An investigation of air pollution in the Tehran metropolitan area between 1992–2000 indicated that there are significant amounts of nitrate ion (NO3), over 30 kg/ha/year, deposited as wet deposition, compared to 13 kg/ha/year in the Chitgar Parkland near the Tehran metropolitan area. The amount of NO3 in warm seasons is twofold that of cold seasons (see Fig. 1), and there was a significant difference between cold and warm seasons (Table 1). Annual wet deposition of ammonia (NH3) was 10 kg/ha/year in the Chitgar Parkland[1].