Uptake of the veterinary antibiotics chlortetracycline, enrofloxacin, and sulphathiazole from soil by radish.

Veterinary antibiotics are available for uptake by the plants through sources such as manure, irrigation, and atmospheric interaction. The present study was conducted to estimate the half-lives of three veterinary antibiotics, chlortetracycline (CTC), enrofloxacin (ENR), and sulphathiazole (STZ), in soil and experimentally explore their uptake from contaminated soil to radish roots and leaves. Samples were extracted using a modified citrate-buffered version of the quick, easy, cheap, effective, rugged, and safe "QuEChERS" method followed by liquid chromatography coupled with tandem mass spectrometric analysis (LC-MS/MS) in the positive ion mode. Good linearity was observed for the three tested antibiotics in soil and plants (roots and leaves) with high coefficients of determination (R2≥0.9922). The average recovery rates at two spiking levels with three replicates per level ranged between 77.1 and 114.8%, with a relative standard deviation (RSD)≤19.9% for all tested drugs. In a batch incubation experiment (in vitro study), the half-lives of CTC, ENR, and STZ ranged from 2.0-6.1, 2.2-4.5, and 1.1-2.2days, respectively. Under greenhouse conditions, the half-lives of the three target antibiotics in soil with and without radishes were 2.5-6.9 and 2.7-7.4; 4.7-16.7 and 10.3-14.6; and 4.4-4.9 and 2.5-2.8days, respectively. Trace amounts of the target antibiotics (CTC, ENR, and STZ) were taken up from soil via roots and entered the leaves of radishes. The concentration of CTC was lower than 2.73%, ENR was 0.08-3.90%, and <1.64% STZ was uptaken. In conclusion, the concentrations of the tested antibiotics decreased with time and consequently lower residues were observed in the radishes. The rapid degradation of the tested antibiotics in the present study might have only little impact on soil microorganisms, fauna, and plants.