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Denitrification in riparian buffer zones - OC9114

There is great pressure on the agricultural industry to reduce the amount of nitrate entering surface and groundwaters from farmed land. Research currently being conducted at the School of Geography, Oxford University by N E Haycock and T P Burt has established that undrained floodplains may function effectively as nutrient retention zones between intensively farmed land and surface watercourses. Results from a field site in the Cotswolds show that there is a sharp reduction in the nitrate concentration of groundwater as it drains across a floodplain into the stream. This effect was observed in winter when nitrate concentrations were at there largest (there was no flow at this site during summer). Denitrification is the most likely cause. However, it has not yet been possible to make measurements of denitrification in floodplain soils. Further work is required to establish the extent to which denitrification occurs generally in riparian zones and weather it occurs at the surface or at depth, perhaps at or below the water table. It is important to determine the importance of denitrification with respect to (i) the control of nitrate concentrations in rivers and lakes, and (ii) the emission of nitrous oxide (N2O) to the atmosphere. The overall objective of the project is to: (i) Determine suitable techniques for measuring denitrification in riparian zones; (ii) Apply these techniques to a number of riparian zones with different hydrological and sedimentological characteristics; (iii) Assess the functional role of riparian zones as sites for nitrate loss from drainage waters via denitrification. Given the vulnerability of surface waters to nitrate pollution from agricultural land, floodplain land may provide important buffer zones between intensively farmed land and rivers used for public water supply. This project will assess the degree to which undrained floodplains provide such a buffer and the degree to which the denitrification process contributes to emissions of N2O to the atmosphere. The work may give some further indication of the factors that control the ratio of N2O:N2 produced, offering the possibility of manipulating the process to maximise N2 production. The project may well lead to guidelines for the manipulation of floodplain drainage aimed at maximising nitrate losses and minimising both water and atmospheric pollution. In this way, control of land on floodplains can contribute to catchment management policies. The project should provide a basis for the development of a model of nitrate movement in riparian zones.
Project Documents
• EVID4 - Final project report : OC9114 Denitrification in riparian buffer zones   (740k)
Time-Scale and Cost
From: 1993

To: 1996

Cost: £112,151
Contractor / Funded Organisations
University - Oxford
Fields of Study
Fertilisers and Nitrate Pollution