Simulation of aromatic polycyclic hydrocarbons remobilization from a river sediment using laboratory experiments supported by passive sampling techniques

Resuspension of bedded sediments was simulated under laboratory-controlled conditions in order to assess the amount of polycyclic aromatic hydrocarbons (PAH) remobilized in the dissolved fraction during one short and vigorous mixing. The desorbed amount of PAH was compared to the exchangeable fraction, the total amount of PAH sorbed on the sediment particles, and the dissolved PAH amount contained in the interstitial pore waters in order to evaluate the contribution of each fraction to the total amount of PAH released. To monitor the desorption of PAH and measure low trace level concentrations, passive samplers were used in an experimental open flow through exposure simulator. Results show that for the selected sediment, a substantial fraction of sorbed PAH (69 % of the total amount) is not available for remobilization in a depleted medium. Obtained data pinpoint that over 9 days, only 0.007 % of PAH are desorbed by passive diffusion through a water-sediment interface area of 415 cm2 and that an intense resuspension event of 15 min induces desorption of 0.015 % of PAH during the following 9 days. Results also highlight that during resuspension simulation, modifications of the sediment and the water body occurred since partitioning constants of some pollutants between sediment and water have significantly decreased.