| The East Dongting Lake is a National Nature Reserve,the pollution of antibiotics and antibiotic resistance genes(ARGs)in the lake has been paied more and more attention in recent years.The previous researches mainly focused on the pollution level,and less on the sources of pollution.The surface water and sediment samples in East Dongting Lake,typical land pollution source(livestock and poultry breeding area,aquaculture area and sewage treatment plant)and atmospheric pullution source samples in East Dongting Lake and lakeside areas were collected by season in this study.The occurrence characteristics of antibiotics and ARGs in surface water and sediments of East Dongting Lake were studied.The correlation between ARGs and other environmental factors was discussed.The occurrence characteristics of ARGs and contribution to the pollution of ARGs in lake in typical land pollution source and atmospheric pullution source areas were analyzed.The main results are as follows:(1)The concentration of antibiotics in surface water of East Dongiting Lake ranged from ND to 943.49 ng/L,and the average concentration was 20.92 ng/L,8.76 ng/L and 11.96 ng/L in spring,summer and autumn,respectively.The concentration of antibiotics in sediments ranged from ND to 177.43 ng/g,with the average concentration of 5.71 ng/g,7.05 ng/g and 16.38 ng/g in spring,summer and autumn,respectively.Ofloxacin(OFL)and sulfamethoxazole(SMX)were the main antibiotics pollutants in East Dongting Lake Basin.Antibiotics pollution was more serious in points that close to human activities and aquaculture areas.SMX and OFL showed high environmental risk in surface water of East Dongting Lake Basin.(2)The absolute abundance of ARGs in surface water and sediments of East Dongting Lake ranged from 0 to 4.88×104 copies/mL and 0 to 2.74×109 copies/g,respectively.sul1 and sul2 were the dominant ARGs in East Dongting Lake Basin.For spatial change,the total abundance of ARGs in upstream was higher than that in downstream.For seasonal change,the surface water was characterized by summer>spring>autumn.The sediment was characterized by spring>autumn>summer.(3)Most antibiotics were positively correlated with corresponding ARGs in spring and autumn surface water,sediments.Dissolved oxygen(DO),temperature(TEMP)and electrical conductivity(EC)were the main factors affecting the abundance of ARGs in surface water of East Dongting Lake.There was a positive correlation between all ARGs and total organic carbon(TOC)in sediments.The positive correlation between Integron and sull,sul2 indicated that int1 was likely to carry sulfonamide resistance genes to migrate in environmental media.(4)In land pollution source areas,the livestock and poultry breeding area and aquaculture area were generally polluted by sulfonamide and tetracycline resistance genes,and the absolute abundance of ARGs ranged from 1.58×102 to 2.75×105 copies/mL and 0 to 1.48×105 copies/mL,respectively.Sewage treatment plants were the main sources of ARGs in water environment.The absolute abundance of ARGs in effluent water ranged from 0 to 1.26×105 copies/mL.The fluxes into lake ranged from 2.89×1014 to 8.43×1017 copies/a,suc1,sul2 and int1 were the main pollutants from sewage treatment plants to East Dongting Lake.(5)The absolute abundance of ARGs in total atmospheric deposition ranged from 0 to 3.9×106 copies/mL.The absolute abundance of ARGs in livestock and poultry breeding area,aquaculture area and population intensive area ranged from 0 to 1.16×104 copies/mL,0 to 2.9×104 copies/mL and 0 to 5.70×104 copies/mL,respectively.The fluxes of atmospheric deposition ranged from 0 to 1.18×1010 copies/(m2·month),qnrS,int1 and sull were the main pollutants transported by atmospheric source to lake in spring,int1,sul2 and tetM were the main pollutants transported by atmospheric source to lake in autumn.The antibiotics used in aquaculture and human activities may affect the deposition flux of ARGs in the atmosphere,and then affect the concentration level of ARGs in lake. |
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