Environmental Science Projects

It is important to remember that we as humans are part of the environment. With over 6 billion of us on Earth, our combined actions also have a big impact on the environment. The hopeful thing is that we can be aware of that impact. We can do things as individuals and we can find ways to work together to lessen the detrimental impacts of billions of people. Environmental Science can help us in that work.

• Acid Rain and Aquatic Life
• Are There Dangerous Levels of Lead in Local Soil?
• How Does Soil Affect the pH of Water?
• It's Raining, It's Pouring: Chemical Analysis of Rainwater
• The Receding Night: The Effect of Artificial Light on the Migration Pattern of Daphnia
• I'm Trying to Breathe Here! Dissolved Oxygen vs. Temperature
• Mapping Troposhperic Ozone Levels Over Time

Mapping Troposhperic Ozone Levels Over Time

Objective

The goal of this project is to investigate ozone levels over time using archived data for the United States from the AIRNow website.

Introduction

Ozone (chemical formula: O₃) occurs naturally in the upper atmosphere (stratosphere). It absorbs potentially harmful ultraviolet radiation from the sun that would otherwise reach the earth's surface. Ozone in the stratosphere thus serves a protective function for life on earth.

In the lower atmosphere (troposphere) ozone is produced by chemical reactions from nitrogen oxides (NO_x, chemical compounds with various ratios of nitrogen and oxygen) and volatile organic compounds (VOCs). A compound is said to be "volatile" if it evaporates readily at normal outside temperatures. Both heat and sunlight are also required for the chemical reactions that produce ozone. Nitrogen oxides are produced in exhaust from factories, power plants, cars, and trucks. Chemical solvents and gasoline vapors are major sources for volatile organic compounds in the atmosphere (AIRNow, 2007a).

Ozone is a highly reactive form of oxygen. The oxygen that we use for respiration (chemical formula: O₂) is less reactive. Ozone can more readily form compounds with an unpaired electron in the outermost shell. These compounds, called free radicals, can cause chain reactions that cause indiscriminate damage to molecules in cells. Virtually any large molecule in the cell—proteins, carbohydrates, lipids, and DNA—can be damaged by free radicals. Enzymes (catalase, superoxide dismutases, and glutathione peroxidases) and anti-oxidant molecules from the diet (e.g., vitamins C and E) act as free radical scavengers, and protect cells from damage caused by free radicals.

Since ozone formation in the troposphere requires heat and sunlight, ozone levels are more likely to rise when the temperature is high. However, other conditions, such as an increase in the pollutants from which ozone is formed, can also lead to ozone elevation. In this project, you can use map data from the U.S. Environmental Protection Agency and other government agencies (AIRNow, 2007c) to track ozone levels in your area under different seasonal conditions to find out when ozone levels are most likely to be elevated.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• Ozone
• Nitrogen oxides (NO_x)
• Volatile organic compounds (VOCs)
• Troposphere
• Stratosphere
• Electron
• Electron shells
• Free radical
• Parts per billion (ppb)
• Air Quality Index (AQI)

Questions

• Why is ozone in the stratosphere protective?
• Why is ozone in the troposphere harmful?
• How does ozone form in the troposphere?
• What conditions make ozone more likely to form?

Bibliography

• The AIRNow website has a page designed for students. Among other resources, you can find Flash animations on how ozone is formed, how ozone acts as a protectant high in the atmosphere but as a pollutant at ground level, and the sources and dangers of particle pollutants:
  AIRNow, 2007a. "AIRNow—Air Quality Students," AIRNow, a cross-agency U.S. Government website [accessed April 20, 2007] http://airnow.gov/index.cfm?action=airnow.student.
• A map of the current Air Quality Index for the continental U.S. can be found at:
  AIRNow, 2007b. "AIRNow National Overview," AIRNow, a cross-agency U.S. Government website [accessed April 20, 2007] http://airnow.gov/index.cfm?action=airnow.main.
• Maps of ozone levels for states and local regions can be found at:
  AIRNow, 2007c. "Air Quality Maps," AIRNow, a cross-agency U.S. Government website [accessed April 20, 2007] http://airnow.gov/index.cfm?action=airnow.currentmaps.
• For information on the effects of ozone on people, animals, and plants, see:
  • Allen, J., 2002. "The Ozone We Breathe," NASA Earth Observatory Reference [accessed April 20, 2007] http://earthobservatory.nasa.gov/Library/OzoneWeBreathe/.
  • AIRNow, 2007d. "Ozone and Your Health," AIRNow, a cross-agency U.S. Government website [accessed April 20, 2007] http://airnow.gov/index.cfm?action=static.brochure.
  • For information on how atmoshperic ozone is monitored, see:
    Allen, J., 2003. "Watching Our Ozone Weather," NASA Earth Observatory Reference [accessed April 20, 2007] http://earthobservatory.nasa.gov/Library/OzoneWx/.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• Computer with Internet connection
• Color printer

Experimental Procedure

Obtaining Air Quality Data

1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
2. To examine ozone levels for a U.S. state or local region, go the AIRNow Air Quality Maps webpage (AIRNow, 2007c).

3. Click on your state of interest, or select it from the drop-down list.
4. Next, you'll see an interface like the one below, which you can use to select a local region within a state (if available), and a date for viewing ozone map data. In the example below, we are choosing to examine data from "San Francisco Bay Area" region within California.

5. Make your selections for local region (if any) and desired date from the drop-down lists. Use the check boxes to select which maps you want, then click on the "Display Maps Below" button to show the mapped data.

6. A convenient way to scan several weeks' worth of data is to use the "Switch to Monthly Thumbnail Overview" option.

7. With the monthly thumbnails, you can scan several weeks' worth of data, and select dates of interest to see maps at higher resolution. Click on any of the thumbnail maps to see the data at full size.

8. The image below shows an example of a 1-Hour Average Peak Concentration map. The data is from the San Francisco Bay Area, for July 21, 2006. The map shows the highest concentration of ozone for each monitoring area during the course of the day. The legend for the colors used on the map is shown at right. The peak for each area can occur at a different time of day, so the data is not necessarily from any single time point during the day. You can also see an 8-hour average, or you can view an animated loop of time points throughout the day.

9. The Variations section has ideas for comparisons you could investigate with map data.

Variations

• Are there seasonal variations in ozone concentrations? For example, you could compare ozone levels in winter months vs. summer months.
• Sometimes the local climate can vary markedly within a small geographic area. For example, in the San Francsico Bay Area (see the map, above) there are dozens of local microclimates. You have the Pacific Ocean, the San Francisco Bay, and coastal mountain ranges all in close proximity. The air tends to be cooler near the ocean and the bay, and rises rapidly in summer months as you move inland. What effect(s) do you see in your area that may be attributable to local variations in elevation and/or bodies of water?
• Do research on the sources of pollutants that form tropospheric ozone: nitrogen oxides (NO_x) and volatile organic compounds. Are ozone precursors produced in higher amounts on weekdays vs. weekends? Compare weekend data with weekday data to see if you can find consistent differences in ozone levels.

Credits

Andrew Olson, Ph.D., Science Buddies

I'm Trying to Breathe Here! Dissolved Oxygen vs. Temperature

Objective

Dissolved oxygen is an important measure of water quality for aquatic life. In this project you will use a test kit to measure the level of dissolved oxygen in water samples. This project has two goals:

1. to measure dissolved oxygen in water samples at different temperatures, and
2. to determine the saturating oxygen concentration for water samples at different temperatures.

Introduction

Dissolved oxygen is one of many measures of water quality, but an important one for aquatic life. Like land animals, fish and shellfish require oxygen to survive. When oxygen levels fall below 5 mg/l, fish are stressed. At oxygen levels of 1–2 mg/l, fish die.

The amount of oxygen that can dissolve in water (i.e., the saturating concentration of oxygen) depends on water temperature. Colder water can hold more oxygen than warmer water. You'll see for yourself just how much more in this project.

Where does dissolved oxygen come from?

There are two main sources of dissolved oxygen: air and photosynthesis. Consider photosynthesis first. You probably know that photosynthesis is the fundamental biological process that uses light energy to produce sugar from carbon dioxide and water. Oxygen is a by-product of photosynthesis. Both algae (phytoplankton, seaweeds) and plants can be found in natural bodies of water. These organisms are net producers of oxygen in the daytime, but at night become net consumers of oxygen.

Now consider oxygen from the air. At the surface of the water, oxygen from the air equilibrates with oxygen dissolved in the water. This is a dynamic equilibrium: the oxygen molecules are in constant motion. At any given moment, some are leaving the water for the air, and some are leaving the air to dissolve in water. At equilibrium, there is a balance. On average, an equal number of oxygen molecules are leaving and entering the water. If the water temperature increases, the water can't hold as much oxygen as before—the water is oversaturated with oxygen. For a time, there will be more oxygen molecules leaving the water than entering it from the air. Then a new equilibrium will be reached, with less oxygen in the water than before.

Moving water has a rougher surface than still water. With more surface area in contact with air, moving water will equilibrate with air more quickly. (You'll make use of this in your experiment.) In natural situations, water can also become stratified into different layers (see the Science Buddies project Can Water Float on Water?). For example, cold water is denser than warm water, and salt water is denser than fresh water. Can you think of ways that different layers of water might form in a lake or ocean? What do you think happens to the oxygen in a colder layer of water trapped under a warmer layer of water? (Remember that the warmer layer cannot hold as much dissolved oxygen as the colder layer. See the Variations section for a project idea on this topic.)

What causes dissolved oxygen levels to vary?

So far we've seen that dissolved oxygen can come from the air or from photosynthesis, and that when water warms up, there is a net loss of dissolved oxygen. Besides warming, how else can dissolved oxygen become depleted? The answer is another fundamental biological process: respiration. Respiration uses oxygen to break down molecules, in order to produce energy for cells. So the amount of dissolved oxygen will be determined by:

• how much oxygen the water can hold (temperature-dependent),
• how much surface area is available for diffusion from the air,
• how much oxygen is produced by photosynthesis, and
• how much oxygen is consumed by respiration.

Here is a real-world example of variations in dissolved oxygen levels from a continuous monitoring site in the Chesapeake Bay (Maryland DNR, 2006). All of the data were collected at the same location over the same time period. The first graph shows dissolved oxygen, the second graph shows temperature and the third graph shows chlorophyll concentration (a measure of how much algae is present in the water). Notice the daily fluctuations in oxygen level and water temperature. Notice also how the oxygen level and chlorophyll level both declined toward the end of the time period.

Figure 1. The three graphs show (from top to bottom) dissolved oxygen, water temperature, and chlorophyll concentration at a monitoring site in the Chesapeake Bay over a one-week period. (Maryland DNR, 2006)

Sometimes imbalances occur that lead to skyrocketing concentrations of algae. For a project that investigates water quality measures and algal blooms, see the Science Buddies project Harmful Algal Blooms. You can also check out the references in the Bibliography section.

How is dissolved oxygen measured?

Dissolved oxygen can be measured with an electronic metering device or with a chemical test. Dissolved oxygen meters cost hundreds of dollars, so this project will use the chemical testing method. You can buy a dissolved oxygen test kit for around $50. The kit will test 100 water samples. Commercial test kits are based on the "modified Winkler method." You can read more details on this method in the Bales and Gutmann reference in the Bibliography, but here is a basic outline of how the test works:

1. A water sample is collected and the sampling container is sealed under water. This prevents exposure of the sample to the atmosphere.
2. A chemical is added to the water sample to react with all of the dissolved oxygen in the sample. An insoluble precipitate is formed.
3. Additional chemicals are added to drive the first reaction to completion, and to prevent an unwanted reaction from occurring in the final step.
4. A third addition causes the precipitate to change color.
5. The oxygen is now "fixed" and can no longer react with the atmosphere.
6. In the final step, a titration is performed. In this step, a chemical is added in liquid form, one drop at a time. The added compound reacts with the colored precipitate, causing it to lose color. The water sample is mixed after the addition of each drop. When the color change is complete (sample is clear again), it means that the added compound has reacted with all of the fixed oxygen in the sample. By counting the number of drops that were added, the amount of oxygen in the sample can be calculated.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• dissolved oxygen,
• titration,
• oxygen saturation,
• hypoxia,
• harmful algal blooms,
• Gulf of Mexico "dead zone,"
• photosynthesis,
• respiration.

More advanced students will want to study the chemistry used in the test kits (modified Winkler method). The reference by Bales and Gutmann in the Bibliography is a good place to start.

Questions

• What concentration of dissolved oxygen is required to support aquatic life?
• What are some of the processes that increase dissolved oxygen concentration in natural bodies of water?
• What are some of the processes that decrease dissolved oxygen concentration in natural bodies of water?

Bibliography

• For more background information on water quality measures, including dissolved oxygen, see:
  Munson, B.H. et al., 2005. "Water on the Web: Understanding: Water Quality: Parameters: Dissolved Oxygen," University of Minnesota Duluth and Lake Superior College [accessed May 15, 2006] http://waterontheweb.org/under/waterquality/oxygen.html.
• The dissolved oxygen test kits can seem rather mysterious. The instructions that come with the kits explain the procedure step-by-step, but they do not explain how the test works. The following webpage is a good resource for understanding what is going on with each step. (For advanced students, there is also a separate page with more detailed information on the chemical reactions involved.):
  Bales, R. and C. Gutmann, date unknown. "The Chemistry Section: Dissolved Oxygen," Department of Hydrology and Water Resources, University of Arizona [accessed May 15, 2006] http://www.hwr.arizona.edu/globe/Hydro/kit_chem/DOchem.html.
• Archived data (including dissolved oxygen) from Maryland DNR continuous monitoring stations in Chesapeake Bay can be found at:
  Maryland DNR, 2006. "Eyes on the Bay," Maryland Department of Natural Resources [accessed May 15, 2006] http://mddnr.chesapeakebay.net/eyesonthebay/index.cfm.
• These websites have background information on harmful algal blooms, which can deplete water of dissolved oxygen:
  
  • Anderson, D.A., 2006. "Red Tide and Harmful Algal Blooms," [accessed May 1, 2006] http://www.whoi.edu/redtide/.
  • NOAA, 2006a. "Harmful Algal Blooms," NOAA's National Ocean Service [accessed May 1, 2006] http://www.oceanservice.noaa.gov/topics/coasts/hab/welcome.html.
• These sites have background information on the Gulf of Mexico "Dead Zone," a massive area of hypoxic water that appears every summer near the mouth of the Mississippi River:
  
  • Science Museum of Minnesota, date unknown. "Dead Zone Home," Science Museum of Minnesota [accessed May 15, 2006] http://www.smm.org/deadzone/.
  • Bruckner, M., 2006. "The Gulf of Mexico Dead Zone," Science Education Resource Center, Carleton College [accessed May 15, 2006] http://serc.carleton.edu/microbelife/topics/deadzone/index.html.
• Roach, J., 2005. "Gulf of Mexico 'Dead Zone' Is Size of New Jersey," National Geographic News, May 25, 2005 [accessed May 15, 2006] http://news.nationalgeographic.com/news/2005/05/0525_050525_deadzone.html.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• dissolved oxygen test kit;
  Note: kits are available from two manufacturers, Hach and LaMotte. Both use essentially the same chemistry (modified Winkler method, see Bales and Gutmann reference in the Bibliography). Both are available from multiple online suppliers; a web search on the brand name + dissolved oxygen test kit will locate them.
  • Hach OX-2P, single-parameter test kit for dissolved oxygen, will test 100 samples,
  • LaMotte 7414 or 5860 dissolved oxygen test kit, will test 50 samples.
• thermometer (range 0°C–100°C),
• gloves,
• safety glasses/goggles,
• at least 3 containers (1 L or more) for water, one to be heated on stove,
• spray bottle (for rinsing test container in the field),
• sealable container (at least 500 ml, for test waste in the field).
• Optional equipment for aerating the water samples (if not readily available, see the Experimental Procedure section for an alternative aeration method):
  • aquarium aerator pump,
  • 2.5 cm or larger fine-mist air stone,
  • plastic aquarium tubing.

Experimental Procedure

Safety notes: Read and follow all of the instructions in your test kit, including all safety precautions. Wear safety goggles and gloves when using test kit reagents. Avoid skin contact with test kit reagents.

In this experiment, you will measure how dissolved oxygen changes in water samples at different temperatures. You will test both aerated and non-aerated water samples at each temperature.

1. Do your background research and make sure that you are knowledgeable about the terms, concepts, and questions, above.
2. Read the instructions that came with your dissolved oxygen test kit so that you know how to perform the test. The Bales and Gutmann reference in the Bibliography has an explanation of what is happening with each of the steps, plus a separate page with a more detailed explanation of the chemistry involved (for more advanced students).
3. Collect your water sample (4 l minimum). The sample can be from a natural body of water, such as an estuary, ocean, lake, pond, or stream. You can also use plain old tap water.
4. Take a baseline dissolved oxygen measurement.
   1. When you collect your water sample, bring along your dissolved oxygen test kit, thermometer, spray bottle and sealable waste container.
   2. Measure the temperature of the water at the collection site.
   3. Test the dissolved oxygen content of the water at the collection site. This is your baseline measurement of dissolved oxygen.
   4. When your measurement is complete, discard the test sample down a drain; do not throw it back in the body of water you sampled. Do the same with the rinse water when you clean the sampling container. If need be, bring the test waste back home in a sealable container and flush it down the drain at home.
   5. To be sure that your results are consistent, you should repeat the test at least three times, using a fresh sample each time. Use the spray bottle to rinse your test container. Discard rinse water down a drain or into your waste container for disposal at home.
   6. Be sure to record the temperature of the water.
5. At home, divide your water sample equally into three separate containers:
   1. container 1 will be cooled with ice,
   2. container 2 will be allowed to equilibrate to room temperature, and
   3. container 3 will be heated slightly.
6. Add enough ice to container 1 to bring the water to about 4–8°C. When the water has cooled, record the temperature and measure the dissolved oxygen concentration. As before, you should run the test at least three times, to be sure that your results are consistent.
7. Next, aerate the sample and re-test. The point of aeration is to saturate the water with oxygen (i.e., dissolve as much oxygen as the water can hold). You can aerate the water with an aquarium aeration pump and airstone. Lots of small bubbles work best. Allow 5–10 minutes for equilibration. Alternatively, you can pour the water back and forth between two large buckets for 5–10 minutes to aerate the water. In either case, check the temperature periodically and add more ice if needed to maintain the temperature.
8. When the water has been aerated, repeat the dissolved oxygen test. Make sure to record the temperature. As before, you should run the test at least three times to be sure that your results are consistent.
9. Run similar tests (aerated and non-aerated) for container 2, the water sample at room temperature (it may take a few hours to equilibrate, depending on how cold the sample was to start).
10. Run similar tests (aerated and non-aerated) for container 3, the water sample that you heat. You can warm it on the stove, or in the microwave. Mix the sample gently and check the temperature frequently. Aim for a temperature from 35–40°C. You don't want to scald yourself when testing the dissolved oxygen concentration.
11. Summarize your results in a table. For example:

    Sample	Aerated?	Temp #1	DO #1	Temp #2	DO #2	Temp #3	DO #3
    Baseline	N
    Chilled	N
    Chilled	Y
    Room temp	N
    Room temp	Y
    Warmed	N
    Warmed	Y

12. Make a graph of your results. You can plot dissolved oxygen vs. temperature. Use separate symbols for:
    1. your baseline sample,
    2. your non-aerated samples,
    3. your aerated samples.
13. From your graph, do you think your original baseline sample was saturated with oxygen? Why or why not?

Variations

• Does seawater hold as much dissolved oxygen as freshwater at the same temperature? Compare aerated fresh- and salt-water samples at different temperatures. If the ocean is too far away, make your own saltwater by adding between 30 and 35 g of table salt for each liter of water. Use a double bath for cooling the saltwater sample down without diluting it (saltwater sample in the inner container, surrounded by ice water in the outer container).
• How could you modify the experiment to test whether the initial baseline sample is saturated with oxygen?
• Measure dissolved oxygen in water with and without aquatic plants. If you have access to a planted aquarium, it would be interesting to monitor oxygen levels both in daytime and at night. As in the experiment described above, this experiment could be done both with and without aeration. If fish are present, monitor the nighttime oxygen level frequently. Also, monitor the fish for signs of oxygen stress (e.g., increased gill beat rate, gulping at the surface).
• If you live near an estuary or other natural body of water, you could monitor dissolved oxygen from one or more sites over time. For example, you could sample multiple times during a 24-hour period to track the daily fluctuation of oxygen. Alternatively, you could sample over a longer time period, and look for changes correlated with weather systems. What effect would you predict for cloudy weather?
• Compare dissolved oxygen in a still portion of a stream vs. a rapidly flowing portion. Or compare oxygen levels in water sampled at different depths.
• For a more advanced project that uses archived water quality data from monitoring stations in the Chesapeake Bay, see the Science Buddies project Harmful Algal Blooms in the Chesapeake Bay.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

• Maryland DNR, 2005. "Eyes on Dissolved Oxygen," Maryland Department of Natural Resources, Eyes on the Bay Lesson Plan Series [accessed May 15, 2006] http://mddnr.chesapeakebay.net/eyesonthebay/lesson_plans/do_lesson_plan.pdf.

The Receding Night: The Effect of Artificial Light on the Migration Pattern of Daphnia

Objective

The purpose of this project is to determine if artificial light has an effect on the migration pattern of Daphnia in a simple laboratory experiment, in a simulation of a pond habitat, and in their natural pond environment.

Experimental Procedure

The experiment had to be done in two phases. First, the Daphnia's natural migration pattern was observed. Then the effect of artificial light on these patterns was studied and compared to the original migration pattern. Daphnia were observed in test tubes and then in 3-foot columns of water and in their natural pond environment during the day and at night. Five different artificial light sources were introduced and the Daphnia were observed.

Credits

Dana A. Feeny

It's Raining, It's Pouring: Chemical Analysis of Rainwater

Objective

The goal of this project is to assess the water quality of rainwater collected from different geographical areas. The water quality measures used in this project are hardness, pH, and plant growth. Additional measures could be chosen to expand this project.

Introduction

Is the chemistry of rainwater from different geographical regions similar or different? How does rainwater chemistry relate to that of local surface water? How is rainwater chemistry affected by large-scale weather patterns? Does rainwater chemistry affect the growth of plants? These are some of the many questions you could choose to pursue with this project.

This project is based on Jonathan Allison's 2003 California State Science Fair entry. Here is how Jonathan summarized his experimental procedure: "I contacted friends and family from 11 different cities in the United States and asked them if they could help me by collecting rainwater from their city. After they collected it, they shipped it back to me. Then I tested the rainwater for hardness, using the chemical process of titration. Next I tested the rainwater for pH levels. Then I planted radish seeds in potting soil and watered each set of seedlings with rainwater from a different city. I observed, measured and recorded any growth or changes daily for seven days." (Allison, 2003)

Water Hardness

Water hardness is a measure of dissolved compounds (e.g., magnesium carbonate, calcium carbonate) in the water. These compounds can precipitate out in boilers and water heaters (scaling). Hard water makes less suds with soap and detergent, so you need to use more soap and detergent to get clothes and dishes clean with hard water. General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified as soft; 61 to 120 mg/L as moderately hard; 121 to 180 mg/L as hard; and more than 180 mg/L as very hard (USGS, date unknown).

Figures 1 and 2 show USGS water hardness data for the continental United States. Figure 1 is a histogram showing the mean hardness data for each of the 344 stations sampled. Figure 2 is a map of the U.S., showing the regional patterns of groundwater hardness. In both cases, the data is from 1975, but the patterns shown have proven to be stable over time.

Figure 1. Histogram of U.S. groundwater hardness from 344 collection stations (USGS, 1975 data).

Figure 2. Map of U.S. groundwater hardness from 344 collection stations (USGS, 1975 data).

pH

Acidity and alkalinity are measured with a logarithmic scale called pH. pH is the negative logarithm of the hydrogen ion concentration:

pH = −log [H⁺] .

What this equation means is for each 1-unit change in pH, the hydrogen ion concentration changes ten-fold. Pure water has a neutral pH of 7. pH values lower than 7 are acidic, and pH values higher than 7 are alkaline (basic). The table below has examples of substances with different pH values (Decelles, 2002; Environment Canada, 2002; EPA, date unknown).

Table 1. The pH Scale: Some Examples

pH Value	H+ Concentration Relative to Pure Water	Example
0	10 000 000	battery acid
1	1 000 000	sulfuric acid
2	100 000	lemon juice, vinegar
3	10 000	orange juice, soda
4	1 000	tomato juice, acid rain
5	100	black coffee, bananas
6	10	urine, milk
7	1	pure water
8	0.1	sea water, eggs
9	0.01	baking soda
10	0.001	Great Salt Lake, milk of magnesia
11	0.000 1	ammonia solution
12	0.000 01	soapy water
13	0.000 001	bleach, oven cleaner
14	0.000 000 1	liquid drain cleaner

Figure 3 shows a map of the average pH of precipitation in the continental U.S. for the year 1992. "The areas of greatest acidity (lowest pH values) are located in the Northeastern United States. This pattern of high acidity is caused by the large number of cities, the dense population, and the concentration of power and industrial plants in the Northeast. In addition, the prevailing wind direction brings storms and pollution to the Northeast from the Midwest, and dust from the soil and rocks in the Northeastern United States is less likely to neutralize acidity in the rain." (USGS, 1997)

Figure 3. Map of U.S. annual average precipitation pH for 1992. (USGS, 1997).

Plant Growth

Most plants prefer soil that is near neutral pH. There are particular varieties (strawberries, azaleas and rhododendrons, for example) that prefer acidic soil. Soil pH also influences how readily available many soil nutrients are to plants.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• titration,
• water hardness,
• pH.

More advanced students will also want to understand the following terms and concepts:

• molarity,
• stoichiometry.

Bibliography

• Wikipedia contributors, 2006. "Titration," Wikipedia, The Free Encyclopedia [accessed May 9, 2006] http://en.wikipedia.org/w/index.php?title=Titration&oldid=51987922.
• These USGS webpages have information on patterns of water hardness of rivers and acidity in rainwater across the United States.
  
  • USGS, date unknown. "Explanation of Hardness," United States Geological Survey [accessed May 9, 2006] http://water.usgs.gov/owq/Explanation.html.
  • USGS, 1997. "What Is Acid Rain?" United States Geological Survey [accessed May 9, 2006] http://pubs.usgs.gov/gip/acidrain/2.html.
• These sites explain the pH scale:
  • Environment Canada, 2002. "Kids' Corner pH Scale," The Green Lane: Acid Rain, Environment Canada website [accessed March 14, 2006] http://www.ec.gc.ca/acidrain/kids.html.
  • Decelles, P., 2002. "The pH Scale," Virtually Biology Course, Basic Chemistry Concepts, Johnson County Community College [accessed March 14, 2006] http://staff.jccc.net/pdecell/chemistry/phscale.html.
• Review pages on moles:
  Park, J.L., 2004. "The Mole Table of Contents," The ChemTeam, A Tutorial for High School Chemistry [accessed May 9, 2006] http://dbhs.wvusd.k12.ca.us/webdocs/Mole/Mole.html.
• Allison, J.R., 2003. "It's Raining, It's Pouring, the Radishes Are Growing: Chemical Analysis of Rainwater for the Nation's Food Production," California State Science Fair Project Abstract [accessed May 9, 2006] http://www.usc.edu/CSSF/History/2003/Projects/J0902.pdf.

Materials and Equipment

• This project requires planning ahead. Remember that it will take some time for your volunteers to collect samples and send them to you. You also need to allow time (at least one week) for the plant growth experiment once you have received all of the samples. Start early and make sure your volunteers send their samples in a timely manner!
  • Where to get samples? You will need to obtain rainwater samples from a wide geographical area. Consult the maps in the Introduction for historical patterns of variation. Ask friends and relatives to collect samples for you.
  • How much water do I need? Check your test kit instructions (see below) to see how much water is required for each test (usually about 5 ml). You will want to repeat your tests for each sample at least 3 times to assure that your results are consistent. So you'll need a minimum of 30 ml just for testing (best to plan on more). You will also need water for the plant growth experiment. Calculate how much water you will need for plant growth, and add 50 ml for testing purposes. This is how much rainwater each of your volunteers will have to send to you.
  • How should my volunteers collect rainwater samples? Simply putting a jar out on the lawn during a rainstorm is not going to be very efficient. In order to get enough water, your volunteers need a large catchment area. Probably the most straightforward solution is to collect water from the roof, by placing a collection jar underneath a downspout.
  • Make sure your volunteers label the water sample with the date and location from which it was collected.
• For performing the water quality tests, the simplest method is to use a pre-packaged kit designed for testing aquarium water. There are several different brands available. You should be able to find a choice at a local pet store that sells fish. The kit will say how many water samples it will test. You should be able to find kits to test 50 samples for under $10. The kits you need for this project are:
  • general hardness (GH) test kit,
  • pH test kit.
• For the plant growth experiment, you'll need:
  • radish seeds, (or other suitable, fast-growing seeds),
  • small containers (peat pots or seedling trays),
  • potting soil, and
  • a measuring device for dispensing water.

Experimental Procedure

1. For the water hardness and pH tests, follow the instructions that come with the water test kit. When titrating samples, it is important to mix the solution well after each drop of test solution is added.
2. For the plant growth portion of the experiment, it is important to keep all of the other growth conditions (sun exposure, soil, temperature, etc.) constant, and to vary only the source of water used for the plants. Be sure to use the same amount of water. Consult the Science Buddies resource, Measuring Plant Growth for methods you can use to quantify differences in growth.

Variations

• Does rainwater chemistry in your area vary with weather patterns? Collect samples over several weeks or months, and test the water quality. Keep track of the weather systems that produced the precipitation. Were there variations in the ultimate source of the moisture? Can you correlate these variations with changes in rainwater chemistry?
• If you live in an urban area, is rainwater chemistry affected by smog? Check the air quality reported in the newspaper for the days that samples were collected. Do you see differences in rainwater chemistry after days with high smog compared to days with cleaner air?
• For the samples in your study, how does rainwater hardness compare with groundwater hardness? (See Figure 2 in the Introduction, above.) How does the acidity compare to the 1992 U.S. data? (See Figure 3 in the Introduction, above.)
• Here are two related Science Buddies projects you might want to check out:
  • How Does Soil Affect the pH of Water?, and
  • Conductance as a Water Quality Measurement.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

This project was based on:

• Allison, J.R., 2003. "It's Raining, It's Pouring, the Radishes Are Growing: Chemical Analysis of Rainwater for the Nation's Food Production," California State Science Fair Project Abstract [accessed May 9, 2006] http://www.usc.edu/CSSF/History/2003/Projects/J0902.pdf.

How Does Soil Affect the pH of Water?

Objective

The objective of this experiment is to measure how contact with different types of soil changes the pH of water.

Introduction

The level of acidity or alkalinity of a soil is one indicator of the soil's health and suitability for growing particular types of plants. Acidity and alkalinity are measured with a logarithmic scale called pH. pH is the negative logarithm of the hydrogen ion concentration:

pH = −log [H⁺] .

What this equation means is for each 1-unit change in pH, the hydrogen ion concentration changes ten-fold. Pure water has a neutral pH of 7. pH values lower than 7 are acidic, and pH values higher than 7 are alkaline (basic). The table below has examples of substances with different pH values (Decelles, 2002; Environment Canada, 2002; EPA, date unknown).

Table 1. The pH Scale: Some Examples

pH Value	H+ Concentration Relative to Pure Water	Example
0	10 000 000	battery acid
1	1 000 000	sulfuric acid
2	100 000	lemon juice, vinegar
3	10 000	orange juice, soda
4	1 000	tomato juice, acid rain
5	100	black coffee, bananas
6	10	urine, milk
7	1	pure water
8	0.1	sea water, eggs
9	0.01	baking soda
10	0.001	Great Salt Lake, milk of magnesia
11	0.000 1	ammonia solution
12	0.000 01	soapy water
13	0.000 001	bleach, oven cleaner
14	0.000 000 1	liquid drain cleaner

Most plants prefer soil that is near neutral pH. There are particular varieties (strawberries, azaleas and rhododendrons, for example) that prefer acidic soil. Soil pH also influences how readily available many soil nutrients are to plants.

In this project, you will measure pH values of different types of soils, and you will see how the soil affects the pH of water that comes in contact with it.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• pH,
• soil types

Questions

• What value of pH is neutral?
• What range of pH values is acidic?
• What range of pH values is basic?

Bibliography

• These sites explain the pH scale:
  • Environment Canada, 2002. "Kids' Corner pH Scale," The Green Lane: Acid Rain, Environment Canada website [accessed March 14, 2006] http://www.ec.gc.ca/acidrain/kids.html.
  • Decelles, P., 2002. "The pH Scale," Virtually Biology Course, Basic Chemistry Concepts, Johnson County Community College [accessed March 14, 2006] http://staff.jccc.net/pdecell/chemistry/phscale.html.
• NSSF, 1998. "Soil Quality Indicators: pH," National Soil Survey Center, USDA [accessed March 14, 2006] http://soils.usda.gov/sqi/files/indicate.pdf.
• Bickelhaupt, D. and R. Schmedicke, 2006. "Soil pH: What It Means," SUNY College of Environmental Science and Forestry [accessed March 14, 2006] http://www.esf.edu/PUBPROG/brochure/soilph/soilph.htm.
• These site have lots of information about soil, including soil formation, soil composition, soil types, and soil pH:
  • BBC, 2006. "Know Your Plot: Analysing Your Soil," How To Be a Gardener: The Complete Online Guide [accessed March 14, 2006] http://www.bbc.co.uk/gardening/htbg/module1/soil_types1.shtml.
  • Moor, F., 1999. "The World of Soil," [accessed March 14, 2006] http://web.ukonline.co.uk/fred.moor/soil/index.htm.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• soil/water pH meter, with resolution of ±0.1 pH units, range 1 to 14 (available at nurseries/gardening stores);
• small shovel or trowel for gathering soil samples;
• plastic bags;
• marking pen;
• stick-on lables;
• places to gather different types of soil;
• plant pots (with drainage holes at bottom;
• paper cups;
• tap water.

Experimental Procedure

1. Do your background research so that you understand the terms, concepts, and questions, above.
2. Gather samples of different soil types. Here are some things to keep in mind:
   • For each different area or soil type, gather 10–15 small samples, and mix them together.
   • Keep each soil type in a separate plastic bag.
   • Label each of your bags.
   • Take notes in your lab notebook about the site where you collected each sample. Include information about the general area (your yard, a park, the beach, a pine forest, etc.), and the kinds of plants (if any) growing in the area.
   • Try to include as wide a variety of soil types and environments as you can.
   • For a method for determining soil type, see the Science Buddies project Get Down and Dirty: How Does Soil Change with Depth? You can use step 10 in the Experimental Procedure from that project to determine the soil texture, using a sample of soil from each site.
3. Read the instructions for your soil pH meter to learn how to use it properly. Make sure you follow any instructions for calibrating the pH meter before using it.
4. Use the soil pH meter to measure the pH of each soil sample.
5. Use the soil pH meter to measure the pH of the water before it contacts the soil.
6. Then, for each soil type, fill a plant pot about two-thirds full with soil. Try to use the same amount of soil (by weight) in each pot. (You can estimate the weight by hand, but if you have a scale that's even better.)
7. Add enough water to the soil in the pot so that it drips out the bottom, and catch the run-off in a clean paper cup.
8. Measure and record the pH of the run-off water.
9. Which soils change the pH of the water the most? The least?

Variations

• For soils with pH that is more acidic or more basic than your tap water: if you keep watering the soil sample, does the pH of water eventually stop changing? Has the pH of the soil changed? How much water did it take? Does this vary with soil type? What does this tell you about irrigation and soil pH?
• How does the addition of fertilizer affect soil pH? Does the fertilizer type matter? Do background research on fertilizers and pH and then devise an experiment to test fertilizer-induced pH changes.
• Use an aquarium test kit to check nitrate levels in water drained from soil pots with and without fertilizer. Be sure to check a sample of the plain tap water too, as a control. Is there less nitrate run-off when plants are growing in the pots?

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

• Decelles, P., 2002. "The pH Scale," Virtually Biology Course, Basic Chemistry Concepts, Johnson County Community College [accessed March 14, 2006] http://staff.jccc.net/pdecell/chemistry/phscale.html.
• Environment Canada, 2002. "Kids' Corner pH Scale," The Green Lane: Acid Rain, Environment Canada website [accessed March 14, 2006] http://www.ec.gc.ca/acidrain/kids.html.
• EPA, date unknown. "pH Scale," What Is Acid Rain, U.S. Environmental Protection Agency [accessed March 14, 2006] http://www.epa.gov/acidrain/education/site_students/phscale.html.
• Staff, 2005. "Agricultural Ideas for Science Fair Projects," Agricultural Research Service, U.S. Department of Agriculture [accessed March 14, 2006]
  http://www.ars.usda.gov/is/kids/fair/ideasframe.htm.

Are There Dangerous Levels of Lead in Local Soil?

Objective

The purpose of this project is to determine whether local soil contains dangerous levels of lead. This is significant because the results will indicate where the soil is hazardous to the health of humans, especially young children.

Introduction

Lead is an element that has been used for centuries in many objects found in and around the home. Lead is also highly toxic to human health. In the 1980's federal, state, and local governments moved to ban the use of lead in common household materials. However, there are products that were created before the 1980's still in use today. Many areas also have soil contaminated from previous use of these products. Are there areas around you where residual products have caused the soil to be hazardous to the health of humans, especially young children?

Terms, Concepts and Questions to Start Background Research

In order to properly conduct this experiment you should become an expert on lead. You should understand:

• What are the health effects of lead?
• What levels of lead are hazardous?
• When does lead become hazardous to humans?
• How does lead get into soil?

Bibliography

General information on lead, its history, and its health hazards, and areas around your community that you might want to check for lead contamination can be found at the following websites:
http://www.epa.gov/lead/
http://www.epa.gov/lead/leadpbed.htm#Brochures
http://www.epa.gov/history/topics/perspect/lead.htm
http://www.niehs.nih.gov/external/faq/alpha-l.htm#lead

A good list of additional offline sources from Environmental Science Archive of Ask A Scientist:
http://www.newton.dep.anl.gov/newton/askasci/1995/environ/ENV134.HTM

Guidelines for soil sampling for residential property:
http://www.ecy.wa.gov/pubs/0309044.pdf
http://www.ext.colostate.edu/pubs/crops/00500.html

Materials and Equipment

• Resealable plastic bags to hold samples
• Shovel
• Stainless steel spoon
• Permanent marker
• Large bowl or bucket
• Paper towels

Experimental Procedure

1. Determine your sampling locations and where, within that location, you are going to collect sub-samples. Lead concentrations can vary from one spot to another, so it is important to use a composite of sub-samples to evaluate an area rather than relying on a single sample. The exception to the composite technique would be if you are trying to get a specific measurement for a small area (for example, around a play structure).
2. Collecting a composite sample (adapted from the Washington State Department of Ecology Arsenic and Lead Soil Sampling Guidance Brochure):
   
   • Sketch out a map of the location that you will be testing and note where you will be collecting each of your samples. You should collect at least 4 samples from smaller areas (for example, a small yard that is less 800 sq. ft.) and at least 15 samples from larger areas (for example, a small neighborhood park).
   • Remove material on the soil surface (grass, leaves, etc.), exposing the soil.
   • Dig a hole with your shovel. The depth will depend on the test you are using to analyze the soil—check the instructions on the home kit or with the analyzing lab to get a specific soil depth recommendation for your samples. (Typically you should not dig deeper than 6 inches).
   • Using your spoon, scrape some soil from the hole and place it in a clean plastic bag. Make sure to collect only soil—do not include rocks, grass, or wandering insects.
   • Clean the spoon with a paper towel to remove any visible traces of soil.
   • Repeat steps 2–5 for each of the sub-samples for this location.
   • Once you have collected all of the sub-samples for a location, put equal amounts of each sub-sample into your bowl and mix them together.
   • Take a sample from this composite soil mixture and put it in a new plastic bag. This is the sample that is tested.
   • Mark the plastic bag with the location name and date of collection.
   • Repeat steps 1–9 for each of your sample locations.
3. Testing the samples: There are a number of do-it-yourself kits that test for lead available on the market. Unfortunately, according to the EPA, these kits simply test for the presence of lead, and do not provide enough distinction between high and low levels of lead (http://www.epa.gov/lead/qa4.pdf). To accurately draw conclusions from your samples, we recommend that you do the following:
   • Use a home test kit to get a positive or negative reading on the lead content of your samples. These results will give you enough information to claim that lead is present.
   • For those samples that show positive indicators for lead, do a follow up check with a soil testing laboratory. There are laboratories associated with universities (for example, University of Massachusetts [http://www.umass.edu/plsoils/soiltest/lead1.htm]) as well as commercial laboratories (see http://www.ext.colostate.edu/PUBS/crops/00520.html for a list of some).

Variations

Other toxins such as mercury

Credits

Madeleine Disner; Jordan Liu; Sarah Stegman-Wise

Acid Rain and Aquatic Life

Objective

In this experiment you will test the effects of acidic water conditions on an aquatic environment containing algae, worms, snails, and plants.

Introduction

Acid rain occurs when pollution in the atmosphere (sulfur dioxide and nitrogen oxide) is chemically changed and absorbed by water droplets in clouds. When there is precipitation, the droplets fall to earth as rain, snow, or sleet. The polluting chemicals in the water droplets form an acid by combining with the hydrogen and oxygen in the water. These acidic droplets (pH <>

"Acid rain is a serious environmental problem that affects large parts of the US and Canada." (EPA, 2006) Acid rain accelerates weathering in carbonate rocks and accelerates building weathering. It also contributes to acidification of rivers, streams, and forest damage at high elevations (Wikipedia contributors, 2006).

What is an acid? An acidic solution will donate hydrogen ions and usually taste sour, like lemon juice. Acids are the opposite of bases, which accept hydrogen ions and usually feel slippery, like soapy water. How do you tell if something is an acid or a base? You use a chemical called an indicator, which changes in color when it goes from an acidic to basic solution. Indicators can be extracted from plant pigments, like red cabbage. If you want to learn how to make your own acid indicator, read the Science Buddies experiment Cabbage Chemistry.

In this experiment you will use an indicator that is concentrated on little strips of paper called "pH test strips". The color of the paper will indicate the pH of the solution you are measuring. Each one unit change in pH is a 10-fold change in the number of hydrogen ions in solution. Your pH test strips will come with a color chart that you can use to measure the pH of your vinegar solutions. This will give you a measurement of the acidity of your aquatic environments.

The goal of this experiment is to test the effects of acid rain on a simple aquatic ecosystem, consisting of small plants and animals. You will use household vinegar to create different solutions of various acidities. You will then observe the organisms in the experimental environment to determine the effects of acidic conditions on viability. To measure viability, you will count the number of living and non-living organisms in each experimental environment over time.

Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• acid rain
• pH
• environmental toxicity
• aquatic organisms
• aquatic environments

Questions

• How will acidic conditions affect an aquatic ecosystem?
• Will all of the organisms be affected similarly or differently?
• Which pH ranges will cause an effect?

Bibliography

• This project was adapted from the Duckweed Bio-Assay protocol from Cornell University:
  EIP, Date unknown. "Assessing Toxic Risk: Student Edition," Environmental Inquiry Program (EIP), Cornell University [accessed July 3, 2006]
  http://ei.cornell.edu/teacher/pdf/ATR/Protocol2.pdf
• This is a site just for kids that discusses acid rain:
  EPA, 2006. "Acid Rain Students Site," U.S. Environmental Protection Agency (EPA) [accessed July 3, 2006]
  http://www.epa.gov/acidrain/education/site_students/index.html
• Wikipedia contributors, 2006. "Acid precipitation," Wikipedia, The Free Encyclopedia [accessed July 3, 2006]
  http://en.wikipedia.org/w/index.php?title=Acid_precipitation

Materials and Equipment

• large bottle of white vinegar
• 3 gallons of distilled (bottled) water
• pH test strips (Alkalive pH Stix can be found at natural food pharmacies, or you can order pH test strips from a scientific supply company like Carolina Biological)
• measuring cups
• 6 large, reusable plastic containers with lids (6 cups / 48 oz, e.g. Glad or Zip-lock)
• permanent marker for labeling
• aquatic organisms: (should pick at least 2 plants and 2 animals)
  • small, cheap fish (minnows, feeder fish, or goldfish from pet shop or bait shop)
  • small pond snails (pond or aquarium supply store)
  • water fleas (Daphnia, available at aquarium supply stores)
  • live tubifex (available at aquarium supply stores, bait shops, or found in pond bottoms)
  • aquatic plants like duckweed or elodea (available at aquarium supply stores, ponds, or nurseries)
  • algae (spirulina, available at aquarium supply stores)

Experimental Procedure

1. Rinse each container thoroughly with water. Do not use soap because it can coat the plastic container and may be harmful to the organisms in your experiment. Label each container with a permanent marker.
2. Prepare the solutions for each container according to the data table below, one container for each experimental group. Use bottled water, not tap water, because it may contain harmful chemicals like chlorine or chloramine:

   Bowl	Water	Vinegar	Total Volume	pH	Observations
   1	1000 mL	0 mL	1000 mL
   2	900 mL	100 mL	1000 mL
   3	800 mL	200 mL	1000 mL
   4	700 mL	300 mL	1000 mL
   5	600 mL	400 mL	1000 mL
   6	500 mL	500 mL	1000 mL

3. Check the pH of each container with your pH test strips and record the data in your data table.
4. Evenly distribute the organisms into each container, being sure to add a mixture of plants (algae, duckweed, elodea) and animals (aquatic worms, snails, and small crustaceans). Write down the number of each type of organism you are adding to the containers. For example, "I added 10 snails,10 worms, and 20 duckweed plants to each container."
5. Observe the animals and write down observations in the data table. Continue your observations for a few hours, or overnight if necessary.
6. For each observation, count the number of organisms that are still alive for each different plant or animal. This is called a viability assay, because you are counting the number of things that are viable, or still living. For example, "At 3 PM there were 5 living snails, 2 living worms, and 7 living duckweed plants."
7. Make a graph of your results. On the left side (Y-axis) of the graph, make a viability scale by graphing the number of living organisms of each type. On the bottom (X-axis) of the graph make a scale of the pH of the water. Then make a line graph for each type of organism in your study. Did they respond similarly or differently to the changes in pH of your environment? What is the viable pH range for each organism? Which organisms are the most sensitive or the most resilient to changes in acidity?

Variations

• Another way to test the effect of acid rain on plants is to germinate seeds in acidic conditions. Try using your solutions to wet a paper towel in a baggie, sprinkle in some seeds, and place in a sunny window to see how many will sprout.
• You can also try watering a series of plants with neutral and acidic water. How well will plants grow when watered with "acid rain" compared to neutral water?
• Try these other Science Buddies experiments to test the effects of toxins on aquatic environments:
  • Heavy Metal
  • Something's Fishy About That Fertilizer

Credits

Sara Agee, Ph.D., Science Buddies