Effects Of Mushroom Residue And Their Pyrolysis Products On Phytoextraction Of Heavy Metals By Sedum Alfredii Hance And Rhizosphere Soil Characteristics

With the intensification of soil heavy metal pollution and people's attention to environmental health,the remediation of heavy metal contaminated soil by Sedum alfredii Hance has attracted the attention of many scholars.However,there is a problem of low remediation efficiency in reality.Therefore,it is necessary to strengthen the remediation.In this study,Sedum alfredii Hance was taken as the research object.Pot experiments were conducted in order to study the effects of different organic materials on phytoextraction of heavy metals by Sedum alfredii Hance and rhizosphere soil characteristics,and provides theoretical reference and technical support for the phytoremediation of heavy metal contaminated soil.Research indicates:1.The mushroom residue and its biochar both increase the soil nutrient content,and the effect of the mushroom residue is better.Tremella residue and Hypsizygus marmoreus residue increased the contents of total carbon,total nitrogen,soluble organic carbon(DOC),caustic nitrogen,available phosphorus and available potassium in the rhizosphere soil.Biochars only increased the contents of total carbon,total nitrogen,available phosphorus and available potassium.Tremella residue reduced the pH of rhizosphere soil,while both biochars increase it.The effect of organic materials on the availability of heavy metals in soil varies with the types of organic materials and heavy metals.Tremella residue increased the available Zn and Cd contents in soil,and Hypsizygus marmoreus residue reduced the available Pb content;Hypsizygus marmoreus residue biochar reduced the available Cd and Pb contents.2.Mushroom residue and its biochar increased the fresh weight and dry weight biomass of the shoot of Sedum alfredii Hance,and Hypsizygus marmoreus residue had the best effect.The effects of different organic materials on the content of heavy metals in the shoot are not the same.Tremella residue increased the content of Zn and Cd,Hypsizygus marmoreus residue reduced the content of Zn and Pb.Both biochars reduced the content of Cd and Zn,while Tremella residue biochar increased the Pb content.The mushroom residue promoted the enrichment of Cd,Zn and Pb,while biochar only promoted the enrichment of Pb,and the effect of Tremella residue was the best.3.Both mushroom residue increased the number of microbes and the activities of urease,phosphatase and invertase,and the effect of Hypsizygus marmoreus residue was better.Both mushroom residue and its biochar have improved the basic basal respiration of the soil,and the effect of mushroom residue is better.The most abundant bacterial phylum in the soil treated by control treatment(CK)and Hypsizygus marmoreus residue were Chloroflexi and Proteobacteria respectively,and the most abundant bacterial phylum of soil treated by Tremella residue,Tremella residue biochar and Hypsizygus marmoreus residue biochar were all Actinobacteri.The mushroom residue and its biochar both reduced the relative abundance of Chloroflexi.Both mushroom residue increased the relative abundance of Proteobacteria,and Tremella residue also improved the relative abundance of Actinobacteri.The effect of mushroom residue on soil bacterial community structure was significantly greater than that of biochar.4.Wood vinegar improves the content of nutrients and available heavy metals in rhizosphere soil and reduces soil pH.100 and 50 times diluted wood vinegar increased the content of total carbon,total nitrogen,DOC,alkali nitrogen and available Pb,Zn and Cd in rhizosphere soil,and the smaller the dilution ratio,the better the lifting effect.300,100 and 50 times diluted wood vinegar reduced the rhizosphere soil pH,and the smaller the dilution ratio,the stronger the effect.5.Wood vinegar significantly increased the biomass of Sedum alfredii Hance,and the value increased first and then decreased with the decrease of dilution ratio,fresh weight,dry weight and root length all reached a maximum with 100 times diluted wood vinegar.The effect of wood vinegar on the heavy metal content in the shoot of Sedum alfredii Hance was not significant,but wood vinegar significantly increased the enrichment of Cd,Zn and Pb,and 100 times diluted wood vinegar was the best treatment.6.Wood vinegar improves the activity of urease,invertase and protease in rhizosphere soil,but reduces the activity of alkaline phosphatase,and the smaller the dilution ratio,the better effect.The wood vinegar showed promotion and inhibition on the alpha diversity of rhizosphere soil bacterial community with high or low times diluted wood vinegar respectively.Shannon,observed_species and PD_whole_tree indices all reached the maximum with 300 times diluted wood vinegar.The most abundant bacterial phylum in all treated soils was Acidobacteria.The wood vinegar increased the relative abundance of the Acidobacteria,and the value increases with decreasing dilution factor.The value only reach a significant level with 50 times diluted wood vinegar.The smaller the diluted multiples of wood vinegar,the greater the influence on the soil bacterial community structure.7.In summary,Tremella fuciformis and 100-diluted wood vinegar have the best effect on promoting the enrichment of heavy metals in Sedum alfredii Hance,while Hypsizygus marmoreus residue and 300-fold diluted wood vinegar have the best effect on improving rhizosphere micro-ecological environment.