Environmentally persistent free radicals in PM2.5 from a typical Chinese industrial city during COVID-19 lockdown: The unexpected contamination level variation

How does COVID-19 lockdown affect air quality: Evidence from Lanzhou, a large city in Northwest China

“…Besides overall air quality, the effects of the lockdown on various pollutants' concentrations and its sources (such as black carbon and aerosol), and greenhouse gases (such as CO 2 ) have also been estimated in previous studies most of which have detected reductions in their concentrations or emissions during lockdown periods in different countries and non-same lockdowns ( Kalisa and Adams, 2022 ; Liu et al, 2022 ; Zeng and Wang, 2022 ; Lu et al, 2021; Naqvi et al, 2021 ; Shen et al, 2021 ; Srivastava et al, 2021 ; Bao and Zhang, 2020 ; He et al, 2020; Le Quéré et al, 2020 ; Mahato et al, 2020 ; Silver et al, 2020 ; Xu et al, 2020). There are, however, some studies that show that the lockdown did not seem to significantly prevent air pollution, especially caused by nonsignificant-changing SO 2 ( Song et al, 2021 ) and PM 2.5 ( Wang et al, 2024 ; Chen et al, 2021 ), and rising O 3 (Mamtimin et al, 2022; Shen et al, 2021 ; Wang et al, 2021b ). For example, O 3 concentrations increased during the lockdown by 116%, 145% and 37.42% in Wuhan ( Lian et al, 2020 ), Hangzhou ( Wang et al, 2020 ) and Ji'nan ( Li et al, 2022 ) city of China, and by 20–30% in Indian Indo Gangetic plain at night ( Singh et al, 2020 ).…”

Impact of the Covid-19 Lockdown on Air Pollution in an Industrial City in Northeastern China

“…Wang et al, 2020a;Mo et al, 2021;Song et al, 2021;Luo et al, 2022;Q. Ma et al, 2023;L. Wang et al, 2024).…”

“…Several studies have also found non-significant changes or even increases in SO 2 and PM 2.5 accompanied by severe haze events (Z. Chen et al, 2021;Mo et al, 2021;Song et al, 2021;L. Wang et al, 2024).…”