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The SARS-CoV-2 (Severe Acute Respiratory Syndrome-related Coronavirus 2) and its concomitant disease COVID-19 (Coronavirus Disease 2019), discovered at the end of December 2019, have spread around the world, becoming a global public health problem. To prevent the spread of COVID-19, the Chinese government took strict lockdown measures in early 2020 in many cities. The purpose of this study was to evaluate changes in air quality in Shanghai, China's most populous city during the lockdown. Lockdown measures led to a decrease in anthropogenic activity and a concomitant reduction in air pollutant emissions, which led to a temporary improvement in air quality. Mean daily concentrations of PM2.5, PM10, SO2 and NO2 during a 2-week portion of the lockdown period (24 January–6 February) were respectively reduced by −19.2%, −44.7%, −21.5% and −33.6% compared to the same period in 2019. Even with the decrease in PM2.5 and PM10 concentrations, they were still more than four times higher than the World Health Organization standards (10 μg/m3 and 20 μg/m3, respectively). This study provides data useful for evaluating existing environmental policy, as it showed how the control of pollution sources can affect air quality. [ABSTRACT FROM AUTHOR]

From the beginning of May 2023 to the end of August 2023, the Northern Hemisphere experienced significant wildfire activity with the most widespread fires occurring in Canada. Forest fires in Canada destroyed more than 15.6 million hectares of forests. These wildfires worsened air quality across the region and other parts of the world. The smoke reached southern Europe by the end of June 2023. To better understand the consequences of such forest fires far from the site of origin, aerosol optical, microphysical and radiative properties were analyzed during this event for southern Europe using data from the Visible Infrared Imaging Radiometer Suite (VIIRS), TROPOspheric Monitoring Instrument (TROPOMI), and Aerosol Robotic Network (AERONET). TROPOMI aerosol index (AI) and the carbon monoxide (CO) product confirm that the smoke originated directly from these forest fires. AERONET data from the El Arenosillo site in southern Spain showed maximum aerosol optical depth (AOD) values on June 27 reached 2.36. Data on Angstrom Exponent (AE), aerosol volume size distribution (VSD), single scattering albedo (SSA), fine mode fraction (FMF), volume particle concentration, effective radius (R Eff ), absorption AOD (AAOD), extinction AE (EAE) and absorption AE (AAE) showed that fine-mode particles with carbonaceous aerosols contribution predominated in the atmosphere above the El Arenosillo site. Direct aerosol radiative forcing (DARF) at the top (DARF TOA ) and bottom of atmosphere (DARF BOA ) were -103.1 and -198.93 Wm -2 , respectively. The atmospheric aerosol radiative forcing (DARF ATM ) was found to be 95.83 Wm -2 and with a heating rate 2.69 K day -1 , which indicates the resulting warming of the atmosphere., Competing Interests: Declaration of Competing Interest ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:, (Copyright © 2024. Published by Elsevier Inc.)