Turbulence effects upon the NO2/NO conversion in the vicinity of an urban area

The dispersion and chemical transformation of nitrogen oxides have been studied in an urban atmosphere. In this work, nitric oxide is considered as being emitted from the ground. It is mixed with ambient ozone with which it reacts to produce nitrogen dioxide. Numerical integration of the transport equation of each species is carried out in the boundary layer, allowing for the effects of dipersion, macro- and micromixing and chemistry. The results show that the influence of turbulence on chemical reactions is important close to the emission zone. It is also found that the NO/NO2 conversion is low in this region and that it grows with increasing distances.