Primary Anions and Cations in WaterA wide range of different elements can become dissolved in water as a result of interactions with the atmosphere, the environment, soil and bedrock. As the water flows it picks up additional minerals and other chemicals on its way to the groundwater or to the river.
Groundwaters tend to have much higher concentrations of most constituents than do surface waters. Deep groundwaters that have been in contact with rock for a long time tend to have higher concentrations than shallow waters.
It is convenient to divide dissolved constituents into major components, the predominant cations and anions, and trace elements.
The major cations present in water are calcium, magnesium, sodium and potassium. The major anions present in water are bicarbonate/carbonate, sulphate and chloride.
Cations are positively-charged ions (atoms or groups of atoms that have more protons than electrons due to having lost one or more electrons).
Anions are negatively-charged ions (meaning they have more electrons than protons due to having gained one or more electrons).
Anions such as the primary nutrients nitrate and phosphate may become dissolved in water from many sources:
Nitrogen and phosphorus are both essential for aquatic growth covered here…Primary Nutrients and Eutrophication.