We are here with you hands in hands to facilitate your learning & don't appreciate the idea of copying or replicating solutions. Read More>>

Looking For Something at vustudents.ning.com? Click Here to Search

www.bit.ly/vucodes

+ Link For Assignments, GDBs & Online Quizzes Solution

www.bit.ly/papersvu

+ Link For Past Papers, Solved MCQs, Short Notes & More


Dear Students! Share your Assignments / GDBs / Quizzes files as you receive in your LMS, So it can be discussed/solved timely. Add Discussion

How to Add New Discussion in Study Group ? Step By Step Guide Click Here.

The Causes of Ozone Depletion

Scientific evidence indicates that stratospheric ozone is being destroyed by a group of manufactured chemicals, containing chlorine and/or bromine. These chemicals are called "ozone-depleting substances" (ODS).

ODS are very stable, nontoxic and environmentally safe in the lower atmosphere, which is why they became so popular in the first place. However, their very stability allows them to float up, intact, to the stratosphere. Once there, they are broken apart by the intense ultraviolet light, releasing chlorine and bromine. Chlorine and bromine demolish ozone at an alarming rate, by stripping an atom from the ozone molecule. A single molecule of chlorine can break apart thousands of molecules of ozone.

What's more, ODS have a long lifetime in our atmosphere — up to several centuries. This means most of the ODS we've released over the last 80 years are still making their way to the stratosphere, where they will add to the ozone destruction.

The main ODS are chlorofluorocarbons (CFCs), hydrochlorofluorcarbons (HCFCs), carbon tetrachloride and methyl chloroform. Halons (brominated fluorocarbons) also play a large role. Their application is quite limited: they're used in specialized fire extinguishers. But the problem with halons is they can destroy up to 10 times as much ozone as CFCs can. For this reason, halons are the most serious ozone-depleting group of chemicals emitted in British Columbia.

Hydrofluorocarbons (HFCs) are being developed to replace CFCs and HCFCs, for uses such as vehicle air conditioning. HFCs do not deplete ozone, but they are strong greenhouse gases. CFCs are even more powerful contributors to global climate change, though, so HFCs are still the better option until even safer substitutes are discovered.

The Main Ozone-Depleting Substances (ODS)

  • Chlorofluorocarbons (CFCs)
    • The most widely used ODS, accounting for over 80% of total stratospheric ozone depletion.
    • Used as coolants in refrigerators, freezers and air conditioners in buildings and cars manufactured before 1995.
    • Found in industrial solvents, dry-cleaning agents and hospital sterilants.
    • Also used in foam products — such as soft-foam padding (e.g. cushions and mattresses) and rigid foam (e.g. home insulation).
  • Halons
    • Used in some fire extinguishers, in cases where materials and equipment would be destroyed by water or other fire extinguisher chemicals. In B.C., halons cause greater damage to the ozone layer than do CFCs from automobile air conditioners.
  • Methyl Chloroform
    • Used mainly in industry — for vapour degreasing, some aerosols, cold cleaning, adhesives and chemical processing.
  • Carbon Tetrachloride
    • Used in solvents and some fire extinguishers.
  • Hydrofluorocarbons (HCFCs)
    • HCFCs have become major, “transitional” substitutes for CFCs. They are much less harmful to stratospheric ozone than CFCs are. But HCFCs they still cause some ozone destruction and are potent greenhouse gases.

Source: http://www.bcairquality.ca/101/ozone-depletion-causes.html

+ How to Follow the New Added Discussions at Your Mail Address?

+ How to Join Subject Study Groups & Get Helping Material?

+ How to become Top Reputation, Angels, Intellectual, Featured Members & Moderators?

+ VU Students Reserves The Right to Delete Your Profile, If?


See Your Saved Posts Timeline

Views: 376

.

+ http://bit.ly/vucodes (Link for Assignments, GDBs & Online Quizzes Solution)

+ http://bit.ly/papersvu (Link for Past Papers, Solved MCQs, Short Notes & More)

+ Click Here to Search (Looking For something at vustudents.ning.com?)

+ Click Here To Join (Our facebook study Group)

Comment

You need to be a member of Virtual University of Pakistan to add comments!

Join Virtual University of Pakistan

Comment by zain ul abdin(mit final) on March 29, 2013 at 7:32am

Latest Activity

Siddiq khan kakar replied to + M.Tariq Malik's discussion Instructions About Mid Papers For Newly Admitted Students:
19 minutes ago
Rana Ali commented on Isha Chuhdary's blog post Moka
28 minutes ago
Rana Ali liked Isha Chuhdary's blog post Moka
28 minutes ago
Butt G updated their profile
41 minutes ago
Rana Ali replied to Rana Ali's discussion تمہیں دل لگی بھول جانی پڑے گی
47 minutes ago
+ ! ❤SΕNSΙТΙVΕ(∂ΕSΕЯТ ΡЯΙNCΕSS)❤ replied to +¢αяєℓєѕѕ gιяℓ's discussion Galat fehmi..
57 minutes ago
+ ! ❤SΕNSΙТΙVΕ(∂ΕSΕЯТ ΡЯΙNCΕSS)❤ liked +¢αяєℓєѕѕ gιяℓ's discussion Galat fehmi..
57 minutes ago
Profile Iconsanaakram, junaid farid, Sundas Shaban and 5 more joined Virtual University of Pakistan
1 hour ago
Mani Siddiqui BS VIII posted a status
"انسانی اِیجادات میں خطرناک ایجاد عارضی انسانی تعلقات ہیں"
6 hours ago
Madeha Naqvi liked fairy's discussion QUIZ NO 1:
7 hours ago
hafsa badar posted a discussion
7 hours ago
Saqib liked +¢αяєℓєѕѕ gιяℓ's discussion Galat fehmi..
8 hours ago

Today Top Members 

© 2019   Created by + M.Tariq Malik.   Powered by

Promote Us  |  Report an Issue  |  Privacy Policy  |  Terms of Service

.