Introduction

Ozone – Where and What is it?

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Ozone is a gas made up of three oxygen atoms (O3) which is naturally found in small amounts in the stratosphere. Ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation. In the troposphere near the Earth’s surface, ozone is formed through chemical reactions between air pollutants from vehicle exhaust, gasoline vapors, and other emissions. At ground level, high concentrations of ozone can be deadly to both people and plants.

90% of ozone in the atmosphere is found in the stratosphere. The natural level of ozone in the stratosphere is a result of a balance between sunlight that creates ozone and chemical reactions that destroy it. The typical formation of ozone is as shown below:

Ozone is created when sunlight splits apart oxygen molecules into single oxygen atoms. Single oxygen atoms can re-join to make O2, or they can combine with O2 molecules to make ozone (O3). Ozone is destroyed when it reacts with molecules containing nitrogen, hydrogen, chlorine, or bromine. Some of these molecules that destroy ozone occur naturally, but since the beginning of the Industrial Revolution, humans have upset the proportion of these molecules in the atmosphere. These increased levels of human-produced gases such as CFCs (chlorofluorocarbons) have caused increased rates of ozone destruction, upsetting the natural balance of ozone, and leading to a reduction in the level of stratospheric ozone.

This is alarming because stratospheric ozone is required to absorb the Sun’s UV radiation to protect Earth. UV radiation can be classified into 3 types, namely: UV-A, UV-B and UV-C, based on their wavelength and the danger posed to humans. UV-A has the longest wavelength of 400nm – 315nm, which causes tanning and premature skin aging. UV-B has a medium wavelength of 315nm – 280nm and prolonged exposure can cause sun burn, cataracts and even skin cancer. UV-C has the shortest wavelength of 280nm – 200nm, and is the most dangerous of the UV spectrum. However, stratospheric ozone can successfully absorb almost all UV-C rays.

As mentioned above, ozone plays an important role in our everyday lives and extra effort must be made to protect our environment, so that it can protect us. The following sections, will cover in greater detail the chemical concepts of ozone, the impacts of ozone depletion on human health, and the efforts made to protect the ozone layer.

Reference:
https://ozonewatch.gsfc.nasa.gov/facts/SH.html