“…Furthermore, O 3 in all provinces showed an increasing trend during 2016–2019, while O 3 in 26 out of 31 provinces showed a reduction in 2020. Most studies reported either minimal to no reduction or even an increase in surface O 3 concentrations during the lockdown period ( Adam et al, 2021 ), and the O 3 increase during the lockdown period was attributed to meteorological conditions and weak titration effects ( Adam et al, 2021 ; Su et al, 2021 ). 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%).…”