Sulfuric acid particles

Lovejoy, E. R., and D. R. Hanson, Measurement of the Kinetics of Reactive Uptake by Submicron Sulfuric Acid Particles, J. Phys. Chem., 99, 2080-2087 (1995). 

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. 

These sulfuric acid particles become less concentrated as the temperature decreases or the water vapour increases. Under very cold stratospheric conditions, these liquid aerosols may take up water and HNO, forming ternary solutions H,S0/HN0,/H,0, which eventually freeze [19,24,26], Below 192 K, HNO, becomes the dominant condensed acid, and H,S04 drops to below 3 wt %. The thermodynamics and freezing nucleation of ice and H,S04 or HNO, hydrates from such solutions are however not well understood [27,28]. Other types of solid particles, such as the less stable nitric acid dihydrate (NAD, HN0,.2H,0) [29], sulfriric acid tetrahydrate (SAT, H S04.4H,0) [18,30], sulphuric acid hemihexahydrate (SAH, H2S04.6.5H20) [18], nitric acid penta-hydrate (NAP, HN03.5H,0) [31] and more complex sulfuric acid/nitric acid mixed hydrates [32] may also be a key to understanding Type IPSC nucleation and evolution [28],... 

Lovejoy, E.R., and Hanson, D.R. (1995) Measurement of the kinetics of reactive uptake by subrmcron sulfuric acid particles, J. Phys. Chem 99,2080-2087. 

Because the mass of ammonium sulfate and sulfuric acid particles is mainly in the size range of active condensation nuclei, it is believed that this process provides a very effective removal mechanism for the tropospheric background aerosol. However, we have to emphasize that other processes are also operating in the cloud to remove small aerosol particles, of which the most important process is the coagulation of particles and cloud drops. As we have seen (Subsection 4.1.1), thermal coagulation is particularly effective in the range of very small particles inactive in condensation. To estimate this process, let us consider a cloud in which the number concentration of drops with radius rc is Nc. If the number concentration... 

Middleton, P., and Kiang, C. S. (1978) A kinetic aerosol model for the formation and growth of secondary sulfuric acid particles, J. Aerosol ScL, 9, 359-385. 

In the Antarctic spring, PSCs evaporate and set free active halogens (CI2 + Cl + CIO + CI2O2 Fig. 5.21). Most NO is stored as HNO3 in solid PSCs and contributes only little to O3 depletion. After ending the ozone hole period (at the end of November), PSCs almost evaporate and remain only as liquid sulfuric acid particles. Meanwhile, the normal gas phase cycles of ozone depletion control the steady-state concentration. 

Hanson, D.R., Lovejoy, E.R. The uptake of N2O5 onto small sulfuric acid particle. Geophys. Res. Lett. 21, 2401-2404 (1994)... 

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