Dissipation and sequestration of veterinary medicines in soil under dynamic moisture conditions

在本研究单位的第一阶段，我们发现，磺胺嘧啶（SDZ）及其4-OH-代谢物在受控的实验室条件下与动物粪便一起施用时，会大量螯合在土壤中。N-Ac-SDZ迅速衰变为母体化合物。第二阶段的结果表明，封存过程是由熵驱动的，即，扩散到小空隙中。SDZ及其代谢物在田间条件下的消散可以通过对第一阶段实验室培养（10°C）和第二阶段围隔实验（21°C）得出的消散速率进行温度调节来合理预测。然而，田间试验的结果表明，在极端干燥和非常潮湿的条件下，偏离预测的耗散，这表明土壤水分对SDZ在土壤中的耗散和封存有显着的影响。因此，我们的项目的主要目标是阐明SDZ的现场封存的土壤水分变化的相关性。特别是，我们的目标是（i）量化到何种程度的干湿循环加速封存（ii）测试使用的SDZ的稳定同位素签名，以表征的“年龄”的SDZ污染，和（iii）完成运行实验的消散和封存的二氟沙星在现场条件下。我们将与项目A4一起在Merzenhausen试验场建立和协调一个中央田间试验II，并控制土壤湿度。我们的项目将负责在中心田间实验和伴随的中心实验室实验中定量土壤中SDZ浓度随时间的变化。

In the 1st phase of this Research Unit, we found that sulfadiazine (SDZ) and its 4-OH-metabolite are sequestered in soil in significant amounts when applied with animal manure under controlled laboratory conditions. N-Ac-SDZ decayed rapidly to the parent compound. The results of the 2nd phase suggested that the sequestration processes are driven by entropy, i.e., diffusion into small voids. Dissipation of SDZ and its metabolites under field conditions could be predicted reasonably well by temperature-adjustment of dissipation rates derived from the laboratory incubation of the 1st phase (10°C) and a mesocosm experiment of the 2nd phase (21°C). Nevertheless, the results of the field trial indicate a deviation from predicted dissipation at extremely dry and very wet conditions, suggesting a pronounced influence of soil moisture on dissipation and sequestration of SDZ in soil. It is therefore the major goal of our project to elucidate the relevance of changing soil moisture on the field sequestration of SDZ. In particular we aim at (i) quantifying to which extent drying-wetting cycles accelerate sequestration (ii) testing the use of the stable-isotope signature of SDZ to characterize the “age” of SDZ contaminations, and (iii) finalizing running experiments on the dissipation and sequestration of difloxacin under field conditions. We will establish and coordinate a central field experiment II at the Merzenhausen test site with manipulated soil moisture together with project A4. Our project will be responsible for the quantification of SDZ concentrations in soil over time in the central field experiment and the accompanying central laboratory experiment.