Ozone and Life on Earth

Ozone (O3) is a molecule composed and bonded of three oxygen atoms. Bonds between the oxygen atoms in the ozone molecule is rather weak compared to the oxygen molecule consists of two atoms (O2), so one of the three oxygen atoms easily escape and react with other molecules.

Ozone was first discovered by Christian Friedrich Schonbein in 1840. Naming ozone is derived from the Greek, ozein meaning smell. Ozone is known as a gas that has no color.

The use of ozone has been performed for more than a century ago. Ozone is used for various purposes, ranging from clean drinking water, sterilization of raw food materials, to elaborate a variety of toxic organic compounds contained in wastewater. In the field of medicine, ozone is more often used after the discovery of the ozone producing equipment for medical sterilization by J Hansler in the mid-20th century. However, ozone is a toxic substance. This gas is very reactive and corrosive (rapidly cause corrosion on metal) and hazardous to human health if inhaled in large quantities.

Ozone is found naturally in the stratosphere. Approximately ninety percent of Earth's ozone is in the stratosphere. Stratosphere is one of the layers of the earth's atmosphere at an altitude between 20-50 kilometers above the earth's surface. The ozone layer in the stratosphere was first discovered in 1913 by Charles Fabry (1867-1945) and Henri Buisson.

The ozone layer in the stratosphere naturally formed mainly through a process fotodisosiasi where the sun has a very important role in this process. Ultraviolet rays emitted by the sun was able to break an oxygen molecule (O2) to form two single oxygen atom. Then every single oxygen atom is bonded to an oxygen molecule to form a molecule of ozone (O3).

Diagram illustrating the ozone-oxygen cycle. (Picture from: http://commons.wikimedia.org/)

The presence of beneficial ozone in the stratosphere protects the earth from the dangers of ultraviolet emission (UV) excessive sun. This ozone protects life on earth by absorbing harmful ultraviolet radiation from the sun. Because it is protecting the ozone in the stratosphere that is also called good ozone.

Ozone in the stratosphere absorbs ultraviolet radiation emitted by the sun. This radiation has a wavelength below 400 nanometers. The spectrum of this radiation (located at wavelengths between 290 nanometers and 320 nanometers) or better known as UV-B radiation. Increasing doses of UV-B radiation reaching the earth resulting in increased cases of skin cancer, lower yields, and ruin the lives of plankton and fish larvae.

Reaction formation and decomposition of ozone occurs naturally in a state of balance and continuously for centuries. Most of the ozone is formed and decomposes in the equatorial region where there are tropical rainforests were quite extensive. By nature, nature has arranged transport phenomena that will bring the gases contained in the earth's surface to the layer above it and distribute ozone into the higher latitudes, and eventually accumulates in the polar regions.

The process of ozone depletion. (Picture from: http://sopf.org/)

However, the balance of the formation and decomposition of ozone has been disrupted due to the increase of ozone-depleting substances or materials (ozone depleting substances / ODS), so the rate of decomposition of ozone faster than the rate of its formation. Damaging substances / thinning of the ozone layer in the lower stratosphere is produced by human activities on the earth's surface. These substances are capable of spreading to the stratosphere. This causes a decrease in the concentration of ozone in the stratosphere.

Ozone depleting substances contain some combination of chemical elements chlorine, fluorine, bromine, carbon, and hydrogen are called halozarbon. The compound consists of only chlorine, fluorine and carbon called cholorofluorocarbon (CFC). CFCs are widely used because it is stable with low toxicity and non-flammable. Because CFCs have chemical and physical properties suitable for coolant, solvents, and heat insulation, this material is widely used by industrial refrigerator, AC (air conditioner), gas booster (spray), foam plastic, fire extinguisher material, the solvent in the industry, and electronic equipments cleaning. If this material is released into the atmosphere by atmospheric transport phenomena, these materials will be lifted and diffused into the stratosphere. In this layer the material will be dissociated by ultraviolet radiation from the sun and breaks down into chlorine gas was very active damaging the ozone layer.

The climate system is complex, meaning that the ozone hole does indirectly alter the surface temperature and climate of the Earth. (Picture from: http://theconversation.edu.au/)

The monitoring of the ozone layer in the stratosphere has long made the developed countries since 1957. In 1985, researchers from the UK found a reduction in the total amount of ozone in the stratosphere during the Antarctic spring. In 1987, a monitoring station in Antarctica recorded a decrease in the total amount of ozone to be less than half the amount of ozone measured in 1970. This drastic decrease in ozone depletion has caused or is called the ozone hole (ozone hole).

Global emissions of ozone-depleting chemicals (CFCs, halons, HCFCs, and others) and their non-ozone depleting substitutes (HFCs) from 1950 to 2050, expressed as Gigatonnes of CO2-equivalent per year. The blue hatched regions indicate the emissions that would have occurred, in the absence of the Montreal Protocol, with 2–3% annual production increases in all ozone-depleting chemicals. Shown for reference are emissions for the range of CO2 scenarios from the IPCC Special Report on Emission Scenarios. (Picture from: http://theconversation.edu.au/)

The discovery of the ozone hole has prompted the formulation of an international treaty known as the Vienna Convention 1985. The agreement aims to protect the environment and human health due to the depletion of the ozone layer. Then in 1987 established the Montreal Protocol. In the protocol was approved reduction and elimination of the production and consumption of CFCs, halon, and other similar substances that contribute to depleting the ozone layer. *** [THE CONVERSATION | SAVE OUR PLANET FOUNDATION | DEDE NURROSYID | PIKIRAN RAKYAT 13092012]

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