The water quality in urban waterways is continuing to decline due to the increased pollutants, toxins, sunlight intensity, and varying temperatures. These factors are known to affect the dissolved oxygen levels found in these waterways. The thrust of this project is to look at the affect of sunlight intensity on the amounts of dissolved oxygen in the Delaware and Raritan Canal and Lake Carnegie, running through Princeton, New Jersey.
 
Question: 

How does the intensity of sunlight affect the levels of dissolved oxygen in the Delaware and Raritan Canal and Lake Carnegie?

Hypothesis:

The amount of sunlight on the water surface of the canal and lake has a direct effect on the amount of dissolved oxygen found in the water.  When there is direct sunlight on the water, the levels of dissolved oxygen increase. The levels of dissolved oxygen will remain the same or decrease when not in direct sunlight.

Testing the Hypothesis:

The hypothesis will be tested using CHEMets water test kits.  Two areas in the canal and two areas in the lake will serve as test sites.  The first area in the canal will be one of direct sunlight at mile marker 28 on the tow path.  The second area will be an area that is shaded (under the stationary railroad bridge).  The first area in the lake is a shaded finger of the lake where the water is stagnant.  This area is heavily shaded due to dense canopy.  The second area in the lake is off of the floating boat dock in direct sunlight. Testing will occur mid-morning and early evening.  Charts and graphs will be made from both areas in order to make comparison.
 
Introduction :

Water is a molecule made of two hydrogen atoms and one oxygen atom ( H₂O). Mixed in with water molecules of any body of water are molecules of oxygen gas (O₂) that have dissolved in the water. Dissolved oxygen (D.O.) refers to the volume of oxygen contained in water.  There are two main sources of dissolved oxygen in the water; the atmosphere and photosynthesis.  In the atmosphere, one out of every five molecules in every million molecules are oxygen. Oxygen enters the water by photosynthesis and by the exchange of oxygen across the air-water surface. The amount of oxygen contained in the water depends on the water temperature, salt content, and altitude. When the body of water being tested is at a higher altitude, the levels of D.O. will be lower. Colder water holds more oxygen than warm water.  Freshwater contains more oxygen than saltwater. Dissolved oxygen in water is measured in parts per million (ppm), which is the number of oxygen molecules (O₂) per million total molecules of water. Oxygen is vital for all living organisms in the water.  Dissolved oxygen levels lower than 3 parts per million (ppm) are stressful to most aquatic organisms.  Fish can not live in water with levels below 2 or 1 ppm.  Fish growth and activity require 5 to 6 ppm of dissolved oxygen.  During the day, aquatic plants cause a D.O. increase in the water where they live.  Without light, the reverse is said to be true and there is usually a decrease in 0₂.  Once absorbed, oxygen is either incorporated throughout the waterway by internal currents or is released from the system.  Flowing water tends to have higher dissolved oxygen levels than stagnant water because of the movement of the water at the air-water surface.  In flowing water, oxygen-rich water at the top is continually being replaced by water with less oxygen due to turbulence. More opportunity for transfer of oxygen across the air-water surface will occur. Stagnant water undergoes less internal mixing, the top layer of oxygen-rich water is likely to stay at the top, resulting in lower dissolved oxygen levels throughout the water body.
 
Procedure:

Procedure comes from CHEMets.

1.  Immerse the snapper (sample collector) into the test site.
2.  An ampoule, tapered end first was placed into the snapper.
3.  Press down on the ampoule to snap the tip allowing water from the snapper to be drawn into
     the ampoule and mix with the contents (indigo carmine).
4.  Remove the ampoule from the snapper, and invert it several times, allowing the bubble
     to travel from end to end to mix the contents.
5.  Wait two minutes for full color development.
6.  Use the color chart (inside box) to determine the dissolved oxygen content of the sample by
     matching the filled CHEMet ampoule with the color bars on the chart.  The chart should be
     illuminated from above by a strong white light.  Be sure to place the CHEMet ampoule on
     both sides of a color bar before concluding that it gives the best match.

Charts and Graphs:
 

Dissolved Oxygen Levels in Lake Carnegie
 
 

Data:

Upon reviewing the data, the dissolved oxygen levels were found to be greater in the area of direct sunlight, on the lake and canal.  In addition, the data shows readings for D.O. were slightly higher in the p.m. test than in the a.m. test.   See the above graphs on the canal and lake testing sites.

Conclusion:

Information from the data suggests that the increase in dissolved oxygen levels may be caused by direct sunlight on the water.  However, other studies indicate that direct sunlight will decrease the amounts of dissolved oxygen in the water.  Further studies are recommended to verify that the sunlight was the direct cause of the increase in dissolved oxygen.

Transfer to Home Sites:

The group of teachers who produced this project plan to implement a similar project at their respective school sites.  A local water system will be chosen near each school site for data collection.  The information and data collected will be shared  between the Arizona classes and the North Carolina classes.  The students will then use this information to do problem solving and comparative studies between the desert ecosystem and the deciduous forest ecosystem.  These studies will link the students from the two regions, by using current technology  and to promote global awareness.

Extensions:

Other factors such as time of day, water temperature, water current, seasonal variances, air temperature, water depth, percentages of living organisms and weather are also known to affect dissolved oxygen levels.  Systematic testing of these variables can be performed to determine how viable their effects are on dissolved oxygen levels.  Testing of these variables can be performed in place of or in conjunction with sunlight.
 
National Science Standards:

Standard 1:
SCIENTIFIC INVESTIGATION - Students design and complete a scientific investigation in which they apply inquiry skills to extend their understanding of dissolved oxygen in their area.

Standard 2:
PHYSICAL SCIENCE - Students observe, measure, and calculate qualities of water samples taken from various locations to test dissolved oxygen levels.

Standard 3:
LIFE SCIENCE - Students will explain how the rate of environmental change can exceed the capacity of an organism to respond to change.  Students will describe the oxygen cycle as it relates to the local area.

Standard 4:
EARTH AND SPACE SCIENCE - Students will identify and analyze the benefits, and   consequences of high dissolved oxygen levels in water of the local area.  Students will explain how weather and climate effect dissolved oxygen levels.

Standard 5:
SCIENCE AND TECHNOLOGY - Students will describe how technology can help solve various dissolved oxygen levels (and their related problems) in the community.  Students will describe the effects of human behavior on the quality of water.

Standard 6:
NATURE OF SCIENCE - Students will refine a hypothesis based on an accumulation of data over time. Students will use graphs, equations, or other models to analyze the data collected.

Standard 7:
HABIT OF MIND - Students will use a variety of measurement tools to corroborate conclusions based on data collected.

Standard 8:
GLOBAL VIEW OF SCIENCE - Students will design models or research papers which will show the effects of various (& inadequate) levels of dissolved oxygen in water that can be found in various location. i.e. Industry, Agriculture, Suburbs, and Wetlands.

References:

Materials, encouragement, ideas, and support from GREEN and GLOBE.
Water quality educational resource links:
Materials specific to Arizona can be found at Arid Arizona.
Materials specific to North Carolina can be found at North Carolina Environmental Education Clearinghouse.
Some clip art images used in this web page came from Corel Corporation.

Glossary :
 
    ampoules - Cylindrical glass tubes for testing dissolved oxygen levels (contains indigo
    carmine)

    canal - Manmade waterway for transportation and commerce

    CHEMetrics - Company that manufactures dissolved oxygen testing kits

    colorimetric Analysis - Color scale to compare test sample

    dissolved oxygen - The oxygen freely available in water. Dissolved oxygen is vital to fish
    and other aquatic life. Traditionally, the level of dissolved oxygen has been accepted as the
    single most important indicator of a water body's ability to support desirable aquatic life.

    finger-lake - Geographic name given to extension of  lake

    hydrology - The science dealing with the properties, distribution, and circulation of water

    lake - Large body of water fed by stream, creek, brook, or spring

    photosynthesis - A process occurring in the cells of green plants and some micro-organisms
    in which solar energy is transformed into stored chemical energy.

    plankton - The passively floating or weakly swimming usually minute animal and plant life
    in a body of water

    ppm - Parts per million

    snapper - Sample collection jar

    stagnant - Without movement

    watershed - The land area that drains into a river, stream , or lake.

    zooplankton - Plankton composed of animals
 
 
Bibliography:

Aquatic Project Wild.  Western Association of Fish and Wildlife Agency. Bethesda, Maryland. 1992.

Bales, Roger & Martha Conklin, Carol Bylsma, Stacy Levowitz, Chris Gutman.  Global Learning and Observations to Benefit the Environment, Teachers Guide. Washington D.C. 1997.

Benchmarks for Science Literacy. Project 2061. Oxford University Press. New York, 1993.

Cole-Misch, Sally & Larry Price, David Schmidt. Source Book for Watershed Education. Kendall/Hunt Publishing Co., Dubuque, Iowa. 1996.

Goudie, Andrew. The Human Impact on the Natural Environment. The MIT Press, Cambridge, MA. 1994.

Mitchell, Mark K. & William B. Stapp. Field Manual for Water Quality Monitoring. Kendall/Hunt Publishing, Co., Dubuque, Iowa. 1996.

National Science Education Standards. National Academy Press. Washington D.C. 1996.

Roa, Michael L. Environmental Science Activities Kit. Center for Applied Research in Education. West Nyack, New York. 1993.

Stankorb, Sheri L. & William B. Stapp, Arjen E. J. Wals. Environmental Education for Empowerment. Kendall/Hunt Publishing Co., Dubuque, Iowa. 1996.
 
 

For more information or comments please send e-mail to:
bhcowan@aol.com
shigh@lomalinda.creighteld.k12.az.us
emcnabb@lomalinda.creighteld.k12.az.us
dstorto@lckennedy.creighteld.k12.az.us
btolber@papago.creighteld.k12.az.us