The atmosphere of the Earth is the air shell of the planet, which consists of gases and impurities, for example, dust, salts, combustion products or water, while their number is not a constant value, unlike the concentration of gases. Let us consider in detail the gas composition of the atmosphere in the percentage ratio: nitrogen - 78%, oxygen - 21%, xenon - 8.7%, hydrogen - 5%, nitrous oxide - 5%, also helium - 4.6%, neon - 1.8 %, methane - 1.7%, krypton - 1.1%, argon - 0.9%, water - 0.5% and carbon dioxide - 0.03%.
The composition of the atmosphere includes water vapor, which varies in space and time and is concentrated in the troposphere. Carbon dioxide also tends to change , its content directly depends on the vital activity of humans and plants. Aerosol particles formed as a result of human activity are often found in the troposphere and at great heights, but in the latter case they are in small doses.
Thus, the composition of the atmosphere varies with altitude. In layers that are close to the ground, the amount of carbon dioxide rises and oxygen decreases. In some places, the percentage of methane and other gases increases, which contribute to the destruction of the ozone layer, the appearance of the greenhouse effect and acid rain. About 10% of impurities enter the atmosphere as a result of natural processes. For example, during volcanic eruptions, ash, sulfuric and other acids, as well as toxic gases, enter it. Also, the source of sulfur is decaying plant debris, drops of sea water and forest fires. In addition, the latter contribute to the release of VOCs (volatile organic compounds). The remaining 90% of the impurities that make up the atmosphere come from human activities. This can be, for example, smoke emissions, soil erosion, waste storage, etc.
It should be noted that the atmosphere has five layers, the boundaries of which are determined by changes in the temperature regime, which depends on differences in the absorption of radiation.
So, gases enter the lower layer (troposphere) from the surface of the earth. The troposphere contains two main gas-forming components: nitrogen and oxygen. Also, this layer has a large amount of aerosols and water vapor coming from the evaporation of water from the surface of the oceans.
This is followed by the stratosphere, which has a composition similar to the troposphere. However, here the amount of water vapor is a thousand times less, and ozone is a thousand times more.
In addition, the atmosphere contains various substances that pollute it and have a harmful effect on living organisms. Let's consider some of them.
1. Sulfur gas enters the atmosphere during the evaporation of sea water, gas emissions and other natural processes, as well as the combustion of fuel. Here it reacts with water vapor and forms sulfuric acid.
2. Carbon monoxide is formed as a result of the combustion of wood, fuel and tobacco, as well as during the operation of an internal combustion engine.
3. VOCs (isoprene, terpen and methane) are formed due to the activities of chemical plants, thermal power plants, as well as the evaporation of moisture in rice plantations or swamps.
4. Nitric oxide (dioxide) is formed when there is a lack of oxygen as a result of fuel combustion, as well as with a large amount of exhaust gases and emissions from thermal power plants.
5. Photochemical oxidizing agents (PAN, formaldehyde and ozone) are formed as a result of chemical reactions involving solar radiation.
Thus, the earth’s atmosphere includes a large number of different elements and substances. Some of them are indispensable for maintaining the life of organisms on the planet, others play a detrimental role for them, contributing to their destruction. That is why it is necessary to ensure that the atmosphere does not receive a large amount of harmful substances that gradually destroy it.