PREDICTION OF NO2 AND O-3 CONCENTRATIONS FOR NOX PLUMES PHOTOCHEMICALLY REACTING IN URBAN AIR

Chimney plumes emitted from power stations and industrial plants conta in nitrogen oxides. As the plume disperses in the air, photochemical r eactions can occur leading to the formation of significant concentrati ons of the pollutants nitrogen dioxide and ozone. This is particularly the case if the plume mixes with urban air containing reactive organi c compounds, however, this situation has proved difficult to model. A novel means for assessing the potential effects of NOx plumes on photo chemical smog concentrations is presented. This is achieved by couplin g the Integrated Empirical Rate (IER) photochemistry model with a conv entional plume dispersion model, and the technique is especially suite d to urban situations. It enables the plume dispersion modelling to be carried out separately to the chemistry calculations, simplifying mod elling 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 variabili ty 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 development s.