The Effect And Mechanism Of Alfalfa On The Restoration Of Phthalate Contaminated Soil Were Investigated

With the large-scale use of plastic products and agricultural films,the pollution of phthalic acid esters in soil is more and more serious,and it is more and more important to protect the soil environment and to realize the sustainable utilization of soil resources.This paper expounds the effect of phthalic acid ester on plant metabolism,understanding the transport and metabolism of phthalates in plants,mastering the micro-ecological characteristics of rhizosphere under polluted soil,and is an important scientific problem in remediation of contaminated soil,which will provide a theoretical basis for the pollution of phthalic acid esters in soil.The main results of this study were:(1)Through GC-MS,a total of 314 alfalfa root metabolites were detected,including carbohydrates,acids,esters,alcohols and amines.The results were analyzed by PCA and orthogonal partial least squares method(discriminant analysis),and 50 different metabolites were detected.Under the DEHP stress of low concentration and high concentration,the carbohydrate substance secreted by root system decreased and the effect of low concentration DEHP on fatty acid metabolism was not significant,but the content of fatty acid increased significantly under high concentration DEHP stress.Under DEHP stress of low concentration and high concentration,the content of flavonoids 4’5-dihyrroxy-7-methoxyisoflavone decreased.The content of intermediate metabolites neohesperidin in flavonoids biosynthesis pathway decreased.(2)Alfalfa had a certain absorption ability to DBP,and in the first 96 h to DBP the absorption ability was strongest.The metabolism of DBP occurs mainly at the root of alfalfa,and a small portion was transported to the ground to be metabolized.The metabolites of DBP were mainly PA and MBP,and alfalfa was mainly metabolized DBP as PA.The distribution of PA in the subcellular components of Alfalfa were asfollows: Underground organelles > soluble components of the underground > soluble components in the ground,and no detectable parts in the cell wall.The distribution of the subcellular components of MBP in Alfalfa were as follows: Underground organelles > underground soluble components > underground cell walls >aboveground organelles > soluble components on the ground > floor cell walls.(3)The planting of alfalfa accelerated the degradation of DEHP in the soil,the fastest degradation rate in 30 d,and the gradual degradation after 60 d.The degradation rate of DEHP in the soil of alfalfa planting were 95% and 90%,respectively.The overall tendency of the DEHP degradation of the soil in the treatment of alfalfa and alfalfa was as follows: Near root layer > root growth layer > distal root layer.(4)Planted alfalfa and do not plant soil samples in the dominant had Proteobacteria,Acidobacteria,Actinobacteria,Chloroflxi,dominant bacteria were Pseudomonas,Massillia,Azonhydromonas,Saprospiraceae.The bacterial community diversity in the test soil increased rapidly in the first 30 days,and the bacterial community in the soil of alfalfa cultivation was richer than that of alfalfa.With the prolongation of culture time,the diversity of bacterial communities changed little.The flora of the soil samples from alfalfa rhizosphere was similar,and there was no obvious difference.