Re: what is a non-point source pollution?

The term "nonpoint source pollution" comes from the historical fact that in 
the United States government started controlling pollution from industrial 
"point sources", such as pipes, ditches, air stacks, first.  When pollution 
prevention moved to address other sources, those not from pipes, these were 
referred to as "nonpoint sources."  Nonpoint sources of pollution include 
farm fields, road and parking lot surfaces, yards and almost any other 
surface area that allows contaminants to migrate into the surrounding 
environment.  The term is typically use in the context of water pollution, 
so nonpoint source pollutants tend to be those materials that move when 
they become dissolved in water, or are washed by the physical action of 
water into surrounding rivers, lakes, or wetlands.  The equivalent term for 
air pollutants would be fugitive emissions.

I hope you find this helpful.  I did my Master of Science in nonpoint 
sourrce pollution of a watershed called Blackearth Creek, near Madison 
Wisconsin in the USA.  I studied the impact of pollution from farm fields 
and towns on insect life in the stream.