In the discussion thread: Fate of Japan and the Whole World Depends on No. 4 Reactor [View all]
Response to Peace Patriot (Reply #65)
Fri Apr 20, 2012, 01:37 PM
snooper2 (18,889 posts)
103. you ever put a drop of purple dye
in an olympic size pool?
Did teachers ever broach these type of topics in science class in the 60's and 70's?
(Fair Use- Government Website)
• define how water can be traced as it moves underground,
• define parts-per-million and parts-per-billion,
• identify two dyes that are commonly used in
hydrologic dye traces.
• Black light
• Eye dropper
• Sample bottles of rhodamine, fluorescein, and optical brightener
1. Ask the students to imagine that they have a delicate cave under their land. The cave has
several large pools, and water drips from the ceiling in many places. A rare species of
blind cavefish lives in several pools in the cave. Two streams run through their property
and disappear into the ground in the woods behind their house. The water in one stream
is very cloudy and may be polluted. Do the students think the water from the streams is
entering the cave? How can they find out?
2. Discuss hydrologic dye tracing. Show the students examples of rhodamine and
fluorescein, two types of dyes that are often used in dye traces. Stress that the dye is nontoxic
and is used in very dilute concentrations.
3. The dye is fluorescent, and often an “optical brightener” (show students the sample
bottle) is added to the dye to increase its fluorescence. Optical brightener is found in
laundry detergents. It is the ingredient that makes your whites appear whiter and your
brights appear brighter, by reflecting sunlight. Turn off the classroom lights and pull
down the shades. Turn on the black light and walk around the room holding the
brightener near students’ clothes, demonstrating to each student that the optical
brightener fluoresces. DO NOT SHINE THE BLACKLIGHT IN ANYONE’S EYES!
4. The students are going to use fluorescent dye to trace the streams into the cave. Have
them determine how they will tell which stream is providing water to the different pools
and drip sites in the cave. (They can put fluorescein in one stream and rhodamine in the
5. How can the dye be detected once it enters the cave? In most cases, the dye will be so
dilute that it will be invisible to the naked eye. The pools of water in the cave probably
will not turn red or green. Can the fluorescence of the dye help in its detection? Tell the
students that samples of the water are brought out of the cave and to the surface where
they are tested in a fluorometer. A fluorometer can be used to detect very small
quantities of fluorescent dye in solution. A fluorometer is a machine that detects the
amount of light that passes through the water. The dyes will reflect light at different
wavelengths, making it possible to detect fluorescein and rhodamine separately.
6. A fluorometer can detect even a few parts-per-billion of rhodamine or fluorescein. What
does this mean? Tell the students that if they put a single drop of dye into a 50’x25’x4.5’
swimming pool, they have a one part-per-billion solution. 3 drops yields a 3 ppb
Water in the Environment • 121
solution. Certain dyes can only be detected in larger concentrations, such as a part-permillion.
If you put one drop of dye into a 44-gallon barrel, you have a 1-ppm solution.
You may wish to use an eyedropper to illustrate these concentrations.
7. Distribute copies of the attached worksheet. The students should color Sinking Stream
green (representing fluorescein) and Pine Creek Stream red (representing rhodamine).
Have the students use the data on the back of the worksheet to determine which pools
and/or drip sites in the cave could be polluted. Why was testing done before the dye was
injected? Discuss background levels of fluorescence. What might cause background
levels? (Antifreeze or laundry
detergents or other chemicals that contain fluorescein or
rhodamine would show up as background levels.) What seems to be the approximate
background level of rhodamine in this case? Fluorescein? A positive dye concentration
must be at least 3 times greater than the background level.
8. The students should color parts of the cave to illustrate the results of the dye trace. How
do they think the water traveled through the limestone to reach particular sites in the
cave? How long did the water take to reach the cave?
9. Have the students consider the following:
• What effect will the polluted water have on the cave?
• How can the pollution be cleaned up?
• How can the students identify the source of the pollution?
• How many other things could the pollutant be affecting?
• Will the pollutants stay in the cave or will they have a farther-reaching effect?
• What will this do to the wildlife in the cave?
10. Building on what the students have learned in previous activities, discuss:
• what would happen if the limestone was covered with a layer of sandstone.
• How long might the water take to reach the cave?
• What effect will this have on the pollution?
• What about the wildlife?
• What about the cave in the future if the rock above is holding contaminants?
11. How can studies like this help the entire area in the future? Imagine real life place where
dye tracing is taking place, places like Wind Cave National Park. By studying dye in the
cave, what actions do you think will be made on the surface? Notice where the buildings
are and where the water drains. Do you think information like this could help set limits
of the numbers of people
allowed to visit the cave?
What about where they are
able to park their vehicles?
(Concerns about leaking oil,
gas, antifreeze, or other
pollutants.) What other
benefits might come from a
dye trace experiment?
122 • W ater in the Environment
Water in the Environment • 123
124 • W ater in the Environment
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Replies to this discussion thread
|Generic Other||Apr 2012||#25|
|Peace Patriot||Apr 2012||#13|
|Peace Patriot||Apr 2012||#12|
|Peace Patriot||Apr 2012||#19|
|Peace Patriot||Apr 2012||#65|
you ever put a drop of purple dye
|marshall gaines||Apr 2012||#69|
|marshall gaines||Apr 2012||#68|
|marshall gaines||Apr 2012||#52|
|Prometheus Bound||Apr 2012||#16|
|marshall gaines||Apr 2012||#50|
|marshall gaines||Apr 2012||#67|
|marshall gaines||Apr 2012||#53|
|Uncle Joe||Apr 2012||#30|
|rhett o rick||Apr 2012||#37|
|marshall gaines||Apr 2012||#49|
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