Aerosols interactions

Figure 19.2 Schematic depiction of the described approaches for deposition and subsequent cell-aerosol interaction measurement. Figure 19.2a based on Ref. [84], Figure 19.2b on Ref. [86], and Figure 19.2c on Refs. [54, 89, 90], respectively. Doted lines represent airflow.

Caltech unified GCM (Global) GISS GCM IF Harvard tropospheric Os-NO -hydrocarbon chemistry (305-346 reactions, 110-225 species) bulk aqueous-phase chemistry of S(IV) (5 equilibria and 3 kinetic reactions) prognostic aerosol/ cloud treatments with prescribed size distribution Global chemistry-aerosol interactions aerosol direct radiative forcing the role of heterogeneous chemistry impact of future climate change on O3 and aerosols Liao et al. (2003), Liao and Seinfeld (2005)... 

MOSAIC The model for simulating aerosol interactions and chemistry... 

Liao H, Seinfeld JH (2005) Global impacts of gas-phase chemistry-aerosol interactions on direct radiative forcing by anthropogenic aerosols and ozone. J Geophys Res 110(D1) 8208. doi 10.1029/2005JD005907... 

Zaveri RA, Easter RC, Fast JD, Peters LK (2008) Model for Simulating Aerosol Interactions and Chemistry (MOSAIC). J Geophys Res 113 D13204. doi 10.1029/2007JD008782 Zhang Y (2008) Online coupled meteorology and chemistry models history, current status, and outlook. Atmos Chem Phys 8 2895-2932... 

At the moment the cloud microphysics-aerosol interaction is included in HIRLAM in a very simple way in the convection schemes, where the cloud condensation nuclei have a lower concentration than over land. Enviro-HIRLAM includes the aerosol dynamics and their indirect effects on meteorology. The use of aerosol may also be prepared by making a 3D field of aerosol that has the characteristics of the currently prescribed values, then the extension to a real 3D distribution of aerosols that can interact with the microphysics is relatively straightforward. Sensitivity studies are needed to understand the relative importance of feedbacks. First experience of Enviro-HIRLAM indicates some sensitivity to effective droplet size modification in radiation and clouds. 

Marlow WH. Survey of aerosol interactive forces. In Aerosol Microphysics I Particle Interaction Marlow WH, ed. McGraw-Hill New York, 1980 116-156. 

Theoretical solution of the Navier-Stokes equation for prediction of the collision efficiency, E(Dp,dp), for the general raindrop-aerosol interaction case is a difficult undertaking. Complications arise because the aerosol size varies over orders of magnitude, and also because the large raindrop size results in complicated flow patterns (drop oscillations, wake creation, eddy shedding, etc.) Pruppacher and Klett (1997) present a critical overview of the theoretical attempts for the solution of the problem. A detailed discussion of these efforts is outside our scope. However, it is important to understand at least qualitatively the various processes involved. 

Carmichael, G. R., D. G. Streets, G. Calori, M. Amman, M. Z. Jacobson, J. Hansen and H. Ueda (2002) Changing trends in sulfur emissions in Asia Implications for acid deposition, air pollution, and climate. Environmental Sciences and Technology 356, 4707-4713 Carroll, J. J. and A. E. Mather (1992) The system carbon dioxide-water and the Krichevsky-Kasarnovsky equation. Journal of Solution Chemistry 21, 607-621 Carlton, A. G., C. Wiedinnyer and J. H. Kroll (2009) A review of secondary organic aerosol (SOA) formation from isoprene. Atmospheric Chemistry and Physics 9, 4987-5005 Carslaw, K. S., O. Boucher, D. V Spracklen, G. W. Mann, J. G. L. Rae, S. Woodward and M. Kulmala (2010) A review of natural aerosol interactions and feedbacks within the Earth system. Atmospheric Chemistry and Physics 10, 1701-1737... 

In materials science, both the preparation of composite materials and the conditions of use, e.g., catalysts, require access to methods of value for aerosol microphysics. In the former case, aerosol interaction forces play a role not only in understanding the agglomeration properties of the components of the composite, but also in describing the potential for spreading of the interstitial material... 

Scope of the Variables Determining Aerosol Interaction Forces... 

From the foregoing discussion it can be seen that the forces acting upon aerosol particles divide into two categories gas dynamics and chemical physics. In all cases, the former moderates the later to determine the spacial extent of its importance. This chapter will be devoted principally to the chemical physics of aerosol interaction forces (see Chap.2 for discussion of the gas dynamic aspects). 

Classification of the Chemical Physical Dependence The Thermodynamics of Aerosol Interactions... 

This survey consists of three parts in which an attempt is made to describe the unique aspects of interaction forces experienced by particles of Kn > 1. As such, no unified theory presently exists so results of a detailed model calculation are presented in the next section for the development of an intuitive picture of how kinetic theory exerts its influence on aerosol interactions. 

The classic treatment of aerosol interaction and coagulation is given by FUCHS [5.1] who calculated the coagulation coefficient as... 

In the transition and free-molecular regimes, the difficulty in describing effective aerosol interaction forces lies ultimately in the intractability of the Boltzmann (or other appropriate) kinetic equation to exact solution. In the case of two transition-regime spheres, with absolutely no interaction potential, an effective attractive force arises because the zone of isotropic gas molecular collisions for each particle is truncated by the presence of the other particle. It is this effective interaction force which the dividing-sphere method approximates by assuming complete absorption for distances less than some distance defined for each pair of spheres regardless of their composition. 

The aerosol interaction forces discussed in the preceding sections of this chapter have involved only electrically charged particles or neutral particles with multipole moments. The importance of charge on all phases of aerosol dynamics is generally recognized and is exploited in numerous ways. It was argued above (Sect. 

This survey has attempted to present the subject of aerosol interaction forces in its full physical context. It was, therefore, necessary from the outset to identify and delineate the numerous components of the aerosol which contribute in an essential way to microphysical aerosol interaction forces. These components include gas composition and density and particle structure and composition, that is, gas dynamics and chemical physics. Though the former is the subject of Chap.2 of this volume, the state of current practice in that area as regards kinetic theoretical definition of the importance of the chemical physics in aerosol interactions was critically assessed here to establish the necessity of the subsequent discussion. 

A model calculation was discussed which attempted to include aspects of both finite Knudsen number transport and realistically complicated interaction potentials. The conclusion was that the oomhined effects of gas and particle properties are essential for the description of aerosol interactions. 

The most commonly overlooked aerosol interaction force is that between neutral particles having no permanent multipole moments, the van der Waals force. The conclusions of the earlier discussions of aerosol kinetic theory, both from the views of current practice and the model calculation, indicated the importance of the... 

In any case, deposition of volatile fission products onto the surfaces of other aerosols will influence significantly their transport behavior and, consequently, their source term to the containment. Because of their great importance, such vapor-aerosol interactions in the primary system have been extensively studied at many institutions. However, investigations on a laboratory scale are very difficult to perform in such a way that their results can be meaningfully transferred to a full-scale facility. 

The main processes of vapor-aerosol interaction are physical and chemical adsorption, condensation and chemical reaction. In spite of the large sorption capacity of the primary aerosols (see Section 7.3.2.2.), in practice the simple sorption processes seem to be of secondary importance. Condensation and chemical reactions apparently dominate what happens in the system vapor—aerosol. 

Vapor—aerosol interactions which are assumed to take place in the primary system were studied in detail in the British Falcon test facility. This facility, which is schematically shown in Fig. 7.19. (according to Beard et al., 1991), has been specifically designed to investigate the transport and deposition behavior of fission products under severe accident conditions. To produce representative aerosols, fuel pellets containing simulant fission products as well as trace-irradiated fuel pellets, both cladded in Zircaloy, were heated up to 2000 K in a steam—helium atmosphere in the presence of bulk-core materials. Fission product transport could be studied along a pathway which was designed to represent the upper plenum, hot-leg structures and containment. Considerable efforts were made to ensure that, as far as possible, the thermal-hydraulic conditions represented those of a selected accident. 

Figure 7.19. Falcon test facility for investigation of fission product aerosol interactions (schematic) (Beard et al., 1991)...

Beard, A. M., Benson, C. G. Fission product vapour — aerosol interactions in the containment Trace-irradiated fuel studies. Report AEEW-R 2472 (1989)... 

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