What type of ammonia is significantly more toxic to aquatic life?

Unionized ammonia (NH3) is significantly more toxic to aquatic life compared to ionized ammonia (NH4+). This is due to its greater ability to permeate biological membranes, leading to a more profound impact on cellular physiology. NH3 can readily cross cell membranes and disrupt cellular processes, such as enzyme function and cellular respiration, which can be detrimental to aquatic organisms.

In contrast, ionized ammonia (NH4+) is less toxic because it is more polar and less capable of crossing membranes, thereby having a reduced impact at the same concentrations in water. Other forms mentioned, such as partially ionized ammonia and ammonium sulfate, do not exist as significantly toxic entities in the same manner as unionized ammonia. Ammonium sulfate, for instance, is a stable compound that dissociates into ions in solution and does not pose the same level of toxicity as free NH3. Understanding the distinction between these forms of ammonia is critical in assessing water quality and its impact on aquatic ecosystems.