Calcium and water: reaction mechanisms, environmental impact and health effects Calcium
occurs in water naturally. Seawater contains approximately 400 ppm calcium. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust. Calcium is also a constituent of coral. Rivers generally contain 1-2 ppm calcium, but in lime areas rivers may contains calcium concentrations as high as 100 ppm.
Examples of calcium concentrations in water organisms: seaweed luctuca 800-6500 ppm (moist mass), oysters approximately 1500 ppm (dry mass).
In a watery solution calcium is mainly present as Ca2+
(aq), but it may also occur as CaOH+
(aq) or Ca(OH)2
(aq), or as CaSO4
Calcium is an important determinant of water harness, and it also functions as a pH stabilizer, because of its buffering qualities. Calcium also gives water a better taste.