The role of groundwater sulfate discharge to ponds and streams within the Goose River basin (33.3 km2) is examined. While airborne sulfate deposition has declined, acidity in surface waters locally remains elevated. Monthly SO42- analyses (1999--2002) of wet deposition and surface waters are reported, and a sulfate budget for six catchments of the Goose River watershed, Maine is calculated. Groundwater δ34SSO4 values from different bedrock types are beneficial in identifying groundwater source(s) of sulfate in surface waters and discriminating them from atmospheric sulfate deposition. The variability of proposed sulfide oxidation among certain local chalcophile rocks and the depth of aeration in these sheared granitoids are elucidated from δ18OSO4 and δ18OH2O data. Cosmogenic 35SSO4 residence times estimate new atmospheric SO42- deposition in the catchments and production of SO42- from water-rock interactions among some fractured granitoids.