Sorption and desorption of antibiotic tetracycline on marine sediments

Tetracycline is commonly used for human therapy and veterinary purposes as well as agricultural feed additives. In this study, batch experiments were carried out to investigate the sorption behaviour of tetracycline on marine sediments. The sediment samples were collected from Victoria Harbour, Hong Kong. Sorption isotherms of tetracycline on marine sediments can be well described by a Freudlich model. The calculated Kf varied from 1.12 to 2.34 L g−1. After H2O2 oxidation for removing the organic carbon from marine sediments, the Kf values were reduced by more than 80%, but the organic carbon normalized sorption constant averaged 213.1 L g−1 for the H2O2-treated sediments, which was higher than 98.3 L g−1 for the raw marine sediments. The calculated hysteresis coefficient H ranged from 0.79 to 0.90 indicating that there is a hysteresis in desorption. The sorption of tetracycline on marine sediments was found to decrease with an increase of pH and salinity. These research findings are of importance to an assessment of the fate and transport of tetracycline and other similar antibiotics in seawater–sediment systems.