Environmental Water Quality Monitoring in
Regional Rivers and Streams
Jennifer Byrd
North Central High School
Spokane, WA
Jessica Smith
Lewis and Clark State College
Lewiston, Idaho
Washington State University Mentors
Professor Bernard Van Wie
Chemical Engineering
Sarah Haarsma
Graduate Research Assistant
Fuchida Hajime
Graduate Research Assistant
Bingwen Liu
Graduate Research Assistant
Daniel Rieck
Graduate Research Assistant
July, 2006
The project herein was supported by the National Science Foundation Grant No. EEC-
0338868: Dr. Richard L. Zollars, Principal Investigator and Dr. Donald C. Orlich, co-PI.
The module was developed by the authors and does not necessarily represent an official
endorsement by the National Science Foundation.
Project Summary
Overview of Project
This module uses ion-selective electrodes to increase student interest in engineering and its applications. These lessons provide middle school and high school students the opportunity to test and analyze water quality for regional rivers and streams. Students will investigate concentrations of ions in water samples (e.g, H+, Ca2+, K+, Na+, Mg2+, SO42-). Using standards of known concentrations of ions students can find regression lines that will allow them to identify the concentration of ions in unknown samples. Student groups will also create RAFT style assignment on the characteristics of a particular ion and the impacts it has on living things and including data from the labs showing ion concentration levels.
Intended Audience
The intended audience for this module will be high school students. With some modifications this module could also be used for middle school students. The background required for this module is experience of general science at ninth or tenth grade levels.
Estimated Duration
This module is intended to last between one and three weeks. It will also be modified in order to give at-risk students visiting a local college an abbreviated experience with the materials and concepts in one hour sessions. For this module we will pre-assemble the electrodes and circuit boards in order to fit the module within the time constraints of a district mandated curriculum. Given more time the students may benefit from the opportunity to be involved in the production of the electrodes and circuit boards.
The project is set in three stages. The first part is a unit on pH which serves as an introduction to the ion selective electrode technology as well as the idea of ion concentration. The second part applies the ion selective electrode technology to water quality in local rivers and will include a jigsaw activity to begin and a RAFT style concluding piece. The third piece of the module is the future development which potentially could include studying phosphates with the ion selective electrodes and introducing the concepts of point source and non-point source pollution.
Introduction
This module is intended to engage students in hands on research endeavors surrounding water quality issues and corresponding societal impact on regional rivers to promote enthusiasm and depth of content in high school science learning. As an introduction to ions in solution and use of ion selective electrodes (ISE) our module begins with an introduction to pH, which most ninth and tenth grade students have most likely heard of. This introduction is the module created in 2005 by Steven Kirking from Clarkston High School in Clarkston, Washington, and Eric Nordquist from Colton Middle School in Colton, Washington. This module has been included in Appendix A.
Our module will build on the pH experience and give students the opportunity to take regional river and stream samples and measure the concentrations of dissolved ions. The dissolved ions to be tested will be determined by the available technology for each ion in use with ion selective electrodes and detectable levels of ions in the samples to be tested. As the unit progresses students will be involved in research and presentations which address the characteristics and implications of ions found in the samples. Along with this information there is room for future discussion of particular water quality issues, responsibility to the environment, and point source and non-point source pollution.
The Washington State Department of Ecology currently divides water pollution sources in to two groups. Non-point source pollution, the first group, is the result of runoff. Possible sources include, “…agriculture, forestry, urban and rural runoff, recreation, hydro modification, and loss of aquatic ecosystems.” [3] The second group are the point source polluters which are responsible for discharge of pollutants directly in to the water. The Department of Ecology identifies, “…Types of nonpoint pollution [to] include fecal coliform bacteria, elevated water temperature, pesticides, sediments, and nutrients” [3]. Thus, along the Spokane River many of these Point Source and Non-Point source polluters exist. We hope through this module to introduce students to issues of water quality in their local rivers and for them to take into account the human actions and choices that impact the quality of our water.
Rationale for Module
The Washington State University and National Science Foundation Institute for Science and Mathematics Education through Engineering Experiences gives teachers six weeks of research and coursework centered on chemical engineering and its applications. From this experience the teachers develop a module to take back to their classrooms to share with their students. The modules will be integrated into the science classroom while also including information on the engineering of the technology and its applications.
The technology in this module involves the use of relatively simple and inexpensive electrodes to identify the concentrations of dissolved ions in water. For the classroom this works well as students can use the technology in the classroom or out in the field where often times the equipment to run the same investigations are unavailable due to cost or size. With these electrodes the students can be involved in actual research in the health of the river and make connections to the articles often seen in the papers on poor water quality.
Science
The basic science premise in this module is the dissociation of ions in water. The most common application given to students is pH. This module applies this idea to other ions which can expand the implications in chemistry and bonding, but also moves it to the impacts of dissolved ions on living things, a biological application.
Engineering
For the engineering here one can discuss the engineering taking place to create a better and more economical method of determining the concentration of dissolved ions in a sample. Additionally, there are many ions not yet measurable using the current electrode activity that we may want to explore. Finally, these electrodes are being developed for use in the medical field and may eventually have applications within the human body.
Goals
Module Goals and Expectations
By the end of this module the student will be able to:
-Construct a model of the dissociation of ions in water. (Application)
-Demonstrate and explain how an ion selective electrode is used. (Application)
-Define an ion and its characteristics. (Knowledge)
-Manipulate a spreadsheet in order to construct a trend line and extrapolate data.
(Application)
-Describe the impacts of ions dissolved in water on plant and animal life.
(Understanding)
-Draw conclusions about the quality of the river water in relation to the
concentrations of particular dissolved ions. (Analyze)
-Students will compose a presentation to share their information and conclusions
with an audience. (Synthesize)
State Science Goals and Learning Expectations
1.1.1-Understand the atomic nature of matter, how it relates to physical and chemical
properties and serves as the basis for the structure and use of the periodic table.
1.2.3-Understand the structure of atoms, how atoms bond to form molecules, and that
molecules form solutions.
2.1.3-Describe a reason for a given conclusion using evidence from an investigation.
2.1.4-Analyze how physical,conceptual, and mathematical models represent and are used
to investigate objects, events, systems, and processes.
3.1.1-Analyze local, regional, national, or global problems or challenges in which
scientific design can be or has been used to design a solution.
Equipment
Ion Selective Electrodes
This project works on the principles of ion selective electrodes. “Ion-Selective Electrodes (ISEs) are part of a group of relatively simple and inexpensive analytical tools which are commonly referred to as Sensors. The pH electrode is the most well known and simplest member of this group and can be used to illustrate the basic principles of ISEs.” [1] Each ion requires a unique membrane which includes a molecule which selectively moves the desired ion across the membrane and into contact with the copper lead.
For this module we will be using four different electrodes. The first will be the pH electrode which will be used as an introduction to the use of ion selective electrodes and will be initially used to measure the acidity of common beverages and later to measure the pH of the river water samples. The other membranes will be used to measure the concentration of several of the following dissolved ions; Calcium (Ca2+), Potassium (K+), Sodium (Na+), Magnesium (Mg2+), Chloride (Cl-), and Sulfate (SO42-). Eventually the addition of ion selective electrodes that could be used to detect the levels of Phosphates, Ammonium, and some of the hard metals would be great as an extension to this lab and particularly address the affects of mining and dumping of sewage into our rivers.
Reference Electrodes
All of the specific electrodes can be used in conjunction with the same reference electrode which contains saturated NaNO3.
Circuit Boards
The circuit boards are used to connect all of the components of the system: power supply, multimeter, reference electrode, and ion selective electrode. Directions for creating the boards are included in Appendix F.
Prerequisite Student Knowledge
· Beginning knowledge of how an ISE works, including the concept of ionization
· Familiarity with the use of a digital multimeter
· Basic knowledge of ion concentrations
· Data collection skills
· Key-boarding skills on a computer
· Basic graphing skills
· Basic understanding of logs and exponents
· Ability to use the ion-selective electrode testing equipment
· Ability to use Excel and Chart Wizard
· Basic knowledge of and ability to extrapolate and interpolate
Activities
Pre-Module / Introduction to ion dissociation (Class Curriculum Materials)Pre-Module / pH Module and Introduction to Ion Selective Electrodes (Appendix A)
Introduction / Current News Articles and Pictures of Pollution in the Local Rivers (Appendix C)
Activity One / Jigsaw: Research on Elements and Ions
Lab One / Standardization of the Ion Selective Electrode
Lab Two / Determination of Best Fit (Regression) Line
Lab Three / Determination of Ion Concentration in River Water Samples
Final Project / Individual RAFT Assignment, Peer Graded With Rubric [4]
Jigsaw: Research on Elements and Ions
The students will do research on the impacts of a particular ion on living things and looking for information on toxicity. Divide the students into groups of three. Each person in the group will research one of the ions. A table of internet resources is included in Figure 1. After completing the Ion Research Worksheet (Appendix E) on their assigned ion, the students will gather in groups of with other “experts” on their ion. In the “expert” groups the students will share their findings, determine the most important information, and discuss what they will share with other people in their original groups. Finally, the students will meet back in their original groups and present to each other the information they found on their assigned ion. As each student presents each member of the group should complete the Ion Reference Sheet (Appendix E) which will serve as a resource for the final project.
Standardization of the Ion Selective Electrode
(Lab Format Modified From: Kirking, S, & Nordquist, E (2005))
Purpose
For students to create a graph of ion concentration in standard solutions, so the regression line can be determined for the particular ion selective electrode to be used later in samples.
Safety
1. Students will be required to wear safety goggles, latex gloves and lab aprons at all times.
2. All solutions must be disposed of in appropriate containers supplied by instructor.
3. Absolutely NO food or beverage in the lab at any time.
4. Lab protocol, etiquette, and courtesy will be observed whenever in lab.
Prerequisite Skills/Knowledge
· Beginning knowledge of how an ISE works, including the concept of ionization.
· Familiarity with the use of a digital multimeter.
· Basic knowledge of ion concentrations
· Data collection skills.
Instructional Strategies
Students will work in groups of three. One student will put the electrodes into the various solutions and rinse the electrodes between tests. Another student will be responsible to exchange the containers of standard solutions and make sure that all the electrical contacts stay connected. The third student will be the recorder. Rotation of responsibilities is a good idea.
This particular lab will be convergent in style. There is a specific product which needs to be arrived at, with specific results. The objectives of subsequent labs will take this data and use it more divergently.
Materials/Equipment
1. Ion selective electrodes (for this activity we will be using either Calcium (Ca2+), Potassium (K+), or Sodium (Na+) electrodes, one per group).
2. Reference electrodes (one per group).
3. Electrical digital multimeter able to read milli-volts (one per group).
4. Power source that will provide 3 volts (2 AA barriers, 2 AAA batteries, or electronic power source).
5. Battery holders (one per group).
6. Circuit board specific to ion selective electrode testing (one per group).
7. Solutions of known ion concentrations specific to the electrode being tested. (Solutions of 1.0x 10-1M, 1.0x 10-2M, 1.0x 10-3M, 1.0x 10-4M, and 1.0x 10-5M.
8. Small Petri dishes for holding pH buffers (three per group).
9. Squeeze bottle filled with de-ionized water for rinsing electrodes between tests (one per group).
10. 250 ml beaker to catch water when rinsing electrodes.
Procedures
1. Connect the digital multimeter to the circuit board as per Diagram #2. (An additional technique to ensure proper installation of wiring would be to color code the red connections with red marker and the black connections with black marker. Warning: connecting wires to the wrong sides (i.e.; reversing polarity) will damage the circuits.)