Condensation, aerosol

Particle size range (um) Ions Nuclei Visabilit> Suspended or settleable nonairbome Uisptersion aerosol Condensation aerosol Pollen and spores Sedimenlatiofi,. lifiusion, and settling... 

Williamson, A.D, Smith, W.B. "A Dilution Sampling System for Condensation Aerosol Measurements Design Specifications," Southern Research Institute, Special Report //SORI-EAS-79-793, 1979. 

Heinrich, U., M. Roller, and F. Pott, Estimation of a Lifetime Unit Lung Cancer Risk for Benzol a Ipyrene Based on Tumour Rates in Rats Exposed to Coal Tar/Pitch Condensation Aerosol, Toxicol. Lett., 72, 155-161 (1994). 

Lead, tellurium, and selenium aerosols in 0.01 to 1 micrometer size range could be generated using a condensation aerosol technique. The particle size is dependent on the generation temperature. The aerosol output is dependent on both the generation temperature and the carrier gas flow rate. 

When H-bombs are exploded at high altitude no ground-based material is incorporated, so the condensation aerosol particles are very small, with 90% of the activity in particles less than 0.3 pm in diameter. 

The size of the particles is determined by the particular material selected and the vapor concentration used. In practice, limited variation in particle size can be achieved for a particular aerosol material because conditions for stable aerosol formation require a particular set of thermal and vapor concentration conditions. The monodispersity of the aerosol can be improved by revaporization and recondensation. In systems in which the condensation occurs in a container with a high ratio of volume to surface areas, relatively monodisperse particles can be obtained (frg 1.1). Otherwise, the particle size varies with the proximity to the wall. In cylindrical or tubular systems, such as in the condensation aerosol generator developed by Liu et al. [10] or the falling-film generator, the particle size that is produced varies radially (see Ref. [3]). A more monodisperse aerosol can be produced by extracting the central portion of the flow, which is less subject to wall effects. Liu et al. [10] found that the monodispersity improved from a ug value of 1.35 to 1.15 by using only the central 5% of the aerosol flow. A commercial version of a modified Sinclair-LaMer generator is available with particle size control suited for inhalation studies [11]. 

Fij ure 6.13 Condensation aerosol generator The nuntber concentrations of the polydispi rsp aerosol produced in the nebuli/cr ore nearly equal to that of the monodisporsc aerosol. Each evaporating droplet from the polydisperse aerosol leaves behind a residue that serves as a nucleus for the ntonudisperse aerosol. (After Liu et al., 1966.)... 

The partial pressure driving force for growth, pi —is a function of time determined by the conditions of the system. For example, in the condensation aerosol generator (Chapter 6), it is determined by the cooling rate in the chimney. None of the quantities... 

Thus the result of particle growth in the chamber is to convert a monodisperse aerosol into a polydisperse aerosol. This is the reverse of what occurs in a condensation aerosol generator (Chapter 10). 

Heinrich U, Dungworth DL, Pott F, et al. 1994b. The carcinogenic effects of carbon black particles and tar-pitch condensation aerosol after inhalation exposure of rats. Ann Occup Hyg 38(Suppl. 1) 351-356. 

Heinrich U, Pott F, Roller M. 1994a. Estimation of a lifetime unit lung cancer risk for benzo(a)pyrene (BAP) based on tumor rates in rats exposed to coal tar/pitch condensation aerosol (CTP). Zentral Hyg Umwelt 195 155-156. 

Walter, H. (1973). Coagulation and size distribution of condensation aerosols. J. Aerosol Sci. 4, 1-15. 

Peterson, T. W., Gelbard, F., and Seinfeld, J. H. (1978) Dynamics of source-reinforced, coagulating, and condensing aerosols, J. Colloid Interface Sci. 63, 426-445. 

Vapour diffiision transition Heavy molecules (condensate aerosols, cluster, and particles < pm) Brownian and eddy diffusion and thermophoresis... 

A specific class of aerosol ions are condensed aerosol ions produced as a result of the condensation of gaseous matter on the cluster ions. In aerosol physics the process is called ion-induced nucleation it is considered as one among the processes of gas-to-particle conversion. The condensed aerosol ions have an inherent charge. Their sizes and mobilities are between the sizes and mobilities of cluster ions and of ordinary aerosol ions. Water and standard constituents of atmospheric air are not able to condense on the cluster ions in the real atmosphere. Thus the concentration of condensed aerosol ions depends on the trace constituents in the air and is very low in unpolluted air. Knowledge about condensed aerosol ions is poor because of measurement difficulties. 

For the understanding and description of aerosol particle interaction processes, the two most important questions are what the two-particle interaction forces are and what the particle-surface interaction forces are. Since a substantial fraction of condensational aerosol particles from all sources nucleate to form spheres prior to subsequent coagulation and deposition, the description of the interaction of spheres is of central interest. 

Condensation aerosols can also be prepared by chemical reactions involving two gaseous reactants... 

Stauffer, D. (1976) Kinetic theory of two-component ("heteromolecular") nucleation and condensation,/. Aerosol. Sci. 7, 319. 

The transport and the deposition of the condensation aerosols in the reactor coolant system depend on a number of parameters such as heat and mass transfer, chemical reactions and aerosol kinetics. With respect to their transport behavior, all the substances volatilized from the reactor core do not directly enter the primary circuit. First, they have to pass through the upper plenum of the reactor pressure vessel their residence time here depends on the specific accident sequence. The masses deposited here on the walls and structures will differ and, consequently, the fraction which, after having passed through the upper plenum, enters the actual primary circuit will depend on the details of the accident. 

An important property of the primary condensation aerosols which is of high importance for the behavior of the volatile fission products is their large surface area. The surface area of the aerosols within the primary system of a severely damaged PWR can be approximately 500 times greater than that of the primary system structural surfaces (Beard et al., 1988 b). An aerosol mass of 1000 kg formed in a core melting process and having a specific surface area of 1 m /g has a total surface area of about 10 m. If one assinnes that the space needed for one fission... 

Ligotke, M. W., Eschbach, E. J., Winegardner, W. K. Ice-condenser aerosol tests. Report NUREG/CR-5768 (1991)... 

Gelbard, F. M., and J. H. Seinfeld, Dynamics of Source-Reinforced, Coagulating, and Condensing Aerosols, J. Colloid Interf. Sci., 63, 426-445 (1978a). 

Particles also have direct health effects when inhaled. This is especially true of very small particles that can be carried into the innermost parts (alveoli) of lungs. The particles that are most damaging are very small ones less than 2.5 pm in size (less than 1/30 the diameter of a human hair) designated PM2 5 These are mostly condensation aerosols and may contain toxic elements, such as arsenic, acids, such as H2SO4, and carcinogenic polycyclic aromatic hydrocarbons including benzo(a)-pyrene. Because of their very small size, these particles have very high surface-to-volume ratios and biochemically active surfaces. 

Explain why condensation aerosols are generally regarded as of greater health risks than are dispersion aerosols. Give two examples of dispersion aerosols that have caused health problems. 

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