Ecological Effects Of Typical Alternative Of Perfluoroalkyl Substances On Wheat Rhizosphere Microorganisms

With the restricted use of traditional per-and polyfluoroalkyl substances（PFASs）in industrial production,6:2 chlorinated polyfluoroalkyl ether sulfonates（6:2 Cl-PFESA）and hexafluoropropylene oxide dimer carboxylic acids（HFPO-DA）are used as typical alternatives to traditional PFASs,respectively,for chromium plating mist suppressants and fluoropolymers.In recent years,they have been widely detected in water,soil and plant bodies and are considered to be highly persistent,bioaccumulative and potentially biotoxic.At present,ecotoxicity studies on these two new PFASs are in their infancy,and their ecological effects on soil microorganisms are still unknown.In this study,we investigated the response of wheat inter-root soil microbes to 6:2 Cl-PFESA and HFPO-DA from the perspectives of soil physicochemical properties,functional gene abundance related to soil carbon and nitrogen cycling,and changes in soil microbial community structure.A pot experiment was set up to grow wheat（Triticum aestivum L.）with 6:2 Cl-PFESA and HFPO-DA added to the soil（brown soil）to target concentrations of1,10 and 50 mg/kg,respectively,while a control group without PFASs was set up.The results of the study showed that:（1）HPFO-DA and 6:2 Cl-PFESA affected soil physicochemical properties.only high concentrations of HPFO-DA and 6:2 Cl-PFESA reduced soil CEC content.HPFO-DA and6:2 Cl-PFESA significantly reduced soil p H,NH₄⁺-N and CEC contents and increased SOM and NO₃^--N contents in bulk soils.HPFO-DA and 6:2 Cl-PFESA decreased soil p H and NO₃^--N content,while increased SOM content in wheat rhizosphere.6:2 Cl-PFESA decreased NH₄⁺-N content,while HPFO-DA increased NH₄⁺-N content.（2）The results of the abundances of functional genes involved in carbon cycling showed that HPFO-DA and 6:2 Cl-PFESA decreased the abundances of carbon sequestration genes（cbb L and cbb M）in bulk soils.Similarly,6:2 Cl-PFESA reduced the abundances of cbb L and cbb M genes,while HPFO-DA had different effects,and increased cbb L gene abundance and decreased cbb M gene.Both HPFO-DA and 6:2 Cl-PFESA reduced the abundances of soil nitrogen cycling（nir S,nir K,nos Z,AOB-amo A and nif H）genes（p<0.05）and inhibited the nitrogen cycling process.（3）HPFO-DA and 6:2 Cl-PFESA significantly reduced the relative abundance and diversity of the rhizosphere soil bacterial community.HPFO-DA significantly increased the relative abundances of Actinobacteriota,Chloroflexi,Bacteroidota,and decreased the relative abundance of Acidobacteriota.6:2 Cl-PFESA significantly increased the relative abundance of Proteobacteria.6:2 Cl-PFESA significantly increased the relative abundances of Arthrobacter and Sphingomonas,HPFO-DA significantly increased the relative abundances of Sphingomonas and Pseudarthrobacter.