Adsorptive removal of polycyclic aromatic hydrocarbons by detritus of green tide algae deposited in coastal sediment

Rare information is available on the adsorptive removal of polycyclic aromatic hydrocarbons (PAHs) in the presence of algal detritus deposited in the coastal sediment during the outbreak of the green tide. The adsorptive removal of typical PAHs by Ulva prolifera (U. prolifera) detritus was firstly investigated since the algal detritus was of great importance for the biogeochemical cycle of coastal contaminants. The results showed that equilibrium adsorptive capacities of naphthalene, phenanthrene and benzo[a] pyrene on the U. prolifera detritus were 1.27, 1.97, and 2.49 mg kg, respectively, at the initial concentration of 10 μg L. The in situ monitoring using laser confocal scanning microscopy confirmed the adsorptive removal of PAHs by U. prolifera detritus. The adsorption of these PAHs was highly pH-dependent. The increase in salinity led to the increase in naphthalene removal rate, while the salinity showed scarce influence on the removal of phenanthrene and benzo[a] pyrene. There was a good linear relationship (R ≥ 0.9892) between the removal efficiency of PAHs and the initial concentration of PAHs. Slow desorption kinetics and low desorption rate (<16%) indicated that the adsorptive removal of PAHs could be benign to the environment. These findings demonstrated that the occurrence of green tide could provide a new natural remediation approach for contamination of PAHs through the adsorptive removal by the detritus of green tidal algae deposited in the coastal sediment.