Monitoring of nitrogen dioxide in and around an Oman liquid natural gas plant using passive diffusion tubes: Exposure and ISCST model study

Recognizing that nitrogen dioxide (Na₂) may be the primary air contaminant released from an Oman liquid natural gas (LNG) plant, this study has been designed with emphasis on this pollutant. The dispersion of Na₂ was examined and compared with measured data during the period from 23 February to 1 April 2001. The observed concentrations were obtained by using Na ₂ diffusion tubes to monitor the spatial distribution of Na ₂ concentrations around at four sites downwind of the plant site. The Industrial Source Complex Short-Term (ISCST) dispersion model was used to predict concentrations at the same sites and for the same time period. Evaluation of the results showed that the model predicted concentrations lower than those observed. However, the comparisons showed that the relationship between the modelled and measured concentrations was consistent. The model also allows the detailed description of predicted concentrations in contour map form. Generally, the predicted concentrations were found to be lower than the permissible limit values, with the maximum ground-level concentrations being found much closer to the plant. On the basis of this study, it can be stated that the Oman LNG plant would not cause any significant deterioration in air quality.