Particulate matter, mainly its finer fraction, is among the main atmospheric pollutants present in an urban environment. The relationship between the increase in the concentration of this pollutant and the harm to human health is well established. The main sources of particulate matter in urban areas are mobile sources, which includes the exhaust emission from light duty vehicles.
In Brazil since its advent in 2003, there has been great penetration in the market for bi-fuel or "flex" vehicles, which use ethanol, gasoline or their mixtures as fuel. More recently, with the introduction of public policies that led to the adoption of improvements in the energy efficiency of vehicles, the use of direct fuel injection technology (GDI), as a trend in downsizing for improved fuel economy, gained prominence. This technology optimizes the burning process in the combustion chamber of the engines, making their use more efficient. On the other hand, it has the side effect of a higher emission of particulate matter compared to engines that use indirect injection. This higher emission is aggravated by the fact that the particulate matter is extremely fine, precisely the most harmful fraction because it contains a large amount of inhalable particles.
This work measured the emission of particulate matter in light passenger vehicles, characterizing it in terms of emitted mass in "flex" vehicles with port fuel (indirect) injection (PFI), using ethanol and gasoline, and in a gasoline vehicle with direct fuel injection. For the four flex fuel PFI vehicles, the average emission of particulate matter was 1.1 ± 0.3 mg.km-1 for the tests running ethanol, and 1.0 ± 0.3 mg.km-1 for gasohol. For the vehicle equipped with GDI the average emission, with gasohol fuel was 2.8 ± 0.2 mg.km-1.