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

在本研究单元的第一阶段，我们发现磺胺嘧啶(SDZ)及其4-羟基代谢物在受控的实验室条件下与动物粪便一起施用时，在土壤中有相当数量的隔离。N-Ac-SDZ迅速衰减到母体化合物中。第二阶段的结果表明，封存过程是由熵驱动的，即扩散到小空穴中。通过对实验室培养的第一阶段(10℃)和第二阶段(21℃)的中温实验得出的耗散率进行温度调整，可以很好地预测SDZ及其代谢物在野外条件下的耗散。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，SDZ的消散与预测的结果有偏差，这表明土壤水分对SDZ在土壤中的消散和固定有显著的影响。因此，我们项目的主要目标是阐明土壤水分变化与SDZ田间封存的相关性。特别是，我们的目标是(I)量化干湿循环加速隔离的程度；(Ii)测试使用SDZ的稳定同位素特征来表征SDZ污染物的“年龄”；以及(Iii)完成关于现场条件下地氟沙星的消散和隔离的运行实验。我们将在Merzenhausen试验场建立和协调一个中央田间试验II，与A4项目一起，利用操纵的土壤水分。我们的项目将负责在中央野外实验和伴随的中央实验室实验中，对土壤中SDZ浓度随时间的变化进行量化。

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.