Past soil contaminations may interfere with the biomonitoring of current PCB release from a RDF co-fuelled cement plant: a case study from NE Italy

Although the intentional production of polychlorinated biphenyls (PCBs) has totally been banned, these pollutants are still released into the atmosphere by industrial and domestic burning processes and by volatilization from soils locally contaminated by PCB spill-overs. The present work aims at identifying the PCB sources in a mixed land use area of northeastern Italy around a cement plant co-powered with recovered derived fuels (RDFs) from 2018. Leaves of Robinia pseudoacacia trees were systematically sampled over c. 40 km2 in 37 sites and analyzed for 12 dioxin-like and 20 non-dioxin-like congeners. The samples of most sampling sites had a PCB content < LOD, whereas those with higher content were located in urban sites. The spatial distribution of PCB leaf content was not centered on the purported emission sources. The samples of three spatially unrelated sites had high contents of 2, 12 and 18 PCB congeners, with the last two having combinations fully compatible with past commercial mixtures traded under different names. Comparison of these results with those of previous (bio-)monitoring surveys supports the hypothesis that the area has been subjected to punctiform PCB spill-overs, which overwhelm the contribution from present day industrial emissions, comprised of those actually derived from the use of RDFs.