Leaching Effect And Mechanism Of Hydroxamate Siderophore On Heavy Metal-polycyclic Aromatic Hydrocarbon In Soil

Soil leaching technology has been receiving widespread attention in soil remediation for its simplicity and economy,but the current commercial eluents can barely deal with HMs-PAHs co-contaminants in soils at the same time,moreover,poor adaptability and potential ecological risks also seem to be insurmountable obstacles.Exploring a novel green efficient bioeluant is a key to promote the sustainable and healthy development of leaching technology.Thus,this study investigated the synergistic leaching effectiveness for HMs and/or PAHs from actual agricultural and industrial contaminated soils by HDS and explored the underlying molecular mechanism.More importantly,the possible ecological risk of residual HDS and its complex with HMs and/or PAHs in the soil after leaching was also analyzed carefully.The results of this dissertation were listed as follows:（1）HDS-producing strain（Pseudomonas fluorescens HMP01）was isolated from HMs-PAHs co-contaminated soil,which has been deposited in the Center for Type Culture Collection of China（Accession No.CCTCC M 20191131）as a patent strain.The 16S rRNA gene sequence has been deposited in Gen Bank（Accession No.MN689650.1）.（2）Molecular structure of HDS and its molecular mechanism about the interactions with cationic HMs or PAHs were explored.HDS has special chemical structures such as hydroxamic acid and dihydroxy quinoline chromophore.The oxygen-containing functional groups（e.g.,carbonyl and hydroxyl）of HDS can chelate with cationic HMs,and the hydrophobic cavity formed by non-polar functional groups（e.g.,benzene ring and long carbon chain）of HDS can solubilize PAHs.（3）Interaction mechanisms of HDS with cationic HMs and/or PAHs were dominated by cation-πinteraction and chelation.The spatial configuration shrinked after HDS chelated with cationic HMs,resulting in an increased hydrophobicity,and thus improving solubilizing ability of PAHs.The chelation ability of cationic HMs was enhanced after HDS solubilized PAHs,which was due to the cationic-πinteraction between a large number of benzene rings and heavy metal ions.（4）HDS could synergistically remove cationic HMs and PAHs in the actual co-contaminated soil and the ecological function and nutrient structure did not change significantly after leaching.The elution amounts of Cd²⁺,Pb²⁺,Hg²⁺,Cu²⁺,Zn²⁺,Ni²⁺,and phe reached 27.5,110.4,6.9,477.7,10606.9,137.4,and 90.2 mg/kg HDS.The contents of catalase,alkaline phosphatase,urease,phospholipid fatty acid,available nitrogen,available phosphorus,available potassium,exchangeable calcium,and exchangeable magnesium in the soil fluctuated within an acceptable range after leaching by HDS.Also,the biodiversity and bacterial community structure in soil after leaching were not affected indicated byα-diversity index and PCoA analysis,except the community abundance of Firmicutes and Bacillus increased.