What is acid rain, and why is it most closely associated with the northeastern part of the United States and eastern Canada?

Acid rain is a kind of rain or precipitation that contains high concentration of harmful acidic pollutants mainly nitrogen oxide and the sulfur dioxide which is released into the atmosphere that reach the earth's surface. It is caused by burning of fossil fuels and other industrial wastes released into the atmosphere that reach with rain and turns the precipitation acidic. The marbles of Taj Mahal is also getting adversely affected due to acid rain.

Acid rain is associated with the Part of USA and Canada for two reasons - natural causes such as volcanic eruption, wildfires and lightning:man made causes such as coal plants and Air pollution from automobiles. An average pH of 4-5. is usually found there (5.6 is normal for atmosphere).