1 / 12

THE OZONE LAYER

THE OZONE LAYER. A. OZONE in the Atmosphere. Tropospheric Ozone = “BAD” Stratosphere Ozone = “GOOD” defense against UV radiation Contains 97% of O3 Essential to life as we know it Mainly formed at Tropics BUT majority is carried to poles by convection currents. B. The Chemistry.

chantale-irwin
Download Presentation

THE OZONE LAYER

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE OZONE LAYER

  2. A. OZONE in the Atmosphere • Tropospheric Ozone = “BAD” • Stratosphere Ozone = “GOOD” • defense against UV radiation • Contains 97% of O3 • Essential to life as we know it • Mainly formed at Tropics BUT majority is carried to poles by convection currents

  3. B. The Chemistry • Formation: • O2 + UV (sunlight) --> O + O (atomic oxygen) • O (atomic) + O2 (molecular) --> O3 (ozone) • Reverse reaction also occurs UV hitting ozone causing it to form O + O2

  4. C. Causes of Ozone Depletion • Major contributors are compounds that release: • Chlorine • Bromine • Flourine • Measurements indicate that over antarctica ozone has decreased about 60% since late 70’s

  5. 3. Main Culprits • Chlorofluorocarbons - CFC’s • First made in 1920’s as refrigerants, coolants, aerosol propellants, industrial solvents, foam and insulation products, cans of hair spray • Largest source is leakage from air conditioning • Average resident time in environment = 200 years (100 in stratosphere) • Chlorofluorocarbons are also greenhouse gases • 1970s, Roland & Molina research showed the negative effects of CFCs on stratospheric ozone

  6. CFCs released into atmosphere make there way to atmosphere • Intense UV radiation breaks the CFC molecules apart and releases chlorine atoms • Cl + O3 --> ClO + O2 • ClO also reacts with Ozone and becomes a chain reaction...(ClO + O3 --> Cl + 2O2)

  7. Bromine • 50x more effective then Cl in destroying ozone • Responsible for 20% of problem • Found in Halons (type of CFCs) which are used in fire extinguishers • Methyl bromide used in fumigation and agriculture • Naturally released from phytoplankton and biomass burning

  8. D. Seasonal Effects • In winter months, ClO is concentrated in ice crystals that form in and around the antarctic polar vortex • In early Spring, returning warmth frees the Cl from the ClO where it destroys more Ozone • ClO + O --> Cl + O2 • Ozone Loss is greatest in SPRING • Chlorine acts as catalysts to help break down more O3

  9. E. Health and Environmental Effects • Excess UV in lower atmosphere causes great damage to cells of living organisms • Sunburns and damage to skin • Skin Cancer • Eye cataracts • Weakening Immune System • Mutations in DNA structure • Plant photosynthesis is greatly reduced due to cellular damage • Reduction in crop production • Reduction in phytoplankton and thus effects on food webs • Animals (fish, amphibians) lacking protective fur or scaly skin are also harmed directly

  10. F. Reduction • Most developing countries have already phased out ozone-destroying • Alternatives to CFCs and Halons • Replace Chlorine with Hydrogen • He, Ammonia, propane, & butane can be used as coolant • Use pump sprays vs. Aerosol • Support legislation that reduces destroying products

  11. G. Legislation • The Montreal Protocol in 1987 • Greatest environmental success stories and signed by 146 nations • Proof that global problems can be solved by combination of international cooperation and scientific advances • Require nations to phase out the use of ozone-depleting chemicals (i.e. CFCs) in favor of less harmful alternatives • Since Protocol depleting chemicals have decreased 95%, however, still several nations rely on CFCs

  12. H. Test Tips • Students often confuse issues of Ozone Depletion and Global Climate Change • Mainly because ozone-depleting chemicals are also greenhouse gases • MAKE SURE TO KEEP SEPARATE: • Ozone-depletion DOES NOT CAUSE WARMING... • Increases UV radiation resulting in increased rates of cancer for humans & loss of photosynthetic productivity....

More Related