Distributions And Correlation Analysis Of Antibiotics And Antibiotic Resistance Genes During Infiltration Process

To develop a better understanding of the pollution conditions of antibiotics during the groundwater recharge process. A rapid and sensitive method has been developed for the simultaneous determination of ultratrace antimicrobials in groundwater using solid phase extraction(SPE) and ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS). The 20 most frequently used antimicrobials belonging to the fluoroquinolone(FQN), sulfonamide(SA), tetracycline(TC), macrolide(MC) and trimethoprim(TMP) classes were targeted. Sample pH in SPE, MS operating parameters and the gradient elution protocol were optimized. The method analyte recoveries were 62.7 to 107.5% and detection limits(MDLs) for all analytes ranged from 0.1 to 1.1 ng/L.A nation-wide survey was conducted across China for the first time. Overall, 15 recharge sites employing reclaimed water located in different humid, semi-humid and semi-arid regions were selected for analysis of the presence of the 20 most commonly used antibiotics, including tetracyclines(TCs), fluoroquinolones(FQNs), sulfonamides(SAs) and macrolides. All types of antibiotics were detected at concentrations of 212–4035 ng/L in reclaimed water and 19–1270 ng/L in groundwater. FQNs were the predominant antibiotics in reclaimed water samples(38%), followed by SAs(34%). In the SAs group, sulfamethoxazole4(SMZ) and sulfamonomethoxine together with trimethoprim accounted for 78% of the total, while ofloxacin(OFL) and norfloxacin accounted for 90% of the FQNs, and doxycycline and oxytetracycline accounted for 82% of the TCs. The concentrations in groundwater were generally 1–2 orders of magnitude lower than in reclaimed water. The three most common antibiotics were OFL, erythromycin(ERY) and SMZ. Similar occurrences of different group antibiotics might be evidence of the influence of groundwater recharge by reclaimed water. FQNs were predominant in northern China, while SAs were predominant in the south. Ecotoxicological risk assessment showed that SMZ, ERY and OFL had the top three hazard quotient values, indicating they should receive preferential treatment before recharging. The abundance of sul1 and sul2 was highest among all the antibiotic resistant genes. Overall, these results provide basis for developing standards for groundwater recharge in China.Long term monitoring showed, the antibiotics in reclaimed water and groundwater had notable correlation with the ARGs. In addition, the relative abundance of the ARGs has significant correlation with class 1 integron. It illustrates the transmission of target genes in the experiment strongly relies to the transfer of integron. During the change of reclaimed water, the antibiotics and the ARGs decay continuously. In shallow groundwater, antibiotics and the ARGs decay to a certain degree along the flow direction. The closer to the riverside, the higher level of the antibiotics and the ARGs were found. The levels of the antibiotics and the ARGs showed a seasonal variations, with higher concentration of antibiotics in winter and higher ARGs anbudance during the wet season.