| Biochar has been widely used in many fields with the rapid development of biochar application technology,and thus widely existed in various environmental media such as soil and water.At the same time,with the deepening of research on biochar,the environmental risk of biochar is increasingly concerned.However,there are currently few studies on the risk of aquatic biotoxicity caused by biochar,and the environmental factors in the actual water environment,such as pH,DOM and the aging time,have not been reported on the ecological risk of the biochar in water.Our study is as follows:In our study,biochar（the pine needles was pyrolyzed at 500°C for 4 h）was used as the research object,and Scenedesmus obliquus（S.obiququus）was used as the test organism.We compared the effects of environmental indicators:pH,humic acid（HA）and sodium dodecyl benzene sulfonate（SDBS）on the biochar toxicity with the following endpoints,cell growth inhibition rate,chl-a synthesis inhibition rate and mitochondrial membrane potential（MMP）.The effect of aging on the biotoxicity of biochar under different environmental conditions was investigated at 32 days.In addition,the physicochemical properties of biochar,cell surface morphology,intracellular oxidative stress and the concentration of free radicals in biochar were characterized to explore biochar’s toxicity mechanism and the role of environmental factors.The results showed that biochar significantly inhibited the cell growth and chl-a synthesis of S.obiququus,and the 72 h-EC50 values were 56.2 mg/L and 127.0 mg/L,respectively.At the same time,biochar also increased the MMP and internal ROS levels of S.obiququus.pH,HA and SDBS significantly affected the toxicity of biochar on S.obiququus.It indicated that the toxicity of biochar to S.obiququus decreased with increasing pH.Meanwhile,the presence of HA and SDBS both alleviated the toxicity of biochar on S.obiququus,and the effect of HA is more pronounced.The aging of biochar under different conditions has caused different changes in toxicity.The toxicity of biochar is weakened after aging in water with pH=4,8,12 and in SDBS solution,while the toxicity is increased after aging in HA solution.The discussion on the mechanism of biochar toxicity indicates that the aggregation and adhesion of biochar on cell surfaces,the intracellular oxidative damage and the PFRs are the main toxic mechanisms of biochar on S.obiququus.pH,HA,SDBS and aging adjusted the aggregation and adhesion of biochar on cell surfaces,the intracellular oxidative stress and the concentration of PFRs to influence the toxicity by changing the physicochemical properties of biochar,such as carbon structure,functional group,surface charge.This study provided the ecotoxicity data for the study of biochar toxicity in aquatic environment,and had great significance and scientific value for the ecological risk assessment of biochar in actual aquatic environment. |
