Ozone sensitivity to its precursor emissions in northeastern Mexico for a summer air pollution episode

Abstract

A summer episode was modeled to address the expected response of ambient air O 3 to hypothetical emission control scenarios in northeastern Mexico, and in particular in the Monterrey Metropolitan Area (MMA). This region is of interest because the MMA holds one of the worst air quality problems in the country and levels of air pollutants in the rest of northeastern Mexico are starting to be a concern. The MM5-SMOKE-CMAQ platform was used to conduct the numerical experiments. Twenty-four control scenarios were evaluated, combining the level of emission controls of O 3 precursors (NOx and volatile organic compounds [VOCs]) from 0% to 50%. For the MMA, VOC-only controls result in the best option to reduce O 3 concentrations, though the benefit is limited to the urban core. This same strategy results in negligible benefits for the rest of northeastern Mexico. NOx controls result in an increase in O 3 concentration within the MMA of up to 20 ppbv and a decrease at downwind locations of up to 11 ppbv, with respect to the basecase scenario. Indicator ratios were also used to probe for NOx-sensitive and VOC-sensitive areas. Locations with an important influence of NOx point sources (i.e., Monclova and Nava/Acuña) are quite sensitive to changes in NOx emissions. Border cities in the Rio Bravo/Grande Valley tend to be marginally NOx-sensitive. Overall, the MMA seems to be dominated by a VOC-sensitive regime, while the rest of the region would tend to have a NOx-sensitive response. The results obtained serve to expand the current knowledge on the chemical regimes that dominate this region (VOC-or NOx-sensitive), and thus could help guide public policies related to emission regional control strategies.Implications: Updated information on the expected response of ambient air O 3 to emission changes in northeastern Mexico is presented. Results suggest that emission control strategies for the Monterrey Metropolitan Area should focus on VOC reductions or combined VOC-NOx reductions, while the Lower Rio Bravo/Grande Valley border has a negligible response to the emission scenarios tested. Changes in NOx emissions from Carbon II, a 1,400-MW coal-fired electric utility, would have a nonnegligible transboundary effect.

Diurnal and seasonal variations of carbonyls and their effect on ozone concentrations in the atmosphere of Monterrey, Mexico

“…Therefore, O 3 is more sensitive to the changes in the concentration of carbonyls. Results found with the graphical analysis made during this research agree with those found by Sierra et al (2013), who modeled O 3 sensitivity in relation to the presence of VOCs in the atmosphere of the MMA. The control of the carbonyls is of interest, especially formaldehyde, which accounts for 50% of the total carbonyls.…”

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.…”

“…The large growth rates in O 3 and NO x at SNN and SNB are explained by increasing emissions of O 3 precursors from a growing number of industries and the urban development E of the MMA. The most likely explanation for the O 3 in-crease at OBI is a reduced titration effect from decreasing NO x levels in combination with the non-linear response in O 3 production to decreasing NO x emissions under the VOCsensitive MMA airshed (Sierra et al, 2013;Menchaca-Torre et al, 2015).…”

Use of Combined Observational- and Model-Derived Photochemical Indicators to Assess the O3-NOx-VOC System Sensitivity in Urban Areas

“…This highlights the importance of untangling the O 3 production sensitivity system to introduce effective emission controls, which can lead to an improvement in the air quality within the MMA. To date, only one study has recently assessed the O 3 production sensitivity system within the MMA [19]; a VOC-sensitive regime was observed based on numerical simulations performed with the Community Multi-scale Air Quality (CMAQ) model. However, those results come from a six-day This study presents the assessment of the O3 photochemical production regime within the MMA over a one-year period carried out by combining box-modeling and observational approaches to analyze the behavior of two photochemical indicators.…”

“…Finally, the presence of a weekend effect in the diurnal production of O 3 was tested using an ANOVA analysis for O 3 /NO y ratios during the enhanced photochemical activity period. Data correlations, PCA, CA and ANOVA were carried out using IBM SPSS Statistics software v. 19.0 (IBM, Armonk, NY, USA) for Windows.…”