Long-term trends of Nitrogen oxides and surface ozone concentrations in Tehran city, 2002–2011

Background and aim: tropospheric ozone is a problem with multi aspects - hazard to human health, plant, andwelfare and a key factor to climate change, air pollution and atmosphere chemistry, as well. behavior of ozone andnitrogen oxides (no, and no2) concentration is highly complex and variable; therefore, their trends as short andlong-term were significantly attended. most of the studies were carried out on the behavior of pollutantconcentrations in north america, europe, and east asia, but few studies have been conducted in west asia. the aimof this study was to assess daily changes and long-term trend of ozone and nitrogen oxides concentrations intehran city, iran from march 2002 to september 2011.material and methods: data were collected from 18 air quality monitoring stations. the data were sorted as dailymean of 10 years (daily changes) and annual mean for each year (long-term trend). one-sample test was used toassess the statistical significance.results: current findings indicated that changes of ozone, no, and no2 concentrations are dependent from jobshifts and photochemical reactions. annual mean concentrations of ozone and no2 were gradually increased,long-term trend of ozone and no2 concentration indicated. the correlation between long term trend of ozone andno2 was significant (p < 0.05).conclusion: the controlling program was the most important factor in long-term concentration of ozone, andnitrogen oxides, but some problems and difficulties were accounted to perform controlling program.