HOW MUCH ATRAZINE?
 
Karol McChesney
East Elementary
Belleville, Kansas
 
Overview:
Atrazine is one of the most widely used herbicides in the U.S. Kansas farmers apply it annually to approximately 1.2 million acres of corn and to 2 million acres of sorghum. Recently, the EPA set the drinking water standard for atrazine to 3 ppb (parts per billion). This lesson demonstrates that 3 ppb is an extremely minimal amount. It also will help pupils to easily understand the ratio.
 
Grades Levels: 3-12
 
Time Needed: 1 class period
 
Geographic Theme:
People and Their Environment
 
Kansas Social Studies Standard for Benchmark, Grade Levels 12-K:
The student will understand the connections among people, places, and environments in the local school and community, Kansas and its surrounding states, the U.S. and its region, and the world.
 
National Geography Standard, Grades K-12:
#16 The geographically informed person knows and understands the changes that occur in the meaning, use, distribution, and importance of resources. 
 
Outcome:
  1. Students will know that atrazine is a valuable herbicide.
  2. Students will know that certain environmental risks are minimal when using atrazine properly.
Performance Objective:
  1. The student will demonstrate the permissible amount of atrazine allowed in Kansas drinking water.
Vocabulary:
atrazine  herbicide 
ppb  EPA 
Tuttle Reservoir  Clorox bleach 

Materials:
Procedure:
 1. Explain that Tuttle Reservoir and other bodies of water in Kansas sometimes have high levels of atrazine recorded during the growing season due to runoff from rainfall and irrigation. 
 2. Point out that the EPA originally set the standard for atrazine concentration in drinking water at 150 ppb. Because atrazine concentrations in water supplies were far below this figure, it was not considered a problem. But now recently, they have reduced the standard for atrazine to 3 ppb. 
 3. Explain that students will demonstrate the ratio of atrazine to water that is considered a safe amount. 
 4. Have student dip the small end of the toothpick in red food coloring (which represents the herbicide, atrazine). 
 5. Next, have student wipe that end of toothpick on paper towel. 
 6. Finally, have student immerse the red tip of toothpick in the 5 gallon bucket of water. 

Sample discussion questions:
Did the water turn red?
Do you think there was a great deal or a teeny amount of “atrazine” in the water?
What are some other words to describe the amount of atrazine?
(microscopic, little, minute, infinitesimal, tiny)
If that had been Clorox, would you have been able to taste it in the bucket of water? Would it have harmed you?
How much Clorox do you think is dumped in the city swimming pool?
Do you think that 3 ppb of atrazine in water will harm you?

 
Assessment:
Teacher observation of student participation.
 
Extension:
Have students predict how many drops of water they can put in one tablespoon. Provide them with eyedroppers, standard measuring tablespoons and water. Have students keep track of the number of drops of water they successfully drop in until the tablespoon no longer holds anymore.
(APPROXIMATELY 500 DROPS OF WATER WILL FILL ONE TABLESPOON)
 
The following chart was used to figure the amount of atrazine allowed in drinking water:
500 drops water in one tablespoon
8000 drops water in one cup
16,000 drops water in one pint
128,000 drops water in one gallon
640,000 drops water in five gallons
12,800,000 drops water in 100 gallons
128,000,000 drops water in 1000 gallons
1, 280,000,000 drops water in 10, 000 gallons
 
So, approximately three drops of atrazine are allowed in 10,000 gallons of water! Students could imagine a 10,000 gallon capacity city water tower with three drops of atrazine dropped in to understand the ratio.  
 
Resources:

Cooperative Extension Service, KSU, (February, 1992). Questions & Answers about Atrazine. Manhattan, Kansas.

 
 
FHSU Geoscience | Kansas Geographic Alliance
National Geographic Society | Kansas Water Office
Fort Hays State University | Kansas State University
e-mail: pphillip@fhsu.edu