FORMATION OF VOLATILE SULFUR-COMPOUNDS IN SALT-MARSH SEDIMENT AS INFLUENCED BY SOIL REDOX CONDITION

The effect of soil redox condition on the production or formation of gaseous sulfur compounds in anaerobic salt marsh soil was studied. Marsh soil from a Louisiana Gulf Coast Spartina alterniflora salt marsh was incubated under controlled soil redox potentials ranging from +220 mV to -240 mV, which represent a range in anaerobic soil conditions. The gas phase production of hydrogen sulfide, methanethiol, dimethyl sulfide, carbonyl sulfide, and carbon disulfide as influenced by soil redox level was quantified. Total reduced sulfur gases increased with decreasing soil redox potential. Percentage composition of the individual sulfur gases varied depending on soil redox level. Methanethiol, dimethyl sulfide and carbon disulfide progressively increased with decrease in soil redox level. A major increase in hydrogen sulfide was measured at redox potential of -100 mV and below. Likewise a significant increase in carbonyl sulfide was observed between -70 and -100 mV. Results show that intensity of soil reduction or degree of anaerobiosis is important in the production of these gaseous sulfur compounds.