Observed trends in ground-level O3 in Monterrey, Mexico, during 1993–2014: comparison with Mexico City and Guadalajara

• Published in: Atmospheric chemistry and physics 2017-07, Vol.17 (14), p.9163-9185
• Main Authors: Hernández Paniagua, Iván Y, Clemitshaw, Kevin C, Mendoza, Alberto
• Format: Article
• Language: English
• Subjects: Air pollution; Annual variations; Area; Diurnal; Emissions; Industrial areas; Metropolitan areas; Mixing ratio; Nitrogen dioxide; Oxygen; Photolysis; Pollutants; Polymethyl methacrylate; Production increases; Quality; Site location; Spring; Spring (season); Suburban areas; Trends; VOCs; Volatile organic compounds; Wind; Wind power
• ISSN: 1680-7316; 1680-7324
• DOI: 10.5194/acp-17-9163-2017

Here, we present an assessment of long-term trends in O3 and odd oxygen (O3 + NO2) at the industrial Monterrey metropolitan area (MMA) in NE Mexico. Diurnal amplitudes in Ox (AVd) are used as a proxy for net O3 production, which is influenced by the NO2 photolysis rate. No significant differences in the AVd are observed between weekends and weekdays, although the largest AVd values are observed at sites downwind of industrial areas. The highest O3 mixing ratios are observed in spring, with minimum values in winter. The largest annual variations in O3 are typically observed downwind of the MMA, with the lowest variations generally recorded in highly populated areas and close to industrial areas. A wind sector analysis of mixing ratios of O3 precursors revealed that the dominant sources of emissions are located in the industrial regions within the MMA and surrounding area. Significant increasing trends in O3 in spring, summer, and autumn are observed depending on site location, with trends in annual averages ranging between 0.19 and 0.33 ppb yr−1. Overall, from 1993 to 2014, within the MMA, O3 has increased at an average rate of 0.22 ppb yr−1 (p