Introduction: Action! On Reframing Postcolonial Patrimony
This introductory essay begins with the premise that, in postcolonial studies, the matter of patrimony has figured only implicitly or peripherally. What happens, then, when it moves to the center of postcolonial critique and activism? How does the task of
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Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
Ozone over Mexico City during the COVID-19 pandemic Oscar Peralta a,⁎, Abraham Ortínez-Alvarez b,c, Ricardo Torres-Jardón a, Manuel Suárez-Lastra d, Telma Castro a, Luis Gerardo Ruíz-Suárez a,c a
Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Circuito exterior s/n, Ciudad Universitaria, 04510, Coyoacán, Mexico City, Mexico Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Circuito exterior s/n, Ciudad Universitaria, 04510, Coyoacán, Mexico City, Mexico Instituto Nacional de Ecología y Cambio Climático, Blvd. Adolfo Ruíz Cortines 4209, Jardines en la Montaña, 14210, Coyoacan, Mexico City, Mexico d Instituto de Geografía, Universidad Nacional Autónoma de México, Circuito exterior s/n, Ciudad Universitaria, 04510, Coyoacán, Mexico City, Mexico b c
H I G H L I G H T S
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• Ozone precursor in Mexico City decreased on the lockdown of the COVID19 pandemic, but its concentration remains the same. • Satellite data for March – May 2019 and 2020, and surface air quality measurements show similar results. • Reductions in NOx were so drastic that O3 formation pass from a VOC sensitive region to a transition-NOx region.
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Article history: Received 28 May 2020 Received in revised form 6 October 2020 Accepted 12 October 2020 Available online xxxx Editor: Jianmin Chen Keywords: COVID-19 Ozone Mexico City metropolitan area Pollutant emissions
a b s t r a c t During the COVID-19 pandemic lockdown, emissions of primary criteria pollutants in the Mexico City Metropolitan Area (MCMA) were substantially reduced, as in many other cities in the world. Unexpectedly, the daily average ozone concentration profile was practically indistinguishable from that of the past two years for the same time span in the calendar. So, we compared surface meteorology data, CO, NOx and O3 hourly concentrations in the MCMA from the ozone season (from March 1 to May 31) for the years 2018, 2019, and 2020. Also, TROPOMI satellite data on column count of CO, NO2 and HCHO, above a sparse grid of surface points in the MCMA, were also compared for March, April, and May 2020 with those from 2019. Population density used as a background variable to increase understanding of the observed differences allowed us to propose that reductions in NOx were so drastic that ozone formation moved rapidly from a VOC sensitive region towards a NOx sensitive region. The relevance of that unplanned policy provides impacts of contingent short-term emissions control actions during very high pollution episodes. Further analysis of these and other related data concerning VOC speciation and emissions patterns during the coronavirus lockdown may provide guidelines to enhance emission control policies in the post-COVID-19 times to come. © 2020 Elsevier B.V. All rights reserved.
1. Introduction Air pollution makes people more vulnerable to respirator
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