What is indicated when the pH of water is above 8.3?

When the pH of water is above 8.3, it typically indicates the presence of bicarbonate ions. Bicarbonate can act as a buffering agent in water, helping to stabilize pH levels. It is a common ion found in natural water supplies and contributes to the alkalinity of the water. As the concentration of bicarbonate increases, it can raise the pH above the neutral point (7.0) and often leads to a higher value, such as 8.3 or even higher.

In contrast, the presence of chlorine or other ions may not necessarily correlate directly with a higher pH, and the absence of carbon dioxide doesn't inherently infer a specific pH level. High hardness is related to the concentration of calcium and magnesium ions, yet, while it can affect pH, it is not as specifically indicative as bicarbonate presence when pH values exceed 8.3. Thus, a pH above 8.3 strongly suggests the influence of bicarbonates in the water chemistry.