Toxic Effects Of Biochar On Caenorhabditis Elegans And Its Toxic Sources

Biochar is the carbon-rich product of pyrolysis of biomass with limited oxygen.It has attracted extensive attention and been widely applied in carbon sequestration,improvement and remediation in water and soil,because of its high adsorption sites and activated functional groups.However,the endogenous contaminants of biochars may be potentially toxic to organisms in the environment.The neurobehaviors and malondialdehyde(MDA)of Caenorhabditis elegans(C.elegans)were investigated after 24h-exposed in biochars,washed biochars and extracted supernatants of five biochars,which derived from pine biochar at the pyrolysis temperature of 200℃,500℃,700℃,1000℃ and rice straw biochar of 500 ℃.Combined with the physicochemical properties and the contents of metallic,non-metallic elements and environmentally persistent free radicals(EPFRs)of biochars,washed biochars and extracted supernatants,the toxicity of biochars on C.elegans were characterized and evaluated.The main results are as follow:(1)With the increasing pyrolysis temperature,C content increased while the H/C,O/C,and(O+N)/C atomic ratios were decreased.The highest intensity of EPFRs is the pine biochar of 500 ℃,while the intensity the biochar after washing was decreased.(2)The biochar and washed biochar made by pine were more toxic to C.elegans than extracted supernatant which don’t have no significant effect on C.elegans.The heavy metal contents are lower than the standard.Pine biochar and washed biochar of 500 ℃ and 700 ℃ are more toxic than 200 ℃.(3)Rice straw biochar of 500 ℃ and its washed biochar are more toxic to C.elegans than extracted supernatants,and biochar is the most toxic one.EPFRs may be the main cause of oxidative damage to C.elegans because it can induce ?OH.(4)Compared rice straw biochar with pine biochar,the toxicity of biochar to C.elegans is related to the intensity of EPFRs,instead of its physical and chemical properties.In general,EPFRs may be one of the sources of toxicity of C.elegans.In this study,C.elegans is used to assess the toxicity and potential sources of biochar,which provided an important basis for the application of biochar.