Amplified solubilization effects of inherent dissolved organic matter releasing from less-humified sediment on phenanthrene sorption

Soil/sediment organic matter (SOM) releasing with inherent dissolved organic matter (DOM) formed in solution was confirmed both in rhizosphere sediment (S) and uncultivated sediment (P) water systems, and correlations between SOM characteristics subject to sediment's humification degree and its releasing effects on phenanthrene sorption were emphasized. The sequential SOM releasing evidenced by fluorescence and H-1-NMR profiles coupled with aqueous DOM solubilization was found to make sorption kinetics atypical and sorption capacity reduced, by comparing sorption results among sediments of different pretreatments. More importantly, the tested S was proved less humified with inherent DOM rich in microbial sources than P, and DOM affinity to phenanthrene was thus weakened (K-doc values of 2.02-3.63 x 10(4) L kg(-1)), while the inhibitive effects of SOM releasing on sorption were strengthened, ascribing to the enlarged alterations of sediment characters, and particularly the amplified solubilization effects resulted from the larger proportion of soluble SOM and lower critical micelle concentration (5.66 mg L-1) of DOM. Moreover, relative contribution of DOM solubilization to the releasing effects enhanced from 0.67 for P to 0.78 for S relative to alterations of sediment characters. Consequently, mobility and exposure risk of polycyclic aromatic hydrocarbons would be enhanced in a plant-soil/sediment-water system.