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USGS · 1015038

Isotopic study of sulfate sources and residence times in a subalpine watershed

C.L. Kester·Jill Baron·J.T. Turk
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Abstract

Stable sulfur and oxygen isotope ratios and naturally occurring 35 S SO4 activities were used to examine sulfate sources, address the role of sulfur dynamics, and estimate residence times of atmospherically derived sulfate in Loch Vale Watershed, Colorado. In 1996, surface water samples from small streams flowing through talus, forest, and wetland areas had δ 34 S SO4 values ranging from 1.8 to 3.7‰. Values of δ 18 O SO4 at the three sites ranged from –1.3 to 3.7‰. Average δ 34 S SO4 and δ 18 O SO4 values in Loch Vale precipitation (1991–1999) are higher (5.2 and 13.6, respectively) than surface water values, indicating that some of the deposited sulfate is transformed and/or mixed with other sulfur sources in the watershed (e.g. mineral and organic sulfur). Sulfate ages determined by 35 S SO4 activities support this and show that deposited sulfate may be stored on a timescale of 1 year or more prior to being released to surface waters.

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C.L. Kester, Jill Baron, J.T. Turk. 2003. Isotopic study of sulfate sources and residence times in a subalpine watershed. https://doi.org/10.1007/s00254-002-0684-y

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