One of the major parts of the environment is the atmosphere. This is the layer of gases which surround Planet Earth. It is essentially a mixture of gases and the composition of this mixture changes as the atmosphere interacts with the earth's crust and the hydrosphere.
Nitrogen and Oxygen
The atmosphere is 78% nitrogen and 21% oxygen, so these gases play an important role in the chemistry of the atmosphere, but the gases that make up the remaining 1% such as carbon dioxide, water vapour and oxides of sulfur and nitrogen, also play large parts.
Respiration and Photosynthesis
Oxygen is the gas that makes Earth special. Life on earth depends on the availability of oxygen. The reaction cycle between oxygen and carbon dioxide is foundational to all living organisms. Oxygen is removed from the atmosphere by the oxidation of organic matter, decaying plants and animals, and respiration in living things. These processes form carbon dioxide, which is used by plants on earth and in the sea to form energy producing sugars and oxygen in the process known as photosynthesis.
Nitrogen Fixation
Nitrogen is a very unreactive gas, but it is also a vital constituent of living processes. Nitrogen has to be “fixed” or turned into more reactive chemicals such as ammonia and nitrates. This is done industrially in the Haber process, but naturally organic compounds such as amino acids are formed first and then “mineralised” into inorganic nitrogen compounds.
Water Cycle
A constantly changing component of the atmosphere is its water content. The “Water Cycle”, which is so important to the world's climate, involves the flux of water from the oceans, into the atmosphere and back to the oceans via streams and rivers. When there is too much or not enough water, environmental catastrophes will occur.
Greenhouse Effect
The final aspect of the chemistry of the atmosphere is the effect of the activities of human beings. Over the past century there has been a steady increase in industrial emissions into the atmosphere, especially as a result of burning fossil fuels. One of the major products of this activity is carbon dioxide gas, which is known as a “greenhouse gas”. Although it is not poisonous, if it is not removed by photosynthesis, this gas can collect in the atmosphere and prevent reflected heat from the earth dissipating into space. Many scientists predict that this will result in a change in climate all over the planet.
Acid Rain
Another important gas which is produced as a result of combustion of fossil fuels is sulfur dioxide. This is one of the main causes of “Acid Rain”, because when it dissolves in the water in the atmosphere it forms an acidic solution which, when it rains, can damage trees and other plants.
One of the main tasks of an atmospheric chemist is to develop models of the interactions of all these constituents in the atmosphere, as well as their interaction with the other parts of the environment, so that we will be able to predict what may happen when changes occur.
Most of the information in the article came from:
Environmental Chemistry, Raiswell, Brimblecombe, Dent & Liss, Edward Arnold, London 1980
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