Modeling of Diffusion in a Wide Alpine Valley

Summary  A K-type diffusion model coupled with a massconsistent wind model is applied for one of the rural biological waste disposal sites in Austrian Alps. The site is situated in the P?ls valley in the eastern Alps, 250 km south-west of Vienna in Austria Aim of the study is to demonstrate dispersion of H₂S from the site to near by village. Model simulations are carried out each for an evening and a morning transition case characterized by flow reversals. The role of locally generated wind in changing the pollutant distribution over nearby residential area is investigated. Surface observations at two stations toward the open boundaries of the main valley are used to derive the turbulence parameters and then to obtain initial inputs of wind profiles. The turbulence parameters behave analogous to that over a plane terrain after the establishment of the valley wind. The model simulations are done for eight hours during the evening transition and eighteen hours for the morning transition by incorporating the wind field from a mass consistent wind model. The results are compared with SF₆ tracer experiments conducted during those periods. The model outputs and the observations at various points inside the valley are in good correlation except for NW part of the valley after the reversal of valley wind. The results also reveal the potential of a simple approach with minimized inputs. Received August 15, 1997 Revised August 15, 1998