Preparation Of Chinese Medicine Residues Biochar And Its Effect On Environmental Behavier Of Tetracycline

Biochar is often used for the removal of pollutants from environments and environmental remediation due to its excellent physicochemical properties.In this research,Chinese medicine residues Evodia lepta were chosen as raw materials to prepare biochar,tetracycline was chosen as the target pollutant.Evaluating the adsorption capacities of biochar derived from Evodia lepta to aqueous tetracycline by comparing with corn-stalk derived biochar.And then,magnesium/biochar composites were prepared by simple mixing and then co-prolysis of Chinese medicine residues Evodia lepta and magnesium sulphate residue.The adsorption capacities of the magnesium/biochar composite to tetracycline in solution was evaluated.Finally,pot experiments were designed by addition of magnesium/biochar composites to tetracycline polluted soils(based on the rates of 0,2% and 5% addition properties and whether to plant Ipomoea aquatic Forsk,each experimental group was named T0,T2,T5,PT0,PT2,PT5 respectively).Systematic studies were carried on the effects of magnesium/biochar composites on soil tetracycline removal,soil enzyme activies(include urease,surcase and catalase),ARGs and soil bacterial communities.In this research,antibiotic genes which related to tetracycline conclude external pump gene tetA,tetC,tetG,tetE;ribosomal protection gene tetM and enzyme modifier gene tetX).The main results are as follows:(1)Compared with the corn-stalk derived biochar which was prepared under 800?(CSBC800),the Chinese medicine residue Evodia lepta derived biochar prepared under 800?(EIBC800)had greater specific surface area,polarity and hydrophilicity.The adsorption process of tetracycline from aqueous solutions by EIBC800 and CSBC800 were affected by solution pH,biochar addition,initial antibiotic concentration,ionic strength,ambient temperature and so on.The adsorption kinetics and isotherms of tetracycline onto EIBC800 and CSBC800 were all fitted with the Pseudo-second order models(R~2 0.9540 and 0.8355)and Freundlich equation(R~2 were between 0.8991?0.9579 and 0.9736?0.9946),respectively.The adsorption process was mainly controlled by chemical reaction,and the tetracycline adsorption process was spontaneous and endothermic.In general,EIBC800 had better adsorption capacity of tetracycline than CSBC800.(2)The magnesium/biochar composite(MBC)of Chinese medicine residue Evodia lepta has greater specific surface area,pore volume and pore size than pristine Chinese medicine residue Evodia lepta derived biochar(BC)which produced under 600?.And the polarity and hydrophilicity of MBC is greater than BC,too.As solution pH increased,the adsorption capacity of MBC slightly decreased.Whereas BC's adsorption capacity increased.But at solution pH reached to 11.0,the adsorption capacity of MBC was still higher than BC did.The adsorption capacities of solution tetracycline by MBC and BC were all decreased with the solution ionic strength increased.The adsorption kinetics of tetracycline onto BC and MBC were all fitted with the Pseudo-second order models(R~2 0.9903 and 0.9598).The adsorption isotherms of tetracycline onto BC fitted Henry linear modals(R~2 were between 0.9503?0.9967),whereas MBC fitted Frendlich modals(R~2 were between 0.8907?0.9585).The adsorption thermodynamics results show that the adsorption of tetracycline in solution by BC and MBC is a spontaneous and exothermic process,and increasing the temperature is conducive to the reaction.In a word,MBC has better adsorption capacity of tetracycline than BC.(3)MBC could promote the removal of tetracycline in soil,and the efficiency of tetracycline residues removal in the soil increased with the increase of MBC addition.The degradation kinetics of tetracycline in soil are all fitted the first-order degradation kinetics equation in the groups of 0 and 2%MBC addition.And the half-lives of T0,T2,PT0,PT2 were83.51 d,16.50 d,76.17 d and 21.66 d,respectively.Whereas the tetracycline degradation kinetics of 5% MBC applied experimental group were more fitted the second-order degradation kinetics modal.In this research,compared with no addicted MBC experimental group,added 2% MBC could promote the growth of Ipomoea aquatic Forsk.But 5% MBC addition made the soil pH increased too much,which caused the Ipomoea aquatic Forsk unable to survive.The effect of MBC on urease activity in soil was related to the dosages of applied MBC.Adding 2% MBC promoted the activity of urease,while added 5% MBC inhibited the activity of urease for highly increased soil pH.Adding MBC in soil had a negctive impact on the activity of invertases.The activity of catalase was related to the rate of MBC dosages and weather or not plant Ipomoea aquatic Forsk.Statistical analysis results showed that soil's enzyme activities(include urease,invertases and catalase)were significantly correlated with MBC addiceted(P<0.05),but Ipomoea aquatic Forsk planted had no significant effect on soil's enzyme activities(P>0.05).(4)Based on the results of soil(sampled at the end of pot experimrnts)tetracycline resistance genes(tetC,tetG,tetE,tetA,tetM,tetX)by quantitative PCR(qPCR).tetG had the highest absolute abundance in every pot of experiment group,followed by the tetM,tetA and tetX;tetC and tetE had the lowest absolute abundance.MBC could dramatically increase the absolute abundance of tetG,while slightly increased the absolute anundance of tetC;The absolute abundance of tetA and tetX were all increased with the increased dosages of MBC.For unplanted Ipomoea aquatic Forsk experimental group,the absolute abundance of tetM increased first and then decreased with the dosages of MBC increased,while the absolute abundance of tetE decreased gradually.For planted Ipomoea aquatic Forsk experimental group,tetM and tetE had the opposite trendency.The difference in the abundance of tetracycline resistance genes in each experimental soil was related to the changed soil bacterial community structure after MBC applied.(5)Based on high-throughput sequencing results of total DNA from soil microbial genomes,the relative abundance of soil Proteobacteria and Bacteroidetes were increased after added MBC.While Chloroflexi,Acidobacteria and WPS-2 have the opposite results.The relative abundance of Gemmatimonadetes decreased with the increased amount of MBC addition,and Actinobacteria had the opposite trendency.The relative abundance of each genus in the soil environment is affected by the addition of MBC and its applied amount.The results of PICRUSt functional prediction analysis demonstrated that adding MBC into soils could affect the pathways of soil microbial self-basic life activities,external information transmission and so on.