Ozone Depletion and Acid Deposition

• Ozone is the 3 oxygen molecule in the stratosphere that absorbs UV radiation and protects the Earth’s surface from the mutating effects of the radiation
• Causes of Ozone Depletion

  • Chlorine or Bromine containing compounds, UV radiation releases Cl or Br ions, Cl and Br ions destroy Ozone
• As algae evolved in oceans, they released O2 into the atmosphere (Gia Hypothesis)
• How Ozone Depletion Takes Place

  Rowland and Molina (1974), Chlorine atoms are removed from CFCl3 by UV light, CFCl3 + UV -> CFCl2 + Cl, Cl + O3 -> ClO + O2, 2ClO + UV -> 2Cl + O2
• Each chlorine atom can convert up to 100,000 O3 molecules to O2 before it finally combines with hydrogen to make HCl and it rains down
• Ozone depletion in the 80’s should cause 12 million people to develop skin issues
• Less Ozone results in more UV radiation (mutagen and carcinogen) reaching southern oceans
• How Does Ozone Absorb UV Light?

  • Man-made chemicals known as Halons (Chlorine and Bromine) containing chemicals, Chlorofluorocarbons (CFC’s) containing Chlorine (Cl) used in aerosol cans, cooling agents in air conditioners and refrigerators (Freon)
• How Ozone Depletion Takes Place

  Cl and Br ions are not degraded by solar radiation, each ion destroys many O3 molecules
• How Is Ozone Formed?

  • O2 + UV -> O + O, O + O2 -> O3
• Chlorine acts as a catalyst in the reaction because it helps it, but is not used up in the reaction
• The thinning 15-20% of the ozone layer over Antarctica is known as the Ozone Hole
• Ecological Effects of Ozone Depletion

  • Increased high energy UV radiation reaching the earth’s surface, Adverse effects on Larval development
• Effects of Acid Deposition

  • Acid Lakes
  • Physiological Tolerance/Abiotic factors
  • Acid Lake “Sweetening”
• 1987 - Montreal Protocol
• Sources of Pollutants

  • SO2 + H2O ---> H2SO4 (Sulfuric acid)
  • NO2 + H2O ---> HNO3 (Nitric acid)
• Controlling Acid Deposition

  • Coal Burning is the main cause
  • Cap and Trade economic approach as part of 1990 Clean Air law
  • Scrubbers and coal washing to remove sulfur (clean coal technologies)
  • Coal is being phased out by natural gas (no sulfur) and renewables
• Ecological Effects of Ozone Depletion

  • Increased high energy UV radiation reaching the earth’s surface
  • Adverse effects on Larval development
• Acidic soils cause minerals to be leached (washed out) from the soil
• CFC production has fallen 77% between 1988 and 1995
• Bioaccumulation
• 1978 - U.S. banned use of CFC’s
• Chlorine levels have already begun to decrease and should be back to safe levels by 2045
• Montreal Protocol

  • 150 nations signed agreement
  • Agreed to cut emissions by 50% between 1989 and 2000
• Larvae (baby ocean creatures) will decline
• Measuring Acidity

  • pH scale (log scale)
  • Normal rainwater (pH of 5-6)
  • Acid rain has a pH between 3-4
• Terrestrial Organisms

  • External damage to bark & leaves
  • Little resistance to pests
  • Lower rates of photosynthesis
• Acid Rain is a Regional Issue
• Effects of Ozone Depletion

  • Ozone depletion in the 80s should cause 12 million people to develop skin cancer in their lifetime
  • Glaucoma (blindness) increases
• Results in a Ca2+ deficient food chain (thinning eggshells of local birds)
• Acidic soils cause toxic Heavy metals ionize in soil and are taken up by plants (metal toxicity)
• Gasoline used in personal automobiles does not release SOx
• Acid deposition


  The process by which acid compounds (H2SO4 or HNO3) condense out of the atmosphere in the form of rain, snow or fog
• Impact of acidic snow melt in a shallow fresh water lake in the spring

  Changes abiotic factor, physiological impact on base (aquatic insects), impact on Osprey populations in the adjacent forest, economic impact
• Acid deposition impacts aquatic (fresh) water ecosystems


  Alters the abiotic conditions of the system
• The Clean Air Act of 1990 focused on controlling Sulfur and Nitrogen emissions by regulating stationary sources of these pollutants
• Lake with granite bedrock is more prone to acidification than one with limestone bedrock


  Reason
• Clean air technology industry required to install when burning fossil fuels
• Acid deposition weakens trees in the forest
• Forests are a natural resource that we depend on economically