| Antibiotics,revolutionized medicine in many respects,are widely used in human and veterinary medicines for treating diseases and promoting the growth of livestock animals due to their antibacterial properties.Partially metabolized by organisms,as high as 80-90%of antibiotic compounds can be excreted in their original form into the aquatic environment via urine and feces and antibiotic residues in the environment can not only pose a threat on aquatic organisms,but also promote the development of the antibiotic resistance genes(ARGs).ARGs have attracted attention in the field of scientific research as a new environmental pollutant with "persistence" and"reproducibility".At present,there are more studies on the migration and transformation of the antibiotics and ARGs in the environment and the potential hazards caused.Researchers are increasingly concerned about antibiotics and ARGs in different environmental media.Seventy two sampling sites of sediments were collected in March and July in our study area,respectively.Twenty kinds of antibiotics in sediment phases were analyzed quantitatively by UPLC-MS/MS.Ten kinds of ARGs were analyzed quantitatively by Q-PCR.At the same time,physical and chemical indicators such as particle size,TOC,heavy metals,etc.were also measured.Statistical data were collected for three age groups with a radius of 250m to 1750m for each sampling point.Moreover,they are used for correlation analysis to provide important theoretical support for the treatment of antibiotics and ARGs in Shanghai's aquatic environment.The main conclusions in our studies were as follows:(1)The total concentration of antibiotics in the sediments of urban rivers networks in Shanghai generally showed a pattern that the dry season was higher than the wet season,indicating that the antibiotics contents were affected by temperature and degradation.The abundance of precipitation during the wet season produced a large amount of surface runoff that can dilute antibiotic concentrations.At the same time,the wet season was in July with high temperature and degradability.While the water temperature,flow rate and effect of microbial degradation was low in March.In addition to MLs,the other four types of antibiotics all showed that dry season was higher than the wet,indicating that the use of antibiotics was an important source of residues.(2)Due to the large amount of FQs and TCs used,their strong adsorption ability to sediments and low degree of microbial degradation,these two types of antibiotics occupied the highest content and detection rate among the five types of antibiotics.The sum of the two accounted more than 85%.Due to the strong hydrophilicity of SAs,MLs,and CPs and the weak adsorption capacity of sediments,the contents and detection rate of these three types were relatively low,and the proportion of these three types of antibiotics was less than 15%.(3)Antibiotics in sediment phases were slightly or similar contaminated compared with other areas in China,but severely contaminated compared with some developed countries.It is worth mentioning that compared with antibiotic concentrations in the Huangpu River measured by Chen et al.and the Yangtze River Estuary measured by Shi et al.in 2014,the antibiotics in this study all showed a rising state,indicating that the level of antibiotic pollution in Shanghai is being gradually deepened.In the spatial distribution,TS was the lowest pollution level in the two quarters,indicating the important role of human-derived antibiotics in Shanghai.(4)Among the three major ARGs in the study,there was a relatively large proportion of ARG,which was sul2 in the sulfa-resistant genes,tetAin the tetracycline-resistance genes,and aac(6')-Ib in the quinolone-resistant genes.The following laws were presented on the hierarchical rivers:sul2>sul1>sul3 in each sulfa-resistance genes;qnrS>aac(6')-Ib in quinolone-resistant genes,and SS>TS>FS in wet season;tetA>tetW in each tetracycline-resistance genes.The significant correlation between sul1 and intI1 during the wet season indicated that intI1 could regulate the expression of sul1.The average concentration of 16S-rRNA during the wet season was an order of magnitude higher than the dry season,with significant seasonal differences.16S-rRNA quantitatively normalized the abundance of ARGs.In terms of seasonal distribution,it was the characteristics of first-order stream and second-order stream showing wet season>dry season,while the third-order stream showed the opposite characteristics of dry season>wet season.In terms of hierarchical rivers,the abundance of third-order stream was generally 2-7 orders of magnitude higher than that of first-order stream and second-order stream.(5)The correlation analysis of antibiotics and ARGs showed that there was a significant correlation between the two quarters of TCs and tetW,but there was no significant correlation with another type of tetracycline antibiotic tetA.In the wet season,SAs showed significant correlation with sul2 and sul3.It showed that the extent of antibiotic residues will affect the production and migration of some ARGs.FQs and their corresponding quinolone resistance genes did not show significant correlation in the two quarters because of the quinolone resistance genes mediated by plasmids.(6)By correlating population data and physicochemical factors(particle size,TOC,OD)with antibiotics,it was found that demographic data were significantly correlated with multiple antibiotics.The MLs used for human treatment with large amounts showed correlation with each radius of the population data,and the correlation of the elderly and children was better than that of young adults.There was no correlation between TCs and population because TCs were mostly used for animal husbandry and animal disease treatment.SAs,FQs,and CPs were significantly related to population data in a certain season within a limited radius.It showed that human-derived antibiotics were an important source of antibiotic contamination in urban river networks in Shanghai,and the degree of contamination was related to the amount of antibiotics;There was no correlation between antibiotics and particle size and OD.Only TOC was related to several types of antibiotics,because the water environment of urban river networks was complex and affected by anthropogenic emissions.(7)The population data,heavy metals and physical and chemical factors(particle size,TOC,OD)were correlated with ARGs.tetW as a sensitive indicator of human influence,had a significant correlation with population data during the wet season.And the correlation with young adults was the best,just opposite of the correlation with antibiotics.sul3 also had a significant correlation with the population,and was also best correlation with young adults.Most ARGs did not show significant correlation with population due to the complexity of water environment.Cu and Zn were the two kinds of heavy metals which have the best correlation with ARGs and there was no correlation between Mn and ARGs;The influence of physical and chemical factors on ARGs was not obvious. |
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