Nitrogen transformations alkalinity

Nitrogen transformations such as nitrate assimilation, denitrification, and decomposition (eqs 10-12) contribute to alkalinity by consuming H+. In contrast, both ammonium assimilation and nitrification (eqs 13 and 14) consume alkalinity via the production of H +. 

This method may be used for soils, and for groundwater and surface runoff water from catchments. It identifies the mean, long-term sources of acidity and alkalinity in the system and then determines the maximum acid input that will bring about a balance that is biologically safe. Weathering rates, biomass acidity input, acid inputs from nitrogen transformations and alkalinity outflux are estimted. Models like MACAL referred to above can be used or more simple mass balance calculation performed. 

Some of the ammonia thus produced is released from alkaline environments to the atmosphere, where it is relatively inaccessible to biological systems. This form of nitrogen (and others in the atmosphere) is subject to chemical and photochemical transformations, after which they can be returned to the litho- and hydrosphere through water deposition. 

All these phenomena result from the great stability of the species, as pointed out by Michaelis. In determining this stability, an important factor is the protonation at nitrogen, which increases the number of resonance structures. The radical species decays rapidly in neutral and alkaline media, when the reverse of Reaction (3) takes place, followed by subsequent transformations of T+. This was confirmed by Gilbert et al., who found that on diluting the... 

Mineralization of the organic matter begins by transformation of the a-amino groups into ammonia. This conversion is observed in the acid-soluble fraction obtained when carbonates are removed by acid treatment of the sediment prior to alkaline extraction. In this fraction, the ratio of ammonium nitrogen to a-amino nitrogen increases steadily with burial in the first few meters of the sediment (Jocteur-Monrozier and Jeanson, 1981). However, these data are not always easy to interpret due to the dissolution, diffusion, and adsorption of ammonium nitrogen on clay minerals. 

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