Residues,Form Transformation And Ecotoxicity Of Sulfonamides In Environment

Sulonamides are synthetic antimicrobial agents,which are used in aquaculture,animal husbandry,and also as human medicines to treat many kinds of infection caused by bacteria and certain other microorganisms.Because sulfonamide antibiotics usually cannot be absorbed completely in the gut of the animals,a large proportion of parent compounds or acetylated metabolites have been excreted into environment through faeces and urine.As a result,sulfonamides were usually detected in the environment.Manure,soil and vegetable samples were collected from 13 different livestock farms of different sizes in Xinxiang of China,and the residues of three sulfonamides including sulfadiazine,sulfamonomethoxine,and sulfamethoxazole were analyzed by HPLC with fluorimetric detector.The results indicated that the concentration ranges of the three total sulfonamides in manure,soil and vegetable was 10.13-566.23μg·kg^-1,7.60-176.26μg·kg^-1 and ND-32.70μg·kg^-1,respectively.The mean concentrations were 219.71μg·kg^-1,70.73μg·kg^-1 and 7.08μg·kg^-1 for manure,soil and vegetables,respectively.The mean concentrations in soil were lower than the ecotoxic effect trigger value(100μg·kg^-1)set by the Veterinary Medicine International Coordination Commission,indicating the low risk for organisms in soil.The concentrations of three sulfonamides varied significantly in different kinds of vegetables and all were lower than the acceptable daily intake values(50μg·（kg·d）^-1)set by Joint FAO/WHO Expert Committee on Food Additives.But we cannot neglect the potential ecotoxicity and resistance for human via food chain.Form transformation and degradation of sulfadiazine and sulfamethoxazole were studied in artificial root exudates-soils and control-soil using batch approach.The results indicated that the percentages of organic solvent extractable,water soluble and bound residues were 86.5-98.5%,0.6-7.3% and 0.1-12.5% of the total residues,respectively.The organic solvent extractable residues were the main form in soils.The proportion of bound residues increased with the time and the formation of them was enhanced by the added artificial root exudates.The degradation of sulfonamides followed the first order reaction kinetics with correlation coefficient between 0.9273 and 0.9963.The added artificial root exudates accelerated the degradation of sulfonamides in soils.Form transformation and ecotoxicity of sulfonamides in root-soil interface of maize were studied by chemical analysis and luminescent bacteria toxicity assay.The results indicated that the contents and relative inhibition rate of water soluble residues in rhizoshpere soils were greater than that in non-rhizoshpere soils,while the contnts and relative inhibition rate of organic solvent extractable and bound residues in rhizoshpere c soils was lower than that in non-rhizoshpere soils.The toxicity of water soluble residues was less than the organic solvent extractable residues,and the bound residues showed the lowest toxicity to luminescent bacteria.The three forms of sulfonamides showed relatively lower toxicity to luminescent bacteria with the relative luminous intensity more than 70%.The contents and relative inhibition rate of water soluble and organic solvent extractable residues declined with the time,while the contents and relative inhibition rate of bound residues increased early and declined later.