Sodium

Sodium is the sixth most abundant element on earth. Sodium is often associated with chloride; common table salt is mostly sodium chloride. Sodium is used extensively in industrial processes, food processing, and in some water softening devices. Sodium is represented in the Periodic Table of Elements as Na.

The Role of Sodium in Waterbodies
All waters contain sodium, which is essential to all animals and some microorganisms and plants. Generally, sodium is not considered a limiting factor for freshwater organisms, unless sodium concentrations reach levels at which freshwater organisms cannot survive. As sodium concentrations increase in a waterbody, there can be a continuous transition from freshwater organisms to those adapted to brackish water and then ultimately to marine (saltwater) organisms. High sodium concentrations can be expected in the following:

Areas near the coast that receive sodium-enriched groundwater from saltwater intrusion;
Areas where evaporation is excessive (perhaps in hot and/or dry climates);
Areas receiving human pollution including agricultural runoff containing fertilizer residues, discharges containing human or animal waste, and backwash from water softeners using the sodium exchange process.

In Florida
Waterbodies in the Florida LAKEWATCH database have sodium concentrations which ranged from 1 to over 1100 mg/L. Over 75% of these waterbodies had sodium concentrations less than 13 mg/L. The higher concentrations of sodium are found in lakes located near the coast and in lakes where the groundwater entering the lakes has been in contact with natural salt deposits.

Health Concerns
At the concentrations found in freshwaters, sodium generally causes no known direct threat to human health.

See also:
Chloride
Salinity
Surface water
Limiting nutrient

The information on this page was derived in part from the following publication of
Florida Lakewatch of the University of Florida Department of Fisheries and Aquatic Sciences.
This booklet may be downloaded in its entirety as a PDF file by clicking here.
Scroll down till you see the Circular 101 icon.

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This project is a collaboration of
the Center for Aquatic and Invasive Plants, University of Florida,
and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection