Atmospheric sulfur dioxide and sulfate. Distribution of concentration at urban and nonurban sites in United States

Abstract

The interpretation of results from the US national air surveillance networks indicates that large differences in sulfate concentation levels exist between eastern and western urban and nonurban sites in the United States. Sulfates contribute a larger portion of the sulfur compounds at western urban sites than at eastern urban sites. The relationship of sulfur dioxide to sulfate is nonlinear over the range of concentrations at urban sites. Statistical relationships have been computed relating urban sulfate to urban sulfur dioxide and also to the ratio of sulfur dioxide to sulfate. Background levels of water-soluble sulfate differ greatly between the eastern and western US at the eastern nonurban sites, a residue sulfate level of at least 5 microgram/m/sup 3/ exists. This large residue is attributed to long-distance transport of sulfur dioxide to sulfate during transport. Sulfate-containing aerosols are broadly distributed throughout large regions of the eastern and midwestern US.