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

中欧和世界各地的河流系统在最近几十年到几个世纪内都发生了迅速的变化。土地利用的变化以及气候的变化导致了泥沙平衡和径流模式的剧烈变化。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志是必不可少的。这些标记物对量化空间和时间领域的变化以及理清自然和人为地貌过程都很重要。在此背景下，沉积物中塑料或微塑料的存在已被广泛讨论了好几年。微塑料完全是人为的，大约从1950年开始在全球范围内大规模使用。然而，到目前为止，只有少数几项研究一致地应用了这一概念。因此，该项目调查了微塑料在河流沉积中作为年代地层标志的程度。Urft水库的沉积物为测试微塑料作为年代地层标志提供了一个极好的机会。乌尔夫特大坝建于1905年。由此产生的湖泊长度为12公里，最大容量为4550万千米。2020年11月，为了进行维护工作，它几乎完全被排干了。与艾菲尔-鲁尔水务局合作，对水库沉积物进行了密集采样。通过无人机测量，对沉积体进行了详细的空间记录。共获得了10个岩芯，长度可达4米。对于其中一个岩心，根据铯-137建立了沉积物的年代学。铯-137的首次发现是在240厘米深的地方发现的，这标志着自1952年以来世界范围内核武器试验的开始。这使得能够确定几个岩芯沉积物中微塑料的下限，并在时间上准确地对它们进行分类。在进一步的步骤中，对不同的聚合物进行了更详细的检查。由于不同类型的聚合物在不同的时期被开发出来，它们也在不同的时期被引入环境中。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1950年之后塑料是否也可以用于精确的测年。该项目的目的是在空间和时间上详细记录URFT水库沉积物中的微塑料，从而为在地貌-沉积学研究中使用塑料作为一种独立的测年方法提供新的推动力。

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.