[Chemistry Class Notes] on Atmospheric Pollutants Pdf for Exam

The surface of the Earth is surrounded by an atmosphere which has different thicknesses at different heights. There are different layers that constitute the atmosphere and each layer has a different density. The troposphere is the lowest layer of the atmosphere in which all the organisms live. It is extended around 10 km above the height of the mean sea level. Troposphere consists of air, clouds and water vapours. The next layer in the atmosphere is the stratosphere which tends to extend from roughly 10 to 50 km above the troposphere. It consists of the dioxygen, dinitrogen, and the ozone layer. The ozone layer is the one that tends to protect both humans and animals from the harmful UV rays of the sun. The pollution in these atmospheric layers refers to atmospheric pollution. It is caused by air or atmospheric pollutants and is known as the pollution of both troposphere and stratosphere. 

Today, in this article, you will all the notes for atmospheric pollution class 11 which includes what are the types of pollution including tropospheric pollution and the stratospheric pollution.

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Tropospheric Pollution

Tropospheric pollution is caused due to the presence of unwanted gaseous or solid components in the air. These pollutants are classified as follows:

1. Gaseous Pollutants: The oxides of nitrogen and sulphur, ozone, hydrocarbons, and several other oxidants tend to fall under this category. Let us learn more about these atmospheric pollutants in detail. 

a. Oxides of Sulphur: When we burn fossil fuel, the oxides of sulphur get produced. Sulphur dioxide is highly poisonous. Several studies show us that even a very low concentration of the gaseous sulphur dioxide tends to cause many respiratory diseases. Sulphur dioxide gets oxidized and changes to sulphur trioxide in the presence of the particulate matter.

2SO2 (g) + O2 (g) →  2SO3 (g)               

b. Hydrocarbons: Hydrocarbons tend to get formed through the incomplete combustion of the fuels. They are carcinogenic, which means that they tend to cause cancer. They are also very harmful to the plants since they tend to cause ageing, shedding of leaves, and the breakdown of tissues. 

2. Particulate Matter: Minute liquid droplets or solid particles that are suspended in the air are referred to as particulate matter. There are basically two different kinds of particulate matter which are viable and non-viable. The microorganisms like fungi and bacteria that are dispersed in the atmosphere are referred to as the viable particulates. The non-viable particulate matter is the one that is classified depending on the nature and size of the particles. Say, for example, smoke contains both solid and liquid particles that tend to get formed when the organic matter is combusted. Whereas, on the other hand, dust consists of fine particles that get produced when it is ground or crushed.

Stratospheric Pollution

The stratosphere layer of the atmosphere consists of the ozone layer that saves our planet from the harmful UV rays of the sun. UV radiation tends to split the dioxygen molecule into the free oxygen atom. These free oxygen atoms tend to combine with the dioxygen molecule and form ozone.

O2–  → uv O(g) + O(g)

O(g) + O2(g)  O3(g)

Ozone is unstable and tends to break down to the oxygen molecule. Chlorofluorocarbons are the primary reason for ozone depletion. They tend to react with the ozone which tends to form the oxygen molecule and chlorine monoxide radical. CFCs are the primary agents that produce the chlorine radicals in the layer of the stratosphere and tend to deplete the ozone layer. This depletion of the ozone layer is a serious threat to all the living organisms since ozone protects all the living organisms from the harmful sun rays that tend to cause skin cancer.