Which water quality characteristic is typically measured on the pH scale?

• A. Dissolved Gases
• B. Turbidity
• C. Alkalinity
• D. Acidity

Answer: (D)

pH directly expresses how acidic or basic a water solution is, based on hydrogen ion activity. This makes acidity the water quality characteristic that is typically measured on the pH scale. A lower pH means higher hydrogen ion concentration and more acidic conditions; a higher pH means fewer hydrogen ions and more basic (alkaline) conditions. The pH value helps predict how water will interact with pipes (corrosion), affect chemical reactions in treatment, and influence aquatic life.

Dissolved gases are reported as concentrations (often in mg/L or as partial pressure), not by pH. Turbidity measures cloudiness due to suspended particles and is assessed with light scattering, not pH. Alkalinity measures the water’s buffering capacity to resist pH changes, which is related to, but not the same as, the current pH.