Stable Isotopes

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The hydrologic cycle (Open University Press)


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» Lecture 13 slides
A pdf of lecture 13 slides in 2X2 format for annotation during class.

» Lecture 14 Slides
A pdf in 4x4 format for printing and annotating during class.

» Lecture 15 Slides
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» Lecture 16 Slides
in 2X2 PDF format for annotation in class

» Intro to Isotopic Calculations
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» Stable Isotopes Review
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Stable Isotopes

So far the emphasis has been on the radioactive isotopes and what they tell us about the timing and nature of processes. We now embark on the topic of stable isotopes and isotope fractionation. We will first learn about how stable (and sometimes unstable) isotope ratios are measured by mass spectrometry. This is important because the isotope geochemist needs to understand the nature of the measurements in order to realize the character and limitations of the data. We then explore the principles, systematics, and mathematics of isotope fractionation. Finally, we delve into two new and promising developments, namely mass-independent fractionation and clumped isotopes.

Lectures 13 and 14: Isotope measurements

Since you need to understand the limits and character of your data in order to use it effectively, we spend the next two lectures discussing isotope ratio measurements. The tool of choice for these measurements is the mass spectrometer, so we concentrate on the mechanics of how these instruments work. This involves a discussion of the underlying principles of mass spectrometry and a broad survey of the various types of mass spectrometers, ranging from "traditional" stable isotope mass spectrometers through ICPMS and AMS systems.  We investigate some of the analytical challenges involved in the various methods. The isotope dilution methodology and mathematics are explored. Then we discuss some basic concepts of data treatment and review error propagation one more time. Finally, we explore how half-lives can be determined using mass spectrometers. 

Lectures 15 and 16: Isotope Fractionation Systematics

Here we learn about the underlying physical principles about isotope fractionation, the basic mathematics and calculations, and some of the generalities associated with using stable isotopes as probes of biogeochemical processes. We finish by exploring mass independent isotope fractionation.

 

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Last updated October 29, 2012
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