Stream Pollution

Vanderbilt Student Volunteers for Science

Fall 2013

Training Presentation

Important!!!

• Please use this resource to reinforce your understanding of the lesson! Make sure you have read and understand the entire lesson prior to picking up the kit!

• We recommend that you work through the kit with your team prior to going into the classroom.

• This presentation does not contain the entire lesson—only selected experiments that may be difficult to visualize and/or understand.

I-II. Introduction and explanation of map and model

• A fish kill has occurred in Harrodsburg River and the nearby lake, and the City Mayor has brought in a special team of scientists to determine the cause of the fish kill.

• Give students a copy of the map observation sheet and have students gather around model.

• Coordinate the map and the model so that students understand where everything is on the model.

II. Explanation of model (cont.)• Explain where runoff from each of

these sources would reach the river.

– It’s important that they understand the significance of the slope of the land, and the direction of water flow in the river.

• Explain that pollution moves the same way.

• The lettered positions on the model represent sources of water, whether they are from wells, ponds, lakes, or streams.

– A, F, G, N, and Q are water samples from wells 100 feet underground.

– All the others are samples taken from surface water - B and C are ponds, E, L, M and O are stream samples, P is a lake, S is spillway water.

III. The Water Cycle• Explain the basics of the water cycle to

the students. Have them refer to the handout.

• The water evaporates from lakes and rivers.

• The water vapor condenses into clouds and precipitation is formed (rain, snow, sleet, etc.)

• When the water falls on the ground some of it percolates (percolation is the movement of water through solids and rocks as ground water).

• The water eventually collects in rivers which carries the water to lakes and oceans, starting the cycle over again.

• Leaching is a process where chemicals that are soluble in water are carried away by moving water or washed into deeper layers of soil. This can contaminate water supplies.

• Wastewater discharge is when waste materials and chemicals are released or washed into surface runoff or river drainage systems.

Illustration courtesy of Illinois State Water Survey, http://www.isws.illinois.edu/docs/watercycle/.

IV. Experiment: Movement of Polluted Water into Lakes and

Rivers• Divide students into 8 groups and

hand out materials to each.• Place one end of the container on

the Styrofoam block so that it is tilted, then pour enough water into the container so that the marbles are covered.

– The water in the marbles represents ground water.

• Dampen the sponge. – The sponge will represent top soil.– The water in the marbles

underneath the sponge represents an aquifer.

– Water next to the sponge becomes a lake.

• Add one drop of food coloring to the top of the sponge near the edge of the container.

– The food coloring represents a point source of pollution.

IV. Experiment cont.

• Hold the cup with the holes in the bottom over the sponge where the red spot is located.

• Add water to the cup so that it drips (rains) above the spot.

• Explain that the “pollutant” diffuses down through the sponge and into the ground water. This in turn flows into the lake and pollutes it.– Remember to reiterate

what each part of the experiment represents in a real life situation.

V. Background for VSVS team

• See manual for details.• The normal pH range for natural waters is between 5.0 and 8.5.

Areas where limestone is found will be on the high end. The acidity of normal rainwater has a pH of 5.5 to 6.5 because of dissolved carbon dioxide. Any rain with a pH below 5.5 is called acid rain.

• Types of pollution • Oxygen is not very soluble in water.

– The solubility decreases with an increase in temperature. Since most fish require at least 5 – 6 ppm to survive, thermal pollution from industry or power plants can cause a fish kill.

– The presence of organic matter, such as animal wastes, can also affect the amount of dissolved oxygen.

– Fertilizers also reduce the level of dissolved oxygen by providing nutrients to algae, which then die and consume oxygen during their decay.

• A range of pH from 6.5 to 8.2 is the best range for most marine life. – Acid runoff from mines or factories can lower the pH and rapidly growing

algae can raise the pH by removing carbon dioxide from the water during photosynthesis.

VII. Testing pH of Water in Wells and Streams.

• Distribute dropper bottles so that all 8 groups have each A-S bottle.

– The letters correspond to the letters on the map• Briefly discuss the pH scale. Take a piece of

the pH Hydrion paper out of its container. Show them a piece and talk about the color chart on the side of the container. Using the dropper bottles with different pH’s (4,7,11) demonstrate how to drop solutions onto the paper and to determine the pH using the chart.

• Each group should then:– Put the bottles in alphabetical order.– Take the top off of the first bottle and squirt a

drop onto a piece of pH paper.– Compare the color of the sample to the side of

the pH paper vial.– Record the estimated pH on the line that

corresponds to the bottle’s label.– Have them repeat this for each sample on a

new piece of pH paper.• Have a VSVS member tabulate all of the

results on the board.

VII. Results • Look at the chart on the board and ask students:

which pH is most common and why? – Samples A, F, G, L, N, Q, and S are pH 7. – A pH of 6 to 7 is common for water that hasn’t been

contaminated.

• Have students gather round the model. Have students look at their observation sheet. You should look at the Map Answer sheet in the sheet protector.

• Discuss the samples that are different from pH 7. – Sample B is pH 9– Samples C and E are pH 9– Sample M is pH 2 – Samples O and P are pH 4.

• Start upstream, and talk about changes from pH 7. – For example, why does sample B have a

measurement of pH 9? (The rock quarry is limestone (calcium carbonate), which gives a basic pH.)

– Why is the runoff from the farm (samples C and E) pH 8? Fertilizers and runoff from cattle feed lots are basic – ammonia from feed lots and lime from fertilizer.

• Have students look at the pH sheet that shows the effects of pH on marine life and determine which samples are causing the fish kill.

– Acidic pH samples

• Ask students to figure out what caused the fish kill by determining where the pollution started.

– Position M on the side of the hill where the mine is

B

C

VII. Results (cont.)

• Note that location N is not polluted and therefore pollution doesn’t come from runoff on that side. At this point you can review the information about acid runoff from coal mines (see manual).

• After students have determined that it is probably runoff from the mine that has caused the low pH of sample M, give each group a piece of iron pyrite, “fools gold” to look at and then collect the pieces.

N (well)

VII. Results (cont.)• Show the students the vial of

solid mine tailings, which is a mixture of iron (II) sulfate, iron (III) sulfate, and other mineral impurities.

• Show the students the vial of a yellow solution of iron (III) sulfate, the oxidation production of iron pyrite.

• Unscrew the lid, dip in a piece of pH paper and show them the result (tests for pH 2).

• Explain why samples O and P are pH 4.

– The water in the stream dilutes the acid runoff from the mine at sample M.

• The spillway sample S is pH 7 so water from the lake has been diluted enough before reaching the end of the spillway

S

O, P

M

VIII. Review

• Review the causes of the different values of pH and how runoff from these sources affects the pH.

• Students may wonder why the well water (sample Q) near the mine isn’t a lower pH. – Point out that the depth of the well allows for dilution – both by

the filtering process through 100 feet of ground and from dilution from the underground aquifer where the bottom of the well is located.

• Mention again that pH is only one measurement that can provide information about the quality of water in the stream or lake. – To gain a true picture, other tests, such as dissolved oxygen

analysis, would be necessary.