Characterization of non-extractable ¹⁴C- and ¹³C-sulfadiazine residues in soil including simultaneous amendment of pig manure

Abstract

Recently, we reported on soil fate of SDZ residues amended with pig manure treated with ¹⁴C-labeled sulfadiazine (¹⁴C-SDZ). The first objective of the present study was to determine whether this strategy can be substituted by application of ¹⁴C-SDZ to soil. The second objective was to characterize non-extractable SDZ residues by fractionation, size exclusion chromatography (SEC) and solid state ¹³C-NMR. The fate of ¹⁴C-SDZ was examined for 28 d, using two soils with and without amendment of pig manure. Mineralization of ¹⁴C-SDZ was low; extractable residues decreased to 7–30%. Compared to the previous study, results were similar. ¹⁴C-SDZ derived bound radioactivity was found in HCl-washings, fulvic, humic acids and humin. According to SEC, one bound ¹⁴C portion (70%) co-eluted with fulvic acids (above 910 g mol⁻¹); the other consisted of adsorbed/entrapped ¹⁴C-SDZ. The ¹³C-SDZ study was performed for 30 d; humic acids were examined by ¹³C-NMR. A signal (100–150 ppm) was referred to ¹³C-SDZ. SEC and ¹³C-NMR demonstrated rapid integration of SDZ into humics.

Keywords:

• ¹⁴C-labeled sulfadiazine
• ¹³C-labeled sulfadiazine
• manure
• soil
• metabolism
• non-extractable residues
• mineralization
• solid state ¹³C-NMR spectroscopy

Acknowledgments

We wish to thank the German Research Foundation (DFG) for financial support of the research unit (DFG For 566), BAYER HealthCare for providing the authentic SDZ reference and ¹⁴C-SDZ and Prof. Dr. R. Kreuzig (Institute of Environmental and Sustainable Chemistry, TU, Braunschweig, Germany) for providing the authentic pig manure.