Study On The Pennisetum Americanum(L.) K. Schum Rhizosphere Micro-ecological Characteristics In Phytoremediation For Atrazine Contaminated Soil

Atrazine is one of the most widely used herbicides in agriculture for its efficient weed control and low cost.However,atrazine has been reported to be harmful to water environment,soil and biological.Phytoremediation is considered to be one of the effective and economic way of soil organic pollution remediation for low cost,saving land resources and no second pollution.Some relative researches proved that P.americanum could show better resistance to atrazine and has the potential as a remediation plant to repair atrazine contaminated soil.In the process of phytoremediation of organic contaminated soil,the interaction between plant rhizosphere and soil microorganisms is considered to be the key driving mechanism to achieve the ultimate pollutant removal.However,our knowledge of the difference of the soil microorganisms between the rhizosphere and non-rhizosphere soil of Pennisetum genus plant is still incomplete.Here,our study selected P.americanum,which is resistant to atrazine,as the test plant to carry out the research of Pennisetum americanum?L.?K.Schum rhizosphere micro-ecological characteristics in phytoremediation for low(20 mg·kg^-1)and high(100 mg·kg^-1)concentration atrazine contaminated soil.We mainly focus on the changes of soil physiochemical properties,as well as bacterial functional diversity and community structure in rhizosphere and non-rhizosphere,in order to provide the theoretical basis for improving the efficiency of phytoremediation.The main results are as follows:Effect of P.americanum on soil typical physical and chemical indexes in atrazine contaminated soil: in the initial phytoremediation,soil pH was increased at low concentration atrazine,while soil pH was decreased and soil Eh was increased at high concentration atrazine.On day 28,the pH,catalase activity and urease activity of low concentration of atrazine contaminated soil were higher than that of high concentration of atrazine contaminated soil,while Eh of the low concentration of atrazine contaminated soil was lower than that of high concentration of atrazine contaminated soil.In the two concentrations of atrazine,P.americanum can significantly change the physical and chemical properties of rhizosphere soil.On day 28,the pH,catalase activity and urease activity of rhizosphere treatment were significantly higher than that of other treatments.At the end of the phytoremediation,the pH,Eh,soil catalase activity and urease activity between rhizosphere treatments in low concentration and high concentration of atrazine had no significant difference.Effect of P.americanum on soil microbial metabolic function diversity in atrazine contaminated soil: compared with the control,low concentration atrazine increased soil significantly increased soil AWCD,Shannon,Simpson and Mc Intosh index,while high concentration atrazine decreased soil AWCD,Shannon,Simpson and Mc Intosh index on day 0.On day 28,the AWCD,Shannon,Simpson and Mc Intosh index of low concentration of atrazine contaminated and high concentration of atrazine contaminated soil had no significant difference.At the end of the phytoremediation,the AWCD,Shannon,Simpson and Mc Intosh index of rhizosphere treatment were significantly higher than that of other treatments.The AWCD and Mc Intosh index of rhizosphere treatment in low concentration of atrazine were significantly higher than that of rhizosphere treatment in high concentration of atrazine.Principal component analysis showed that rhizosphere soil of P.americanum had better ability of carbon source utilization.And the microbial community metabolic diversity of P.americanum rhizosphere soil at low concentration atrazine was higher than that of P.americanum rhizosphere soil at high concentration atrazine.Effect of P.americanum on soil bacterial community structure in atrazine contaminated soil: on day 0,the diversity of soil bacterial community structure was decreased at low concentration and high concentration atrazine,since soil microbial Chao,ACE and Shannon index of pollution treatment were significantly lower than that of control treatment.On day 28,the Chao,ACE and Simpson index of low concentration of atrazine contaminated soil were lower than that of high concentration of atrazine contaminated soil.At the end of the phytoremediation,the Chao,ACE and Simpson index of rhizosphere treatment were lower than that of other treatments and the Chao index of rhizosphere treatment in low concentration of atrazine was significantly higher than that of rhizosphere treatment in high concentration of atrazine.The above results showed that P.americanum significantly changed soil microbial community structure,reducing the diversity of bacterial communities in the root,and the diversity of bacterial communities of P.americanum rhizosphere soil in the low concentration atrazine was higher than that of P.americanum rhizosphere soil in high concentration atrazine.Furthermore,the level of classification of the genus species and OTU Venn also showed that the microbial community structure of rhizosphere soil was different from other treatments and the rhizosphere soil had some unique OTUs.These OTUs contained some microbial species which participated in soil nutrient cycling,also contained some microorganisms which can degrade organic pollutants.Principal component analysis further proved that P.americanum rhizosphere significantly influenced soil microbial community structure and different concentrations of atrazine had different influence on the bacterial community structure of P.americanum rhizosphere soil.