Ozone layer. Part 2

Next up is Ozone depletion!..

Initially, it started as thinning of ozone layer... However, observations has shown a slow, steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere (the ozone layer) since the late 1970s. Durin the same period, stratospheric ozone over Earth's polar regions decline at a much larger, but seasonal, decrease. Latter phenomenon is commonly referred to as the ozone hole.

Cause of Ozone depletion

• Catalytic destruction by atomic chlorine and bromine, known as Halogen
• Main source: Ozone-Depleting Substances (ODS)
• Photodissociation of chlorofluorocarbon (CFC) compounds [aka freons]
• & Photodissociation of bromofluorocarbon compounds [aka halons]

*Photodissociation: chemical reaction in which a chemical compound is broken down by photons

* Photons: elementary particle, the quantum of the electromagnetic interaction, basic "unit" of light and all other forms of electromagnetic radiation

Photodissociation of chlorofluorocarbon (CFC) compounds

CFC → solar energy → Cl atoms

Chlorine atoms destroy ozone molecules:

Cl + O 3 → ClO + O 2

This process is especially troublesome because chlorine monoxide (ClO) reacts with other molecules of the same kind to generate more chlorine atoms:

ClO + ClO → Cl + Cl + O 2

Hence, once CFCs get into the stratosphere and break down, a continuous supply of chlorine atoms is assured where these chlorine atoms destroy ozone molecules.