Ozone depletion and CFCs
In 1974, a controversial hypothesis was proposed, suggesting that
chlorofluorocarbons (CFCs) deplete stratospheric ozone. This hypothesis was based on the observations that CFCs are extremely stable in the lower atmosphere, they readily migrate to the stratosphere, where they can be broken down by intense UV radiation, and the freed chlorine free radical can then catalyze the destruction of stratospheric ozone (e.g., CFCl2):
CFCl3 + light ------> Cl●
+
CFCl2
(1)
Cl● + O3 ------> ClO +
O2 (2)
ClO
+ O3 ------> Cl●
+
2O2 (3)
Ozone depletion thus results in significantly increased levels of biologically damaging and effects on human health, including sunburn, skin cancer, and cataracts, as increased UV solar radiation reaches the earth’s surface.
Emission and uses of ozone-depleting chemicals
CFCs and other ozone destroyers have been widely used as aerosol propellants, refrigerants, blowing agents, cleaning solvents, and fire extinguishing agents. CFCs are thought to be responsible for most ozone depletion. Though restricted for use as aerosol propellants, CFCs are still widely used as refrigerants, and this use shows an upward trend.
The Antarctic ozone hole
Much of the world’s stratospheric ozone is produced near the equator, However, air circulation patterns produce the greatest concentration of ozone in the polar regions. The term ozone hole refers to springtime thinning of the ozone layer above Antarctica; such thinning has been observed since the 1970s.
An Arctic ozone hole?
The ozone-deficient air masses that form over the North Pole are more mobile than those over Antarctica, thus threatening some densely populated regions of northern continents.
Tropical and midl-atitude ozone depletion
Conditions conducive to ozone depletion may occur in the tropics and mid-latitudes. Volcanic eruptions in tropical latitudes may contribute sulphur-based aerosols which trigger the necessary reactions.
Environmental effects
The potential environmental effects of ozone depletion include damage to aquatic and terrestrial food chains and a variety of human health effects. Increased UVB exposure resulting from ozone destruction can educe primary productivity in marine food chains, thus affecting all trophic levels and perhaps disrupting the global carbon cycle. Agricultural harvests could be negatively affected by widespread ozone depletion. Increased UV radiation due to ozone depletion is expected to increase human skin cancers and cataracts and to suppress human immune system functions.
CFCs and other ozone destroyers have been widely used as aerosol propellants, refrigerants, blowing agents, cleaning solvents, and fire extinguishing agents. CFCs are thought to be responsible for most ozone depletion. Though restricted for use as aerosol propellants, CFCs are still widely used as refrigerants, and this use shows an upward trend.
The Antarctic ozone hole
Much of the world’s stratospheric ozone is produced near the equator, However, air circulation patterns produce the greatest concentration of ozone in the polar regions. The term ozone hole refers to springtime thinning of the ozone layer above Antarctica; such thinning has been observed since the 1970s.
An Arctic ozone hole?
The ozone-deficient air masses that form over the North Pole are more mobile than those over Antarctica, thus threatening some densely populated regions of northern continents.
Tropical and midl-atitude ozone depletion
Conditions conducive to ozone depletion may occur in the tropics and mid-latitudes. Volcanic eruptions in tropical latitudes may contribute sulphur-based aerosols which trigger the necessary reactions.
Environmental effects
The potential environmental effects of ozone depletion include damage to aquatic and terrestrial food chains and a variety of human health effects. Increased UVB exposure resulting from ozone destruction can educe primary productivity in marine food chains, thus affecting all trophic levels and perhaps disrupting the global carbon cycle. Agricultural harvests could be negatively affected by widespread ozone depletion. Increased UV radiation due to ozone depletion is expected to increase human skin cancers and cataracts and to suppress human immune system functions.
Ozone depletion prevent - collection and Reuse of CFCs
CFCs in refrigerators, automobiles, and other cooling systems can be collected and reused rather than discarded.
Substitutes for CFCs
The two major substitutes for CFCs, HFCs and HCFCs, are less ozone-destructive
than CFCs, but are costly and may have other environmental effects. Other CFC substitutes, such as helium and propane, show great promise but face technological and/or economic difficulties in development .
Short-term adaptation to ozone depletion
Given the realities of present and future ozone depletion, the most sensible short- term approach will center on human adaptation to increased UV levels and increased commitment to researching the ecological implications of ozone depletion.
My persona favourite tips to prevent ozone depletion:
1. Minimising person vehicle driving
2. Understanding it illegal to recharge refrigerators, freezers and home/vehicle air
conditioners with CFCs
3. Not purchasing or using portable fire extinguishers that contain halons
4. Using environmental-friendly household products
5. Minimising using pesticides.
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