Mobilization of PAHs by Wave-Induced Resuspension and Liquefaction in Silty Sediment

Silty seabed sediments in the subaqueous delta of the Yellow River are heavily contaminated with petroleum-derived polycyclic aromatic hydrocarbons (PAHs). Storm-induced sediment resuspension and liquefaction are key mechanisms responsible for the remobilization of PAHs into the overlying water column. In this study, laboratory-scale wave flume experiments were conducted to simulate PAH release under three hydrodynamic scenarios: (i) static diffusion (Stage I), (ii) low-intensity wave action (5 cm wave height, Stage II), and (iii) high-intensity wave action (12 cm wave height, Stage III). Results revealed a strong positive correlation between suspended particulate matter (SPM) and PAH concentrations in the aqueous phase during sediment disturbance. In particular, sediment liquefaction significantly enhanced PAH release, with concentrations up to five times higher than those under static conditions. Furthermore, liquefaction facilitated vertical migration of PAHs within sediments, resulting in reductions in PAH levels below the original background concentrations. The release dynamics varied notably among PAH species: low-molecular-weight (2–3 ring) PAHs, with lower hydrophobicity, were primarily detected in the aqueous phase, while medium- and high-molecular-weight PAHs remained predominantly associated with sediment particles. These findings underscore the critical role of hydrodynamic disturbances—especially sediment liquefaction—in influencing PAH mobility and offer important implications for pollution risk assessment and coastal management in storm-impacted deltaic environments.