GEOLOGIC SOURCES OF SULPHUR AT DARGALL LANE (GALLOWAY SCOTLAND)

摘要

Dargall Lane is an acidic stream draining a moorland catchment in the Galloway Hills of southwest Scotland. This area has been receiving high atmospheric loadings of sulphur. The Dargall Lane catchment is underlain by a greywacke-shale sequence and by intrusive rocks of granodioritic- tonalitic composition. The shales have a sulphur concentration in the range 0.04--0. l9 wt./100, whereas mudstones, greywackes and grandiorites rarely exceed 0.02 wt./100 S. Calculations based on bedrock chemical composition, typical denudation rates of sedimentary and intrusive rocks, and the composition of surface water during baseflow, indicate that geogenic sulphur may account for a significant fraction of the sulphate hydrochemical budget. Sulphur mo- bilised by rock weatbering of black shales is likely to be an important contributing lhctor causing the observed lack of a significant sulphate decrease in sulfite water despite the reported 30/100 reduction of sulphate in atmospheric precipitation during the past decade.