Modeling of sulfur sequestration in coastal marsh soils

In transgressive coastal areas, marshes form in response to sea-level rise and they generally represent an ideal environment for the sequestration of S species. Various predictions in rates of sea-level rise associated with global warming and concern for potential environmental problems from acid-sulfate weathering have prompted interest in modeling rates of S sequestration during coastal marsh pedogenesis. In this study, predictive models were derived for organic and pyrite S using data from pedons along two marsh transects in Dorchester County, MD, Organic S accumulates mainly in the organic horizons, and the rate is mainly driven by sea-level rise. Rates of organic S accumulation for the last 150 yr averaged 4.3 +/- 1.19 g m(-2) yr(-1); before this, long-term rates ranged between 0.95 and 2.05 g m(-2) yr(-1). Pyrite S sequestration reflects accumulations both in organic horizons and in the submerged mineral soil. The rate of pyrite sequestration in organic horizons is generally driven by sea-level rise and the availability of reactive Fe. During the last 150 Jr, the rates of pyrite accumulation averaged 7.2 +/- 1.6 g m(-2) yr(-1); before this, long-term rates ranged between 0.53 and 1.14 g m(-2) yr(-1). Modeled predictions of pyrite and organic S accumulations in newly forming marshes during the next century were 15 +/- 4.3 g m(-2) yr(-1) and 19 +/- 8.2 g m(-2) yr(-1), respectively.