Microplastics as a chronostratigraphic indicator in the sediments of the Urft reservoir

在中欧和世界范围内的河流系统在最近几十年到几个世纪里经历了迅速的变化。土地使用的变化以及气候变化导致了沉积物平衡和径流模式的急剧变化。然而，为了识别和量化近几十年来的地貌变化，合适的地质年代学标记是必不可少的。这些标志物是重要的，无论是量化的空间和时间域的变化，但也解开自然和人为的地貌过程。在此背景下，多年来一直在深入讨论沉积物中塑料或微塑料的存在。微塑料纯粹是人为的，自1950年以来在世界范围内大规模使用。然而，到目前为止，只有少数研究始终应用这一概念。因此，本项目研究了微塑料在河流沉积物中可用作年代地层标志物的程度。Urft水库的沉积物提供了一个极好的机会来测试微塑料作为年代地层标志物。乌夫特大坝建于1905年。由此形成的湖泊长12公里，最大体积为4550万立方公里。2020年11月，由于维修工作，其几乎完全排水。与Eifel-Rur水务委员会合作，对水库沉积物进行了密集取样。通过无人机勘测对沉积体进行了详细的空间记录。总共获得了10个芯，长度可达4 m。对于其中一个岩芯，根据铯-137确定了沉积物的年代。铯-137的第一次出现标志着从1952年开始的全球核武器试验，在240厘米的深度发现。这使得可以确定多个岩心沉积物中微塑料的下限，并及时对其进行精确分类。在下一步中，可以更详细地检查不同的聚合物。由于不同类型的聚合物是在不同时期开发的，因此它们也在不同时期被引入环境中。在Urft的调查现在将显示进入时间的差异是否反映在沉积物中，以及塑料是否也可以用于1950年之后的精确测年。该项目的目的是详细记录Urft水库沉积物中的微塑料，包括空间和时间，从而为塑料作为一种独立的测年方法在地貌沉积学研究中的应用提供了新的动力。

Fluvial systems in Central Europe, but also worldwide, have been subject to rapid change in recent decades to centuries. Changes in land use but also climatic changes have led to drastic alterations in the sediment balance and runoff patterns. However, for the identification and quantification of geomorphological changes in recent decades, suitable geochronological markers are essential. These markers are important either to quantify changes in the spatial and the temporal domain but also to disentangle natural and anthropogenic geomorphological processes. In this context, the occurrence of plastics or microplastics in sediments has been intensively discussed for several years. Microplastics are purely anthropogenic and have been used on a massive scale worldwide since about 1950. However, so far there are only a few studies that consistently applied this concept. Therefore, this project investigates the extent to which microplastics can be used as chronostratigraphic markers in fluvial sediments.The sediments of the Urft reservoir offer an excellent opportunity to test microplastics as a chronostratigraphic marker. The Urft dam was built in 1905. The resulting lake has a length of 12 km and a maximum volume of 45.5 million km³. In November 2020, it was almost completely drained for maintenance work. In cooperation with the Eifel-Rur Water Board, the reservoir sediments were intensively sampled. The detailed spatial recording of the sediment body was carried out by means of drone survey. A total of 10 cores with a length of up to 4 m were obtained. For one of the cores, a chronology of the sediments was established based on caesium-137. The first occurrence of caesium-137, which marks the beginning of worldwide nuclear weapons testing from 1952, is found at a depth of 240 cm. This makes it possible to determine the lower limit of microplastics in the sediments over several cores and to classify them precisely in time.In a further step, the different polymers are examined in more detail. Since different types of polymers were developed at various times, they were also introduced into the environment at different times. The investigations at the Urft will now show whether differences in the time of entry are reflected in the sediments and whether plastic can thus also be used for precise dating after the year 1950.The aim of the project is to record microplastics in the sediments of the Urft reservoir in detail, both spatially and temporally, and thus to provide new impulses for the use of plastics as an independent dating method in geomorphological-sedimentological research.