Unit 6 (Kognity Only) Flashcards
1
Q
The pH of natural deposition
A
Usually acidic between pH 5 and 6 due to the presence of carbon dioxide in the atmosphere forming carbonic acid
2
Q
Acid deposition occurs as a result of:
A
Primary pollutants of sulphur dioxide and nitrogen oxides reacting in the atmosphere to form secondary pollutants of sulphuric and nitric acid. Then, the pH declines to below 5
3
Q
The main human source of primary pollutants, sulphur dioxide and nitrogen oxides
A
The combustion of fossil fuels
4
Q
Natural sources of sulphur dioxide
A
Volcano emissions, hot springs, and biodegradation of dead organic matter
5
Q
Natural sources of nitrogen oxides
A
Lightning and biodegradation of dead organic matter
6
Q
Decomposition can occur as
A
Wet or dry deposition
7
Q
Wet deposition example
A
Earn pollutants are incorporated into the clouds or falling raindrops and result in acidified rain or snow
8
Q
Dry deposition example
A
When atmospheric pollutants are removed by gravity or direct contact under dry conditions. EG: when emissions of ash or dry particles from power stations are absorbed directly onto plants and buildings
9
Q
When sulphur dioxide and nitrogen oxides are emitted into the air
A
They can be transported long distances by prevailing winds. In the presence of strong winds, pollutants are dispersed over larger areas than with light winds which allow them to accumulate near the source resulting in more acute pollution
10
Q
Tall smoke stacks have often been used
A
To reduce local pollution by increasing dispersion of the pollutants
11
Q
Wind speeds are lower at ground level due to
A
Friction from the ground, vegetation and buildings. So there is less friction higher up where speeds are greater
12
Q
Prevailing winds
A
Carry pollutants long distances to otherwise unpolluted areas EG: the majority of Acid deposition in Norway originates in Germany, the UK, and Poland
13
Q
The topography downwind of the source pollution
A
Can affect the distribution of acidic deposition
14
Q
Pollution in mountainous areas
A
Moist air masses are forced to rise causing cooling and condensation resulting in precipitation potentially increasing acidification in the area
15
Q
The impacts of acid deposition on aquatic and terrestrial ecosystems
A
Depends on the capacity of the environment to neutralise the acidic input
16
Q
Calcium carbonate (limestone)
A
Has a high buffering capacity
17
Q
The presence of alkaline calcium and magnesium compounds
A
Increase the buffering capacity of soil and water, reducing the effect of acid deposition
18
Q
Acid deposition can enter aquatic ecosystems
A
Directly (EG: precipitation as rain) or indirectly (as run off) - it can also lower the pH of the quantity environment beyond the ability of some organisms to service
19
Q
Species that are sensitive to changes in pH
A
Phytoplankton, invertebrate (eg: crayfish) and fish (eg: trout and salmon)
20
Q
Loss of some species causes
A
A knock on effect through the food chain, adversely affecting other organisms due to lack of prey. Some species suffer from reproductive failure and many fish eggs do not hatch below pH 5
21
Q
When fish are exposed to aluminium ions
A
They secrete excess mucus around the gills preventing oxygen updates and leading to death by asphyxiation
22
Q
Decrease in soil pH
A
Releases aluminium ions, then leached into the aquatic system
23
Q
Acid deposition increases the rate of
A
Stone erosion and metal corrosion
24
Q
Metal corrosion
A
When acid deposition increases the corrosion of metals such as iron and steel, building structures are weakened
25
Stone erosion
Buildings made of marble and limestone are vulnerable to acid deposition which reacts with the calcium carbonate forming gypsum which flakes off. It also penetrated beyond the stone through the pores where crystals of gypsum can grow causing cracks to appear and stone to crumble
26
Terrestrial ecosystems acid deposition
Acid deposition on land increases soil acidity
27
The lowering of solid pH results in
Leaching of plant nutrients, mobilisation of aluminium ions, mobilisation of other toxic metals from soil
28
Leaching of plant nutrients
Calcium, magnesium, and potassium. This reduces the nutrients available for plant uptake
29
Overall, the effect of acid deposition in soil results in
Reduction in crop yield in agricultural areas, loss of biodiversity and reduction in forest areas
30
Exposure of plants to acid deposition results in:
Damage to the cuticle wax found on leaves reducing photosynthesis, lower tolerance to pests, disease and low temperature
31
Mobilisation of aluminium ions
Damage plant root systems and can also be leached into nearby watercourses adversely affecting fish and discussed above
32
Mobilisation of other toxic metals from soil
Cadmium, lead, and mercury which can then be leached into quantity ecosystems adversely affecting aquatic organisms and potentially contaminating drinking water
33
The main sources of sulphur dioxide and nitrogen oxides that’s result in formation of acid rain include:
Stationary sources, mobile sources
34
Stationary sources
IE: fixed point sources such as a power station, industry, and domestic boilers
35
Mobile sources
Predominantly vehicles
36
Methods to reduce emissions of air pollutants
Also apply to the reduction of acid deposition
37
Acid deposition is considered as...
A regional rather than global issue
38
Acid deposition is a....
Transboundary issue where impacts may occur hundreds of miles downwind of the source
39
Acid deposition frequently occurs...
In neighbouring or nearby countries
40
Conference focused on the growing problem of acid deposition
1972 United Nations conference on Human Environment in Stockholm
41
After the UN conference, activity was extended by....
The Geneva convention of long range transboundary air pollution in 1979, 1999 Gothenburg protocol to abate acidification, eutrophication, and ground level ozone with the last amendment in 2012. The Geneva invention allowed parties to share knowledge and scientific information to set and update emission targets
42
Regional air quality agreement
Between Canada and the US in 1991 to repair issues of transboundary pollution between the to countries, emission of precursors to acid deposition have fallen significantly in both countries
43
Cap and trade
Involves allocating utilities with permits which allow them to produce a set amount of emissions. The utilities are then free to buy and sell emission permits to each other. Those that do not use their permits gain economically by selling their surplus to other. The US uses it to reduce emission levels
44
Acid deposition clean up and restoration example:
In Sweden, linestone is added to some lakes annually to maintain a suitable pH for fish rocks. However, it is only seen as a short term solution while the source of pollution is reduced since a majority of the AD in Sweden is from other countries, with importance lying in cooperation
45
Terrestrial systems an be limed to....
Increase solid pH and immortalise toxic metals. On agricultural land, fertilisers may also be added to replace lost nutrients
46
In-situ clean up and restoration
Clean up methods have focused around neutralising the acidic water by adding limestone (calcium carbonate)
47
Liming in Sweden
Here, thousands of lakes were affected by acid deposition where liming has restored the natural pH of about 7500 lakes, restocking them with fish
48
Process of liming water
Raising the pH causes aluminium ions to precipitate out of the water column. However, it will reoccur if acid deposition continues.
49
When water is at a low pH
Aluminium ions are released back into the water column which can have a detrimental effect on fish stocks
50
Catalytic converters
Reduce emissions of nitrogen oxides, VOCs and carbon monoxide
51
A barometer ...
Measures air pressure. At sea level this is 760mm Hg (Mercury) and declines with increasing altitude. The lowest pressure on land is found at the highest peak of Mount Everest
52
Troposphere
The layer of the atmosphere closest to the earth’s surface including where we live, it extends about 10km above sea level
53
The greenhouse effect occurs in the
Troposphere and helps to regulate the temperature of the earth
54
In the troposphere
Most of out weather occurs, most of the atmospheric mass is found (including nearly all water vapour, clouds, and pollutants)
55
Humans and other organisms have the most interaction....
With the troposphere (EG: through the exchange of gases or the introduction of pollutants)
56
Temperature in the troposphere
Warmest near the earth surface with temperature declining around 6.5º per km.
57
Heat on the earth’s surface
The earth’s surface absorbs heat from the sun. The warm earth then heats the atmosphere through conduction
58
In the absence of GHGs
The heat would be radiated back into space potentially resulting in an average global temperature of -18º
59
In the presence of GHGs
Long wave radiation is absorbed by the gases resulting in warming of the atmosphere to an average global temperature of approx. 15º. This is the “Natural GH effect”
60
Human activities that alter the concentration of GHGs
In the atmosphere, can impact global temperatures
61
The albedo effect
Some solar energy does not enter the earth’s atmosphere reaching the ground. It is rather reflected back into space by clouds, particles, in the area and surfaces such as ice and snow
62
Energy from the sun enters as
Short wave radiation, and only some of it is absorbed by the earth’s surface
63
As the ground warms
Heat energy is radiated back into the atmosphere in the form of long wave radiation
64
Green house gases absorb
Long wave radiation
65
Water vapour
The most abundant GHG. Rise in temperature results in larger quantities leading to further warming, allowing more water to evaporate and the positive feedback cycle continues
66
Carbon dioxide
Concentrations are increased by burning fossil fuels, respiration, volcanic activity, and deforestation.
67
Plants and trees act as
Carbon sinks, removing carbon dioxide from the atmosphere, storing it in the form of biomass
68
Deforestation GHG impact
Reduces available carbon sinks which worsens the situation
69
Methane
Arises from livestock emissions, anaerobic decomposition of waste, rice cultivation, and fossil fuels
70
Anaerobic
“Relating to or requiring an absence of free oxygen”
71
Nitrous oxide
Sources include fertilisers, combustion, and industrial processes
72
Perfluorocarbon
Used in the production of aluminium
73
Chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs)
Used as liquid coolants (in refrigerators and air con systems), in the production of plastic foam as industrial solvents
74
Sulphur hexa-fluoride
Used in production of magnesium
75
The earth’s atmosphere consists of
4 distinct layers
76
Stratopause
Marks the ends of the stratosphere and is where the temperature remains constant with altitude
77
Stratosphere
Extends from 10 to 50km above sea level
78
Weather in the stratosphere
Wind increases with height, the air is dry
79
Stratospheric ozone
Absorbs ultra violet radiation from the sun
80
Temperature in the stratosphere
Constant at approx -60º in the lower part of the stratosphere, which is shielded by the ozone layer but then increases with altitude
81
Mesopause
Occurs at the end of the mesosphere and is where the temperature does not change
82
Both the mesosphere and the stratosphere
Provide some protection against meteorites
83
Mesosphere
Ranges from about 50 to 80km above sea level
84
Temperature in the mesosphere
Without the presence of ozone or other particles to absorb UV radiation, the temperature declines with height. The coldest part sees temperatures falling to -100º C
85
Weather in the mesosphere
There are strong winds which go up to 3,000 km/h
86
Thermosphere
Extends beyond 80km to between 500 to 1000km
87
Radiation in the thermosphere
UV and X-radiation from the sun is absorbed which breaks apart molecules into atoms
88
Main atomic components in the thermosphere
Oxygen, nitrogen, and helium atoms are the main components in the upper thermosphere
89
Temperature in the Thermosphere
Temperature increases with height and can reach beyond 2000º C. This heat can cause the layer to expand causing variation in depth overtime from 500-1000km
90
Ionosphere
Located within the thermosphere, comprising of an area in which the particles are electrically charged
91
Ionosphere radiation
Shortwave radio waves bounce off these ions back to earth, these are used by amateur radio enthusiasts to communicate over large distances
92
Another feature of the ionosphere
The “aurorae Polaris” (polar lights consisting of both the Northern lights in the northern hemisphere and the southern lights in the Southern Hemisphere) our as a result of electrically charged particles from the sun colliding with ions in the ionosphere
93
There is a debate about
Where the atmosphere ends and space begins
94
“The Karman Line”
At 100km above sea level, has been accepted as the point where atmosphere ends and space begins by the international aeronautic federation.
95
Other ISS orbit within
The thermosphere
96
The ozone layer occurs
In the stratosphere between 20-30 km
97
The hydrological and nutrient cycles
Influence levels of gases in the atmosphere
98
Some components of the atmosphere such as:
Carbon dioxide, water vapour, and ozone, vary significantly from one location to another and are effected by human activities such as combustion of fossil fuels
99
Nitrogen quantity in the atmosphere
78%
100
Oxygen quantity in the atmosphere
21%
101
Argon quantity in the atmosphere
0.93%
102
Neon quantity in the atmosphere
0.002%
103
Carbon dioxide, water vapour, Aragon, and other gases
17%
104
Water quantity in the atmosphere
Variable 0.01 to 4
105
Carbon dioxide quantity in the atmosphere
Variable eg: 0.03%
106
Ozone quantity in the atmosphere
Variable eg: 0.0006
107
During the Proterozoic era which followed the Archean era (2.5 billion to 542 million years ago)
Levels of atmospheric oxygen continued to increase
108
What occurred during the Proterozoic era?
Levels of carbon dioxide decreased, higher up the atmosphere, oxygen molecules were split by sunlight energy into atomic oxygen which lead to the formation of ozone, more complex single felled organisms (eukaryotes) appeared about 2 billion years ago, followed by multicellular organisms about 1 billion years ago
109
Life was restricted to the oceans until
The ozone layer had developed to shield the earth;s surface from the harmful effects of UV light
110
The first green plants appeared on land
Approx. 500 million years ago during the Phanerozoic era (542 million years UFO until present day)
111
Any oxygenn formed during the Archean era
Reacted with other gases and iron sulphide in the oceans to from red Ron oxide which then precipitated onto the seabed
112
The oxygen formation during the Archean era
Left to the formation of sedimentary rocks over time, containing red bands of oxidised iron
113
The earth’s early atmosphere predominately consisted of
Hydrogen and helium gases, which later escaped into space as a result of solar winds and a weak magnetic field within the earth
114
Volcanic emissions led to an atmosphere
Comprised of water vapour, carbon dioxide, methane, ammonia, and hydrogen sulphide
115
Life first appeared on earth
about 3.8 billion years ago in the form of simple felled bacteria (prokaryotes)
116
Early bacteria
anaerobic and included methane producing bacteria that used carbon dioxide and hydrogen. It evolved to capture and use light energy leading to photosynthetic bacteria
117
Phyotosynthetic bacteria
Produced oxygen as a by-product and included Cyanobacteria, responsible for increasing levels of atmospheric oxygen from less that 1% to almost 21%
118
The earth was formed approx.
4.5 billion years ago
119
The combustion of fossil fuels
Leads to emissions containing carbon dioxide, water vapour, sulphur dioxide, nitrogen oxides, and particulates such as smoke and soot
120
If combustion is incomplete
there may also be emissions of carbon monoxide and hydrocarbons.
121
Primary pollutants
Air pollutants which are directly emitted from their source
122
Secondary pollutants
Formed when primary pollutants react in the atmosphere
123
Examples of secondary pollutants
Acid rain, Ozone
124
One formation
When nitrogen dioxide and hydrocarbons react in the presence of sunlight energy
125
Acid rain formation
When nitrogen oxide and sulphur dioxide react with water
126
Nitrogen dioxide
Can be a primary of secondary pollutant
127
Nitrogen dioxide is a primary pollutant if
It is formed during fossil fuel combustion and emitted into the atmosphere
128
Nitrogen dioxide is a secondary pollutant when
It is formed from nitrogen oxide in the air reacting with oxygen
129
Carbon dioxide and water vapour
Green house gases, resulting in an increase in the average global temperature and contributing to climate change
130
Sulphur dioxide
Coal and oil contain sulphur, when these fossil fuels are combusted they produce sulphur dioxide gas which is toxic, and is linked to an increase risk of cardiac disease and death
131
Sulphur dioxide can act as...
A potent respiratory irritant which causes inflammation of the lungs, it can trigger asthma attacks, chronic bronchitis, and also increase the risk of lung infections. An eye irritant, and a Pricilla component of acid rain
132
Nitrogen oxides (NOx)
Yellow brown gas that can reduce visibility and apparatus as a haze over urban areas
133
Nitrogen oxides are
Respiratory irritants causing lung inflammation and triggering asthma, a principal component of acid rain, a precursor of photochemical smog and ozone formation
134
Particulates
Produced during FF combustion and emitted into the atmosphere. Suspended particulates such as smoke and soot are categorised according to size
135
PM 10
Particulate matter with a diameter of 10 μm of less. Exposure has been associated with an increased risk of cardiovascular disease
136
PM2.5
Particulate matter with a diameter of 2.5 μm or less. Can travel deep into the lungs, increasing the risk of respiratory diseases and cancer
137
World heath organisation (WHO) estimated that in 2012
Air pollution resulted in 3.7 premature deaths - 80% heart disease, 14% respiratory infections, 6% lung cancer
138
Main sources of NOx emissions
Industry, power stations, and vehicles
139
The main sources of volatile organic compunds (VOCs)
Industry, vehicles, solvents (eg: used in plants and adhesives)
140
Forest fires accidental or intentional (eg: slash and burn)
Increase levels of VOCs and particulate matter (PM10) while leading to deforestation and loss of habitats
141
Photochemical smog occurs
When sunlight activates reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) resulting in the formation of ozone and peroxyacyl nitrates (PAN)
142
VOCs (Volatile organic compounds)
Carbon based compounds with a low boiling point such as propane, butane, and formaldehydes
143
The formation of chemical smog involves
A series of complex reactions, the mixture of over 100 different chemicals formed is dominated by ozone, but also include other oxidants such as peroxuacyl nitrates (PAN) and aldehydes
144
The impacts of ozone on...
Healthy reduced crop production, and material degradation, also contribute to a significant economic loss
145
Air pollution
Can be blown downwind from its sauce to cause movement of pollution from urban to rural areas. Expanding the size of its impact
146
The formation of smog is affected by:
Climate, topography, population density, and the total amount of industry and vehicles
147
Impact of tropospheric ozone
Highly reactive, inflammation of lungs and contributing to asthma, reduces lung function contributing to lung disease and premature death, eye and nose irritation, damages fabrics like rubber and plastics
148
Impact of tropospheric ozone on the environment
Damages cells in leaves disrupting photosynthesis and reducing plant growth which affects crops and forest. In crops such as wheat, soya beans, tomatoes, and cotton, smog has also been found to increase risk of infection
149
Many cities experience photochemical smog yet it is more common when:
The city is located in a valley, weather is sunny and dry with little wind movement, there are high emissions from cars or industry (EG: LA, Rio, Mexico City)
150
Factors influencing the production of photochemical smog
Emissions, sunlight, winds, weather, topography, thermal inversion
151
Emissions - Factors influencing the production of photochemical smog
From the combustion of fossil fuels, influenced by the amount of industry, population size, common mode of transport in an area
152
Weather - Factors influencing the production of photochemical smog
The highest levels of ozone occur during the sunniest part of the day, calm or light winds reduce dispersion and dilution allowing pollutants to accumulate at ground level, dry weather in which rain does not wash the pollutants from the air
153
Topography - Factors influencing the production of photochemical smog
Allows pollutants to accumulate such as a valley surrounded by hills. The hills reduce the flow of air allowing pollution to concentrate in The Valley. Tall buildings also have the same impact increasing pollution levels
154
Thermal inversion - Factors influencing the production of photochemical smog
Occurs at ground level, warms, and rises which also dissipates the air pollutants. This air expands and cools resulting in a temperature gradient.
155
During a thermal inversion
Cold air is trapped below a layer of warm air. This can occur during cold winter nights when the earth’s surface cools and chills the later of air next to it. This is broken when the sun comes to warm the air.
156
Temperature inversions only last
A few hours unless meteorological factors (high pressure) result in clear, windless conditions that allow pollutants to accumulate at ground level. Although thermal inversions are usually shallow, deep inversions can occur in a valley and be slow to dissipate
157
Pollution reduction policies can employ the following approaches:
Altering human activity, legislation to prevent or regulate the release of air pollutants, clean up and restoration of damaged systems
158
Altering human activity can be achieved by changing human behaviour and may:
Involve education and campaigns to inform the public of the effects of air pollution and ways they can reduce omissions, be supported by economic instruments, involve the use of alternative technologies
159
Educational campaigns are often used to inform the public about:
The damage caused by air pollution, how they can take appropriate action to reduce emissions
160
Adopting practices at an individual level that reduce energy use (changing human behaviour)
Using more energy efficient devices such as refrigerators and washing machines, turning off appliances rather than in standby mode, making home modifications to reduce loss of heat through windows, doors, roof, and flooring such as efficient windows (triple glazed), wall cavity insulations, and ceiling and floor insulation
161
Some policies occur internationally, right down to locally. EG...
The EU has adopted air pollution policies that involved national government down to local regional governmental level to be effective
162
Other practises to modify human behaviour (part 2)
Decrease car use and us public transport, share vehicles, and cycling. Adopt hurried cars, reduce consumption of non-local goods that are transported long distances, decrease consumption of non local goods that utilise energy during production (EG: latest fashions encourage waste)
163
Hybrid and electric cars
Hybrid use both petrol and electricity or electric car only use electricity. They are effective in reducing air pollution when renewable sources of energy are used to generate the electricity. If FF are used. To generate electricity, emission control technologies should be employed to reduce levels of pollutants
164
Economic tools for changing human behaviour
Road tolls and parking charges to discourage cars, subsidising public transport, subsidies or tax credits to promote renewable energy sources, charging pollution emitters eg: pollution tax charged based on amount produced, use of subsidies to encourage new technologies and support research into methods to reduce pollution from combustion
165
Catalytic converters
Can be used on all motor vehicles to reduce the amount of potential pollutants
166
Catalytic converters process
Reduces NOx to form nitrogen and oxygen gas, oxidises carbon monoxide to form carbon dioxide, oxidises VOCs to carbon dioxide and water
167
Alternative energy sources
To reduce air emissions, technologies that harness renewable energy sources include solar panels and wind turbines
168
Current research is looking to....
Improve energy efficiency of processes and products, Fisher improve the efficiency of renewable energy sources, further develop low emission vehicles, develop low emission fuels
169
Increasing energy efficiency
More energy efficient industrial processes, more efficient cars and home appliances
170
Disadvantage of new technologies in energy efficiency
Technological changes require more time and financial investment to be developed. It might also require economic support to be competitive in the market place
171
Legislation
For legislation to be effective in reducing atmospheric pollution, it requires appropriate enforcement and policing
172
International agreements
Set goals that are then adopted into national policies
173
1999 Gothenburg Protocol
Abate acidification, eutrophication, and ground level ozone, sets a minimum emission standard for sulphur dioxide, nitrogen oxides, volatile organic compounds and ammonia
174
legislation setting emission standards
Can be used to set more stringent emission standards for industry, power generation, and vehicles. This encourages use of low sulphur fuel such as gas or adoption of renewable energy such as solar or wind to meet more stringent standards
175
Building regulations
Set standards that require improvements in new and existing building to improve energy efficiency. EG: improved insulation of to reduce loss of heat and more efficient appliances such as boilers
176
Planning regulations
Locates industry and power stations outside of urban areas and in places where conditions are least likely to allow air pollutants to accumulate. (EG: outside valleys) They also promote alternatives to private car use (vehicle free zones, cycle lanes, road lanes for car sharing or public transport)
177
Clean up measures
“Scrubbers” are used by industry and power stations to filter emissions prior to discharge to remove primary pollutants such as particulate matter and sulphur dioxide
178
Once photochemical smog is formed
Ozone and PAN are highly reactive and are removed by reactions with other chemicals. In polluted areas, levels of ozone fall overnight reacting with nitrogen oxide to form oxygen and nitrogen dioxide
179
Restoration
May involve reforestation and replanting of areas affected by smog
180
Stratospheric ozone is threatened by....
Chemicals that react with the ozone and reduce its concentration. They are names ozone depleting substances (ODS)
181
Ozone depleting substances (ODS)
Often contain chlorine or bromine. One of main groups are chlorofluorocarbons (CFCs). They also include methyl bromide, halons, carbon tetrachloride, methyl chloroform, and hydrobromofluorocarbons (HFCs)
182
Methyl bromide
Used as a soil fumigator to destroy pests. Natural sources include emissions from the ocean and the burning of biomass. It releases bromine into the stratosphere which is estimated 50 times more effective than chlorine at destroying ozone. Lifespan of 2 years
183
Halons
Similar to CFCs but contain bromine rather than chlorine. They are used as fire suppressants in fire extinguishers
184
Carbon tetrachloride
Used as a solvent, dry cleaning agent, refrigerant, and a propellant for aerosol cans
185
Methyl chloroform
Used in industrial solvents, degreasing agent, correction fluid, spray adhesive, and aerosols
186
Natural emissions of ODCs
Emissions from volcanoes. EG: the eruption of mount pinatubo in 1991 which released sulphate particles and nitrogen oxides which reacted with the stratospheric ozone, declining its levels,
187
Hydrobromonfluorocarbons (HBFCs)
Similar properties to CFCs and contain either or both bromine and fluorine. Used as solvents, cleaning agents, and as suppressants in fire extinguishers
188
Special differences
Variation is stratospheric ozone levels around the world, both seasonal and long term changes.
189
Chlorofluorocarbons (CFCs)
A farming of chemicals discovered in 1930 including CFC-11, CFC-12 sometimes referred to as their trade name - Freons
190
CFCs are widely used as
Coolants in refrigerators and air con systems, propellants in erosion cans, cleaning agents for electrical parts, blowing agents in plastic foam
191
CFCs are...
Very stable compounds with lifetimes of between 65-110 years. They were initially considered as non-problematic to the environment due to their high stability
192
CFCs are not...
Solvable and therefore can not be removed by rain. They dissipate into the air. Over a period of 10-20 years, they gradually migrate upwards from the troposphere into the stratosphere
193
CFCs in the stratosphere
UV light breaks down the molecule producing chlorine atoms that react with ozone, breaking it down and reforming chlorine atoms. This is a chain reaction, and unsettles the previous ozone equilibrium. More ozone is destroyed than formed resulting in depletion
194
Scientists have estimated one molecule of CFC
Can destroy 100,000 molecules of ozone
195
Once chlorine atoms form hydrogen chloride
It diffuses out of the stratosphere into the troposphere where it is washed out by rain
196
Formation of ozone
Ozone is created from a series of different oxygen molecules and atoms. When a short wave of UV light hits an oxygen molecule (O2), the molecule splits to become 2 oxygen atoms. Then one of these will join with another O2 molecule, and combine to become Ozone, being O3. This O3 makes up the Ozone layer. If the UV light hits it at this point, it will remain as O3
197
Ultraviolet (UV) radiation in the stratospheric ozone
From the sun, categorised to its wavelengths either as UV-A, UV-B, or UV-C. Ozone has the ability to absorb some but not all wavelengths
198
UV-A
Longest wavelength, between 3.15-400nm - ozone is unable to absorb this and it passes through the the ground level
199
UV-B
Wavelength between 280-315nm - ozone absorbs most of this radiation but some pases into the troposphere below
200
UV-C
Shortest wavelength, highest energy 100-280nm - ozone and atmosphere can absorb all radiation, preventing it from reaching the earth’s surface
201
To try and prevent skin cancer due to UV exposure
Governments have sponsored public awareness campaigns to encourage people to protect themselves from the sun and stay inside when UV-B levels are high
202
Ozone levels are measured in
Dobson units (DU) which is the depth the ozone molecules occupy at standard temperature and pressure and 1 atmosphere
203
When ozone concentration falls
The molecules become more dispersed within the same area - known as “ozone thinning”
204
Ozone levels are often measured using
Lasers or a Dobson spectrophotometer which measures intensity of certain wavelengths
205
Normal ozone levels
Range from 300-500 Dobson units (3-5mm of thickness)
206
Due to levels of insulation
Ozone production is highest in the tropical state sphere and is moved by prevailing atmospheric circulation systems towards the poles
207
Benefits of UV radiation
Treats psoriasis and vitiligo (skin diseases), used as a steriliser as it kills pathogenic bacteria, air and water purifier, industrial uses in lasers, lighting, forensic analysis, stimulates production of vitamin d in animal
208
Photosynthetic organisms are sensitive to UV
This can disrupt food pyramids
209
UV-B leads to
Sunburn, skin cancers, cataracts formation which reduces vision and leads to blindness, immune system suppression to increase risk of infections, heath problems in animals (cancers, eye damage, lower yields in crop production (rice, soya beans), redice phytoplankton growth, reduction in seafood, reduction in forest productivity reducing amount of carbon dioxide absorbed causing CC, damage to living tissues
210
Challenges with ODS
Long life span, lack of alternative, illegal trade, still present in discarded equipment, replacement chemicals still contain them, lack of enforcement
211
Long life span of ODS
ODS like CFCs will have an affect long after production concludes
212
ODS present in discarded equipment
They still remain present in discarded items such as air cons and fridges which may leak into the environment. Although some are recovered and destroyed, some still remain in unused materials.
213
Lack of alternatives
There are no cheaper and effective alternatives to OCDs (EG: polystyrene)
214
Illegal trade
This takes place with banned ODS. This is because of less effective replacements, higher cost of alternatives, and the cost of altering existing air con and fridge systems. This trade requires further policing and enforcement
215
Replacement chemicals also contain ODS
Chemicals to replaces CFCs include HCFs and CHCIF2. However, although they still contain ODS, they have a shorter life of 2-20 years in comparison to 110 causing 2.5% of ozone depletion in comparison to CFCs which could still reduce ozone if used in large quantities
216
Both CFCs and HCFCs are
Greenhouse gases (Under the Montreal Protocol HCFCs should be phased out by 2030)
217
Clean up and restoration
Add ozone to remove chlorine from stratosphere, removal and destruction of existing ODS like CFCs
218
Controlling the release
Recover and recycle CFCs, capture them from scrap cars. Ban production and use of main ODS. Policing to ensure compliance and stop of illegal use. National legislation and policy measures
219
Altering human activity
replace CFCs with carbon dioxide, propane, butane or air as a propeller, replace aerosols with pump sprays, replays methyl bromide pesticides, replace ODS with cyclopentane as a blowing agent in production of foam insulation material (gas blown plastics)
