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Unit 6.2 - Biogeochemical Examples

Adam Hoffman (University of Dubuque)
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This material was developed and reviewed through the InTeGrate curricular materials development process. This rigorous, structured process includes:

  • team-based development to ensure materials are appropriate across multiple educational settings.
  • multiple iterative reviews and feedback cycles through the course of material development with input to the authoring team from both project editors and an external assessment team.
  • real in-class testing of materials in at least 3 institutions with external review of student assessment data.
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This page first made public: May 15, 2017

Summary

In this week-long unit students will explore Critical Zone function and dynamics as they relate to nutrient cycling in agricultural systems and nutrient pollution into aquatic systems. This unit is generally subdivided into three sections: (1) nutrient pollution (2) agricultural importance and (3) Critical Zone function and dynamics in relation to nutrient cycling. The students will use data sets, interactive activities, primary literature, and videos to allow them to examine the role that the CZ plays and how that role changes with differing land uses. Important present-day topics of food production, clean water, nutrient pollution, and sustainable agriculture are examined using a CZ lens. Students will interact with each other on a variety of scales (individual, small groups, entire class) and using a variety of modes (presentations, written reports, question and answers, and class discussion) in this unit. Additionally, optional activities are provided if lab activities are able to be accommodated. The unit ends with a summative assessment assignment that is based on an innovative call for proposals to combat one of America's most widespread, costly, and challenging environmental problems: nutrient pollution.

Learning Goals

Learning Objectives:

  1. Increase student proficiency in the reading and interpretation of scientific literature.
  2. Increase student understanding of the role the Critical Zone plays in food production and providing clean water.
  3. Explore the cycling characteristics of important biological elements---C, N, and P---through the Critical Zone.

Specific Biogeochemistry Learning Goals:

  1. Introduce students to general geochemical concepts, processes, theory, and specifically the phosphorus and nitrogen cycles.
  2. Students will evaluate the impact the Critical Zone has on clean water.
  3. Students will use data to explain the role the Critical Zone plays in agriculture, eutrophication, and how the two interact (nutrient transport).
  4. Students will explain the differences in land-use on nutrient cycling and CZ functions.

Context for Use

This unit is easily adaptable to a lab, lecture, or online course and is intended for students with a basic geoscience background. The entire unit is designed with two 75 minute periods, which can be easily modified for three 50 minute periods. Minimal equipment is needed for this unit, however the optional soil filtering activity has a larger set of equipment needed.

Description and Teaching Materials

Pre-class Reading

Carpenter, S. R. (2008). Phosphorus control is critical to mitigating eutrophication. Proceedings of the National Academy of Sciences. 105(32), 11039-11040.

Unit 6.2 - Day 1 (75 min total)

Introduction [20 minutes]: During this 75 minute class period the students will explore the relationship between water bodies, nutrient cycling, and the Critical Zone.

  • Concept Mapping
    • Have students make a concept map answering the question "What connections exist between the Critical Zone and the food we eat and the water we use?"
    • The goal of the concept mapping exercise is to get an initial feel for what the students know regarding the connections between the Critical Zone and the food we eat and the water we use. You can use it to guide a discussion, or use it as an assessment tool later on. It is suggested that these grand challenges are discussed after the concept mapping to tie in the final summative project. If the latter is the plan you can can assess the concept map (1 point is given for each correct relationship i.e., concept-concept linkage; 5 points for each valid level of hierarchy; 10 points for each valid and significant cross-link; and 1 point for each example). An example of a scored concept map can be found at the following website, http://archive.wceruw.org/cl1/flag/cat/conmap/conmap7.htm
  • Discuss Pre-class Reading - Carpenter, S. R. (2008). Phosphorus control is critical to mitigating eutrophication. Proceedings of the National Academy of Sciences. 105(32), 11039-11040. http://www.pnas.org/content/105/32/11039.full.pdf. Have the students recap their answers to the reading questions using think-pair-square-share. It is important in the discussion to stress that both N and P are important drivers, yet the systems cannot expect to improve simply with decreasing N inputs. Also this is a good opportunity to tie in the two geochemistry and biogeochemistry units.
  • Unit Background slides to introduce the topic of nutrient pollution Intro to BGC Cycling Examples (PowerPoint 2007 (.pptx) 1.5MB Feb2 17)
  • Nutrient Pollution
    • Have the students jot down three important take-home points from the video. After watching the video hold a class discussion to see what points were identified by the students. Ask the students to explain what a dead zone is, what causes a dead zone, and how can we reduce the number of dead zones occurring around the world.
    • EPA Video on Nutrient Pollution

Agricultural Influences and Impacts [55 minutes]

  • Read and Discuss. This reading focuses on soil as a threatened resource and should challenge the students' view on the role that soil plays. Hopefully with the previous discussions in the preceding units the content will be less extreme than it might first seem. The questions that the students are directed to fill out and share (in think-pair-square-share) should help them focus on what is in the article as well as to extend the thoughts of the article.
  • Best management practices - In Your Backyard. The strength of this activity lies in both integrating case studies as well as showing the important steps that many groups in many areas have taken to decrease nutrient pollution. In addition in this exercise the students will interact in multiple scales, with each other, and in small groups. The list of case studies is fairly extensive and will allow you to choose case studies that hold meaning for the class in terms of geographic significance (e.g. students from a particular area, previous locales that may have been examined in class). This is a good spot to examine best management practices that could be explored in the final summative assessment project, as the proposed CZO should consider scale and services provided by the critical zone.
    • Small group activity followed by large group discussion. Use existing databases to identify local case studies in nutrient pollution reduction efforts. Give each group a different case study (sites listed below have links to pages with 2 page pdf summaries that can be distributed to each group) and have them list the best management practices used and then summarize the case study for the entire class.
  • Journal - What you learned, questions you have, what you're confused about. This is some time for the students to reflect on what they learned in class today. In addition it will help all determine content that has still not quite sunk in yet. It is suggested that areas identified be followed up to start the next class period.
  • Homework: The students will read two articles pertaining to dead zone size, both dealing with historical dead zone size and predictions regarding future dead zone size. The homework then prompts them to find primary data to backup claims in the articles.
  • Optional Lab/Data Analysis Activity (1.5 hours): Students will be introduced to the concept of dead zones and will probe their causes, spatial, and temporal variations, and remedies using hands on activities and NOAA data. This activity need not be done in the lab, but computer access is a must and a large chunk of time should be devoted to it, so a lab activity or homework activity would work best. The activity deals with viewing, modeling, and interpreting the dead zone, which is a result of our mismanagement of nutrients and soil in our watersheds.
    • Dead Zone Activity: Students will be introduced to the concept of dead zones and will probe their causes, spatial and temporal variations, and remedies using hands on activities and NOAA data
  • For more information see the following:

Unit 6.2 - Day 2 (75 min total)

Introduction: During this 75 minute class period the students will explore the cycling of carbon, nitrogen, and phosphorus and will examine how Critical Zone characteristics influence cycling. The lecture period today is broken into two parts, cycling of nutrients and critical zone function and dynamics.

Activity to assess last class period's learning as well as setting the stage for today's class.

  • Questions the students need to answer using knowledge gained from last class period and the homework articles they read. Suggest using individual think, pair, share to answer these questions.
  • Answers to the same questions from a researcher at the University of Michigan who specializes in nutrient pollution as it relates to the dead zone.

Cycling of Nitrogen, Carbon & Phosphorous (N, C, P) [40 min]

  • Activity - in groups create global cycling schematic for P and N (5 minutes) based on the article below. Then have the class work together to create a global schematic for P and N cycling on the board. It is suggested that the professor work as the facilitator during this time. Make sure to point out the natural and anthropogenic flux differences between N and P. In addition point out that the atmosphere is very important for N cycling, but much less important (not at all in many locals) in P cycling. Air-borne sediment can on occasion play a role in atmospheric P transport.
  • Follow-up or alternative activity - Powerpoint presentation showing literature examples of C, N, and P global cycles to compare with the student's creations. In addition there are soil P and N cycles that will help tie together modules 6.2.1 and 6.2.2.
  • As a class watch, the following TED Talk. Then group the students up and have them brainstorm ideas why this new technology of using mycorrhizae has not been readily adopted by the world. Then have each group read and discuss a response to the talk. This video, like the others suggested in this unit could also be assigned as homework rather than watching it in class. The benefit from viewing it in class is that it ensures all the students are able to contribute to group discussions. Hearing two sides to an argument is important for students. In addition the fact that the response to the TED Talk is from a fertilizer group should be noted. The ideas of science communication and the important considerations are considered further in the Continuing the Science Communication Discussion file.
  • Class discussion of the change in agricultural soil carbon over 15 years and carbon sequestration (5 minutes). The changes of carbon storage as a result of land use and agricultural practices are readily apparent. However the land use changes and agricultural practices are likely not as apparent so have the students brainstorm what might have driven the noted changes.
  • Review primary literature of N and P cycling (5 minutes) based on the article below. This article compliments the preceding carbon storage activity as it delves into the specifics of land use and agricultural practices. In addition, this article is over 15 years old and allows the students the opportunity to examine how far we've come (or not) in terms of N and P pollution and Critical Zone functions.
  • Homework: Each of the homework options listed below allow the students to interact with the biogeochemical issues relating to water quality. The first option is a bit more global in scale, while the second option gives the student more flexibility and freedom in choosing the processes and areas they wish to study.
    • Option A: Listen to the following podcast and write a one-page summary
    • Option B: Students will produce a case study showing how specific biogeochemical processes have influenced the amount and quality of water and soil in a specific region or area.
      • Students should also discuss how food production and water usage affects the specific region or area.

Critical zone functions and dynamics [20 min]

  • Quick Read: Have the students examine these figures and determine how deep saprolite P limitation is different than aquatic P limitation. The students will also explore the variation in weathering rates of apatite. This activity will stress to the students the differences in P limitation and cycling in an environment not similar to the ones previously discussed.
    • Dissolution of Apatite (Luquillo Mountains, Puerto Rico CZO):Buss H.L., Mathur R., White A.F., and Brantley S.L. (2010): phosphorus cycling in deep saprolite, Luquillo Mountains, Puerto Rico. Chemical Geology. DOI: 10.1016/j.chemgeo.2009.08.001
  • Water's influence on weathering in relation to elements. This is a nice visual that can be played for the class and it quite clearly (admittedly on a very basic level) shows how weathering affects different elements. It should encourage the students to think about differences in water and soil characteristics in relation to weathering characteristics and parent material influences.
  • Journal - What you learned, questions you have, what you're confused about.
  • Activity 6.3 - Homework Activity (Summative Unit Assessment): Nutrient Challenge. Depending on class size, this activity can be assigned individually or to groups of students. One particular strength of this activity is its real-world basis and that it necessitates building on both units of this module. This activity, based on a real world challenge grant, prompts students to apply their knowledge learned in the geochemistry and biogeochemistry unit to devise a transformative strategy for reducing excess nutrients in the waterways. This activity should serve as an effective way to tie together the unit by necessitating the utilization of the biogeochemical and geochemical processes that take place in the Critical Zone.

Teaching Notes and Tips

The unit was developed so that an array of activities was provided for the instructor to select from based on their expertise and the interest of the student. This includes optional homework, labs, and readings to be used to supplement the topics as the instructor sees fit. There too is flexibility built into the summative unit assessment assignment (Nutrient Challenge), as it it can be assigned individually or to groups of students. This is a strong activity that has a real-world basis modeled after an actual solicitation, requires information from both biogeochemistry units, and it necessitates "out of the box" thinking.

All students are expected to read all articles, however like the preceding unit, 6.1, it is recommended that students be assigned into small groups to begin each discussion prior to holding a large class discussion. Most readings are to be done outside of class, but the Save Our Soils reading is short and many have found it useful to use that reading as an in-class reading.

Assessment

Formative Assessment Options are built into the above activities and include:

  1. Concept maps
  2. Responses to primary literature and video clips
  3. Homework activities (written summaries)
  4. End of class journal responses

Summative Unit Assessment Options:

1) Nutrient Challenge. Depending on class size, this activity can be assigned individually or to groups of students. One particular strength of this activity is its real-world basis and that it necessitates building on both units of this module. This activity, based on a real world challenge grant, prompts students to apply their knowledge learned in the geochemistry and biogeochemistry unit to devise a transformative strategy for reducing excess nutrients in the waterways. This activity should serve as an effective way to tie together the unit by necessitating the utilization of the biogeochemical and geochemical processes that take place in the Critical Zone.

2) Pre and post concept maps. Concept maps can be used for assessment, both formative or summative. For example, one can assess concept maps in the following manner: 1 point is given for each correct relationship i.e., concept-concept linkage; 5 points for each valid level of hierarchy; 10 points for each valid and significant cross-link; and 1 point for each example. An example of a scored concept map can be found at the following website and an example of how concepts maps can be used for assessment in the geosciences can be found here.

References and Resources

  • CZO data website: http://criticalzone.org/national/data/access-czo-data-1national/
  • Euro CZO: http://www.soiltrec.eu/
  • Alexander, R.B., R.A. Smith, G.E. Schwarz, E.W. Boyer, J.V. Nolan, and J.W. Brakebill. 2008. Differences in phosphorus and nitrogen delivery to the Gulf of Mexico from the Missississippi River Basin. Environ. Sci. Technol. 42(3):822-830 doi:10.1021/es0716103
  • Banwart. 2011. Save our soils. Nature. 474: 151-152.
  • Buss H.L., Mathur R., White A.F., and Brantley S.L. 2010. Phosphorus cycling in deep saprolite, Luquillo Mountains, Puerto Rico. Chemical Geology. DOI: 10.1016/j.chemgeo.2009.08.001
  • Filippelli, G. M. 2002. The global phosphorus cycle. Reviews in Mineralogy and Geochemistry 48: 391–425.
  • Carpenter, S.R., N.R. Caraco, D.L. Corell, R.W. Howarth, A.N. Sharpley, and V.H. Smith. 1998. Nonpoint source pollution of surface waters with phosphorus and nitrogen. Ecological Applications. 8(3):559-568.
  • Zip file with data for Dead Zone mapping activity. Data for Modeling Dead Zone Activity (Zip Archive 4.2MB Jul24 16)

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These materials are part of a collection of classroom-tested modules and courses developed by InTeGrate. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »