Alkalinity is defined as

Alkalinity is defined as

• A. the ability of water to neutralize acids via hydroxide, carbonate, and/or bicarbonate ions
• B. the concentration of dissolved salts
• C. the buffering capacity of biota
• D. the total suspended solids

Answer: (A)

Alkalinity is the water’s ability to neutralize acids, a buffering capacity provided mainly by hydroxide, carbonate, and bicarbonate ions. When acid is added, these base species react to consume hydrogen ions, forming carbonic acid and carbon dioxide, which helps keep the pH from dropping quickly. In most natural waters, bicarbonate is the dominant contributor, especially where carbonate rocks are present, but the key idea is the buffering action against acidification, not the presence of dissolved salts or solids. The other statements describe different water properties (dissolved salts relating to salinity, biota buffering not a standard measure, and suspended solids affecting turbidity), so they don’t define alkalinity.

Alkalinity is the water’s ability to neutralize acids, a buffering capacity provided mainly by hydroxide, carbonate, and bicarbonate ions. When acid is added, these base species react to consume hydrogen ions, forming carbonic acid and carbon dioxide, which helps keep the pH from dropping quickly. In most natural waters, bicarbonate is the dominant contributor, especially where carbonate rocks are present, but the key idea is the buffering action against acidification, not the presence of dissolved salts or solids. The other statements describe different water properties (dissolved salts relating to salinity, biota buffering not a standard measure, and suspended solids affecting turbidity), so they don’t define alkalinity.