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

Silicon is the most abundant element on earth after oxygen. Large amounts of silicon can be found in various minerals and it is abundant in oceans and nearly all other waters as silicic acid. In the surface layers of oceans silicon concentrations are 30 ppb, whereas deeper water layers may contain 2 ppm silicon. Rivers generally contain 4 ppm silicon. Silicon is usually not ionized when dissolved; it is present as ortho silicic acid (H₄SiO₄ or Si(OH)₄). These compounds are the result of slow dissolution of silica in water. Rivers transport large amounts of silicon to sea. Most likely, less than 20% of dissolved silicon is removed from rivers by means of biological or chemical transformation processes.