The occurrence of 22 antibiotics in water samples, sediments, fish and shellfish in aquaculture area of the Pearl River Estuary (Zhuhai and Daya Bay) was studied, using ultrasonic extraction combined with ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The main pollutants detected in aquaculture area of the Pearl River Estuary are quinolones such as norfloxacin, ofloxacin, ciprofloxacin and flumequine. Higher Σantibiotics were observed in Zhuhai Bay in water and sediments compared with Daya Bay. The concentrations of antibiotics in water samples, ranging from 0.13 (sulfamethoxazole) to 4.68 (spectinomycin) ng/L on average, were strongly affected by precipitation. The concentrations of antibiotics in sediments, ranging from 0.02 (isochlortetracycline) to 8.77 (spectinomycin) ng/g (dry weight) on average, accumulated over time. The concentrations of antibiotics in seafood ranged from 0.06 (sulfamerazine) to 46.75 (norfloxacin) ng/g (dry weight). The concentration levels of antibiotics in shellfish and fish were similar and did not show any significant difference. The correlation analysis showed that the concentration levels of antibiotics among sediments were the same; for most seafood, it was same; and for water samples, the difference was great.

A fast and simple method for simultaneous determination of fifteen antibiotics (sulfadiazine, ciprofloxacin, penicillin, spechromycin and roxithromycin) in mussels using ultrasound extraction, solid phase extraction purification and ultra performance liquid chromatography-tandem mass spectrometric was established. The mussel samples were extracted by ultrasonic extraction, followed by solid-phase extraction (SPE) as the cleanup procedure. Ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) was used for identification and quantification of antibiotics. The performance of two kinds of SPE cartridges, Oasis HLB and Oasis PRiME HLB, was compared, with the latter showing better results. Recoveries ranged from 64% to 121% at spiking levels of 50 ng/g, with RSD being 0.5%–19%, and from 67% to 117% at spiking levels of 100 ng/g, with RSD being 1%–9%. Limits of detection (LODs) ranged from 0.004 to 0.5 ng/g (dry weight) and limits of quantification (LOQs) ranged from 0.013 to 1.67 ng/g (dry weight). The recoveries were reasonable and the detection limit was low. Finally, the method was successfully applied to the determination of the target antibiotics in mussel samples (Hyriopsis cumingii) collected from Poyang Lake. 9 out of 15 selected antibiotics were detected in the collected mussel tissues. The concentration and detection frequency of trimethoprim in mussels were the highest. The concentration of trimethoprim was 78.8 ng/g, followed by spectinmycin (41.2 ng/g) and ciprofloxacin (39.8 ng/g).

Using one kind of main mercury methylation iron reducing bacteria of Geobacter sulphurreducens PCA strains as targeting bacteria, two kinds of quinolones ciprofloxacin and ofloxacin were chosen to study the influence of antibiotics on PCA strains and its ability to methylate mercury in combined pollution. The experiment results showed that a promoting effect of antibiotics on growth PCA was found under the low concentration. Through the detection of the concentration of antibiotic and the figure of ESI scan, it was found that Geobacter sulphurreducens PCA could metabolize ofloxacin, but ciprofloxacin could not be degraded by Geobacter sulphurreducens PCA. Methylation of mercury was promoted by the presence of two kinds of antibiotics, the methyl-mercury conversion rate of ofloxacin to Geobacter sulphurreducens PCA was 4.21 times higher than that of the control group, ciprofloxacin was 2.27 times, and the addition of two mixed kinds of antibiotics was nearly 2 times respectively. In the mixed solution, there is no superimposed effect of methyl-mercury.