SULFUR DYNAMICS IN LOUISIANA COASTAL FRESHWATER MARSH SOILS

The profile distribution of specific sulfur forms was examined in a Louisiana freshwater marsh. Soil samples were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur (S°), pyrite sulfur (FeS2), ester-sulfate sulfur, carbon-bonded sulfur, and total sulfur. Inorganic sulfur constituted 14 to 30% of the total sulfur pool, with HCl-soluble sulfur present as the largest portion (77–94%). AVS sulfur accounted for <1% of total soil sulfur. No clear pattern of pyrite sulfur formation was observed in the upper 20 cm of the soil profile; however, concentration tended to increase with depth below this zone. Pyrite sulfur represented <3% of total sulfur and together with elemental sulfur accounted for 6 to 21% of the inorganic sulfur fraction. Elemental sulfur concentration was highest in the plant root zone (<20-cm). Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was a major constituent (70–86%) of total sulfur. Ester sulfate represented between 15 and 34% of the organic sulfur fraction.