Tabla de Contenidos
The most abundant gases in the Earth’s atmosphere depend on the region or layer of the atmosphere in which we find ourselves, and also on other factors. Likewise, the chemical composition of the atmosphere depends on temperature, altitude and proximity to water. Normally, the four most abundant gases are:
- Nitrogen (N 2 ) – 78.084%
- Oxygen (O 2 ) – 20.9476%
- Argon (Ar) – 0.934%
- Carbon dioxide (CO 2 ) 0.0314%
However, water vapor can also be one of the most abundant gases. The maximum amount of water vapor that air can hold is 4%, so water vapor could be number 3 or maybe 4 on this list. On average, the amount of water vapor is 0.25% at the level of the atmosphere, by mass (fourth most abundant gas). Warm air holds more water than cold air.
On a much smaller scale, near surface forests, the amount of oxygen and carbon dioxide can vary slightly from day to day.
Gases in the upper atmosphere
Although the atmosphere near the surface has a fairly homogeneous chemical composition, the abundance of gases changes at higher altitudes. The lower level is called the homosphere, it extends to approximately 80 to 100 km in height. Above it is the heterosphere or exosphere. This region consists of different layers of gases. The lowest level consists mainly of molecular nitrogen (N 2). Above it, there is a layer of atomic oxygen (O). At an even higher altitude, helium (He) atoms are the most abundant element. Beyond this point, the helium dissipates into space. The outermost layer is formed by hydrogen atoms (H), this part of the atmosphere is permanently ionized due to solar radiation. The ionized particles that surround the Earth in the outermost layer (ionosphere) are charged particles, not gases. The thickness and composition of the layers of the heterosphere or exosphere vary depending on solar radiation (day and night as well as solar activity).
References
http://www.caib.es/sites/atmosfera/es/la_atmosfera-3198/
