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Research article, 2008

Sources of stream water sulfate during the spring snowmelt in boreal streams: Evidence from delta S-34 isotope measurements

Moerth CM, Laudon H, Mellqvist E, Torssander P, Giesler R


Episodic hydrological events, such as snowmelt during spring, have a marked effect on stream water chemistry. Here we investigated how spring snowmelt affected delta S-34 values of sulfate in six streams situated in northern Sweden. Four streams had high delta S-34(SO4) values during base flow with values ranging from +11.9 to +8.6%. During snowmelt the delta S-34(SO4) decreased to around +6%. In one of the streams and in the forested upper reaches of a second stream, delta S-34(SO4) values were close to +5% during base flow and decreased to about +3.8% during the spring snowmelt. One stream, which drained cultivated postglacial sediments dominated by acid sulfuric soils, was differentiated from the other streams by low delta S-34(SO4) values (-5.0% to -0.5%). We could identify two stream water SO4 sources: sedimentary sulfides and anthropogenic S. Bacterial dissimilatory sulfate reduction was identified as an important process affecting stream water delta S-34(SO4) values and suggests that in this boreal landscape, peatlands and possibly riparian zones have a large influence on the biogeochemistry of SO42- during base flow conditions. Our results suggest that during the spring snowmelt, snow S and desorbing SO4 of mainly anthropogenic origin are the two major S sources in four of the investigated streams. Two streams in forested areas also indicate that reoxidation of reduced S may be released during the spring flood. The stream in the cultivated area was found to be strongly influenced by the acid sulfuric soils independent of stream flow conditions

Published in

Journal of Geophysical Research
2008, Volume: 113, number: G1, article number: G01005

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    Environmental Sciences related to Agriculture and Land-use

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