Assessment of NO2 levels as an air pollutant and its statistical modeling using meteorological parameters in Tehran, Iran

In the present study, air quality analyses for NO2 were conducted in Tehran, capital of Iran. The measurements were taken in four different locations to provide average data in the city. The average concentrations were calculated diurnally, monthly and seasonally. Results exhibited that the highest NO2 concentration occurs generally in the early morning and early night, while the least in the afternoon and after mid-night. Monthly NO2 concentrations displayed the highest value in April, while the least in June and July. The seasonal concentrations exhibited the least amounts in summer, while the highest in autumn. Relationships between the air pollutant and some meteorological parameters were also calculated statistically using the daily average data. The wind data (velocity, direction), relative humidity, temperature, sunshine periods, dew point and rainfall were considered as independent variables. The relationships between pollutant concentrations and meteorological parameters were expressed by multiple linear and nonlinear regression equations for both annual and seasonal conditions using SPSS software. RMSE test displayed that the stepwise, among different prediction models, is the best option.