Static and dynamic sorption of phenanthrene in mangrove sediment slurry

The static and dynamic sorption of phenanthrene (Phe) in three types of mangrove sediment slurries (sandy, silty and muddy) were described by three models, namely linear model, Freundlich adsorption isotherm model and Langmuir adsorption isotherm model. The Freundlich adsorption isotherm was the best model to describe the static sorption behavior of Phe in mangrove sediment slurry with the regression coefficients ranging from 0.96 to 0.99. In static sorption, the sorption capacity and sorption intensity were reduced with the inoculation of Sphingomonas, a PAH-degrading bacterial isolate, suggesting that the inoculum even though inactive and/or dead would enhance bioavailability of Phe. On the other hand, the static sorption of Phe was significantly enhanced at high salinity (20 ppt) while no difference was found at low salinities ranging from 5 to 15 ppt. During the dynamic sorption process, i.e. with biodegradation by indigenous microorganisms and the inoculation of Sphingomonas, linear regression was the most suitable model to describe Phe sorption behavior. The partition coefficient α was the highest in silty sediment, followed by sandy sediment and the muddy sediment had the lowest value. These results indicated that the sorption behavior of Phe changed from non-linear to linear when biodegradation took place and the silty mangrove sediment slurry had the highest sorption affinity.