Nitrogen Transformations

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© 2017 Elsevier Inc. All rights reserved. Nitrogen (N) is a key element in the biology of all organisms and an important pollutant in streams and the water bodies they feed into. Understanding N availability and transport requires elucidation of the major fluxes in the nitrogen cycle. In this chapter, we discuss measurement of some of the most important N fluxes: (1) actual and potential denitrification (the conversion of nitrate to nitrogen gas), (2) gross and net nitrification (the conversion of ammonium to nitrate), and (3) nitrogen fixation (the assimilation of nitrogen gas into organic N) as standard assays. More advanced methods make use of stable isotopes of nitrogen (15N) and membrane inlet mass spectrometry to trace N fluxes; we discuss application of these techniques to measure dissimilatory conversion of nitrate to ammonium as well as net flux of nitrogen gas as influenced by denitrification and nitrogen fixation.

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Methods in Stream Ecology: Third Edition