Sodium is a mineral that commonly occurs in a range of food sources. Despite often being used interchangeably with the term ‘table salt’, sodium and salt are two different things; salt is a crystal-like compound which is about 40% sodium and 60% chloride, also found abundantly in nature.
Sodium is a major concern in drinking water in the form of sodium chloride, with no smell but a distinctive salty taste. Sodium is also key for functioning of the human body however when salt levels are too high, the water can pose a significant health risk if ingested. Generally, a ‘safe’ sodium level in water is below 20 mg/L however some countries water supply will far exceed this. A complication can come in the form of water treatment chemicals that contain sodium, which can artificially raise sodium levels.
In freshwaters levels of sodium are generally low, either single or double digits, and as such aquatic flora and fauna are generally not well adapted to increased sodium concentrations. Sodium levels can increase in freshwaters due to a number of factors such as runoff from urban environments where de-icer products have been used, weathering of concrete and the application of fertilizers to name but a few. When this occurs, it can lead to a phenomenon known as freshwater salinization syndrome (FSS) which characterises the direct and indirect effects of salts that trigger other pollutants across ground & surface water, soils and pipework infrastructure to become more mobile and concentrated. For example, increase in salts can causes metals to mobilise from soils allowing them to be more easily transported into water courses which can then trigger polluting events and toxicity response from aquatic life.
