Climate effects on sulphate flux from forested catchments in south-central Ontario

摘要: Net export of sulphate from watersheds may delay the response surfacewaters to changes in acid deposition. Long-term (18-yr) sulphatebudgets were calculated for 8 headwater streams located acid-sensitiveregion Muskoka-Haliburton, south central Ontario. Sulphate deposition inthisregion has decreased by almost 40% over last 2 decades, and exportfrom catchments also generally declined time, but most arestill a net source drainage streams. sulphateoccurred majority years record, wasparticularly large following dry, warmer than average summers, when stream flowceased up several weeks at time. In with warm dry suchas occurred 1983/84 between 1987/88 1990/91, inclusive, streamexportfrom was 1.5 times greater input viabulkdeposition. Annual concentrations stronglycorrelated dryness, which weredry longer periods Temporal patterns annual sulphateconcentrations highly coherent among streams, netsulphate both wetland-draining predominantly uplandstreams. Climate variables, specifically temperature precipitation act on aregional scale are likely responsible similar temporal ofsulphate retention these physiographically different catchments. Netsulphate recovery impacted surfacewaters, despite reductions industrial SO2 emissions.