| Antibiotic residues in the environment have become a subject of public concern. Large quantities of antibiotics are administered to humans and animals to treat diseases and infections. Some antibiotics are also used at sub-therapeutic levels to promote growth of livestocks. A high percentage of the administerd antibiotics is often excreted by the dosed humans and animals without in the forms of conjugates or unchanged which will possibly enter the aquatic environment. Recent studies have clearly demonstrated that antibiotics are prevalent at detectable concentrations in waters, including municipal wastewater, riverine water, lake-water, and even ground water. These findings merit concerns because antbiotic contaminants may perturb microbial ecology, increasing the proliferation of antibiotic-resistant pathogens and thus posing threats to hunman health. A great amount of antibiotic pharmaceuticals are administered in China due to the huge population as well prosperity of livestock farming and aquaculture. However, so far, there has been few reports on the residues of antibiotics in aquatic environment in China, partly because of the lack of feasible analytical methods. In this work, we chose eight frequently-used antibiotics including ofloxacin (OFX), norfloxacin (NFX), ciprofloxacin (CFX), sulfadiazine (SDZ), sulfamethoxazole (SMX), sulfamethazine (SMZ), chloramphenicol (CAP) and trimethoprim (TMP) as the targets to develop a sensitive multi-residue analytical method of antibiotic contaminants in aquatic environment. The distribution of the selected antibiotic residues in urban riverine water and their fate during the municipal wastewater treatment processes have also beenprimarily studied. The work is summarized as the following:1. A simple and feasible method had been developed for simultaneous determination of fluoroquinolones, sulfonamides, chloramphenicol and trimethoprim residues in aquatic environment by combination of solid phase extraction (SPE) and high performance liquid chromatography (HPLC).①SPE conditions (e.g. the adsorbents, pH value, flow rate, selection of washing solvent and eluting solvent) were optimized to improve extraction efficiency;②HPLC condition was optimized to achieve the baseline separation of the selected antibiotics. ?Internal standard quantification was adopted to decrease the matrix effects which has been a significant problem during LC analysis. The recoveries for the investigated antibiotics ranged from 80 to 120% for spiked tap water, 63 to 126% for urban surface water and 65 to 112% for municipal wastewater respectively. The relative standard deviations were always lower than 18% . The method quantification limits were 0.030~0.080μg/L for surface water and 0.12~ 0.25μg/L for wastewater respectively.2. The distributions of the selected antibiotics in three urban streams and the Pearl River at Guangzhou were preliminarily studied. SDZ, SMZ, SMX, TMP, OFX+NFX and CPX have been detected in the Pearl River at Guangzhou, at concentrations ranged from 0.065 to 1.910μg/L. TMP and SMX were the most frequently detected antibiotics, which have been detected in 66.6% and 80.0 % respectively of water samples. The concentrations of TMP and SMX increased by 0.02 and 0.15μg/L respectively in the Pearl River right at the downstream of its confluence with the Shijing River. SMX was also detected at 0.244～0.510μg/L in the lower reach of the Liuxi River.3. The occurrence and fate of the selected antibiotics were preliminarily studied during the municipal wastewater treatment processes in Guangzhou. SMX, SDZ, OFX, CAP, and TMP have been detected in the raw wastewaters, with concentrations ranging from 1.02 to 7.91μg/L. These concentrations of antibiotic contaminants showed no obvious variations after preliminary treatments (sand filter and/or primary sedimentation). About 80～90% of the antibiotics have been removed after the activated sludge treatment. None of the investigated antibiotics were found to be above MQLs in the final effluents after chlorinated disinfection.
|
PDF Full Text Request