PARTICLE MODEL SIMULATION OF POLLUTANTS DISPERSION FROM A LINE SOURCEIN COMPLEX TERRAIN

Pollutant transport and dispersion in complex orography are usually di fficult to model accurately, due to the problem of properly reproducin g wind and turbulence fields and interactions between pollutants and o rography. In these situations the well-known Gaussian approach is limi ted. For studies of line sources (i.e. highways), models are available which are adequate for flat terrain and steady-state conditions (i.e. US-EPA recommended CALINE-3 and HIWAY-2). In complex terrain, however , no well-tested models are available. A possible approach to the prob lem is the use of a wind field model with a Lagrangian dispersion mode l well suited to consider both orography-induced inhomogeneities and l ine sources. We present the application of SPRAY particle model to rep roduce pollutants dispersion from a highway at the bottom of a deep al pine valley, where pollutants are well confined and stagnation may occ ur. Model results for NOx are compared to those of the EPA recommended model HIWAY-2 and to measured concentrations.