Sources of stream sulphate in headwater catchments in Otter Creek Wilderness, West Virginia, USA

Upland forested catchments in the Appalachian Plateau region receive among the greatest rates of atmospheric sulphur (S) deposition in the eastern USA , although coal mines and S-bearing minerals in bedrock may also contribute to stream acidity in this region. Watershed mass balance and stable S isot opic values (delta S-34) of sulphate (SO42-) were used to assess the contri butions to stream SO42- from atmospheric and lithogenic sources at Yellow C reek (YC), a headwater catchment on the Appalachian Plateau in West Virgini a. Oxygen isotopic values (delta O-18) Of water were used to study catchmen t hydrology. Stream output of SO42- was c. 60% of atmospheric S deposition during a relatively dry year, whereas atmospheric S input was nearly balanc ed by stream output during a year with above normal amounts of precipitatio n. The temporal patterns and values of delta S-34 were similar between bulk precipitation and stream water at two upper elevation sites. At the lowest elevation site, stream delta S-34 values were similar to bull; precipitati on values during the dormant season but were slightly lower than precipitat ion during the low-flow summer, probably as the result of a greater proport ion of stream water being derived from deep hydrological flowpaths that hav e contacted S-bearing minerals with low delta S-34 values in coal seams. St ream delta S-34 values at YC were significantly higher than at Coal Run, a catchment containing abandoned coal prospects and having a greater amount o f S-bearing minerals than YC. Results suggested that lithogenic S is a rela tively minor source acid that atmospheric deposition is the principal sourc e of stream SO42-, and thus stream acidity, at YC. Copyright (C) 2001 John Wiley gr Sons, Ltd.