Air Quality Assessment Before and During COVID-۱۹ Using Sentinel-۵P Satellite and Ground Station Data in Ahvaz, Bushehr, and Bandar Abbas

Introduction: The current study investigated temporal variations in six air pollutants: PM۲.۵, PM۱۰, SO۲, NO۳, O۳, CO in the cities of Ahvaz, Bandar Abbas, and Bushehr during ۲۰۱۸–۲۰۲۲, with a focus on the pre- and during-COVID-۱۹ periods. Methods: SO۲, NO۲, CO, and O۳ data were obtained from the TROPOMI sensor onboard Sentinel-۵P (۷ × ۷ km resolution) using Google Earth Engine (GEE). PM۲.۵ and PM۱۰ concentrations were estimated from Aerosol Optical Depth (AOD) data derived from MODIS MCD۱۹A۲ (۱ km resolution) using a regression model calibrated with ground-based monitoring data. Records with > ۳۰% cloud cover or missing values were excluded, and monthly and annual means were calculated. Satellite observations were bias-corrected via linear regression against ground-based data and downscaled using bilinear interpolation. Inter-city comparisons were conducted using independent t-tests, while pre- vs. during-pandemic differences were assessed using paired t-tests. Results: Ahvaz recorded the highest mean concentrations of PM۲.۵, PM۱۰, SO۲, and CO. In most cases, pollutant concentrations were higher before the COVID-۱۹ pandemic, particularly for PM۲.۵ and PM۱۰ in Ahvaz and Bushehr (P < ۰.۰۵). Correlations between satellite-derived and ground-based measurements of PM۲.۵ and PM۱۰ were strong and statistically significant in Ahvaz and Bushehr, but weak or non-significant for SO۲, NO۲, and O۳. Conclusion: The integration of satellite observations with ground-based monitoring systems provides a reliable and cost-efficient approach to air quality assessment. Reductions in certain pollutants, especially particulate matter, were associated with decreased industrial activity and transportation during the pandemic.

Keywords:

Air Quality , Sentinel-۵ satellite , Air Pollutants , COVID-۱۹