Nitrogen oxide trace gas transport and transformation: i. evaluation of data from intact soil cores
2002
Venterea, Rodney T. | Rolston, Dennis E.
Once emitted to the atmosphere, nitric oxide (NO) and nitrous oxide (N2O) regulate several important processes in the troposphere and stratosphere. Understanding controls over N oxide gas emissions from fertilized soils is often complicated by highly heterogeneous and dynamic field conditions. An intact soil core method is described here for examining multiple subsurface controls concurrently with N oxide surface fluxes under hydrostatic and isothermal conditions dominated by Fickian diffusive transport. The method allows for simultaneous measurement of inorganic N levels, pH, water content, and soil-gas concentrations of NO, N2O, O2, and CO2 and for subsequent calculation of N mass balances, net nitrification rates, CO2 respiration rates, O2 uptake rates, fraction of nitrified N lost as gas, and anaerobic microsite fraction profiles. The method is applied to moderately acidic soil fertilized with anhydrous ammonia. Steady nitrification and persistent NO2 levels resulted in NO gaseous losses representing 22–37% of the inorganic N initially present and >50% of the nitrified N. Of the initial N mass present, 96–119% was accounted for as N solutes and gases. High N2O soil-gas concentrations (5–20 mg N m) and fluxes (1 mg N m h) persisted despite anaerobic fractions of ≤ 10 m anaerobic soil m soil, suggesting that N2O sources other than denitrification were important.
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