Stable isotopes in Earth Sciences

Course goals

Content

Course content

Theoretical and methodological foundations:

1. basic terminology;
2. principles behind mass spectrometry;
3. reporting conventions;
4. isotope effects: kinetic versus equilibrium isotope fractionation (Rayleigh plot, thermometry);
5. mass balances (Keeling plot, stable isotope probing).

Diverse applications of stable isotopes in Earth sciences:

1. atmospheric carbon cycle, role of natural and anthropogenic activity. Tracers: ¹³C in CO₂, ¹³C and D in CH₄.
2. hydrological cycle, and its link to paleo-thermometry. Tracers: ¹⁸O and D in H₂O, clumped isotopes (¹³C and ¹⁸O) in carbonate minerals.
3. linking isotopic composition of minerals, including biogenic minerals, to their formation and transformation (natural or experimentally induced). Tracers: ¹³C and ³⁰Si.
4. reconstruction of food-webs. Tracers: ¹³C and ¹⁵N in specific compounds (e.g., lipids or fatty acids).
5. quantification of organism-specific rates of activity by stable isotope probing experiments. Tracers: ¹³C, ¹⁵N, ¹⁸O, D.

Course setup

The course activities will include lectures and practicals (10 meetings) followed by a mid-term exam, and working on a group-project (5 meetings) followed by a written report and poster presentation.

During lectures, we will explain the principles behind the applications (theoretical and empirical) and illustrate them with examples. When appropriate, we will also explain the principles behind the relevant analytical techniques. This part may include a visit to the GEOLAB and IMAU isotope facilities, depending on the interest.

During practicals, you will apply these principles (on paper and computer) to solve practical problems. Most of these problems will be quantitative in character. 

Large part of the course will involve project-based work. You will form a group (3-4 students) and work for 2.5 weeks on a project that best suits your interests. The project topics will overlap with the applications discussed during the lectures (see above). You will receive raw data from stable isotope measurements (as well as other relevant data, when appropriate), and your task will be to process, analyze and interpret it, with the emphasis on quantitative interpretation. You will do this under the guidance of one of the lecturers. At the end of this process, you will write a short report summarizing your approach, results and conclusions. You will also present your findings as a poster in a conference-like setting. Overall, while the group project aims to stimulate deep learning and understanding of (bio)geochemical processes, it is also a great opportunity to further develop your writing and presentation skills in preparation for your Master thesis.

Relation to the curriculum

In this advanced geochemistry course you will learn about applications of stable isotopes in Earth Sciences. These applications are diverse and continuously expanding, covering topics such as element cycling, climate, solar system and Earth evolution, mineral formation and transformations, functioning of food-webs, or physiology of (micro)organisms. In this course you will learn the basic principles behind these applications, and gain practical experience in interpretation of stable isotope data. Stable isotopes are such a basic yet broadly applicable “tool-kit” that learning about them will be beneficial for you if you follow any of the tracks offered by the Master in Earth Sciences program at Utrecht University, including Earth, Life and Climate (ELC), Earth Structure and Dynamics (ESD), Earth Surface and Water (ESW), and Marine Sciences (MS), or if you study atmospheric physics and chemistry at the Institute of Marine and Atmospheric Research (IMAU). It will be particularly useful if you are considering to use stable isotopes during your Master thesis project.