The atmosphere Punjab Class 10 Notes Chemsitry Unit 14 Pdf Download | Chapter 14

The troposphere is the layer of the atmosphere closest to the Earth’s surface where the weather takes place. A small concentration of carbon dioxide and water vapour in the atmosphere plays a major role in regulating air temperature. They allow solar energy to pass through and absorb thermal radiation emitted from the planet’s surface. Therefore, these gases absorb much of the outgoing radiations and result in an increase in temperature. As the concentration of gases in the troposphere decreases rapidly with altitude, correspondingly the temperature also decreases at a rate of 6^oC per kilometre.

Sources of CO and CO₂ emissions
i) The largest human source of CO and CO₂ emissions is from the combustion of fossil fuels such as coal, petroleum and natural gas. Fossil fuels burnt in the combustion of automobiles or kiln of an industry emit CO and CO₂.
ii) Volcanoes emit clouds of dust and poisonous gases including CO and CO₂.
iii) Forest fires and burning of wood release CO₂ and CO. Emission of CO dominates in the limited supply of oxygen

Carbon dioxide (CO₂) gas acts as a glass wall of a greenhouse around the Earth. It allows the heat rays of the Sun to pass through it and reach the Earth. The Earth’s surface absorbs some of this energy and heats up. It cools down by giving off a different form of energy, called infrared radiation. But before all this radiation can escape to outer space, the increased concentration of CO2 in the atmosphere absorbs some of it, which makes the atmosphere warmer. Thus CO2 prevents heat energy from escaping from the atmosphere. So, CO2 is responsible for heating up the atmosphere. Exessive heating due to CO₂ is called global warming.

Carbon monoxide (CO) is a gas that has no odour, colour or taste and can be very dangerous to health. This means that we have no way to detect the problem until we become ill. CO can cause harmful health effects by reducing oxygen delivery to the body’s organs (like the heart and brain) and tissues. Exposure to higher concentrations of CO can cause headaches, fatigue and death. The initial symptoms are flu-like but without a fever. High-level poisoning can result in vomiting, loss of consciousness, shortness of breath and blurred vision.

SO₂ is a colourless gas with an unpleasant and irritating odour. It causes suffocation and severe respiratory problems to people suffering from asthma, bronchitis and emphysema.

Anaerobic decomposition of organic matter takes place in the absence of oxygen through bacterial activity. The main products of anaerobic decomposition are methane, CO₂ and H₂S.

Acid rain is formed when rainwater dissolves acidic air pollutants such as sulphur dioxide and nitrogen dioxide producing H₂SO₄ and HNO₃. Acid rain enters the soil and increases its acidity. Acid rain leaches many of the existing soil nutrients from the soil, which can seriously damage the roots of trees, thus, making it virtually impossible for them to survive. They get dry and die. It increases the toxic metals in the soil that poisons the vegetation.

Effects of ozone depletion
i) Depletion of ozone allows ultraviolet (UV) radiation of the Sun to reach the Earth that can cause harm to human health. Exposure to UV rays can result in skin cancers, sunburns and premature ageing of the skin.
ii) It can disrupt the food chain changing the lifecycle of plants.