Gaseous Nitrogen Losses from Gulf Coast Marshes

The low evolution of N2O and NH3 from unamended brackish and salt marsh soils suggests a conservative internal nitrogen cycle exists in Louisiana\u27s coastal marshes. The gaseous evolution of NH3 and N2O increased following the addition of (NH4) 2SO4. The maximum rates of NH3 volatilization from the salt and brackish marshes were 5.7 and 3.2 mg N m_2 d_1, respectively. The corresponding total NH3 volatilization was 34 and 15 mg N m_2 for the salt and brackish marshes. Volatilization from unamended cores amounted to 6.0 and 0.9 mg NH3-N m_2 from the salt and brackish marshes. Approximately 29 and 15 mg N2O-N m_2 was evolved from the brackish and salt marsh sediment amended with 1243 and 1469 mg NH4+ -N m_2. The N2O evolution from the unamended cores was 0.4 and 2.2 mg N m_2 from the brackish and salt sediment

Distribution of organic and reduced sulfur forms in marsh soils of coastal Louisiana

Soil samples from a Louisiana Barataria Basin brackish marshes were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester-sulfate sulfur, and carbon-bonded sulfur. Inorganic sulfur composed 13% of total sulfur in brackish marsh soil with HCl-soluble sulfur representing 63–92% of the inorganic sulfur fraction. AVS represented less than 1% of the total sulfur pool. Pyrite sulfur and elemental sulfur together accounted for 8–33% of the inorganic sulfur pool. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, was the most dominant pool representing the majority of total sulfur in brackish marsh. Results were compared to values reported for fresh and salt marshes. Reported inorganic sulfur fractions were greater in adjacent marshes, constituting 24% of total sulfur in salt marsh, and 22% in freshwater marshes. Along a salinity gradient, HCl-soluble sulfur represented 78–86% of the inorganic sulfur fraction in fresh, brackish, and salt marsh. Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was the major constituent (76–87%) of total sulfur in all marshes. Reduced sulfur species, except elemental sulfur, increased seaward along the salinity gradient. Accumulation of reduced sulfur forms through sedimentation processes was significant in marsh energy flow in fresh, brackish and salt marshes