Evidence for decrease in atmospheric sulfur burden in the eastern United States caused by reduction in SO 2 emissions

We report aerosol SO 4 2− measurements from 1979 to 1996 at Whiteface Mountain located in the Adirondack Mountains and from 1983 at Mayville, in western New York State. From 1981 to 1991 SO 4 2− decreased, ∼3% per year. Reductions of nearly 47% in SO 4 2− and total sulfur concentrations at Whiteface Mountain, and about 30% at Mayville, were observed during 1995 to 96 compared with the mean levels during 1981–91, while the upwind SO 2 emissions in the Midwestern United States decreased by 36%. Linear relationships between SO 4 2− and total sulfur concentrations and the SO 2 emissions were observed for the entire period. The mean ratio of SO 4 2− concentrations to SO 2 emissions for the eighteen year period at Whiteface Mountain is 0.11 ± 0.014 and for thirteen years at Mayville is 0.23± 0.014 µg SO 4 2− /m³ per 10³ metric tons SO 2 emitted per day. The data suggest that the observed relationship could be used to predict decreases in atmospheric SO 4 2− levels based on SO 2 emissions several years hence. Furthermore, it appears feasible to develop an empirical source‐receptor relationship if similar data were acquired from a network of strategically located sampling sites.