Volatile organic compounds in the atmosphere of Mexico City

Abstract

26The Mexico City Metropolitan Area (MCMA) is one of the most polluted megacities in North 27 America. Therefore, it is an excellent benchmark city to understand atmospheric chemistry and 28 to implement pilot countermeasures. Air quality in the MCMA is not within acceptable levels, 29 mainly due to high ground levels of ozone (O 3 ). Tropospheric O 3 is a secondary pollutant formed 30 from the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides and 31 sunlight. To gain a better understanding of O 3 formation in megacities, evaluate the effectiveness 32 of already-implemented countermeasures, and identify new cost-effective alternatives to reduce 33 tropospheric O 3 concentrations, researchers and environmental authorities require updated 34 concentrations for a broader range of VOCs. Moreover, in an effort to protect human health and 35 the environment, it is important to understand which VOCs exceed reference safe values or most 36 contribute to O 3 formation, as well as to identify the most probable emission sources of those 37 VOCs. In this work, 64 VOCs, including 36 toxic VOCs, were measured at four sites in the 38 MCMA during 2011-2012. VOCs related to liquefied petroleum gas leakages exhibited the 39 highest concentrations. Toxic VOCs with the highest average concentrations were acetone and 40 ethanol. The toxic VOC benzene represented the highest risk to Mexican citizens, and toluene 41 contributed the most to O 3 formation. Correlation analysis indicated that the measured VOCs 42 come from vehicular emissions and solvent-related industrial sources. 43 44 Keywords: Volatile organic compound, Toxic volatile organic compound, Ozone, Ozone 45 formation potential 46 47 48 CAPSULE ABSTRACT 49 VOC measurements revealed that compounds related to liquefied petroleum gas leakages are the 50 most abundant, the toxic VOC benzene represents the highest risk to citizens, and toluene is the 51 greatest VOC contributor to O 3 formation in Mexico City. 52 53 5

Comparison of Ozone Production Regimes between Two Mexican Cities: Guadalajara and Mexico City

“…It is noteworthy that SO 2 emitted from an active volcano in the southeast and an industrial complex in the north interfered the ozonesonde measurement in MCMA [16]. The VOC analysis by GC with flame ionization detector (FID) and mass spectrometer (MS) confirmed previous findings such as that a large proportion of VOC was LPG related to domestic consumption and that more reactive and toxic species than the LPG components could be attributed to vehicular transport and solvent-related industries [18].…”

“…The MCMA campaign conducted in March 2012 has already been reported for ozonesonde [16,17] and VOC analysis [18]. The O 3 -concentration profiles obtained twice daily in the morning and afternoon reflected the meteorological condition on the observation days [17].…”

Observed trends in ground-level O<sub>3</sub> in Monterrey, Mexico, during 1993–2014: comparison with Mexico City and Guadalajara

“…S1) (SEMARNAT, 2006(SEMARNAT, , 2011(SEMARNAT, , 2014. However, as for NO x , NEI trends in VOCs disagree with existing reports for average VOC decreases within the MCMA (Arriaga-colina et al, 2004;Garzón et al, 2015).…”

“…New road corridors were designed for improving the intracity transport and the public transport fleet was renewed (ProAire-MCMA, 2001). For industrial sources, the switch from fuel oil to LP gas fuel, relocation of highly polluting industries away from the MCMA, and im- Garzón et al (2015) is consistent with a reduction in light alkane and aromatic levels during the morning rush hour reported by Jaimes-Palomera et al (2016). Continuous measurements of VOCs have been recently introduced by the MCMA government, which precludes an assessment of VOC long-term trends.…”

“…S1 and 10). For VOCs, the NAEI and the MCMA inventories oppose measured trends in VOCs during 1993(Arriaga-Colina et al, 2004Garzón et al, 2015). This can be explained by underestimates of VOC emissions within the MCMA of a factor of 2-3 (Arriaga- Colina et al, 2004;Velasco et al, 2007).…”