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This article in JEQ

  1. Vol. 26 No. 4, p. 1049-1055
    Received: July 23, 1996

    * Corresponding author(s): r.v.smith@qub.ac.uk
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Free Ammonia Inhibition of Nitrification in River Sediments Leading to Nitrite Accumulation

  1. R. V. Smith *,
  2. L. C. Burns,
  3. R. M. Doyle,
  4. S. D. Lennox,
  5. B. H. L. Kelso,
  6. R. H. Foy and
  7. R. J. Stevens
  1. Agric. and Environ. Science Div., Dep. of Agric. for Northern Ireland, Newforge Lane, Belfast, BT9 5PX, Northern Ireland;
    Biometrics Div., Dep. of Agric. for Northern Ireland, Newforge Lane, Belfast, BT9 5PX, Northern Ireland;
    Dep. of Agric. and Environ. Science;
    Dep. Biometrics, The Queen's University of Belfast.



Previous studies have reporled that only 40% of nitrite (NO2) in major rivers in Northern Ireland originates from land drainage. The remainder appears to originale from N transformations at the interface between sediment and water within river systems. Streams in two major river catchments in Northern Ireland were monitored for the presence of NO2. Mean NO2 concentrations (which all exceeded 3.0 µg N L−1 which is the European Community (EC) guide values for supporting salmonid fish) ranged from 3.8 to 84.5 µg N L−1 in 14 streams in the Upper Bann and 10.7 to 60.0 µg N L−1 in 14 streams in the Colebrooke river system. Evidence from multiple regression analysis suggested that NO2 accumulation in these streams was associated with the presence of free NH3. Incubation and differential 15N labeling of sediment extracts with ammonium nitrale (NH4NO3) provided support for this hypothesis that showed that the mechanistic process involved in NO2 accumulation is nitrification inhibition rather than denitrification. Free NH3 partially inhibils NO2 oxidation by Nitrobacter, but does not inhibit the oxidation of ammonium (NH+4) by Nitrosomonas. Most of the NH+4 in streams originates from pollution by agricultural effluents and must be curtailed to prevent NO2 accumulation.

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