Depletion Of The Ozone Layer Essay, Research Paper
The ozone bed diminishes more each twelvemonth. As the country of
polar ozone depletion ( normally called the ozone hole ) gets
larger, extra UV beams are allowed to go through through.
These beams cause malignant neoplastic disease, cataracts, and lowered unsusceptibility to
diseases.1 What causes the depletion of the ozone bed?
In 1970, Crutzen foremost showed that N oxides produced
by disintegrating azotic oxide from soil-borne bugs respond
catalytically with ozone rushing its depletion. His findings
started research on “ planetary biogeochemical rhythms ” every bit good as the
effects of supersonic conveyance aircraft that release N
oxide into the stratosphere.2
In 1974, Molina and Rowland found that human-made
CFCs used for doing froth, cleaning fluids,
refrigerants, and repellants transform into ozone-depleting
agents.3
Chlorofluorocarbons stay in the ambiance for several
decennaries due to their long tropospheric life-times. These compounds
are carried into the stratosphere where they undergo 100s of
catalytic rhythms with ozone.4 They are broken down into Cl
atoms by ultraviolet radiation.5 Chlorine acts as the accelerator
for interrupting down atomic O and molecular ozone into two
molecules of molecular O. The basic set of reactions that
affect this procedure are:
Cl + O3 & # 8211 ; & gt ; ClO + O2 and
ClO + O & # 8211 ; & gt ; Cl + O2
The net consequence:
O3 + O & # 8211 ; & gt ; 2O2
Chlorine is ab initio removed in the first equation by the
reaction with ozone to organize chlorine monoxide. Then it is
regenerated through the reaction with monoatomic O in the
2nd equation. The net consequence of the two reactions is the
depletion of ozone and atomic oxygen.6
Chlorofluorocarbons ( CFCs ) , halons, and methyl bromide are a
few of the ozone depletion substances ( ODS ) that break down ozone
under intense UV visible radiation. The Br and F in
these chemicals act as accelerators, reforming ozone ( O3 ) molecules
and monoatomic O into molecular O ( O2 ) .
In volcanic eruptions, the sulphate aerosols released are a
natural cause of ozone depletion. The hydrolysis of N2O5 on
sulphate aerosols, coupled with the reaction with Cl in HCl,
ClO, ClONO2 and bromine compounds, causes the dislocation of ozone.
The sulphate aerosols cause chemical reactions in add-on to
Cl and bromine reactions on stratospheric clouds that
destruct the ozone.8
Some ozone depletion is due to volcanic eruptions. Analysis
of the El Chichon volcanic eruption in 1983 found ozone
devastation in countries of higher aerosol concentration ( Hofmann and
Solomon, “ Ozone Destruction through Heterogeneous Chemistry
Following the Eruption of El Chichon ” ) . They deduced that the
“ aerosol atoms act as a base for multiphase reactions taking
to ozone loss. “ 9 Chlorine and bromine cooperates with
stratospheric atoms such as ice, nitrate, and sulphate to
rush the reaction. Sulphuric acid produced by eruptions enhances
the destructiveness of the Cl chemicals that attack ozone.
Volcanically flustered conditions increase Cl & # 8217 ; s breakdown
of ozone. Besides, Cl and Br react good under cold
temperatures 15-20 kilometres up in the stratosphere where minute
of the ozone is lost. This helps explicate why there is less ozone
in the Antarctic and Arctic polar regions.10, 11
The Antarctic ozone hole is the largest. A 1985 survey
reported the loss of big sums of ozone over Halley Bay,
Antarctica. The suspected cause was the catalytic rhythms
affecting Cl and nitrogen.12
Halons, an particularly powerful beginning of ozone depleting
molecules, are used in fire asphyxiators, refrigerants, chemical
treating. They are composed of Br, Cl, and C.
Most of the Br in the ambiance originally came from
halons
. Bromine is estimated to be 50 times more effectual than
Cl in destructing ozone.13
Insect fumigation, firing biomass, and gasolene use all
release methyl bromide into the air. Some is recaptured before
making the stratosphere by dirt bacteriums and chemicals in the
troposphere. The balance breaks down under exposure to
sunshine, liberating Br to assail the stratospheric ozone.
Annual atmospheric releases of methyl bromide include 20 to 60
kilotons from fumigation ( 50 per centum of the methyl bromide
used as a dirt fumigant is released into the ambiance ) , 10 to
50 kilotons from biomass combustion, and.5 to 1.5 kilotons from
leaded gasolene car fumes each twelvemonth. Marine works life
besides releases methyl bromide, but most is recaptured in saltwater
reactions.14, 15
Hydrochlorofluorocarbons ( HCFCs ) and HFCs ( HFCs )
are being used as replacements to replace CFCs.
They “ still incorporate Cl atoms that are responsible for the
catalytic devastation of ozone but they contain H which
makes them vulnerable to the reaction with hydroxyl groups ( OH )
in the lower atmosphere. ? The reactions in the troposphere remove
the Cl before it reaches the stratosphere where ozone
depletion occurs.16
Some of the HFCs and HCFCs being used to replace Chlorofluorocarbons are
HFC-134a, HCFC-22, HCFC-141b and HCFC-123. HFC-134a replaces CFC-
12 in most infrigidation utilizations. HCFC-22 is marketed as a coolant
for commercial and residential air-conditioning systems. HCFC-
141b and HCFC-123 are used for doing urethane and other foams.1
Each twelvemonth since the 1970s, the stratospheric ozone above
Antarctica disappears during September and reforms in November
when ozone-rich air comes in from the North. Because new
chemicals that do non destruct ozone are replacing ozone-depleting
chemicals, the ozone hole is projected to vanish by the center
of the 21st century.18
Mentions:
1. Monastersky, R. ( 1992, September 19 ) . UV jeopardy: Ozone
lost versus ozone gained. Science News, 142, pp. 180-181.
2. Lipkin, R. ( 1995, October 21 ) . Ozone Depletion research
wins Nobel. Science News, 148, pp. 262
3. Lipkin ( ibid. )
4. Consortium for International Earth Science Information
Network ( CIESIN ) ( 1996, June, Version: 1.7 ) . Chlorofluorocarbons
and Ozone Depletion. hypertext transfer protocol: //www.ciesin.org/TG/OZ/cfcozn.html
5. CIESIN ( 1996, June, Version: 1.7 ) . Production and Use of
Chlorofluorocarbons. hypertext transfer protocol: //www.ciesin.org/TG/OZ/prodcfcs.html
6. CIESIN ( 1996, June, Version: 1.7 ) . Ozone Depletion
Procedures. hypertext transfer protocol: //www.ciesin.org/TG/OZ/ozndplt
7. US Environmental Protection Agency ( 1996 ) . Ozone
Depletion Glossary. hypertext transfer protocol: //www.epa.gov/ozone/defns.html
8. National Oceanic and Atmospheric Administration ( 1994 ) .
Scientific Assessment of Ozone Depletion-Executive Summary.
hypertext transfer protocol: //www.al.noaa.gov/WWWHD/pubdocs/Assessment94/executive-
summary.html # A
9. CIESIN ( 1996, June, Version 1.7 ) . Ozone Depletion
Procedures. ( ibid. )
10. National Oceanic and Atmospheric Administration ( 1994 ) .
Scientific Assessment of Ozone Depletion-Executive Summary.
( ibid. )
11. Kerr, Richard A. ( 1994, October 14 ) . Antarctica Ozone
Hole Fails to Recover. Science, 266, pp.217
12. Kerr, Richard A. ( ibid. )
13. US Environmental Protection Agency. Ozone Depletion
Glossary. ( ibid. )
14. Adler, T. ( 1995, October, 28 ) . Methyl Bromide doesn & # 8217 ; T
stick around. Science News, 148, pp. 278
15. National Oceanic and Atmospheric Administration ( 1994 ) .
Scientific Assessment of Ozone: 1994-Executive Summary. ( ibid. )
16. CIESIN ( 1996, June, Version: 1.7 ) . Ozone Depletion
Procedures. ( ibid.
17. CIESIN ( 1996, June, Version: 1.7 ) . Ozone Depletion
Procedures. ( ibid. )
18. Monastersky, R. ( 1995, October 14 ) . Ozone hole reemerges
above Atlantic. Science News, 148, pp. 245-246