Sulfate aerosol study. Final report

For many years, the interest in measuring ambient concentrations of sulfuric acid and ammonia has been largely derived from the need to determine the impact of specific pollution sources, or the desire to obtain information about the atmospheric processes which dominate the formation of ambient sulfates and nitrates. More recently, the need to determine the impact of the sulfuric acid emissions from catalyst equipped vehicles has increased the interest in being able to make these measurements. The work in this report was motivated by the latter problem, and is finding immediate application. Two analytical methods for determining the amount of sulfuric acid aerosol on Teflon filters have been improved, and the accuracy, precision and specificity of the methods determined. In the low temperature volatilization method, sulfuric acid is determined by selective volatilization into a flame photometric detector. The method gives an excellent separation between sulfuric acid and ammonium bisulfate or ammonium sulfate, and can be used to determine between 0.1 micrograms and roughly 1.5 micrograms sulfuric acid per filter. The 1.5 micrograms upper limit arises from apparatus limitations which can be removed. The benzaldehyde extraction method has been improved by the development of an ion chromatographic method for determining themore » sulfate extracted. The method gives excellent separation between sulfuric acid and ammonium sulfate, but about one-quarter of the ammonium bisulfate aerosol is extracted in reagent grade benzaldehyde. Amounts of sulfuric acid larger than about 5 micrograms per filter can be determined.« less