Importance of groundwater sulfate to acidification in the Goose River watershed, Maine

摘要

The role of groundwater sulfate discharge to ponds and streams within the Goose River basin (33.3 km~2) is examined. While airborne sulfate deposition has declined, acidity in surface waters locally remains elevated. Monthly SO_4~(2-) 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 δ~(34) S_(SO_4) 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 δ~(18)O_(SO_4) and δ~(18)O_(H_2O) data. Cosmogenic ~(35)S_(SO_4) residence times estimate new atmospheric SO_4~(2-) deposition in the catchments and production of SO_4~(2-) from water-rock interactions among some fractured granitoids.