Which natural mineral in water increases alkalinity and buffering capacity?

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Multiple Choice

Which natural mineral in water increases alkalinity and buffering capacity?

Alkalinity measures a water’s capacity to neutralize added acid, mainly from dissolved carbonate species such as bicarbonate and carbonate. When water contains limestone, a calcium carbonate mineral, it can dissolve to release bicarbonate ions, boosting both alkalinity and the system’s buffering ability. A common way this happens is CaCO3 reacting with CO2 and water to form Ca2+ and 2 HCO3−, which raises the carbonate/bicarbonate content and makes the water more resistant to pH changes. Other minerals listed don’t provide the same carbonate-based buffering. Sand and quartz are primarily silica and contribute little to carbonate alkalinity. Gypsum (calcium sulfate) adds calcium and sulfate but not carbonate alkalinity, so it doesn’t increase buffering capacity in the same way limestone does.

Alkalinity measures a water’s capacity to neutralize added acid, mainly from dissolved carbonate species such as bicarbonate and carbonate. When water contains limestone, a calcium carbonate mineral, it can dissolve to release bicarbonate ions, boosting both alkalinity and the system’s buffering ability. A common way this happens is CaCO3 reacting with CO2 and water to form Ca2+ and 2 HCO3−, which raises the carbonate/bicarbonate content and makes the water more resistant to pH changes.

Other minerals listed don’t provide the same carbonate-based buffering. Sand and quartz are primarily silica and contribute little to carbonate alkalinity. Gypsum (calcium sulfate) adds calcium and sulfate but not carbonate alkalinity, so it doesn’t increase buffering capacity in the same way limestone does.

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