What does alkalinity refer to in water quality?

Alkalinity in water quality refers specifically to the capacity of water to neutralize acids. This property is primarily a function of the presence of bicarbonates, carbonates, and hydroxides in the water, which act as buffers to maintain pH levels. High alkalinity indicates that the water can resist changes in pH upon the addition of acids, making it essential for aquatic life, as a stable pH is crucial for healthy ecosystems.

Other options, like levels of dissolved oxygen, concentration of heavy metals, and total dissolved solids, pertain to different aspects of water quality assessment, such as oxygen levels for aquatic respiration, possible contamination from toxic substances, and general water clarity or salinity, respectively. However, they do not relate to the capacity to neutralize acids, which is the defining characteristic of alkalinity.