Sodium and water: reaction mechanisms, environmental impact and health effects

For billions of years sodium is washed out from rocks and soils, ending up in oceans, where it may remain for about 50^.10⁶ years. Seawater contains approximately 11,000 ppm sodium. Rivers contain only about 9 ppm.
Drinking water usually contains about 50 mg/L sodium. This value is clearly higher for mineral water. In soluble form sodium always occurs as Na⁺ ions.