What are three sources of groundwater pollution and how do pollutants get into the water?
Septic tanks, oil containers (underground) and industrial and agricultural pollutants
From domestic sources, such as houses, septic tanks cause groundwater pollution. Since there are many chemicals used in homes, detergents, shampoos, cosmetics, etc., these chemicals might enter into groundwater via septic tanks. They contaminate groundwater.
Oil tanks (such as leaking underground tanks) are another concern. Benzene, toluene, etc. are chemicals that are found in such tanks. They do not degrade easily when they are introduced in groundwater. It is hard to treat such pollution too.
Industrial areas might contaminate groundwater too. Civil Action (a movie) addresses this issue. Agricultural chemicals (such as pesticides, nutrients, etc.) cause groundwater pollution and this is a nonpoint pollution.