Environmental Chemistry

  • Environment means all that environs i.e. surrounds us. Different organisms live in different types of surroundings such as air, water and soil. Different kinds of living organisms share these surroundings with other. An environment can be defined as the sum total of all conditions and influences which affect the development and life of all organisms on earth. It is the sum of living (biotic) and non-living (abiotic) components.
  • Broadly environment consists of two parts a) physical or abiotic (non-living) components and b) living or biotic components.
  • Abiotic components of the environment are air, water, soil, energy radiation, etc. Biotic components of the environment are microbes (such as bacteria, algae and fungi), plants, animals, etc.
  • Environmental chemistry deals with the study of the origin, transport, reactions, effects and fates of chemical species in the environment.

Components of Environment:


  • All the parts of the earth are not suitable for survival of organisms. Some parts are too hot or very cold to support life. The part of the earth on which organisms can survive and reproduce is called biosphere. A perfect and delicate balance is needed between the organism and other components of environment for the survival of the organism. A disturbance, damage or abrupt change in the quality of environment poses a threat to the survival and well-being of organisms.


  • The atmosphere is a thin layer of air (a mixture of gases) around the earth which is a great source to all living organisms.
  • The atmosphere is important for the survival of organisms because this is the layer which consists of free oxygen and water vapour. It also consists of nitrogen which is fixed in the soil in nitrification and used by plants.


  • Hydrosphere is the part of the earth on which all types of water resources exist, viz., oceans, seas, rivers, lakes, glaciers, ice caps, groundwater, etc. After oxygen water is needed by the organisms for their survival.


  • The lithosphere is the part of the earth where all types of minerals, metals, organic matters, rocks, soils, etc. exist. The soil is part of the lithosphere.

Environmental Pollution:

  • The word pollution is derived from the Latin word pollutionem which means to soil. The waste generated through human activities and spoiling the natural environment is termed as pollutants. Pollution is defined as the deterioration or unclean objectionable conditions in the quality of natural resources such as air, water and soil because of the action or presence of unwanted substances beyond a certain limit. Thus pollution creates an unwanted effect on our surroundings that have harmful effects on animals, plants and human beings.

Causes of Pollution:

  • In ancient times civilizations developed along the river banks. The ecosystem was sufficient to cater the needs of those civilizations. But due to the rapid growth of population people were forced to move away from river banks to other places. For creating shelter natural resources such as trees and soil were used. For comfort, humans started manufacturing industries. The industrial waste aggravated the problem of pollution. To cater food requirement of increasing population more food was required. Hence to increase agricultural yield pesticides and chemical fertilizers were manufactured and were used in excess quantity. All these wastes find its way to water sources such as sea, river, lakes and ponds and affected the aquatic organisms. It decreased the supply of potable water.
  • The causes of pollution can be summarized as follows
    • Rapid industrial population growth and urbanization.
    • Rapid industrial and technological growth led to the increase in the release of poisonous matter in the air, water and soil. Excessive use of the automobiles is also a major cause.
    • The manufacturing of drugs, antibiotics, pesticides, fungicides, herbicides etc. aggravated the pollution problem.
    • Excess use of chemical fertilizers and pesticides in agriculture,
    • A large release of industrial effluents and emissions from industries, power projects, etc.
    • Radioactive waste released from nuclear power plants add tests is hazardous because it shows its effect in future generations.


  • Pollutants are defined as the substances or the effect introduced into the environment in significant amounts in solid, semisolid, liquid gas or sub-molecular particle form due to which there is a detrimental (bad) effect on the environment.

General Classification of Pollutants:

Physical Pollutants:

  • Noise, radiation, unpleasant odours, heat, etc.

Chemical Pollutants:

  • Harmful gases like CO2, CO, SO2, H2S, S, NO, NO2, hydrocarbons, etc. carbon and dust particles, heavy metals, insecticides, pesticides, herbicides, petroleum products, soli and liquid waste, radioactive substances, etc.

Biological Pollutants:

  • pollen grains, microorganism, overpopulation

Classification of Pollutants on The Basis of The Origin:

Natural Pollutants:

  • Fires in forests may be caused by lightning strikes produces a large amount of CO2 which is released into the atmosphere.
  • Soil erosion due to wind or water flow increases suspended particulate matter and dust in the air. They may enter water bodies due to washing down by rain or natural waterfalls.
  • Volcanic eruptions add pollutants like SO2 and solid particles in form of ash to the Volatile organic compounds from Leaves, trees and dead decaying organisms give volatile organic compounds which mix the atmosphere.
  • Natural radioactivity by radioactive substances like uranium, thorium, etc.

Anthropogenic Pollutants:

  • Pollutants added to the environment through human activities are termed anthropogenic pollutants. They are further classified as primary pollutants and secondary pollutants.
  • Primary pollutants are those pollutants which are added directly in a harmful form to the atmosphere. eg CO2 and CO from the burning of fossil fuel; SO2 and oxides of nitrogen from vehicular combustion, thermal power stations, etc.
  • Secondary pollutants are the products of the reaction between the primary pollutants and normal environmental constituents.

2SO2  + O2 → 2SO3

  • In this case SO2 a primary pollutant, O2 a normal constituent of air to give secondary pollutant SO3. Further, SO3 reacts with water vapour present in the atmosphere and forms the sulphuric acid (secondary pollutant).

2SO3  +   H2O  →  H2SO4

  • Nitric oxide (NO), a primary pollutant reacts with oxygen to give NO2 which is a secondary pollutant.

2NO  + O2 → 2NO2

Classification of Pollutants on The Basis of The Type of Source:

Industrial Pollutants:

  • Paper, textile industries, tanneries and distilleries dispose various effluents like oil, grease, plastic and metallic wastes into
    the environment.

Domestic Pollutants:

  • Detergents, fluoride toothpaste, edible colours, food flavouring agents, polythene bags and wrappers. Crop burnt in the field after harvesting. Methane is produced in cattle stomach and in stagnant paddy fields is also a domestic pollutant.

Classification of Pollutants on The Basis of Their Degradation:

Non-degradable Pollutants:

  • The substances which do not degrade or degrade very slowly are called non-degradable pollutants. e.g. mercuric salts, lead salts, chromium salts, polythene, long chain phenolic chemicals, pesticides and D.D.T., etc.
  • These pollutants are not recycled in the ecosystem, hence get accumulated in the environment. Hence their small presence is also dangerous.

Degradable Pollutants:

  • These substances get degraded into the atmosphere due to the action of microorganisms. e.g. Domestic wastes, sewage, plan leaves and residues.
  • They are recycled in the ecosystem but their excess accumulation prohibits the complete degradation.

Classification of Pollutants on The Basis of The Motion of Source of Pollution:

Stationary Source Pollutants:

  • The pollutants released from a fixed location or a well-defined area is known as the stationary source. e.g. smokestacks of power plants, smelters, surface mines, etc.

Mobile Source Pollutants:

  • The pollutants released from diffused sources or the sources that move from place to place is termed as a mobile source. e.g. automobiles, buses, aircrafts, ships, trains, etc. The various pollutants of water.

Atmospheric Pollution:

  • On the basis of medium, the pollution is classified as
    • Air Pollution
    • Water pollution
    • Soil pollution

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