NEET Chemistry Environmental Chemistry Revision Notes

Environmental Chemistry

Components of Environment:

It is the atmosphere condition in which the presence of certain concentration produce harmful effects on man and his environment. These substances include:

 

Particulate Matter Inorganic gases Secondary

 

Particulate matter:

• Soot

• Metal particles

• Metal oxides .

• Lead salts

• Fly ash

• Asbestos dust

• Solid Hydrocarbons

• Dust Particulates

• Acid mist.

 

Stratospherical Pollution: (ozone layer & its depletion):

Role of Ozone Layer: protecting earth from the UV radiation coming from the sun. Depletion of Ozone Layer : The equilibrium between formation & destruction of ozone has been upset by influx of several substances into the atmosphere which react with ozone to destroy it.

Effect of Depletion of Ozone layer: The influx of UV radiation reaching the surface of earth would increase which would increase in risk to skin cancer due to exposure to UV radiation, UV radiations also tend to damage the immune system.

Acid Rain:

SO₂, nitrogen oxides & acidic soots. Sulphurdioxide & nitrogen dioxide interact with water vapours in presence of sunlight to form sulphuric acid & nitric acid units.

radiations of short wavelength. As a result of this the temperature of earth stands rising. Eventually, earth starts emitting infrared radiations of longer wavelengths. The partially radiated infrared radiations from the earth are absorbed by the greenhouse gases. This results in excessive heating of Earth’s atmosphere. Thus the greenhouse gases add to the heating of atmosphere. This causes global warming. The atmosphere traps the sun’s heat near earth’s surface and keeps it warm. The reemission of the earth’s energy absorbed by CO₂ and other greenhouse gases present near the earths surface and its radiation back to the earth is called green house effect.

Advantages of green house effect :

• It is necessary for evaporation of water, formation of clouds, rainfall etc.

• The warm atmosphere helps in rapid growth of plants, trees etc. Harmful effects of green house effect :

• High temperature of atmosphere may melt polar ice caps which are likely to raise the level of sea thereby sinking most of the coastal areas and causing large scale destruction.

• The high temperature may reduce crop product.

• The high temperature will reduce work efficiency of human being.

• Tropical rains and hurricane will become more frequent and also stronger causing more devastation.

• The change in ocean temperature will adversely affect the warm life.

Biochemical Oxygen Demand (BOD) : The measure of the total contamination caused by compounds which can be oxidised in the presence of microorganisms. The BOD is taken as a realistic measure of water quality – clean water would have a BOD value of less than 5 ppm whereas highly polluted river water could have a BOD value of 17 ppm or more.

Land Pollution :

Caused by pesticides and other chemicals which are added to the soil to grow better crops.