Trend study of three main air pollutants of Tehran city by Sentinel-5

During recent years, by expanding cities, air pollution is one of the most important problem made by humans. Tehran, as the capital of Iran, is expanding gradually and its population is rising day by day. Therefore, the increase of human activities causes many problems, such as air pollution in this area. In this study, Sentinel-5 data for Tehran city are used from last month of 2018 to present, and collected by Google Earth Engine. Three main pollutants have been studied, such as aerosol, ozone and CO. Different statistics of each pollutant are calculated, and temporal evolutions are investigated using variance analysis and linear regressions. The medians and the interquartile ranges are -0.555 and, 1.248 for aerosols, 0.131 and 0.015 mol m^-2 for ozone, and 0.037, and 0.011 for CO mol m^-2. The annual evolution shows that aerosols amounts are higher in summer against the winter months, whereas ozone is high in March and low in October. CO amounts are minimum in summer and maximum at the end of fall and winter, with high variability. The aerosol trend is increasing, whereas statistics have shown a decreasing trend for ozone, with both trends being statistically significant at a 95% confidence level. However, the CO trend is totally stable. These results can be used to detect pollution events, and to protect human life in future. Moreover, these parameters can be studied in other areas, especially the industrial ones, to understand the most polluted sites and periods.