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

Abstract

Ozone concentrations have been increasing in the Guadalajara Metropolitan Area (GMA) in Mexico. To help devise efficient mitigation measures, we investigated the ozone formation regime by a chemical transport model (CTM) system WRF-CMAQ. The CTM system was validated by field measurement data of ground-level volatile organic compounds (VOC) and vertical profiles of ozone in GMA as well as in the Mexico City Metropolitan Area (MCMA). By conducting CTM simulations with modified emission rates of VOC and nitrogen oxides (NO x ), the ozone formation regime in GMA was found to lie between VOC-sensitive and NO x -sensitive regimes. The result is consistent with the relatively large VOC/NO x emission ratio in GMA compared to that in MCMA where the ozone formation regime is in the VOC-sensitive regime.

Increasing Weekend Effect in Ground-Level O3 in Metropolitan Areas of Mexico during 1988–2016

“…However, within the MCMA and GMA, we observed increases in the occurrence and magnitude of the WE that have led to increasing breaches to the 1 h O 3 official standard during weekends after 2014 and 2008, respectively. Although control strategies have been effective in reducing O 3 precursor emissions simultaneously, larger decreases in VOC emissions in the VOC-sensitive environments existing at the MCMA and GMA resulted in the spread and increase of the WE magnitude [36]. These increases are consistent with those reported in California during the 1990s in VOC-sensitive regions where large reductions in VOC emissions increased the WE in some regions [13].…”

“…The three MAs studied here have particular tropospheric photochemical environments associated to differences in local precursor emissions sources and meteorology [24,35,36]. Overall, the WE occurrence in ground-level O 3 has been defined in Equation (1) as the existence of higher daytime averages (06:00-18:00 CDT) for Sat-Sun than for Tue-Thu [12,31].…”

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

“…This also makes evident that increasing upwind industrial emissions have offset reductions in emissions from on-road sources as revealed by the decline in NO x evident at OBI. Sierra et al (2013), whereas Kanda et al (2016) reported that in the GMA the O 3 production lies in the region between VOC and NO x sensitivity. Therefore, it can be suggested that simultaneous decreases in NO x and VOC emissions on weekends in the GMA and MMA explain the similar behaviour in O 3 and O x in the MCMA.…”

“…Control measures have been designed based on NAEI and local emissions inventory data, which possess significant uncertainties (Arriaga-Colina et al, 2004;Velasco et al, 2007;Kanda et al, 2016). However, despite these uncertainties, the emissions control strategies have helped to reduce O 3 levels within the MCMA since 1991-1992(ProAire-MCMA, 2001).…”

“…By contrast, growing industrial emissions within the MMA must be subject to stringent controls to abate O 3 levels. In the GMA, where the industrial activity is lower than in the MCMA and MMA (Kanda et al, 2016), the policies introduced on a national scale for controlling on-road source emissions have resulted in the decrease in NO x emissions and in the stabilisation of O 3 levels. The results presented here demonstrate the merits of the assessment and analysis of long-term O 3 levels, which can be used by environmental authorities to revise and to redesign programs and policies to improve air quality.…”