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EMERGY ANALYSIS OF THE PREHISTORIC NITROGEN CYCLE
Citation:
Campbell, D E. EMERGY ANALYSIS OF THE PREHISTORIC NITROGEN CYCLE. The Proceedings of the 2nd Biennial Emergy Evaluation and Research Conference, Gainsville, FL, September 20-22, 2002.
Description:
Several relationships between the specific emergy or the emergy per unit mass and the mass concentration of nitrogen were shown to exist through an analysis of the global nitrogen cycle. These observed relationships were interpreted by examining the nature of the underlying energy transformation and the configuration of the network in which energy was being transformed. A primary pattern observed in the data showed a monotonic increase in the specific emergy as a function of increasing mass concentration of the material as postulated by the proposed sixth law of thermodynamics. This pattern of specific emergy is to be expected when energy is transformed through a hierarchical network such as a trophic or geochemical web. In this case the increased specific emergy is reflected by an increase in the concentration of the material in higher transformity units. A different pattern with specific emergy decreasing as a function of mass concentration was observed for nitrogen species in the troposphere. In this case, high energy pulses of lightning create nitrogen species of higher transformity by breaking the stable triple bond of diatomic nitrogen and increasing the chemical reactivity of nitrogen rather than by accruing greater mass concentrations. Transformity and the emergy per unit mass are greater for the more reactive but lower concentration nitrogen species that result. A final set of patterns for specific emergy as a function of mass concentration result from the unique properties of nitrogen cycling through living systems. In the initial, energy-capturing, material loop of the biosphere; there is a small increase in the emergy per mass but a large increase in mass concentration as disordered forms of nitrogen, e.g, ammonia, are transformed into the more ordered forms of nitrogen in plant matter. The emergy per unit mass increases as energy is transformed and nitrogen concentrated through the trophic web that is built upon this initial loop. In addition, oxidized nitrogen species have increased specific emergy relative to ammonia, perhaps reflecting the additional energy transformation required for nitrification. This analysis of the global nitrogen cycle supports the hypothesis that elements may manifest unique or emergent properties when they achieve sufficient concentrations as predicted by the proposed sixth law. Specifically, it appears that minima in the transformity and specific emergy of mass flows may accompany system states where maximum empower is being generated by a network of interactions.