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Title: Aerobic denitrification in soils : fact or fiction?
Author: Morley, Nicholas Jackson
ISNI:       0000 0001 3422 1598
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2008
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Homogeneous soil slurries were employed for testing the regulating factors for aerobic denitrification. The presence of nitrite, at a relatively high concentration, was a strong inducer of aerobic nitrous oxide production, during which no dinitrogen evolution was measured. High concentrations of nitrite also appeared to inhibit reduction of nitrous oxide under more suitable denitrifying conditions (low oxygen), which resulted in a high denitrifier nitrous oxide-to-dinitrogen ratio. In contrast, dinitrogen production was efficient in near-anoxic slurries when nitrate or low concentrations of nitrite were present. Nitrous oxide and dinitrogen production in soil slurries exhibited various responses with the addition of different carbon compounds. Simple sugars (glucose and mannitol) induced the lowest nitrous oxide production whereas more complex substrates (glutamic acid and butyrate) induced more nitrous oxide under oxic conditions. In addition, no dinitrogen production occurred when slurries were incubated with more than 2% oxygen in the headspace, except when supplemented with butyrate. In addition to soil slurries a culture-based approach was adopted to investigate whether bacterial cells extracted from soil exhibited any aerobic denitrification activity. During the respiratory depletion of oxygen these extracted cells only initiated denitrification when oxygen concentration fell below 10 &'956;M, and once anoxic denitrification was highly efficient with little intermediates accumulating. However, anoxic cells, containing a fully functional denitrification pathway, appeared to sustain denitrification where re-exposed to oxygen. The resulting denitrification was highly perturbed in that nitrous oxide was the dominant product. The results suggest that aerobic denitrification is a possibility in soils and that nitrite might be a replacement. Dynamic changes in oxygen could lead to higher soil nitrous oxide production following an anoxic phase.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available