Teacher’s Guide

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In this series of investigations, the students explore the reasons why two farmers experience a major failure of their radish crops. Their neighbor’s radish crop is minimally affected. All three farmers draw irrigation water from the same river. Upstream of these farms a, salt storage facility and landfill were recently built. Downstream is a power plant.

Students represent the staff of the county agricultural agency. They are charged with determining the cause(s) of the radish crop failures. Successful crop production is dependent upon many environmental factors. The students perform a bioassay by growing radishes using samples of water taken from different locations along the irrigation river and its tributaries. Radish seeds are used because they germinate within several days. Percent germination serves as an indicator of water quality. Students will use the internet component of this activity to study the natural history of the area, as well as landfills, salt storage facilities and power plants. Using either CBL/LabPro technology or conventional technology, the conductivity, pH, and temperature of additional water samples taken from the bioassay collection sites are made. The students report their findings and recommendations to the Aire County Radish Growers' Association.

This series of investigations may be used as a stand-alone activity or as a vehicle to prepare students for an actual environmental study or to assess student learning upon completion of such a study. You may customize any part of this activity. To do so, highlight the section of web page you wish to modify, copy and paste it into a word-processing document, customize and use.

If students do not have prior knowledge and training in CBL/LabPro technology, train them or use alternative techniques (pH paper, thermometers, and conductivity tester).

Procedure:

Duplicate materials

Prepare hardcopies of student investigation pages for each student.

Prepare water samples (for class)

1. Duplicate and tape sample number to each of 15 containers (clear tape covering entire label prolongs life of label). Film canisters are ideal and can be easily obtained at no cost from photography stores or wherever film is processed.

All 15 collection sites should be included in this activity. If you have fewer than 15 students, have volunteers be responsible for anlayzing the extra samples. Should you wish to have each student analyze his/her own water sample, prepare additional canisters by making duplicates of water sample sites. For a large class, several students could be assigned to a water sample.

2. If the salt storage facility is the cause of crop failure, then make water samples nearest this source of higher salinity than those further away (see teacher map). A range of 3% (3g sodium chloride per 100 ml water) to 0% works well. See below for suggested salt concentrations to place in the different water sample canisters.

Teacher suggestion: In a similar way, prepare a range of dilutions if you desire the landfill to be the culprit. ( Safety goggles should be worn by all students when using hydrochloric acid) Appropriate to the location from which water sample was taken, reduce the pH by the addition of hydrochloric acid. This is based on the assumption that acids are leaching out of the landfill. Determine what pH is necessary to prohibit radish seed germination (we found only pH 1 prohibited radish seed germination).

3. Fill each canister with an equal amount of solution (about 8 -10 ml).

Bioassay

Students are to place a paper towel in the gallon-size plastic bag and pour entire water sample into the bag. The water diffuses most rapidly if the bag is laid flat on the table. Once the toweling is wet, the seeds are placed in a horizontal row about 2 inches from the bottom of the bag. As the bag is sealed, excess air should be expelled. If the students gently press the on the sealed bag against the seeds, the seeds will adhere better to the wet toweling and remain there unless roughly handled. Bags can be taped, seeds showing, to the wall or bulletin board. The number of seeds that germinated is to be recorded.
Teacher suggestion: measurements of shoot and root length may also prove informative. Bioassaying with invertebrates, such as daphnia or lumbriculus,is also a possibility.

Bioassay Bags	Seed Arrangement

Design Pool

While the students are awaiting bioassay results, this is an ideal time to have the students practice using temperature, conductivity and pH probes to study the dispersal of hot water or chemicals in the Design Data Pool. Please see student pages for pictures of the design pool.

Photos of Pool

The dispersal of hot water or an acid (500 ml vinegar) can be modeled by adding them in front of the circulating pump. Have the students place probes along both sides of the channel flow (near central "garbage can" and outside wall of the pool) when the hot water (to which red food coloring has been added for greater visiblity) or acid is added. Also try placing the probes at different depths when observing the dispersal of the hot water. Have students share and discuss data and its implications in trying to determine reason for radish crop losses.

Internet

To assist students locate relevant background information, web sites about radishes, landfills, salt storage facilities, and power plants have been included. Student explorations are not limited to theses sites.

Teacher Watershed Map

This map differs from the students' map by including the location of the 15 water collection sites.

Canister Labels

Teacher Data Table

The table will assist you in determining what concentration solution should be placed in each sample canister. Prepare a handout of this table for each student BUT DO NOT GIVE THIS TO STUDENTS UNTIL AFTER all data has been collected - distribution prior to this will diminish open-endedness of activity.

Aire County Agricultural Department

Reuter River Study

Suggested Activities:

1. Field trip to your local water facility.

2. Guest speakers: geologist, ecologist, scientist from the agriculutral extension office.

3. Have students visit a local stream to collect and analyze water samples.

4. Have students visit a local stream and a pond. Collect, analyze, and compare data from both sources. Consider the organisms that inhabit both aquatic environments. What adaptations have they made to survive in their environments?

5. Have students design and implement their own water quality activity.

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