Air: What is, composition, functions, properties and pollution

Air is a gas mixture that form the Earth’s atmosphere forks essential for life On our planet. The main air composition includes nitrogen (around 78%), oxygen (approximately 21%) and a small amount of other gases such as argon, carbon dioxide and water vapor.

Oxygen is essential for breathing of living beings, while carbon dioxide is used by plants during photosynthesis to produce oxygen and energy. Nitrogen, although it is not reactive in its gaseous form, is vital for life since plants use it in the form of nitrogen compounds to grow and develop.

The composition of the air is quite stable in the troposphere, the lowest layer of the atmosphere, where life develops and meteorological phenomena occur. These are the components of the air:

Nitrogen (N2): 78%

It is the most abundant gas in the atmosphere. Although it is not reactive in its gaseous form, nitrogen is essential for the biosphere. Plants cannot use nitrogen directly from the air, but need to be fixed in compounds such as ammonia or nitrates, a process carried out by some specific bacteria and plants.

Here you can know the nitrogen cycle: what is, stages and importance and the function of nitrogen in plants and their importance.

Oxygen (O2): 21%

This gas is crucial for the breathing of most living beings, including humans. Oxygen allows combustion and is vital for metabolic processes that produce energy at the cellular level. Without oxygen, life as we know could not exist.

Argon (AR): 0.93%

Argon is a noble gas and, as such, it is chemically inert. Although it does not participate in important biological or chemical processes in the atmosphere, its stability makes it useful in industrial and scientific applications.

Carbon dioxide (CO2): 0.04%

Despite its small proportion, CO2 is crucial for photosynthesis, the process by which plants produce oxygen and energy. In addition, it is a significant greenhouse gas that contributes to global warming. Human activities, such as burning fossil fuels, have increased their concentration in the atmosphere, which has important climatic implications.

Water vapor (H2O): variable (0.1% to 4%)

The amount of water in the air varies according to temperature and humidity. Water vapor is essential for the water cycle and plays a crucial role in the regulation of earth temperature. It is also an important greenhouse gas.

• The air is fundamental for the survival of all living beings. Human beings and many animals depend on the oxygen present in the air to breathe. The plants, meanwhile, use carbon dioxide for photosynthesis, a process by which they convert solar energy into chemical energy. In this other post we tell you why air for living beings is important.
• It also acts as a Natural climate regulator and temperature of the planet. The Greenhouse gasessuch as carbon dioxide and water vapor, catch the heat of the sun, keeping the earth warm enough to support life. Without this layer of gases, temperatures would fluctuate dramatically, making life on the planet almost impossible. Here you can read about what are the greenhouse gases and where they come from.
• The Earth’s atmosphere filters the harmful solar radiation. The ozone layer, which is found in the stratosphere, absorbs and blocks most of the ultraviolet rays of the sun, thus protecting the living beings of their harmful effects, such as solar burns and skin cancer.
• The air movement, known as The windit is necessary to The distribution of heat and humidity throughout the planet. The winds help to balance temperatures and transport the clouds, which facilitates the distribution of precipitation and ensures that the different regions receive water, an essential resource for life.

The air has various physical and chemical properties that are fundamental for their behavior and for the multiple roles it performs in the environment and in everyday life. Among the physical properties we have:

• Colorless, toilet and tasteless: The air, in its pure state, has no color, smell or flavor, which makes it invisible and practically imperceptible to human senses under normal conditions.
• Density: The density of the air at sea level and a temperature of 15 ° C is approximately 1,225 kg/m³. Air density decreases with altitude, due to the decrease in atmospheric pressure and temperature.
• Pressure: Air pressure, also known as atmospheric pressure, is the force that air exerts on the earth’s surface. At sea level, standard atmospheric pressure is 1013.25 HPA (hectopascales) or 1 atm (atmosphere).
• Temperature: The air temperature varies widely depending on altitude, latitude and local climatic conditions. The temperature influences the density and air capacity to retain water vapor.

On the other hand, among the chemical properties of air we have:

• Reactivity: Although most air components are quite stable, some can react under certain conditions. For example, oxygen is an oxidizing agent that can react with other elements and compounds, a process that is essential for combustion and breathing.
• Solubility: Gases in the air are soluble in water in different degrees. Oxygen and carbon dioxide dissolve in water and are vital for aquatic life.
• Thermal conductivity: The air has low thermal conductivity, which means that the heat does not lead well. This makes it a good thermal insulator, which is why the air trapped in insulating materials helps keep heat.
• Refraction index: The air has a refractive index of approximately 1,0003. This value indicates how air folds the light that passes through it, which is fundamental for optical phenomena such as refraction and dispersion of light.

Air pollution is a significant environmental and public health problem that occurs when harmful substances are released in the atmosphere, affecting air quality. These substances can be of natural or anthropogenic origin (caused by human activities) and can have harmful effects for living beings and the environment.

Among the causes of pollution by the human being, we have the following:

• Transport: Motor vehicles emit nitrogen dioxide (NO2), carbon monoxide (CO), hydrocarbons (HC) and suspended particles, all of which contribute significantly to urban air pollution.
• Industry: Energy factories and plants release a variety of pollutants, including sulfur dioxide (SO2), nitrogen oxides (NOX), carbon monoxide (CO) and volatile organic compounds (COVS).
• Agriculture: The use of fertilizers and pesticides, as well as methane emissions (CH4) of farm animals, contribute to air pollution.
• Fossil fuel burning: Carbon, oil and natural gas burning in energy plants, homes and cars produces a large number of air pollutants.

On the other hand, natural pollution sources are:

• Volcanoes: Volcanic eruptions can release large amounts of sulfur dioxide (SO2), ashes and other pollutants in the atmosphere.
• Forest fires: Fire release particles, carbon monoxide (CO) and organic compounds in the air.
• Dust and sand: Dust and sand storms in arid regions can increase suspended particles in the air.
• Biogenic emissions: Plants and soils can also emit volatile organic compounds (COVS) and other gases.

In these other articles we explain what are the types of air pollution and solutions for air pollution.

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