Status and Prediction of Nitrogen Oxides in the Air of Shiraz City, Iran

In the present study, air quality analyses for Nitrogen oxides (NOX) were conducted in Shiraz, a city in the south of Iran. The measurements were taken over the period from 2011 through 2012 in two different locations to prepare average data in the city. The average concentrations were calculated every twenty-four hours, each month and each season. The results showed that the highest concentration of NOX occurred generally in the morning while the least concentration was found at mid-night. Monthly concentrations of NOX showed that the highest value occurred in December, while the least value was recorded in September. The seasonal concentrations showed that the least amounts were in summer, while the highest amounts were found in winter. Unfortunately, most of the time, the concentration of the NOX showed higher levels than the primary standards of Nitrogen dioxide (0.021 ppm), protecting human health. Relations between air pollutants and some meteorological parameters were calculated statistically using the daily average data. The wind data (velocity, direction), relative humidity, temperature, sunshine periods, evaporation, dew point and rainfall were considered as independent variables. The relationships between the concentration of pollutants and meteorological parameters were expressed by multiple linear regression equations for both annual and seasonal conditions using the SPSS software. The RMSE test showed that among the different prediction models, the stepwise model is the best option.