Air Quality Variations and Influence of COVID‑19 Lockdown Restrictions on it in Tabriz, Iran

The severe lockdown imposed to prevent the spread of COVID-19 decreased the emissions of air pollutants in large cities. A comparative approach was adopted to analyze the effect of the COVID-19 lockdown on ambient air pollution concentrations and the impacts of meteorological parameters on them using data from air quality monitoring stations (AQMS) in Tabriz, Iran. Air quality improvement was significant for all pollutants, except for O₃, in the first phase of the lockdown compared to other phases. The lockdown (restricted social contact, closing of shops, schools, universities, restaurants, and many administrative centers and companies, etc.) temporarily reduced air pollutants. Comparing meteorological parameters between lockdown periods and the same period in previous years showed no statistically significant variations (P-value < 0.05). Therefore, the meteorological parameters did not intervene in reducing air pollutants during the lockdown. The effects of lockdown on the concentration of air pollutants could provide a special way to understand the extent of quarantine compliance by citizens, evaluate additional air quality policies, and assess the impacts of reducing various emission sources.