Distribution of alternant and non-alternant polycyclic aromatic hydrocarbons in sediments and clams of the Pialassa Baiona Lagoon (Ravenna, Italy)

Abstract

The distribution of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and clams (Tapes philippinarum) in a Ramsar site (Pialassa Baiona Lagoon, Italy) was investigated by high-performance liquid chromatography (HPLC) with fluorescence detection and gas chromatography–mass spectrometry (GC–MS). Surface sediments exhibited a variable degree of PAH contamination, with high concentration values (>100 mg/kg) in the southern area, in the proximity of the industrial district, and much lower values (<1 mg/kg) in the northern area. The molecular distribution of PAHs was very similar throughout the Lagoon, confirming previous studies indicating a common source of contamination attributed to partial combustion of methane. With the exception of the northernmost site, the molecular distribution was characterized by high levels of non-alternant PAHs, among which the probable mutagenic cyclopenta[cd]pyrene was the predominant species. PAH levels in tissues of clams collected in the polluted area, where fishing is forbidden, and in the less-polluted permitted area were similar (∼0.1 mg/kg dry weight). In both sites, the PAH distribution in clams was different from that observed in sediments. In particular, the levels of non-alternant PAHs with an external cyclopenta ring (CP-PAHs), acenaphtylene and cyclopenta[cd]pyrene, were remarkably lowered in clams with respect to sediments, probably as a result of their chemical/biological reactivity.