Investigation of the spatiotemporal patterns of air quality over the metropolitan area of Tehran, using TROPOMI and OMI data

Abstract

AbstractAir quality has been one of the main concerns among Tehran residents for at least two decades. In this study, we investigated air quality in the metropolitan area of Tehran utilizing TROPOMI and OMI data based on the Google Earth Engine platform. Long-term analysis indicated slight negative trends in NO2, SO2, and HCHO over the last two decades, which are due to the development of urban transportation systems. Air quality parameters were classified based on spatiotemporal similarities. Urban pollutants include CO1, NO2, and HCHO, which were concentrated over the eastern part of Tehran and decreased radially towards the city border. Among the pollutants, CO1 showed a dependency with altitude. SO2 was controlled by both urban vehicles and nonurban industrial activities. SO2 was thus classified as an urban-industrial pollutant. The exterior parameters almost entirely controlled by external factors include O3, aerosols, and clouds. The spatial variations of the pollutants highly differed from a fraction to several times. All pollutants exhibited seasonality associated with fuel consumption and air conditions. However, the seasonality in the exterior parameters was associated with regional air masses. The Iranian New Year holiday significantly impacts air pollution. NO2, CO1, and SO2 experienced their annual minimum levels during this holiday period. COVID-19–related closures also led to negative trends in NO2, CO1, and SO2 after March 2020. However, the exterior parameters were not affected by these events. The results agreed with in situ measurements. As the final objective, we aimed to support urban management to reduce atmospheric pollution in Tehran.