Temporal And Spatial Distribution Of Antibiotics And Their Correlation With Microbial Communities In Lianjiang River Basin

Since the 1990 s,with the innovation in analytical technologies,and upgradation of sewage treatment processes,environmental research has gone beyond the removal of the traditional priority is to control pollutants.More research has concerned trace emerging pollutants such as antibiotics.Lianjiang River originates from Puning,Jieyang City,Guangdong Province,flows through Chaoyang and Chaonan Districts of Shantou City,and joins the South China Sea.Lianjiang basin is densely populated,and the major industries in the basin include textile and dyeing,and electronic waste disassembly.In recent years,the central and provincial governments have put a lot of efforts to reclamation of Lianjiang Basin,and the water quality in Lianjiang River has been continuously improving.Studies on the Lianjiang River Basin have focused on heavy metals,nitrogen and phosphorus,polycyclic aromatic hydrocarbons,etc.However,there is a lack of research on the pollution of antibiotics in Lianjiang River Basin.In this study,18 typical antibiotics of 4 categories(Sulfonamides,Macrolides,Fluoroquinolones and Chloramphenicols)in the whole section of the main stream of Lianjiang River were systematically studied.Water and sediments samples were collected from 20 points in the main stream and 5 fish and shrimp ponds downstream.The temporal and spatial characteristics,sources and risk levels of antibiotics in the water environment of Lianjiang River Basin were evaluated.The relationship between microbial community structure and antibiotic concentration in sediments was explored.The main results are as follows:1.The total concentration of antibiotics in the water phase during the wet season ranged from 0.96-4502.89 ng/L,with an average concentration of 34.27 ng/L.The total concentration of antibiotics in water phase during the normal water period ranged from 1.23 to 4415.56 ng/L,and the average concentration was 986.59 ng/L.The total concentration of antibiotics in sediments during dry season ranged from 580.75-9785.61 ng/kg,with an average concentration of 3202.92 ng/kg.The total concentration of antibiotics in the sediments in the wet period ranged from 399.77-8474.29 ng/kg,with an average concentration of 2644.54 ng/kg.The total concentration of antibiotics in the sediments in the normal water period ranged from 716.50 – 12918.31 ng/kg,with an average concentration of 5027.50 ng/kg.The water phase was dominated by chloramphenicol antibiotics,and the total level of antibiotics in wet season in the decreasing order was upstream > downstream > aquaculture pond > middlestream,while it was middle stream > upstream > downstream > aquaculture pond in the normal water period.Chloramphenicol was the dominant antibiotic in the sediments.The total concentration of antibiotics in the dry season was downstream > upstream >middlestream,whereas it was middle stream > downstream > upstream > aquaculture pond in the normal water period.2.Antibiotic pollution in Lianjiang River Basin mainly came from antibiotics used in aquaculture industry,and antibiotics remained in the treated medical wastewater and domestic sewage.Primary environmental risks of antibiotics in the water of Lianjiang River Basin were from Sulfamethoxazole,Norfloxacin and Chloramphenicol.Environmental factors have a strong correlation with antibiotics.Antibiotics such as Sulfathiazole,Florfenicol,Ciprofloxacin,Sulfapyridine,Chloramphenicol and Norfloxacin are positively correlated with a variety of conventional environmental pollutants.The low treatment rate of wastewater contaminated with antibiotics may be the main reason for this correlation.3.Proteobacteria,Chloroflexi,Actinobacteria,Bacteroidetes and Acidobacteria were the dominant phyla in the surface sediments of the main stream of Lianjiang River.KEGG prediction showed that among all antimicrobial resistance genes,?-lactam resistance was the highest,followed by vancomycin resistance and peptide resistance.The use of antibiotics will not only select their corresponding resistance genes,but also may play a certain role in the regulation or influence of other antibiotic resistance genes.On the other hand,bacteria containing antimicrobial properties may affect the metabolic degradation of antibiotics.4.Sulfonamides showed the greatest co-occurrence with microbial community structure variations,and quinolone antibiotics had a certain degree of interaction with microbial community structure composition.Asgardaeota,Firmicutes,DeinococcusThermus and so on have the greatest co-occurrence with antibiotics.The relationship between antibiotics and microorganisms in the environment is mainly positively correlated.The existence of antibiotics in the environment not only inhibits or kills bacteria,but also plays a regulatory role in the microbial community.