“…In contrast, stations in the northeastern quarter of the Nation have tended to show either no trend or declines in sulfate con- centrations. These changes in sulfate levels tend to coincide with the historical pattern of trends in atmospheric sulfur dioxide emissions in the United States from 1965 through 1980 and lend support to the hypothesis that stream sulfate concentrations in surface water tend to follow regional trends in deposition rates of acidic precipitation (Smith and Alexander, 1983). When acidic precipitation falls on the land surface in areas of alkaline terrane, the acidity generally is neutralized by reaction with alkaline constituents of the soil, rock, and vegetation; thus, in areas of alkaline terrane, the acidity of the precipitation has little effect on surface or ground water.…”