Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Lapworth, D. J. ORCID:; Shand, P.; Abesser, C.; Darling, W. G.; Haria, A. H.; Evans, C. D.; Reynolds, B.. 2008 Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales. Science of the Total Environment, 390 (1). 241-254.

Before downloading, please read NORA policies.

Download (537kB) | Preview


The importance of upland groundwater systems in providing a medium for nitrogen transformations and processes along flow paths is investigated within the Afon Gwy moorland catchment, Plynlimon, mid-Wales. Dissolved organic nitrogen (DON) was found to be the most abundant form of dissolved nitrogen (N) in most soils and groundwaters, accounting for between 47 and 72% of total dissolved nitrogen in shallow groundwater samples and up to 80% in deeper groundwaters. Groundwater DON may also be an important source of bio-available N in surface waters and marine systems fed by upland catchments. A conceptual model of N processes is proposed based on a detailed study along a transect of nested boreholes and soil suction samplers within the interfluve zone. Shallow groundwater N speciation reflects the soilwater N speciation implying a rapid transport mechanism and good connectivity between the soil and groundwater systems. Median nitrate concentrations were an order of magnitude lower within the soil zone (< 5–31 μg/L) than in the shallow groundwaters (86–746 μg/L). Given the rapid hydrostatic response of the groundwater level within the soil zone, the shallow groundwater system is both a source and sink for dissolved N. Results from dissolved N2O, N2/Ar ratios and dissolved N chemistry suggests that microbial N transformations (denitrification and nitrification) may play an important role in controlling the spatial variation in soil and groundwater N speciation. Reducing conditions within the groundwater and saturated soils of the wet-flush zones on the lower hillslopes, a result of relatively impermeable drift deposits, are also important in controlling N speciation and transformation processes.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
BGS Programmes 2008 > Groundwater resources
UKCEH and CEH Sections/Science Areas: Emmett
Harding (to July 2011)
ISSN: 0048-9697
Additional Keywords: Dissolved Organic Nitrogen (DON), Groundwater, Denitrification, Nitrification, Nitrate, Transformations, Upland catchments
NORA Subject Terms: Ecology and Environment
Date made live: 09 Jan 2008 11:50 +0 (UTC)

Actions (login required)

View Item View Item

Document Downloads

Downloads for past 30 days

Downloads per month over past year

More statistics for this item...