Study On The Remediation Process And Response Mechanism Of High Concentration Complex Heavy Metals Contaminated Soil By Sedum Alfredii

Heavy metals(HM)in soil can not only affect soil properties and ecological functions,but also have an impact on plant growth and harm the human body through the food chain.Low cost,high environmental friendly phytoremediation has become a research hotspot of HM contaminated soil remediation.As one of the typical hyperaccumulating plants,S.alfredii has been proven to be used for the remediation of Zn and Cd contaminated soil.However,the remediation process and response of high concentration complex heavy metals(HCCHMs)with three or more HM are not yet clear.This study utilized S.alfredii to remediate soil contaminated with HCCHMs such as Cu,Zn,and Cd.By analyzing the distribution of HM and the characteristic indicators of plants and microorganisms,the remediation process and response mechanism of S.alfredii on HCCHMs contaminated soil were explored.The main research conclusions are as follows:S.alfredii has a good remediation effect on soil contaminated by HCCHMs,and basically does not have toxic reactions.In the process of remediation of soil contaminated by HCCHMs which include Cu,Zn,and Cd,S.alfredii can promote the accumulation of HMs from non rhizosphere soil to rhizosphere soil,and the absorbed HMs are mainly concentrated in roots and leaves;In addition,S.alfredii not only benefits the removal of Zn and Cd from the soil,but also has no impact on its physiological characteristics.Instead,it increases the chlorophyll content of the leaves,thereby enhancing their photosynthesis.HCCHMs affected the soil native bacterial community of S.alfredii with high resilience,but they had some HMs remediation functions.HCCHMs significantly affects soil bacterial diversity and community structure,but soil bacterial diversity can increase rapidly and form many dominant phyla,at the same time,the Proteobacteria in the dominant phylum enhance microbial metabolism primary functional abundance,and promote the expression of signal molecule synthesis enzymes in partial quorum sensing,regulating EPS production to chelate HMs;In addition,soil bacteria can also synthesize cysteine by promoting the serine → cysteine pathway,favoring the intracellular complexation of HMs.The soil native fungi of S.alfredii have high resistance to HCCHMs,and have a certain potential for HMs remediation.Under the influence of HCCHMs,the diversity and community structure of rhizosphere fungi changed significantly,but there was no significant change in non rhizosphere fungi;The abundance of fungi such as Ascomycota and Basidiomycota that have HMs remediation effects increased;The metabolic type of fungi is gradually transitioning from pathotroph to pathotrophsaprotroph.At this time,the ability of the fungus S.alfredii to provide nutrients to promote its growth is improved,which is beneficial for S.alfredii to repair HMs soil.