Dissipation And Adsorption Characteristics Of Antibiotics In Upland Agricultural Soils

The use of antibiotics not only improves the production performance of livestock and poultry but also has a series of effects on the ecological environment.A large portion of administrated antibiotics can not be absorbed animals and often enter agricultural land through manure application,potentially resulting in the pollution of soil and surrounding waters.The livestock and poultry industries are well developed in Zhejiang Province,and residues of sulfonamides,tetracyclines,quinolones,and chloramphenicol antibiotics in livestock and poultry manure have been frequently detected.Therefore,five upland agricultural soils,which have been applied with different fertilizers（chicken manure,pig manure,and chemical fertilizer）for a long term,were collected from Lin’an,Jiashan,Longyou,Kaihua,and Wucheng in Zhejiang and used as experimental soils.On one hand,the dissipation dynamics of five veterinary antibiotics[three sulfonamide antibiotics（sulfadiazine,sulfamethazine,and sulfamethoxazole）and two tetracycline antibiotics（oxytetracycline and deoxytetracycline）]widely used in livestock and poultry farming were studied by laboratory incubation experiment.On the other hand,the isotherm adsorption behavior of ten commonly used veterinary antibiotics[three quinolone antibiotics（norfloxacin,ciprofloxacin,and enrofloxacin）,two tetracycline antibiotics（oxytetracycline and deoxytetracycline）,three sulfonamides antibiotics（sulfadiazine,sulfamethazine,and sulfamethoxazole）,a chloramphenicol antibiotic（florfenicol）,and a macrolide antibiotic（tylosin）]were explored through batch experiment.Key soil properties and environmental factors that could affect the dissipation and adsorption of the antibiotics were identified in this study.The main results are as follows:（1）The laboratory incubation experiment showed that the dynamic change characteristics of five antibiotics（sulfonamides and tetracyclines）in the soils applied with chicken manure and the soils applied with pig manure were as follows:The content of antibiotics showed a sharp decline in the first 30 days of incubation;after 30 days,the trend of antibiotic content was relatively flat.Soil p H and dissolved organic carbon（DOC）were the main factors that affected the dissipation of five antibiotics in manured soils.（2）A batch balancing experiment showed that quinolones(norfloxacin K_f:333.77-5155.77 mg^1-1/n·L^1/n·kg^-1;ciprofloxacin K_f:318.62-7273.89 mg^1-1/n·L^1/n·kg^-1;enrofloxacin K_f:277.47-1822.28 mg^1-1/n·L^1/n·kg^-1)and tetracyclines(oxytetracycline K_f:206.14-2304.65 mg^1-1/n·L^1/n·kg^-1;deoxytetracycline K_f:386.58-3027.33 mg^1-1/n·L^1/n·kg^-1)exhibited strong adsorption in the soils;the adsorption of tylosin varied in different soils(K_f:0.87-153.96 mg^1-1/n·L^1/n·kg^-1).The adsorption of sulfonamides(sulfadiazine K_f:0.16-5.57mg^1-1/n·L^1/n·kg^-1;sulfamethazine K_f:1.44-13.23 mg^1-1/n·L^1/n·kg^-1;sulfamethoxazole K_f:0.73-6.05 mg^1-1/n·L^1/n·kg^-1)and florfenicol(K_f:0.27-3.81mg^1-1/n·L^1/n·kg^-1)was weak,with florfenicol exhibiting the weakest sorption in the soils.Soil p H was the main factor affecting the adsorption of quinolones.Total organic carbon（TOC）and DOC were the main soil factors influencing the adsorption of tetracyclines and sulfonamides.DOC,electrical conductivity（EC）,and cation exchange capacity（CEC）were the main soil factors affecting the adsorption of florfenicol.The main soil factors influencing the adsorption of tylosin were p H,CEC,and DOC.（3）The application of manure could affect the dissipation and adsorption of antibiotics by changing soil p H,TOC,DOC,CEC,and EC.Moreover,the concentration and source type（chicken manure and pig manure）of fecal dissolved organic matter could affect the adsorption of antibiotics,and the effect of these factors varied with soil and antibiotic type.