Quick Revision: Environmental Chemistry | Inorganic Chemistry for NEET PDF Download

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ENVIRONMENTAL POLLUTANTS
Any substance which causes pollution in the environment is known as environmental pollutant. It can be
atmospheric, water and soil pollution.
WATER POLLUTION
The quality of drinking water is very important for human welfare. The pollution of water by sewage has been
linked with the spreading of diseases such as cholera and typhoid fever.
In addition, water is also contaminated by industrial wastes, like :
(i) Heavy Metals : Such as Cd, Pb and Hg may be present.
(ii) Detergent and Fertilizers : They may contain 
–3
4
PO as additives which encourages the growth of algae
that reduces the dissolved oxygen concentration of water. This process is known as Eutrophication.
(iii) Acid Polluted Water (pH < 3) : This is deadly to most forms of aquatic life.
(iv) Polychlorinated Biphenyls (PCBs) : PCBs are resistant to oxidation and their release into the environment
causes skin disorders in humans. They are reported to be carcinogenic.
Determination of quality of waste water : It is done through BOD and COD.
Biological Oxygen demand (BOD) - It is the amount of oxygen required for biological oxidation by microbes
in any unit volume of water. This test is done for at least 5 days. BOD values generally approximates the
amount of oxidisable organic matter.
Chemical oxygen demand (COD) : BOD measurement takes few days, so another parameter called COD
measurement is required. In COD measurement sample of fixed volume is treated with oxidising agent
(usually K
2
Cr
2
O
7
 in acidic medium). The reagent oxidises most of the polluting substances including those
which are resistant to microbial oxidation.
AIR POLLUTION
Air is very essential for life, particularly oxygen which is needed for breathing. But at the same time air is
polluted due to various human activities. Man made, pollutants such as gases like CO, NO, NO
2 
, SO
2 
,
H
2
SO
4
, hydrocarbons and aerosols etc are being constantly released in the atmosphere leading to air pollution.
Atmospheric Pollution
Tropospheric pollution : Troposphere extends upto height of 10 km from sea level. It contains 80% of total
mass of air and water vapour. Pollution is also caused by SO
2
, SO
3
, NO
2
 etc.
Stratospheric pollution : Extends (10–50) km above sea level. It contains N
2
, O
2
 and ozone.
Table : Sources of Air Pollution
Sl. No. Class Aerosols Gases and Vapours
1. Combustion processes Dust, fumes, smoke SO
2
, NO
2
, CO, Organic vapours
2. Chemical processes Dust, fume, mist Process dependent
(cement and fertilizers) (CO
2
, SO
2
, CO, NH
3
, NO
2
 organic vapours)