Ozone responses to reduced precursor emissions: A modeling analysis on how attainable goals can improve air quality in the Mexico City Metropolitan Area

Jairo Vazquez Santiago; Monica Jaimes Palomera; Cintia Resendiz Martinez; Andres Hernandez Matamoros; Hiroo Hata; Kazuya Inoue; Kenichi Tonokura

doi:10.1016/j.scitotenv.2023.169180

Ozone responses to reduced precursor emissions: A modeling analysis on how attainable goals can improve air quality in the Mexico City Metropolitan Area

Sci Total Environ. 2024 Feb 20:912:169180. doi: 10.1016/j.scitotenv.2023.169180. Epub 2023 Dec 9.

Authors

Jairo Vazquez Santiago¹, Monica Jaimes Palomera², Cintia Resendiz Martinez², Andres Hernandez Matamoros³, Hiroo Hata⁴, Kazuya Inoue⁴, Kenichi Tonokura⁵

Affiliations

¹ Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan; Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan.
² Secretaría del Medio Ambiente de la Ciudad de México, Ciudad de México 06068, Mexico.
³ Department of Ocean Technology, Policy and Environment, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
⁴ Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan.
⁵ Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan. Electronic address: tonokura@k.u-tokyo.ac.jp.

PMID: 38072281
DOI: 10.1016/j.scitotenv.2023.169180

Abstract

High tropospheric ozone (O₃) concentrations prevent the improvement of the air quality in the Mexico City Metropolitan Area (MCMA). Although the problem has improved considerably since the 1990s, a rebound in O₃ levels in recent years has raised concerns about the deteriorating air quality. The nonlinear relationship between O₃ formation and the emissions of its main precursors, i.e., volatile organic compounds (VOCs) and nitrogen oxides (NO_x), is a challenge when measures are enacted for effective mitigation of the O₃ problem. This study evaluated the reduction in precursors, VOCs and NO_x, using an up-to-date regional air quality model (HERMES-Mex-WRF-CMAQ). For evaluating realizable scenarios, the decline in VOC achieved in Japan after policy implementation was the targeted VOC reduction (40 % from area sources), and the NO_x reduction observed in the MCMA during the COVID-19 pandemic was the targeted NO_x reduction (40 % from mobile sources). The analysis evaluated the O₃ responses to changes in a single precursor and a combination of both during a period of high O₃ concentrations (April 2019). The results showed that 40 % reduction in VOC emissions would decrease the O₃ 8-h maximum concentrations by 16 %. However, 40 % reduction in NO_x emissions would increase O₃ by >15 %. The simultaneous reduction of both precursors did not significantly affect O₃ levels. The diagnosis of ozone sensitivity using the H₂O₂/HNO₃ ratios reinforced the simulation findings, indicating that VOC emissions limited ozone formation in most MCMA areas. As the simulated scenarios were based on factual case studies, our research offers insights into the realistic aims of MCMA policies to reduce O₃ levels.

Keywords: Air quality models; Ozone pollution; Ozone sensitivity; Precursor emissions.