title: Inorganic and organic losses of nitrogen from upland regions of Britain: concentrations and fluxes.
abstract: The nitrogen (N) composition of streams draining eight upland regions of Britain was compared using monthly samples collected between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), and dissolved organic nitrogen (DON). Concentrations of TN were small, generally less than 1.5 mg N l(-1), were dominated by dissolved forms of N, and varied significantly between regions. NO3 accounted for the majority of variability. Concentrations of DON also varied between regions but to a smaller extent than those of NO3. There were considerable variations in TN fluxes between upland regions, which ranged between 3.8 and 16.1 kg N ha(-1) year(-1). The majority of the variation was due to NO3 fluxes, which were largest in regions receiving largest inputs of atmospheric N deposition and ranged between 1.4 and 13.5 kg N ha(-1) year(-1). Fluxes of DON ranged between 1 and 3.5 kg N ha(-1) year( -1), while fluxes of PN were generally less than 0.5 kg N ha(-1) year(-1) , and NH4 fluxes ranged between 0.1 and 0.4 kg N ha(-1) year(-1). NO3 was the dominant fraction (47-84%) of N exported from all upland regions except the Highlands, where DON accounted for 52% of the TN flux. This study has shown that the DON fraction is an important component of the total N transported by upland streams in Britain.
authors.affiliation: School of Geography, University of Leeds, UK. p.chapman@geog.leeds.ac.uk
authors.forename: P J
authors.initials: PJ
authors.lastname: Chapman
authors.forename: A C
authors.initials: AC
authors.lastname: Edwards
mesh_terms: D000531:Altitude; D000641:Ammonia / Q000032:analysis; D017753:Ecosystem; D005618:Fresh Water / Q000032:analysis; D005843:Geography; D009566:Nitrates / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D012621:Seasons; D006113:United Kingdom
chemical_list: D009566:Nitrates; D000641:Ammonia; D009584:Nitrogen