Estimation of the pollution concentration in the vicinity of a cellulose plant in an Alpine valley using the non-hydrostatic mesoscale model GRAMM

摘要

In this paper the application of the non-hydrostatic mesoscale model GRAMM to a mountinous region in the Alps is described. The simulation is used for the estimation of the pollution dispersion of a cellulose plant during selected weather conditions. The GRAMM model solves the conservation equations for mass, momentum, potential temperature and humidity in a terrain-following grid. The time integration scheme is explizit depending on two time levels according to Adams-Bashforth. The discretisation of the model makes use of the Gaussian and the first Green integral theorem without any co-ordinate transformation. The lateral boundary conditions are generalised radiation boundary conditions. On the upper border the boundary conditions damp the vertical velocities and the integral mass flow is kept near zero. The soil temperature is calculated considering the influence of radiation. The investigated region comprises an area of 13.5 x 13.5 km and the altidutes of the highest peaks are more than 1000 m above ground level. Meteorological conditions were measured at one point during several years. This data have been analysed with special attention to the meteorological conditions during the growth season of the coniferous trees. The concentration of pollutants during the morning hours of spring and summer are important for the rate of growth. The investigated pollutant was SO_2, which will be emitted at a height of 90 m above ground level. The simulations were carried out for three meteorological situations and qualitatively checked. The calculated pollution concentrations were compared to the theoretical values of a Gaussian plume model. The GRAMM concentrations are lower than the maximum values of the results of the Gaussian plume model.