Study On Ecological Restoration Technology Of Rare Earth Minng Wasteland And Microbial Degradation Of Chlortetracycline Secondary Contamination

On the one hand,the study focused on the evaluation of soil quality in the process of remediation of rare earth mine wasteland and took the abandoned land of rare earth mine in Pingyuan County of Meizhou as the research object and included two field trials,the mountain top and the mountain foot.Then Single technologies organic fertilizer or Composite technology combined with other modifiers were adopted to repairing and planted leguminous plants for greening.In the aim of screen suitable technology,fertilizer index was tested to evaluate the repair effect.On the other hand,concerned about the secondary pollution of tetracycline antibiotics caused by the long term application of organic fertilizers in the soil improvement,this study screened the chlortetracycline-degrading strains from oxidation ponds in a farm,from the chromatographic conditions,extraction solvent and elution volume.the long-term application of organic fertilizer is not only improve the soil but also cause tetracycline antibiotics contamination problems.As chlortetracycline-degrading strains were screened from the oxidation pond in a certain farm,this paper optimized a detection method for chlortetracycline from chromatographic conditions,solvent extraction,and elution volume.To optimize the detection method of chlortetracycline and to study the degradation performance of chlortetracycline-resistant strains,in order to obtain a soil remediation technology that is highly efficient and harmless.This study has achieved the following results in screening suitable organic compound-based composite repair technologies:1)The results of the fertility indicators and individual fertility indices of mountain top were analyzed,and comprehensive fertility evaluations were conducted.According to the results of the fertility indicators,whether the single organic fertilizer technology or the combination with other technologies all can play a better role after sustained restoration in a relatively short period of time.According to the individual soil fertility index,the comprehensive fertility evaluation was conducted,the soil fertility under different remediation techniques in the area without the alien earth soil improving technology reached level II?general?,while the soil fertility of control was still in level III?poor?,and about the same technique,there was no significant difference between the area with the alien earth soil improving technology and the area without the alien earth soil improving technology.This indicated that the effect of these technologies could be presented in short time and can be maintained for a long time,and except in the area with the alien earth soil improving technology after continuous restoration for 12 months,the others wre relatively better than the single technology in the combination technology,but they did not rach the significant level.It was also found that the soil fertility index of control in the area with the alien earth soil improving technology also reached Grade II?general?after continuous restoration for 4months,while only reached III?poor?after continuous restoration for 12 months.This indicated that the alien earth soil improving technology could play a better role in short time.but the soil improvement effect was not obvious in the area based on the alien earth soil improving technology and combined with other technologies.2)The results of the fertility indicators and individual fertility indices of mountain foot were analyzed,and comprehensive fertility evaluations were conducted.According to the results of the fertility indicators,whether the single organic fertilizer technology or the combination with other technologies can play a better role after sustained restoration in a relatively short period of time.According to the individual soil fertility index,the comprehensive fertility evaluation was conducted,soil fertility in this region after the different technologies were continuously restored was at Grade II?general?,while the soil fertility of the control was still at Grade III?poor?.This indicated that each technology can show good improvement effect in the short time and can be maintained for a long time,and in addition to the regreening of the sword beans that have been improveed for 4 months,other combinations were significantly better than single technology.This research has achieved the following results in the study of microbial degradation of secondary pollution of chlortetracycline:1)The sludge collected from the oxidation pond in a certain farm was acclimated and screened with MSM medium containing a certain concentration of chlortetracycline,and chlortetracycline degrading strains F3 were obtained after isolation and purification.According to gram staining,physicochemical identification and phylogenetic analysis,strain F3 was initially identified as Acinetobacter baumannii.2)A quantitative method for the determination of chlortetracycline in MSM medium by HPLC was established.The sample was mixed with equal volum of 0.1 mol·L^-1 Na₂EDTA-Mcllvaine buffer and extracted by ultrasonic for 30 min.The supernatant was collected after centrifugation and the passed through an activated HLB cartridge and finally eluted with 1/5volume of methanol.The column to be tested was E clipse XDBC18?4.6 x 250 mm,5?m?,phase A was 0.1%aqueous formic acid,phase B was V?methanol?:V?acetonitrile?=2:3,V?A?:V?B?=2:1,flow rate is 1 mL·min^-1,column temperature is 35°C,injection volume is10?L,and can be detected by the UV at 375 nm.The peak of the element is completely separated from other substances,and the retention time of chlortetracycline is 4.9-5.0 min.In the concentration range of 0.1-10 mg·L^-1,the R² of the chlortetracycline standard curve was 0.9997.3)The degradation kinetics of strain F3 and its growth and proliferation(OD₆₀₀)were studied and found.After the addition of strain F3,the degradation of chlortetracycline significantly accelerated,and reached 95.57%at 20 h,but the degradation of hydrolysis process reached 30.47%,and the degradation of chlortetracycline reached 99.04%at 35 h,but the degradation of hydrolysis process only 57.52%at 35 h.was degraded by hydrolysis.Strain F3 grew rapidly in agaromycin-containing 10-PMSM medium and reached its maximum growth density at 5 h,after which the bacterial density remained stable,but biodegradation continued.The degradation of chlortetracycline reached 99.04%at 35 h.It can be seen that the strain F3 grew rapidly in 10-PMSM medium and reached its maximum growth density at 5 h,after which the bacterial density remained stable,but biodegradation continued.This research indicated that there was certain improvement effect in the single technique of organic fertizer and the combination of other modifiers based on organic fertilizer was more effective,and each technology can show good results in a short period of time and can maintain for a long time.The alien earth soil improving technology has certain improvement effect in short time,and the improvement effect of combining other technologies was not better than that of organic fertilizer alone or combined with other modifiers.This study also obtained a strain with high efficiency of chlortetracycline degradation and enriched the gerpmlasm resources of chlortetracycline degrading bacteria and provided scientific basis for the harmless treatment of chlortetracycline pollutants.