Interactions between complicated flow-dispersion patterns and boundary layer evolution in a mountainous complex terrain during elevated SO 2 concentrations

The dispersion of air pollutants from multiple industrial stacks located in complex topography is an interesting subject. An attractive case is that of the wider region of Western Macedonia in NW Greece, where the greater amount of electric power of Greece is being produced by lignite power plant stations (LPPS). Considerable amounts of atmospheric pollutants are emitted by those LPPS into the atmosphere due to the quantities of coal burned. The variability of the topographic features and the terrain complexity of the area may lead to the formation of local atmospheric circulations of various types, which affect pollutant’s transport and dispersion. In the present work, the dispersion conditions that favor the pollutants accumulation in the area are investigated. For this purpose, 1 year’s hourly SO 2 concentrations, surface wind measurements and a mesoscale meteorological and air pollution model (The Air Pollution Model, TAPM) were used. The SO 2 and wind measurements were collected in situ from monitoring stations located nearby and at a greater distance from the power plants. Yearly and daily variations of SO 2 concentrations are analyzed and discussed, and the period with the highest concentrations is selected. During this period, the evolution of the atmospheric boundary layer (ABL) in the area as well as the pollutants dispersion is examined. Statistical measures between modeled and observed meteorological data were in good agreement and a good correlation coefficient 0.68 and 0.98 was found in the SO 2 variations. The analysis of the wind fields indicated better ventilation in the center of the area due to topographic venturi effects, while the dispersion mechanism which resulted in the relatively high ground level concentrations was fumigation. Finally, the evolution of the ABL was affected by the complex interactions between topography and mesoscale flows as it was found by the turbulent kinetic energy cross sections.