Assessment of the local role of a steel making plant by POPs deposition measurements

Atmospheric depositions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were monitored at three sites in the vicinity of a steel making plant, located in an Italian alpine valley. A high variability in the deposition of PCDD/Fs was observed. The influence of the plant was noticeable at two of the sampling sites. However, as the congener profiles demonstrated, wood burning for domestic heating is an additional source of PCDD/Fs for the area under investigation, and this interferes with the characterization of the emissions from the steel plant. The influence of the plant, in terms of PCDD/F deposition, was not noticeable at the most distant site (2km), where an extremely high peak of PCDD/F deposition was measured during the period from 12 January-22 February 2012. The comparison between the congener distribution of PCDD/Fs observed in this sample and the fingerprints of different sources could justify the attribution of this anomalous peak to a possible episode of domestic waste combustion. In order to find a better correlation between the deposition to soil and emissions from the plant, the congener distribution of PCBs was studied. The PCB profiles observed at the three sites well reproduced the average profile found in samples of ash retained by the bag filter of the plant. Thus the monitoring of PCB deposition is an interesting starting point to calibrate dispersion models to assess the impact of steel making activities.