Drivers of microbial metabolism, nutrient cycling and greenhouse gas production in agricultural streambed sediments

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Comer-Warner, Sophie (2019). Drivers of microbial metabolism, nutrient cycling and greenhouse gas production in agricultural streambed sediments. University of Birmingham. Ph.D.

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Abstract

Drivers of carbon and nitrogen cycling, and associated greenhouse gas (GHG) production, were investigated in streambed sediments. Research was conducted to address a lack of availability of adequate porewater sampling technologies and standard protocols, and to determine the effect of temperature, sediment properties and season as primary drivers of nutrient cycling and GHG production in the streambed. A high-resolution sampler of nitrate isotope and concentration data was developed by confirming diffusive equilibrium in thin-film (DET) gel samplers did not cause fractionation of nitrate isotopes. An investigation of commonly used sampling techniques provided information on the most appropriate samplers to use and illustrated that ammonium concentrations vary significantly between sampling techniques. Thermal sensitivity of CO\(_2\) and CH\(_4\) emissions was dependent on sediment type, organic matter and geology, with these factors having a major effect. CO\(_2\) and CH\(_4\) concentrations were higher in sand than gravel sediments, but season had a minor influence. Nitrogen cycling was highest in sand than gravel sediments, resulting in high rates of denitrification and low N\(_2\)O concentrations in the sand sediments. Nitrogen cycling and associated N\(_2\)O concentrations varied greatly with season in gravel sediments. This indicates that different greenhouse gases may be produced in different areas of the streambed.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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