Adsorption Characteristics And Mechanism Of Atrazine In Rhizosphere And Non-Rhizosphere Soil Of Pennisetum

Atrazine is a commonly used herbicide in the soil of northeast China's farmland.When applied to farmland,atrazine will pollute the soil environment and even the water environment.The current research on phytoremediation of atrazine has a lot of,the existing research proves,pennisetum with repair of atrazine contaminated soil,but the event about pennisetum grassroots effect and rhizosphere of atrazine adsorption mechanism is unclear.This selection test for pollutant atrazine,pennisetum as repair plant,analysis the differences of basic physical and chemical properties between pennisetum of rhizosphere and non rhizosphere soil,study on the atrazine adsorption characteristics in the pennisetum of the rhizosphere soil and non rhizosphere soil;At the same time using fluorescence spectroscopy technology,explore the atrazine adsorption effect of the rhizosphere soil and rhizosphere soil and the differences of adsorption.Relevant studies are expected to provide basic information for better understanding of the environmental behavior of the pollutants in the process of remediation of atrazine contaminated soil.In this experiment,the soil was planted with pennisetum for 60 days.The test results showed that the rhizosphere nutrition?nitrate,ammonia nitrogen,total phosphorus,available phosphorus?levels were significantly higher than those of non-rhizosphere soil,and rhizosphere soil cation exchange capacity and total organic carbon content were significantly higher than that of non rhizosphere soil,rhizosphere soil pH lower than non rhizosphere soil.The results of adsorption kinetics test showed that atrazine reached adsorption equilibrium within 32 hours.in the adsorption process of atrazine on two soils were well described by the Pseudo-second-order model fitting.In addition,the atrazine adsorption rate constant K₂ in two types of soil were 0.026 and0.023 kg·?mg·h?^-11 respectively.The results show that the adsorption capacity of therhizosphere soil was better than that of the non-rhizosphere soil.In the study of isothermal adsorption experiments,it was found that for the same concentration of atrazine solution(1³0mg·L^-1),the adsorption amount of atrazine was always higher than that of non-rhizosphere soil.The two soils were used by the Freundlich model Langmuir model fitting.it was found that were well described by Freundlich model fitting.Isothermal adsorption model of K value on behalf of the adsorbent adsorption capacity for pollutants,whether in the Freundlich model or in the Langmuir model of rhizosphere soil K value was always greater than the non-rhizosphere soil,showed that the rhizosphere soil of atrazine adsorption ability was stronger than the non-rhizosphere soil.Adsorption thermodynamics of atrazine on two soils at 15?,25?,and 35?,and the results showed that atrazine adsorbed on the rhizosphere soil and non-rhizosphere soil of Pennisetum.Thermal reactions occur spontaneously,and the increase in temperature favors the adsorption.In the leaching test,the leaching property of atrazine in two soils was that the non-rhizosphere soil was larger than the rhizosphere soil,and the leaching property was stronger in the non-rhizosphere soil.Applied on the surface of the soil column 1 ml 500 mg·L^-1 of atrazine solution,in the rhizosphere soil column atrazine of residual rate was 80%,and in the non-rhizosphere soil column in the residual rate was only 45%,the rhizosphere soil in leaching process of atrazine adsorption reduces the leaching rate of atrazine.According to the three-dimensional fluorescence spectra and synchronous fluorescence spectra,the dissolved organic matter?DOM?of both soils contains materials similar to humin.As the concentration of atrazine increased from 0 mg·L^-1 to 30 mg·L^-1,the fluorescence peaks of both DOM decreased significantly in the three-dimensional spectrum,In synchronous fluorescence spectrum,the quenching speed of rhizosphere soil DOM was 1.5 times that of non-rhizosphere soil,two of the DOM fluorescence peak were significantly decreased,two peak intensity of fluorescence quenching percentage were 79.03%and 83.64%respectively,the data show that DOM combined with atrazine of capability in the rhizosphere soil was better than in the non-rhizosphere soil,the combination of two kinds of DOM and atrazine after quenching process are mainly static fluorescence quenching;the atrazine binding constant K_A of the non-rhizosphere and rhizosphere soil of DOM were 2.7×10⁴ L·mol^-1and 3.2×10⁴ L·mol^-1,respectively.It was shown that the DOM in both soils exhibited good atrazine binding capacity,and the DOM in the rhizosphere soil was stronger than that in the non-rhizosphere DOM.FTIR spectra showed that the DOM of the rhizosphere soil had three new stretching peaks at 665 cm^-1,825 cm^-1 and 2372 cm^-1than the DOM of the non-rhizosphere soil,which corresponded to the C-H stretching,aromatic C=C ring structure and Si-H,respectively.The C=C ring structure and the increase of Si-H functional groups,these groups belong to lipophilic groups.Pennisetum will release root exudates to the soil environment through the roots,regulate the characteristics of the soil,and also cause differences in the two soils and the extracted DOM,resulting in different adsorption capacities of atrazine for the two soils.