Air consists of oxygen, nitrogen, water vapor and other gases. In the cities, air is polluted and filled with exhaust gases, dust, ashes. As molecule of oxygen and nitrogen it is easier than molecules of harmful gases, air below is always more polluted.
Instruction
1. Air represents mix of gases. As a part of air there is a nitrogen in number of 78%, oxygen – 20%, argon – 0.9%, carbon dioxide, water vapor, hydrogen, ammonia, hydrogen sulfide, xenon, helium and other gases.
2. Oxygen is the most important element for life of all living organisms on the planet. Oxygen is absorbed by lungs of the person. The person exhales carbon dioxide which in total with water vapor increases air temperature.
3. Ozone is a barrier to aggressive ultra-violet radiation. Decrease in level of ozone can affect ruinously activity of organisms on Earth. Besides, ozone dilutes oxygen which is purely not suitable for life of living beings.
4. The amount of other gases in the atmosphere is small. However at excess of norms of threshold limit value of these substances the living organisms, and people in particular, can significantly suffer. So, allergic reactions of a human body are quite often connected with reaction to new substances which, thanks to technical progress, appear in the atmosphere.
5. Air in big cities, except basic elements, is filled with flying organic pollutant, toxic gases, tobacco smoke, a smog, exhaust gases of transport, dust and aerosols, bacterial pollutants, coal and adsorptive filters, viruses, bacteria, fungi, a mold.
6. Molecules of heavier gases accumulate below, and more lungs - rise up. As sulphurous and exhaust gases it is heavier than oxygen and nitrogen, the above there is a person, the better for him to breathe, for example, the freshest air in mountains. The amount of water vapor defines humidity of air. Even in the desert air contains water vapor, but in smaller quantities. On the contrary, water vapor contains in tropical forests much. The health of the person in any given conditions depends on amount of water vapor. So, at the minimum humidity it becomes difficult to breathe, and at high humidity high and low temperatures are very hard transferred.
7. Air on Earth has the identical chemical composition to an upper atmosphere - tropospheres. At the height over 18 miles there is a layer of hot air. Even above the layer called an ionosphere which consists of the particles electrified by the Sun is located. These particles form a layer of the plasma air protecting Earth from external magnetic field.