Science of Ozone

THE SCIENCE OF OZONE

Ozone, though similar to oxygen chemically, is composed of three molecules of oxygen and is usually blue in color with a very strong odor. The atmosphere contains less ozone than the common oxygen. While out of every ten million air molecules, there exist about two million molecules of normal oxygen and only three molecules of ozone. Most of these ozone molecules are typically concentrated in the Stratosphere, the atmospheric layer that runs roughly from ten kms to about fifty kms in altitude. Even though the amount of ozone in the atmosphere is small, it plays a vital role in the atmosphere. The ozone layer protects the Earth and everything on it by absorbing the sun's UV radiation. When the ozone is not at an atmospheric level and is at ground level, ozone proves to have toxic effects.

'Inhaling fairly low amounts of ozone can result in signs and symptoms such as coughing, congestion, wheezing, shortness of breath, and chest pain in otherwise healthy people. People with already existing asthma, bronchitis, heart disease, and emphysema may find their conditions worsen while inhaling ozone. Breathing ozone may also increase the risk of getting certain lung diseases. People can recover from short-term exposure to low levels of ozone. However, breathing high levels of ozone or breathing low levels of ozone over a long period of time may have more damaging and longer-lasting effects.' Ozone has also been found to have positive effects on people. It has proven to be a very purifying substance. Doctors are now aware that it has three powerful properties:

1. It stimulates the immune systems through production of natural cancer-killing proteins called cytokines.

2. It improves oxygenation (delivery of oxygen to starved tissues) and metabolism.

3. It is a powerful antibiotic when applied locally.

Ozone is made naturally in the atmosphere or artificially by using high voltages or ultraviolet rays. Ozone and Oxygen work together efficiently to prevent the ultraviolet radiations reaching the earth's surface. The ultraviolet radiations with shorter wavelengths, such as wavelengths less than 242 nm, have sufficient energy to break the O-O covalent bonds in the oxygen molecules and are thereby used up by the oxygen molecules.

< 242 nm

O2 (g) ® 2O (g)

Similarly, ultraviolet radiations with higher wavelengths, for example more than 242 nm to 320 nm, are used up in breaking the bonds between the oxygen atoms in an Ozone molecule.

242-320 nm

O3 (g) ® O (g) + O2 (g)

As Oxygen cannot use up such higher wavelengths of the ultraviolet radiations, it is most important that the Ozone layer in the atmosphere is preserved without being destroyed. This process of ozone is called 'Photolysis' which is a continuous process so that ultimately the sun rays that reach humans are of less intensity. Otherwise, such high wavelengths of the ultraviolet radiations cause many adverse reactions to humans like skin cancers, skin aging and even the failure of crops.

But, Ozone, the protective shield of the earth has been observed to be depleting since several years. The first discovery of ozone depletion was in the Polar Regions of Antarctica and the North Pole. During winter the Polar Regions do not experience any sunlight, but the air present in these regions develops into strong winds called the 'Polar Vortex.' As the temperatures in these regions fall below certain range these winds start getting very cold and ultimately form clouds. These clouds are called the 'Polar Stratospheric Clouds' which are unusual in that they form nitric acid trihydrate. With the further drop in the temperatures the cold water present combines with the nitric acid. What are left over are chlorine atoms. This key important reaction leads to the loss of ozone in those regions.

This process requires cold conditions which favor the clouds to form which is why the Polar Regions were the first target. However, once these clouds are formed, depletion of ozone can take place even in warm conditions. These are some of the chemical reactions in the polar stratospheric clouds that were discovered by Mario Molina :

"Molina's chemical formulas are as follows:

(1) ClONO2 + HCl ice > Cl2 + HNO3

(2) Cl2 + hv -> 2 Cl

(3) Cl + O3 -> ClO + O2

(4) ClO + ClO + M -> Cl2O2 + M

(5) Cl2O2 + hv -> Cl + ClOO

(6) ClOO + M -> Cl + O2 + M

(M) is a "collision chaperone" (a hard surface) for N2 and O2, as put by Molina.

The "hv" stands for the ultraviolet rays that the sun puts out. The net result of this series of complex chemical reactions is two ozone molecules (O3) will be turned into three oxygen molecules (O2). This is the heart of the explanation that CFCs are depleting ozone in Antarctica. The so-called "chloro-catalytic process" has scared the hell out the common people.

There is, however, a major problem that has been ongoing for almost eighty years that is harmful to the ozone layer. This problem happens to be the manmade chlorofluorocarbons that we have been releasing into the air through many different means. The first CFC's were invented for the intentions of being used as a safe non-toxic gas in refrigerators. The previous refrigerant compounds used prior to the chlorofluorocarbons were sulfur dioxide and ammonia. These compounds were very good at keeping the refrigerators cold, but since the compounds were poisonous and hazardous to people's health they needed to be replaced. The CFC compounds that replaced the sulfur dioxide and ammonia compounds were much safer to the health of everyone.

In few years, the use of these compounds was extended to various other things like propellants in the aerosol cans, solvents, as expansions gases in the production of foams, as heat exchanging fluids in air conditioners, and as working fluids in refrigerators. These compounds are so very much useful as they are stable compounds with low toxicity and low flammability and do not react with other compounds. Chlorofluorocarbons are a family of compounds mainly containing chlorine, fluorine and carbon. Their main important properties