| At present,excrement of livestock and poultry is considered as an important reservoir for antibiotic resistance genes(ARGs),heavy metals and antibiotics.Anaerobic digestion is an effective method to deal with a large number of livestock and poultry manure.The biogas slurry produced is mostly used to fertilize the field,which can obviously improve the yield and quality of some crops.However,as the generated biogas slurry still contains a large number of heavy metals,antibiotics and antibiotic resistance gene residues,it is bound to cause certain harm to the farmland soil environment.The existing studies mainly focused on the content characteristics of antibiotics in farm areas and farmland soil,but paid little attention to the pollution and distribution characteristics of ARGs in farmland soil,and the risk assessment of antibiotics and ARGs is still in the initial stage.Therefore,in this study,the content and distribution of heavy metals,antibiotics and ARGs in the farmland soil environment were studied,and the ecological risks of heavy metals,antibiotics and antibiotic resistance genes in the farmland environment were scientifically evaluated,mainly aiming at the soil samples in the dry field and paddy field under the returning mode of biogas slurry.The main conclusions are as follows:(1)Five heavy metals(Cu,Zn,As,Cd and Pb)in upland soil,paddy soil and ditch sediment were generally detected in all samples,among which the content of Zn was the highest.The content of heavy metals in soil showed a decreasing trend from ditch soil-paddy soil-upland soil-control.The content of Cu and Zn in the roots,stems and leaves of water celery is generally high.(2)According to the detection of 9 typical antibiotics in the soil samples,oxytetracycline and aureomycin were detected in the soil and sediment of paddy fields,while the other 7 antibiotics were not detected in the samples,which may be because the irrigation of biogas slurry was not carried out during the epidemic.According to the test results,the concentration of oxytetracycline was significantly higher than that of aureomycin,and in different soil samples,the concentration of antibiotics was higher in paddy soil.(3)the test results showed that the 17 target ARGs were detected in all the samples.According to the data analysis,the relative abundance of tet W,tet Q,sul1,sul2 and erm F ARGs was relatively high,and the relative abundance of ARGs in all the soil samples was as follows: sulfonamide > tetracycline > macrolactone > quinolones.(4)Pearson correlation coefficient analysis of ARGs and MGEs abundance by SPSS software showed that int I1 was significantly correlated with tet Q,sul1,sul2,qnr S,erm B,erm F(P<0.01).This suggests that MGEs may be involved in the horizontal transfer of ARGs between microorganisms,leading to the development of resistance to multiple antibiotics.(5)Heavy metal pollution in soil samples was analyzed by the potential ecological risk index method,and the element Zn evaluation index was significantly higher than that of the other four elements,showing severe pollution.The index values of Cd and Pb were all less than 3,showing no pollution,while the elements Cu and As were slightly polluted.The analysis results of ecological risk values showed that element As presented low risk,other elements presented no risk,and the overall RI values were all risk-free.In addition,the ecological risk assessment for antibiotics showed that OTC was medium-low risk in paddy soil and ditch sediment,while CTC was risk-free for the time being in soil samples.Because at present still has not formed the system of antibiotic resistance genes risk assessment benchmark,so this study combined with pathogenic bacteria and the mobile genetic elements as the damage and spread risk factors,to preliminary assessment of antibiotic resistance,it is concluded that farmland soil environment int I1 can accelerate the spread of antibiotic resistance genes,have a high risk of drug resistance. |
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