Occurrence of quinotone antibiotics and their impacts on aquatic environment in typical river-estuary system of Jiaozhou Bay, China.

There is a data gap on occurrence and transport of antibiotics in river-estuary system, with limited understanding of their impact on aquatic environment. To gain insight into the antibiotic pollution in river-estuary system, 22 surface sediments and 5 wetland plants from Yang River and its estuary in Jiaozhou Bay were selected to explore the occurrence and transport of eight quinotone antibiotics (QNs), and their impacts on aquatic environment. Our results indicated that QNs were widely present in the sediments from Yang River and its estuary, with a range of 1.34-8.69 ng/g (average 4.46 ng/g) in Yang River and 0.99-10.86 ng/g (average 3.92 ng/g) in its estuary, respectively. No obvious correlations were observed between QNs values and TOC contents in sediments from our study area, due to low detective concentrations and frequencies of QNs. The mass loading of individual antibiotic from Yang River to its estuary was from 11.73 to 391.59 g/year, far below those from the other estuarine regions all over the world. QNs were observed in all five wetland plants, demonstrating that QNs contaminants could be taken up by wetland plants and providing the evidence that phytoremediation could be a feasible way to remove contaminants. Negative partial coefficients between individual antibiotic and brassicasterol biomarker suggested the presence of QNs inhibited the phytoplankton growth. Evaluation of ecological risk based on the values of risk quotients (RQs) showed that OFL in Yang River displayed medium risk for algae, and CIP and OFL in its estuary also displayed medium risk value for plant and algae. The results could provide powerful basis on controlling river antibiotics pollution to enhance rivers-estuary security in similar regions.