Isotopes and Tracers

Thomas Meixner, University of Arizona

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This assignment offers students several problems that help them understand the basic of mixing models and their use in understanding the controls on water quality in the environment. The purpose of the assignment is to help students integrate across the various topics in environmental chemistry in the context of flow and transport. Students will hopefully learn how reactive and non-reactive tracers can be used in conjunction to fully understand a chemical system.

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This assignment is the final assignment of the semester for a senior undergrad first year grad student course on the Fundamentals of Water Quality. Students will have covered many of the topics in aqueous geochemistry with a specific emphasis area on isotopes, mixing models and transport.

Skills and concepts that students must have mastered

Student will need to be familiar with- delta notation for stable isotopes, basics of solving a system of equations and the basic concepts of age dating using radiogenic isotopes.

How the activity is situated in the course

This is the final assignment of the term. The assignment is designed to integrate across a number of topics in the course.


Content/concepts goals for this activity

Student will understand how tracers, stable isotopes and radiogenic isotopes can be used to integrate processes in environmental systems. Students will also learn how to test hypotheses about data through the course of the assignment.

Higher order thinking skills goals for this activity

Student will understand how to pull together disparate data sets to understand geochemical and biogeochemical processes.

Other skills goals for this activity

HIgher level thinking about how to link disparate data.

Description and Teaching Materials

This a problem set for the course integrating across nutrients, stable isotopes, radiogenic isotopes and tracers

Problem set (Microsoft Word 36kB Apr30 13)

Spreadsheet for problem 1 (Excel 207kB Apr30 13)

Seasonal patterns in streamwater nutrient and DOC (Acrobat (PDF) 389kB Jun4 13)

Teaching Notes and Tips


Students are assessed on getting questions right quantitatively. In their explanations for why they found the correct results emphasis is placed on student assessing several hypotheses and discarding ones that are not useful and being left with the most useful hypothesis to explain the observed results.

References and Resources