Atmospheric Composition and Impact on the Environment

The branch of chemistry which deal with the study of the environment and the change that occurs in it is called environmental chemistry. OR The branch of chemistry deals with the study of all-natural systems. Their importance and the change occurring in them are called environmental chemistry.

The environment consists of four natural systems.

(i) Geosphere (earth)

(ii) Hydrosphere  (Water)

(iii) Atmosphere  (Air)

(iv) Biosphere  (All living organisms)

Atmosphere:- The protective blanket around the earth's surface is called the atmosphere. The mass of gases around the earth is called the atmosphere.

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Composition of Atmosphere

The atmosphere is a mixture of different gases like N2, O2, CO2, Ar, etc. Including water vapours and dust particles. The major constituents of the atmosphere are N2 (78%) and O2 (21%) and 99% atmosphere is made up of these two gases. The minor constituents of the atmosphere are CO2 and Argon and some tracer gases are present in the atmosphere. The mass of the atmosphere is approximately 4.5 to 5 x 10 power 15 metric tons. 

The density of the atmosphere is 0.0013 g/cm² and the temperature of the atmosphere varies from -92 to 1200 ०C. The pressure of the atmosphere at the sea level is 1.0 atm.

Types of air pollution

Layer of atmosphere

The atmosphere is divided into the following layers or structural zones. (i) Troposphere (ii) Stratosphere/ozonosphere (iii) Mesosphere (iv) Thermosphere

(i) Troposphere layer

The first layer of the atmosphere closest to the earth's surface is called the troposphere. 70 to 75% of the atmospheric gases are present in this layer. The major components of the troposphere are N2, O2, and CO2 water vapours etc., Average height of this layer is 11 Km at sea level but decreases at the poles. because the height depends on latitude season and pressure. The average temperature near the surface is 15 °C while the top temperature is -56 °C. 

The change in temperature with increase occurs with altitude. The temperature decreases at the rate of 6.5 °C per Km as the altitude increases. The change in temperature with an increase in height is called the lapse rate. Most of the weather phenomena like cloud formation wind reinstall snow take are negative.

(ii) Stratosphere layer

The second layer of the atmosphere which is above the troposphere is ozone (O3) therefore they are also called the ozonosphere. The average height of this layer is from 11 to 50 Km. The concentration of ozone increases with the increase in height. The maximum concentration of ozone is at the height of 30 Km. The temperature of the stratosphere in stratosphere increases from -56°C to -2°C with height due to the absorption of ultraviolet rays of the sun. Weather balloons and jet aircraft fly in this region because the air present in this layer is very thin, which increases the fuel efficiency of the aircraft. Its lapse rate is positive.

(iii) Mesosphere layer

The third layer of the atmosphere which is above the stratosphere is called the mesosphere layer. The major component of this layer is O3, NO. The average height of this layer is from 50 to 85 Km. The temperature of the mesosphere decreases from -2°C to -92°C with height due to the low concentration of ozone. Its lapse rate is negative.

(iv) Thermosphere layer

It is the fourth layer of the atmosphere, which is present above the mesosphere, the important component of the thermosphere is O2, NO, O, ions etc. The average height of this layer is from 85 to 500 km. It shows a positive lapse rate because temperature increases from -92 to 1200°C with an increase in height, due to the absorption of Ultraviolet light they undergo an ionization process and due to the presence of ions thermosphere is also called the ionosphere. 

Importance of the Atmosphere

The atmosphere plays an important role for living organisms, some of the importance of the atmosphere is given below.

(i) It protects all living organisms on the earth by absorbing dangerous cosmic rays of the Sun.

(ii) It plays an important role in maintaining heat balance on the earth.

(iii) Atmosphere is the main source of essential gases for life on Earth, for example, Oxygen is essential for all life on the Earth, and carbon dioxide is essential for photosynthesis in plants.

(iv) It maintains biogeochemical cycles like the Carbon cycle, Nitrogen cycle, Phosphorus cycle etc.

(v) It helps in radio communication.

(vi) It helps in the movement of aircraft.

(vii) It maintains the heat balance of the earth by absorbing the heat radiation re-emitted by the earth's surface.

(viii) The Atmosphere allows visible radiations coming from the Sun, as a result, we can see.

(ix) Ozone protects all kinds of life on the earth from the harmful ultraviolet rays of the Sun.

(x) It facilitates combustion and without an atmosphere, combustion is not possible. 

Types of Air Pollution

The substances released into the air either by human activity or by natural activities in sufficient concentration to cause harmful effects to human beings, vegetation and other living things is called air pollution.

Effect of air pollution on environment


The substances which cause pollution are called pollutants. These are substances in the air that can cause harm to humans and the environment, air pollutants can be classified into two types. 

(i) Primary pollutants

Those pollutants which are released directly into the air or directly produced from a process such as ash from a volcanic eruption, carbon monoxide from vehicle exhaust or sulphur dioxide released from factories etc. are called primary pollutants. 

Example:- SO2, SO3, CO2, NO2, and volatile organic. 

(ii) Secondary pollutants

Those pollutants which are formed from primary pollutants are called secondary pollutants. The most common secondary pollutants are certain gases that are synthesized by photochemical reactions. The Secondary pollutants are concentrated as they can be formed from many different types of compounds. Like phenomena of photo-chemical smog, sulfuric acid and nitric acid (acid rain), Particulate matter, peroxyacyl nitrates solar radiation etc. 

>Guidelines for Identification of Issues (Environmental Aspects and Health & Safety Risks)

Anthropogenic Air Pollution Sources 

(i) Particulate:- The man-made sources of particulate pollutants are the combustion of fuels, wood, meaning, mountain blasting, construction, industrial processes etc.

(ii) Oxide of carbon:- Most of the carbon dioxide produced by human activities of them are about 75% CO produced by automobiles. Incomplete combustions of fossil fuels petroleum production, iron and steel industries. Thermal power generation etc.

Anthropogenic air pollution sources

(iii) Oxide of nitrogen:- the man-made sources of nitrogen oxide are automobiles, industrial furnaces, thermal power, jet engines etc.

(iv) Oxide of sulphur:- About 33% of SOx pollution is caused by man-made sources, some of the major sources of Sox are the burning of fossil fuels, transportation, industries, and combustion of other sulphur-containing compounds.

(v) Volatile organic compounds:- Volatile organic compounds are produced by the burning of fossil fuel, meaning, the extraction of fossil fuel, and automobile exhaust.  

(vi) Chloro-fluoro carbons:- Chlorofluorocarbons are a group of compounds, which contain the elements chlorine, fluorine and carbon. The main source of CFCs are aerosols containing spray, and leakage from refrigerators and air conditioners.

Effect of Air Pollutant 

Some of the harmful effects on humans and the environment of air pollutants are given below.

Effect of carbon monoxide (CO)

Carbon monoxide is a colourless, odourless, non-irritating but very poisonous gas. It affects respiratory activity because haemoglobin has more affinity for CO to bind with itself than for oxygen. It damaged the central nervous system and heart. It causes blurred images, headaches, nausea etc.

Effect of carbon monoxide

Effect of carbon dioxide

The increase in the concentration of carbon dioxide causes global warming and disturbs the environment.

Effect of sulphur dioxide 

It causes respiratory problems, causes irritation of the eyes nose and throat. It reduces the productivity of plants. It causes yellowing and reduces the storage time of paper. It causes yellowing and damage to limestones and marbles. 

Effect of Chloro-fluoro

It destroys the ozone layer which then allows harmful ultraviolet rays to enter the atmosphere and their effect on the earth could be very dangerous.

Effect of particulate pollution

particulate matter, such as lead halide etc produced by the combustion of leaded gasoline products, which are toxic and affect humans and other living organisms. 

Effect of Chloro-fluoro

Environmental effect of air pollution

Acid Rain:- The rain having a pH value of less than 5.6 is called acid rain. It increases the acidity of water which causes waterborne diseases. It destroys vegetation and causes damage to human skin and hair etc. It damaged buildings and other materials made up of limestone and marble. 

 >Important role chemistry disadvantage

>Environmental Health & Safety Procedure Manual

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