Occurrence, Distribution and Ecological Risks of Fluoroquinolone Antibiotics in the Dongjiang River and the Beijiang River, Pearl River Delta, South China.

The occurrence and distribution of five selected fluoroquinolones (FQs) were studied in the Dongjiang River and the Beijiang River, South China. Ciprofloxacin, norfloxacin and enoxacin, used as human and veterinary medicines, were detected with detection frequencies of 75%-100% and average concentrations of 9.5-18.8 ng L(-1) in the two rivers. Meanwhile, enrofloxacin, which is only used as veterinary medicine, was detected at lower levels (2.9-4.0 ng L(-1)) than those of ciprofloxacin, norfloxacin and enoxacin. The spatial distribution of the five FQs exhibited a close relationship with the intensity of local human activity. Certain antibiotics were detected in industrial wastewater and domestic sewage at considerably higher concentrations than those measured in the river water, indicating important sources of antibiotic contamination. Finally, an ecological risk assessment based on the calculated risk quotient showed that ciprofloxacin could pose high risk to Microcystis aeruginosa (M. aeruginosa). The two rivers are important sources of drinking water and should arouse the attention of relevant departments. Effective measures must be taken to strengthen the protection of the two rivers.