The Remedial Effects And Mechanisms Of Potamogeton Crispus L. On Polycyclic Aromatic Hydrocarbons In Sediments

Polycyclic aromatic hydrocarbons?PAHs?are greatly persistent and hydrophobic.They would tend to adsorb on particles and accumulate in sediments,and then could pose a threat to human beings through the accumulation of PAHs in aquatic animals and food chain.Submerged macrophytes could release root exudates and oxygen into rhizosphere sediments through their advanced roots to stimulate microbial activity.Therefore,studies on phytoremediation of PAHs-contaminated sediments are of great significance.This paper selected typical submerged macrophyte Potamogeton crispus L.?P.crispus?as the tested plant,studied?1?the tolerance of P.crispus on different concentrations of PAHs in sediments,?2?the effects of different factors?PAHs concentrations,plant density and aging?on the phytoremediation of PAHs through pot and rhizonbox experiments using phospholipid fatty acids?PLFAs?analysis,redox microelectrode,modeling and other technical means,and discussed the remedial mechanisms.The results showed that?1?P.crispus could tolerate as high as 120 mg PAHs/kg in sediments,and root tip number was the most sensitive parameter to PAHs concentrations,?2?P.crispus can enhance the degradation of PAHs.With improving the PAHs concentration?8⁴8 mg/kg?and plant densities(642³530 m^-2),the dissipation increments of PAHs improved by P.crispus also increased,and the dissipation increments of pyrene in aged sediment was up to 45.9%,?3?P.crispus not only improved sediment redox potential,polyphenol oxidase activities?by7.1⁴2.1%?,microbial biomass?by 48.2¹97.8%?and degrading bacterial populations?by 24.6⁵0.0%?in sediments,but also changed the microbial community structures in sediments,?4?The results of desorption and biodegradation models showed that P.crispus improved the biodegradation activity of pyrene in unaged and aged sediments?150%and 277%,respectively?more evidently than the bioavailability of pyrene?13.1%and 73.9%,respectively?.The main conclusions of this study are?1?P.crispus could tolerate high doses of PAHs in sediments,?2?The oxygen released by P.crispus firstly changed the anaerobic environment of the sediment,and then improved the microbial activities and changed the microbial community structure,and lastly enhanced the dissipation of PAHs in sediments,?3?Compared with the bioavailability of PAHs,the microbial activity played a more important role in enhancing the biodegradation of PAHs in sediments.