Effects Of Polystyrene Microplastics On The Environmental Fate Of PAHs In Earthworm Metaphire Guillelmi And Clamworm Perinereis Aibuhitensis

Growing evidence of the existence of microplastics(diameter<5 mm,MPs)in marine and terrestrial environment have caused lots of concern recently.Due to their small size,MPs can be ingested and accumulated in organisms.Besides,due to their high specific surface area and hydrophobicity,MPs possess a strong sorption capacity of various types of hydrophobic organic pollutants.Polycyclic aromatic hydrocarbons(PAHs)are one important class of persistent and ubiquitous contaminants in the environment.Many studies have proved the sorption of PAHs by MPs,and PAHs was found on the surface of MPs in the environment.MPs can act as a vector of PAHs to organisms.Once MPs are ingested,there is a potential risk of MPs intake from the environment via intruding plastics.However,there is little researches about the effects of MPs on the environment fate of PAHs.In this study,we investigated the sorption of phenanthrene and pyrene on MPs,and studied the effects of MPs on the bioavailability of phenanthrene in soil and the environmental fate of phenanthrene on earthworm Metaphire guillelmi.We also developed on novel protocol for quantifying the bioaccumulation of nanosized MPs and PAHs in clamworm Perinereis aibuhitensis and investigated the effects of MPs on the bioaccumulation of pyrene.In soil system,a 10-day laboratory incubation study was conducted.We investigated the effects of two kinds of MPs on the mineralization of phenanthrene in two kinds of soil.Effects of MPs on the bioaccumulation,distribution,ratio of extract phase to bound residues and biodegradation of phenanthrene and its metabolites in earthworms was also detected.In addition,we tested the effects of MPs on the bioavailability of phenanthrene in soil.Our study showed that the presence of MPs,the mineralization of phenanthrene in soil was significantly inhibited,and the inhibition showed a close relationship with the loading ways of phenanthrene and the size of MPs.Earthworms accumulated phenanthrene mainly in their gut,and the addition of MPs reduced the uptak e of phenanthrene.The addition of nanosized MPs changed the ratio of extract phase to bound residues of phenanthrene and metabolites,the relatively ratio of extract phase raised.Decrease of bioavailability of phenanthrene in MPs treatment was found,we assumed that MPs may change the environmental fate of phenanthrene by lowing its bioavailability in soil system.In artificial seawater system,a novel protocol involving enzyme digestion of bentonic organisms was developed in this study.Under this protocol,91 percent of biological tissues was digested,92 percent recovery of nanosized MPs and 88 percent recovery of pyrene were achieved,and no modification occurred on nanosized MPs surface.A bioaccumulation sample was used to verify the reliability of this protocol,and the protocol was found to be efficient at detecting plastics and contaminants from clamworm tissues,an inhibition of pyrene burden were found in clamworms with the addition of MPs.By confirming the effect of MPs on the environmental fate of PAHs in organisms,this study provided scientific evidence of environmental risks of MPs and promoted new insight into studying the effects of MPs on organic contaminants.