Effect of COVID-19 lockdown on ambient air quality

The aim of this study was to evaluate the impact of pandemic-related lockdown on Turkey's air quality throughout time and space. For this purpose, statistical techniques were used to assess daily particulate matter (PM₁₀), sulfur dioxide (SO₂), nitrogen oxides and nitrogen dioxide (NO_x and NO₂), ozone (O₃), and carbon monoxide (CO). The study's findings showed that, while the lockdown improved air quality in terms of air pollutant emissions, the most notable reduction was in NO₂ and NO_x emissions. When comparing the months prior to the pandemic (November 2019 to January 2020) with the months during the pandemic (November 2020 to January 2021), the declines in NO₂ were 20%, 3%, and 0.5%, respectively. NO_x emissions decreased by an average of 19% and 5% in November and December, respectively, and increased by an average of 16% in January during the pandemic. When the data for the 33 days of lockdown were compared to the data for the same 33 days the previous year, significant differences were determined at several Clean Air Centers, which were two for PM₁₀, two for SO₂, seven for NO_x, four for NO₂, two for CO, and three for O₃, respectively. In this study, pollutant concentrations were found in the following ranges from November 2019 to January 2021: PM₁₀: 3–208 µg m^–3, SO₂: 1–56 µg m^–3, NO_x: 6–600 µg m^–3, NO₂: 4–155 µg m^–3, CO: 1–3921 µg m^–3, and O₃: 2–119 µg m^–3. There were days that exceeded the limit values for PM₁₀.