Start Over

Ozone weekend effect in cities: Deep insights for urban air pollution control.

Authors :: Sicard P
Paoletti E
Agathokleous E
Araminienė V
Proietti C
Coulibaly F
De Marco A
Source :: Environmental research [Environ Res] 2020 Dec; Vol. 191, pp. 110193. Date of Electronic Publication: 2020 Sep 11.
Publication Year :: 2020
Abstract: Studying weekend-weekday variation in ground-level ozone (O <subscript>3</subscript> ) allows one to better understand O <subscript>3</subscript> formation conditions, with a potential for developing effective strategies for O <subscript>3</subscript> control. Reducing inappropriately the O <subscript>3</subscript> precursors emissions can either produce no reduction or increase surface O <subscript>3</subscript> concentrations. This paper analyzes the weekend-weekday differences of O <subscript>3</subscript> at 300 rural and 808 urban background stations worldwide from 2005 to 2014, in order to investigate the O <subscript>3</subscript> weekend effect over time and assess the effectiveness of the precursors emissions control policies for reducing O <subscript>3</subscript> levels. Data were analyzed with the non-parametric Mann-Kendall test and Theil-Sen estimator. Rural sites typically did not experience a weekend-weekday effect. In all urban stations, the mean O <subscript>3</subscript> concentration on the weekend was 12% higher than on weekdays. Between 2005 and 2014, the annual mean of daily O <subscript>3</subscript> concentrations increased at 74% of urban sites worldwide (+ 0.41 ppb year <superscript>-1</superscript> ) and decreased in the United Kingdom (- 0.18 ppb year <superscript>-1</superscript> ). Over this time period, emissions of O <subscript>3</subscript> precursors declined significantly. However, a greater decline in nitrogen oxides (NO <subscript>x</subscript> ) emissions caused an increase in Volatile Organic Compounds (VOCs) to NO <subscript>x</subscript> ratios leading to O <subscript>3</subscript> formation. In France, South Korea and the United Kingdom, most urban stations showed a significant upward trend (+ 1.15% per year) for O <subscript>3</subscript> weekend effect. Conversely, in Canada, Germany, Japan, Italy and the United States, the O <subscript>3</subscript> weekend effect showed a significant downward trend (- 0.26% per year). Further or inappropriate control of anthropogenic emissions in Canada, Southern Europe, Japan, South Korea and the United States might result in increased daily O <subscript>3</subscript> levels in urban areas.<br /> (Copyright © 2020 Elsevier Inc. All rights reserved.)