Impacts of suspended sediment on oil spill in macro-tidal turbid waters: An example in Zhoushan Archipelago

The concentration of suspended sediment was found to impact the characteristics and dynamics of oil spills, as indicated by the rate of formation of oil particle aggregates (OPA). The transport and fate of oil spills in the Zhoushan Archipelago were simulated by using a combined hydro-sediment-oil spill model. We studied the impacts of suspended sediment on oil spills in macro-tidal turbid archipelagic seas. The model results indicated that the formation of OPAs is affected by the concentration of suspended sediment, energy dissipation rate, oil density, and hydrodynamics (winds and tides). An increase in oil density accelerated the formation of suspended buoyant OPAs but suppressed the formation of negatively buoyant OPAs. Winds and tides affected the rate of OPA formation by changing the energy dissipation rate and the concentration of suspended sediment, respectively. Oil spill dispersion is impacted by winds, tides, and oil spill location, through the changes in the formation of both suspended buoyant OPAs and negatively buoyant OPAs. Although strong winds promote the formation of OPAs and tend to reduce oil content they also potentially enlarge the oil film (depending on tidal currents). OPAs form more readily in oil spills in main tidal channels, likely due to the high concentration of suspended sediment and high degree of mixing generated by strong currents. The findings of this study provide theoretical foundations for the studies of oil spills and coastal management in turbid coastal zones.