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Untangling the waves: decomposing extreme sea Levels in a non-tidal basin, the Baltic Sea
No full textGeoreferenzierung von 3D-Unterwasserstrukturen mittels Photogrammetrie durch wissenschaftliche Taucher
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Einfluss der räumlichen Variabilität von Bodeneigenschaften auf die Bestimmung von Versagensstellen von Küstenschutzbarrieren bei extremen Sturmfluten
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Das Info-Magazin der BAW
No full textFokusthema: Strategische Ressourcenplanung für den Erhalt wasserbaulicher Anlage
Konzepte für die Probenahme und Analyse von Mikroplastikpartikeln in Flussbettsedimenten und Grundwasser
No full textAlthough microplastic particles (MPs) are a ubiquitous and globally emerging anthropogenic pollutant in freshwater environments, little is known about their fate and behavior at the surface water–groundwater interface, a critical zone also for drinking water production. Groundwater is often considered pristine and less contaminated by MPs than surface water or fluvial sediments. For particulate contaminants as diverse as MPs, accurate and reliable analysis is challenging. Despite the wide range of techniques available, there is no one-size-fits-all or standardized method for sampling and detecting MPs in the environment. The unique capabilities and limitations of the various techniques available need to be evaluated and adapted in order to further develop appropriate approaches for the analysis of MPs in surface water, riverbed sediments and groundwater.
This PhD thesis investigated the occurrence and fate of MPs at the surface water–groundwater interface to better assess the risk of MPs reaching drinking water supplies. To this end, comprehensive sampling and analytical concepts tailored to the accurate analysis of small MPs (< 20 µm) in groundwater and the relatively fast and unelaborate analysis of MPs in riverbed sediments were developed and applied in the field for data collection. A validated analytical workflow combining fractionated filtration sampling with semi-automated Raman microspectroscopy (µ-Raman) detection was developed for the analysis of small MPs (down to 5 µm) in groundwater. These small MPs are of particular toxicological relevance and exhibit higher mobility in porous media. A mean MP concentration of 66 ± 76 MP/m3, consisting mainly of polyethylene (PE, ~86%) and MPs < 20 μm (~79%), was found in groundwater and raw drinking water, indicating that MPs from groundwater sources may pose a risk to drinking water. River water and groundwater are hydraulically connected reservoirs, whereby riverbed sediments can act as potential retention reservoirs or transport pathways for MPs from river to groundwater. The depth-specific occurrence and distribution of MPs in deep riverbed sediments under permanent losing stream conditions was investigated to gain insight into their fate, transport and retention behavior in freshwater systems. Undisturbed and water-saturated sediment cores were obtained by freeze coring. The extracted MPs (≥ 100 µm) from the sediment were detected by near-infrared (NIR) imaging spectroscopy and complemented by polymer mass analysis using thermoanalytical methods (TAM). MPs were found throughout the riverbed down to 100 cm in sandy sediments (~21.7 ± 21.4 MP/kg) and down to 140 cm in gravel sediments (~3.1 ± 2.3 MP/kg). This emphasizes the continuous and widespread MP pollution of riverbeds. In gravel sediments, even MPs as large as 676 µm are transferred directly from the river to the groundwater without significant retention in the gravel riverbed sediments. This indicates a potential risk of MP transfer to groundwater via bank filtration and highlights the urgent need for a better understanding of MP mobility at the surface water–groundwater interface. In contrast, a more complex distribution of MPs was found in sandy sediments, suggesting a sophisticated interplay and superposition of driving processes such as infiltration, retention, and relocation. Based on the observed characteristic MP distributions, the use of MPs as a potential environmental process marker to infer the controlling processes for sediment dynamics in the riverbed was established in an initial conceptual approach. This approach has the potential to be applied to other river reaches and river sediment structures, offering new possibilities to explore sedimentation processes and complement chronological assessments in fluvial systems.
Overall, this PhD study makes an important contribution to the establishment of reliable and robust methods for MP sampling and analysis, and provides essential insights into the fate and behavior of MPs at the surface water–groundwater interface. It provides a sound basis for future research to gain a more comprehensive understanding of the fate and behavior of MPs in freshwater environments and the potential risk to drinking water supplies
