Investigating the Complexities of VOC Sources in Mexico City in the Years 2016-2022

Volatile organic compounds (VOCs) are major ingredients of photochemical smog. It is essential to know the spatial and temporal variation of VOC emissions. In this study, we used the Positive Matrix Factorization (PMF) model for VOC source apportionment in Mexico City. We first analyzed a data set collected during the ozone season from March-May 2016. It includes 33 VOCs, nitrogen oxide (NO), nitrogen dioxide (NO2), the sum of nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2) and particle matter with a diameter < 1 mu m (PM1). Another PMF analysis focused only on VOC data obtained in the month of May between the years 2016, 2017, 2018, 2021, and 2022 to gain insights into interannual variations. While the use of fossil fuel through combustion and evaporation continues to be major fraction in Mexico City, additional sources could be identified. Apart from biogenic sources which become more important closer to the end of the ozone season, a second natural emission factor termed "geogenic", was identified. Overall, anthropogenic sources range between 80-90%. Diurnal plots and bivariate plots show the relative importance of these emission source factors on different temporal and spatial scales, which can be applied in emission control policies for Mexico City.