Investigating the impact of existing and under construction industries on the air quality of Arak City using ADMS model

Investigating the impact of existing and under construction industries on the air quality of Arak City using ADMS model. Environmental 20(1): 21-40. Results and discussion: The results showed that the concentration of CO, SO 2 , and NO 2 in all stations was within the permissible level announced by the DoE. The dispersion of suspended particles (contour lines) in the city was to the west and southwest and up to a radius of 3 km in the prevailing and semi-prevailing wind direction. This for Shazand was to the west up to a radius of 1 km in the prevailing wind direction and to the southwest up to 5 km in the direction of semi- prevailing wind until reaching the background concentration of 19.1 μg. Accumulation of SO 2 contour lines in Shazand pollution center was observed up to a radius of 7 km in the west direction and up to a radius of 10 km in the southwest direction. The accumulation of NO 2 contour lines was the same as NO 2 . The radius of impact of CO gas was extended from Arak to Shazand. Accumulation of CO contour lines in Arak was up to a radius of 5 km in the direction of west and southwest. The accumulation of H 2 S contour lines in Shazand was up to a radius of 5 km towards the directions of west, southeast, and southwest. In general, the difference between the sampling and modeling results indicated the pollution sources that were not observed in the model and were beyond those emitted from the factories. In most stations, the modeled and directly monitored SO 2 concentrations were not much different and the correlation coefficient of the data was high, indicating the accuracy of the calculations and the prominent role of industries in the emission of this gaseous pollutant. Also, in most stations, the results of environmental measurement of NO 2 were less than the modeled values, revealing that the industries had a greater share in the emission of this gas. The overestimation of this emission may probably be due to the inclusion of the under-construction industries in the model. The environmental concentration of CO in all stations was higher than the modeled values. small share in the pollution load of this pollutant while in urban areas, the concentration of CO depends on the mobile sources and traffic load. Conclusion: In general, the pollution levels of the city showed that the center of pollution was in the southeast of Arak and in the complex of the refinery, petrochemical company, and thermal power plant. According to the overlaid contours of emissions, a number of points (14 points) that were closest to the pollution centers were proposed as critical stations, two points as control stations, and 4 points as the stations exposed to pollution in each period.