Subject area

Stable isotopes of oxygen and hydrogen in the water molecule are a useful tool to investigate a broad range of ecohydrological processes. The use of stable isotopes of water has increased due to a recently lowered cost of analysis. This course is for students in science and engineering who are currently using or wishing to incorporate stable isotope data (mainly 18O and 2H) in their research. Applications of stable isotope approaches include, among others, the partitioning of precipitation into runoff, evaporation and plant transpiration (“blue” and “green” fluxes), the residence times of water in the subsurface and the spatio-temporal origin of water used by vegetation. The course will briefly teach aspects of sampling and analysis, followed by in-depth qualitative interpretation and model-aided quantitative interpretation of water stable isotopes data.

Guest lecturers

Research Scientist Paolo Benettin, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
Assitant Professor Scott T. Allen, Dept. of Natural Resources and Environmental Science, University of Nevada, Reno, USA

Content

1. Fundamentals of isotope hydrology and stable isotope geochemistry
2. Isotope composition of the atmosphere and hydrosphere
3. Stable isotopes as environmental tracers
4. Use of stable isotopes in ecohydrology
5. Use of stable isotopes in transport modeling
6. Retrieving and processing isotopic data from repositories
7. Stable isotope methods:
a) Young water fractions
b) End member splitting analysis
c) Implementations of the convolution integral with isotope data
8. Stable isotope fractionation models:
a) Rayleigh fractionation,
b) Craig-Gordon model,
c) Mixed Craig-Gordon and mass balance models,
d) Fractionation detrending.
9. Water sample collection and preparation for isotope analysis (field trip
and laboratory experience)

Teaching and learning methods

• In-person lectures by the teachers
• Exercise sessions with tutorials and data examples
• Workshop with students' own data/cases/future uses/ideas
• Practical work during field trip
• Group assignment with presentation

Learning Prerequisites

Students need some programming knowledge (any language like R, Python or Matlab is ok). Previous experience with stable isotope data is not mandatory but recommended.

Learning Outcomes

1. Learn the fundamentals of stable isotope (18O, 2H) geochemistry
2. Retrieving isotope data from the main data repositories and conduct
initial processing of these data
3. Knowledge of stable isotope methods for
a) Quantification of water residence times,
b) Quantification of evaporation losses,
c) Rainfall partitioning into “blue” and “green” fluxes.
4. Implementing isotope fractionation models
5. Implementing isotope-based methods for ecohydrologic investigation
6. Conduct collection and preparation of water sample for stable isotope
analysis
7. Learn the functioning of a Laser Spectrometer (Picarro CRDS) and learn
how to handle the instrument’s output data files.

Literature

• Allen, S. T., Kirchner, J. W., Braun, S., Siegwolf, R. T. W., & Goldsmith, G. R. (2019). Seasonal origins of soil water used by trees. Hydrology and Earth System Sciences, 23(2), 1199–1210. https://doi.org/10.5194/hess-23-1199-2019.
• Benettin, P., Volkmann, T. H., Freyberg, J. von, Frentress, J., Penna, D., Dawson, T. E., & Kirchner, J. W. (2018). Effects of climatic seasonality on the isotopic composition of evaporating soil waters. Hydrology and Earth System Sciences, 22(5), 2881–2890. https://doi.org/10.5194/hess-22-2881-2018.
• Gat, J. R. (1996). Oxygen and hydrogen isotopes in the hydrologic cycle. Annual Review of Earth and Planetary Sciences, 24(1), 225–262. https://doi.org/10.1146/annurev.earth.24.1.225.
• Gonfiantini, R. (1986). Environmental isotopes in lake studies. In P. Fritz & J. Ch. Fontes (Eds.), The Terrestrial Environment, B (pp. 113–168). Elsevier. https://doi.org/10.1016/B978-0-444-42225-5.50008-5.
• Kendall, C., & McDonnell, J. J. (1998). Isotope tracers in catchment hydrology. Elsevier, Amsterdam. https://doi.org/10.1016/B978-0-444-81546-0.50001-X.
• Rothfuss, Y., Quade, M., Brüggemann, N., Graf, A., Vereecken, H., & Dubbert, M. (2021). Reviews and syntheses: Gaining insights into evapotranspiration partitioning with novel isotopic monitoring methods. Biogeosciences, 18(12), 3701–3732. https://doi.org/10.5194/bg-18-3701-2021.

Preparation and self study

Prior to the course, students are expected to study preliminary teaching material and literature (that will be sent in advance) and to prepare a short presentation of their project/data/ideas. During the course students are expected to study the material and complete the proposed exercises. After the course they are expected to hand in a report and code for their assignment.

Exam form: Individual Report (passed/not passed)
Criteria for assessment: Active participation during course.
Deadline for registration: 17. September 2022
Venue address: Øster Voldgade 10, 1350 Copenhagen K, Denmark
Course hours: 9-17:30

Workload:
Preparation and Self-Study: 60
Course hours: 45
Evaluation / reporting: 20
Total/ ECTS: 5 ECTS

(1 ECTS corresponds to approx. 25-28 working hours)

Day 1 morning:
• Round of introduction,
• Basics of isotope hydrology
• Basics of stable isotope chemistry

Day 1 afternoon:
• Hydrologic data repositories (navigating and retrieving data)
• Isotope data repositories and Handling (navigating and retrieving data)

Day 2 morning:
• Fieldtrip with experimental data collection and sample handling
• Group Photo

Day 2 afternoon:
• Discussion of students’ data and topics

Day 3 morning:
• Stable isotope fractionation and related models
• Main techniques to measure stable isotopes

Day 3 afternoon:
• Visit to NBI's isotope laboratory
• Processing Picarro instrument data
• Application of fractionation models

Day 4 morning:
• Hydrologic and transport processes,
• Stable isotope ecohydrology

Day 4 afternoon:
• Case studies
• Work on group assignment
• Social activity: dinner in the evening

Day 5 morning:
• Frontiers in Isotope Hydrology
• Exercises and applications

Day 5 afternoon:
• Groups present projects
• Course evaluation (SCIENCE PhD School evaluation form)
• Concluding remarks