Characterization, sources and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated riverbank sediments

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants common in aquatic ecosystems. Although there is a vast literature on PAH contamination, there is a scarcity of information in long-term contaminated ecosystems. This study is the first detailed characterization of PAHs and their sources from riverbank sediments with a historic legacy of pollution. A total of 27 cores were collected at two highly contaminated locations and at one upstream location where apparently there was no PAH contamination. At each location, three cores were taken at three different depths using stainless steel liners. PAHs were extracted by using a modified sonication method followed by identification and quantification by gas chromatography mass spectrometry. Twelve PAHs were quantified and sources were identified using PAH ratios. High PAH concentrations (94,000-560,000 A mu g/kg) were detected making this aquatic ecosystem one of the most polluted in the world. Pyrolytic sources of PAHs was indicated by the large relative contribution of four ring compounds, while high levels of low molecular weight PAHs also suggested input from petrogenic sources. Risk quotients assessment overwhelmingly demonstrated that the riverbank sediments of the Mahoning posed a very high ecological risk to aquatic organisms, even at what was previously considered an unpolluted location. These results suggest that there is a great need for implementation of remediation strategy of the riverbanks.