## 4 Conclusions  
The monitoring of deposition airborne particle greatly contributes to the knowledge on the dynamic of pollution in an area allowing to study the deposition fluxes, the pollutants environmental fate with the aim to address the potential exposure for population. Total depositions (bulk) are particularly suitable to measure the environmental POPs concentration. The data collected by bulk deposition are useful to estimate contamination of farmlands and a subsequent accumulation in the food chain (in which POPs are particularly associated with to fats). In this study, we want to replicate the approach already used in countries like Belgium, Germany and France for PCDD/Fs and PCBs to identify reference values (TDI/deposition) for the Italian situation. Particularly, the results of the chemical characterization of the depositions show that the major differences between the sites are attributable to the PCDD/Fs content. In fact, the total metal content and the total PAHs one are comparable between the four sites, whereas PCDD/Fs and DL-PCBs between the Roccaccia and Rocca Respanpami sites are 3/4 orders of magnitude higher than the other two locations. This suggests that what has been observed is due to activities carried out locally, probably attributable to livestock and agricultural activities. This is conceivable by observing the seasonal differences in the content of PCDD/Fs and DL-PCBs in the different sites: in fact, higher contributions of PCDD/Fs and DL-PCBs in the depositions are observed mainly in summer and autumn. Even the meteorological characteristics of the summer may have contributed to the increase in these depositions. Furthermore, it is highlighted that the results of the chemical characterization of the depositions do not distinguish the potential contribution due to the CTE plant, unlike the results of the airborne PM chemical characterization study [67], performed in the same area. At present, it is necessary to establish specific guidelines and/or limits at European level to better manage the particularly difficult environmental and health situations of the population that are observed in the various national contexts. Finally, it is also desirable find a European consensus on sampling procedures, analytical methods and assessment methods for a unique, accurate and effective evaluation approach. Figure 7: PCA of the four investigated locations. Component 1: inorganic fraction; Component 2: organic fraction. **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)]([https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)) 417/11/4/1827/s1, Tables S1-S9: Table S1. Limit of Detections (LODs) for each compound/metal determined in this study. LODs were determined according to the methods reported in International guidelines [51, 52, 53, 54, 55]; Table S2. Deposition (mg m\({}^{-2}\)d\({}^{-1}\)) of the total sedimentable particulate matter (PM) per season at each location; Table S3. Atmospheric deposition of PCDD/Fs + DL-PCBs per season at each location; Table S4. Levels of PCDD/Fs and DL-PCBs expressed as equivalent toxicity I-TE, WHO-TE\({}_{1998}\) and WHO-TE\({}_{2005}\) at Roccaccia location; Table S5. Levels of PCDD/Fs and DL-PCBs expressed as equivalent toxicity I-TE, WHO-TE\({}_{1998}\) and WHO-TE\({}_{2005}\) at S. Agostino location; Table S6. Levels of PCDD/Fs and DL-PCBs expressed as equivalent toxicity I-TE, WHO-TE\({}_{1998}\) and WHO-TE\({}_{2005}\) at Allumiere location; Table S7. Levels of PCDD/Fs and DL-PCBs expressed as equivalent toxicity I-TE, WHO-TE\({}_{1998}\) and WHO-TE\({}_{2005}\) at Rocca Respampani location; Table S8. Seasonal levels of the deposition rates (ng m\({}^{-2}\)d\({}^{-1}\)) for PAHs determined in the four investigated locations; Table S9. Seasonal levels of the deposition rates (ug m\({}^{-2}\)d\({}^{-1}\)) for metals determined in the four investigated locations. Conceptualization, M.E.S., G.M. and P.A. ; methodology, G.S. and G.M. ; software, M.I. ; validation, M.I. and G.S.