The role of a steel plant in north-west Italy to the local air concentrations of PCDD/Fs.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are ubiquitous contaminants, mainly released into the environment during combustion processes (point sources), but also from other sources (traffic, uncontrolled combustion). This study aims at investigating the contribution of a steel plant in NW Italy (700000tons of steelyear(-1)) to the air concentrations of PCDDs/PCDFs at local level, through the analysis of measured, modelled and literature data. The study was carried out in an area of 600km(2), using air quality data measured by the institutional monitoring network, data obtained from AERMOD simulations and literature data. The measured air concentrations were consistent with literature values for similar areas, and both the homologue profiles and PCA analyses showed a clear distinction between the monitoring stations and the source profiles. All the previous results were confirmed by the air dispersion model (AERMOD), that predicted PCDD/F air concentrations due to the steel plant from four to two orders of magnitude lower than those measured in the monitoring stations, highlighting the presence of other sources. This study outlines the limited influence of the source in the local PCDD/F air concentrations and at the same time the usefulness of a joint analysis of measured, literature and calculated data to correctly evaluate the role of a source to the local pollution. The study also highlights the usefulness of AERMOD as a complementary tool to define the correct placement of monitoring stations and to locate those areas expected to have the highest air concentrations deriving from a source.