edu.ucar.opensky::articles:6402 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T15:15:40.810162 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d76d5t56 Weekly patterns of México City's surface concentrations of CO, NOx, PM₁₀ and O₃ during 1986 - 2007 2008-09-05T00:00:00Z publication https://n2t.org/ark:/85065/d76d5t56 https://doi.org/10.5194/acp-8-5313-2008 Stephens, Sherry author Madronich, Sasha author Wu, Fei author Olson, J. author Ramos, R. author Retama, A. author Muñoz, R. author UCAR/NCAR - Library publisher Surface pollutant concentrations in México City show a distinct pattern of weekly variations similar to that observed in many other cities of the world. Measurements of the concentrations of carbon monoxide (CO), nitrogen oxides (NOx=NO+NO₂), particulate matter smaller than 10 μm (PM10), and ozone (O₃) collected hourly over 22 years (1986 - 2007) at 39 urban monitoring locations were analyzed. Morning concentrations of CO, NOx, and PM₁₀ are lower on Saturdays and even more so on Sundays, compared to workdays (Monday - Friday), while afternoon O₃ concentrations change minimally and are occasionally even higher. This weekend effect is empirical evidence that photochemical O₃ production is NOx-inhibited, and to the extent that emissions of CO are proportional to those of reactive volatile organic compounds (VOCs), it is VOC-limited, at least in the urban areas for which the monitoring stations are representative. The VOC-limitation has increased in the past decade, due to decreases in the concentrations of CO (and presumably VOCs) and consequent decreases in the CO/NOx and VOC/NOx ratios. Enhancements of photolysis frequencies resulting from smaller weekend aerosol burdens are not negligible, but fall short of being an alternate explanation for the observed weekend effect. The strength of the weekend effect indicates that local radical termination occurs primarily via formation of nitric acid and other NOx-related compounds, some of which (e.g. peroxy acyl nitrates) can contribute to the regional NOx budget. While VOC emission reductions would be most effective in reducing local O₃ production, NOx emission reduction may be more important for controlling regional oxidants. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Authors 2008. This work is distributed under the Creative Commons Attribution 3.0 License. None eng geoscientificInformation