| Manure application is indispensable for the high-yield and good-quality vegetable production andthe nutrient recycling. The residual antibiotics in the manure from intensive farming, however, willcause pollution in vegetable products and soil, leading to potential threatens to soil environment andpeople health. The usually reported analytical methods for antibiotics are not satisfactory as the lowerreproducibility between them and the complexity of soil properties and manure sources. There are notenough investigation to the antibiotic residues in soil and manure, and few reports about the effect ofcombined application of chemical N with different sources of organic N (pig manure and straw) on theaccumulation of antibiotics in soil. In this study, the common used solid phase extraction plus highefficient chromatography method (SPE-HPLC) for the analysis of three kinds of tetraclyinces(TCs),oxytetracycline(OTC), tetracycline(TC) and chlortetracycline(CTC) in soils and manure, was optimized,the residual status of tetracyclines in soils and manure in Tianjin was investigated using the optimizedmethod, and the effect of different combined application patterns of chemical fertilizers and organicmaterials on the change of soil tetraclyinces levels during the growing stages of tomato and celery werestudied using the long-term located trials. The acquired results will provide solid supports for theestablishment of efficient and environmental friendly fertilization patterns aiming high-yield andprofitable protected vegetable production. The main advances obtained in this study are summarized asfollows:1. Optimization of the protocol using SPE-HPLC for the extraction and analysis of residualtetracyclines in soils and manureIn this study, the SPE-HPLC method of tetraclyinces was optimized from these several as: the samplesof soils and manure were extracted with mixture of equal volume of0.1mol/L Na2EDTA-McIlvainebuffer solution and acetone containing20%of0.01mol/L dibocarxyl in methanol. The extractingsolution were then loaded on HLB cartridges for soil samples and SAX-HLB cartridges for pig andchicken manure samples. The retained analyte in the cartridges was eluted with acetone containing20%of0.01mol/L dicarboxyl in methanol. The mobile phase used in HPLC for soil samples was0.01mol/Ldicarboxyl-acetonitril-methanol（V/V/V：76/16/8）under constant condition, and for manure was:0~12min，16%acetonitril+8%methanol；12~16min，25%acetonitril+15%methanol；16~30min，16%acetonitril+8%methanol. The obtained method recovery of OTC, TC and CTC in soils is respectively80.1%,61.2%and52.1%, and the recovery of TCs in pig and chicken manure was respectively61.2%-94.2%and69.9%-81.8%. The optimized method recovery was applicable, and greatly reducesthe sample analysis time and promotes analysis efficiency.2. Status of tetracyclines in soils and manure in TianjinThe residual status of tetracyclines in soils and manure in Tianjin was investigated using theoptimized method. In the surveyed manure samples from intensive piggeries and poultries, CTC wasdetected in78%of manures with the highest values of563.8mg/kg, and OTC and TC are detected in56%of manure samples with the highest values of34.8and22.7mg/kg, respectively. TCs were alsodetected in the market manure in Tianjin with similar residual levels and percentages to those in themanure samples. The total percentage of soils from vegetable fields containing detectable TCs was64%of the surveyed soils, and those for OTC, TC and CTC were18%,36%and32%, respectively. The highest values for OTC, TC and CTC were105.6,196.7and477.8μg/kg in dry weight, respectively.The residual levels in the vegetable soils for greenhouse with wall and greenhouse without wall werehigher than those in the vegetable soils for open fields. In27.3%of the surveyed vegetable soils, theamounts of single tetracyclines antibiotics residue exceeded100μg/kg, the trigger lines causingecological safety.3. The effect of combined application of organic manure and chemical fertilizers on thetetracyclines residue in soilsUsing the long-term fertilizer experiment on vegetables under protected condition, the yields andprofits of tomato and celery were investigated with different combined application treatments of organicmanure and chemical fertilizers, and the variation of soil chlortetracycline residual levels during thegrowth seasons,(the sixth tomato crop and the seventh celery crop), were studied.(1) Characteristics of soil tetracyclines residue variation during the growing stagesIn the chosen sixth tomato and seventh celery growing season, neither oxytetracycline nortetracycline was monitored in all the sampling growth stages with the designed fertilizer treatments,only chlortetracycline monitored in different levels. In the treatments containing pig manure, the soilresidual chlortetracycline levels showed close relation with the mineralization of pig manure afterincorporated into soil: increasing at first and then decreasing gradually. The higher soil chlortetracyclineresidual levels appeared at the40days after manure application, then start degraded process and to avery low level at the end of growing season.(2) The relation of residual chlortetracycline in soil with pig manureThere is a certain amount of tetracycline accumulation after3years and twice applications per yearof pig manure, depending on the leftover from the former crop and the new released amount. When thepig manure use amount was as high as the conventional farmer’s level, the residual chlortetracyclinelevel was significantly higher than the decreased fertilizer treatments in the experiment, the residuallevels from base application of pig manure to flowering stage in the sixth tomato season even exceededthe trigger line for the ecological safety proposed by the Europe Union, although the residualchlortetracycline level decreased gradually to a low level at last.(3) Effect of applying crop straw on the degradation of chlortetracycline in soilApplying crop straw could stimulate the degradation of chlortetracycline in soil. With the sameamount of pig manure use, the residual soil chlortetracycline was significantly lower in the strawcontaining treatment (2/4chemical N+1/4pig manure N+1/4straw N) than in the no straw treatment(3/4chemical N+1/4pig manure N) at all the sampling time in the annual tomato and celery rotationcycle. The decreased rate was100%,24.8%,27.9%and4.9%at before basal fertilizer application,40days (flowering stage),90days (full fruit stage) and115days (last stage of picking) after basalapplication respectively in tomato crop, and the decrease rate was100%and8.5%at before basalfertilizer application and40days after application respectively in celery crop.(4) Optimal combined application pattern of organic manure and chemical fertilizers withhighest yield and profit and least soil chlortetracycline residue Under this experimental condition, the best combined application pattern of organic manure andchemical fertilizers for the highest yields and profits was3/4chemical N+1/4manure N at the first4vegetable production. Since the fifth cultivation, treatment2/4chemical N+1/4manure N+1/4strawN showed the best efficiency as this patter could increase soil organic matter content thus provide asteady N supply for vegetable growth. |
PDF Full Text Request