Patricia Johnston, David Lineman, Carl G Johnston & Laura Leff: Characterization, sources and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in long-term contaminated riverbank sediments; Environ Earth Sci DOI 10.1007/s12665-015-4402-y, 2015 Polycyclic aromatic hydrocarbons (PAHs) are persistant pollutants common in many terrestrial and aquatic ecosystems. PAHs are toxic, cause tumors and cancer. Although there is vast literature on PAH contamination, there is very little 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. High PAH concentrations (94,000–560,000 ug/kg) were detected making this aquatic ecosystem one of the most polluted in the world, second only to a river system in China. Pyrolytic (combustion) sources of PAHs were indicated by the large relative contribution of four ring compounds, while high levels of low molecular weight PAHs also suggested input from petrogenic (petroleum) 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.