Study of Spatio-temporal Variations of Air Pollution in Tehran Using TROPOMI and OMI Data Products

In this study spatio-temporal variations of three air pollutants including CO۱, NO۲ and SO۲ in Tehran are investigated using data products OMI and TROPOMI sensors based on Google Earth Engine platform. Spatial distribution maps derived from TROPOMI data products show that, for the period of ۲۰۱۹-۲۰۲۱, mean levels of CO۱, NO۲ and SO۲ in Tehran are estimated at about ۰.۰۳۹۱, ۰.۰۰۰۷۴ and ۰.۰۰۰۲۴ mol/m۲, having spatial variations about ۲۵%, ۵۰% and ۲۰۰% respectively over the city. The center of concentration was District #۳, District #۴ and District #۱۵ for CO۱, NO۲ and SO۲ respectively. The concentration of CO۱, and NO۲ are influenced by the geographical situation, as the north-east of the city is surrounded with mountain chains leading to gather air pollutions brought by winds. The most concentration of the integrated pollutants was at the east of Tehran, on the borders of Districts #۶, #۷, #۱۲ and #۱۳. The least pollutions are observed in the northern margins of the city. The OMI derived two-decade time series, show decreasing trends on air pollution which is due to developments in urban transport systems in Tehran after the construction of subway lines. Sub-annual fluctuations include a winter-summer seasonality in all pollutants, and a drop in the new-year vacations. All the pollutants records their annual minimum rates during the new-year vacations, which is characterized with a rapid decrease at the beginning of the vacations. CO۱ and NO۲ show a correlation larger than with SO۲, in both spatial and temporal behaviors. The results show high agreement with in-situ measurements from air control stations.

Keywords:

Air pollution , TROPOMI , OMI , Tehran , CO۱ , NO۲ , SO۲