Calcium is often used as a measure of ‘hardness’ for water. Water hardness refers to the amount of magnesium and calcium that is dissolved within the water. Where water is particularly ‘hard’ there is a high level of dissolved minerals present. Calcium occurs naturally in waters having been dissolved as water runs over/through limestone and chalk rocks in particular.
Hard water can present significant challenges to homeowners and industry alike with a tendency to build up hard deposits known as scale on pipework which can cause reduced water flow and additional stress on pipe systems eventually causing corrosion. Hardness often has to be removed before it is used in industrial processes.
When water is softer, the permeability of gill membranes is increased meaning aquatic mammals will uptake heavy metals dissolved in the water more easily. In harder water, calcium competes with other heavy metals for binding spots on the gills and some metals will actually form a precipitate and therefore be unavailable for uptake by organisms.
