It has been proved that pollutant gases have a remarkable effect on the amount of total ozone measurements by the Dobson instrument. Among these gases SO2 and NO2 are the most influential pollutants on the ozone and have attracted the attention of scientists.
In this study we make a general survey of the total ozone in the 4 year period, 2002-2005 measured in the Institute of Geophysics of the University of Tehran by the Dobson instrument D109.
A correlational study has also been made using SO2 pollutant values and unrefined total ozone data. The results show that the SO2 makes a fluctuation on the total ozone magnitude and this varies between 0.2% -1.4% in winter and 0.1% - 0.7% in summer. It has also been found that Maximum variability of ozone value happens in winter and early spring. The Maximum value in the spring is experiencing a moderate growth. The largest value of monthly averaged total ozone happened in 2005 and the least value is for 2003 in our data.
A comparative study between the Dobson unit and satellite data reveals that the differences between these two groups of data have decreased in recent years.