Investigation of changes in air pollutants in major metropolises of Iran using the optical depth of satellite images

Global analysis of particulate matter indicates the fifth highest risk of death in the world due to exposure to PM2.5. The purpose of this study is to analyze the monitoring and study of changes in air pollutants in the metropolises of Tehran, Karaj, Isfahan, Mashhad and Shiraz using a combination of optical depth of satellite images. Methods first, satellite images of MODIS, MISR and SeaWifs sensors were used, and the data of quality control stations of Iranian metropolises and statistical indicators were used for validation. Kendall and Sense slope methods were also used to analyze the trend. The results showed that the annual variability of suspended particles (PM2.5) during the statistical period of 2000-2000 has an increasing trend in all metropolises of Iran. The city of Tehran showed the highest PM2.5, which is more than other metropolises. After that, Karaj and Isfahan showed the maximum PM2.5. Also, the trend value and trend slope of PM2.5 trend is increasing in all metropolises; this value of trend is statistically significant for Tehran at the level of 0.05; So that the Z score of Man-Kendall test for Tehran is 1.998. The lowest value of suspended particles trend in Isfahan metropolis with Z-score of Mann-Kendall test is 0.02. The effects of urban areas and elevation changes show the most spatial variation of the estimated PM2.5. The amount of PM2.5 in all metropolises has a high spatial diversity; the reason for this variability is due to the proximity to the main sources of dust on the one hand and urban and industrial pollutants on the other.