STABLE SULFUR ISOTOPES OF SULFATE IN PRECIPITATION AND STREAM SOLUTIONS IN A NORTHERN HARDWOOD WATERSHED

Stable S isotopes of SO42- in precipitation, throughfall, and stream water solutions in a northern hardwood watershed (Bear Brook Watershed, Maine) were examined to determine sources of stream SO42- and to identify watershed processes that may affect atmospherically deposited SO42- prior to reaching the streams. Similarity among temporal patterns in delta-S-34 of precipitation, throughfall, stream SO42- (range: +3.4 to +9.4%), and [SO42- marine]/(SO42- total] of stream SO42-(5-10%) indicate that the delta-S-34 values of stream SO42- are controlled principally by atmospheric deposition. Lack of correlation between delta-S-34 of stream SO42- and stream [SO42- total], elevational position, and stream discharge supports the interpretation that fractionation of stable S isotopes within the watershed appears to have, at most, a minor influence on delta-S-34 of stream SO42-.