Examples of regional pollution are

$A$ : Irrigation without proper drainage of water leads to water logging in the soil.
$R$ : Water logging results in increased soil salinity.

Among the $41$ most polluted cities of the world,Delhi ranked

The figure shows the biomagnification of $DDT$ in an aquatic food chain. What could be the concentration of $DDT$ in $P$,$Q$,and $R$ respectively?

$A$ large number of fish suddenly die in a lake near a village. Which of the following could be the reason for this?
$(a)$ Excessive use of urea and phosphate fertilizers in nearby fields.
$(b)$ Spraying of $DDT$ in the entire area.
$(c)$ The lake water has turned green and murky.
$(d)$ The population of phytoplankton in the lake has decreased,reducing the photosynthetic capacity.
Which two of the above reasons are responsible?

The second commitment period for the Kyoto Protocol was decided at