Quantification of Trace Contaminant Emissions on the River Basin Scale

Rivers around the world are under pressure from chemical pollution originating from agriculture,industry and settlements. This pollution, among others, by trace contaminants – includingpotentially toxic elements (PTE) and persistent ”forever chemicals” – threatens ecosystemsand human water use. Effectively managing this pollution requires a river basin perspective,as rivers naturally integrate all upstream contaminant inputs. By understanding contaminantemission quantities and their pathways across entire catchments, managers can prioritise effortsfor contamination monitoring and target emission mitigation measures where they are mostneeded. This thesis develops and applies innovative methods to quantify trace contaminantemissions via different pathways at the river basin scale, providing scientific tools for effectivepollution control in three complementary studies:Study 1 investigated the transport dynamics of PTEs during high-flow events in a lowlandriver catchment to improve monitoring strategies and emission modelling. Field sampling wasconducted at three sites during multiple flow events, analysing water samples for total anddissolved concentrations of 29 elements. Concentration of PTE in suspended particulate matter(SPM) were derived by calculation and compared to riverbed sediment and land-use stratified soilsamples. The study found that while the quantity of transported SPM was the primary driver ofPTE transport during events, significant changes in SPM composition also occurred. Notably,concentrations of Sb and Cu in SPM decreased as events progressed, suggesting a ”first flush”contribution from sources like road dust containing brake wear particles. Furthermore, PTEsand a few other elements showed systematic enrichment in SPM compared to catchment soils,particularly for Ag, Bi, Zn, Cu, P, Sb, Ni and Li, indicating anthropogenic sources. However,sediment fingerprinting to identify specific SPM sources in the catchment was deemed unfeasibledue to low variability of concentrations in potential source materials.Study 2 addressed the critical need for accessible and harmonised data to support pathwayorientedemission inventories for trace contaminants in the Danube River Basin (DRB). Itestablished a relational database integrating fragmented concentration measurements and essentialmetadata from various environmental compartments (surface water, groundwater, wastewater,soil, atmospheric deposition, stormwater runoff) across multiple countries. The database waspublished online in a research data repository under a Creative Commons license, applying FAIRprinciples (Findable, Accessible, Interoperable, Reusable) to facilitate widespread reuse. Analysisrevealed severe imbalances: surface water and groundwater data dominated while atmosphericdeposition, stormwater runoff, and soils were under-represented; spatially, coverage was extensivein Austria, Germany, and Hungary but limited elsewhere in the DRB primarily to compartmentsmonitored under EU legislation. The database identified critical gaps caused by inconsistentmetadata and suboptimal data storage, enabling prioritisation of future monitoring efforts andinforming recommendations for a harmonised transnational monitoring programme coveringtributaries and under-represented pathways.Study 3 applied a pathway-oriented approach using the MoRE model to quantify emissions andriver concentrations of two prevalent ”forever chemicals” – perfluorooctanesulfonic acid (PFOS)and perfluorooctanoic acid (PFOA) – across Austria, supported by tailor-made monitoring. Theanalysis revealed different pathway contributions: PFOS emissions were predominantly drivenby wastewater treatment plants (WWTPs), whereas PFOA exhibited greater contributions from diffuse pathways like surface runoff and groundwater. Regional patterns showed elevatedconcentrations for both substances in eastern Austria, where the dilution capacity of riversis limited, alongside a major PFOA hotspot near the legacy industrial PFOA production sitein Gendorf, Germany. The model demonstrated markedly better performance than previousmodel studies using generalised inputs (e.g., population-based emissions). This enabled a reliableidentification of priority areas and evaluation of scenarios on mitigation measures, such asadvanced wastewater treatment, demonstrating its value for strategic management of persistentpollutants.This thesis establishes a comprehensive framework for quantifying trace contaminant emissionsin river basins, integrating process understanding, data management, and pathway-orientedmodelling. By advancing methodologies for emission validation, transnational data infrastructure,and spatially resolved pathway analysis, it provides scientifically robust tools to identify pollutionhotspots and prioritise mitigation efforts. The consistent application of open-source tools (R,PostgreSQL, MoRE) and advanced statistical methods ensures transparency and reproducibility,supporting evidence-based river basin management. Collectively, this work demonstrates howpathway-focused emission quantification can help to direct pollution control resources where theyyield the greatest environmental benefit.