Searching for the bomb spike in Danube river sediments: Extracting the anthropogenic impact of Vienna

The Anthropocene, the strongly debated potential new unit of the Geological Time Scale, describes the intensified anthropogenic influence on the environment and geological processes, and its traces in geological archives. Regional studies characterizing the growth of human impact, the Anthropocene transformation, are scarce, especially for urban or per-urban environments.In this project, we investigate the anthropogenic impact of the metropolis Vienna on its peri-urban environment and the proposed beginning of the Anthropocene epoch in the 1950s CE by applying sedimentological and geochemical methods. In previous studies (Wagreich et al. 2022), the authors were able to successfully detect the human influence in urban sedimentary archives of Vienna (anthropogenic coarse sediments) using artificial isotopes and anthropogenic trace metals. For our project, we extend the study area from Vienna to the city of Hainburg to investigate Vienna’s anthropogenic impact in both anthropogenic and natural sediments downstream the Danube river. In this area, direct human intervention in the environment, such as ground excavations, backfill and damming, is highly variable, from locally strong (e.g., hydro-power dams, airport constructions), to not existing (National Park Donau-Auen), thus offering a suitable location to trace and quantify the extent of anthropogenic impact.Within petrographic facies, sedimentological and geochemical markers are applied to characterize the anthropogenic strata in this area: The archive of fine-grained natural Danube deposits, i.e. erosional profiles and sediment cores, is analysed for trace metals, artificial radiogenic isotopes, and microplastics with the aim (i) to disentangle the anthropogenic fingerprint of Vienna from the sediment, (ii) to identify and evaluate the proposed Anthropocene geological boundary around 1950 CE, and (iii) to evaluate a potential correlative stratigraphic reference section section/ point for the Anthropocene downstream of Vienna. Finally, the Carnuntum-Vienna Anthropocene field lab offers the opportunity to integrate environmental systems modelling with an Anthropocene equation approach for the temporal and spatial growth of the anthropogenic layers (iv).