Introduction to urban watershed geochemistry

Vijay M. Vulava, College of Charleston

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The main goal of this multi-part field and lab exercise is to introduce students to practical aspects of soil and water geochemistry. Some of the analyses for this lab are conducted in the field using field analytical instruments and rest of the analyses is conducted in a wet chemistry/geochemistry lab. There are several objectives:
1. Learn how to sample water and soil samples in a safe and effective manner
2. Collect basic aqueous chemical parameters in the field
3. Compare field collected data with that obtained using advanced instruments in the laboratory
4. Determine bulk physical and chemical properties of the soils in the lab
5. Determine trace and major element concentrations of the soils in the laboratory
At the end of this exercise students will gain a better appreciation for how soil and water quality is assessed in multiple ways. They are also introduced to basic "tools-of-the-trade" in the environmental geochemistry and also using Excel to make simple and advanced calculations as well as for plotting data. During preparation of lab reports, they are introduced to basic elements of an effective data-based technical paper.

Key words: urban watershed, soil chemistry, water chemistry, aqueous geochemistry, field analysis, analytical chemistry

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I use variations of this exercises in three courses: (i) Introduction to geochemistry (main focus here is aqueous geochemistry and basic analytical chemistry), (ii) Aqueous geochemistry (focus is on both aqueous and soil geochemistry), (iii) Pollution in the environment (focus is on aqueous and soil geochemistry of contaminated environments). The first course is offered at sophomore to junior level, while the rest are senior-level courses.

Skills and concepts that students must have mastered

1. Students must have completed two-course lab and lecture sequence of introductory chemistry (CHEM 111 and 112).
2. Basic understanding of laboratory chemical safety procedures and philosophy before working in a wet chemistry lab.
3. Some basic understanding of geological and environmental processes in shaping the character of water.

How the activity is situated in the course

This five-part series of lab exercises are designed to be performed after 2-3 weeks in the lab where students become comfortable with the basics of wet chemical analytical principles and in preparing detailed reports of laboratory experiments.


Content/concepts goals for this activity

The main goal of this multipart field and lab exercise is to introduce students to practical aspects of soil and water geochemistry and characterizing water and soil quality in an urban watershed.

Higher order thinking skills goals for this activity

1. Laboratory and field analytical skills.
2. Critical evaluation of chemical data with respect to available data and literature.
3. Synthesis of several different types of data to build a conceptual model contaminant behavior in an urban watershed.

Other skills goals for this activity

1. Operation of field and laboratory analytical instruments
2. Good laboratory practice
3. Preparation of effective laboratory reports patterned after mini-research papers
4. Working in groups cooperatively to share instrumentation and data.

Description and Teaching Materials

There are five PDF files numbered sequentially describing activities to be conducted over a five-week period. Each period is designed for a 3-h lab depending on the availability of instrumentation.

Introduction to Urban Watershed Geochemistry Lab Exercise 1 Student Handout (Acrobat (PDF) 1.3MB Apr15 13)
Introduction to Urban Watershed Geochemistry Lab Exercise 2 Student Handout (Acrobat (PDF) 2.4MB Apr15 13)
Introduction to Urban Watershed Geochemistry Lab Exercise 3 Student Handout (Acrobat (PDF) 661kB Apr15 13)
Introduction to Urban Watershed Geochemistry Lab Exercise 4 Student Handout (Acrobat (PDF) 145kB Apr15 13)
Introduction to Urban Watershed Geochemistry Lab Exercise 5 Student Handout (Acrobat (PDF) 134kB Apr15 13)

Teaching Notes and Tips

These activities can easily be modified to study both pristine and urban watersheds. Analytical parameters can also be altered to accommodate other available analytical techniques or interests of the instructor. Depending on the course and the scope, modules can be added, removed, or modified. For example, in a pollution themed class, monitoring basic indicator pathogens can be used to assess stream water quality and delineate main sources of contamination within the watershed. In a hydrology themed class, water isotopes can be used to delineate sources of water to a stream. I create a series of these exercises built around a major theme each year to add "freshness." For example, we either characterize a different pristine or contaminated site each year. We also involve major stakeholders including community groups, nonprofits, local government, etc. to give relevance to the overall project and give students a sense of ownership.


I use a rubric to evaluate each section of the lab report as well as the laboratory performance and lab journal. As the beginning of the semester, I conduct a laboratory orientation. Topics covered include detailed information on laboratory safety, maintaining a lab journal, good laboratory practices, detailed instructions on preparation of a good laboratory report, and the grading rubric for each completed laboratory.