Prediction of NO2 and O3 concentrations for NOx plumes photochemically reacting in urban air

Chimney plumes emitted from power stations and industrial plants contain nitrogen oxides. As the plume disperses in the air, photochemical reactions can occur leading to the formation of significant concentrations of the pollutants nitrogen dioxide and ozone. This is particularly the case if the plume mixes with urban air containing reactive organic compounds, however, this situation has proved difficult to model.A novel means for assessing the potential effects of NO_x plumes on photochemical smog concentrations is presented. This is achieved by coupling the Integrated Empirical Rate (IER) photochemistry model with a conventional plume dispersion model, and the technique is especially suited to urban situations. It enables the plume dispersion modelling to be carried out separately to the chemistry calculations, simplifying modelling procedures compared with the previous methods that use detailed chemical kinetic mechanisms. The IER approach also has the advantage that the model can be executed by using air quality monitoring data to provide the ambient air composition. This enables the great variability that is observed in the composition of urban air to be more readily taken into account when assessing the potential environmental impacts of nitrogen oxides to be emitted from proposed industrial developments.