Open AccessSources of stream water sulfate during the spring snowmelt in boreal streams: Evidence from δ 34 S isotope measurements
Author(s) -
Mörth CarlMagnus,
Laudon Hjalmar,
Mellqvist Elin,
Torssander Peter,
Giesler Reiner
Publication year - 2008
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jg000457
Subject(s) - snowmelt , streams , hydrology (agriculture) , spring (device) , sulfate , environmental science , boreal , biogeochemistry , soil water , geology , snow , chemistry , oceanography , soil science , geomorphology , mechanical engineering , computer network , paleontology , geotechnical engineering , organic chemistry , computer science , engineering
Episodic hydrological events, such as snowmelt during spring, have a marked effect on stream water chemistry. Here we investigated how spring snowmelt affected δ 34 S values of sulfate in six streams situated in northern Sweden. Four streams had high δ 34 S SO4 values during base flow with values ranging from +11.9 to +8.6‰. During snowmelt the δ 34 S SO4 decreased to around +6‰. In one of the streams and in the forested upper reaches of a second stream, δ 34 S 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 δ 34 S SO4 values (−5.0‰ to −0.5‰). We could identify two stream water SO 4 sources: sedimentary sulfides and anthropogenic S. Bacterial dissimilatory sulfate reduction was identified as an important process affecting stream water δ 34 S SO4 values and suggests that in this boreal landscape, peatlands and possibly riparian zones have a large influence on the biogeochemistry of SO 4 2− during base flow conditions. Our results suggest that during the spring snowmelt, snow S and desorbing SO 4 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.