The average human will take approximately 15 breaths per minute, or 21,600 breaths per day, and not concern himself with the composition of the air he has breathed. Air is air, right? Read on to find out why air is not exactly the same everywhere on Earth.
The main components of air, nitrogen and oxygen, make up 99.0316 percent of the troposphere, the layer of the earth’s atmosphere that extends from the planet surface to a vertical distance of 23 to 60 thousand feet. Nitrogen in its gaseous state composes about 75 percent of our air. Oxygen, essential to life, makes up about 21 percent. We need the air we breathe to have at least a 19.5 percent oxygen content. Amounts below that level can cause physiological problems and oxygen levels below 16 percent can eventually kill.
Argon is the gas which is third highest on the air composition list. It, and neon, helium, krypton, and xenon, also part of the air we breathe, are noble’ gases. These noble’ or rare’ gases do not interact with much strength in chemical reactions with other elements; they are considered inert. Carbon dioxide, necessary to plant growth, and water vapor complete the standard list of gases in the air.
The degree to which these are present varies from location to location. Air composition is affected by different factors such as the direction from which the wind is coming, the time of day or year, biological or geological influences, and the amount of transportation emissions, agricultural activities, and industrial plants. Major forest fires and organic decomposition are examples of biological influences. A volcanic eruption with its soot, ash, and gaseous fumes is an example of a geological influence.
Iodine is sometimes found in air samples near the ocean and other salty waters due to evaporation. Methane (CH4), ozone (O3), nitrogen dioxide (NO2), nitrous oxide (N2O), sulfur dioxide (SO2), carbon monoxide (CO), and ammonia (NH3) have all been found in varying amounts in the air samples taken over industrial and agricultural areas.
Tiny particles of different elements are also in the air we breathe. Various studies have been done measuring particulate levels in the air over certain locations. A 1991 study of air samples over Saudi Arabia and Kuwait during the time of the oil well fires showed carbon and salt in the air as well as calcium and silica which came from the clay found in the landscape.
The El Paso-Ciudad Juarez area that is along the United States-Mexico border had air quality tests done for thirty years. A 1996 report indicated lead, copper, arsenic, and chromium were found in the air, and were present at their highest levels in the fall and winter months. These particulates were especially concentrated around three industrial sites.
A 1999 study done in eastern Egypt around a resort area showed lead, vanadium, cadmium, chromium, nickel, selenium, arsenic, and cobalt to be in the air samples taken. No reason was given for these elements to be present at detectable levels.
In summary, the air that you breathe has large amounts of nitrogen and oxygen, with smaller amounts of carbon dioxide, water vapor, noble gases, and particulates in it. The concentration of each of these is dependent upon several factors.
Resources:
http://chemistry.about.com/b/a/257751.htm
http://www.cfv.org/guides/3443.pdf
http://www.p2pays.org/ref/15/14671.pdf
http://www.gulflink.osd.mil/pm/pm_s03.htm#fig%201
http://www.fjokk.hu/cejoem/files/Volume5/Vol5No3-4/CE99_3-4-09.html
http://www.uigi.com/air.html
http://mistupid.com/chemistry/aircomp.htm
