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Trees and Air Quality

The following activity can be used in combination with EEK! articles A Tree's True Color and with Global Warming is Hot Stuff!. You can also use it with another activity in the teacher pages entitled "How to Plant a Tree".

[Ash Tree]

Subject
math, science. language arts, social studies

Grade Level: 4-9

Objectives
Students will be able to describe the ways in which trees benefit air quality and determine how to landscape a home with trees to decease energy use.

Materials
Drawing of students' residence.

Background
Trees are much more than something pretty in your yard. They are important for a number of reasons, including:

  • Reducing run-off of water
  • Providing habitat for wildlife
  • Providing people with forest products
  • Providing a recreation site
  • Economic value
  • Aesthetic value

In addition, trees and plants have a great impact on our air quality. Trees act like filters. The leaves capture particulates like dust, soot, and pollen and remove them from the air. They also remove and store carbon and reduce our need for energy.

Trees act like a carbon warehouse. In the process of photosynthesis, plants remove carbon dioxide from the air and release oxygen. A healthy tree uses over 20 lbs. of carbon dioxide each year. The carbon is stored in the tree (wood is about 45 percent carbon) and the oxygen is released back into the atmosphere. Carbon dioxide is the most common greenhouse gas. Other greenhouse gases include a variety of nitrogen oxides, methane, and chlorofluorcarbons (CFCs).

Trees are outdoor air conditioners. They provide a natural way to shade and cool your house in summer and can shield your home from the cold winds of winter. A person can save energy by landscaping with trees. Deciduous trees planted on the south, west, and east will protect your home from the direct rays of the sun in summer. In winter, without their leaves, they allow most of the sun's energy to reach the house. Conifers to the north and west can block cold winter winds. This reduces consumption of energy to heat your home.

A successful urban tree program can also impact whole communities. Cities are often 10 degrees (Fahrenheit) warmer than suburbs, partially due to the "heat island effect" cause by concrete, steel, and asphalt. The planting and care of trees can minimize this phenomenon and greatly reduce energy consumption.

Procedure

1.Testing for particulate removal. Students should draw a map to scale of their yard or school site and locate any trees on the map. Using a damp white cloth they should carefully wipe a leaf from each tree. Is the cloth dirty? Can you tell what material is on the cloth? Using your map, record which tree had the most dirt on the cloth. What was the source of the material? What will happen to the particulates that be came trapped on the leaf in a week? Or month?

2. Using the same map determine which trees assist in saving energy. Students should make several observations on sunny or windy days. Which trees provide shade in the summer? Students should consider the changing angle of the sun's rays during the seasons? Which trees block winter wind?

3. Draw in locations where you would plant trees to save energy. What types of trees would you plant? Students should consider a variety offactors including distance to buildings, soil drainage, power and gas lines.

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