Polycyclic Aromatic Hydrocarbons (PAHs) from Diffuse Sources in Coastal Sediments of a Not Industrialised Mediterranean Island

Ustica is an island relatively far from continental, industrial and urban settlements and it has been designated as a marine protected area with the aim of preserving the natural diversity of flora and fauna of the surrounding sea. In such an environment, the assessment of the levels and origin of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) can shed light on the mechanisms and effects of pollutant long-distance transport in the western Mediterranean Sea. PAHs concentrations resulted relatively low when compared with those of other coastal areas of the Mediterranean Sea. The low values of the ratio between low- and high-molecular-weight (LMW and HMW, respectively) PAHs and the fluoranthene and pyrene ratios underlined a pyrolytic origin of these contaminants. The prevalence of HMW-PAHs, however, may also be due to the effect of LMW-PAH preferential degradation during transport and burial into sediments. On the other hand, petrogenic sources prevailed in the past. Whilst PAHs concentrations showed a recent increase, especially at the site close to the port, the estimated sedimentary fluxes of PAHs ranged from 0.5 to 25 μg m−2 year−1.