Chemical Pollution - the introduction of toxic substances into an ecosystem, e.g., acid rain, contamination of water supplies by pesticides. Thermal Pollution - varying temperatures above or below the normal condition, e.g., power plant turbine heated water. Organic Pollution - oversupplying an ecosystem with nutrients, e.g., fertilizer inflow. Ecological Pollution - stresses ordinarily created by natural processes. The first three are dominantly caused by humans, although there are rare cases where natural process can cause them.
Ecological pollution is typically natural, although there are cases where it is caused by humans.
Pass out the Pollutant Information Sheets. Review each kind of pollutant with the students. Ask students to put each kind into the four categories. Talk about how some of these can fit into more than one of the four categories. Color code each of the four categories of pollutants with a different color of the construction paper.