L06 - Ozone Depleting Substances Flashcards
What is ‘good ozone’ ?
About 90% of the ozone in our
atmosphere is contained in the
stratosphere (at about 15 to 35 km
above Earth’s surface). This is good
ozone.
It has a concentration of 5 to 8 ppm (which is the ozone layer).
Why is the ozone layer important?
It absorbs biologically harmful ultraviolet (UV) radiation emitted from the Sun.
What is bad ozone?
“Bad ozone” refers to ground-level ozone, which is a harmful air pollutant.
What is ozone depletion?
It describes a steady decline
of ozone in Earth’s ozone layer.
What is the ozone hole?
Ozone hole refers to this depletion observed over the poles.
How does the ozone layer deplete?
- Primary cause of ozone depletion is the emission of chlorine-containing gases from industry
- In the presence of ultra-violet (UV) light, these gases dissociate, releasing chlorine atoms
- Chlorine then catalyses the ozone
destruction
What are the main gases the deplete the ozone layer?
- Halons (bromine containing gases) & CFCs (chlorine containing gases)
- Propellants in aerosols, blowing agents in foam manufacture,
air conditioning and fire extinguishers.
Two types of ODS on board ships?
- CFC-11 Trichlorofluoromethane : CCl3F
- CFC-12 Dichlorodifluoromethane
Explain the refrigeration system of a ship and how it’s a source of ODSs.
Refrigeration systems are based on
vapour-compression principle, and refrigerants are used as working substances in refrigeration systems. Therefore, when refrigerant leak, they contribute to ODSs emissions to the atmosphere.
What do reactive gases contain?
Chlorine and Bromine
ODS stands for what? What sort of damages ODS could cause?
What is the main chemical element in an ODS that is responsible for
ozone depletion? Explain the mechanism of Ozone destruction in
atmosphere.
What does CFC stand for?
Chlorofluorocarbon
Is this statement true and why: “Reducing the release of ODS into the atmosphere has no impact on global warming”?
Name one gas that can be used as refrigerant and has no impact on
Ozone Layer at all.
CO2
R744, carbon dioxide, has several attractive characteristics: non-flammable, does not cause ozone depletion, very low toxicity index (safety A1), available in large quantities, and low cost.
