Monitoring pops in a complex environment: the role of modelling

Pollutants released by large industries are often a cause of major concern for local communities liv ing nearby. Traditional monitoring consists of continuous emissions control ling systems (CEMS) and regular sampling of flue ga s associated with monitoring stations positioned at best for checking on air qua lity where people reside. Sometimes a remote monito ring station is employed to set a background pollution reference value. In the case of Persistent Organic Pollutants (POPs) this may not be the best planning strategy for mon itoring exposure. In fact, direct exposure through inhalation forms just a minor cont ribution to the total people exposure. A much more relevant exposure is indirect, due to the ingestion of food, either vegetable or animal, which has been contaminated. For this reason, a gre at care should be put in placing monitoring instruments where deposition of POPs is larger, especially when industrial and rural areas are bordering. As an example, we present the case of a steel found ry in an alpine valley, emitting PCDD/Fs and PCBs b esides traditional air pollutants. Using all the available data registered by the CEMS installed on the main chimney, hourly concentratio n and deposition fields have been obtained by running a one year long simulation with the three dimensional lagrangian model SPRAY, capa ble of simulating both dry and wet deposition. Due to the complexity of the local topography, a 25 0m horizontal spatial resolution grid has been used . Meteorological fields have been obtained at the same resolution by a downscaling pr ocedure with a mass-consistent model (SWIFT). The s tatistical analysis of the results shows the relevance of secondary fallout patterns i n remote areas, where vegetables could be grown for local consumption or dairy cattle could frequently pasture, thus suggesting the need of specific monitoring for remote areas in order to attain a wider assessment of human exposure.