泰乐菌素和土霉素在农业土壤中的消解和运移

长期施用禽畜排泄物可导致抗生素在土壤中的积累, 对环境产生不良影响.为了解进入农田后抗生素的去向及残留动态, 选择2个典型农业土壤, 利用田间小区试验, 研究了田间实际状况下泰乐菌素和土霉素2种抗生素在土壤中的消解与运移行为.研究表明, 抗生素在土壤中的消解和运移与抗生素种类和土壤性质有关.抗生素在砂质土壤(清水砂)中的下移明显高于粘壤土(泥质田), 泰乐菌素在土壤中的垂直迁移强于土霉素.表层土壤中抗生素因降解和下移随时间逐渐下降, 消解速率在试验初期大于后期, 并且土霉素消解速率大于泰乐菌素.砂质土壤中抗生素的消解速率在试验初期明显高于粘壤土, 但至试验后期, 二者渐趋相似.田间条件下测得的抗生素消解速率明显低于实验室条件下, 这可能与抗生素进入田间深层土壤后稳定性增加有关.农田施用抗生素初期产生的径流中含较高浓度的抗生素, 但随时间(10 d之内)很快下降至检测下限以下; 试验初期径流中抗生素浓度为泰乐菌素大于土霉素, 砂质土高于粘壤土.

Dissipation and leaching of oxytetracycline and tylosin in typical agricultural fields

Antibiotics used in livestock production may be present in manure and slurry as parent compounds and/or metabolites. And environments may therefore be exposed to these antibiotics due to the application of animal manure in agricultural lands. In order to understand the environmental fate of two typical antibiotic compounds tylosin (C₄₆H₇₇NO₁₇) and oxytetracycline (C₂₂H₂₄N₂O₉HCl) in agricultural fields, liquid pig slurry was fortified with the antibiotics and then applied on field plots. The leaching, dissipation and surface runoff under field conditions were investigated. The results show that both degradation and leaching behaviors of the antibiotics are related with antibiotic kind and soil property. Vertical migration of the antibiotics is greater in sandy soils than in clay-loam soils. Transfer capacity of tylosin in soils is greater than that of oxytetracycline. Dissipation rate of antibiotics in surface layers is greater in sandy soils than in clay-loam soils at the initial stage, but eventually becomes similar for both soil types. Degradation rate of oxytetracycline in surface soils of both soil types is greater than that of tylosin. It is observed that degradation rates of the antibiotics measured under field conditions are much smaller than those measured under laboratory conditions. This suggests that antibiotics become stable as they enter into the deeper soil layer. Runoff losses of antibiotics mainly occur at the initial stage of manure application. Concentrations of the antibiotics in runoff are greater in sandy soils than in clay-loam soils. Tylosin poses a greater risk of ground surface water contamination.