What is Alkalinity reported as?

Alkalinity is a measure of the capacity of water to neutralize acids, and it is typically expressed as the equivalent concentration of calcium carbonate (CaCO3). This is the standard practice in water quality analysis because calcium carbonate is a common reference compound that represents the buffering capacity of water. The use of mg CaCO3/L allows for a clear understanding and comparison of alkalinity levels, which can help in assessing the quality of the water and its ability to counteract the effects of acidification.

Reporting alkalinity as calcium carbonate also makes it easier for researchers and water treatment professionals to relate alkalinity values to the natural processes in water systems, as CaCO3 is widely encountered in various environmental contexts. Other compounds, such as sulfuric acid (H2SO4), sodium chloride (NaCl), or potassium chloride (KCl), are not relevant to the measurement of alkalinity, as they do not represent the buffering capacity that defines alkalinity in water systems.