School of GeoSciences

School of GeoSciences

Willena McAuley BSc (Edin), MRes (Lanc)
PhD thesis: Diffuse Nitrate Pollution: Improving mitigation and reducing pollution swapping

Supervisors: David Reay, Kate Heal, Keith Smith
Institute: Atmospheric and Environmental Sciences
Address: Rm 309, School of Geosciences; Crew Building;
West Mains Road; Edinburgh; EH9 3JN
Phone: +44 (0) 131 6517034

Agricultural practices have and continue to increase, the amount of leached reactive nitrogen (N) from farmland reaching aquatic ecosystems. Riparian areas represent the transitional area between terrestrial and aquatic environments and as a result play an important role in intercepting diffuse N pollution from agricultural leachate and run-off.
Field-edge buffer strips are a remediation strategy that has great potential for mitigating diffuse nitrate (NO3-) pollution. However the microbial process – denitrification - exploited to remove diffuse NO3- pollution may result in increased Nitrous oxide (N2O) emissions and so swap a water pollution issue for a climate change problem.

My research is concerned with nitrogen pollution swapping in grassland buffer strips. Nafferton Farm, Northumberland, is the site of Newcastle University’s land-based research facility where numerous runoff interception and mitigation strategies for surface and groundwater systems are currently under investigation. It is also a commercial enterprise employing both organic and conventional farming methods to produce, milk, beef, cereals, oilseed rape and vegetables. Within the organic sector of Nafferton Farm, two grassland plots each with several static gas flux chambers and one automated flux chamber were used to measure weekly and daily N2O fluxes respectively. These were used to identify seasonal variations in N2O fluxes. One grassland plot was irrigated each day for three and a half hours with NO3--rich agricultural drainage water, the other served as a control plot.

Initial results revealed surface drainage water from Nafferton farm is highly polluted, with NO3- concentrations exceeding 100 mg NO3- l-1 during times of greatest surface runoff. The highest N2O emissions from both the buffer strip and control plot occurred within the non-growing season, when the vegetative cover was low and mild winter temperatures apparently allowed denitrification to continue apace. High rainfall events were associated with high N2O emissions across the both plots. Monthly N2O emissions from the control plot ranged from 0.2 – 3.57 mg N2O-N m-2 d-1 whereas those observed from the irrigated buffer strip plot ranged from 0.32 – 5.72 mg N2O-N m-2 d-1.


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