Correlations between Stream Sulphate and Regional SO2 Emissions
Smith RA and Alexander RB. 1986. Correlations between Stream Sulphate and Regional SO2 Emissions. Nature. 322:722-724
ABSTRACT: The relationship between atmospheric SO2 emissions and stream and lake acidification has been difficult to quantify, largely because of the limitations of sulphur deposition measurements. Precipitation sulphate (SO4) records are mostly <5 yr in length1 and do not account for dry sulphur deposition2. Moreover, a variable fraction of wet- and dry-deposited sulphur is retained in soils and vegetation and does not contribute to the acidity of aquatic systems3,4. We have compared annual SO2 emissions for the eastern United States from 1967 to 1980 with stream SO4 measurements from fifteen predominantly undeveloped watersheds (Figs 1,2). We find that the two forms of sulphur are strongly correlated on a regional basis and that streams in the southeastern United States (SE) receive a smaller fraction (on average, 16%, compared with 24% of regional sulphur emissions than do streams in the northeastern United States (NE). In addition to providing direct empirical evidence of a relationship between sulphur emissions and aquatic chemistry, these results suggest that there are significant regional differences in the fraction of deposited sulphur retained in basin soils and vegetation.