Persistent organic pollutants and metals in atmospheric depositions at an urban site in Rome, Italy: Deposition...

Atmospheric deposition is one of the main routes by which persistent pollutants are transferred from the air to the soil and subsequently into the food chain, with potential impacts on human health. This study investigated atmospheric deposition of persistent pollutants at an urban site in Rome (ISS building), Italy, with particular attention to pollutant deposition fluxes (pg, ng or μg m^-2 d^-1) normalized to the collected sedimentable particulate matter (pg, ng or μg mg^-1 SPM), and comparison between street and roof-level samples. Monthly samples were collected from 1/08/2023 to 31/08/2024 using deposimeters. PCDD/Fs, PCBs, PAHs, and metals were assessed in atmospheric deposition using GC-HRMS and ICP-MS instrumentation. Pollutants deposition fluxes were consistently higher at street level, with annual SPM fluxes of 42 and 26 mg m^-2 d^-1 at street and roof level, respectively. Although deposition fluxes were higher at street level, the Wilcoxon signed-rank non-parametric test showed no significant differences (p > 0.05) between street and roof level samples when pollutant deposition fluxes were normalized to SPM. This suggests comparable contamination levels of deposited dust at the two sampling heights. According to the Kruskal-Wallis test, significant (p < 0.05) seasonal patterns were observed for PCDD/Fs, PCBs and for certain metals (Cr, As, Ni, Sb), with peak concentrations generally occurring in winter, whilst PAHs show significant peak in summer and autumn. Spearman correlation analysis revealed strong associations among organic pollutants (p < 0.01), indicating shared combustion-related sources, while metals were mainly linked to non-exhaust traffic emissions, resuspended road dust and diffuse urban sources. These results show that atmospheric deposition in Rome is controlled by source type and seasonality, and highlight the value of combining deposition fluxes with pollutant concentrations in SPM to improve urban contamination assessment and support exposure-oriented monitoring.