Nitrogen in the Earth: abundance and transport

Abstract

The terrestrial nitrogen budget, distribution, and evolution are governed by biological and geological recycling. The biological cycle provides the nitrogen input for the geological cycle, which, in turn, feeds some of the nitrogen into the Earth's interior. A portion of the nitrogen also is released back to the oceans and the atmosphere via N 2 degassing. Nitrogen in silicate minerals (clay minerals, mica, feldspar, garnet, wadsleyite, and bridgmanite) exists predominantly as NH 4 +. Nitrogen also is found in graphite and diamond where it occurs in elemental form. Nitrides are stable under extremely reducing conditions such as those that existed during early planetary formation processes and may still persist in the lower mantle. From experimentally determined nitrogen solubility in such materials, the silicate Earth is nitrogen undersaturated. The situation for the core is more uncertain, but reasonable Fe metal/silicate nitrogen partition coefficients (> 10) would yield nitrogen contents sufficient to account for the apparent nitrogen deficiency in the silicate Earth compared with other volatiles. Transport of nitrogen takes place in silicate melt (magma), water-rich fluids, and as a minor component in silicate minerals. In melts, the N solubility is greater for reduced nitrogen, whereas the opposite appears to be the case for N solubility in fluids. Reduced nitrogen species (NH 3 , NH 2 − , and NH 2 +) dominate in most environments of the modern Earth's interior except the upper~100 km of subduction zones where N 2 is the most important species. Nitrogen in magmatic liquids in the early Earth probably was dominated by NH 3 and NH 2 − , whereas in the modern Earth, the less reduced, NH 2 + functional group is more common. N 2 is common in magmatic liquids in subduction zones. Given the much lower solubility of N 2 in magmatic liquids compared with other nitrogen species, nitrogen dissolved as N 2 in subduction zone magmas is expected to be recycled and returned to the oceans and the atmosphere, whereas nitrogen in reduced form(s) likely would be transported to greater depths. This solubility difference, controlled primarily by variations in redox conditions, may be a factor resulting in increased nitrogen in the Earth's mantle and decreasing abundance in its oceans and atmosphere during the Earth's evolution. Such an abundance evolution has resulted in the decoupling of nitrogen distribution in the solid Earth and the hydrosphere and atmosphere.

Particular H2O dissolution mechanism in iron‐rich melt: Application to martian basaltic melt genesis

“…The Q Si─O─Si corresponds to the vibration of the interconnected oxygen between two tetrahedral Q n units as stated in previous studies, although Trcera et al assigned it to Q 3 species. Considering the work of Micoulaut et al and Mysen, and the low NBO/T of our glasses (i.e., <1), Q 1 species cannot be present. Indeed, all the Q n species that can be present are following the equilibrium: …”

On the Crystal Chemistry of Inorganic Nitrides: Crystal-Chemical Parameters and Opportunities in the Exploration of Their Compositional Space

“…Based on the similar crystal-chemical behavior of these classes of compounds, their significant overlap in cation configurations, and the isoelectronic nature of N 3-and O 2-, we assume that cation configurations yetto-be-observed in inorganic nitrides with equal or lower oxidation states and/or coordination numbers than their oxide and oxysalt counterparts either result from challenging synthesis or lack of synthetic attempts. Comparing the dataset of Gagné & Hawthorne against the present work for cation configurations with bonds > 1 v.u., we conclude that promising opportunities for multiple bond-formation (1)(2)(3) v.u.) in inorganic nitrides include cations such as Ti 4+ , V 4+ , As 5+ , Se 4,6+ , Br 5+,7+ , Mo 5+ , Tc 7+ , Te 4,6+ , I 5,7+ , W 5+ , Re 7+ , Os 6,7,8+ , Bi 5+ , U 6+ and Np 5,6,7+ ; further work is also warranted for V 5+ , Cr 5,6+ , Nb 5+ , Mo 6+ , Ta 5+ and W 6+ .…”

“…The predominance and variety of oxide and oxysalt compounds as minerals in Earth's crust means that they were inevitably among the first materials to be methodically characterized and examined for interesting properties, occupying scientists for decades in trying to decipher, reproduce, and enhance their behavior. Conversely, inorganic nitrides, here defined as ionic/covalent compounds with N 3-as the main anion, are a relatively-unexplored class of compounds owing to (1) the scarcity of nitrogen minerals in Earth's crust due to various biological and geological transport processes drawing nitrogen away from the crust 1 (not limited to their reaction with water to form hydroxides and ammonia 2 ), and (2) challenging synthesis. 3 Systematic investigation of nitrides began in the late 1930s with the work of Juza and collaborators who mainly focused on lithium compounds for their relative ease of preparation.…”

Understanding the Structure and Structural Effects on the Properties of Blast Furnace Slag (BFS)

“…So in binary alkali silicate melts viscosity might positively correlated with the amount of Q 4 units. 81) As shown in Fig. 7(c), viscosity (ln η) of the silicate melts increases linearly as ln (Q 3 /Q 2 ) increases at 1 873 K and 1 773 K. The value of ln (Q 3 /Q 2 ), can be measured and it can work as a vital polymerization index to determine the relationship between silicate structure and viscosity of the melts.…”