Bioaccumulation,Distriburion And Toxicity Of Graphene In Earthworm And Limnodrilus Hoffmeisteri

As a new nano-material in 21 century,graphene is a flat monolayer of carbon atoms packed into a two-dimensional lattice,which is much better than other nano-material on the structure and properties.It attracts popular attention intensively and the quite comprehensive research on synthetic methods,property,potential applications of graphene has been investigated since it was fist isolated in 2004.It is inevitable that graphene will enter the environment with increasing usage in consumer products involving graphene,and could have a significant impact to organisms in environment.But the research about the ecological risks of graphene remains a relatively unexplored field or an initial stage.Thus,it is very important to conduct system investigation of the graphene behavior in different environmental media as well as the ecological risks to organisms in the environment.This research selects ¹⁴C-graphene as an imaginary pollutant.The purpose of our work is to evaluate the toxicity of graphene to Limnodrilus hoffmeisteri,Eisenia foetida,Metaphire guillelmi and Daphnia magna.In this study,we explore the effects of graphene on aquatic organisms and soil organisms after graphene entering the environment,and make a preliminary assessment of the ecological risks of graphene.And the major findings are as follows:?1?In this study,a novel synthetic method for producing ¹⁴C-labeled graphene was devised.This method can synthesize a kind of high purity 4-layer graphene which has little O,H?<5%?.?2?The bioaccumulation and distribution of graphene in earthworms were investigated,for evaluating the risk of graphene on soil ecosystem.Eisenia foetida and Metaphire guillelmi were selected to be the testing organisms.A modified process employing ¹⁴C-labeled methane was used to synthesize graphene.The labeled graphene was then spiked to soil sample?1 ?g graphene in 1 g soil?.The results showed that the graphene concentration in earthworm was 0.17 ?g/g organisms dry mass after exposure for 9 days in spiked soil.And graphene can only be accumulated in the intestine,but not cross the intestinal wall.?3?The ¹⁴C-labeled graphene was added to artificial freshwater and the uptake of graphene by Limnodrilus hoffmeisteri was assessed.After exposure for 36 h,the graphene concentration in the organisms reached a peak.And the enrichment of graphene was increased with increasing concentration of graphene in artificial freshwater.In the experiments,a number of proteins secreted by Limnodrilus hoffmeisteri was observed,and there was interaction between these proteins and graphene:Protein was attached to the surface of the graphene,and facilitating its dispersion in solution;Moreover,the particle size of graphene changes from 400 nm to about 150 nm.?4?The ¹⁴C-labeled graphene which was modified by Limnodrilus hoffmeisteri was added to artificial freshwater and the uptake of graphene by Daphnia magna and the dispersion of graphene were changed.These results suggested that the behavior of graphene in water environment is very complex.Therefore,the assessment of the ecological risks of graphene in the water environment is still necessary.