Occurrence Characteristics Of Antibiotics And Antibiotic Resistance Genes In Jinze Drinking Water Source Region

Drinking water source region usually exists in the form of a river-reservoir system,and the water quality of it is closely related to human health.However,researches on the characteristics of pollutants in the river-reservoir system are still scare.Therefore,investigations on the characteristics of pollutants in the river-reservoir system are of great importance to have a comprehensive understanding of the occurrence characteristics and the environmental behaviors of the pollutants.In addition,some purification processes have been applied in the reservoir to improve the water quality,but the purification effects of these processes on the pollutants in reservoir still need to be studied in order to provide evidences on the pollution control and integrative management of the reservoir.What's more,the occurrence characteristics are influenced significantly by hydrodynamic conditions.The hydrodynamic modeling of the reservoir can provide evidences for the studies on fate and transportation of the pollutants.Therefore,Jinze drinking water source region was selected as a river-reservoir system,and the water quality as well as the occurrence characteristics of antibiotics and antibiotics resistance genes?ARGs?was investigated.17 antibiotics were detected by liquid chromatography coupled with tandem mass spectrometry.283 ARGs were detected by high throughput quantitative PCR.The hydrodynamic modeling was conducted by Delft 3D.The main conclusions are as follows:?1?The concentrations of DTN and DTP both showed significant seasonal variation,indicating that seasonal-related hydrological situation had impacts on the occurrence of them.Compared with the river system,the reservoir system could reduce the concentration of DTP but accumulate DTN.NO₃^--N was the main form of DIN,indicating the purification capability of the surface water at this region.According to the TLI,the reservoir was mostly in a light eutrophic state.?2?17 antibiotics were all detected with the detection frequencies of more than 70%except for vancomycin.The concentrations of all target antibiotics were n.d.-296.4 ng/L and fluoroquinolones?FQs?was the dominant pollutants in the studied region.The highest concentration level of antibiotics was obtained in winter,and the lowest one was obtained in summer.The concentration of antibiotics in winter was 1.6-2.1 times higher than those in other three seasons.In terms of the spatial variation,the concentration level of antibiotics in the river system was higher than that in the reservoir system,and in the reservoir system,the concentration level had a decline trend from the pretreatment area to the water delivery area,indicating that the purification processes in the reservoir were effective on the attenuation of antibiotics.The ecological risk assessments revealed that norfloxacin,amoxicillin and penicillin G posed relatively high risks to the aquatic ecosystem and should be taken priority control.In addition,the purification processes in the reservoir had a positive effect on reducing the ecological risks of antibiotics.?3?The average number of detected ARGs was 69,and the absolute abundance of ARGs was n.d.-3.20×10¹⁰ copies·L^-1,and the relative abundance of ARGs was n.d.-2.65×10^-1.Multidrug ARGs,aminoglycoside ARGs and sulfonamide ARGs were the dominant ARGs in the studied region.The absolute abundance of ARGs was highest at S1 and highest in spring,while the relative abundance of ARGs was highest at S1 and highest in winter.There was a decline trend of the abundance of ARGs from the pretreatment area to the ecological purification area and then to the water delivery area,indicating that the hydrophytes and the ecological floating bed in the ecological purification area of the reservoir were effective on the attenuation of ARGs.MGEs played an important role in the horizontal transfer,dissemination and accumulation of ARGs.?4?The validation results showed that the 3D hydrodynamic model of Jinze Reservoir was capable of describing the hydrodynamic condition of the reservoir.The result showed that the flow velocity among the observation sites ranked as follows:S2>S3>S5>S6>S4,and the operation mode of the reservoir had impacts on the flow field.The result also revealed that the water temperature showed seasonal variation,and there were no vertical gradients of water temperature.Occurrence characteristics of antibiotics and ARGs were influenced by flow conditions and water temperature.