Occurrence, Loading, and Exposure of Atmospheric Particle-Bound POPs at the African and European Edges of the Western Mediterranean Sea.

ABSTRACT

A comparative study for 62 toxic chemicals based on the simultaneous monthly collection of aerosol samples during 2015-2016 in two coastal cities at both the African (Bizerte, Tunisia) and European (Marseille, France) edges of the Western Mediterranean basin is presented. Legacy polychlorinated biphenyls (∑18PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (∑17PCDD/Fs) show generally higher median levels at the African edge (2.1 and 0.2 pg m-3, respectively) compared to the European coastal site (1.0 and 0.08 pg m-3, respectively). Contrarily, the "emerging" polybrominated diphenyl ethers' (∑27PBDEs) median concentrations were higher in Marseille (∼9.0 pg m-3) compared to Bizerte (∼6.0 pg m-3). Different past usages and current emission patterns were found at both edges of the Western Mediterranean, most probably linked to the respective different regulatory frameworks for toxic chemicals. Our results indicate that the total organic carbon (TOC) and/or the elemental carbon (EC) contents in the atmospheric aerosol may have a stronger effect than the total suspended particle (TSP) content as a whole on the spatial-temporal variability and the long-range atmospheric transport potential of the studied POPs. A "jumping" of the PBDE local atmospheric stocks from the Northwestern European Mediterranean edge to the Northwestern African coast seems to be possible under favorable conditions at present. While a higher PBDE median loading is estimated for the Marseille area (∼550 ng m-2 y-1) compared to Bizerte (∼400 ng m-2 y-1), the median PCB and PCDD/F dry deposition fluxes were higher at the African site, resulting in a 3-fold higher toxic equivalent (TEQ) loading of dioxin-like pollutants (400 pg TEQ m-2 y-1) compared to Marseille (∼140 pg TEQ m-2 y-1), with potential implications for aquatic organisms. However, the inhalation exposure assessment points to a minimum risk for human health at both sites.