Effect of root exudates on sorption, desorption, and transport of phenanthrene in mangrove sediments

• In the presence of root exudates, sorption of PAH was inhibited and desorption and mobility were promoted.
• Artificial root exudates enhanced PAH bioavailability, which was lower than that with the same concentration of organic acids.
• Citric acid promoted desorption and mobility of PAH more effectively than oxalic and acetic acid.

The effect of root exudates on the environmental behaviors of phenanthrene in mangrove sediments is poorly understood. In order to evaluate their influence, comprehensive laboratory experiments were performed using batch equilibrium and thin-layer chromatography (TLC) analyses. In the presence of root exudates, sorption of phenanthrene was inhibited, whereas desorption and mobility were promoted, and were elevated as root exudate concentrations increased. Among the three representative low molecular weight organic acids (LMWOAs) (citric, oxalic, and acetic acids), citric acid promoted desorption and mobility of phenanthrene more effectively than the other two. In addition, application of artificial root exudates (AREs) enhanced phenanthrene desorption, and mobility was always lower than that with the same concentration of LMWOAs, suggesting that LMWOAs predominantly affected the fate of phenanthrene in sediments. The results of this study could enhance our understanding of the mobility of persistent organic pollutants in sediment–water system.

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