Which of the following contributes to the buffer capacity of water?

Alkalinity is a key factor that contributes to the buffer capacity of water. It refers to the ability of water to neutralize acids and is largely influenced by the presence of bicarbonates, carbonates, and hydroxides. These compounds can react with added acids or bases to help stabilize the pH of the water, thereby maintaining a relatively constant environment. This buffering action is particularly important in natural water bodies, as it protects aquatic life from harmful pH fluctuations that can arise from organic decomposition, industrial discharges, or other pollution sources.

The pH level of the water is a measure of its acidity or basicity, but it does not directly contribute to buffering capacity; instead, the pH is an indicator of how effective the buffer systems are within the water. Dissolved oxygen is crucial for aquatic organisms and can influence biochemical processes, but it does not play a direct role in the buffer capacity. Temperature affects chemical kinetics and solubility of gases, but again, it is not a buffering agent. Thus, the contributing factor to the buffer capacity of water is primarily represented by alkalinity.