Dynamics and mechanism of degradation of three tetracycline antibiotics from pig manures in soil

Simulated indoor incubation experiment was carried out to explore the degradation dynamics of three tetracycline antibiotics (TCs, including CTC, TTC and OTC) from pig manures in soil and the mechanisms were investigated as well. The results show that the TCs entering soil with pig manure can soon enter the degrading period, the three TCs concentrations of all the treatments are rapidly declined at the beginning, and after that the declining speeds are slowed down. The degradation rates and degradation percentages are significantly different for different antibiotics with different concentrations (P0.05). At the day of 180 the degradation percentages are in the order: CTCOTC TTC. The halflives of CTC, OTC and TTC are 17.43d, 31.32d and 49.48d. The degradation percentage is negatively correlated with the amount of manures used and positively correlated with incubation time. These results indicate that the TCs from pig manures in soil are more degradable than those of chemical ones. The microbiological from manures decomposition played an important role, the microorganic degradation is best for OTC. With the extension of incubation time, the concentrations of tetracycline antibiotics are declined through microbiological degradation and the others, but there may have the risk of environmental at a short time after the manures entering the soil.