The occurrence and seasonal changes of antibiotics in the Victoria Harbour and the Pearl River were studied using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry with multiple reaction monitoring(MRM).The results showed that the concentrations of antibiotics were mainly below the limit of quantification(LOQ) in the ambient marine water of Victoria Harbour.However,except for amoxicillin,all the target antibiotics were detected in the Pearl River during high(summer) and...