| The bioremediation of radioactive polluted water has a good application prospect,but the key bottleneck in real application and promotion is how to improve the absolute enrichment and efficiency of plants in the repair process.With the separation and selection of microorganisms which can enhance plants'adsorption efficiency and phytoremediation ability in the natural environment,this research has constructed a highly efficient plant-microbial symbiotic repair system to stengthen that the actual remediation capacity of radioactive contamination is one of the highlights in the bioremediation field.In this paper,hydroponic experiments were conducted to explore the effects of microorganisms on phytoremediation of uranium?U?-contaminated water.Under the single factor U-pollution,the effects of three kinds of microorganisms?Aspergillus niger,Bacillus mucilaginosus and Bacillus subtilis?on biomass,fluorescence physiology,and U enrichment characteristics in Eichhornia crassipes and the effects of microbial mixing treatment on its biomass and U enrichment characteristics were studied.Through comparing high quality combinations under electric field treatment,the dominant repair mode was filtered and field repair verification was performed.The research results are as follows:Under U stress,all the three kinds of microorganisms could promote the biomass,PSII system activity and U enrichment ability of Eichhornia crassipes.When the U concentration was 25 mg·L-1,Bacillus subtilis and Bacillus mucilaginosus respectively increased the dry weight of Eichhornia crassipes'roots,stems and leaves by 34.7%and 60.5%,which also increased the U enrichment concentration of Eichhornia crassipes'stems and leaves and the U enrichment concentration of Eichhornia crassipes'roots by 14.1%and 36.6%respectively.The U enrichment of whole plants was most significantly increased by Bacillus mucilaginosus?51.8%?which is up to 3.706mg.However,all the three microorganisms would reduce the photosynthetic performance of Eichhornia crassipes.At the same time,the activity of the antioxidant enzyme system of Eichhornia crassipes was promoted by Bacillus mucilaginosus and Bacillus subtilis and inhibited by Aspergillus niger.The highest TF of Eichhornia crassipes under the action of Bacillus subtilis was 1.192,and the highest BCF was 272.8 under the action of Aspergillus niger.All the four types combination of mixed microorganisms had a certain promoting effect on the roots of Eichhornia crassipes.Some of them could improve Eichhornia crassipes'U tolerance.The highest growth rate of roots'dry weight?75.8%?appeared in the combination of Bacillus subtilis and Aspergillus niger.However,the combination of mixed microorganisms would reduce the enrichment ability of the roots of Eichhornia crassipes,and would promote the.When the concentration of U was 25mg·L-1,the enrichment concentration of stems and leaves was the most obvious?31.3%?in the combination of Bacillus subtilis and Bacillus mucilaginosus.U total extraction was the most significant?16.2%?when combined with Bacillus subtilis and Aspergillus niger,which had reached25.412 mg.All the mixed microbial combinations could improve the transport capability of Eichhornia crassipes in the medium and high U concentration whereas at low U concentrations,the transport coefficient was the highest,reaching 0.28.The high quality combinations had different proper U concentration range.When treated with single Bacillus mucilaginosus at low concentrations,the biomass,antioxidant enzyme system activity,PSII system activity and the U enrichment ability of Eichhornia crassipes were stronger,but at the same time the cell membrane of Eichhornia crassipes was also more stressed.At the middle concentration of U,the Eichhornia crassipes mixed with Bacillus subtilis and Aspergillus niger was more prominent.At high U concentration,the stress increased and there was no significant difference in biomass between the two groups.The activity of the antioxidant enzyme system of Eichhornia crassipes was higher under the single treatment of Bacillus mucilaginosus.The activity of PSII system and U enrichment ability of Eichhornia crassipes were better under the combined treatment of Bacillus subtilis and Aspergillus niger.On the other hand,the photosynthetic pigment content of Eichhornia crassipes'leaves under single treatment of Bacillus mucilaginosus was higher than that of Bacillus subtilis and Aspergillus niger at all concentrations.The electric field had a double-sided effect on the combined system.Under certain conditions,the biomass,the activity of antioxidant enzyme system,the activity of PSII system and the light and pigment content of leaves of Eichhornia crassipes were promoted,but they were generally suppressed.The effect of electric field on the degree of stress on the cell membrane was mostly reduced.Moreover,at the same U concentration,compared with two high quality groups,the effect of electric field on Eichhornia crassipes U enrichment ability showed that it could promote the lower group's U enrichment ability and inhibit the higher group's U enrichment ability.In the test,the total extraction amount of U was 13.834 mg,which was obtained by mixing microorganisms and electric field treatment at the 15 mg·L-11 U concentration.In the field restoration,Bacillus mucilaginosus increased Eichhornia crassipes'root dry weight by 59.1%and stem and leaves'dry weight by 58.3%respectively,which also significantly enhanced the enrichment ability of Eichhornia crassipes for U,Mn and As heavy metals.The total extraction amount increased by 24.6%,275.8%,and 80.0%respectively,reaching 9.421mg,25.109mg,and 0.360mg. |
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