Attenuation And Its Mechanism Of Selected Antibiotics In River Systems

Based on 14 typical antibiotics commonly detected in urban rivers of China,analysis method of 14 antibiotics was established by solid phase extraction-high separation liquid chromatography-tandem mass spectrometry(SPE-RRLC-MS/MS)for two complex matrices of environmental water and sediment,and the method was applied to the quantitative analysis of antibiotics in water and sediment in indoor flume simulation experiment for migration and transformation of antibiotics and field tracer experiment.The circulating flume system was used to simulate the migration and transformation process of antibiotics in water-sediment systems such as rivers,and combined with control experiments to identify the dominant process and the mechanism of attenuation of antibiotics in water-sediment system.Then,the attenuation experiment of antibiotics in actual river was carried out,travel time of specific water parcel was determined by tracer technology,Lagrangian sampling scheme was used to collect water samples,and the comprehensive attenuation rule of antibiotics in river was analyzed.The results of the study were summarized as follows:(1)The elution solution,elution volume,extraction solvent,extraction times,and mass spectrometry conditions were optimized by using SPE-RRLC-MS/MS technology.The recoveries of 14 antibiotics in river water were 56%-117%,the relative standard deviations(n=3)were 0.10%-12%;the recoveries of 14 antibiotics in sediment were 57%-127%,the relative standard deviations(n=3)were 0.10%-25%.The detection limits of antibiotics in river water and sediment were 0.18-5.88 ng·L-1 and 0.25-2.94 ng·g-1,respectively.The method was applied to detect antibiotics in surface water and sediment of Nanfei River in Hefei City.Five antibiotics were detected,and the concentrations of antibiotics in river water and sediment ranged from 32-308 ng·L-1 and 2.70-329 ng·g-1,respectively.(2)Circulating flume experiment and control experiment was used to study the migration and transformation rule and mechanism of antibiotics in water-sediment system,the results showed that the most important attenuation process of these 14 antibiotics in water environment was photolysis.The half-lives of 14 antibiotics were 2-26 days.The order of half-lives was: sulfadiazine > sulfamethoxine > sulfamethazine > sulfamethoxazole > sulfamethazine > sulfathiazole > ofloxacin > Nozafloxacin> Norfloxacin> Ciprofloxacin> Erythromycin> Tetracycline> Roxithromycin> Oxytetracycline.All antibiotics were detected in surface sediment.Some antibiotics migrated to deeper sediment and pore water due to hyporheic exchange.Quinolone antibiotics were detected in both surface and deep sediments.The concentration and frequency of sulfonamide antibiotics detected in pore water were higher than those of the other three types of antibiotics.The high mobility and persistence of sulfonamides may pose a threat to groundwater.(3)The tracer experiment combined with Lagrangian sampling scheme was used to study the attenuation law of antibiotics in actual river,the results showed that the half-lives of 14 antibiotics obtained in natural river were 2.9 h to 20.8 h,which was much lower than 2 d-26 d of the circulating flume experiment.The result was attributed to the elimination of dilution effect in the flume experiment,only considered the attenuation of the antibiotic itself.The results indicated that dilution and mixing played a significant role in the attenuation of antibiotics.