Holes in the Ozone Layer

Holes in the Ozone Layer

Ozone, 03 is a highly important component of the earth's atmosphere.

Close to the ground ozone, is produced by the action of light on

exhaust fumes and so concentrates in areas of heavy traffic. In this

was it can be a pollutant, it corrodes metal, can inhibit plant growth

and cause irritation to the lungs and throat. Up in the stratosphere

though, about 15-50km above the earth surface, ozone is beneficial as

it intercepts much of the suns UV (ultraviolet) radiation that would

otherwise reach the earth. Over exposure to UV causes damage to DNA in

cells and increases chances of mutations. It can reduce the metabolism

of plants and algae as well as increasing chances of skin cancers and

cataracts in animals and humans. Its also believed UV radiation may do

harm to the immune system. The true extent of the damage excess UV

radiation does is not really known but there is some evidence that it

can cause higher mortality rates in young amphibians and fish. Algae

are at the base of the marine food web and so damage to them can cause

long lasting harm to marine ecosystems.

Ozone in the stratosphere is caused by the photochemical reaction of

oxygen in sunlight, and is formed in greater amounts around the

tropics where sunlight is strongest.

The least amount of ozone is found around the poles when they are in

darkness. In the mid-1980's it was shown that measurements were

showing decreasing amounts of ozone above the Antarctic. This

depletion of ozone eventually became a large hole by the early 1990's,

and this same series of events has recently been observed to be

occurring over the arctic. In fact ozone depletion has even occurred

at lower latitudes and exposure to sunlight is not recommended in the

UK without UV protecting sun cream.

The depletion of ozone comes from chemical emissions, which then react

in the stratosphere breaking down ozone. The worst of these chemicals

are called halocarbons and include CFC's (chlorofluorocarbons) but

nitrous oxide and methane also deplete ozone.