Aerosol growth

This paper summarizes part of the results of an investigation designed to characterize the aerodynamic size distributions of natural radioactivity and to evaluate the results in the context of sulfate distributions and recent advances in the understanding of aerosol growth mechanisms. This paper, while emphasizing our results on Pb-212 and Pb-214, also summarizes our initial data for longer-lived radionuclides. 

Pb-210 and the Cosmogenic Radionuclides. We noted earlier that our measurements of Pb-214 were really measurements of Po-214 decay, that is, the production of Pb-210. The mean AMAD of these measurements was about 0.16 um, with the AMAD of Pb-210 predicted to be 0.18 um after recoil. However, the summer AMAD of Pb-210, after aging in the atmosphere for about a week (Moore et al., 1980), was closer to 0.4 um, indicating that Pb-210 s AMAD approximately doubles during its lifetime in the atmosphere. The limited measurements reported here suggest that the AMAD of Pb-210 is smaller in winter than summer, possibly reflecting differences in aerosol growth rates. The summer measurements were also not different from simultaneous SoJ measurements. 

FIGURE 3 17 Increase in aerosol light-scattering efficiency as a result of aerosol growth. Compare with Figures 3-24 and 3-26. Reprinted with permission from O Brien et al. 

McMurty, P.H. and Grosjean, D. Photochemical formation of organic aerosols growth laws and mechanisms, Atmos. Environ., 19(9) 1445-1451, 1985. 

The basic theoretical equation ( ) relating source contributions and chemical composition is a mass balance which requires no consideration of rate processes. In this paper, the theory is extended to the resolution of the visibility degrading components of the aerosol and to chemically reactive families of chemical compounds. These extensions require new theoretical analyses which take into account the dynamics of aerosol growth and chemical kinetics, respectively. The extension to these rate processes are the subject of this paper. 

Thus the use of a linear theory with constant coefficients to relate the extinction coefficient to source mass contributions can be justified for certain aerosol growth mechanisms. 

Smog chamber studies have documented similar aerosol growth mechanisms. For example, in the photochemical oxidation of dimethyl sulfide, the formation and growth of particles in an initially particle-free system was observed. However, if seed particles with 34-nm mean size were present, an oscillation in the... 

Another example of reactions at interfaces that is only now being recognized, due to the lack of suitable experimental techniques in the past, is that of species such as SOz and NOz at liquid interfaces. As discussed in Chapters 7 and 8, there is increasing evidence that the reactions of such species at the air-water interface can be fast relative to that in the bulk and may have unique reaction mechanisms compared to those in the bulk or gas phases. Given the paucity of data on such processes at the present time, they are generally not included in present models of aerosol growth. How-... 

Relative Importance of Various Aerosol Growth Mechanisms... 

Different mechanisms of aerosol growth give rise to different so-called growth laws, which are expressions relating the change in particle size (e.g., volume or diameter) with time to the particle diameter. Because different mechanisms of particle formation give rise to different growth laws, one can test experimental data to see which mechanism or combination of mechanisms is consistent with the observations. For a more detailed discussion of this approach, see Friedlander (1977), Heisler and Friedlander (1977), McMurry and Wilson (1982), Pandis et al. (1995), and Kerminen and Wexler (1995). 

Heisler, S. L., and S. K. Friedlander, Gas-to-Particle Conversion in Photochemical Smog Aerosol Growth Laws and Mechanisms for Organics, Atmos. Environ., 11, 157-168 (1977). 

Tang, I. N., H. R. Munkelwitz, and J. G. Davis, Aerosol Growth Studies. IV. Phase Transformation of Mixed Salt Aerosols in a Moist Atmosphere, . /. Aerosol Sci., 9, 505-511 (1978). 

Carslaw, K. S., B. P. Luo, S. L. Clegg, Th. Peter, P. Brimblecombe, and P. J. Crutzen, Stratospheric Aerosol Growth and HN03 Gas Phase Depletion from Coupled HNO, and Water Uptake by Liquid Particles, Geophys. Res. Lett., 21, 2479-2482 (1994). 

Carlslaw, K.S., Luo, B.P., Clegg, S.L., Peter, T., Brimblecombe, P, and Crutzen, P.J. (1994) Stratospheric aerosol growth and HNO, gas phase depletion from coupled HNO, and water uptake by liquid particles, Geophys. Res. Lett. 21,2479-2482. 

Maria S.F. Russel L.M. Gilles M.K. and Myneni S.C.B. (2004). Organic aerosol growth mechanisms and their climate-forcing implications. Science, 306(5703), 1921-1924. 

A comparison between the rates of formation and dissociation of doublets as well as the calculation of the critical particle size are presented in the next section. The subsequent section discusses the implications of the above two mechanisms of aerosol growth on the calculation of the Brownian coagulation coefficient from the evolution of particle number concentration. 

This book contains a number of papers published by Ruckenstein and coworkers on the topic of nanodispersions. Aerosols are the focus of the first chapter which features a model for the sticking probability as the main contribution. One concludes that, when the particles are small enough, the dissociation rate can become sufficiently large for doublets to reach equilibrium with single particles. However, above a critical radius for the particles, the doublets become stable and their concentration increases with time, providing nuclei for aerosol growth. 

Tang I. N. and Munkelwitz H. R. (1977) Aerosol growth studies III. Ammonium bisulfate aerosols in a moist atmosphere. J. Aerosol Sci. 8, 321-330. 

Aerosol growth laws are expressions for the rate of change in particle size as a function of particle size and the appropriate chemical and physical properties of the system. Such expressions are necessary for the calculation of changes in the size distribution function with time as shown in thi.s and the next chapter. In this section, transport-limited growth laws based on the previous section are discussed first followed by growth laws determined by aerosol phase chemical reactions. 

This form is quite different from the diffusional growth expression (13.7) in its dependence on particle size in this case, larger particles grow faster than smaller ones. McMurry et ai. (1981) analyzed data for several power plant plumes (Fig. 13.6a). They found that both diffusion to the particles and droplet phase reaction contributed to plume aerosol growth (Fig. 13.6b). However, the droplet-phase reactions accounted for less than 20% of total aerosol volume growth. 

Upadhyay, R. R. Ezekoye, O. A. 2003 Evaluation of the 1-point quadrature approximation in QMOM for combined aerosol growth laws. Journal of Aerosol Science 34, 1665-1683. 

Czoschke N.M., M. Jang and R.M. Kamens Effect of acidic seed on biogenic secondary organic aerosol growth, Atmos. Environ. 31 (2003) 4287-4299. 

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