Environmetal Chemistry
ENVIRONMENTAL CHEMISTRY
The branch of science which deals with the chemical phenomena occuring in the environment is called as
environmental chemistry.
INTRODUCTION
The environment means surroundings. It has 4 following component.
Atmosphere
Function of the atmosphere :
l It contain all the gases which are essential for the life on the earth.
l It is a carrier of water vapour which are needed for all life.
l Ozone (O3) is present in stratosphere which is responsible for absorption of 99.5% of harmful U.V.
radiations.
l It maintain heat balance of the earth by absorbing infrared radiation, coming from the sun and re-emit
from the earth.
ENVIRONMENTAL POLLUTION & ENVIRONMENTAL POLLUTANT
The addition of any undesirable material to air, water and soil by a natural source (or due to human
activity) which affects the quality of environment is called as environmental pollution.
The undesirable material which is added to the environmental is called as pollutant
Causes of pollution :
* Fast growth. * Rapid urbanisation.* Excessive trialisation. * Use of pesticides in agriculture
Types of Pollutants
Bio Degradable and Non Bio Degradable Pollutants
(A) Bio degradable pollutants : The materials (such as cow dungs) which are easily decomposed by the
micro-organism. These are not harmful, but in the excess in environment, they do not undergo degradation
completely and thus become pollutant. Eg. Discarded vegetables
(B) Non bio degradable pollutants :- The material (such as Hg, Al, DDT) which do not undergo degradation
(or degrade very slowly) but their presence even in very small amount in the environment is very harmful.
They may react with other compounds present in the environment and produce more toxic compound.
Eg. Plastic materials, DDT, heavy metal, many chemicals, nuclear wastes etc
TYPES OF POLLUTION
Depending on the Part of the Environment Polluted
(A) Air pollution (B) Water pollution (C) Soil pollution (or land pollution)
(A) Air pollution : It is defined as the undesirable materials into the atmosphere either due to natural phenomena
(or due to human activity on the earth). Which affect the quality of the air and also affect the life on the Earth.
Major source of air pollution :
(i) Natural sources :
Ex. due to CO, H2S, SO2, Forest fire
(ii) Man made air pollution or source due to human activity :
Natural sources :
Ex. Burning of fossil fuels which produce some poisonous gases as CO, CO2, CH4, oxide of nitrogen .
Combustion of gasoline in the automobiles : The automobiles emit the CO, oxide of nitrogen
(NO, NO2)
Deforestation : Due to this % of CO2 is increased and % of O2 is decreased.
Fast industrialisation : The smoke of carbon and CO, CO2, SO2, H2S, NO, NO2 are coming out from
the industries. The industries are responsible for 20% of total air pollution.
Agriculture activities : The pesticides are added in the soil. They give a foul smell and affect the
health of animals and human being.
Wars : The nuclear weapons are used in war which emit the radiation
Air pollutants :
(A) CO as pollutant : It is mainly realsed by automobile exhaust due to incomplete combustion of carbon. It
binds to haemoglobin to form carboxyhaemoglobin, which is about 300 times more stable than the oxygen-
haemoglobin complex. In blood, if the concentration of carboxyhaemoglobin reaches 3-4 percent then oxygen
carrying capacity is greatly reduced.
Sink of CO : A large amount of CO are added in the atm. But the level of CO does not rise too much as CO
is converted in CO2 by the micro organism which is present in the soil.
The micro organism (bacteria) act as sink for CO.
Harmful effect of CO :
(i) The CO is poisonous because it combine with haemoglobin of R.B.C. about 300 times easily than O2, to
form carboxy haemoglobin.
(ii) Oxygen deficient results into headache, weak eyesight, nervouness and cardiovascular disorder.
(iii) In pregnant women who have the habit of smoking the increased CO level in blood may induce premature
birth, spontaneous abortions and deformed babies
(B) Hydro carbon : Hydrocarbons are carcinogenic, i.e., they cause cancer. They harm plants by causing
ageing, breakdown of tissues and shedding of leaves, flowers and twigs.
(a) Natural sources :
(i) Due to decomposition of organic matter in soil
(b) Man made sources :
(i) Due to burning of stationary fuel. (ii) Evaporation of organic solvent.
(C) Sulphur compounds : Produced by burning of fossil fuel. The most common species, sulphur dioxide,
is a gas that is poisonous to both animals and plants.
Harmful effect of Sulphur compounds :
(i) Even a low concentration of sulphur dioxide causes respiratory diseases e.g., asthma, bronchitis, emphysema
in human beings.
(ii) Causes irritation to the eyes, resulting in tears and redness.
(iii) High concentration of SO2 leads to stiffness of flower buds which eventually fall off from plants.
Sulphur dioxide Uncatalysed oxidation of sulphur dioxide is slow. However, the presence of particulate matter
in polluted air catalyses the oxidation of sulphur dioxide to sulphur trioxide.
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