Screening EE2 Degradation Bacteria And Remediation Of EE2 Contanminated Soil With Plants

EE2 is a typical environmental endocrine disruptor,which can be harmful to organisms at ng/L concentration.EE2 will enter into the soil due to sewage irrigation,runoff and the use of livestockexcrement.However,there was no study on the remediation of EE2 in soil.In this study,EE2 degradation bacteria associated with ryegrass was used to remove EE2 from soil,and the main results obtained were as follows:1.An EE2 degradation strain was screened from the farmland and the degradation conditions were optimized.The strain was cultured in liquid medium in 3 days,and the EE2 degradation efficiency of the strain reached 25%.Through the morphological characteristics of the strain and the analysis of 16SrDNA sequence,the strain was identified as Hyphomicrobium,and named Hyphomicrobium sp.GHH.Then we examined the effects of auxiliaries,carbon source,temperature,pH,and metal ions on the degradation of strain,and results showed that when the temperature of 30 ?,pH value of 7.5,joined the 10 mg/L in yeast powder and 0.1 mmol/L methanol in Mineral basal medium,the EE2 degradation rate can get to 60%after 3d.Fe³⁺ and Cu²⁺ had no significant effect on the growth of the strain at low concentration.Cr³⁺,Cr?VI?and Cd²⁺ ions all inhibited the bacteria at different degrees.2.The effects of Hyphomicrobium sp.GHH and ryegrass on remediating EE2 contaminated soil were studied.Hyphomicrobium sp.GHH was inoculated into the EE2 contaminated soil,which increased the biomass of ryegrass and improved the extraction efficiency of EE2.When the plant grew 42d,the transport coefficient?TF?and bioconcentration factor?BCF?were 0.062 and 30.48 respectively.The TF and BCF of the B+P treatment were 0.318 and 86.67 respectively,which increased 4.13 and 1.84 times than P.The results showed that after 28 days,the plant-microbe remediation technology removed 92%EE2 from soil;and after 42 days,the removal efficiency of EE2 was 99%.Hyphomicrobium sp.GHH combined with ryegrass can effectively remove the EE2 from soil.3.The effects of heavy metal Cd on removing EE2 by Hyphomicrobium sp.GHH and ryegrass from soils were studied.The results showed that the root length in the P and B+P treatment increased 1.97%and 7.36%respectively than C.Soil Cd concentration at 5 mg/kg had no significant influence on the shoot dry weight.However,Cd concentration at 20 and 80 mg/kg significantly inhibited the growth of the ryegrass.As the concentration of Cd increasing,the content of EE2 in ryegrass root and shoot reduced.The access of degrading bacteria changed the root environment of the plant and promoted the growth of plants,thus improving the uptake of EE2 by ryegrass.The change of urease activity in soil and microbial biomass carbon content under different treatments was studied,and the results showed that the 5 mg/kg Cd increased soil urease activity and microbial biomass carbon content.When Cd concentration was greater than 20 mg/kg,the soil urease activity and microbial biomass carbon content gradually reduced.While the growth of urease activity and microbiological carbon content can be significantly improved by planting ryegrass and inoculating strain.With the increase of Cd concentration,the content of Cd in ryegrass increased.Inoculation Hyphomicrobium sp.GHH improved the extraction of Cd by ryegrass.When the Cd concentrations were 5,20 and 80 mg/kg respectively,the contents of Cd in root increased by 88.14%,33.81%and 7.66%,and the contents of Cd in shoot increased by 46.91%,18.49%and 6.34%.After 28 days,When the concentrations of Cd was,the removal rates of EE2 from was 89%,80%and 71%respectively from the soil with Cd concentration of 5,20 and 80 mg/kg,and the extraction efficiency of Cd were 0.69%?0.44%and 0.39%respectively..According to the study,Hyphomicrobium sp.GHH combined with ryegrass can effectively remediate the Cd-EE2 compound contaminated soil.