Ozone Depletion Ozone (O3) is a triatomic molecule responsible for absorbing UV radiation in the stratosphere. It is produced by the breaking of chemical bonds in an oxygen molecule (O2) in a process known as photodissociation producing two single oxygen atoms which bind to oxygen molecules to form Ozone. Ozone buildup in the stratosphere was a result in increases in atmospheric oxygen concentrations two billion years ago in the Precambrian era where oxygen levels increased to between 5-18% at atmospheric level . There are four regions of UV radiation however, based on UV radiation interaction with biological matters, there are three sections of UV radiation, UV A (315-400nm), UV B (280-315nm) and UV C (100-280nm). UV radiation has little penetrating power and hence is usually linked to skin cancer (both melanoma and carcinoma). Suntans are the body’s natural defenses against UV radiation, melanin pigments in cells are activated and migrate to the surface of the skin, giving a darker complexion. Ozone screens UV B radiation and prevents penetration onto the Earth’s crust, preventing loss of marine life and skin cancer. This is done by absorbing UV B radiation by one of the Ozone’s Oxygen-Oxygen bonds, breaking it down to an oxygen molecule (O2) and an oxygen atom (O). The oxygen molecule then reacts with the oxygen atom reforming ozone molecules.
The theory of ozone depletion began with Dutch chemist, Paul Crutzen who published a paper suggesting that nitrogen oxide reduced the rate of ozone production. His theory believed that Nitrogen Oxide (NO) reacted free oxygen atoms in the atmosphere forming nitrogen dioxide (NO2).
Dr F. Sherwood Rowland and Dr Manuel E. Molina recognized the possibility for CFCs to become a major source of chlorine which could potentially break down ozone molecules in the stratosphere through UV radiation forming chlorine radicals. Chlorine radicals (Cl•) broke down ozone (O3) by taking an oxygen atom from ozone molecules forming chlorine monoxide (ClO). The chlorine monoxide then reacts with an oxygen atom to form an oxygen molecule and a chlorine atom, hence, the free chlorine radical is a catalyst itself. (fig.1.1) Rowland and Molina’s work was validated by the British Antarctic Survey in 1985 by the discovery of a hole in the ozone layer located in the polar region of Earth.
This process of ozone depletion can repeat itself over again and again, resulting thousands of ozone molecules converted into oxygen molecules by a single free radical. Over time, the continual usage of CFCs resulted in extensive damage in the ozone later creating holes, allowing lethal dosages of UV B radiation penetrating onto the earth’s surface, capable of destroying large amounts of marine plankton life up to 30 meters below sea level. The largest ozone hole is located in the polar regions of the Earth, especially in Antarctica (fig1.2), where a decline in marine life has occurred due to UV B radiation