Degradation behavior of sulfadiazine in soils under different conditions

Abstract

This study investigated the degradation of sulfadiazine in three soils and also determined its sorption and hydrolysis behaviors as well. At the spike concentration of 10 mg/kg, the half-lives for sulfadiazine in the aerobic nonsterile soils ranged from 12 days to 18 days. Sulfadiazine was more persistent in the anoxic soils with the half-lives ranging between 57 days and 237 days and soil microorganisms played little role in the dissipation process under anoxic conditions. The decline in sulfadiazine concentrations was also observed in the sterile soils under aerobic conditions. Hydrolysis could not explain this phenomena as hydrolysis of sulfadiazine was pH dependent. Sulfadiazine only hydrolyzed to a very limited degree at acidic pH. Increased sorption was observed for sulfadiazine in soil 1 (pH 4.3) when the contact time increased to 14 days, but no significant increase in sorption was found for soil 2 (pH 7.2) and soil 3 (pH 8.5).

Keywords:

• Dissipation
• bound residues
• redox conditions
• sulfadiazine

Acknowledgments

The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (NSFC 40688001, 40771180 and 40821003). This is contribution no. IS1007 from GIGCAS.

Notes

^a OM represents the content of organic matter in soil.

^b CEC represents the cation exchanging capacity.

^c pH measured using soil to CaCl₂ solution (1:5, w/v).

^a Soil 1, soil 2 and soil 3 represent the three types of soils used in the study.

^b k represents the rate constant of the first order degradation kinetics (mg/kg/d).

^c t _1/2 represents half-life time of degradation.

∗ Unspiked soils were the soils without addition of sulfadiazine; spiked soils were the soils with sulfadiazine at a concentration of 10 mg/kg.