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 isotopic values (delta S-34) of sulphate (SO42-) were used to assess the contributions to stream SO42- from atmospheric and lithogenic sources at Yellow Creek (YC), a headwater catchment on the Appalachian Plateau in West Virginia. Oxygen isotopic values (delta O-18) Of water were used to study catchment hydrology. Stream output of SO42- was c. 60% of atmospheric S deposition during a relatively dry year, whereas atmospheric S input was nearly balanced by stream output during a year with above normal amounts of precipitation. 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; precipitation values during the dormant season but were slightly lower than precipitation during the low-flow summer, probably as the result of a greater proportion of stream water being derived from deep hydrological flowpaths that have contacted S-bearing minerals with low delta S-34 values in coal seams. Stream delta S-34 values at YC were significantly higher than at Coal Run, a catchment containing abandoned coal prospects and having a greater amount of S-bearing minerals than YC. Results suggested that lithogenic S is a relatively minor source acid that atmospheric deposition is the principal source of stream SO42-, and thus stream acidity, at YC. Copyright (C) 2001 John Wiley gr Sons, Ltd.