What does alkalinity measure?

Alkalinity measures the capacity of water to neutralize acids, which is primarily attributed to the presence of carbonate, bicarbonate, and hydroxide ions. These ions react with acids and thus help maintain a stable pH level in the water. By quantifying the concentrations of these specific ions, alkalinity provides insight into the buffering capacity of the water body, indicating how well it can resist changes in pH when acids are added. This is particularly important for aquatic environments, where significant fluctuations in pH can be harmful to aquatic life.

The other options refer to different water quality parameters. The total amount of dissolved solids pertains to the overall concentration of all dissolved substances in water, not its buffering capacity. Measuring acidity through pH gives an indication of how acidic or basic a solution is but does not specifically address the buffering capacity related to alkalinity. Finally, the concentration of nitrogen compounds relates to the nutrient level in the water, which is a separate aspect of water quality and does not measure the alkaline properties that alkalinity focuses on.