What is the ozone depletion causes by?
Ozone depletion occurs when the natural balance between the production and destruction of stratospheric ozone is tipped in favour of destruction. Although natural phenomena can cause temporary ozone loss, chlorine and bromine released from man-made compounds such as CFCs are now accepted as the main cause of this depletion. Chlorofluorocarbons are not “washed” back to Earth by rain or destroyed in reactions with other chemicals. They simply do not break down in the lower atmosphere and they can remain in the atmosphere from 20 to 120 years or more. As a consequence of their relative stability, CFCs are instead transported into the stratosphere where they are eventually broken down by ultraviolet (UV) rays from the Sun, releasing free chlorine. The chlorine becomes actively involved in the process of destruction of ozone. The net result is that two molecules of ozone are replaced by three of molecular oxygen, leaving the chlorine free to repeat the process: Cl + O3 -> ClO + O2 ClO + O –
The depletion is reckoned to have been caused by the release of chlorofluorocarbon gases (CFCs) that used to be used (mainly) as a propellant in aerosol cans and as a coolant in refrigerators, freezers and air conditioning units. When released (as it used to be) CFC gas rose into the upper atmosphere where it broke down molecules of ozone. The ozone layer helps to protect earth from ultra-violet radiation. There are many old fridges and freezers around that still contain CFCs, which is why there are now legal restrictions on how these can be disposed of. As part of the approved disposal process, the CFC gas is drained into a sealed container.
