دکتر مژگان احمدی

 AERMOD model is a Gaussian model, which is widely used to model the emission of air pollutants from different sources and for distances less than 50 km from emission sources. Nowadays, petrochemical industries are one of the essential and cost-effective industries for the country. So, along with the progress of these industries, air pollution control should be considered. The purpose of this study is to model the dispersion of two pollutants, carbon monoxide, and nitrogen oxides, emitted from Maroon petrochemical stacks.

 In this study, the emission of carbon monoxide and nitrogen oxides from the stacks of the Maroon Petrochemical Complex was modeled using the AERMOD model in 2019. For modeling the dispersion of pollutants using AERMOD, which is the model proposed by the EPA for comprehensive studies of air pollution, the three-hour data from Bandar Mahshahr synoptic station as well as a digital elevation model with 30 m pixel size were gathered and then modeling was done in an area of 2500 square kilometers. 

 The results indicated that the average annual concentration of nitrogen dioxide and carbon monoxide pollutants was 1.44 and 1.3 mg/m3, respectively, at a distance of 900 meters from the stacks. This land area includes Maroon Petrochemical Complex and does not affect residential areas.

 The results of this study also indicated that the AERMOD model is suitable for comprehensive studies, with a focus on pollution concentration. The results of this study showed that the concentration of carbon monoxide and nitrogen dioxide pollutants is lower than the standards assigned by the Iranian Department of Environment. Maintenance programs, employee health monitoring, output control, and appropriate controls under EPA recommendations have a significant impact on controlling and reducing pollutant emissions. The result of this study also showed that the AERMOD model is highly efficient in comprehensive air pollution studies that require a detailed investigation of pollutant concentration.

During the past decades, population growth, rapid industrialization, increased air pollution at low levels of the atmosphere, and the impact of heat island have caused dramatic changes in the local climate of the big cities. The release of heat energy increased greenhouse gas emissions, and land use change are among the main causes of local climate change in cities. The effects of urban environments on the atmosphere appear more often as thermal islands. Green space would be effective in reducing the temperature and increasing the humidity, and finally reducing the thermal island phenomenon as well as reducing runoff, improving the comfort of the citizens and, ultimately, the sustainability of the urban environment. The objectives of this study were to prepare land use maps and NDVI vegetation index, as well as land surface temperature maps, and to study the distribution of thermal patterns of land surface and temporal and spatial variations of vegetation and their relation in Isfahan from 1985 to 2016.

For this purpose, satellite imagery was downloaded from the US Geological Survey site. Using the three Landsat satellite TM images of August 1985, 2010, and 2016, the NDVI index was quantitated using Terrset software, and their maps were prepared. Then, by generating land use maps using the maximum likelihood supervised classification method, the analysis of the changes in land uses (such as city, road, agricultural fields, barren lands, river, mountains, and green spaces) was done. Finally, Land Surface Temperature (LST) index was used to estimate the land surface temperature (LST) and its relationship with the vegetation maps.

The trend of land use/cover changes in the study area showed that during the study period, severe degradation occurred in the green space of the area and the main part of these changes was the conversion of green spaces to urban areas. Also, the results indicated an inverse relationship between LST and NDVI index. The results showed that the growth of urban heat islands was toward areas that had encountered poor vegetation and developed constructional uses (residential, industrial, etc.). The results also indicate an accelerated increase in temperature in recent years compared to previous years, as the average annual temperature increase in the period from 2010 to 2016 was 0.61 °C, while the average temperature increase of 0.05 °C was observed from1985 to 2010.

The analysis of the changes in thermal islands of Isfahan was indicative of the increase of thermal islands and spatial reduction in urban cool areas. It can be concluded that the changes occurred in this 30-year period (1985-2016) in various aspects, such as population increase, urban area increase, and land use change eventually increased the area of hot spots. Because of the correlation between surface temperature and NDVI vegetation index, the necessity of protecting vegetation and green space, especially in urban areas, is a critical variable for climate change modification for responsible institutions in urban management. The results of this study could provide critical insights on precise and effective urban vegetation management with the purpose of Urban Heat Island mitigation for urban planners and managers.