Degradation of sulfonamides in soils

The degradation of five veterinary sulfonamides,such as sulfadiazine,sulfamerazine,sulfamethazine, sulfadi-methazine,sulfamethoxazole,in different types of soil with and without light was studied by laboratory simulation method. The results indicated that the degradation of sulfonamides in soils followed the biexponential equation. Degradation trend presented two stages,previous stage of the degradation rate faster, while later stage was slower. Sulfonamides in Taihu paddy soil and northeast black soil degraded rapidly with DT 50 and DT 90 range of 5. 3 to 18. 0 days and more than 180 days,but which in Jiangxi red soil was more persistent with DT 50 and DT 90 range of 37. 4 to more than 180 days and more than 180 days. The light was less affected on the degradation of sulfonamides in Taihu paddy soil and northeast black soil,but it was obvious acceleration in Jiangxi red soil,with the half-life by 37. 4 to more than 180 days( dark) to speed up to 20. 0 to 58. 5 days( light). In addition,the degradation rate in soils more affected by soil clay content and organic matter content.