High fluvial export of dissolved organic nitrogen from a peatland catchment with elevated inorganic nitrogen deposition

D A Edokpa; M G Evans; J J Rothwell

doi:10.1016/j.scitotenv.2015.06.072

High fluvial export of dissolved organic nitrogen from a peatland catchment with elevated inorganic nitrogen deposition

Sci Total Environ. 2015 Nov 1:532:711-22. doi: 10.1016/j.scitotenv.2015.06.072. Epub 2015 Jun 25.

Authors

D A Edokpa¹, M G Evans², J J Rothwell²

Affiliations

¹ Upland Environments Research Unit, School of Environment, Education and Development, The University of Manchester, Oxford Road, M13 9PL, United Kingdom. Electronic address: donald.edokpa@manchester.ac.uk.
² Upland Environments Research Unit, School of Environment, Education and Development, The University of Manchester, Oxford Road, M13 9PL, United Kingdom.

PMID: 26119385
DOI: 10.1016/j.scitotenv.2015.06.072

Abstract

This study investigates seasonal concentrations and fluxes of nitrogen (N) species under stormflow and baseflow conditions in the peat dominated Kinder River catchment, south Pennines, UK. This upland region has experienced decades of high atmospheric inorganic N deposition. Water samples were collected fortnightly over one year, in combination with high resolution stormflow sampling and discharge monitoring. The results reveal that dissolved organic nitrogen (DON) constitutes ~54% of the estimated annual total dissolved nitrogen (TDN) flux (14.3 kg N ha(-1) yr(-1)). DON cycling in the catchment is influenced by hydrological and biological controls, with greater concentrations under summer stormflow conditions. Dissolved organic carbon (DOC) and DON are closely coupled, with positive correlations observed during spring, summer and autumn stormflow conditions. A low annual mean DOC:DON ratio (<25) and elevated dissolved inorganic N concentrations (up to 63μmoll(-1) in summer) suggest that the Kinder catchment is at an advanced stage of N saturation. This study reveals that DON is a significant component of TDN in peatland fluvial systems that receive high atmospheric inputs of inorganic N.

Keywords: Baseflow; DON; N saturation; Peat; South Pennines; Stormflow.