Effects of root exudates on the mobility of pyrene in mangrove sediment-water system

Mangrove ecosystems receive substantial polycyclic aromatic hydrocarbons (PAHs) from human activities. The mechanism of transport and translocation of PAHs within mangrove sediment is not well understood. In the present study, the mobility of pyrene in two typical mangrove sediments was studied using soil thin layer chromatography (TLC). The mobility of pyrene in the sediments displayed an inverse trend with organic carbon (foc) content. As one of the important fraction in sediment organic matter pool, the influence of root exudates on adsorption of pyrene within the tested sediments was also evaluated. In particular, root exudates significantly enhanced the bioavailability and mobility of pyrene in the sediments. The effectiveness of root exudates in promotion of pyrene mobility follows an order: citric acid > oxalic acid > malic acid > artificial root exudates (ARE). In addition, mobility factors of pyrene from root exudate treatments were significantly higher than the value determined in the control, and the magnitude of mobility factor (Rf) showed a positive correlation with root exudate concentrations. Results of this study could promote our understanding of the mobility of PAHs in contaminated mangrove sediments.