Pollution:-  

Any undesirable change in composition of environment which is harmful for living organism.

 Causes of pollution:-

1. Population  explosion 
2. Industrialization and urbanization
3. Deforestation

Positive pollution:- Addition of undesirable substance at wrong place which result in reduction of fertility of soil.

Eg:-

1. Land filling by waste.
2. Excessive use of fertilizer.

Negative pollution:- Removal of desirable substance from right place which result in reduction in fertility of soil.

Eg:-

1. Soil erosion
2. Over grazing

Pollution on basis of source:-

1. Point source pollution:- Means all the pollution is caused from a single outlet.

e.g. Chimney and sewage treatment plant.

2. Live source Pollution:- Pollution in the form of narrow belt.

E.g. roadways or railway tracks.

Pollutant:- Agent causing pollution.

Primary pollutant:- It is directly released by human activity and causes pollution.

e.g. :- CO₂, NO₂, NO₃, N₂O, NO_x.

SO₂, SO₃ causes direct pollution.

Secondary pollutant:-

It is formed due to chemical reaction of primary pollutant with any environment factor.

e.g.:- Ozone, PAN [peroxy acetyl nitrate]

Synergism:- When 2^o pollutant causes great harm with respect to 1^o pollutant.

Qualitative pollutions:-

Cause pollution due to its nature. Initially it is absent in environment and now appears in activity due to human activity.

e.g.:- Chemical pesticides.

Quantitative pollutions:- Causes pollution due to its excessive amount.

e.g.:- CO₂, O₃, CO.

Biodegradable pollutions:- Dead plant part, Dead animal body, animal waste.

Non-Biodegradable:- e.g.:- DDT(lipid soluble which gets accumulated in adipose tissue which cause cancer, sterility.

Recyclable:- paper, plastic, glass, metals.