Sulfur salt marshes

Luther, GW., HI et ah Inorganic and Oiganic Sulfur Cycling in Salt-Marsh Poie Waters, Science. 232, 746 -749 (1986). 

Peterson, B. J., and R. W. Howarth. 1987. Sulfur, carbon, and nitrogen isotopes used to trace organic matter flow in the salt-marsh estuaries of Sapelo Island, Georgia. Limnology and Oceanography 32 1195-1213. 

There have been a number of studies of biogenic emissions of sulfur gases other than H2S reported in the literature. Most of these have been concerned with high productivity sources, such as salt marshes and tidal areas and are summarized in Table II. 

Many of the previous direct flux measurements have focused on two distinct ecosystems, intertidal mudflats and Spartina altemiflora salt marshes. These coastal systems have the potential for large emissions of volatile reduced sulfur gases due to the availability of sulfate and organic matter. Intertidal mudflats (3.4) have a tendency towards anoxia, with concomitant production of H S via sulfate reduction. . altemiflora marshes (4T5) release DMS through the... 

The low emission rates measured in this study indicate that salt marshes are a minor source of sulfur to the global atmosphere. Furthermore, our measurement of deposition rates show the potential for losses to the same soil surfaces at times of elevated atmospheric concentration. 

Bacterially produced elemental sulfur can also react with hydrogen sulfide form polysulnde ions. Thus, polysulfide ions should constitute a significant fraction of sulfur nudeophiles in reducing sediments especially where sulfide oxidation is incomplete, such as in intertidal and salt marsh sediments (31321. The polysulfide ions should also be important at redox boundaries (anoxic/ suboxic) in the water column of marine anoxic basins, such as the Black Sea. 

In marine and lacustrine muds, the initial sulfide phase precipitated during early diagenesis is mackinawite (FeS09) which is subsequently converted to greigite (Fe3S4) and pyrite (FeS2) (85-89). This reaction path leads to the formation of framboidal pyrite (88.90). However, in salt marsh sediments under low pH and low sulfide ion activity conditions, direct precipitation of pyrite by reaction of ferrous iron with elemental sulfur without the formation of iron monosulfides as intermediates has been reported (85-87.89.91.92). This reaction is one possible pathway for the precipitation of pyrite as single crystals (89). 

Tne question of the source molecule occurrence must be addressed. The coincidence in anaerobic environments of ammonia and reduced divalent sulfur species, which includes hydrogen sulfide, bisulfide anion and sulfide dianion, has been given adequate recognition. (See for example references 36,37.) The coincidence of polysulfide and ammonia has already been noted in an earlier part of this report (1). Polysulfide has been found in tidal and salt marsh sediments as well (38). 

Stable sulfur isotopes can be effectively used to examine important geochemical processes associated with redox changes in sedimentary environments. For example, S042- reduction in salt marsh sediments yields isotopically depleted 534S porewater sulfide the uptake of H2S by marsh plants also results in isotopically depleted [Pg.173]

Gardner, L.R., Wolaver, T.G., and Mitchell, M. (1988) Spatial variations in the sulfur chemistry of salt marsh sediments at North Inlet, South Carolina. J. Mar. Res. 46, 815-836. 

Howarth, R.W. (1984) The ecological significance of sulfur in the energy dynamics of salt marsh and coastal sediments. Biogeochemistry 1, 5-27. 

King, G.M. (1988) Patterns of sulfate reduction and the sulfur cycle in a South Carolina salt marsh. Limnol. Oceanogr. 33, 376-390. 

King, GM., Howes, B.L., and Dacey, J.W.H. (1985) Short-term endproducts of sulfate reduction in a salt marsh the significance of acid volatile sulfide, elemental sulfur, and pyrite. Geochim. Cosmochim. Acta 49, 1561-1566. 

Luther III, G.W., and Church, T.M. (1988) Seasonal cycling of sulfur and iron in porewaters of a Delaware salt marsh. Mar. Chem. 23, 295-309. 

Luther III, G.W., Church, T.M., Scudlark, J.R., and Cosman, M. (1986) Inorganic and organic sulfur cycling in salt-marsh pore waters. Science 232, 746-779. 

Peterson, B.J., Howarth, R.W., and Garritt, R.H. (1986) Sulfur and carbon isotopes as tracers of salt-marsh organic matter flow. Ecology 67, 865-874. 

Howarth, R. W. and J. M. Teal. 1979. Sulfur reduction in New England salt marsh. Limnol. Oceanogr. 24 999—1013. 

Ferdelman T. G., Church T. M., and Luther G. W., Ill (1991) Sulfur enrichment of humic substances in a Delaware salt marsh sediment core. Geochim. Cosmochim. Acta 55(4), 979-988. 

Kiene R. P. and Capone D. G. (1988) Microbial transformations of methylated sulfur compounds in anoxic salt marsh sediments. Microbiol. Ecol. 15, 275-291. 

Speciation of Dissolved Sulfur in Salt Marshes by Polarographlc Methods... 

Sulfur speciation In the porewaters of two salt marshes (Great Marsh, Delaware and Great Slppewlssett, Cape Cod, Massachusetts) are presented. A major finding Is that the porewaters from Great Slppewlssett salt marsh are dominated by Inorganic sulfur species throughout the depth profile. 

---