs, which run on diesel 95% + 5% biodiesel) and 12% motorcycles. Approximately 55% of the LDVs using a mixture of 78% (v / v) gasoline and 22% ethanol (gasohol), 4% using hydrous ethanol (95% ethanol and 5% water), 38% are flex-fuel, which are capable running either gasohol and ethanol, and 2% use diesel (containing 5% biodiesel) (Cetesb 2013). According São Paulo State Environmental Agency - CETESB (Cetesb 2012), vehicles are responsible for issuing (into the atmosphere) 97% of all carbon monoxide (CO), 85% of hydrocarbons (HC), 82% nitrogen oxides (NOx), 36% of sulfur dioxide (SO2), and 36% of all inhalable particulate matter (PM10). These data indicate that the main source of air pollution in the MASP is vehicular emission. In this study, air quality monitoring will be performed by monitoring of pollutants such as ozone, nitrogen oxides, hydrocarbons - ethane, ethylene, propane, propylene, iso-butane, n-butane, acetylene, trans-2-butene, 1 -butene, cis-2-butene, cilcopentano, isopentane, n-pentane, trans-2-pentene, 1-pentene, cis-2-pentene, 2,4-dimethylbutane and 2,3-dimethylpentane. Statistical correlations between these species will be undertaken with a view to help identify the emission sources. The correlation between species as acetylene and ethylene are frequently used as tracers of vehicle emission, since these species are mainly emitted by vehicles, particularly those containing catalytic exhaust system, while n-butane, trans-2-butene, n-pentane are used as tracers of evaporative emissions from gasoline (Araizaga et al, 2013;. Guo et al, 2012). The seasonality of concentrations of pollutants will be assessed within this project (winter, spring and summer), and correlated with meteorological data such as speed, wind direction and rain precipitation to interpret the transport and dispersion of pollutants. (AU)