Evaluating the Health of an Urban Wetland Using Electrical Resistivity

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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

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- Scientific Accuracy
- Alignment of Learning Goals, Activities, and Assessments
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This material was developed and reviewed through the IGUaNA curricular materials development process. This structured process includes:
- Iterative review and feedback cycles throughout the course of material development with input to the author(s) from the project team;
- Pilot testing of materials in courses at multiple institutions; and
- Pre-publication review to ensure the materials meet the standards in the IGUaNA module rubric.

Initial Publication Date: April 16, 2021 | Reviewed: August 4, 2022 (see revision history: 2 events)

Summary

This module introduces students to the fundamental principles and uses of electrical resistivity, with a focus on an environmental application. Students explore the characteristics and environmental setting of Harrier Meadow, a salt marsh just outside of New York City. They investigate the relationship between electrical resistivity and physical properties of the soil in the marsh. Students also discover how variations in survey configuration parameters control investigation depth (how far into the ground the signals sense) and spatial resolution (what size objects can be detected). Finally, students learn about and then perform geophysical inversion, which is the process of estimating the geophysical properties of the subsurface from geophysical observations. In the final unit of the module, students evaluate the extent to which the geophysical dataset and direct physical measurements support the hypothesis, introduced in Unit 1, accounting for the distribution of pickleweed in Harrier Meadow.

Optional: Students can collect and analyze their own seismic refraction data, using instruments available through the EarthScope Primary Instrument Center (instructions for making an educational use request are on the EarthScope Geophysics Field Education page).

Strengths of the Module

Use of real data: Authentic datasets are used throughout the module, beginning with Unit 1. This allows students to grapple with the challenges of real data sets, where there is an inherent element of ambiguity. It also shows students how geophysics is used one real-world setting.

Connects students to the world around them: This module emphasizes how electrical resistivity is used as a proxy for measuring salinity in a wetland just outside of New York City, and how the presence of an indicator species is used as a proxy for ecosystem health. Comparing these data illustrates how cities impact the environments around them.

Flexibility: This module can be used as individual units or as a complete module. It is also possible to use Units 1, 2, and 5 without the more mathematically intensive Units 3 and 4. This approach significantly decreases the time it takes to complete the module while still highlighting the application of geophysical methods to an urban environmental question. Unit exercises can be used as homework or in-class/lab assignments. Exercises can be completed individually or in small groups.