Depletion Of The Ozone Layer Essay Research

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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

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