Transport of veterinary medicines from soils to groundwater under variable soil moisture and temperature conditions

在本研究的第一阶段和第二阶段，我们建立了磺胺嘧啶(SDZ)在土壤中的吸附模型，并评估了SDZ在土柱中的迁移和蒸渗仪实验。这些研究表明SDZ及其代谢物在蒸渗仪上的淋溶受瞬时吸附反应和在不同大气边界条件下的长期降解强烈影响。有强烈的迹象表明，SDZ的瞬时吸附和降解都受到土壤水分的影响。因此，我们子项目拟议的第三阶段的目标是在完成正在进行的关于地氟沙星在蒸渗仪中的传输和去向的实验后，在中央田间实验和伴随的实验室实验中量化土壤水分对SDZ的快速吸收、降解和传输的影响。中央田间试验将由我们的子项目与子项目A3在Merzenhausen试验场合作建立和进行，将涵盖i)环境土壤水分和温度条件，ii)接近持水量40%的恒定土壤水分条件，以及iii)土壤水分的极端变化。使用透明屋顶和灌溉将实现恒定的土壤水分和极端变化的土壤水分。单独的实验室实验将研究SDZ以不同结合强度的形式快速吸附，以及在土壤水分含量为0%(风干)、20%、50%和100%的最大持水量以及在土壤浆液中(土液比，w：v，1：5)时的降解情况。这些实验将有助于检验中心假设，即与静态水分条件相比，干燥和重新湿润循环增加SDZ的转化反应、隔离和NER形成，并降低其影响，以及扩展的假设，即在水分饱和条件下，在给定温度下，SDZ残留物在数月(90天)的时间尺度上有明显的矿化。

During the 1st and 2nd phase of this Research Unit we developed a model for sulfadiazine (SDZ) sorption in soil and evaluated SDZ transport in soil column and lysimeter experiments. These investigations showed that leaching of SDZ and its metabolites is strongly influenced by instantaneous sorption reactions and long-term degradation under variable atmospheric boundary conditions in lysimeters. There are strong indications that instantaneous sorption and degradation of SDZ are both affected by soil moisture. The goal of the proposed 3rd phase of our subproject is therefore to quantify soil moisture effects on the fast sorption of SDZ, its degradation, and transport in a Central Field Experiment and accompanying laboratory experiments after finalizing ongoing experiments addressing the transport and fate of difloxacin in lysimeters. The Central Field Experiment, which will be established and conducted by our subproject in collaboration with subproject A3 at the Merzenhausen test site, will encompass i) ambient soil moisture and temperature conditions, ii) constant soil moisture conditions close to 40% of the water holding capacity, and iii) extreme variations of soil moisture. Constant soil moisture and extreme variations of soil moisture will be achieved using transparent roofs and irrigation. Individual laboratory experiments will investigate the rapid sorption of SDZ in forms of different binding strength as well as its degradation at soil water contents of 0% (air-dried), 20%, 50%, and 100% of the maximum water holding capacity and in soil slurries (soil to solution ratio, w:v, 1:5). These experiments will contribute to testing the central hypothesis that drying and re-wetting cycles increase transformation reactions, sequestration, and NER formation of SDZ, and reduce its effects compared to static moisture conditions, and the extended hypothesis that under water saturated conditions, there is a pronounced mineralization of SDZ residues on time scales of months (90 days) at given temperature.