Extractionof Endophytic Bacteriain Sedum Plumbizincicola And Its Rolein Cadmium Contaminated Soil Remediation

The influence of heavy metal on the safe production of agricultural products in farmland has been paid more and more attention by people,and phytoremediation is a kind of environmentally friendly,safe and effective heavy metal pollution soil remediation technology.In the process of repairing soil Cd pollution in farmland by using super-rich plant with Sedum plumbizincicola,some strengthening measures can improve the efficiency of the remediation of contaminated soil in the Sedum plumbizincicola.In this paper,the endophytic bacteria with good growth-promoting and soil Cd dissolution ability are screened for mild Cd-contaminated farmland soil in Hunan,the reinforcing effect of endophytic bacteria on the remediation of soil Cd pollution in farmland in the Sedum plumbizincicola,and the effect of organic matter on the remediation and fertilization of farmland soil under the action of microorganisms is analyzed.To achieve the"side-by-production and remediation"of soil contaminated with moderate Cd,it provides theoretical basis and technical guidance.The main result are as follows:?1?58 endophytic bacteria were extracted from the Sedum plumbizincicola,the number of different parts was root>stem>leaf;The 9endophytic bacteria initially selected were able to secrete ialystic acid?IAA?and siderohore,with the growth-promoting characteristics of nitrogen fixation and phosphate solubilization;The maximum tolerable concentration of Cd²⁺is 2.5 mM,of which S-ER7 is the most resistant,and endogenous bacteria can increase the concentration of Cd²⁺in the medium upliquid with CdCO₃ by 0.04?g/L to 2.66?g/L.Taking into account the growth-promoting index and the tolerance and solubility of Cd²⁺,four endophytic bacteria were identified as test strains,identified by16S DNA sequencing,and four endophytic bacteria were:S-ER2 for Aeromonas eucrenophila,S-EL3 for Buttiauxella,S-ER7 for Ralstonia picketti,S-ES9 for Pedobacter.?2?Four endophytic bacteria can reduce the p H of alluvial soil and reddish clay soil,and affect the Cd form in the soil.In alluvial soil and reddish clay soil,the pH of endophytic soils decreased by up to 0.11 units and 0.56 units.In soils treated with endophytic bacteria,the contents of weak acid soluble Cd and oxidizable Cd increased,and reducible Cd and residual Cd content is reduced,and the effect of different endophytic bacteria treatments on the Cd form in reddish clay soil is greater than that in fluvo-aquic soil.Correlation analysis found that the weak acid soluble Cd and oxidizable Cd in soil are negatively correlated with pH and can be reduced.State Cd and residual Cd are positively correlated with pH.?3?Endophytic bacteria can promote the remediation of Cd contaminated in alluvial soil and reddish clay soil.The reason is to improve the biomass of each part of the Sedum plumbizincicola,in which the biomass of the Sedum plumbizincicola increase significant in each treatment,on the other hand,to increase the bioavailability of Cd in the soil,to promote the enrichment of Cd in the Sedum plumbizincicola,alluvial soil and reddish clay soil,and the enrichment coefficient of the Sedum plumbizincicola to Cd increased by 49.99%to 85.30%and88.10%to 118.36%,respectively.Under the influence of endophytic bacteria,the remediation efficiency of Sedum plumbizincicola increased by up to 12.63%and 48.17%,respectively,which was better for the remediation of Cd contaminated in reddish clay soil,while S-ER2 and S-EL3 also had a good remediation efficiency of Sedum plumbizincicola in the alluvial soil.?4?Organic materials?soybean straw,sawwood chips,slag?by increasing the total amount of nutrients,to promote the growth of the Sedum plumbizincicola,and effiect the remediation efficiency of the Sedum plumbizincicola.Organic materials processing increases soil C,N,P content,improves the chemical measurement ratio of Sedum plumbizincicola C,N and P,which is beneficial to the growth of the Sedum plumbizincicola and improves its biomass.Organic material treatment reduced soil Cd effectiveness and Sedum plumbizincicola Cd content,but its reduction was less than the increase of the biomass of the Sedum plumbizincicola,therefore,the accumulation of soil Cd in the Sedum plumbizincicola increased.The total amount of soil Cd treated with sawdust and slag decreased by 0.05mg/kg and 0.04mg/kg,which improved the remediation efficiency of the Sedum plumbizincicola by9.68%and 7.42%,with significant differences,while the effect of soybean straw treatment was not obvious.