Sulfuric stratospheric

Pollack, Toon, Turco and collaborators have extensively studied the characteristics of aerosols in the context of climate research (Pollack et al., 1976 Toon and Pollack, 1975 Turco et al., 1980, 1982). Relevant contributions in this field have been given by Reck (1974) and by Harshvardan and Cess (1976). Studies related to the nucleation and growth of sulfur stratospheric aerosols have been performed by Friend et al. (1980), by Hamill et al. (1977), and by Steele and Hamill (1981). Problems related to transport and dynamics of the volcanic clouds have been considered by Danielsen (1968, 1974), Dyer and Hicks (1968) and Cadle et al. (1976). 

Similar heterogeneous reactions also can occur, but somewhat less efticientiy, in the lower stratosphere on global sulfate clouds (ie, aerosols of sulfuric acid), which are formed by oxidation of SO2 and COS from volcanic and biological activity, respectively (80). The effect is most pronounced in the colder regions of the stratosphere at high latitudes. Indeed, the sulfate aerosols resulting from emptions of El Chicon in 1982 and Mt. Pinatubo in 1991 have been impHcated in subsequent reduced ozone concentrations (85). 

A smaller factor in ozone depletion is the rising levels of N2O in the atmosphere from combustion and the use of nitrogen-rich fertilizers, since they ate the sources of NO in the stratosphere that can destroy ozone catalyticaHy. Another concern in the depletion of ozone layer, under study by the National Aeronautics and Space Administration (NASA), is a proposed fleet of supersonic aircraft that can inject additional nitrogen oxides, as weU as sulfur dioxide and moisture, into the stratosphere via their exhaust gases (155). Although sulfate aerosols can suppress the amount of nitrogen oxides in the stratosphere... 

Chlororocarbon (CFG) refrigerants are inherently safer with respect to fire, explosion, and acute toxic hazards when compared to alternative refrigerants such as ammonia, propane, and sulfur dioxide. However, they are believed to cause long term environmental damage because of stratospheric ozone depletion. 

Baroni M, Thiemens MH, Delmas RJ, Savarino J (2007) Mass-independent sulfur isotopic composition in stratospheric volcanic eruptions. Science 315 84-87 Barth S (1993) Boron isotope variations in nature a synthesis. Geologische Rundschau 82 640-651... 

Thiemens MH, Heidenreich JE (1983) The mass independent fractionation of oxygen - A novel isotope effect and its cosmochemical implications. Science 219 1073-1075 Thiemens MH, Jackson T, Zipf EC, Erdman PW, van Egmond C (1995) Carbon dioxide and oxygen isotope anomalies in the mesophere and stratosphere. Science 270 969-972 Thode HG, Monster J (1964) The sulfur isotope abundances in evaporites and in ancient oceans. In Vinogradov AP (ed) Proc Geochem Conf Commemorating the Centenary of V I Vernadsku s Birth, vol 2, 630 p... 

There are many different types of surfaces available for reactions in the atmosphere. In the stratosphere, these include ice crystals, some containing nitric acid, liquid sulfuric acid-water mixtures, and ternary solutions of nitric and sulfuric acids and water. In the troposphere, liquid particles containing sulfate, nitrate, organics, trace metals, and carbon are common. Sea... 

Zhang, R., J. T. Jayne, and M. J. Molina, Heterogeneous Interactions of C10N02 and HC1 with Sulfuric Acid Tetrahydrate Implications for the Stratosphere, J. Phys. Chem., 98, 867-874... 

Iraci, L. T and M. A. Tolbert, Heterogeneous Interaction of Formaldehyde with Cold Sulfuric Acid Implications for the Upper Troposphere and Lower Stratosphere, . /. Geophys. Res., 102, 16099-16107 (1997). 

Zhang, R., M.-T. Leu, and L. F. Keyser, Heterogeneous Chemistry of HONO on Liquid Sulfuric Acid A New Mechanism of Chlorine Activation on Stratospheric Sulfate Aerosols, . /. Phys. Chem., 100, 339-345 (1996). 

The concentration of sulfuric acid in SSA is typically 50-80 wt% under mid- and low-latitude stratosphere conditions. However, as the temperature drops, these particles take up increasing amounts of water, which dilutes the particles to as low as 30 wt% H2S04. Gaseous nitric acid is also absorbed by these solutions, forming ternary H2S04-H20-HN03 solutions with as much as 30 wt% in each acid. 

Another method of probing sulfuric acid aerosols is to heat the sample intake sufficiently to vaporize sulfuric acid-water aerosols but not other particles such as those containing ash minerals the difference between the measured particles with and without intake heating provides a measure of the contribution of sulfuric acid-water. Using this technique, Deshler et al. (1992), for example, have shown that more than 90% of the stratospheric particles above Laramie, Wyoming, after the Mount Pinatubo eruption were composed of sulfuric acid-water mixtures. 

Most of the research to date has focused on aerosols and PSCs containing inorganic species such as nitric and sulfuric acids. While CH4 is the only hydrocarbon that is sufficiently unreactive in the troposphere to reach the stratosphere, it is oxidized to compounds such as HCHO that can be taken up into sulfuric acid particles (Tolbert et al., 1993). The effects of such uptake and subsequent chemistry are not well established. 

Additional sulfates continue to form after the eruption as gaseous S02 is oxidized to sulfuric acid and sulfates. While we shall focus here on the effects of these sulfate particles on the heterogeneous chemistry of the stratosphere, there may be other important effects on the homogeneous chemistry as well. For example, model calculations by Bekki (1995) indicate that this oxidation of S02 by OH leads to reduced OH levels, which alters its associated chemistry. 

Measurements of the solubility of HBr in sulfuric acid at 220 K gave Henry s law constants from 8.5 X 103 M atm-1 for 72 wt% H2S04 to 1.5 X 107 M atm-1 for 54 wt% H2S04 (Williams et al., 1995 Abbatt, 1995). Application of these values to stratospheric aerosol particles typical of midlatitude conditions gives very small equilibrium concentrations of dissolved HBr i.e., most of the HBr will remain in the gas phase. 

Abbatt, J. P. D., Interactions of HBr, HCI, and HOBr with Supercooled Sulfuric Acid Solutions of Stratospheric Composition, J. Geophys. Res., 100, 14009-14017 (1995). 

Borrmann, S S. Solomon, J. E. Dye, D. Baumgardner, K. K. Kelly, and K. R. Chan, Heterogeneous Reactions on Stratospheric Background Aerosols, Volcanic Sulfuric Acid Droplets, and Type I Polar Stratospheric Clouds Effects of Temperature Fluctuations and Differences in Particle Phase, J. Geophys. Res., 102, 3639-3648 (1997b). 

Burley, J. D., and H. S. Johnston, Nitrosyl Sulfuric Acid and Stratospheric Aerosols, Geophys. Res. Lett., 19, 1363-1366 (1992a). 

M. Loewenstein, G. V. Ferry, K. R. Chan, and B. L. Gary, Particle Size Distributions in Arctic Polar Stratospheric Clouds, Growth, and Freezing of Sulfuric Acid Droplets, and Implications for Cloud Formation, J. Geophys. Res., 97, 8015-8034 (1992). 

Hanson, D. R., and A. R. Ravishankara, Heterogeneous Chemistry of Bromine Species in Sulfuric Acid under Stratospheric Conditions, Geophys. Res. Lett., 22, 385-388 (1995). 

Hofmann, D. J., Increase in the Stratospheric Background Sulfuric Acid Aerosol Mass in the Past 10 Years, Science, 248, 996-1000 (1990). 

Imre, D. G J. Xu, and A. C. Tridico, Phase Transformations in Sulfuric Acid Aerosols Implications for Stratospheric Ozone Depletion, Geophys. Res. Lett., 24, 69-72 (1997). 

Tolbert, M. A., M. J. Rossi, and D. M. Golden, Heterogeneous Interactions of Chlorine Nitrate, Hydrogen Chloride, and Nitric Acid with Sulfuric Acid Surfaces at Stratospheric Temperatures, Geophys. Res. Lett., 15, 847-850 (1988a). 

---