Add Stub # – Karan – Ozone-Monitoring Gardens

GRADE: 3, 8  |  TIME: 5 days; 20+ minutes / day


Students will plant milkweed to create an ozone-monitoring garden in spring or fall for the following year’s class. At the beginning of the school year (late summer or early fall) students will monitor the milkweed planted by the previous year’s class or observe other ozone–sensitive plants in the schoolyard to determine whether ozone levels got high enough to damage leaves.

Students will also explore ways in which some pollutants can be reduced by making models of cyclone hoppers and electrostatic precipitators, which collect particle pollution before it escapes from smokestacks. Ground-level ozone cannot be mitigated this way, so students will brainstorm ways to reduce ozone by changing things people do. Students will contribute to a nation-wide citizen science project by contributing data from the study of their ozone-monitoring garden.

Video credit: Neil Bromhall

DISCIPLINE: Life Sciences
TOPIC: Life Science, Natural Selection and Adaptations
GA STANDARDS(GSES): S4L2. Survival or Extinction of Organisms, a. Effects of Pollution on Habitats, b. Factors Leading to Extinction, c. Environmental Changes Effect on Ecosystems
NGSS CORE IDEA: LS4.C Adaptation
PRACTICE: Asking Question/Defining Problems, Developing & Using Models, Engaging in Argument from Evidence, Investigations, Planning & Carrying Out Investigations
CROSSCUTTING CONCEPTS: Cause and Effect, Patterns, Stability and Change, Systems and System Models


Georgia Standards of Excellence in Science (GSES):
NGSS Standard:


Georgia Performance Standards in Science

S3L2. Students will recognize the effects of pollution and humans on the environment.

  1. Explain the effects of pollution (such as littering) to the habitats of plants and animals.
  2. Identify ways to protect the environment.
  • Conservation of resources
  • Recycling of materials

 Next Generation Science Standards

3.LS4.C: Adaptation

For any particular environment, some kinds of organisms survive well, some survive less well, and some cannot survive at all. (3-LS4-3)

                NGSS Evidence Statement:
Other Standards:



Students will conduct an ozone bio-monitoring citizen science project and other investigations of air pollution in the vicinity of the school garden. Students will also create a classroom air-filtering garden and explore ways to reduce air pollution using an online interactive app.


Essential Questions

How can I estimate ozone air pollution levels by observing plants in the garden? What causes air pollution and how does it affect organisms and ecosystems? What can be done to reduce or mitigate air pollution?



Students will create particle pollution testers and make models of electrostatic precipitators and bag hoppers to investigate this form of air pollution.



Students will monitor ozone-sensitive plants for indications of this form of air pollution and report data as part of a citizen science project. Students will make Schönbein strips to detect the presence of ground-level ozone.



Students will explain the impact that air pollutants, and particularly ground-level

ozone, have on organisms and on an ecosystem. Then students will argue from evidence regarding whether the air is polluted or healthy.


Environmental Stewardship

Students will create an ozone monitoring garden using sensitive plant species to detect air pollution OR create an indoor air-purifying garden, using plants that hyper-accumulate toxins and chemicals.



A rubric is provided to assess student mastery of performance expectations.



Students may make a model of a cyclone hopper to see how it effective it may be at reducing particle pollution.


Students will make working models of an electrostatic precipitator and a cyclone hopper, to investigate how technology is able to reduce some air pollution. These featured lesson activities are from the Teach Engineering web site.



Day 1: 20 – 30 minutes

Show the class this slide presentation about how they can become air pollution scientists, doing real science in the schoolyard by monitoring sensitive plants for signs of pollution. Focus on how students can distinguish ozone damage from other types of leaf damage, such as the chewing of monarch caterpillars.

Elicit Questions


Day 4: 20 minutes

Ask students to explain what they know about air pollution and its effects on plants, animals and ecosystems and highlight the following points, as they are made by students.

  • Air pollution is a type of environmental change that affects entire ecosystems.
  • Ground-level ozone is formed when pollutants from vehicle tailpipes react with vapors and fumes in the air on hot, sunny days.
  • Ozone pollution hurts certain plants, including milkweed and many others.
  • Ozone-damaged plants are an indicator that pollution levels are also high enough to affect humans, animals, and ecosystems.
  • All organisms in an ecosystem are inter-connected.
  • Air pollution can change an ecosystem by forcing organisms to adapt or die.
  • If a plant cannot adapt quickly enough, it will die and be replaced by more pollution-tolerant species.
  • Changes in the types of plants in a community will result in changes in the types of animals in the community, because plants provide shelter and food for the animals.
  • If there are too few healthy milkweed plants and too many hungry monarch larvae (who only eat milkweed), the populations of both species will decline.
  • Ozone pollution levels can be lowered by reducing vehicles’ tailpipe emissions (i.e. more fuel-efficient vehicles, fewer miles driven, more carpooling, bus and bike riding, less time letting engines idle, etc.); reducing power plant emissions (by conserving energy and thus reducing demand for coal-fired electricity, cleaning smokestack emissions, etc.); and reducing release of vapors from volatile organic compounds (by patronizing “green” dry cleaners, fueling cars in the dark when gas fumes are less likely to evaporate, using low VOC paints, etc.).

Students should be able to argue from evidence whether ozone pollution is detected by their sensitive plants, whether that means there is or is not any air pollution in their area, and how air pollution can be prevented as well as partially mitigated.


A rubric is provided to assess student competency in conducting the field investigation; understanding of the concept of plants as bio-indicators of air pollution; and ability to articulate human impacts on the environment and how they can be mitigated. In addition, students should be able to explain that plants which are bio-indicators of pollution are more pollution-sensitive than other species. If their environment becomes polluted, they are less likely to survive than more pollution-tolerant species. Over time, pollution could have the effect of changing the both the plants and the animals that live in an ecosystem, because the shift to more pollution-tolerant plants will provide habitat and food for different animals.

8th grade Ozone assessment



Day 2: 45 – 60 minutes

Planting an Ozone Detecting Garden

Allow students to research, plan, and plant an ozone-detecting garden for next year’s class. (Milkweed will attract monarch butterflies, in addition to providing bio-indicators for an ozone-detecting garden). Milkweed can be planted in fall or spring for the following school year.


Day 3: 45 – 60 minutes

Field Investigation of Bio-Indicator Plants

Students should observe mature milkweed plants in late summer or early fall, or use an alternative bio-indicator plant that is also sensitive to ozone. (See Teacher Preparation section for details). Divide the class into teams of two. Each team will need a clipboard, pencil, and the Field Study Report form included with this lesson. Students will identify a bio-indicator plants and look for signs of leaf damage caused by ozone. After the field work, display team reports with corresponding photos and pressed leaves, so students can compare their results and get an overall picture of the health of milkweed plants in the ecosystem.


Day 4: 20 minutes

Encourage students to reflect on their research and field work to consider these questions: Does the condition of milkweed plants indicate that our air is polluted? (answer will vary depending on location and season) How do we know? (ozone data map from research and milkweed monitoring results) What are the first effects of ozone pollution on an ecosystem? (sensitive plants may show damage before other components of ecosystem) What effects cascade from the damage done to plants? (scarcity of a plant limits the population of animals that depend on that plant for food and affects every other organism connected in a food web, in some way) How could animals be affected by ozone pollution? (indirectly, as a result of damage to plants on which they depend, and directly, in terms of their own respiratory health) What are some ways that plants respond to pollution in an ecosystem? (pollution-tolerant species may out-compete the pollution-sensitive species and become dominant in the area) What are some ways that animals may respond to pollution in an ecosystem? (migration, change in diet, increased competition for limited resources, starvation/decline in population)


Day 4: 20 minutes

Making Models to Demonstrate Electrostatic Precipitators and Cyclone Hoppers

Students should work in pairs to make models of electrostatic precipitators by rubbing balloons against hair (to generate static electricity) and then collecting dried oregano, representing particle pollutants, by holding the balloons above the ground herb. Next, students can make models of cyclone hoppers by each applying petroleum jelly to the inside of a small paper cup (to represent a smokestack equipped with a cyclone hopper), sticking a sharpened pencil into the bottom of the cup as a handle, sprinkling oregano (particle pollutants) into the bottom of the cup, and spinning the cup to collect pollutants on the sides by centrifugal force. (For more information on these learning activities, check out this lesson from the Teach Engineering web site: Pollution Solutions). Ozone is invisible and cannot be collected and removed as easily as particle pollution, so it is important to prevent it from being formed in the first place. Ask students to brainstorm ideas for reducing ozone formation. (Ideas can be found at the Wisconsin Partners for Clean Air web site).


Grow plants in containers in the classroom, to mitigate the effects of airborne toxins. Indoor air pollution can harm human health just as outdoor air pollution can. Ask students to assess the classroom to see which building materials and furnishings could be releasing airborne toxins, according to the NASA Clean Air Study. Then select plants that have the ability to remove toxins from the air as they respire (breathe), and grow those species in pots near the best light.

Supplies and Prep

Teacher Preparation Ground-level ozone is highest in summer when heat contributes to the formation of this pollutant. Therefore late summer or early fall (before frost) are the best times to find ozone leaf damage on sensitive plants (so-called bio-indicators), after ozone levels have been highest. Milkweed seeds can be planted in fall or spring and will grow throughout the summer until first frost. Fall-planted seeds will experience freeze damage that will help them germinate in spring. Spring-planted seeds may need to be scarified with sandpaper in order to grow. If milkweed seeds were not previously planted in time for this activity, mature milkweed plants may be available from native plant societies, nurseries, or master gardener plant sales. Plant milkweed species that are native to your area. See Monarch Watch’s list of native milkweed species: http://monarchwatch.org/bring-back-the-monarchs/milkweeds-by-state/. If neither milkweed seeds nor plants are available, the class may select another sensitive species to monitor in fall, based on what plants are found in the garden or schoolyard. Among suitable species are choke cherry, black cherry, tulip tree, sycamore, dogbane, coneflower, flowering dogwood, and blackberry. For more information, refer to Using Sensitive Plants as Bio Indicators of Ground Level Ozone Air Pollution. One misconception students may have is related to confusion between stratospheric (upper level) and tropospheric (ground level) ozone. It should be clarified that ozone in the stratosphere has the positive effect of blocking harmful ultraviolet (UV) rays from the sun. And ozone does not naturally occur at harmful levels in the troposphere (at ground level). However, on hot sunny days ozone can be formed near ground-level when nitrogen oxides from combustion engines and fumes from fossil fuels mixed. (More can be found about this topic at the Wisconsin Environmental Education web site). Additional Resources: Using Sensitive Plants as Bio Indicators of Ground Level Ozone Air Pollution  http://www.handsontheland.org/monitoring/projects/ozone/implementation_guide.pdf   Bio-indicator Monitoring slide show http://dnr.wi.gov/org/caer/ce/eek/earth/field/biomon.htm   Sources of indoor airborne toxins and plants that can remove them from the air http://www.denverplants.com/foliage/html/CleanAir3.htm   Directions for planting an ozone garden http://aura.gsfc.nasa.gov/outreach/garden_getinvolved.html   Distinguishing ozone damage from other types of leaf damage http://dnr.wi.gov/org/caer/ce/eek/earth/field/milkweed/slideshowindex.htm   Who eats milkweed? http://www.monarchwatch.org/milkweed/damage.html   Interactive online training to estimate percentage ozone damage of a leaf http://www.nature.nps.gov/air/edu/O3Training/index.cfm   How to submit a leaf damage photo to NASA for analysis http://aura.gsfc.nasa.gov/outreach/garden_getinvolved.html  

Environmental Stewardship

Contribute data from your school’s ozone monitoring project to a national database, as part of an important citizen science research project. The Hands on the Land web site provides the protocol and details for data submission.

STEM Connections

Students are engaged in STEM learning as this lesson integrates math (data collection and analysis) with science (observation and field investigation). Technology can also be integrated if students take photographs of leaves to evaluate damage. An engineering activity is included to engage students in designing possible solutions for air pollution.


Small Group Learning Activity:
Individual Learning Activity:

Teaching Tips

Milkweed can be planted in fall or spring. Do the field investigation in fall. Leaves that have over-summered are more likely to ozone leaf damage, because ozone levels are highest in summer.

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