Sulfuric atmospheric aerosol

Atmospheric particulates (sea salt, carbonaceous soot, and sulfuric acid aerosols) are known to provide a condensed phase for conq>lex heterogeneous chemistry to occur. Although the presence of atmospheric particulates are known to alter trace gas concentrations, details of the specific chemical mechanisms for condensed phase chemistry have not been identified. 

Macias, E.S. Radcliff, C.D. Lewis, C.W. Sawaki, C.R., Proton-Induced y-ray Analysis of Atmospheric Aerosols for Carbon, Nitrogen, and Sulfur Composition, Anal. Chem., 1978, 5, 1120. 

Barbaray, B., J.-P. Contour, and G. Mouvier, Sulfur Dioxide Oxidation over Atmospheric Aerosol-X-Ray Photoelectron Spectra of Sulfur Dioxide Adsorbed on V205 and Carbon, Atmos. Environ., 11, 351-356(1977). 

The dense clouds in the atmosphere of Venus, which obscure the surface of the planet totally from our view, are evidently composed of a sulfuric acid aerosol. Why are such clouds possible on Venus but not on Earth (See Section 8.1.)... 

On-line measurements of the sulfur content of atmospheric aerosols have been made by removing gaseous sulfur species from the aerosol and then analyzing the particles for sulfur with a flame photometric detector (24) or by using an electrostatic precipitator to chop the aerosol particles from the gas so that the sulfur content could be measured by the difference in flame photometric detector response with and without particles present. These and similar methods could be extended to the analysis of size-classified samples to provide on-line size-resolved aerosol composition data, although the analytical methods would have to be extremely sensitive to achieve the size resolution possible in size distribution analysis. 

Continuous Sampling and Determination. There are no truly continuous techniques for the direct determination of sulfuric acid or other strong acid species in atmospheric aerosols. The closest candidate method is a further modification of the sensitivity-enhanced, flame photometric detector, in which two detectors are used, one with a room-temperature de-nuder and one with a denuder tube heated to about 120 °C. Sulfuric acid is potentially determined as the difference between the two channels. In fact, a device based on this approach did not perform well in ambient air sampling (Tanner and Springston, unpublished data, 1990). Even with the SF6-doped H.2 fuel gas for enhanced sensitivity, the limit of detection is unsuitably high (5 xg/m3 or greater) because of the difficulty in calibrating the two separate FPD channels with aerosol sulfates. 

Sulfuric acid may be determined in the presence of other acidic aerosol constituents, but no method for the separation and determination of bisulfate, the most common acidic species in atmospheric aerosols, has been successfully developed. 

Onsager inverted snowball theory (Com.) relation to Smoluchowski equation in, 35 relaxation time by, 34 rotational diffusion and, 36 Ozone in the atmosphere, 108 alkene reactions with, 108 Crigee intermediate from, 108 molozonide from, 108 ethylene reaction with, 109 acetaldehyde effect on, 113 formic anhydride from, 110 sulfur dioxide effect on, 113 sulfuric acid aerosols from, 114 infrared detection of, 108 tetramethylethylene (TME) reaction with, 117... 

Figure 1 shows a schematic of a typical atmospheric aerosol particle (if such an entity can be assumed to exist). The particle consists of sulfates, nitrates, water, ammonium, elemental and organic carbon, metals, and dust. After a primary particle is emitted, gas-phase reactions occur, converting oxides of nitrogen to nitric acid, sulfur dioxide to sulfuric acid, and hydrocarbons to oxidized, low-vapor-pressure condensable organics. 

Leung, Colussi and Hoffmann have used isotopic analysis in an attempt to constrain the amount of sulfate that could be produced by Crutzen s mechanism [129,130]. The first study retrieved the concentration profiles of OC S and OC S from infrared transmission spectra of the atmosphere recorded by the NASA MkIV balloon-borne interferometer. They derived an enrichment factor of 73.8 zb 8.67oo defined such that photolytically generated sulfur would be enriched in An isotopic budget based on this result shows that OCS photolysis cannot be a significant source of sulfate aerosol, since the enrichments of OCS, sulfuric acid aerosol and SO2 are known to be small [131]. A later laboratory study by the same group came to the conclusion that stratospheric photolysis results in an enrichment of 67 zb 77oo. 

Understanding the processes that control atmospheric aerosol concentrations and representing these processes in chemical transport models rests in large part on the accuracy of emissions inventories of aerosols and gaseous precursors. The most widely applied approach to developing such inventories is characterization of emissions per unit of activity (called emission factors ) combined with characterization of the intensity and geographic distribution of these activities. This approach is well developed for some gas-phase species. Emission of SO2 from fossil fuel combustion provides an example. Most sulfur in... 

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