Reasons for the observed tropospheric ozone weakening over south-western Europe during COVID-19: Strict lockdown versus the new normal

16 Years (2006–2021) of Surface Ozone Measurements in Córdoba (Southern Spain): Trends and the Impact of the COVID-19 Lockdown

“…These results indicate that the strict lockdown mainly impacted the production of O 3 in Córdoba city, while the background values presented similar or even higher values. These results do not agree with those observed in 15 regional background sites in the Iberian Peninsula [ 19 ] since at these sampling sites, the hemispheric regional O 3 background was significantly reduced during the health crisis. This fact, in a general framework of a decrease in anthropogenic emissions over the Iberian Peninsula [ 35 ], and hence, fewer precursors available, pointed to the large variability in O 3 concentrations and the different impact of this lockdown on the sampling stations, according to their location and environment.…”

“…Following the methodology applied in [ 19 ], we have calculated the averages between 22–09 h and 12–18 h for each period to quantify the differences between the background values and local–regional O 3 production. The averages and differences are shown in Table 1 .…”

“…This O 3 time series covers the COVID-19 health crisis, which has been extensively analysed in terms of air quality all around the world [ 17 , 18 ]. In Spain [ 19 ], an analysis was performed on how O 3 concentrations changed during this period at different monitoring stations, although Córdoba city was not considered in the study. Therefore, the present study is also the first analysis describing the impact of this special period on the O 3 concentrations in this city.…”

Spatial characteristics of change trends of air pollutants in Chinese urban areas during 2016–2020: The impact of air pollution controls and the COVID-19 pandemic

“…In addition, Qi et al (2021) pointed out that the rise in ozone during the lockdown period was the combined effect of a substantial increase at night (58%–91%) and a small reduction in the daytime (1%–17%). In contrast, Pey and Cerro (2022) pointed out that the mitigation of regional O 3 pollution during the lockdown over southwestern Europe was related to the reduction in hemispheric background concentrations. A decline in O 3 concentrations was also observed in the Pearl River Delta (China), where O 3 formation rates are under a NO x -limited regime; therefore, the same reduction in NO x would diminish O 3 generation rates ( Wang et al, 2021b ).…”

Seasonal Variations and Effect of COVID-19 Lockdown Restrictions on the Air Quality in the Cities of Kazakhstan

“…The reduction in air pollution due to the decline of economic activities during lockdown was reported by many authors across the world (Mousazadeh et al 2021 ) (Supplementary Material ( SM ); Table SM1 ). The positive effect of COVID-19 lockdown on air quality improvement, mainly reduction of NO 2 and CO concentrations, was observed in some parts of India (Allu et al 2021 ; Bera et al 2021 ; Chelani and Gautam 2021 ; Gopikrishnan et al 2022 ), Italy (Collivignarelli et al 2020 ; Gautam 2020 ), China (Chen et al 2020b ; Gautam 2020 ), Spain (Gautam 2020 ; Tobías et al 2020 ; Pey and Cerro 2022 ), France (Gautam 2020 ), Vietnam (Nguyen et al 2022 ), Russia (Ginzburg et al 2020 ), Canada (Tian et al 2021 ), USA (Liu et al 2021 ), Turkey (Şahin 2020 ) and Malaysia (Ash’aari et al 2020 ). However, the impact of lockdown measures was not uniform across different pollutants and areas.…”