Factors affecting inter-annual variability of NOx and NO2 concentrations from single point sources. (PDF)
In the application of dispersion modelling for regulatory purposes questions frequently arise regarding the meteorological data used for the study: in particular how many years data are sufficient; is the meteorological site representative of the dispersion site? Although studies have been conducted on the impact of meteorology from different years on ground level concentrations from point sources [1,2] these studies have generally focussed on the source contribution, without consideration of background concentrations or of any chemical reactions that may take place. This approach is sufficient for releases of SO 2 from large dominant sources. However, most regulatory studies now focus on NO 2 , for which background concentrations and chemical reactions are important. Investigation of the inter-annual variability of only the process contributions to NO x may give little indication of what is actually important, that is, the inter-annual variability of the NO 2 concentration. In this note we present some calculations of NO x and NO 2 using ADMS 3.1 , in which the impacts of both background pollutant concentrations and chemical reactions are assessed. The focus is on isolated point sources without building impacts. The impact of the choice of meteorological site is not considered here.