Explain following.
(i) Salination
(ii) Ozone hole
(iii) Pollution
(iv) Secondary pollutants
(v) Smog
(vi) Plume
(vii) Aerosol
(viii) Eutrophication
(ix) Biomagnification
(x) Positive soil pollution

(i) The increase in the concentration of soluble salts in the soil is called as salination.
(ii) Decline in the thickness of ozone layer in specific regions is called as the ozone hole.
(iii) An undesirable change in the physical, chemical or biological aspects of the environment which makes it harmful to humans, all other living organisms and for cultural assets is called as pollution.
(iv) Secondary pollutants are formed by interaction among the primary pollutants, e.g., PAN.
(v) Smog is a dark fog formed by condensation of water vapours around, dust, smoke particles and various gaseous pollutants (NO${}_2$, SO${}_2$, H${}_{2}S$ etc.).
(vi) Geometrical shape or form of the smoke coming out of a chimney is called as a plume. 
(vii) Aerosol is a general term used for particles suspended in air.
(viii) Phosphates and nitrates dissolved in water act as nutrients and accelerate the growth of algae. This increased productivity is called as eutrophication.
(ix) Industrial wastes and some pesticides (e.g., DDT) are not biodegradable and hence they keep on increasing in concentration at different trophic levels in the food chain. This is called as biomagnification.
(x) Reduction in the productivity of the soil due to an addition of undesirable substances is called as positive soil pollution.