Investigation of Behavior and Trend of Nitrogen Dioxide in Tehran Using OMI Satellite Sensor Measurements

Air pollution is one of the most important problems in the world’s major cities in the last century because it endangers human health and the environment. One of the indicators of air pollution is nitrogen dioxide, which is continuously measured by satellite from space and via ground-based instruments. In this paper, the data for nitrogen dioxide was measured by OMI over Tehran. Wind, surface temperature and horizontal visibility were recorded at Mehrabad Meteorological Station during the period from October 2004 to May 2016 to evaluate the behavior and trends of air pollution. The average amount of nitrogen dioxide during the spring, summer, autumn and winter seasons were 6.99 ×1015, 6.22 ×1015, 16.90 ×1015, and 19.65 ×1015 molec/cm2 with the highest (lowest) value occurring in the winter (summer). Also, the highest (lowest) standard deviation occurred in the winter (summer), which was 14.84 ×1015 (3.73 ×1015). The correlation coefficient of nitrogen dioxide with wind and temperature were -0.04 and -0.59, respectively, which show a greater effect of temperature on nitrogen dioxide changes. Also, the correlation coefficient of nitrogen dioxide with horizontal visibility was -0.20, which indicates a reduction of horizontal visibility with increasing urban pollution in Tehran. The nitrogen dioxide trend was calculated using linear regression after eliminating four, six, and twelve-month periods with 95% confidence. The trend of nitrogen dioxide was 5.76 ×1014 molec/ cm2 per year.