OZONE DEPLETION
- What is Ozone (O3)?
- 0.0008% of all gases in the atmosphere
- 10% in the troposphere, 90% in stratosphere
- stratosphere O3 is naturally produced and protects the Earth
- filters out 99% of UV
- UV comprises 2% of the incoming solar radiation
- the wavelength 320 - 400nm is UVA (harmless)
- 200 - 280nm is UVC (lethal but is absorbed ozone)
- 280 - 320 nm is UVB (lethal)
- regulates planetary temperature
- absorbs incoming UV light and warms the stratosphere
- caps the Earths climate system below the troposphere
- Where does it come from?
- Ozone is produced by reactions with incoming solar radiation
- When solar radiation in the wavelength of 180 - 240 nm enters the stratosphere, it is absorbed by O2
- This process splits the O2 into O + O
- The two oxygen atoms recombine with an oxygen molecule to form O3
- Where does it go?
- Ozone can be depleted naturally
- When solar radiation in the wavelength of 200 - 320 nm enters the stratosphere, it is absorbed by O3
- This process splits the O3 into O2 + O
- This process releases heat (exothermic), which keeps the stratosphere warm
- Ozone can also be depleted by naturally occurring gases in the stratosphere
- Oxides of nitrogen, chlorine, and hydrogen
- These gases help balance the amount of ozone created
- Ozone can also be depleted by man
- Chlorofluorocarbons (CFC's) contain chlorine
- used as propellants in spray cans, styrofoam, cleaning solvents, coolants
- Industrial and agricultural sources
- methane and nitrogen (NO2)
- Health Effects
- skin cancer (10% increase by 2060)
- cataracts
- UV-B lowers immune system response(?)
- Effects on Ecosystems
- Terrestrial
- plant lesions and disease
- Aquatic
- the phytoplankton problem
- Macroalgae and seagrasses
- impact on primary and secondary consumers ranging from zooplankton to fish
- declines in both amphibians and corals
- Effects on Biogeochemical Cycles
- changes
in UV penetration into aquatic environments, nutrient cycles, carbon
capture and storage in the aquatic and terrestrial environment, and the
biosphere-atmosphere exchange of greenhouse and chemically-active gases
such as CO2
- Materials Damage
- An
increase in solar UV may result in shortening of useful lifetimes of
plastics and increase the cost of using plastics, particularly in
building
applications
- GEE....IS THERE ANY GOOD NEWS?
- In
1987 24 countries signed the Montreal Protocol, which is a treaty that
is supposed to reduce the emissions of ozone-depleting chemicals
- Followed by the London Agreement (1990) that added 36 countries, and by the Copenhagen Agreement in 1992
- Since 1994, there has been a reduction in chlorine in troposphere
- Global warming link?