AIR AND ATMOSPHERE

AIR AND ATMOSPHERE

Air is mainly a mixture of two gases, nitrogen and oxygen. Air is invisible, colorless and tasteless. Air has weight and exerts pressure. Air is an extremely important natural resource. Air is necessary for all the living organisms. This is because all the living beings breathe air. In fact, air is the best medium for the respiratory process. The terrestrial organisms can get oxygen necessary for respiration from air. A man respires about 22000 times a day and takes about 16 kg of air into body during this process. 

 The air present above the surface of the earth is its gaseous components which forms an invisible cover around the earth. The region of air present around the earth is called the atmosphere. The density of air is highest near the sea-level and as we go higher above the sea level, the density of air goes on decreasing. The atmosphere extends about 50 kilometers from the surface of the earth. The composition of atmospheric of atmospheric air also changes with the change in altitude. There are several concentric layers in the vertical profile of the atmosphere. The main layers of the atmosphere are: 

i) Troposphere

ii) Stratosphere

iii) Mesosphere

iv) Thermosphere

Role of atmosphere is to protect the living things from harmful radiation like ultra-violet reys by forming an ozone layer. Ozone is a gas whose one molecule contains three atoms of oxygen. At a height about 16 kilometers from the earth, the sun-rays convert the oxygen present there into ozone. The proportion of ozone gas in the atmosphere increases up to a height of about 23 kilometers.

The air particulates: the finely divided solid or liquid particles suspended in air are called particulates. Some of the examples of particulates present in the atmosphere are; dust, smoke, fumes, mist, spray are liquid particulates. Some more examples of particulates in the atmosphere are; spores, pollen grains, bacteria, fungi, virus, fur, hair, sand, sodium chloride, pesticides, insecticides, cement dust, lead dust, mercury dust and asbestos dust.

The particulate pollutants cause various allergic reactions, produces disease like bronchial asthma and tuberculosis. It reduces the visibility by producing haze in the atmosphere. This hinders road and air traffic. The particulates like smoke blacken the buildings and white clothes. The aerosols like fog can absorb and concentrate poisonous gases in the atmosphere and cause more serious air pollution like smog. Smog produces diseases like bronchitis, asthma and heat related disorder. It causes irritation to the eyes, nose and throat. Smog has an adverse effect on the growth and development of plants and reduces the visibility to very low level and hence causes the disruption of road and air traffic too. 

Lead is a very poisonous metal. Even a very low concentration of lead in the human body can create metabolic disturbances. Due to the prolonged effect of lead in the human body, malformation of red cells lead to a disease called anemia. Lead gets bound with the cellular enzymes and disrupts the functioning of cells and organs of the muscular dust cause lung cancer and asbestos.

Air pollution is the unwanted substances present in the air that affects the environment. The substances which pollute the air are called air pollutants. Air pollution is caused due to natural processes, human activities, and radioactivity. We all know about natural process and human activities and radioactive pollution is the phenomenon in which the nuclei of atoms of certain elements undergo spontaneous disintegration and emit alpha particles, beta particles and gamma rays. The sources of radioactive pollution are of two types and they are natural and man-made. The natural sources are mainly the naturally occurring radioactive elements and their compounds and the man-made are those which can be mining and refining of radioactive materials like nuclear weapons and so on.