Impact of COVID-19 Event on the Air Quality in Iran

Abstract

This study examines changes in air quality during Iran’s COVID-19 lockdown (21 March–21 April 2020 vs same period 2019) using data from 12 ground stations and satellite observations. In Tehran, primary pollutants SO2 (−5–28%), NO2 (−1–33%), CO (−5–41%), and PM10 (−1.4–30%) decreased, while O3 (↑0.5–103%) and PM2.5 (↑2–50%) increased. Nationally, SO2 and NO2 decreased, but aerosol optical depth (AOD) increased. Unfavorable meteorology—including reduced planetary boundary layer height and rainfall—limited dispersion, yet air quality improved due to reduced emissions.