A-B1 2020 Dipierno

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Across
  1. 4. the presence in or introduction into the environment of a substance or thing that has harmful or poisonous effects.
  2. 5. a colorless, transparent, odorless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms.
  3. 6. Soil erosion is the displacement of the upper layer of soil; it is a form of soil degradation.
  4. 8. is a highly reactive gas composed of three oxygen atoms
  5. 10. the envelope of gases surrounding the earth or another planet.
  6. 12. the action of clearing a wide area of trees.
  7. 17. the layer of the earth's atmosphere above the troposphere, extending to about 32 miles (50 km) above the earth's surface (the lower boundary of the mesosphere).
  8. 18. the region of the earth's atmosphere above the stratosphere and below the thermosphere, between about 30 and 50 miles (50 and 80 km) in altitude.
  9. 21. the chemical element of atomic number 18, an inert gaseous element of the noble gas group.
  10. 22. occurs when a species' population exceeds the carrying capacity of its ecological niche.
  11. 23. the chemical element of atomic number 7, a colorless, odorless nonreactive gas that forms about 78 percent of the earth's atmosphere.
  12. 24. the lowest region of the atmosphere, extending from the earth's surface to a height of about 3.7–6.2 miles (6–10 km), which is the lower boundary of the stratosphere.
  13. 25. a gas that contributes to the greenhouse effect by absorbing infrared radiation, e.g., carbon dioxide and chlorofluorocarbons.
Down
  1. 1. a measure of the warmth or coldness of an object or substance with reference to some standard value.
  2. 2. a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.
  3. 3. a colorless, odorless gas produced by burning carbon and organic compounds and by respiration.
  4. 7. the state of the atmosphere at a place and time as regards heat, dryness, sunshine, wind, rain, etc.
  5. 9. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice.
  6. 11. a change in global or regional climate patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.
  7. 13. a colorless, odorless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air.
  8. 14. the outermost region of a planet's atmosphere.
  9. 15. a colorless, odorless flammable gas which is the main constituent of natural gas.
  10. 16. the layer of the earth's atmosphere that contains a high concentration of ions and free electrons and is able to reflect radio waves
  11. 19. the region of the atmosphere above the mesosphere and below the height at which the atmosphere ceases to have the properties of a continuous medium.
  12. 20. the degree to which the ambient air is pollution-free, assessed by measuring a number of indicators of pollution.