Binary nucleation

2 Effect of a Preexisting Aerosol on H2SO4-H2O Binary Nucleation 

FIGURE 10.15 Dimensionless nucleation flux as a function of dimensionless aerosol surface area. S = 4.0 and / = 87. 

The characteristic time r/v to achieve a certain nucleation rate is calculated as follows. We assume that the production rate Rg of H2SO4 vapor is constant. At r = 0, = 0 

We see that at the lower SO2 conversion rate, the characteristic time for nucleation to occur greatly exceeds that for condensation so the latter can be expected to predominate as the mechanism for gas-to-particle conversion. At the higher production rate at high humidities, the nucleation time can actually become shorter than the condensation time, indicating that heteromolecular nucleation can be expected to become important under these conditions. 

FIGURE 10.16 Estimates for the characteristic time required for the condensation of sulfuric acid vapor on preexisting particles (r ) and the characteristic time required for nucleation of H2SO4-H2O aerosols (xs) as a function of relative humidity. Two H2SO4 production rates 

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As discussed in detail by Pandis et al. (1995), nucleation theory shows there is a critical sulfuric acid concentration above which binary nucleation of sulfuric acid and water should occur. Based on the work of Jaecker-Voirol and Mirabel (1989), they parameterize the theoretical dependence of this critical concentration needed to generate nuclei at a rate of 1 cm 3 s 1 on the relative humidity (RH, expressed in this case as a fraction, i.e., between 0 and 1) and temperature, T (in K) ... 

Nilsson, E. D., and M. Kulniala, The Potential for Atmospheric Mixing Processes to Enhance the Binary Nucleation Rate, J. Geophys. Res., 103, 1381-1389(1998). 

Wyslouzil, B. E., J. H. Seinfeld, R. C. Flagan, and K. Okuyama, Binary Nucleation in Acid-Water Systems. II. Sulfuric Acid-Water and a Comparison with Methanesulfonic Acid-Water, J. Chem. Phys., 94, 6842-6850 (1991). 

Zhang et al. (1996) suggest that this preactivation changes the crystal structure of SAT at the interface to more closely match the NAT lattice. This nucleation and growth of NAT on solid SAT was proposed as one potential mechanism for Type I PSC formation (e.g., see Tolbert, 1994), although this process now appears to be less important because of the low probability for binary nucleation of nitric acid and water on SAT (MacKenzie et al., 1995). 

Singh, J. J., and A. C. Smith, Experimental studies of the ion-induced binary nucleation, J Aerosol Sci.,... 

In the particular case of gas-to-condensed-phase transitions. Equations 8 and 14 can be developed together to yield the following accurate approximation for isothermal binary nucleation (e.g., for H2SO4/H2O) ... 

Clarke AD, Davis D, Kapustin VN, Eisele F, Chen G, Paluch I, Lenschow D, Bandy AR, Thornton D, Moore K, Mauldin L, Tanner D, Litchy M, Carroll MA, Collins J, Albercook G (1998) Particle nucleation in the tropical boundaiy layer and its coupling to marine sulfur sources. Science 282 89-92 Clarke AD, Kapustin, Eisele FL, Weber RJ, McMuny PH (1999) Particle production near marine clouds Sulfuric acid and predictions from classical binary nucleation. Geophys Res Lett 26 2425-2428 Clegg SL, Brimblecombe P, Wexler AS (1998) Thermodynamic model of the system H -NH/-Na -S04 -NO3 -CI -H2O at 298.15 K. JPhys Chem. A 102 2155-2171 Clement CF, Piijola L, dal Maso M, Ma kela JM, Kulmala M (2001) Analysis of particle formation bursts observed in Finland. J Aerosol Sci 32 217-236... 

Kusaka I, Wang ZG, Seirrfeld JH (1998a) Direct evalrration of the equilibrium distribution of physical clusters by a grand canonical Monte Carlo simrrlation. J Chem Phys 108 3416-3423 Kusaka I, Wang ZG, Seinfeld JH (1998b) Binary nucleation of sulfuric acid-water Monte Carlo simulation. J Chem Phys 108 6829-6848... 

Obeidat, A., Li., J.-S. Wilemski, G. (2004) Binary Nucleation of a Non-ideal System from Classical and Density Functional Theories. In Nucleation and Atmospheric Aerosols 2004 7(5 International Conference, Conference Proceedings (Eds. M. Kasahara, M. Kulmala) 81-84... 

FIGURE 10.14 Vapor pressure of sulfuric acid as a function of temperature using the Ayers et al. (1980) and Kulmala and Laaksonen (1990) estimates. (Reprinted with permission from Kulmala, M. and Laaksonen, A. Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2S04 saturation vapor pressure, J. Chem. Phys. 93, 696-701. Copyright 1990 American Institute of Physics.)... 

Kulmala, M., and Laaksonen, A. (1990) Binary nucleation of water sulfuric acid system. Comparison of classical theories with different H2SO4 saturation vapor pressures, J. Chem. Phys. 93,696-701. 

Another method of nucleation measurement that differs from both diffusion and expansion chambers involves the rapid turbulent mixing of two gas streams (Wyslouzil et al. 1991a,b). This method is particularly suited to studies of binary nucleation. Two carrier gas-vapor streams are led to a device where rapid turbulent mixing takes place. The two-component vapor mixture is supersaturated and begins to nucleate immediately. The stream passes to a tube where nucleation may continue and the nucleated particles grow. Residence time in the flow tube is the order of seconds. When the nucleated particle concentration is sufficiently low, droplet growth does not deplete the vapor appreciably, and constant nucleation conditions can be assumed. 

FIGURE 11.9 Clusters in binary nucleation. Proceeding vertically up the left side of the figure are clusters of pure water proceeding horizontally along the bottom of the figure are clusters of pure acid molecules. The darker circles denote water molecules the dashed lines indicate the boundary of the cluster. 

FIGURE 11.10 Free energy of duster formation, AG(nA.nB). for binary nucleation (a) schematic diagram of saddle point in the AG surface, (b) AG surface for HjSO -HjO system at 298 K. 

Sulfuric acid-water binary nucleation (Kulmala and Laaksonen 1990)... 

Wyslouzil, B. E., Seinfeld, J. H., Flagan, R. C., and Okuyama, K. (1991b) Binary nucleation in acid-water systems. II. Sulfuric acid-water and a comparison with methanesulfonic acid-water,... 

FIGURE 10.11 H2SO4-H2O binary nucleation rate (cm s ) as a function of NH2SO4. calculated from classical binary nucleation theory (Kulmala and Laaksonen, 1990). (a) Relative humidity... 

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