Modelling the trends of vehicle-emitted pollutants in Salalah, Sultanate of Oman, over a 10-year period

From 2004 to 2014, a significant increase in the number of vehicles in Salalah, Oman, has been observed and is related to the fact that the city has become a more popular tourist destination. Due to this rise in the number of vehicles, traffic jams have become a serious problem in Salalah. Therefore, this study aims to assess carbon monoxide (CO), nitrogen oxides (NOx), and carbon dioxide (CO2) from 2004 to 2014 for the Salalah region using the CALPUFF modelling system. Although the number of vehicles gradually increased in the area, the pollutant concentration levels fluctuated. CALPUFF results illustrated that CO levels were within the allowable concentrations assigned by the U.S. Environmental Protection Agency (EPA) standards, but NOx and CO2 concentrations were higher than the criterion limits set by the EPA and the Ontario Ministry of the Environment and Climate Change’s emission standards. Since Salalah is a coastal city, wind blowing toward the land from the sea significantly affects the dispersion of pollutants. Additionally, most of the maximum concentrations of the three pollutants were located near the centers of the streets. Replacing roundabouts with flyovers might significantly reduce traffic jams and vehicle-emitted pollutants in Salalah.