Cutting Edge > Geochemistry > Teaching Activities > Relationship between mineral weathering and groundwater composition

Relationship between mineral weathering and groundwater composition

Nancy Hinman
,
University of Montana
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
  • Completeness of the ActivitySheet web page

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This page first made public: May 17, 2005

Summary

By observing changes in rocks exposed to chemical weathering, students are to infer resulting changes to the chemical composition of groundwater. Students are required to justify their inferences through the use of chemical reactions involving common minerals. Students must predict outcome of a chemical weathering experiment.

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Context

Audience

This exercise is used in an undergraduate course in geochemistry or in hydrochemistry.

Skills and concepts that students must have mastered

How the activity is situated in the course

Goals

Content/concepts goals for this activity

Higher order thinking skills goals for this activity

Students are expected to analyze published data in order to develop predictions for how compositions will change in experiments.

Other skills goals for this activity

Description of the activity/assignment

In this pair of activities, students start by using published data to predict what will happen to groundwater composition as a consequence of chemical weathering. The data are provided in a spreadsheet (Hinman_weathering). Students are given the histograms only; both are normalized to 100 %, while one includes silica and the other does not. Students must use resources to predict how groundwater composition will change as a consequence of the observed weathering, and support those predictions using balanced chemical-weathering equations. Afterwards, they conduct a laboratory experiment in which they subject crushed rock to four types of solutions (acid solution, organic-rich solution, rainwater, and alkaline solution). The pH of each solution is measured, and subsequently adjusted after 24 and 48 hours. Solutions are sampled after 14 days. They are analyzed by ICP, and the compositions reported to students for comparison with their predictions.

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Other Materials

Supporting references/URLs

Krauskopf, K.B. and Bird, D.K. 1994. Introduction to Geochemistry, 3rd edition, McGraw-Hill Science/Engineering/Math, 640 p.

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