Organic ammonium ions, soil-water

Equation 8.9 shows that when NH3 is introduced to an acid solution, it reacts directly with the acid and produces the ammonium ion (NH4) (see Chapter 12). Concurrent with Equation 8.9, NH3 may associate itself with several water molecules (NH3nH20) without coordinating another H+. This hydrated NH3 is commonly referred to as unionized ammonia and is toxic to aquatic life forms at low concentrations. Because NH3 is a volatile gas, some of it may be lost directly to the atmosphere (volatilization) without dissolving in solution. On the other hand, the ammonium ion may undergo various reactions in the soil water that may alter its availability to plants and/or other organisms. These reactions include formation of metal-ammine complexes, adsorption on to mineral surfaces, and chemical reactions with organic matter. [Pg.329]

The equilibrium between these two species is regulated by the pH of the solution they are present in. The ammonium nitrogen, as described earlier, is derived from several sources such as ammo-nification of organic nitrogen and inputs from external sources (fertilizers, wastewater, and rainfall). Ammonium ions present on the exchangeable sites are in equilibrium with those in the soil solution or pore water. Ammonium ions in solution are converted to ammonia gas through Equations 8.4 and 8.5 ... [Pg.284]

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