兽用抗生素在土壤中的衰减特征及其与土壤性状的关系研究

为了解土壤性状对兽用抗生素在土壤中的衰减及其生物有效性的影响，选择10 种理化性状相差较大的典型蔬菜地土壤，通过添加不同浓度（1、5、20 mg/kg）的4 种抗生素（土霉素、恩诺沙星、磺胺二甲嘧啶和泰乐菌素），在保持65%的土壤田间持水量和恒温(25℃)条件下培养，观察分析各类抗生素的残留量和生物有效性的动态变化。结果表明，试验初期（20 天内）土壤中抗生素的降解速率明显高于后期（50~100 天），进入土壤中的抗生素降解量随抗生素浓度的增加而增加，但降解比例却随抗生素添加量的增加而减小。4 种抗生素在土壤中的降解速率：磺胺二甲嘧啶＞恩诺沙星＞土霉素＞泰乐菌素。培养前期土壤中有效态抗生素含量随培养时间的下降比抗生素的残留量下降更明显。各类抗生素的降解率主要与土壤粘粒含量和氧化铁含量呈负相关，与土壤有机质含量存在轻微正相关，但与土壤pH 和CEC无明显相关。培养初期（5 天），土壤中有效态抗生素含量与粘粒含量、氧化铁含量呈负相关，与有机质含量呈现正相关；但随培养时间的增加，其与土壤粘粒含量、氧化铁含量的相关性有所降低。

Degradation Characteristics of Veterinary Antibiotics in Soils and Its Relationship with Soil Properties

In order to understand the effects of soil properties on degradation characteristics and bioavailability of veterinary antibiotics in soils, 10 kinds of typical vegetable soils with different physical and chemical properties were selected for the experiment. After adding 4 kinds of antibiotics (oxytetracycline, enrofloxacin, sulfamethazine and tylosin) at different concentrations (1, 5, 20 mg/kg) and adjusting moisture content of water holding capacity to 65%, soils treated with antibiotics were incubated at 25℃. Dynamic changes of residue and bioavailability of 4 kinds of antibiotics in soils were monitored. The results showed that the degradation rates of antibiotics in soils were significantly higher at the early stage of the experiment (＜20 days) than those of the later (50-100 days). Accumulated degradation amount of antibiotics in soils increased with the increasing concentration of antibiotics. But the degradation proportion decreased with the increasing amount of antibiotics. The degradation rate of 4 kinds of antibiotics in soils decreased in the order of sulfamethazine＞ enrofloxacin＞oxytetracycline＞tylosin. Decline of available antibiotics in soils was more obvious than residue of the corresponding antibiotics in the earlier stage. The degradation rates of all antibiotics were mainly and negatively correlated with the contents of clay and iron oxides, and slightly and positively correlated with the content of organic matter. No correlation was found between the degradation rate of antibiotics and pH, CEC. At the beginning of incubation (5 days), content of available antibiotics was negatively correlated with the contents of clay and iron oxides, and positively correlated with the content of organic matter. However, these correlations decreased with the incubation time.