Potencial de formación de ozono de los compuestos orgánicos volátiles emitidos por vehículos y su relación con la composición de las gasolinas
Authors:   , Martínez Reyes Claudia Adriana 
Published: April 2022

Air pollution is the alteration of the composition of the air due to pollutants that at high concentrations can be harmful to health and the environment. Among the most important pollutants are volatile organic compounds (VOC), which are polluting hydrocarbons in a gaseous state at room temperature and together with nitrogen oxides (NOx) are precursors of ozone formation. Each VOC has a different impact on the increase in ozone concentrations and this is directly related to the potential for ozone formation (PFO) is the quantification of an effect of VOCs on ozone formation, which can be determined in different ways, but the most used is the maximum incremental reactivity (MIR). It should be mentioned that the main source of VOCs emissions are vehicles, they are emitted in two ways, evaporative and exhaust. Where depending on the composition of the gasoline will be the emissions. In this thesis, the exhaust emission and evaporative emission profiles of VOCs were determined in gasoline vehicles in Mexico City, as well as the ozone formation potential of each of the VOCs. To determine the exhaust emission profiles of gasoline vehicles, two sampling campaigns were carried out in two tunnels in Mexico City at different times of the year using 6 L stainless steel cans and performing two types of instantaneous and integrated sampling. Environmental samplings were also carried out, that is, in a site where there was very little traffic flow. In turn, three environmental sampling campaigns were carried out as well as in a tunnel of Av. Chapultepec for the determination of carbonyls. Finally, to determine the composition of gasoline, two sampling campaigns were carried out during 2018 and 2019 at gasoline stations in Mexico City, where 500 ml of the two types of Magna and Premium gasoline from different brands of gasoline were purchased. gasoline that are shipped in Mexico City. The gasoline samples that were analyzed were liquid and gasoline vapors. The analyzes of the samples obtained from the exhaust emissions and the gasoline samples were carried out by gas chromatography with a flame ionization detector (FID) and for the analyzes of the carbonyl samples they were carried out by high performance liquid chromatography (HPLC). Tunnel emission compositions have on average 67% paraffins, 17% aromatics, 12% olefins and 4% alkynes. Compared to emission profiles 20 years ago, gasoline has 17% more paraffin in its composition. Regarding the composition of the types of gasoline, Magna presents an average of 47% isoparaffins, 8% olefins, 6% naphthenes, 25% aromatics, 1% oxygenated and 11% paraffins and Premium 27% isoparaffins, 9% olefins, 4% naphthenes, 30% aromatic, 1% oxygenated and 8% paraffin. The compounds that present the highest PFO are ethylene and propylene for exhaust emissions, 1-butene and propane for the environment in Chapultepec and for the environment in Mixcoac it was toluene and 1-butene. The most abundant carbonyl compounds are formaldehyde and acetaldehyde. Formaldehyde emissions inside the Av. Chapultepec tunnel are 3 times higher than those of ambient air.