Study On The Removal And Dissemination Characteristics Of Drug Resistance Genes In Bioretention Ponds

In recent years,with the unreasonable use and long-term abuse of antibiotics,the pollution of antibiotic resistance genes(ARGs)caused by antibiotic residues in the environment has become increasingly prominent.As an important carrier of non-point source pollution,rain water runoff has been proved to be one of the potential paths for the spread of ARGs in the environment.On the other hand,as a typical control facility of rain water runoff pollution,bioretention cells has a good removal effect on conventional pollutants such as nitrogen,phosphorus and heavy metals,but there is a lack of research on the removal of antibiotic resistance bacteria(ARB)and antibiotic resistance gene in rain water runoff.Therefore,in this study,the environmental behavior of antibiotic resistance bacteria and drug-resistant genes in bioretention cells was studied by using RP4 plasmid containing tetracycline(tet A,tet R),ampicillin(bla _TEM)and kanamycin(aph A)as target genes.Through the study on the removal characteristics of ARGs in the bioretention cells,the results show that the removal efficiency of ARB and ARGs in the bioretention cells is good,and the removal rate of ARB is 2.76-3.28 log;ARGs,and the removal rate is 3.59-5.13 log.The bioretention cells has different effects on ARB and ARGs removal under different operating parameters,under the selected parameters,The bioretention cells with matrix packing ratio 7:3,Hydraulic retention time for 9 h and none submerged area has the best effect on ARB removal has the best effect on ARB removal;and the bioretention cells with matrix packing ratio 8:2,HRT for 6 h,submerged area of 150 mm was the most suitable for ARGs pollution control in runoff.The removal efficiency of ARB and ARGs in bioretention cells was affected by the initial ARB concentration of influent.The removal efficiency of ARB and ARGs in bioretention cells was less affected by the initial ARB concentration of influent.The distribution characteristics of ARB content along each bioretention cells are as follows:100mm>300 mm>500 mm in the matrix packing layer.the accumulation of ARB in the bioretention cells will increase the risk of ARB outflow from the effluent;the total relative abundance of bla _TEMin the matrix layer of the bioretention cells is similar to that of tet R,which is about an order of magnitude higher than the total relative abundance of aph A.The ARGs in the bioretention cells mainly existed in intracellular form,and the proportion of extracellular drug resistance genes in the matrix layer had no obvious effect on the removal of ARGs.Both matrix fillers and biofilms had good adsorption effects on ARB and ARGs.Through the study on the propagation characteristics of ARGs in the bioretention cells,the results show that the larger the proportion of soil in the matrix filler ratio,the stronger the transmission capacity of ARGs;the effect of HRT on the binding transformation of ARGs is different,high HRT hinders the binding transfer of ARGs in the device,but promotes the transformation process;the setting of flooded zone can promote the spread of ARGs.The four strains of Terrabacter,Clostridium sensu stricto,Effusibacillus and Massilia explained the changes of ARGs in the bioretention cells(total 98.9%).The extracellular polymer metabolized by microorganisms had little adsorption capacity to ARGs,and the effect of the operating parameters of the bioretention cells on the total abundance of ARGs potential host bacteria was consistent with that on the spread of ARGs.