Spatial variation in concentrations of dissolved nitrogen species in an upland blanket peat catchment.
The concentration of nitrogen (N), particularly as nitrate (NO3-N), in upland streams, lakes and rivers is frequently used as a diagnostic of the vulnerability of upland ecosystems to increased atmospheric nitrogen deposition and N saturation. The N content of running waters, however, is generally assessed on the basis of sampling at a limited number of points in space and time within the catchment under investigation. The current study was conducted at Trout Beck, an 11.5 km2 blanket peat-dominated catchment in the North Pennine uplands of the UK. Results from sampling at 33 sites within this catchment demonstrated that the concentrations of all dissolved N species were highly variable, even over short distances. Statistical relationships between the concentrations of NO3-N and dissolved organic nitrogen (DON) and percentage catchment cover of Calluna/Eriophorum and Eriophorum vegetation were found. However, it was also noted that in catchments containing limestone outcrops, NO3-N concentration was much higher than in catchments where runoff was sourced directly from the blanket peat surface. It is possible that NH4-N and DON leached from the blanket peat are mineralised and nitrified, providing a source for the NO3-N found in the river channels. Overall, the current study suggests that interpretations of N-saturation based on river water chemistry measurements at a single point must be treated cautiously, and that the influence of catchment-scale physical factors, such as vegetation and geology cover on the concentration of dissolved N species in upland river waters should not be ignored.
Cundill
A P
AP
School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK. Alan.Cundill@sepa.org.uk
Chapman
P J
PJ
Adamson
J K
JK
D002118:Calcium / Q000032:analysis; D002119:Calcium Carbonate; D029795:Calluna; D029785:Cyperaceae; D004784:Environmental Monitoring; D009566:Nitrates / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D045483:Rivers; D012987:Soil; D006113:United Kingdom; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply
D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012987:Soil; D014874:Water Pollutants, Chemical; D002119:Calcium Carbonate; D009584:Nitrogen; D002118:Calcium