Dynamic process and mechanism of crude oil release from silty intertidal sediment under different influencing factors.

Under tidal scouring, residual petroleum in the intertidal sediment after oil spills could release again, causing secondary pollution in the marine ecosystem. The current study aimed to investigate the dynamic process and principles of crude oil release from silty intertidal sediment under different influencing factors and screened for the key factors. In this paper, the fitting equations and correlation between the release amount and various factors were explored through the single-factor and orthogonal experiments. Then, the key influencing factors were selected for multi-factor fitting of the release amount. The results showed that the oil release amount rose with the increase in oil concentration, oscillation frequency, and release time, but decreased with an increase in salinity. As the pH decreased, the oil release amount increased. The relationship between release amount and concentration/oscillation frequency can be equipped by the polynomial equation, and the average R2 was 0.95 and 0.84, respectively. The release amount can be fitted by the Lagergren pseudo-second-order kinetic equation with time, with the average R2 0.89. The pH was negatively correlated with the release amount in the fresh contaminated sediment but positively correlated with the weathered one. The correlation between each factor and oil release amount was ranked (from large to small) as oil concentration, oscillation frequency, salinity, time, and pH. At last, a polynomial equation can be fitted between the key influencing factors (oil concentration and oscillation frequency) and the release amount. The results can provide a theoretical basis for predicting the secondary pollution owing to the oil re-release from intertidal sediment.