Problem statement

Excessive levels of nitrogen (N) and phosphorus (P) in our freshwater systems threaten the health of aquatic ecosystems. In recent decades, various sources of inputs have been prevalent, and various mitigation measures have been implemented that nevertheless have often failed to achieve water quality objectives. Because of these changes in inputs and mitigation measures, N and P concentrations have changed over time. In some cases, these changes differ substantially among catchments because of their different histories and characteristics. In addition to these long-term trends in individual nutrient concentrations, it is crucial to better understand the stoichiometric ratio of N and P (N:P) at large scales, as it is critical to ecosystem functioning and eutrophication. At this point, there are very few studies that look at this ratio on a larger scale, thus the knowledge gained from this thesis has the potential to substantially contribute to our understanding of water quality trajectories across Western Europe.

Ebeling et al. (2021)

Aim

The aim of this thesis is to characterize trajectories of N:P ratios across catchments in Germany and France (and possibly even beyond) and to identify spatiotemporal patterns and potential drivers.

Method

Large sample catchment analysis and statistics in R. Data-driven modelling and potentially machine learning to identify relatiships between water quality patterns and catchment characteristics.

Supervision

Pia Ebeling (Department for Hydrogeology, UFZ, Leipzig) and Carolin Winter

Special note

This work will be conducted at the UFZ in Leipzig under supervision of Pia Ebeling (UFZ Leipzig) and Carolin Winter (Uni Freiburg). The student is encouraged to spent at least part of her/his time in Leipzig (which is also a nice opportunity to get to know the UFZ). Students interessted are welcome to approach and talk to Carolin Winter to disuss the procedure and requirements.

Contact

Carolin Winter carolin.winter@hydro.uni-freiburg.de Tel. +49 (0)761 / 203-3509

Pia Ebeling pia.ebeling@ufz.de Tel. +49 (0)341 / 235 1986

Language

Englisch

Literature

• Ebeling, P., Dupas, R., Abbott, B., Kumar, R., Ehrhardt, S., Fleckenstein, J. H., & Musolff, A. (2021). Long‐Term Nitrate Trajectories Vary by Season in Western European Catchments. Global Biogeochemical Cycles, 35(9), e2021GB007050.
• Ebeling, P., Kumar, R., Lutz, S. R., Nguyen, T., Sarrazin, F., Weber, M., … & Musolff, A. (2022). QUADICA: water QUAlity, DIscharge and Catchment Attributes for large-sample studies in Germany. Earth System Science Data, 14(8), 3715-3741.
• Wachholz, A., Dehaspe, J., Ebeling, P., Kumar, R., Musolff, A., Saavedra, F., Winter, C., … & Graeber, D. (2023). Stoichiometry on the edge—humans induce strong imbalances of reactive C: N: P ratios in streams. Environmental Research Letters, 18(4), 044016.