Composition of atmospheric air and pollutants

The Air composition Is based on several components; 78% nitrogen, 21% oxygen, 1% argon and the rest of various noble gases that form l To the atmosphere that surrounds the Earth.

In some places, human activities have added other gases to the atmosphere, called pollutants.

Composition of atmospheric air and pollutants

Current air composition

  • Nitrogen : 78%. It dilutes oxygen and prevents rapid burning on the surface of the earth. Living things need it to produce proteins. Nitrogen can not be used directly from the air. The nitrogen cycle is the way in which nature supplies the nitrogen necessary for living things.
  • Oxygen : twenty-one%. It is used by all living beings, essential for breathing and necessary for combustion or burning.
  • Argon : 1%. It is used in light bulbs.
  • Carbon dioxide : 0.03%. Plants use it to produce oxygen. Carbon dioxide acts as a blanket and prevents heat from escaping into outer space. Scientists believe that the extraction of fossil fuels, such as coal and oil, adds more carbon dioxide to the atmosphere.
  • Water vapor : 0.0 to 4.0%. Essential for life processes. It also prevents the loss of heat from the earth.
  • Tracking gases Are gases that are found in very small amounts. They include neon, helium, krypton and xenon.

While the composition does not change much as they travel through the lower layers of the atmosphere, what changes is the number of molecules.

When they travel higher, the air molecules become less abundant. Although predominantly the same composition, there is a very important chemical difference within the stratosphere, because it is within this layer where the highest concentrations of ozone molecules reside.

In the stratosphere, ozone molecules - three oxygen atoms linked together - prevent some of the sun's most intense rays from reaching Earth's surface.

At present, NCAR (National Center for Atmospheric Research) scientists and researchers are monitoring this layer, which is so thin in the south pole that it is already called a"hole", and it is in this area where the molecules are being Destroyed.

Above the mesosphere, the composition changes. Although the mesosphere is still dominated by nitrogen and oxygen, the gases in the thermosphere are highly ionized and the bonds between the oxygen atoms are broken.

In the exosphere, the outer layer of the Earth's atmosphere, the air molecules can easily escape the Earth's gravity and float in space.

The atmosphere also contains a small but significant amount of carbon dioxide, about 0.04 percent, and small amounts of some other gases. In addition to these gases, air also contains water vapor. The percentage of water vapor varies from place to place and according to climatic conditions.

Contaminants in the air

The pollution adds additional molecules to the air, including carbon dioxide and ozone to the lower parts of the atmosphere. Although small amounts of both are natural at ground level in the troposphere, their amounts have increased due to the burning of fossil fuels.

Carbon dioxide

Carbon dioxide, a byproduct of burning, is called"greenhouse gas"because it contributes to global warming. Ozone emitted in the troposphere damages plants and causes respiratory problems, unlike the"good"ozone in the stratosphere that protects Earth from ultraviolet sunlight.

Human activities produce a series of gases that are released into the atmosphere. Factories can cause air pollution as well as burning of fuels, which releases a large amount of carbon dioxide into the atmosphere. It is believed that that is the cause of global warming.

Other oxides

Other polluting gases released into the air when fuels are burned include carbon monoxide, nitrogen oxides and sulfur dioxide. Incomplete combustion of fuels also releases small particles of solids (such as carbon) into the air.

Larger particles of contamination in the lower atmosphere can also cause breathing problems. Although aerosols are relatively small and ultra thin, emitted by the inflammation of fossil fuels and possibly trees and other vegetation, they can cause significant respiratory problems for some people.

How was the composition of the air discovered?

The first indication of the existence of argon was Sir Henry Cavendish In 1785. Cavendish was dissatisfied with what little was known about the air and was particularly dissatisfied with the lack of information on the fraction of air (most) that was not oxygen.

This scientist knew that nitrogen in the air could react with oxygen to ultimately form nitrous acid. Its objective was to find out if all the air that was not oxygen or carbon dioxide could be converted to nitrous acid, because in determining it, one could know if the air was totally oxygen, carbon dioxide and nitrogen.

Cavendish used an electric spark in the air to react oxygen and nitrogen to form nitrogen oxides. Thereafter, additional oxygen was added until all of the nitrogen had reacted.

Since the nitrogen oxides are acidic, Cavendish used aqueous sodium hydroxide to remove them and hence any carbon dioxide that was present. He removed the remaining oxygen using potassium polysulfides.

A small gas bubble remained (especially of argon) so Cavendish determined that this bubble"was not more than one hundred twenty of the air volume (nitrogen)"and therefore verified that the air is at least 99.3 percent of Nitrogen / oxygen / carbon dioxide with a maximum of 0.7 percent"something else".

Now we know that the 'something else' is argon and is very unreactive, which allowed Cavendish to find it, but also prevented him from finding out more about it. The giant advances in spectroscopy were made by Gustav Kirchhoff and Robert Bunsen 85 years later.

Important facts about oxygen

  • Oxygen is the third most abundant element in the mass universe.
  • Oxygen is the most abundant element in mass in Earth's biosphere.
  • The high concentration of oxygen in the atmosphere is a result of the Earth's oxygen cycle, which is predominantly driven by photosynthesis of plants.
  • Leonardo da Vinci Was the one who proposed for the first time that air is composed of two gases, one for breathing and the other for fueling the fire.
  • TO Joseph Priestley Is traditionally attributed to the discovery of oxygen in 1774.
  • Carl Wilhelm Scheele Possibly discovered oxygen the previous year, but his work was not published until after Priestly.
  • At normal pressure and temperature, the oxygen molecules bind to form dioxide, or O2, which is present in the atmosphere.
  • Due to its presence in the water, oxygen constitutes the bulk of the mass of all living beings.
  • It is used in cellular respiration for all types of life.
  • An allotro of oxygen is the ozone (O3) that forms the upper layer of atmospheric ozone and absorbs the UV radiation of the sun.
  • Oxygen can be produced for commercial use by the fractional distillation of liquefied air as well as other methods.
  • Under normal conditions, fresh water contains approximately 6.04 ml of oxygen per liter, while sea water contains approximately 4.95 ml of oxygen per liter.
  • Oxygen has a paramagnetic property (Paramagnetism is generated at the moment when the molecules of a substance have a permanent magnetic moment).
  • Oxygen plays an important role in the high concentration of life in the polar oceanic regions, since oxygen is soluble in water at extremely low temperatures.
  • It is believed that green algae and cyanbacteria are responsible for the production of up to 70% of free oxygen found in nature.
  • Free oxygen gas was almost non-existent on Earth before the appearance of photosynthetic organisms about 3.5 billion years ago.
  • Oxygen is commercially produced for a wide variety of industries and uses, including medical uses.

Important facts about argon

  • On a planetary scale, we can calculate that the Earth's atmosphere contains 65 billion metric tons of argon. That's more than 9 metric tons of argon per person on Earth.
  • Until 1957, the chemical symbol of argon was A. In 1957, IUPAC agreed that the symbol should change to Ar.
  • The dating of potassium-argon and argon-argon allows us to date the oldest rocks. The ratio of potassium-40 to argon-40 trapped in the rock can be used to determine how much time has passed since the rock has solidified.
  • The vast majority of argon on Earth comes from the radioactive disintegration of potassium-40, which produces stable argon-40. More than 99% of the argon of the Earth is argon-40.
  • Far from Earth, argon-36 is the most abundant isotope, synthesized in the silicon firing phase of stars with a mass of about 11 or more suns from Earth.

Important facts about carbon dioxide

  • The main function of the respiratory system of any living organism is to exchange oxygen and carbon dioxide. Carbon dioxide enters the body through the air it breathes. As blood is pumped through the pulmonary artery into the lungs, the blood releases carbon dioxide into the lungs and is the primary gas that is exhaled. About 0.3 liters of carbon dioxide is transferred from the bloodstream every minute.
  • If a living organism is locked in an airtight room, it will die of carbon dioxide poisoning before it dies by asphyxiation with oxygen.
  • The largest producer of man-made carbon dioxide gas is the combustion of fossil fuels, especially that produced by cars and industrial processes. However, natural processes such as decay of vegetation emit much more carbon dioxide into the atmosphere. Carbon dioxide is also released from the interior of the Earth through volcanic eruptions and huge bubbles that rise through the oceans.


  1. Stewart, D.. (2012). Composition of Air. 3-1-2017, from Chemicool.
  2. Sirois, M. (2009). Composition of the atmosphere. 3-1-2017, from Houston TeacherTECH Archives.
  3. BBC UK. (2014). The composition of air. 3-1-2017, from BBC.
  4. UCAR. (2014). Air pollution. 3-1-2017, from The National Center for Atmospheric Research.
  5. Braybury, L. (2014). Interesting Facts About Carbon Dioxide. 3-1-2017, from Qingdao Baigong Industrial And Trading Co., Ltd.

Loading ..

Recent Posts

Loading ..