382 Int. J. Environment and Pollution, Vol. 14, Nos. 1–6, 2000 Copyright © 2000 Inderscience Enterprises Ltd. A simple and practical model for reactive plumes L. Delamare, A. Coppalle and M. Gonzalez CORIA/LAME-UMR6614, CNRS-Université & INSA de Rouen, Campus du Madrillet, INSA-Avenue de l’Université-BP8, 76801 Saint-Etienne-du-Rouvray, France Abstract: Pollutants emitted from industrial stacks can be transformed by chemical reactions. An interesting case is the NO to NO 2 conversion due to reactions with the ambient ozone. A simple and practical model has been developed to calculate this conversion in the vicinity of the source. Spatial distributions of the reactive species concentrations in the plume are represented by generalized Gaussian profiles. The influence of non-linear chemistry is taken into account by means of different dispersion parameters for each species. The model itself consists of a limited number of ordinary differential equations which are easy to solve numerically. The wind tunnel reactive plume experiment of Builtjes has been simulated. Comparison between the results of this simple model and calculations involving the complete partial differential equations solved on a refined mesh shows that this generalized Gaussian representation of the transverse profiles is valid except very near the source. It turns out that the influence of chemistry on the dispersion parameters has to be taken into account in order to predict the NO/NO 2 conversion accurately. Keywords: Gaussian models, macro-mixing, non-linear chemistry, reactive plumes. Reference to this paper should be made as follows: Delamare, L., Coppalle, A. and Gonzalez, M. (2000) ‘A simple and practical model for reactive plumes’, Int. J. Environment and Pollution, Vol. 14, Nos. 1–6, pp. 382–390. 1 Introduction By reaction with ambient ozone, NO emitted from industrial stacks is converted into NO 2 , which is much more hazardous to human health. 1 It is thus important to be able to predict accurately the spatial distributions of NO and NO 2 in the vicinity of localized emission sources. The length scale of this chemical conversion is so small that it cannot be resolved by grid-based Eulerian air pollution simulation models. Reactive plumes are sub-grid processes and have to be modelled separately. 2 A detailed simulation of each plume in an urban area would greatly increase the computational burden of air pollution simulations. It is, then, useful to define models as simply as possible for the treatment of sub-grid reactive plumes. Such models are reactive Gaussian models and ring models. 3, 4, 5 Available Gaussian models do not take into account the non-linear interaction between the dispersion of the plume and the chemical reactions. Ring models do so, but their precision is related to the number of rings used to discretize the plume. Our objective here is to build a model that takes into account the macro-mixing/chemistry interactions without excessive additional computer time.