A Teaching Exercise To Introduce Stable Isotope Fractionation of Metals into Geochemistry Courses

Abstract

Variations in the isotopic composition of elements have been widely used to study earth’s climate, biosphere, and interior, and more recently to track the fate of contaminants. Within the broad range of elements that exhibit measureable isotopic variations, metal stable isotopes are increasingly applied across the biological, geological, environmental, and chemical sciences. Mass spectrometry and the isotope (geo-) chemistry of metals, often termed non-traditional stable isotopes, are not yet regularly taught in university courses. However, their growing importance in the natural sciences is reflected in the increasing number of research papers published. We present here a novel teaching exercise that can be incorporated into a curriculum where the stable isotope (geo-) chemistry of more traditional stable isotope systems (e.g., C, H, N, O, S) or inorganic mass spectrometry is taught. The exercise first introduces the basics of metal stable isotope fractionation. Next, the students use scientific papers to develop spreadsheets that enable them to program equations, to test isotope fractionation models, and to interpret environmental processes.