Across
- 2. methods to measure the types and amounts of chemicals in water
- 4. any type of substance that is in air and makes it unsafe to breathe
- 10. a measure of how clean the air is
- 11. water that has been used by people
- 13. a facility that cleans wastewater before being returned to the environment
- 15. the color of the leaves of most plants
- 16. an artificial or natural substance that contaminates air, water, or soil
- 17. a gas found in air
- 19. play well
- 20. to save or protect
- 21. water stored in the spaces between materials beneath Earth's surface
- 22. happens when fog and smoke are combined
Down
- 1. water that is usable for humans for things such as drinking and cleaning
- 3. fresh water found in rivers, streams and lakes
- 5. materials that occur in nature than can be used by people
- 6. gas made by plants that is breathed by people and animals
- 7. tiny organisms that break down matter
- 8. the process of cleaning infection from a material
- 9. an energy source that does not release pollutants when it is used
- 11. the presence of harmful substances in water
- 12. a want or a need
- 14. rapid growth of microscopic algae in a body of water
- 18. green substance in plants