Microbial Degradation of Sulfonamides in Soils

Through indoor simulation degradation experiments,microbial degradation of six sulfonamides in sandy soil was carried out to investigate the influence of soil types,concentrations and temperatures on degradation of sulfadiazine. The results indicated that the optimum degradation conditions for sulfadiazine in three soils were as follows: sandy soil,temperature 308.15 K and concentration 25 mg·kg-1 within the scope of this experiment. Degradation of sulfadiazine in sandy soil was slightly faster than in loam and clay,respectively. Degradation rate constant of sulfadiazine in sandy soil increased with increasing temperature,but it decreased with the increase of temperature when the temperature was over some temperature. The degradation rate constant increased with decreasing initial concentration,indicating that the bioactivity of the degrading microorganisms in sandy soil was sensitive to sulfadiazine concentration and temperature. The microbial degradation of six sulfonamides in sandy soil were slow,with the degradation rate constants order SMD = SMX SDM SMM SD SMT. Degradations of sulfonamides in sandy soil were mainly caused by non-biological degradations such as hydrolysis and chemical degradation,rather than by microbial degradation,which mostly related to their strong antibacterial activities.