Förster M, Laabs V, Lamshöft M, Groeneweg J, Zühlke S, Spiteller M, Krauss M, Kaupenjohann M, Amelung W
University of Bonn, Institute of Crop Science and Resource Conservation, Soil Science and Soil Ecology, D-53115 Bonn, Germany.
Environ Sci Technol. 2009 Mar 15;43(6):1824-30. doi: 10.1021/es8026538.
It is not the total but the (bio)accessible concentration of veterinary medicines that determines their toxicity in the environment. We elucidate the changes in (bio)accessibility of manure-applied sulfadiazine (SDZ) with increasing contact time in soil. Fattening pigs were medicated with 14C-labeled SDZ, and the contaminated manure (fresh and aged) was amended to 2 soil types (Cambisol, Luvisol) and incubated for 218 days at 10 degrees C in the dark. Antibiotic residues of different bioaccessibility were approached by sequential extractions with 0.01 M CaCl2 (CaCl2 fraction), methanol (MeOH fraction), and finally acetonitrile/water (residual fraction, microwave extraction at 150 degrees C). In each fraction, total radioactivity, SDZ, and its major metabolites were quantified. The results showed that both SDZ and,to a lesser extent 4-hydroxysulfadiazine (4-OH-SDZ) were rapidly reformed from N-acetylsulfadiazine (N-ac-SDZ) during the first 2-4 weeks after fresh manure application, i.e., the N-acetylated metabolite does not sequester in soil to a significant extent Yet, the water and methanol extractable SDZ and 4-OH-SDZ also dissipated rapidly (DT50 = 6.0-32 days) for the fresh manure treatment with similar rate constants for both soil types. In the residual fractions, however, the concentrations of both compounds increased with time. We conclude that the residual fraction comprises the sequestered pool of SDZ and its hydroxylated metabolite. There they are entrapped and may persist in soil for several years. Including the residual fraction into fate studies thus yields dissipation half-lives of SDZ which exceed those previously reported for sulfonamides by a factor of about 100.
决定兽药在环境中毒性的并非其总量，而是（生物）可利用浓度。我们阐明了施用于土壤中的磺胺嘧啶（SDZ）随接触时间增加其（生物）可利用性的变化。用14C标记的SDZ给育肥猪用药，将受污染的粪便（新鲜和老化的）添加到两种土壤类型（始成土、淋溶土）中，并在10摄氏度黑暗条件下培养218天。通过用0.01M氯化钙（氯化钙部分）、甲醇（甲醇部分）依次萃取，最后用乙腈/水（残留部分，150摄氏度微波萃取）来获取不同生物可利用性的抗生素残留。在每个部分中，对总放射性、SDZ及其主要代谢物进行定量。结果表明，在施用新鲜粪便后的前2 - 4周内，SDZ以及程度较轻的4 - 羟基磺胺嘧啶（4 - OH - SDZ）迅速从N - 乙酰磺胺嘧啶（N - ac - SDZ）中重新形成，即N - 乙酰化代谢物在土壤中不会大量螯合。然而，对于新鲜粪便处理，水和甲醇可萃取的SDZ和4 - OH - SDZ也迅速消散（DT50 = 6.0 - 32天），两种土壤类型的速率常数相似。然而，在残留部分中，两种化合物的浓度均随时间增加。我们得出结论：残留部分包含SDZ及其羟基化代谢物的螯合库。它们被困在那里，并可能在土壤中持续存在数年。因此，将残留部分纳入归宿研究得出的SDZ消散半衰期比先前报道的磺胺类药物的半衰期长约100倍。
