7.75 - Ozone Depletion

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Information about 7.75 - Ozone Depletion
Education

Published on December 9, 2008

Author: ecumene

Source: slideshare.net

Ozone Depletion You should know and understand; What is ozone, where does it occur and why is it important? The difference between good and bad ozone How human pollutants affect levels of stratospheric ozone leading to ozone depletion and the “ozone hole” The impact of ozone depletion on plants and animals How international treaties have addressed the ozone issue

You should know and understand;

What is ozone, where does it occur and why is it important?

The difference between good and bad ozone

How human pollutants affect levels of stratospheric ozone leading to ozone depletion and the “ozone hole”

The impact of ozone depletion on plants and animals

How international treaties have addressed the ozone issue

What is ozone, where does it occur and why is it important? Ozone is trioxygen (O 3 ) Ozone is found in both the troposphere (lower atmosphere) and the stratosphere In the stratosphere the ozone forms a “layer”, this layer is important as it protects us from UV radiation – ozone is responsible for filtering a very high percentage of UV radiation

Ozone is trioxygen (O 3 )

Ozone is found in both the troposphere (lower atmosphere) and the stratosphere

In the stratosphere the ozone forms a “layer”, this layer is important as it protects us from UV radiation – ozone is responsible for filtering a very high percentage of UV radiation

The difference between good and bad ozone The ozone is the stratosphere is GOOD ozone as it filters the UV radiation Ground level tropospheric ozone is BAD ozone as it can exacerbate asthma and cause other respiratory and associated health problems When you investigate urban microclimates and pollution you will study ground level ozone

The ozone is the stratosphere is GOOD ozone as it filters the UV radiation

Ground level tropospheric ozone is BAD ozone as it can exacerbate asthma and cause other respiratory and associated health problems

When you investigate urban microclimates and pollution you will study ground level ozone

Ozone Depletion Ozone is continually created and destroyed within the stratosphere (O+O 2 =O 3 +O=2O 2 +O=O 3 etc.) The total amount of ozone in the stratosphere is determined by the balance between photochemical production and recombination This good ozone in the stratosphere can be destroyed by ozone depleting substances (ODS) ODS include chlorofluorocarbons (CFCs), hydro-chlorofluorocarbons (HCFCs) and halons – these have anthropogenic sources such as coolants in air conditioning systems and propellants in aerosol sprays. Whilst the source of much of the worlds ODS has been removed (see Montreal Protocol below) it is worth remembering that 1 chlorine atom can destroy 100,000 molecules of ozone and these chlorine atoms stay in the stratosphere a long time.

Ozone is continually created and destroyed within the stratosphere (O+O 2 =O 3 +O=2O 2 +O=O 3 etc.)

The total amount of ozone in the stratosphere is determined by the balance between photochemical production and recombination

This good ozone in the stratosphere can be destroyed by ozone depleting substances (ODS)

ODS include chlorofluorocarbons (CFCs), hydro-chlorofluorocarbons (HCFCs) and halons – these have anthropogenic sources such as coolants in air conditioning systems and propellants in aerosol sprays.

Whilst the source of much of the worlds ODS has been removed (see Montreal Protocol below) it is worth remembering that 1 chlorine atom can destroy 100,000 molecules of ozone and these chlorine atoms stay in the stratosphere a long time.

The Ozone Hole Whilst CFCs and other ODS led to a depleltion in global stratospheric ozone levels this was not distributed evenly. In the tropics no noticeable declines have been recorded, whilst in middle latitudes declines of between 3 and 6% have been measured. Reactions that take place in polar stratospheric clouds speed up the depletion of ozone – thus levels of depletion of Antarctica (where such clouds are common) were much faster than elsewhere. This is where the concept of an “ozone hole” first emegred

Whilst CFCs and other ODS led to a depleltion in global stratospheric ozone levels this was not distributed evenly.

In the tropics no noticeable declines have been recorded, whilst in middle latitudes declines of between 3 and 6% have been measured.

Reactions that take place in polar stratospheric clouds speed up the depletion of ozone – thus levels of depletion of Antarctica (where such clouds are common) were much faster than elsewhere.

This is where the concept of an “ozone hole” first emegred

Ozone depletion over Antartica

The largest Antarctic ozone hole ever recorded (Sept 2006)

The Impacts of Ozone Depletion Less ozone = more UV penetration into the troposphere and lower atmosphere The most serious human impacts are skin cancer and cataracts Increased tropospheric UV radiation can lead to greater levels of BAD tropospheric ozone High levels of UV can also affect rice and plankton growth

Less ozone = more UV penetration into the troposphere and lower atmosphere

The most serious human impacts are skin cancer and cataracts

Increased tropospheric UV radiation can lead to greater levels of BAD tropospheric ozone

High levels of UV can also affect rice and plankton growth

1989 Montreal Protocol This is a good example of a successful international treaty to tackle a climatic hazard issue It has undergone 7 revisions since it was first ratified in 1989 Levels of CFCs and other ODS have declined Even with these success it will be 2050 before the ozone layer will have fully recovered

This is a good example of a successful international treaty to tackle a climatic hazard issue

It has undergone 7 revisions since it was first ratified in 1989

Levels of CFCs and other ODS have declined

Even with these success it will be 2050 before the ozone layer will have fully recovered

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