A study combining a sediment-seawater microcosm with multimedia fugacity model to evaluate the effect of tidal cycles on polycyclic aromatic hydrocarbon release from sediments

Estuarine sediments are key storage sites for persistent organic pollutants (POPs), and estuaries are strongly influenced by tides throughout the year. Although much work has been done concerning on POPs release, related questions on tidal action have not been considered in the release process. Herein, polycyclic aromatic hydrocarbons (PAHs) release from sediment to seawater was investigated under tidal action by combining a tidal microcosm with level IV fugacity model. The results showed that PAHs release with tidal action was 2.0-3.5 times the accumulation of that without tidal action. Tidal action was confirmed to influence strongly PAHs release from sediment to seawater. We also quantified suspended substance (SS) in the overlying water, and an obvious positive correlation between the PAHs concentration and SS content was found. In addition, an increase in seawater depth enhanced the intensity of tidal action, and more PAHs were released, especially dissolved PAHs. Moreover, the fugacity model results showed a good fit with the experimental results. The simulated values demonstrated that the PAHs release was accomplished via two processes, rapid release and slow release. And the sediment played a key role in the fate of PAHs and was a major sink in the sediment-seawater system.

Automated summary

Tidal action significantly affects the release of PAHs from estuarine sediments to seawater. The release is 2.0-3.5 times higher compared to no tidal action. PAHs concentration shows a positive correlation with suspended substance content. Increased seawater depth intensifies tidal action and leads to more PAHs release, especially dissolved PAHs. Sediments play a crucial role in the fate of PAHs and act as major sinks in the sediment-seawater system.