[Effect of Manure from Different Sources on the Leaching of Antibiotics in Soil]

Antibiotic residues in farmland soils resulting from the application of livestock manure poses risks to the soil and water ecology associated with the spread of antibiotic resistance, thereby threatening environmental safety and human health. Here, a leaching experiment was carried out using soil(CK-T), pig manure(PM-T), cow manure(CM-T), and chicken manure(CHM-T) with the addition of tetracyclines(tetracycline, oxytetracycline, and chlortetracycline) and a control group(without antibiotics). The effects of different sources of manure on soil physical and chemical indicators and bacterial abundance under simulated leaching conditions were studied, while the migration of tetracyclines in the different treatments were also determined. The results showed that compared with the CHM-T and CM-T treatments, the tetracyclines in the PM-T treatment were more easily accumulated in the soil(residual amounts=0.90-6.91 mg·kg^-1 compared to the other treatments=0.33-4.42 mg·kg^-1). Compared with the surface soil(0-4 cm), higher concentrations of tetracyclines were detected at soil depths of 16-24 cm. Consistent with the residues of antibiotics, the concentrations of TN and NH₄⁺-N in the soil with the PM-T treatment were increased by 0.044 g·kg^-1 and 14.11 mg·kg^-1, respectively, which were significantly higher than other treatments. The abundance of bacteria in the soil was reduced due to the bactericidal effect of antibiotics, by 39.66% in the PM-T treatment, which was significantly higher than in the other treatments(12.38%-35.26%). Compared with other treatments, the antibiotics in the CHM-T treatment were more easily leached from the soil, with 9.91 mg of antibiotics in the leachate, which was significantly higher than the other treatments(P<0.05). TN, NH₄⁺-N, tetracycline, oxytetracycline, and chlortetracycline were the first principal component factors, accounting for 54.55% of the variation, and corresponding concentrations increased with soil depth. Based on these results, tetracyclines in pig manure tended to accumulate in soil and transfer vertically along with variations in the soil microbial community. For chicken manure, relatively high concentrations of tetracyclines were detected in the soil leachate, increasing the risk of water pollution.