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Oxidation of Ammonium to Nitrite Under Iron-Reducing Conditions in Wetland Soils: Laboratory, Field Demonstrations, and Push-Pull Rate Determination

Shrestha, Junu1; Rich, Jeremy J.2; Ehrenfeld, Joan G.3; Jaffe, Peter R.1

doi: 10.1097/SS.0b013e3181988fbf
Technical Article

Nitrite (NO2) in soils has been observed under a variety of field conditions. The formation of NO2 in soils is possible during nitrification or denitrification depending on the soil conditions. This study presents a series of experiments performed at different scales that demonstrate the production of NO2 under iron-reducing conditions, in the absence of an initial nitrate pool. These experiments were performed either in a riparian wetland in New Jersey or in laboratory experiments using soils from the same location. The rates of use of NO2 and ammonium (NH4+) determined in situ by performing push-pull experiments were of the same magnitude, supporting the observation of a steady-state NO2 pool under such anaerobic conditions. An isotope experiment performed with 15NH4+ conclusively showed an existence of a pathway linking NH4+ to dinitrogen gas under anaerobic iron-reducing conditions, in the absence of initial nitrate or NO2. Such observations indicate a possibility for the complete removal of NH4+ from wetland soils under anaerobic conditions that develop when soils are water saturated.

1Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544. Dr. Jaffe is corresponding author. E-mail: jaffe@princeton.edu

2Center for Environmental Studies, Brown University, Providence, RI 02912.

3Department of Ecology, Evolution & Natural Resources, Cook College, Rutgers University, New Brunswick, NJ.

Received June 29, 2008, and in revised form Dec. 10, 2008.

Accepted for publication Dec. 11, 2008.

© 2009 Lippincott Williams & Wilkins, Inc.