Nitrous oxide emission from Gulf Coast wetlands

Nitrous oxide evolution may contribute to partial destruction of the ozone layer in the stratosphere. A two year study of the release of N₂O from adjoining salt, brackish, and fresh marsh sediment indicates that the annual emission was 31, 48, and 55 mg N m^?2 respectively. Emission from open water area was less than the corresponding emission from the marsh sediment. In vitro experiments indicate that the N₂O emission was increased when the sediment was drained for extended periods of time. The addition of NO₃^? significantly increased the rate of N₂O evolution, indicating that a large potential for denitrification exists in the anoxic sediment. Appreciable losses of N₂O would only be expected when the marshes receive an extraneous source of nitrate such as sewage and/or wastewater.The contribution of the Gulf Coast wetlands to the atmospheric N₂O balance is estimated to be 3.3 × 10⁹ g N₂O. The maximum average daily emission was equivalent to 1.5 g N₂O-N ha^?1, which is less than the measured emission from uncultivated soils (Mosieret al., 1981) but greater than the estimates from noncropped land (CAST, 1976).