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Measurement of Aerosols Optical Thickness of the Atmosphere using the GLOBE Handheld Sun Photometer

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The vanishing ozone weekday/weekend effect.

George T Wolff¹, Dennis F Kahlbaum, Jon M Heuss

¹Air Improvement Resource, Inc., 47298 Sunnybrook Lane, Suite 103, Novi, MI, 48374, USA. gwolff@airimprovement.com

Journal of the Air & Waste Management Association (1995)

|April 6, 2013

Summary

Weekend ozone levels were once higher than weekdays in many cities due to lower precursor emissions. Recent emission controls have largely eliminated this ozone phenomenon, with most areas showing little weekend/weekday difference.

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Area of Science:

Environmental Science
Atmospheric Chemistry
Air Quality Research

Background:

Historically, urban areas exhibited higher weekend ozone (O3) concentrations despite lower precursor emissions.
This weekend ozone phenomenon was prevalent in the late 1990s, particularly in the Northeast, Midwest, and coastal California.

Purpose of the Study:

To analyze the changes in weekday/weekend ozone concentration differences from the late 1990s to the late 2000s.
To investigate the impact of evolving ozone precursor emission trends on observed ozone levels.

Main Methods:

National analysis of weekday/weekend ozone (O3) data from 1997-1999 and 2008-2010.
Comparison of 8-hr maximum O3 concentrations and other O3 metrics across different time periods.
Examination of trends in ozone precursor emissions, specifically nitrogen oxides (NOx) and volatile organic compounds (VOCs).

Main Results:

The phenomenon of higher weekend O3 concentrations significantly declined between 1997-1999 and 2008-2010.
The percentage of sites with higher weekend O3 dropped from ~35% to <5%, while sites with higher weekday O3 increased from 3% to ~27%.
Increased VOC/NOx emission ratios, driven by greater NOx reductions, appear to be the primary reason for this shift.

Conclusions:

Weekend emission reductions, often linked to motor vehicle use, served as an inadvertent test of ozone control strategies.
Implemented emission controls have largely resolved the issue of higher weekend ozone in most urban areas.
Current emission control strategies suggest that weekend emission reductions have minimal impact on ozone concentrations in most locations.