Atmospheric impact of power plant stack emissions using air pollutant dispersion model at micro-scale

This study deals with a case of local air quality impact arising from a power plant (tri-generator and conventional boilers) designed to meet the energy demand of the General Hospital of Modena, central Po Valley, Northern Italy. Stack emissions are expected to fall over the densely populated urban area nearby the General Hospital, where main impacting sources currently are vehicular traffic and household heating system. Pollutant accumulation phenomena often occur in Modena, especially during winter season, even because calm wind events and strong atmospheric stability are very frequent and tend to prevent pollution removal. Hence high concentration levels for atmospheric pollutants, such as NO x , CO and PM10, are recurrently expected. The atmospheric impact of the power plant can be assessed using dispersion modeling, in order to simulate pollutant distribution, i.e. concentration fields, in the surrounding of the source. Since the plant is placed within the urban area the dispersion phenomena are not only driven by meteorology, but depend also on airflow perturbations by turbulence due to the urban canopy. In such complex conditions, the simulation of pollutant dispersion has been performed by a micro-scale dispersion model, which is able to take into account building shape and arrangement, as well as non-homogeneous and non-stationary conditions. Micro-scale simulations were carried out for power plant NO x emissions according to different daily meteorological scenarios; all simulations span over a period of 24 hours, and a hourly modulation of emission pattern and meteorological data is considered. Simulation results are presented through concentration maps and compared with hourly concentration data measured at the air quality monitoring sites by the Local Environmental Agency in Modena. Aim of the study is to compare the contribution of power plant emissions on air quality with the other NO x emission sources impacting on the receptors. Future analyses will focus on more detailed investigation of source contribution apportionment, by the simulation of both power plant and vehicular traffic emissions. All simulations were performed using ARIA INDUSTRY software package, developed by Arianet s.r.l.