What does alkalinity measure in water?

Alkalinity in water primarily measures the water's capacity to resist changes in pH, often referred to as its buffering capacity. This refers to the presence of bicarbonates, carbonates, and hydroxides in the water, which can neutralize acids and stabilize pH levels. When acids are introduced into the water, the alkalinity helps to absorb these changes, preventing drastic shifts in pH that can adversely affect aquatic life and overall water quality.

The significance of maintaining proper alkalinity levels is essential for aquatic ecosystems, particularly in addressing issues related to acid rain or other sources of acidity that can occur in natural water bodies. If alkalinity levels are too low, it can lead to a decrease in pH, which may harm fish and other organisms. Thus, measuring alkalinity is a critical aspect of assessing the health of water bodies and ensuring the stability of their chemical environment.

The other options focus on different facets of water quality. Acidity directly measures hydrogen ion concentration, dissolved solids quantify the total amount of minerals present, and temperature relates to the thermal conditions of the water rather than its buffering capacity.