Biogenic Emission of Reduced Sulfur Gases

As a result of bacterial sulfate reduction and decomposition of organic material, large amounts of reduced sulfur gases are emitted into the atmosphere annually from wetland systems, especially tidally influenced marine sediments and salt marshes (Adams et al., 1979,1981). 

Coastal marshes have the highest aerial gaseous sulfur emissions with rates 10-100 times greater than that from oceans and inland soils. The range of reported emission rates is large, and extreme variability at a given sampling site is common. 

Gaseous sulfur compounds produced in wetlands are either intermediate metabolites or end products of biological processes. Hydrogen sulfide (H2S) produced by dissimilatory sulfate reduction in anaerobic environment was originally thought to be the primary gaseous sulfur source emitted to the atmosphere (Rodhe and Isaken, 1980). 

Wetlands are significant sources of not only H2S but also DMS, methyl mercaptane (methanethiol-MeSH), carbonyl sulfide (COS), DMDS, and carbon disulfide (CSj). 

High rate of DMS emissions from S. alterniflora is attributed to the presence of high concentrations of the DMS precursor dimethylsulfoniopropionate (DMSP in the plant tissue). Enzymatic cleavage of this compound produces DMS plus acrylic acid. S. alterniflora is one of only three plant species containing DMSP, the others being S. anglica and S. foliosa. Spartina patens does not contain DMSP. In general, emissions to the atmosphere are lower than that reported for salt marshes. 

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