This research is designed to assess the potential of freshwater wetlands to accumulate anthropogenic sulfur. The work is predicated on the observation that under certain circumstances, stable sulfur isotope analysis can distinguish the origin of sulfur compounds within sediments. These analyses, combined with precise measurements of sulfur pool sizes and sulfate reduction rates, can determine if and to what extent, sulfur is accumulating within wetland peat, in what form, and from what source. Both a modeling and an experimental approach (including laboratory and whole watershed manipulation) are used to detail the important processes affecting sulfur cycling. The total sulfur pool is considered as three separate subfractions: reduced inorganic sulfur (RIS), organic ester sulfate (ES), and organic carbon bonded sulfur (CBS), and analyzed for pool size, stable sulfur isotope ratio, and rate of formation and breakdown. The role of organic substrates and sulfate concentration in controlling the rate of reduced sulfur formation is also examined. The bulk of this research will be carried out in a well studied wetland in the New Jersey Pinelands. An important adjunct to this research will be participation in an interdisciplinary and international research effort called HUMEX in Norway. HUMEX is a whole watershed acidification of a Sphagnum-dominated wetland and humic lake that is similar to wetlands and surface waters in the Pinelands. The results from this study will make important contributions to ecosystem ecology by 1) documenting the importance of wetland S biogeochemical cycling in regulating watershed S flux, 2) providing the first direct evidence on the long-term storage products of dissimilatory sulfate reduction in freshwater wetland peat, 3) identifying the important processes regulating S flux in wetland peat, and 4) testing the generalizability of these mechanisms to other systems. Dr. Morgan is a leading wetland ecosystem scientist with expertise in sulfur biogeochemistry. The facilities for this research are outstanding.
