Groundwater can be contaminated by many different kinds of sources. Harmful chemicals or biological materials are usually deposited into the soil above the aquifer, seeping into the groundwater from there.

Some of the common sources are found on this page. There are many, many more. Click each picture below for a larger version.

As you look at each picture, notice what specific contaminants are found at each source. From which sources can you find nitrates? From which can you find gasoline products?

All of the pictures on this page are from Michigan State University