Sulfur cycling in a forested Sphagnum bog in northern Minnesota

Abstract

Abstract.The mass balance and internal cycle of sulfur within a small forested, Sphagnum bog in northern Minnesota are presented here based on a 4-year record of hydrologic inputs and outputs (precipitation, throughfall, streamflow, upland runoff) and a 3-year measurement of plant growth and sulfur uptake. Concentrations and accumulation rates of inorganic and organic sulfur species were measured in porewater. The bog is a large sink for sulfur, retaining 37% of the total sulfur input. Because of the relatively large export of organic S (21% of inputs), retention efficiency for total-S (organic S + SO:; 37%) is less than that for SOT (58%). There is a dynamic cycle of oxidation and reduction within the bog. Annual oxidation and recycling of S is equal to total inputs in the center of the bog. Plants receive 47% of their uptake requirement from atmospheric deposition, 5% from retranslocation from foliage, and the remainder from sulfur remineralized from peat. Mineralization is most intense in the aerobic zone above the water table. Inorganic sulfur species comprise < 5% of the total sulfur burden within the peat.

Concentration and chemical species of iron in soils from groundwater/surface water ecotones

“…The reduced S species may be pyrite, organic S and H 2 S. It is likely that pyrite was the dominant reduced compound as Fe/Cl was also three times lower in August than in March. Many studies have shown that accumulation of Fe-sulphides is of minor importance in peatlands (Brown, 1985;Wieder, 1988;Urban et al, 1989). However, although inorganic species such as pyrite are not important pools of S, they may be important as intermediate short term products which transform to organic S (Brown, 1985(Brown, , 1986Urban et al, 1989).…”

“…S0 4 may be too unreactive for a direct chemical incorporation into organic matter. High pH, high Fe concentrations and high S0 4 concentrations have been proposed to enhance the formation of pyrite (Urban et al, 1989), conditions which are fulfilled at H2 and H4. The accumulated amorphous Fe-sulphides, if present, should be extracted by both pyrophosphate and oxalate extractant.…”

“…Alternatively, it could indicate that most of the discharging groundwater was flowing quickly through channels instead of being diffusely filtered through the peat. S0 4 retention may well be more effective when the hydrological conditions maximize the contact time between the water and the soil (Bayley et al, 1986;Urban et al, 1989). Redox potential measurements have suggested that soils in the groundwater discharge zone could have different permeability in different sections (Norrstrôm, unpublished results).…”

Sulfur during early diagenesis in Sphagnum peat: Insights from δ34S ratio profiles in 21Pb‐dated peat cores

“…Bayley et al 1986;Urban et al 1989;Spratt and Morgan 1990). Sulfur retention apparently is not the result of a fraction of the incoming S atoms becoming immobilized within the peat, with the remaining fraction passing through the peatland unaltered.…”

“…Rather, the biogeochemical cycling of S in peat is quite dynamic. The quantity of S that cycles internally through oxidation and reduction reactions in peat may far exceed S inputs (Urban et al 1989;Spratt and Morgan 1990;Wieder et al 1990). Subsurface peaks in total S, organic S, and FeS,-S concentrations, typically I Corresponding author.…”