Sources and distribution of aliphatic and polyaromatic hydrocarbons in sediments of Sfax, Tunisia, Mediterranean Sea

This investigation is the first extensive study of the spatial distribution and sources of hydrocarbons in surface sediments from the Sfax–Kerkennah coastal zone (Tunisia). We show that the Sfax–Kerkennah coastal zone suffers from serious problems of pollution due to petroleum contamination. Analyses performed by GC/FID and GC/MS permitted a precise determination of both aliphatic and alicyclic compounds (n-alkanes, isoprenoids, hopanes, steranes, diasteranes and unresolved complex mixture of fossil hydrocarbons and highly degraded organic matter (UCM)) and polycyclic aromatic hydrocarbons (PAHs). Non-aromatic hydrocarbon concentrations vary in the range = 16–1729 μg/g sediment d.w., and PAH concentrations vary in the range = 0.11–10.72 μg/g sediment d.w. These concentrations are relatively high, compared to other Mediterranean sites (37 examined sites). n-Alkane, UCM and PAH concentrations with biomarker profiles together prove the presence of a limited petrogenic contamination in sediments close to the Kerkennah Island, 22 km from the harbour of Sfax. In contrast, moderate to high petrogenic contamination is detected in the Sfax area sediments, notably closer to the storage tanks of hydrocarbons. Contaminant patterns indicate that PAHs originate mainly from fossil sources, with higher pyrolytic contributions near industrialized and urban areas. GC/MS analyses indicate the omnipresent contamination by petroleum. This contamination is confirmed by the identification of hopanes with predominant C29 and C30 α,β compounds and steranes with predominance of C29, C28 and C27 compounds.