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Seasonal and event variations in δ 34 S values of stream sulfate in a Vermont forested catchment: Implications for sulfur sources and cycling

James B. Shanley·Bernhard Mayer·Myron J. Mitchell·Scott W. Bailey
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Abstract

Stable sulfur (S) isotope ratios can be used to identify the sources of sulfate contributing to streamwater. We collected weekly and high-flow stream samples for S isotopic analysis of sulfate through the entire water year 2003 plus the snowmelt period of 2004. The study area was the 41-ha forested W-9 catchment at Sleepers River Research Watershed, Vermont, a site known to produce sulfate from weathering of sulfide minerals in the bedrock. The δ 34 S values of streamwater sulfate followed an annual sinusoidal pattern ranging from about 6.5‰ in early spring to about 10‰ in early fall. During high-flow events, δ 34 S values typically decreased by 1 to 3‰ from the prevailing seasonal value. The isotopic evidence suggests that stream sulfate concentrations are controlled by: (1) an overall dominance of bedrock-derived sulfate ( δ 34 S ~ 6–14‰); (2) contributions of pedogenic sulfate ( δ 34 S ~ 5–6‰) during snowmelt and storms with progressively diminishing contributions during base flow recession; and (3) minor effects of dissimilatory bacterial sulfate reduction and subsequent reoxidation of sulfides. Bedrock should not be overlooked as a source of S in catchment sulfate budgets.

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Science of the Total EnvironmentArticle
90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 44.213709909702054° to 44.63739123445585° latitude; -72.35595703125° to -71.5869140625° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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James B. Shanley, Bernhard Mayer, Myron J. Mitchell, Scott W. Bailey. 2008. Seasonal and event variations in δ 34 S values of stream sulfate in a Vermont forested catchment: Implications for sulfur sources and cycling. https://doi.org/10.1016/j.scitotenv.2008.03.020

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