Environmental Issues -
Human poculation is increasing tremendously; therefore there is a lot of demand for food, electricity, clothing, housing, roads, etc. These are exerting a lot of pressureon natural resources which are undergoing depletion and degradation, leading to pollution and deterioration of environment and biodiversity.
POLLUTION
Poliution may be defined as an undesirable change in the physical, chemical on biological aspects of environment which makes it harmful for humans and other living organisms as well as for cultural assets.
The agents which cause environmental pollution are called pollutants.A pollutant may be defined as a physical, chemical or biological substance, unintentionally released into the environment, which is directly or indirectly harmful to humans
and other living organisms.
Pollution can be natral or man made.
Natural pollution comes from natural sources like release of methane by cattle and paddy fields, smoke from forest fire, dust storms, nitrogen oxides
ozone from volcanic eruptions, emission of natural gas, biological decay, etc
Man made or anthropogenic pollution is the pollution caused by human activities like sewage effluents, pesticides, fertilisers, mining, burning of fossil fuels, noise, deforestation, etc.
Most of the natural pollution is balanced by activities occurring in nature itself like CO2 from animals and plants released during respiration is used up in photosynthesis.
Classification of pollutants
On the basis of their existence in nature, form (in which the pollutants persist after release) and nature of disposal, pollutants are of various types. The various classes of pollutants are shown in the given flow chart
Air pollutants-
The air pollutants have been separated into two categories:
the primary air pollutants and the secondary air
pollutants.
Primary air pollutants
Primary air pollutants include the directly emitted
substances from some identifiable sources.
The major primary air pollutants are carbon dioxide, carbon monoxide, nitrogen oxides, sulphur oxides, hydrogen sulphide, hydrocarbons, particulate matter, etc. which are discussed in the given table.
Particulate matter is a complex mixture of suspended solid and liquid particles in semi-equilibrium with surrounding gases
The particulate pollutants may be solid or liquid particles.
The larger particles such as sand and water droplets, quickly settle down in still air. They are called settleable particulate matter. Small particles such as dust, remain suspended in the air for a longer time. They are termed
suspended particulate matter (SPM). Very fine particles such as tobacco smoke, do not settle at all. They are known as nonsettleable particulate matter
The particulates are categorised according to size, source or physical state. They are differentiated into aerosol (less than 1 μm), dust (more than 1 μm) and mist (liquid, more than 1 um). Aerosol consists of liquid droplets or solid particles dispersed in a gas. For example, cigarette smoke is
an aerosol of ash in air
