Modelling Denitrification In Soil

Denitrification is a process used by many bacterial species to support anaerobic respiration, where, faced with a lack of oxygen, energy is instead created from available nitrates. Arable soils with high nitrogen content, and commonly-used fertilisers, encourage this process. Unfortunately, the ultimate impact on the environment is negative since nitrous oxide gas, which emerges as a bi-product, escapes into the atmosphere where it presents a 300-fold greater danger for global warming than carbon dioxide. The aim of this thesis is find a way to estimate the level of nitrous oxide which may escape into the atmosphere from denitrifying soil. Traditionally, the chain of chemical reactions followed in the denitrification process is modelled using Michaelis-Menten kinetics. We begin this thesis by reviewing existing work, discussing some of its limitations and proposing various alterations. Later, we present a preliminary model of the oxygen distribution within a soil with the aim of identifying anaerobic micro-sites where bacteria can denitrify. Our first models consist of a solitary circle of oxygen-absorbing soil residing beneath ground level in an environment saturated with oxygen. We show that normal respiration occurs inside the circle except within a core anaerobic region where denitrification occurs. We extend the oxygen distribution model by generalising to multiple oxygen-absorbing regions. The model is then considered from two viewpoints. We either think of the model as an aggregated soil where each circle represents an individual aggregate surrounded by air. Or we think of the model as a solid non-aggregated soil, where each circle represents a high respiration area. For both of these viewpoints results are found for realistic parameters and levels of denitrification within the soil can be estimated.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Bocking, Christopher

Language dc:language

en