Sources of alkalinity in water chemistry Alkalinity in a water sample may arise from which of the following constituents?

Introduction / Context:Alkalinity is a measure of a water’s capacity to neutralize acid. It is a key parameter for coagulation control, corrosion tendency, and biological stability in distribution systems.

Given Data / Assumptions:

• In natural and treated waters, alkalinity typically results from bicarbonates, carbonates, and hydroxides.
• Metal cations (Ca, Mg, Na, K) pair with these anions to form the salts present.

Concept / Approach:Bicarbonate alkalinity (HCO3−) commonly arises from Ca and Mg bicarbonates. Carbonate alkalinity (CO3^2−) may be present as sodium or potassium carbonates. Hydroxide alkalinity (OH−) can appear when lime is added or pH is adjusted upward. The total alkalinity equals the sum of these contributions expressed as CaCO3 equivalent.

Step-by-Step Solution:

Verification / Alternative check:Standard methods (acid titration to pH endpoints) apportion alkalinity among bicarbonate, carbonate, and hydroxide species.

Why Other Options Are Wrong:Each individual option is only a subset; full characterization requires acknowledging all contributing species.

Common Pitfalls:Assuming alkalinity equals hardness: magnesium/calcium bicarbonates contribute to both, but sodium/potassium carbonates add alkalinity without hardness.

Final Answer:All the above