Gaseous air pollutants dispersion emitted from point and line sources by coupling WRF-AERMOD models (Case study: Lowshan, Guilan Province, Iran)

The cement factories in urban areas can affect the air quality of cities due to the variety of pollutants emitted from cement production processes. In the present study, the impacts of the Khazar cement factory and two transportation axes between Guilan and Qazvin provinces were investigated on the air quality of Lowshan in Guilan Province, Iran in 2019. Due to the lack of suitable meteorological data for dispersion modeling, the WRF model was used to predict the meteorological parameters. The pollutants dispersion modeling was conducted by AERMOD software and the accuracy of results was confirmed by field measurements of NO2 obtained by passive samplers. The CO and NO2 dispersion modeling results showed that the air quality of Lowshan is in an acceptable situation compared to the ambient air quality standards. So that, the maximum one-hour concentration of NO2 in most residential areas was lower than the ambient standard, and only in small parts of the areas close to line sources, the concentration value was close to the standard limits. The maximum value of annually-averaged concentration of NO2 and the maximum one-hour concentration of CO were 17 ppb and 2.5 ppm, respectively, which are much lower than the clean air standards. Further investigation showed that in the cold weather seasons, due to the less vertical displacement of air and the decrease in the boundary layer height, the concentration of pollutants in the urban environment is higher than that in the warm weather seasons. Considering the night and day time wind roses showed that despite the existence of valley-mountain structure in the city, the air quality of the city is not affected by the mountain and valley breezes and also night and day wind roses do not follow the trend of these breezes.