The Neurotoxicity And Mechanism Of Biochar To Caenorhabditis Elegnas

To solve the problem of global soil degradation,biochar is wildely applied for the improvement of soil quality.There are many advantages of biochar,like increasing the pH,providing nutrients,and repairing contaminated soil.However,the potential toxic substances from biochar including metallic elements,polycyclic aromatic hydrocarbons(PAHs)and environmentally persistent free radcials(EPFRs)will be inevitably released into the soil and influence soil organisms.In the current research of biochar assessments,little attention has been paid to the effects of biochar to soil animals.The model animal Caenorhabditis elegans(C.elegans),an important part of soil biodiversity,can improve the soil quality and increase plant productivity.C.elegans are gradually be used in the field of environmental science to assess the risks of pollutants recently,because of their many advantages,such as,easily culture,short-life cycle and many mutants.In this research,firstly,biochars were prepared by rice straw at the pyrolysis temperature of 200?,500?,700? and 1000?,and the contents of metallic and non-metallic elements,biochar physicochemical properties,polycyclic aromatic hydrocarbons(PAHs)and the environmentally persistent free radicals(EPFRs)were characterized.Then,soild expoure medium was used to C.elegans,and the neurobehaviors including body bends,relative move length,defecation,touch response and chemical index were observed to evaluate the effects.Finally,liquid exposure medium was used,the neurobehaviors of biochars,the washed biochars and biochar supernatants of four temperature were detected,and the content of lipid peroxidation product,Malondialdehyde,was measured to analysis the source of toxicity.Based on these,it is concluded that:(1)With the increasing of pyrolysis temperature,the biochar yield decreases,the atomic ratio of H/C,O/C and(N+O)/C declines.The highest intensity of EPFRs is biochar of 500? with the value of 5.6×10~5.(2)In the result of solid exposure,both the unwashed and washed biochar of 500? have a similar effect,namely,hormesis.Biochar supernatant has no obvious effect.EPFRs might be a reason for the neurotoxicity.(3)In the result of liquid exposure,four kinds of unwashed biochar have little effect on the neurobehaviors.The washed biochar of 700? is more toxic to C.elegans than unwashed.The metallic elements in the supernatant are unlikely to cause the toxicity.(4)The source of toxicity may from ROS produced by EPFRs and dissolved black carbon.C.elegans are subject to the stress from biochar.In conclusion,EPFRs might be one of the reason for the neurotoxicity to C.elegans,and it needs to do more different biochars'assessments by using C.elegans for affirm the risks of EPFRs.In the future,biological methods could be used to study the mechanism of biochar toxicity,and in that way,it would make biochar a better application.