A model to simulate the pollutant concentrations in the reactive plume is developed. Equal partitioning of the plume into lateral cross sections enabled the mass conservation relationship to govern the concentrations in each unit cell. The model results for inert species are similar to that of the Gaussian plume model, both in ground level and airborne concentrations. For the simulated reactive plume, the model results are compared with the measured data of Janssan [6]. This model formulation give a similar downwind variation trend of the NO conversion rate, however consistently overestimated results.