The Ozone Layer

What is ozone?

Ozone, or O3, is one of many trace gases that float around our atmosphere in minuscule quantities (trace gases are atmospheric gases that have concentrations normally measured in parts per million (ppm) or parts per billion (ppb)). Ozone is made from the oxygen atom (O2) through photochemical or electric discharge reactions. In the troposphere, the lowest level of our atmosphere, ozone is a pollutant. It is, however, also used for many commercial purposes - such as water purification and bleaching. So, why is this small molecule important at all?
As anyone experienced with atmospheric chemistry will know, it is the trace gases that play an important role in our climate and not the major atmospheric components (nitrogen, oxygen, carbon dioxide, and argon). Ozone is a prime example of this, as without ozone, it is unlikely that planet earth could so aptly host the peculiar thing that we call life. Why? Because of the ozone layer.

What is the ozone layer?

At roughly 30 kilometers above the earth's surface (in the middle of the stratosphere), [O3] (the concentration of ozone) reaches a maximum at roughly 10 ppm. This layer of increased concentration that envelopes the earth is collectively known as the ozone layer. The ozone reflects around 98% of the sun's ultraviolet radiation, thus shielding the planet's surface from the dangerous rays - UV radiation damages living tissue and overexposure often results in skin cancer.

Why do we care?

In 1970, atmospheric scientists began to express concerns that commercial gases, namely fluorocarbons used in aerosol cans and refrigerators, were destroying the ozone layer. By 1978, the use of fluorocarbons as propellants in aerosol cans had been banned. None-the-less, in 1985 a British study reported a hole in the ozone layer over Antarctica. This hole, actually a net thinning of the stratospheric ozone concentration, has been steadily increasing in size despite the efforts of scientists to press for stricter laws regarding the usage of fluorocarbons. Further studies have indicated that several other chemicals are also responsible for stratospheric ozone destruction, making the problem even more severe.


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