رضا میرزایی

Arak is one of the eight most polluted cities in Iran, whose pollution is mainly due to the activities of various industries located in the city or its suburbs. Using air pollution modeling it would be possible to estimate the effect of emissions of suspended particles and gases from the activities of various industries on the local environment. This study is an attempt to investigate the impact of existing and under construction industries in Arak on the air quality of the city using the ADMS model as a widely used and trusted model of the Department of Environment (DoE).

Because the main sources of air pollution in Arak are of focal type, in modeling air pollution, 17 large industries (including 98 chimneys) located in the city were considered as pollution points. In addition to the emission data, the geometrical data of the chimneys including the height and diameter of their opening and the temperature of the exhaust air were also included in the model. To validate the model outputs, the measurement values of the environmental stations were compared with the values estimated by the modeling using Pearson linear correlation coefficient.

The results showed that the concentration of CO, SO2, and NO2 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 SO2 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 NO2 contour lines was the same as NO2. 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 H2S 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 SO2 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 NO2 were less than the modeled values, revealing that the industries had a greater share in the emission of this gas. The overestimate 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. Industries have a 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.

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.

Accelerating the process of industrialization has increased energy consumption as the most essential factor of development in societies. Powerplants have a main role in this development. In powerplants, the first step can be prepare fuel.Air pollution from powerplants mainly includes the release of carbon monoxide, sulfur oxides, nitrogen oxides. In this paper, the amount of emissions mentioned in the periods of using gas and mazut fuel during ten years has been studied.CO concentration in both cases was lower than the standard of the Environmental Protection Agency of Iran, NOx concentration in both sections is higher than standard level The concentration of SOx during the use of mazut fuel was significantly different from the use of gas fuel and at the time of use of mazut fuel is 65% higher than the standard of the Environmental Protection Organization of Iran. The high consumption of fossil fuels to supply electricity has caused air water and soil pollution, global warming, acid rain and carcinogens. Although the use of gas to generate electricity significantly reduces waste-related problems in the electricity industry and power plants, the use of renewable energy as an alternative to fossil fuels could bring a brighter future to a cleaner environment.