Polychlorinated naphthalenes in the gas-phase of the Venice Lagoon atmosphere

The gas-phase concentrations of polychlorinated naphthalenes (PCNs) (16 congeners) were investigated over 1 year at two sites in the Venice Lagoon (‘marine’ and ‘industrial’) and at a mainland station (‘rural’). ΣPCN concentrations were mainly composed of lighter congeners and ranged from 191 to 3415 fg m−3 with values comparable with those of ‘background’ air. The lowest ΣPCN concentration was detected at the ‘marine’ site while no significant differences were found between the ‘industrial’ and ‘rural’ stations. The presence of combustion marker congeners in most samples suggests that this is the main source of PCN at all sites.The variation of ΣPCN concentrations over the year showed that the highest values occurred from autumn to early spring months at the ‘industrial’ and ‘marine’ sites, while at the ‘rural’ station the values were quite homogeneous, with some peaks in summer. The temperature–PCN relationship was statistically significant only at the ‘marine’ station, but with a weak correlation. The linear regression between PCN, PAH and PCB, and the seasonal evolution of their ratios was investigated to gain a better understanding of the potential sources of PCNs. At the ‘marine’ site, it may be supposed that combustion processes constitute PCN sources, with a substantial sea influence. At the ‘rural’ site, continuous PCN sources from distant points of emission are hypothesized while the ‘industrial’ site may be supposed to feature an unidentifiable continuous source as well as other seasonal sources.