Negative Alkalinity and Bicarbonate

A Bru’n Water user asked about negative values being reported for Alkalinity and Bicarbonate in the program.

While alkalinity is typically a positive value, it can fall below zero. The following response was taken from the United States Geological Survey:

"Alkalinity and ANC (acid neutralizing capacity) are just a measure of the deficiency of H+ ions relative to a solution of carbon dioxide in water. A negative alkalinity or ANC simply reflects the presence of some amount of mineral acidity, or an abundance of H+ ions relative to a solution of carbon dioxide in water. Alkalinity and ANC may be positive, zero, or negative. It is instructive to note that concentrations of hydroxide, carbonate, and bicarbonate ions, unlike alkalinity and ANC, cannot be negative."

Bru'n Water does tabulate the acidity or alkalinity calculated for the solution and the alkalinity value CAN be reported as a negative value in the results.  In the same tabulation, the program calculates and reports alkalinity using a "Bicarbonate" surrogate. If net bicarbonate is present, it is reported as a positive bicarbonate value. If the solution has excess acidity and all bicarbonate is consumed, the bicarbonate is reported with a negative value.

Negative values are acceptable in Bru’n Water.