Background: Ammonia is a commonly used chemical in the process industries. Chemical leakage is one of the main problems threatening the staff, facilities, and the environment in the process industries. Objectives: The aim of this study was to model the emission of ammonia and its consequences in the petrochemical industry. Methods: In this study, three accident scenarios of the most probable ones were chosen, including toxic vapor cloud, jet fire, and boiling liquid expanding vapor explosion (BLEVE). Then, the scenario modeling was done using areal locations of hazardous atmospheres (ALOHA) software. Results: In the first scenario, the total released ammonia is 81,316 kg. The concentration of ammonia toxic vapor is greater than 1,100 ppm (AEGL-3 region) at a distance of 1 km, which might cause death in 60 seconds. The overpressure never exceeds 3.5 psi; thus, there is no possibility of serious injury or destruction of buildings. In the third scenario, the thermal radiation of BLEVE is greater than 10 kW/m 2 at a distance of 376 m, which is potentially lethal within 60 seconds. Conclusions: One of the main risks in petrochemical companies is the leakage of ammonia. The toxicity of ammonia is the most significant threat to people. The overpressure of vapor cloud explosion does not cause serious injury or of building destruction. The thermal radiation from jet fire and fireball has no effect on the city while it may cause death to the staff within 60 seconds. Thus, safety precautions should be considered to prevent the consequences of leakage accidents.
Introduction: Estimating air pollution levels in areas with no measurements is a major concern in health-related studies. Therefore, the aim of this study was to investigate the amount of exposure to particulate matter below 2.5 µ (PM2.5) in the metropolis of Tehran. Materials and methods: The hourly concentrations of PM2.5 during 2017-2018 period were acquired from the Department of Environment (DOE) and Air Quality Control Company of Tehran (AQCC). The hourly concentrations were validated and 24-h concentrations were calculated. Inverse distance weighting (IDW), Universal Kriging, and Ordinary Kriging were used to spa- tially model the PM2.5 over Tehran metropolis area. Root Mean Square Error (RMSE) and Mean Error (ME) were used to measure and control for the ac- curacy of the methods. Results: The results of this study showed that RMSE and MENA values in Kriging method was less than the IDW, which indicates that the Kriging was the best method to estimate PM2.5 concentrations. According to the final map, the highest annual concentrations of PM2.5 were observed in the southern and southwestern areas of Tehran (districts 10, 15, 16, 17, and 18). The lowest exposure to PM2.5 was found to be in districts 1, 2, 3, 6, and 8. Conclusion: It can be concluded that Kriging method can predict spatial vari- ations of PM2.5 more accurately than IDW method.
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