Inorganic Compounds (IOCS)

Inorganic compounds are rather simple chemicals present in ground water. These chemicals are generally described as mineral in nature and usually exist as ions (chemical substances with a positive or negative charge) when dissolved in water. Typical examples include sodium, iron, calcium, magnesium, manganese, nitrate, chloride, sulfate, and zinc. Many of these chemicals are naturally occurring minerals that are dissolved from the rock/soil which make up the aquifer or water-bearing rock formations below the soil surface. However, some of these compounds may be introduced into ground water by human activities. Nitrate (an agricultural fertilizer) and sodium chloride (road salt) are two examples. The Water Utility tests all of its wells for nearly 30 different inorganic compounds including all the chemicals named above plus arsenic, barium, cadmium, lead, mercury, selenium, and thallium.

Concerned about sodium? Take a look at the 2011 PHMDC paper on sodiumpublished on its website.


Radionuclides are unstable forms of an atom that give off radiation as they decay into more stable atoms. They may come from natural or man-made elements. Radium-226 and radium-228 are radionuclides that form from uranium and thorium decay in the environment. In the natural environment, radium occurs at very low levels in almost all rock, soil, water, and plants. If high levels of thorium or uranium occur in native rock, radium will also be present at high levels.

Seven Madison wells were required to be tested in 2015.