Abstract
Short distance diffusion with chemical reaction experiment was investigated. NO, NO2 and O3 concentrations were measured within 120 m downwind from the source which emitted NO gas continuously into the atmosphere with background ozone. Very large fluctuation of NOx concentration was observed, and average concentrations of instantaneous plumes were obtained. The results show that the sums [NO]+[NO2] and [NO2]+[O3] are conserved under chemical reaction and that the photochemical decomposition rate of NO2 is much smaller than its formation rate during the daytime when travelling time is less than 20 sec. And it is also shown the formation rate of NO2 depends not only upon travelling time but on background ozone concentration, and also on the dilution rate due to turbulent diffusion.
A simple model of diffusion with reaction which is applicable within short distances from the source is presented. It gives fairly good agreement with observed concentrations in instantaneous plumes.
