Surface waters are a source of polychlorinated biphenyls to the coastal atmosphere of the North-Western Mediterranean Sea

Atmospheric (gaseous and particulate) and seawater (dissolved and particulate in the surface microlayer and underlying waters) samples were collected in 2001 and 2002 in two North-Western Mediterranean contrasting coastal environments, Banyuls-sur-Mer (France) and Barcelona (Spain). The total aerosol suspended particle concentrations (μg m−3) were higher in Barcelona (266 ± 132) than in Banyuls-sur-Mer (149 ± 43), even under near-gale conditions. The influence of the marine aerosol in the total suspended particles (TSP) concentration was backed by both organic carbon (OC) and elemental carbon (EC) concentrations, as they exhibited lower levels in Banyuls (3 ± 2 μg OC m−3 and 0.4 ± 0.3 μg EC m−3) than in Barcelona (31 ± 26 μg OC m−3 and 6 ± 8 μg EC m−3). Moreover, samples from Barcelona, both atmospheric and seawater, showed greater variability than in Banyuls (Snedecor’s test (p < 0.001)) possibly reflecting the influence of urban sources of pollutants. Concentrations of atmospheric PCBs (Σ41 congeners) off-shore Barcelona ranged from 389 to 1410 pg m−3 in the gas phase and from 71 to 78 pg m−3 in the aerosol phase. In Banyuls, concentrations were 30.7–858 pg m−3 in the gas phase and 12.8–41.2 pg m−3 in the aerosol phase. Their gas-particle partitioning suggested that PCBs in the samples were close to equilibrium (deduced from the regression of the experimental log Kp and logPl0). Moreover, a positive correlation was found between wind direction, wind speed and atmospheric PCB concentrations, which is consistent with the fact the PCB concentration of the marine waters, influenced by coastal run-off, become a secondary source for these semi-volatile compounds after volatilization to the coastal atmosphere. This is supported by the high dissolved concentrations in the coastal surface waters, and specially by the enrichment found in the surface microlayer.