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Nitrate Lab: Environmental Science

Nitrates (NO3)

Nitrates (NO3-) are a chemical compounds made from the elements nitrogen and

oxygen. Nitrogen is needed by all plants and animals in order to make proteins (thebuilding blocks of cells), to grow, and to reproduce.

Nitrogen is very common and found in many forms in the environment. Nitrogen ismost abundant in its molecular form (N2

-) which makes up 79 percent of the air we

breathe. In this form, nitrogen is useless to most plants and animals. Blue-greenbacteria, the most common algae found in algae blooms, can convert nitrogen (N2

-)

into other compounds such as ammonia (NH3) and nitrates (NO3-) which can be used

by plants in order grow. Nitrogen is a common ingredient found in most fertilizers.

Animals get the nitrogen they need by eating plants or by eating animals that haveeaten plants. Animal digestive systems break down plant proteins to form nitrogen

compounds which can be used to form the proteins they need. Much nitrogen isreleased in the wastes produced by animals. Ducks and geese contribute a heavyload of nitrogen (from excrement) in areas where they are plentiful.

When plants and animals die, proteins are broken down by bacteria forming

ammonia (NH3). Ammonia is broken down by other bacteria to form nitrite (NO2-).

Ammonia and nitrite are both poisonous to animals. Nitrite is then consumed by a

third type of bacteria which forms nitrates (NO3-). Nitrates can then be used by

plants in order to grow. This recycling of nitrogen through the environment is called

the nitrogen cycle.

Nitrate is a major ingredient in most fertilizers. When it rains, varying amounts of 

nitrates wash from farmlands and lawns into nearby streams. Nitrates can also enterstreams from animal wastes, leaking septic systems, and sewage.

Nitrate (NO3-) can be harmful to humans. It is broken down in our intestines

becoming nitrite (NO2-). Nitrite affects the ability of red blood cells to carry oxygen.

If infants consume water high in nitrite/nitrates, they may suffer from a serious

condition called methemoglobinemia or "blue baby" disease. Wells contaminated bysewage or agricultural run off are a major concern in some areas. Nitrites can also

cause serious illnesses in fish.

How to Test for Nitrates

Nitrates can be tested for in a variety of ways. Most tests involve a colormetricchange. Some kits measure this change through electronic means, others use a

simple color wheel comparator. Testing procedures vary for different levels of nitrates. Suspected nitrate nitorgen in the 0 to 1 mg/liter range requires one test

while a high range test 0-10 mg/liter Nitrate test is necessary for water with highernitrate levels.

Listed below are the instructions for measuring nitrate (NO3-) levels between 0-50

mg/l using a Model NI-11 test kit manufactured by Hach Co.

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1. Rinse a color viewing tube several times with the water to be tested; then fillto the 5-ml mark.

2. Open one NitraVer 5 Nitrate Reagent packet. Add the contents of the packetto the tube containing the water sample to be tested. Stopper the tube and

shake it vigorously for exactly one minute. An amber color will develop if nitrate is present.

3. Allow the prepared sample to set undisturbed for one minute.4. Place the amber colored disk into the black comparator box.5. After the sample has set undisturbed for one minute, place the tube into the

top right opening of the black comparator box.

6. Fill the other viewing tube to the 5-ml mark with some of the original watersample and place it into the top left opening of the black comparator box.

7. Hold the comparator box up to a light source and view through the openingsin the front. (Use a white sheet of paper for a background.) Rotate the color

disk in the comparator box until the two colors match. Read the mg/l nitratenitrogen (N) through the scale window.

8. Test results can be converted from mg/l nitrate nitrogen (N) to mg/l nitrate

(NO3-) by multiplying the scale reading by 4.4.

9. When finished, pour the used chemicals into the waste collection container.

Clean the equipment and return it to its proper place.

Procedure:1. Follow directions given in your test kit to test tap water for nitrates.

2. Follow directions given in your test kit to test tap water for phosphates.

Questions:

1. What was the concentration of nitrates in your sample?

2. What is the movement of nitrogen through the environment called?

3. What are some ways that nitrates can enter streams?