Distribution Of Antibiotics In Surface And Core Sediments From Aquaculture Areas

In recent years, antibiotics have widely been used in medical treatments, livestock operations and aquaculture, and frequently detected in water, soils and sediments as emerging pollutants. Antibiotics can induce antimicrobial resistance in microorganisms, which may pose potential threats to ecological systems and human health. The production of mariculture increases rapidly in coastal intertidal zones and offshore areas in China. Antibiotics were widely used in aquaculture in these areas. The information of residual levels and spatial distribution of antibiotics in sediments is useful in the assessment of ecological risk and contamination control for antibiotics.In this study,22 samples of surface sediments and 5 sediment cores were collected from costal aquaculture areas in Dongying and Yancheng City. An analytical procedure was developed for simultaneous extraction and determination of 26 antibiotics in sediments using accelerated solvent extraction (ASE) followed by solid phase extraction (SPE) clean-up and high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis. The distribution of residual antibiotics in surface and core sediments was studied. A preliminary ecological risk assessment was conducted on aquatic organisms employing risk quotients (RQs) method.The results showed that all the tested antibiotics were detected in the surface and core sediments from coastal aquaculture areas in Dongying and Yancheng City. Quinolones are the antibiotics with the highest level in sediments with a range of 6.89?63.3 ng/g, followed by macrolide antibiotics (0.67?26.1 ng/g). The levels and categories of antibiotics in surface sediments at Kenli County were similar to those of sediments at Sheyang County. Enoxacin, enrofloxacin, norflloxacin and erythromycin were detected with the highest concentrations and frequency, with a maximum concentration of 18.6,23.6,17.0 and17.5 ng/g, respectively.The distribution of antibiotics in surface sediments demonstrated an obvious spatial distribution, as the farther in the distance from the aquaculture areas, the lower the concentration of antibiotics were determined. The levels and composition of antibiotics in various aquaculture ponds were different. For example, the concentrations of antibiotics in surface sediments collected from sea cucumber culture ponds (55.3-71.3 ng/g) were higher than those of shrimp ponds (52.2?55.1 ng/g), which related to the differences in antibiotics usage and culture operations.The vertical distribution of antibiotics in sediment cores was different for various classes. The levels of sulfonamides and macrolides demonstrated a relatively smaller change with the depth of samples, while the vertical changes were much larger for quinolones. The patterns of vertical distribution of antibiotics were deemed to relate to their usage and environmental transfer and transformation.