Premium
Thermodynamics of Inorganic Nitrogen Transformations
Author(s) -
Lindsay W. L.,
Sadiq M.,
Porter L. K.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500010014x
Subject(s) - redox , denitrification , chemistry , metastability , nitrogen , chemical stability , limiting , chemical reaction , chemical equilibrium , inorganic chemistry , thermodynamics , organic chemistry , mechanical engineering , physics , engineering
Standard free energies of formation for various inorganic N species were selected from the literature and used to calculate equilibrium constants for reactions involving various inorganic N species. These reactions were systematized into stability diagrams and used to discuss possible N transformations that may occur in soils. The developments show that N 2 (g) is the only stable N species in the redox range of pe + pH of 4 to 18. At lower redox NH 4 + is stable, whereas at higher redox NO 3 ‐ is stable. Stability diagrams were developed on the basis that first N 2 , then N 2 O, and finally N 3 ‐ do not attain equilibrium with other inorganic N species. These diagrams provide insight into possible reaction sequences that may be involved in chemical denitrification. The hypothesis proposed herein is that NO 0 (nitric oxide) and possible H 2 N 2 O 2 (hyponitrous acid) may be rate‐limiting intermediates in chemical denitrification. These N species are metastable but reach maximum stability in the narrow redox range of pe + pH 13.5 to 14.0. The possibility that these species may be the kinetically feasible intermediates in chemical denitrification are discussed.