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

在本研究单元的第一和第二阶段，我们开发了磺胺嘧啶（SDZ）在土壤中的吸附模型，并评估了SDZ在土柱和蒸渗仪实验中的迁移。这些调查表明，SDZ及其代谢物的浸出是强烈的瞬时吸附反应和长期降解的可变大气边界条件下的蒸渗仪的影响。有强烈的迹象表明，瞬时吸附和SDZ的降解都受到土壤水分。因此，我们的子项目的第三阶段的目标是量化土壤水分对SDZ的快速吸附，降解和运输的影响，在完成正在进行的实验后，在中央现场实验和伴随的实验室实验中，解决了在蒸渗仪中的二氟沙星的运输和命运。中心田间实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，将包括i）环境土壤湿度和温度条件，ii）接近40%持水量的恒定土壤湿度条件，iii）土壤湿度的极端变化。通过使用透明屋顶和灌溉，可以实现恒定的土壤湿度和极端的土壤湿度变化。单独的实验室实验将研究SDZ在不同结合强度形式下的快速吸附，以及在土壤含水量为0%（风干）、20%、50%和100%最大持水量时以及在土壤泥浆（土壤与溶液的比例，w：v，1：5）中的降解。这些实验将有助于测试的中心假设，干燥和再润湿周期增加转化反应，封存，和NER形成SDZ，并减少其影响相比，静态水分条件下，和扩展的假设，在水饱和的条件下，有一个显着的矿化SDZ残留物的时间尺度上的几个月（90天）在给定的温度。

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.