Role of salinity in the multiphase redistribution of polycyclic aromatic hydrocarbons (PAHs) in sediment suspension

Sediment suspension in estuarine environment was simulated with particle entrainment simulator device to investigate the phase redistribution characteristics of polycyclic aromatic hydrocarbons (PAHs). The main focus was laid especially on the role of salinity gradient in the static and dynamic release behavior of PAHs via keeping the consistent of other factors (i.e., hydrodynamic condition and sediment component) in the whole experiment. Results showed that salinity facilitated the accumulation of dissolved and particle-bound PAHs in overlying water in sediment pre-standing and suspending period, which certainly increased the adverse ecological effect of PAHs in sediments. The most beneficial value of salinity for PAHs release from sediments was about 20 ‰. Salinity had more significant impact on the release behaviors of 2+3 ring PAHs than other individual PAHs species. Salinity significantly changed the diameter and suspending status of flocs via adsorption and charge neutralization, and thus affected the existing status of PAHs in the overlying water. Based on quantitative calculation, salinity was found to have more significant influence on the release of PAHs than the pre-fixed hydrodynamic force.