OZONE DEPLETION AND GLOBAL WARMING CLASS NOTES

OZONE DEPLETION AND GLOBAL WARMING

CLASS NOTES

Ozone depletion is decrease of ozone layer.

This depletion of ozone will allow

harmful ultra-violet radiations reach earth.

Global warming is Increase in the average

temperature of earth and sea. It is due to

absorption of infra red radiations by green

house gases. Both are harmful to all types of life.

ATMOSPHERIC LAYERS

(i) Troposphere:      up to 11 km from sea level. About 80% of the total mass of the atmosphere in troposphere,  Earth weather – in the troposphere. Maximum temperature is near the Earth’s surface in this layer, Air temperature drops approximately 6.5° C/ 1000 m, called ENVIRONMENTAL LAPSE RATE,   -56.5° C at the top of the troposphere ,  a narrow transition zone at the top, called- TROPOPAUSE. In this  TROPOPAUSE, Temperature remains constant.

(ii) Stratosphere:                11-50 km, T increases

Lower stratosphere:        11 – 36 km, T rises.
Upper stratosphere:        36 – 50 km, T rises
19.9% of the total mass found in the atmosphere, very little weather – in stratosphere,   First 9 km stratosphere, T=Constant with height,  This 9 km zone with T =C = Isothermal layer.
From  20 to 50 km, Temperature rises with altitude,
Temperature increases  as O3 absorb UV radiations,
O3 layer in11 to 50 km,
O3 layer  protects life from harmful effects UV,
Without O3 layer life could not exist on Earth,
Earth transition zone at top is STRATOPAUSE.

(iii)  Mesosphere:        50 -80 km, T decreases & –1000C at top, At top transition zone– MESOPAUSE ( mesosphere and thermosphere)

(iv)  Thermosphere:            80-550 km, T rises, >10000C at the top

(v)                 Exosphere:                   550-1000 km, vacuum

OZONE DEPLETION

decrease of ozone concentration in the lower stratosphere (11-36 km).
REGION OF OZONE —-11-50 km vertically above the Earth’s surface.

CAUSES OF OZONE DEPLETION

Ozone depletion — due to chlorine in the atmosphere.

SOURCES OF CHLORINE IN ATMOSPHERE

(i)     Freon refrigerants (CFC, HCFC)
(ii)   Halen,
(iii) methyl bromide, a deadly pesticide
(iv) From sea by evaporation
OZONE FORMATION PROCESS
Three allotropic forms of oxygen exist:
(i)      Single atomic oxygen (O),
(ii)   Di-atomic oxygen (O2 ),
(iii)  Tri-atomic oxygen or ozone gas (O3 ).
Oxygen molecules photo dissociate due to UV photon with λ < 240 nm.
It gives two oxygen atoms. The atomic O combines with O2 to create O3.
O2+Energy of I UV photon = O + O
 O2+O=O3

 OZONE DEPLETION PROCESS

 Ozone – destroyed by a number of free-radicals
Hydroxyl radical (OH·):              Natural origin
Nitric Oxide radical (NO·):   Natural origin
Atomic chlorine (cl·):             Manmade
Atomic bromine  (Br·):          Manmade
Elements cl and Br  in CFCs,
These go to the stratosphere.  Not destroyed in troposphere due to their low reactivity.
 UV radiations with λ=0.01 to 0.24 microns liberate cl and Br atoms from chlorine compounds.
CFC + hν (energy) of ultraviolet radiations → Chlorofluorocarbon + Chlorine atom
CFCl3+ hν (energy) → CFCl2 + Cl
Cl + O3 → ClO + O2
ClO + O3 → Cl + 2 O2
 A single chlorine atom keeps destroying O3 for two years. Single ‘cl’ atom reacts  100,000 ozone molecules.
 Region of Global Warming             
Troposphere up to 11 km from earth
Cause of Global Warming
Greenhouse effect
green house gases absorb infra red radiations
 MAIN GREENHOUSE GASES
 water vapor (36-70 %),
carbon dioxide CO2 (9-26 %),
methane (4-9 %) and
ozone (3-7 %).
OTHER GREEN HOUSE GASES
Nitrous oxide
Sulfur hexafluoride,
Hydro fluorocarbons,
Per fluorocarbons and chlorofluorocarbons.
 MEASUREMENT GLOBAL WARMING
Unit mass of CO2 causes 1 unit of global warming

SOURCES OF CARBON DIOXIDE

(i) largest source — burning of fossil fuels
(ii)  population increase,
(iii)  demand for more power production
(iv)  increase in number of vehicles,
(v)  More  houses resulting deforestation
(vi) widening of roads with cutting trees & deforestation
97 % Global warming by (CO2, CH4, N2O, CFC-12 and CFC-11)
03% Global warming by remaining greenhouse gases
Life of CO2 is 50 to 200 years.
THE GREENHOUSE EFFECT
Earth becomes warm due to sunlight. Most of it radiated back to the atmosphere at λ >  λsun rays. Some Rays of large λ absorbed by greenhouse gases warms the atmosphere. These greenhouse gases act like a mirror. Some heat reflects back to earth. Otherwise this heat goes to space. Reflecting heat energy towards earth is  “the greenhouse effect”.

CAUSES OF OZONE DEPLETION

Presence of CFC,HCFC, HBFC, chlorine, bromine, OH ions and NO ions
ODP AND GWP OF VARIOUS CHEMICALS
Reference: ODP of R-11 is 1 unit.
GWP of Co2 is 1 unit.
TABLE: ODP AND GWP OF CHEMICALS
Refrigerant
ODP
GWP
R-11 Tri-chloro-fluoro-methane
1.0
4000
R-12 Dichlorodifluoromethane
1.0
2400
R-13 B1 Bromo-tri-fluoro-methane
10
Not known
R-22 Chloro-difluoro-methane
0.05
1700
R-113 Tri-chloro-tri-fluoroethane
0.8
4800
R-114 Di-chloro-tetraf-luoroethane
1.0
3.9
R-123 Di-chloro-tri-fluoro-ethane
0.02
0.02
R-124 Chloro-tetra-fluoro-ethane
0.02
620
R-717 Ammonia – NH3
0
0
R-718 Water – H20
0
0
R-729 Air
0
0
R-744 Carbon Dioxide – CO2
0
1

 EFFECTS OF OZONE DEPLETION

More harmful UV radiation will reach earth & will cause
(i)  Sunburns will increase,
(ii) Premature aging of skin,
(iii)  Skin cancer
(iv) Causes immune suppression in  animals and human beings leading to infectious diseases.
(v)  Eye cataracts leading to blindness
(vi)  Output decreases in rice, wheat, corn, soybean, vegetables and fish.
(vii) Increased eye and skin cancer in domestic animals
(viii) Overexposure to UV rad  degrades wood, plastic, rubber
(ix)  Reduces phytoplankton , oceanic food chain.
(x)  Malaria, dengue, increase.
(xi) Virus persists for longer duration.
(xii) Infections increase further compounded by malnutrition.
(xiii) Children by birth will have body defects.
(xiv) Increases healing time for a wound
(xv) More and more dangerous virus will be in the atmosphere.

CONTROL OF OZONE DEPLETION

MONTREAL PROTOCOL 1987

Time bound international agreement to minimize ozone depletion. It is to achieved  by drastically decreasing the production. Side by side increase the cost of ‘Substances that deplete the ozone layer’.
(a)   CFC Phase-out Schedules:
(a)   CFC Phase-out Schedules: Allowed Production and Consumption for Developed Countries (percent of baseline 1990)
1987
Original Montreal Protocol
1990
London Montreal Protocol
1992
Copenhagen Montreal Protocol
1990
U.S. Clean-Air Act Amendments
1994
European Community    Schedule
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
100%
100%
100%
80%
80%
80%
80%
80%
80%
50%
50%
100%
100%
80%
80%
50%
50%
15%
15%
15%
0%
25%
25%
0%
85%
80%
75%
25%
25%
0%
50%
15%
0%
(b)   HCFC PHASE-OUT SCHEDULE
(i) Developed Countries  1996 level of production=100 %
(ii)               2004————–65 %
(iii)             2010————–35 %
(iv)             2015————–10 %
(v)               2020————–0.5 %
(vi)             2030————– 0 %
(II) DEVELOPING COUNTRIES
January 1, 2016: 10 %
January 1, 2040: Complete phase-out

 EFFECT OF CFC REFRIGERANTS (  R11, R12) ON OZONE DEPLETION

These contain chlorine. Life of  chlorine in atmosphere is around 100 years. It is only chlorine which depletes the ozone layer. 1 atom of chlorine can destroy 1 lac molecules of ozone. These posses high Ozone Depletion and high Global Warming potential. Use prohibited.

EFFECT OF HCFC REFRIGERANTS(R-22) ON OZONE DEPLETION 

 ODP and GWP less than R-12.  Use R-22 till 2030.
TABLE: ODPAND GWP OF CHEMICALS
Refrigerant ODP GWP
R-11 Tri-chloro-fluoro-methane
1.0
4000
R-12 Dichlorodifluoromethane
1.0
2400
R-13 B1 Bromo-trifluoro-methane
10
Not known
R-22 Chlorodifluoromethane
0.05
1700
R-113 Trichloro-trifluoro-ethane
0.8
4800
R-114 Dichloro-tetrafluoro-ethane
1.0
3.9
R-123 Dichloro-trifluoro-ethane
0.02
0.02
R-124 Chloro-tetrafluoro-ethane
0.02
620
R-717 Ammonia – NH3
0
0
R-718 Water – H20
0
0
R-729 Air
0
0
R-744 Carbon Dioxide – CO2
0
1

 GLOBAL WARMING CAN INCREASE OZONE DEPLETION

Global warming increases stratospheric O3 depletion. O3 depletion increase on stratosphere becomeing colder. Global warming traps heat , less heat reaches stratosphere and becomes colder.

IMPACTS FROM GLOBAL WARMING

(i)  Increase of Tearth by about 3° to 5° C by 2100,
(ii)  Melting of glaciers &
(iii) Already  rise of sea levels 10-25 cm , 25 m by 2100,
(iv) Flooding of low lying areas
(v)  Extreme heat waves,
(vi) Droughts,
(vii) Storms,
(viii) Extinction of species,
(ix)  Loss of entire forests,
(x)   Marine life destruction
(xi)  More ozone depletion,
(xii)  Lower agricultural yields,
(xiii) Malaria returns to areas extinguished earlier.
(xiv) Pests will grow faster
(xv)  Increase in epidemics.
CATASTROPHIC CLIMATE CHANGES as concentration of CO2
in atmosphere reaches 450 ppm.
Present is 380 ppm
Increases 2 – 3 ppm each year,
critical value in 25 to 30 years.
STEPS TO CONTROL GLOBAL WARMING  
(i)   Produce thermo-solar power,
(ii)  Produce Nuclear Power,
(iii)Reduce the use of vehicles,
(iv)Pool vehicles,
(v) Eat less meat,
(vi) Grow more plantations,
(vii) Use less TV& Air conditioner,
(viii) Reduces power wastage by switching off lights when not in use,
(ix) Use less micro-oven,
(x)  Use a bicycle for short distances,
(xi) Reduce the energy use and its wastage.
(xii) Grow bamboos to reduce global warming as bamboo acts as a carbon sink and absorbs excess carbon dioxide.

KYOTO PROTOCOL: JAPAN 1-10 December 1997

Kyoto Protocol is a legally binding international agreement,
whereby all the participating nations will tackle global warming
by controlling greenhouse gas emissions.
 Average reduction 5.2% from 1990 levels by 2012.
Kyoto protocol limits greenhouse gas emissions by developed
and developing countries

 THE MONTREAL PROTOCOL DOES NOT COVER

GREEN HOUSE GAS EMISSION