Interdisciplinary Investigation (IDI)-LAB

Research-based Interdisciplinary

Science Education

Investigating Eutrophication in our Campus Wetlands Using Ion Chromatography

Introduction

In the summer of 2014, residents of Ohio’s fourth largest city, Toledo, were urgently warned not to drink their tap water, even if they boiled it. Chemists had found high levels of a potent toxin called microcystin in the water supply. Restaurants closed, the governor declared a state of emergency, and residents quickly bought out all available bottled water.

The source of the toxin was an algal bloom so dense it was visible from space. The bloom was fueled by fertilizers and run-off from industrial sources near the lake. The run-off contained sources of nitrogen and phosphorus; these two nutrients are frequently limiting in aquatic systems, meaning that their scarcity typically prevents substantial growth of plants and algae.

The city of Toledo, however, experienced an acute eutrophication event. Eutrophication occurs when an ecosystem is enriched with nutrients like phosphorus or nitrogen. These added nutrients trigger a predictable chain of events. They act as fertilizer for the algae, triggering a bloom. Eventually, the algae start to die off, and sink to the bottom. Bacteria then start to decompose the algae, quickly using up most of the oxygen in the system. Fish and other aquatic animals then begin to die off. Sustained eutrophication can create so-called “dead zones”, or large areas where oxygen levels are too low to support most aquatic life.

Because of the potentially devastating ecological and health impacts of an eutrophication event, scientists often monitor both the nitrogen and phosphorus concentrations in aquatic systems.

In this lab, you and your team will have the opportunity to develop your own research question and collect some data on nutrient enrichment in our local wetland. Ion Chromatography (IC) will be used as the tool to quantify these nutrients, with a specific focus on quantifying nitrates (NO3-) and phosphates (PO43-). For a review of Ion Chromatography, please see the handout provided.

Overview of the Investigation

In this investigation, you will work with a team to design a research question that is focused on eutrophication events in our campus wetlands, collect samples, analyze your results and draw conclusions. To accomplish this, we will progress through the following parts of this project:

Part 1: Eutrophication, Review Ion Chromatography and Wetland Tour(Day 1 in class)

Part 2: Design Research Question and Collect Samples from Campus Wetlands (Days2, 3in class)

Part 3: Seminar (prepare outside class between Days 24, discussion in class on Day 4)

Part 4: Representing Results & IDI Challenge(Day 4in class)

Part 5: Post-lab Assignment(outside class)

Outcomes

  • Recognize how scientists engage in research practices including communicating through dialogue and writing
  • Identify a variety of water quality issues on the global scale and recognize how ion chromatography can contribute to water monitoring efforts
  • Explain how ion chromatography can be used to separate and quantify ions in aqueous solutions
  • Review and critique science writing and respond to your peers in a productive manner
  • Design a research question that is feasible for the amount of time and tools you have available to investigate your question
  • Collect and process water samples in a field setting such that the samples can be evaluated using ion chromatography
  • Use unit conversion calculations to assess and compare laboratory results to EPA regulations
  • Quantify, analyze and represent research results using Excel

Part 2: Wet-labSolution Preparation and Analysis using the IC (prelab due Day 3)

Pre-lab: Due Day 3. Handwrite the procedure and any tables into your lab notebook. Answer the following pre-lab questions in your lab notebook.

1.Water nitrate (NO3-) levels exceeding 3.00 mg/L are considered contaminated.

  1. Convert 3.00 mg/L to molarity (M)
  2. Convert 3.00 mg/L to millimolarity (mM)
  3. Convert 3.00 mg/L to ppm
  4. Convert 3.00 mg/L to ppb

2.What is eutrophication? Describe what causes it?

3.Briefly describe ion chromatography (IC). What can IC measure and how does it work?

4.Practice making and using acalibration curve.

[NO3-]
(ppm) / Peak Area (S/cm)
1.0 / 0.0401
5.0 / 0.2511
10.0 / 0.5022
20.0 / 1.0456
40.0 / 2.0125
  1. Use a spreadsheet program to plot a calibration curve using the followingpractice data. The x-axis is ppmand y-axis is peak area.
  1. Include a point on your graph showing the EPA limit for ground water (3.00 ppm).
  1. Include on your graph an unknown sample that gives a peak area of 0.8257S/cm.

Sample Collection Guidelines

On Day 1 you will take a tour of the Wetlands. With your lab group, you will determine what question you want to answer and where to collect your samples. Use these guidelines to design your own procedure.

  1. Rinse your plastic collection bottle as follows three times.
  2. Fill ~1/4 full with DI water
  3. Cap and shake
  4. Pour the rinse water out
  1. Fill your collection bottle to the top with distilled water.
  1. When you have arrived at the wetlands, pour out your distilled water.
  1. At your chosen water sample collection site collect your wetland water sample in the plastic bottle provided.
  1. If collecting flowing water: Be sure to fill the bottle with the opening facing away from the flow of water if collecting in a stream or river. Hold the opening of the bottle below the surface. Do not collect surface water.
  2. If collecting in standing water: Push the opening of the bottle well below the surface when filling. Do not collect surface water.
  3. To make sure that all the distilled water has been completely removed from your bottle, rinse the bottle with your sample source water three times. Make sure to follow the same procedure each time you rinse/fill the bottle (holding the bottle below the surface, facing away from the water flow).
  1. Bring your sample back to the lab and prepare it for measurement by ion chromatography.
  2. Filter your wetland water sample through as instructed. We will go over this in lab.

Part 3: Seminar Preparation (outside class between Days 2 and 4)

Read the articles:

1. Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions, Proceedings of the National Academy of Science (2013).

2. Toxic algae creating deep trouble on West Coast, Seattle Times (2015)

3. This summer’s West Coast algal bloom was unusual. What would usual look like?, NOAA(2015)

To prepare for the seminar, write a brief summary of each article, and write three questions that come up for you during the reading. Bring the summary and questions with you to class and be prepared to participate in an in-class seminar. You will be asked to submit your summary and questions to your instructor after the seminar.

Part 4:Representing your Results & IDI Challenge (Day 4in class discussion, include in postlab)

1. Once you have your results (chromatograms), identify the peaks of interest. Are there any peaks in the chromatogram that you were not expecting? If so, discuss what these might be?

2. Explore the concentration data that was provided for your samples. Be sure that you are very clear on how these concentrations were determined using standards and a calibration curve. Do you notice anything interesting or out of the ordinary? Are the results in the range that you expected?

3. Use Word and Excel to design a table and a graph to illustrate your results. Be sure to think about what kind of table would work well for your particular set of results. You may want to spend some time thinking about calculations that would be useful for making your points (mean, standard deviation, etc.). Show your graph to your instructor for feedback.

Part 5:Post-lab(complete after Day 4)

1. In your lab notebook, clearly provide all methods and results (graphs and tables). Also in your lab notebook, include a statement of any problems/errors encountered, and a separate statement of what you learned from this lab.

2. Prepare an electronic report (Word doc) including the sections shown below. These sections represent the skeleton of a formal report or journal article. This week we will practice writing these sections, but will keep it brief. No more than three pages total for your entire report.

3. After writing your report, respond to the following question:

Knowing what you know now, what would you change about your research question? Rewrite your question to reflect your new thinking.

Title

Write a descriptive title that captures the essence of your investigation

Introduction

Write one paragraph that provides an introduction to eutrophication and how nitrates and phosphates are involved. Include at least one scholarly citation. The last sentence of your introduction should introduce your project. You may want to begin that last sentence with something like; In this study…. You should end this section with a statement of your research question.

Methods

Clearly describe your procedure in paragraph format.This should include descriptions of the sites you selected including any photos that you captured. It also includes sampling procedure, sample preparation procedure, and a statement about using the IC to quantify ion concentrations. Be sure to number photos or diagrams and provide a caption for each figure. This section may be more than one paragraph, but no more than three.

Results

Provide your results (tables and graphs) produced in Part 4 of this investigation. Be sure that your figures are numbered and have captions. You should also include a paragraph describing the results, referencing your figures.

Discussion

Write one paragraph discussing what your results indicate and any implications associated with your findings.

References

Provide the citation for the reference(s) you used in your introduction.