1. These are substances which cannot be broken down by the activity of microorganisms. These substances go on concentrating at each trophic level of food chain, e.g., DDT and heavy metal (mercury, cadmium, etc.).

    These are substances which cannot be broken down by the activity of microorganisms. These substances go on concentrating at each trophic level of food chain, e.g., DDT and heavy metal (mercury, cadmium, etc.).

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  2. (i) Sewage; (ii) Industrial wastes; (iii) Synthetic soaps and detergents; (iv) Fertilizers and pesticides; (v) Petroleum; (vi) Heat.

    (i) Sewage; (ii) Industrial wastes; (iii) Synthetic soaps and detergents; (iv) Fertilizers and pesticides; (v) Petroleum; (vi) Heat.

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  3. 1. Ground water; 2. Surface water (ponds, lakes, streams, rivers, etc.).

    1. Ground water; 2. Surface water (ponds, lakes, streams, rivers, etc.).

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  4. Generally, tetraethyl lead is added to petrol to make it burn smoothly in motor vehicles. However, burning of petrol in automobiles releases toxic lead compounds through the exhaust pipes of automobiles. Continuous inhalation of these compounds causes anaemia, brain damage, convulsions and even deatRead more

    Generally, tetraethyl lead is added to petrol to make it burn smoothly in motor vehicles. However, burning of petrol in automobiles releases toxic lead compounds through the exhaust pipes of automobiles. Continuous inhalation of these compounds causes anaemia, brain damage, convulsions and even death.

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