Evaluation of the Industrial Source Complex Short-Term model: dispersion over terrain.

Terrain around an air discharge source can have several influences on diffusion, the pattern of plume dispersion, the wind flow, and the turbulence characteristics. The Industrial Source Complex Short-Term (ISCST) model contains simple algorithms to attempt to account for the effects of terrain. The model has the ability to analyze concentrations in any type of terrain by using the terrain options available for running the model. In this study, the ISCST model was adopted to predict the concentration of sulfur dioxide (SO2) in and around the Mina Al-Fahal refinery in Oman. The central purpose of the study was to examine the performance of the ISCST model in predicting SO2 concentrations under two different scenarios: (1) when flat terrain was assumed; and (2) when the terrain descriptions were addressed. The results of these two scenarios were validated against SO2 monitoring data. The comparison showed that the model underestimated the observed concentrations for the two scenarios. However, the predicted concentrations of SO2 in the absence of the terrain scenario were in better agreement with the observations. Furthermore, the predicted SO2 concentrations were found to be lower than the World Health Organization guideline values, with the maximum concentrations found to occur relatively close to the sources of emission.