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Chemistry LibreTexts

Identifying the Problem

  • Page ID
    219827
  • This module provides background information about the Columbia Spotted frogs and aquatic snails found at the End Creek Wetland Restoration area.  Surveys data are provided suggesting a decline in frog population and different distributions of aquatic snails in different ponds. 

    Q1. What are some possible water quality parameters that could affect invertebrate and amphibian populations in a fresh water environment?  You may want to research if any information is available on recommended levels of specific ions that may positively or negatively impact these populations.

    This question could be posed to students before any further information is provided.  They could be guided to research the effect that nutrients such as nitrogen and phosphorous, pH, dissolved oxygen, levels of calcium and magnesium and dissolved solids could have on amphibians and invertebrates.  An initial awareness of EPA regulations for some of these parameters could also be developed at this point. A great resource is the EPA Volunteer Stream Monitoring: A Methods Manual (http://water.epa.gov/type/rsl/monitoring/stream_index.cfm). 

    The main research questions that will guide all subsequent modules are:

    1. Is water quality at the End Creek ponds potentially responsible for the decrease observed in spotted frog population?
    2. Are there differences in water chemistry that influence snail family distribution in the ponds at End Creek?

    Like most real scientific questions, these are complex ones! To our knowledge there are no definite answers and there may in fact be a variety of contributing factors that affect these populations. Even if only one or two of the modules will be used in your course, it would probably be useful to start with the Identifying the Problem unit to provide a context for the other sections.

    Identifying Possible Analysis Methods

    It is useful to have students explore the possible analytical methods that might be used to measure cations and anions involved in water quality assessment. 

    If this exercise is used in general chemistry, the experimental procedures (see experimental procedures section) may be made available to students.  If the module is covered toward the end of an analytical chemistry course, students may be asked to go back through each method that was covered in the course and explain whether or not it might work for the analysis of the species in question. 

    An alternative is to ask students to go to the scientific literature and find possible methods for the analysis.  In this format, it is probably best to divide the class into groups and give each group one of the cations or anions to analyze.  After completion of the assignment, each group can report their findings to the rest of the class.  This can lead to a useful discussion of the strengths and weaknesses of the various methods they identify.  This discussion may turn up methods that are not covered or emphasized in the course and lead to the introduction of other analysis methods that are usually not discussed.  

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