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Analyses of the Ozone Weekend Effect in Tokyo, Japan: Regime of Oxidant (O3 + NO2) Production

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Volume: 12 | Issue: 2 | Pages: 161-168
DOI: 10.4209/aaqr.2011.07.0102
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Yasuhiro Sadanaga , Mitsuyo Sengen, Norimichi Takenaka, Hiroshi Bandow

  • Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan


The ozone weekend effect (OWE) in Tokyo, the capital of Japan, was analyzed from April 2005 to March 2008 with respect to the photochemical ozone production, focusing on the ozone production regime. For most periods, the OWE was confirmed in the wintertime as well as in the summertime. The comparison of Ox ([Ox] = [O3] + [NO2] – 0.1[NOx]) concentrations between weekdays and weekends suggests that there are some periods when the photochemical ozone production on the weekends could be larger than on the weekdays (defined as the POP group). We compared NOx (the sum of NO and NO2) and Ox concentrations on the weekends with those on the weekdays for several distinct ranges of the non-methane hydrocarbons (NMHCs) concentrations, and NOx and Ox concentrations on the weekends are significantly lower and higher than those on the weekdays in the POP group. Therefore, the ozone production regime would be NMHC-limited in the POP group. The ozone production regime in the summertime in Tokyo could be in the boundary area between NMHC- and NOx-limited in terms of the NMHCs/NOx ratios. The NMHCs/NOx ratios in the NMHC-limited regime are smaller than those in the NOx-limited regime in general. However, the NMHCs/NOx ratios in the POP group were not smaller than those in the non-POP group.


Ozone weekend effect Ozone production regime Nitrogen oxides Non-methane hydrocarbons

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