Origin of Polycyclic Aromatic Hydrocarbons (PAHs) in Coastal Marine Sediments: Case Studies in Cotonou (Benin) and Aquitaine (France) Areas

Polycyclic Aromatic Hydrocarbons (PAHs) were identified and quantified in recent sediments of the Cotonou coastal zones (Benin) in the total concentration range 25–1450 ng g−1, while the Aquitaine sediment samples (France) exhibited total PAH concentrations in the range 4–855 ng g−1. The highest contents of PAHs were found in the harbours, as well in Cotonou as in the Aquitaine region, with the maximum values in the Cotonou harbour. However, the PAH concentrations were comparable with those of slightly contaminated zones. Good correlations observed between a certain number of pairs of isomer PAH concentrations allowed to identify six origin molecular indices that were used to identify the PAH contamination sources in the studied sampling stations: Phe/An, Flt/Py, Chry/BaA, LMW/HMW, Per/∑(PAH), and Per/∑(penta-aromatics). In general, the Cotonou lagoon sampling sites were contaminated mainly by petrogenic PAHs, due to petroleum trade at individual scale along the lagoon, and also waste oils from mechanics shops; the Aquitaine samples were polluted by pyrolytic origin PAHs. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed in the harbours due to petroleum products deliveries and fuel combustion emissions from the ships staying alongside the quays. Diagenetic origin of perylene was confirmed in this study, but its possible formation by combustion of organic matter was also considered because of the relatively higher concentrations of this PAH in the harbours of Cotonou and of Aquitaine region sediment samples.