| The widespread use of antibiotics in health care and animal husbandry results antibiotics entering into the environment extensively,while residual antibiotics in the environmental system induce antibiotic resistance genes?ARGs?.Due to its persistence and easy-spread nature,ARGs are defined as an emerging contaminants,and have become the most significant challenge to human health in the 21st century.Water environment system is an important medium for the release and spread of resistant bacteria and ARGs.Meanwhile,ARGs can spread between human and environment alongside through the water cycle.Shanghai as a densely populated and megacity along the Yangtze River Delta,China,has a dense water network.Health and safety of water environment is crucial to the stable development of the city.Therefore,exploring the spatial and temporal distribution of ARGs and the influence factors in the water had important benchmark for the future risk management and control of ARGs pollution in Shanghai.This study focused on the ARGs in the different typical urban water of Shanghai,China.The 17 sampling sites including Huangpu River,Suzhou Creek,Dianpu River,landscape water,wastewater treatment plant,urban sewage pumping station and farm were collected during winter,spring and summer.These samples were classified into three groups according to the water quality,namely clean water?Res,HPU,HMH,HXH,HNJ?,polluted water?SZR,DPU,DPM,DPD,BI,BE,WWTPI,WWTPA,WWTPE,PW?and landscape water?Park,WetL?.To explore the spatio-temporal distribution of ARGs and influencing factors,there were 10 ARG subtypes(tetM,tetQ,sul1,sul2,ermB,mefA,aadA-1,str B,blaCTX-M,blaTEM),integron intI1 were detected using the real-time quantitative PCR,and variations of environmental factors were tested in all samples.Meanwhile,using high-throughput sequencing technology,the microbial community structure in the samples were analysed.?1?The distribution of total concentration of ARGs in space were landscape water<clean water<polluted water,specifically represented by Res<Park<HMH<Wet L<HXH<HPU<DPU<BE<DPD<HNJ<SZR<DPM<WWTPE<BI<WWTPA<WWTPI<PW,among them,Res and PW had the lowest concentration?2.33×106±2.30×105 copies/m L?and highest concentration?1.93×109±1.19×109copies/mL?,respectively.The spatial distribution of ARGs was mainly affected by human activities,where human activities intensively had higher concentration and wastewater treatment plants and pumping stations are important sources of ARGs in urban water.Among the target ARGs,the detection concentration of sulfonamide ARGs was the highest,followed by aminoglycosides ARGs.The highest concentration was sul1,ranging 3.18×1061.93×109 copies/mL.This was mainly due to the higher diversity of potential host bacteria carrying sul1,and the concentration of sul1 in this study was higher than that detected in water environments of other cities.The highest concentration of ARGs was mainly distributed at PW,WWTPI and WWTPA,and the lowest concentration was at Res.The results of high-throughput sequencing showed that there were significant differences in microbial community structure in different sampling sites.Actinbacteria,Proteobacteria,Bacteroidetes and Verrucomicrobia were the dominant species in clean water and landscape water.Polluted water was dominated by Proteobacteria,Bacteroidetes and Firmicutes,however,all contained Proteobacteria,Actinobacteria and Bacteroidete phylum.The comprehensive analysis of the target ARGs and microbial community structure showed that Arobacter,Bacteroides,Prevotella,Trichococcus and Thiothrix had a significant positive correlation with ARGs and Sediminibacterium and Synechococcu had a significant negative correlation with ARGs.?2?The time distribution characteristics of ARGs showed that,in all ARGs,the concentration of sul1 increased from 6.61×106 to 5.20×107 copies/mL along with the sampling time.However,the concentration of other ARGs was not significantly changed.The concentration of sul1,sul2 and tetM in the Huangpu River was generally higher than that in 2011.In recent years,although the water quality of the Huangpu River has continuously improved,however the concentration of ARGs has increased.In terms of seasonal distribution,except for mefA,sul1 and tetM,the concentration of other ARGs showed that in winter-spring was higher than in summer,which was mainly related to the concentration of NH3-N in winter-spring being higher than in summer.Microbial community structure also showed variation over time.The abundance of Proteobacteria and Bacteroidetes in winter-spring was higher than that in summer,and the abundance of Actinobacteria was greater in summer than that in winter-spring.Analysis of the correlation between environmental factors,microbial community structure and ARGs revealed that NH3-N,TN and TP were the major environmental factors affecting microbial community structure and ARGs and NH3-N had the greatest impact.Aquirestis,Candidatus Xiphinematobacter and Mycobacterium were significantly negatively correlated with mefA,sul1 and tetM.The abundance of these microorganisms in winter-spring was higher than that in summer,which may be the main factor affecting the seasonal distribution of ARGs.?3?Both of the constructed wetland and the oxidation ditch of wastewater treatment plants had some effect on the removal of ARGs,and the logarithmic removal rates of ARGs were in the range of 0.19 to 1.37 log and 0.69 to 1.76 log,respectively.The logarithm removal rate of mefA,tetQ,blaCTX-M,aadA-1 and strB in constructed wetlands was greater in winter-spring than that in summer.Moreover,the logarithm removal rate of all of the ARGs in the oxidation ditch process of wastewater treatment plants was also greater in winter-spring than that in summer.This may be due to higher temperatures in summer and larger microbial biomass than that in winter-spring,respectively.Redundancy analysis?RDA?found that the removal of ARGs by the two processes was related to the removal of TP,NO3-N and NO2-N.In summary,this study explored the temporal and spatial distribution of five types of ARGs in Shanghai's typical urban waters and revealed the effects of environmental factors and microbial community structure on ARGs.Pollution sources such as wastewater treatment plants and pump stations could significantly affect the concentration of ARGs in urban rivers,and that nitrogen and phosphorus nutrients can promote microbial reproduction and stimulate the spread of ARGs in the environment.Therefore,we need to focus on the pollution source in cities and take effective measures to control the spread of ARGs in the environment. |
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