To examine the residual and distributions of tetracycline antibiotics in the Weihe River, SPE-UPLC (solid phase extraction-ultra performance liquid chromatography with UV-Vis detection) was employed to analyze the oxytetracycline (OTC), chlortetracycline (CTC), and minocycline (MC) of 41 surface water and 35 sediment samples collected from main streams, tributaries, and main sewage outlets. The results showed that: (1) The order of residual levels of tetracycline antibiotics in water and sediment from high to low was the following: OTC > CTC > MC., considering the water solubilities are 313 mg/L, 630 mg/L, and 50200mg/L and octanol water partition coefficients (K_ow) are 7.94, 4.16, and 1.12 for OTC, CTC, and MC, respectively. Thus, the distribution of antibiotics was not only related to the basic properties of antibiotics, but also some environmental factors. The concentrations of OTC in water and sediment were in the range of 1.56–87.89 ng/L and 6.13–45.38 ng/g (mean value of 16.13 ng/L and 20.60 ng/g), respectively; while CTC was 1.07–26.78 ng/L and 6.17–32.29 ng/g (mean value of 4.96 ng/L and 14.48 ng/g), respectively; and MC was 0.28–12.35 ng/L and 4.80–29.74 ng/g (mean value of 1.70 ng/L and 12.96 ng/g), respectively. There were maximum concentrations in all sewage outlets. Compared with other areas in China, tetracyclines residual in the Weihe river were at a medium level; (2) in spatial distribution, the levels of tetracyclines in water and sediment from the middle and upper reaches were higher than the lower reaches. Meanwhile, the sewage outfalls and livestock farm waste water discharge appeared to be the main sources of tetracycline antibiotics in the Weihe River; (3) ecological risk assessment revealed that in main streams and tributaries, OTC and CTC may be at a low ecological risk level; while in sewage outfalls, they may represent a medium ecological risk level.

The performance of oxytetracycline adsorption by untreated reed roots, stems and leaves, as well as the desugared reed roots, stems and leaves, was investigated with scanning electron microscopy, Fourier-transform infrared spectroscopy, elemental analysis and surface area analysis to understand the adsorption mechanism. The results showed that the adsorption capacities of untreated reed were 416.35 mg/kg for roots, 341.92 mg/kg for stems and 280.21 mg/kg for leaves, and can be increased significantly by a factor of 8–12 after desugarization. The pseudo-first-order kinetic model was more suitable for describing the adsorption kinetics of reed residues, and the isothermal adsorption process was fitted well by both the Langmuir and Freundlich models. The thermodynamic process suggested that the adsorption was a spontaneous endothermic reaction, and mainly physical adsorption-dominated. The desugared reed tissues had a larger surface area and smaller pore area, and the aromaticity of reed residues increased; on the other hand, the polarity and hydrophilicity decreased after desugarization, thus revealing the mechanism of enhanced OTC(oxytetracycline) adsorption by desugared reed residues. This study suggests that the reed residues contribute the complex adsorption ability for both inorganic and organic contaminates. Corruption of the reed can enhance the adsorption; thus, protecting the natural reed residue and letting it naturally corrupt, rather than artificially cleaning it up, can effectively promote the adsorption of pollutants in the environment and protect environmental and public health.