Which substance combines with hydrogen ions in the carbonate buffering system?

In the carbonate buffering system, carbonic acid plays a crucial role in maintaining pH balance in water bodies. When hydrogen ions (H+) are added to the water, carbonic acid (H2CO3) can react with these excess hydrogen ions. This reaction helps to moderate changes in pH by forming bicarbonate ions (HCO3-) or carbonate ions (CO3^2-), depending on the conditions. The ability of carbonic acid to combine with hydrogen ions effectively dampens the acidity in aquatic environments, providing stability to the overall ecosystem.

The buffering action of carbonic acid is vital for aquatic life, as even small fluctuations in pH can harm organisms in those ecosystems. Therefore, carbonic acid is a fundamental component of the carbonate system that regulates acidity and maintains the health of aquatic environments.