Porto Alegre, the capital of the State of Rio Grande do Sul
(coordinates 30°S and 51°W), Southern Brazil (Figure 1), has an
area of 497 km² and a population of 1.41 million inhabitants (IBGE,
2014). The city has 0.80 million vehicles, of which 71.2% are
powered by gasoline, 17.3% are powered by diesel, and 11.5% are
motorcycles (IBGE, 2014). At present, gasoline–fueled vehicles
operate on a mixture of gasoline and 20% ethanol, with a sulfur
content of 50 ppm (PETROBRAS, 2014). The diesel, currently used,
contains 500 ppm of sulfur with addition of 5% biodiesel (Mattiuzi
et al., 2012).