Research On The Occurrence Characteristics Of Antibiotics And Antibiotic Resistance Genes In Typical River Water And Sediments Of Hainan Island

The widespread use and even abuse of antibiotics in various fields have caused unused antibiotics to enter the environment through different pathways,leading to the emergence and spread of antibiotic resistance genes(ARGs).This poses a potential threat to the ecological environment and human health and has received great attention in modern society.Surface water in tropical environments is an important water source for many biological communities and human communities,and the surface water environment plays an important role in the spread of antibiotics and ARGs,even becoming an important reservoir for antibiotics and ARGs.Therefore,it is of great significance to study the occurrence of antibiotics and ARGs in tropical surface water.In this study,the three main rivers of Hainan Island in China(Nandu River,Changhua River,and Wanquan River)were selected as the study area.The occurrence characteristics of antibiotics and ARGs in the water and sediment of the three rivers were investigated using high-performance liquid chromatography-tandem mass spectrometry and high-throughput PCR technology,and the driving factors affecting the occurrence of ARGs in water and sediment were analyzed.The main results are as follows:(1)A total of 54 antibiotics belonging to six classes were detected in the water of the three main rivers.The concentration levels of antibiotics in Nandu River ranged from ND-196.54 ng/L,in Changhua River from ND-156.04 ng/L,and in Wanquan River from ND-284.50 ng/L.Among the detected antibiotics in the rivers,macrolides and tetracyclines were the main pollution types.The distribution characteristics of antibiotic pollution in the three rivers showed that the total concentration of antibiotics in Nandu River was the highest,followed by Changhua River,and Wanquan River had the lowest concentration.The pollution of antibiotics in the three main rivers waters was mainly concentrated in the middle and lower reaches.The pollution of antibiotics in the water of the three main rivers poses a certain ecological risk to sensitive aquatic organisms(algae),and the pollution of tetracyclines,virginiamycin M1,dehydrated erythromycin,tylosin,and ofloxacin should be given special attention.(2)Among the 49 target genes detected in water and sediment,a total of 46 ARGs and two integrase genes were detected,with a detection rate of 100%for the integrase genes.The absolute abundance of ARGs ranged from 1.16×10~3-2.97×10~7 copies/L in water and from 3.34×10~3-1.55×10~7 copies/g in sediment.Macrolides,aminoglycosides,and sulfonamides were the main types of ARGs in the study area,with the absolute abundance of genes detected in water showing intl1>mac B>mph A-01>sul2>aad A1>aad A1-01>others,and the absolute abundance of genes detected in sediment showing intl1>mac B>aad A-01>aad A1>mph A-01>ere A>others.tet W,dfr A12,tet E,erm F,tet X,and aac(6’)-Ib were identified as core ARGs in the water and sediment of the three rivers.The relative abundance of ARGs was higher in the middle and lower reaches of the three rivers and lower in the upper reaches and estuaries.(3)The correlation analysis showed that there was no significant correlation between antibiotics and corresponding ARGs in the water of the three main rivers.The ARGs detected in the water of the three main rivers were significantly positively correlated with each other,while in sediment,except for the significant negative correlation between tet Q and tet C,mac B and ere A,and erm F,the other ARGs were significantly positively correlated.In both water and sediment,intl1,intl2 and most ARGs were significantly positively correlated.The integration enzyme genes played an important promoting role in the horizontal transfer of ARGs in the three main rivers,which strongly demonstrated that the efficiency of HGT could be improved in tropical environments,which was more conducive to the spread of ARGs.Among the 9environmental factors,p H was the main factor related to the occurrence of ARGs in water.Among the detected heavy metals,only Cd and Zn were significantly correlated with two ARGs in water.The variance decomposition analysis showed that heavy metals had the greatest potential impact on ARGs among the environmental factors.The abundance of detected ARGs in the three main rivers is low,with less influence from environmental factors and more influenced by mutual interactions between ARGs.