Chapter 26 - Ozone depletion study guide
What are the peak concentrations of ozone?
400ppb
It has been estimated that during the catalytic chain reactions, there are around _____ interruptions while the chlorine is in the stratosphere.
200
How many oxygens are in ozone?
3
average stratospheric ozone levels:
300 DU
What % of UV solar radiation is screened out by the ozone layer?
99%
ART of ozone depleting sources
75-150 years
What % of the atmospheric ozone is found in the stratosphere?
90%
What is the process of the Polar hole in the transition from their winter to spring?
As their temperatures drop and clouds form, nearly all the nitrogen oxides in the air mass are held in the clouds as nitric acid. The nitric acid particles grow large enough to fall from gravitational settling from the stratosphere. This results in the small amounts of nitrogen oxide being left in the atmosphere in the vicinity of the clouds. These processes facilitate the ozone-depleting processes that reduce ozone, and once the sun comes during the polar spring, all of the chemical reactions are accelerated and ozone is depleted even further
What direction does the Antarctic polar vortex spin?
Counter-clockwise because it is in the southern hemisphere
How is ozone concentration measures?
Dobson Units
What two reactions occur when CFC's wander to the upper part of the stratosphere,
When CFC's wander to the upper part of the stratosphere however, reactions do occur, even with the earlier statement that CFC's are nonreactive. UVC splits the CFC releasing chlorine. The two reaction following this process: 1) Cl+o3 ----> ClO+o2 2)Clo+o ----> Cl + o2
How do the pollutants solidify in the Antarctic Polar Vortex?
With the clouds being extremely cold (-60 to -100), the particles become frozen and the sulfur acid particles serve as seed particles for nitric acid
Is there an arctic hole similar to the Antarctic hole?
Yes, there is ozone depletion above the north pole, but not nearly at the rate of the south pole ozone depletion
Collection and reuse of CFC's
You can recycle refrigerators because they use CFC's for coolant gas
Ground level ozone is _____
bad
The release of chlorine from the following equation: HCl + ClONO2 ----> Cl2 + HNO3, releases the ______ atom to the open, accelerating the ozone depletion
chlorine
1) Cl+o3 ----> ClO+o2 2)Clo+o ----> Cl + o2 These two equations define a chemical cycle that can _____ozone
deplete
Ozone (does/doesn't) react with many materials in the atmosphere
does
What would be required for developing countries to switch to HCFC's and HFC's?
massive financial aid would be required
CFC's are responsible for the (most/least) ozone depletion
most
Ozone is a (weak/strong) oxidant
strong
UVC
λ = .28-.1 μm most energetic, absorbed in stratosphere, doesn't reach Earth's surface
UVB
λ = .32-.28 μm can cause damage, mostly absorbed by ozone*
UVA (wavelength?)
λ= .4-.32 μm
Ultraviolet B (UVB) details
- Energetic and strongly absorbed by the stratospheric ozone - Ozone is the only known gas that can absorb UVB - Ozone depletion results from an increase in the amount of UVB that reaches the surface of the earth - Hazardous to living things -ozone problem present from this
What are dobson units?
- They are the common way that we measure ozone concentration. - 1 DU = 1 ppb ozone
Ultraviolet A (UVA) details
- This radiation has the longest wavelengths of the 3 - Has the least energy of the 3 - Can cause some damage to living cells - Is not affected by stratospheric ozone - Transmitted to the surface of the Earth
Properties of CFC's
-CFC's emitted in the lower atmosphere are extremely STABLE -They are nonreactive in the lower atmosphere -There are no significant troposphere sinks for CFC's known besides soil. (possible exception) -Because CFC's have a long residence time in the lower atmosphere and because the lower atmosphere is very fluid, with abundant mixing, the CFC's eventually wander upward and enter the stratosphere -Once they reach altitudes above most of the stratospheric zones, they may be destroyed by the UVC radiation, as a result, chlorine is released -The reactive chlorine released may then enter into reactions that deplete ozone in stratosphere -The result of the depletion of ozone is an increase in the amount of UVB radiation that reaches the earth's surface
2nd thing that can stop a catalytic chain reaction
2) Chlorine released from CFC's may combine with methane to form hydrochloric acid may then diffuse downward. If it enters the troposphere, rain may remove it, thus removing the chlorine from the ozone-destroying chain reaction. This is the ultimate end for most chlorine atoms in the stratosphere. However, while the hydrochloric acid molecule is in the stratosphere, it may be destroyed by incoming solar radiation, releasing the chlorine for additional ozone depletion.
HCFC's details and characteristics
-HCFC's have a hydrogen atom instead of a chlorine atom -HCFC's can be broken down in the lower atmosphere -Still can cause o3 depletion if it doesn't reach the stratosphere -atmosphere lifetime is much shorter than CFC's -they do not inject chlorine into the atmosphere
Ultraviolet C (UVC) details and characteristics
-Has the shortest wavelength -the most energetic of the 3 -has enough energy to break down diatomic oxygen in the stratosphere into two oxygen atoms. Each of these oxygen atoms may combine with a diatomic oxygen atom to create ozone -is strongly absorbed in the atmosphere -Little to none of this UV reaches the earth's surface
CFC details (from powerpoint)
-Originally developed as a refrigerant, used in air conditioners, refrigerators, -non toxic, chemically stable, cheap -Other uses: aerosols, foams -no longer used for aerosols, still widely used as -refrigerants
What is the Montreal Protocol
-The Montreal protocol is the convention/agreement of countries stating that they would decrease use of CFC's by 50% (1986) -Called for elimination of CFC's -troubling because of economic gaps between countries -China and India did not sign -limited production of O3 depleting substances
HFC's details and characteristics
-controversial -more expensive than CFC's -Still cause o3 depletion -Some blends of HFC's don't cause o3 depeletion
1990 - Amendments to Clean Air Act
-ended U S production of CFCs, CCl4 and methyl chloroform -Refrigerants can be collected and reused. -New products (HFCs and HCFCs): less damaging to the ozone layer, but are more expensive
Polar Antarctica hole (powerpoint def)
-polar vortex, air is isolated -extreme cold forms polar stratospheric clouds, ties up Cl -Energy from spring sunlight releases Cl, starts destruction of O3
Ozone depleting chemicals:
1) CFC's 2) CCL4 (Methyl Chloroform)/(methyl bromide) solvents used in dry cleaning 3) Halons (used in fire extinguishers, styrofoam,
Environmental effects of ozone depletion
1) Damage to earth;s food chains on land and in the oceans 2) Decrease of phytoplankton, which is a main carbon dioxide sink, and if that gets lost, that would even further global warming
Substitutes for CFC's (2)
1) HFC's (Hydrofuorocarbons) 2) HCFC's (Hydrochlorofuorocarbons)
What are the two important sinks of chlorine?
1) Hydrochoric acid 2) Chlorine Nitrate
Ways to reduce UV exposure
1) Limit exposure to times with less sunlight 2) When possible, remain in shade 3) Use sunscreen with spf of 30+ 4) Wear a wide brimmed hat and full clothing 5) Wear UV protective sunglasses 6) Avoid tanning salons and sunlamps 7) Consult U index before going outside
1st thing that can stop a catalytic chain reaction
1) UV light breaks down the CFC's to release Chlorine, which combines with ozone to from chlorine monoxide. The chlorine monoxide may then react with nitrogen oxide to form a chlorine nitrate. If this reaction occurs, ozone depletion is minimal. The chlorine nitrate, however, is only a temporary reservoir for chlorine. The compound may be destroyed, and the chlorine released again.
What are the 3 types of UV solar radiation
1) UVA 2) UVB 3) UVC
How is stratospheric ozone created?
1) When intense UVC light breaks apart an oxygen molecule (o2) through the process of photo-dissociation into two oxygen atoms 2) The atoms then react with another oxygen molecule to form two ozone molecules 3) Ozone, once produced, may absorb UVC radiation, which breaks the ozone molecule into an oxygen molecule and an oxygen atom 4) This is followed by the recombination of the oxygen atom with another oxygen molecule to re-form into ozone 5) As part of this process, UVC radiation is converted to heat energy in the stratosphere
Human health effects of ozone depletion
1) development of skin cancers 2) Cataracts
Process of forming ozone (PowerPoint process)
1) diatomic oxygen is split O2 → O + O 2) O atoms combine with oxygen molecules O + O2 → O3 3) Additional U V splits ozone into O2 and O which recombines to form O3 O3→ O2 + O → O3 4) This process occurs constantly and absorbs UV radiation energy
What is the scale on the UV index?
1-11+
It is approximated that chlorine can destroy approximately ____ molecules of ozone over a period of one or two years
100,000
In which altitude is the highest concentration of ozone?
15-40km (9-25mi)
What year did usage of CFC's for propellant gas for spray cans stop from bans?
1970
What are CFC's?
CFC's stand for Chlorofuorocarbons
1) Cl+o3 ----> ClO+o2 2)Clo+o ----> Cl + o2 These two equations cycle chlorine and keep producing chlorine infinitely until the it gets moved out of the atmosphere. The terms for these two equations is _________
Catalytic chain reaction, chlorine is a product and a reactant
What are the 2 most common ozone "depleters"
Chlorine and Bromine
Chemistry of Ozone Depletion (powerpoint formula)
Cl + O3 → ClO + O2 O3 + UV light → O2 + O O + ClO → Cl + O2 Net: 2 O3 → 3 O2
What is one of the most common and essential use of CFC's?
Coolant gas for refrigeration units
How do you know if it is the part of the day with the highest UV exposure?
If your shadow is not as long as your height
What is the layer of ozone that protects us from UV called?
It is called the ozone shield
Between which wavelengths does UV solar radiation occur?
It is present between 0.1 and 0.4μ
What is the Antarctic Polar Vortex?
It is when the air mass is isolated from the rest of the atmosphere and circulates about the pole in what is called the Antarctic Polar Vortex
What is the key issue of management of ozone depletion?
It is whether the depletion is natural or human-induced
What are nitrous oxides?
NOx Nitrogen oxides, especially from jet contrails, also play a major role in ozone depletion
In part as a result of the ozone-deletion reactions, concentrations of ozone have decline in which two areas?
Northern and Southern Temperate latitudes
In the lower atmosphere, how is ozone created?
Ozone is created in the lower atmosphere from photochemical reactions involving sunlight, nitrogen oxides, hydrocarbons, and diatomic oxygen
What is the UV index?
The UV index is service made by the National weather service and the EPA to inform the general public about the air quality and whether or not it is safe to go outside.
For the southern hemisphere, where is the lowest concentration of ozone?
The equator
Where is much of the worlds ozone produced?
The equator
When is the Antarctic Ozone hole measured?
The holes is measured every year during the October because during October, it is Antarctica's spring season
Where does the ozone in the stratosphere move?
The ozone in the stratosphere moves from the equator toward the poles with global air circulation patterns
For the southern hemisphere, where is the highest concentration of ozone?
The polar regions
How many types of Polar stratospheric clouds are there?
There are two, type 1 and type 2
What are type 2 polar stratospheric clouds?
They are polar stratospheric clouds that have larger frozen particles
What are Polar Stratospheric Clouds
They are the clouds located above Antarctica usually several miles thick, blocking out sunlight
What are type 1 polar stratospheric clouds?
They are the polar stratospheric clouds that have smaller frozen particles
Why is the north pole ozone depletion a prossible?
This is a possible problem because of the all the ozone-deficient air being released and then being swept across North America and that air can be harmful.
What is the needed plan of action to decrease air pollutants in the future?
This is not quite known yet, but the future plan of action to attempt to take already-existing pollutants out of the atmosphere
When did the USA stop using CFC's as an aerosol propellant
USA stopped using CFC's in 1995
What usually dissipates the Arctic Polar Vortex?
Usually the Arctic Polar Vortex is dissipated by warmer air from the midlatitudes