Ozone Depletion (p1) Flashcards
(19 cards)
What is the range of UV A radiation?
320-400nm
UV A radiation is used by the skin to synthesize Vitamin A but also causes sunburn and cataracts.
What does UV B radiation damage?
Organic molecules such as DNA and chlorophyll
UV B radiation is higher in energy than UV A and some of it is absorbed.
What is the role of ozone in the atmosphere?
Ozone absorbs harmful UV radiation
Ozone absorbs wavelengths up to about 310 nm, protecting life on Earth.
What is ozone?
An allotrope of oxygen gas (O3)
Ozone is made naturally in the atmosphere and can also be produced by photocopiers and laser printers.
How is ozone formed in the stratosphere?
Oxygen gas molecules are bombarded by high-energy UV light from the Sun, forming oxygen radicals which react to make ozone
The reaction can be summarized as: 3O2 → 2O3.
What happens to ozone molecules when they are hit by UV radiation?
They break up to form oxygen gas molecules and oxygen radicals
The reaction can be summarized as: 2O3 → 2O. + 2O2.
What are CFCs?
Chlorofluorocarbons, organic molecules containing chlorine, fluorine, and carbon
CFCs are used in refrigerants, aerosol propellants, and as solvents.
What was the Rowland-Molina Hypothesis?
A theory suggesting that the chemical properties of CFCs could lead to ozone depletion
It was based on the persistence of CFCs and their dissociation by UV radiation.
How do CFCs deplete ozone?
CFCs react with UV light in the stratosphere, releasing chlorine radicals that destroy ozone
This process involves several steps including the formation of Cl• and ClO•.
What medical problems can increased UV radiation cause?
Increased risk of sunburn, skin cancer, and cataracts
It can also damage plant tissues and inhibit the reproductive cycle of various species.
How is ozone measured?
In Dobson units
A Dobson unit corresponds to a layer of gas with a thickness of one hundredth of a mm.
What evidence supports the reduction of ozone levels?
Ground-based data collection, satellite surveys, air samples from the stratosphere
Increased UV levels at ground level and higher-than-expected UV readings reflected by Earth indicate ozone loss.
What is the Montreal Protocol?
An international agreement to reduce the use of CFCs and other ozone-depleting substances
It includes provisions for phasing out the manufacture and use of these substances.
What alternatives have replaced CFCs in aerosols?
Propane and butane
These alternatives are flammable compared to the original CFCs.
True or False: CFCs are flammable.
False
CFCs were not flammable, which made them popular for various applications.
Fill in the blank: Ozone can be destroyed by _______.
Ozone-Depleting Substances (ODS)
Examples include halogenated hydrocarbons like CFCs and HCFCs.
What is the effect of stratospheric conditions over Antarctica on ozone depletion?
Stratospheric temperatures are lower, forming ice crystals that facilitate chemical reactions
This results in more severe ozone depletion due to higher concentrations of chlorine.
What is the impact of the Montreal Protocol on ozone levels?
It has led to a global decrease in stratospheric ozone by 3% between 1980 and 2005
Ozone thinning over Antarctica has been observed to be around 50% in winter and spring.
What substances are used as alternatives to CFCs in asthma inhalers?
Hydrofluoroalkanes (HFAs)
These alternatives do not contribute to ozone depletion.
