Aerosol conditions

UV-B spectral global irradiance and total ozone direct sun measurements carried out at Lisbon during 1990 with a MARK 11 Brewer ozone spectrophotometer and with clear-sky conditions were used for comparison at several zenith angles, total ozone and aerosol conditions. However, because aerosol optical depth measurements were not available at this time it was decided to use T5oo=0.0 for the model input. The results of the Model/Brewer ratios for global spectral irradiances are shown in Figure 5. The results are similar and consistent with the earlier LOWTRAN 7 (6) comparison, where the ratio approaches to unity as the wavelength increases,... 

The concerns addressed in our feasibility studies of He-jet activity transport were 1) Will the He-jet technique work at the beam intensities that exist at LAMPF 2) What transport efficiencies can be expected for both fission and spallation products 3) What is the time dependence of the activity transported and 4) What aerosols and/or aerosol conditions are optimum ... 

Since such trace gases seem to be particularly efficient reactants for ions, it is conceivable that the tropospheric ion composition responds sensitively to aerosol conditions and meteorological factors. 

This introductory chapter addresses the concept of the aerosol condition of matter first by explaining how it arose and then by delineating the physical questions which are common to all such systems. Section 1.1 reviews possible definitions of "aerosol" and Sect.1.2 discusses the division among the component studies of aerosol physics which is followed in these volumes. The discussion of aerosol microphysics in Sect.1.2.2 establishes its relationship to the conventional investigations of basic physics. To be of value both to the basic scientist seeking the context of his work in other natural sciences and in technology and conversely to the engineer or natural scientist curious of how his domain of interest is related to aerosol microphysics, Sect.1,3 briefly discusses examples of where aerosols arise. 

The dose conversion factor, DCF, in effective dose per exposure unit is calculated by taking into account the dose function of the particle diameter (Figure 5.4) and the radon decay product characteristics. The dose conversion factors for living and work places with typical activity size distributions, as a function of the unattached fraction, fp, are illustrated in Figures 5.13 and 5.14, respectively. The value of the dose conversion factor, DCFae, for fp = 0 represents the dose contribution of the radon product aerosols. The values of dose conversion factor in Figure 5.14 are based on aerosol conditions which are typical for many workplaces. 

Average dose conversion factor, DCF, for the inhalation of unattached, DCFu, and aerosol-attached, DCFae. radon decay products in air of different locations arranged according to aerosol conditions. ITbb ITbb Ai = 0- 0 0.15 0.05 is the relative cancer sensitivity distribution of the bronchial, Wbb. and alveolar, u)ai> regions of the thoracic lung, v = inhalation rate, Z = aerosol particle concentration. The indices i = n, a and c represent the nucleation (Aitken nuclei), accumulation and coarse particle modes... 

Fatty acid film formation and the associated surface tension depression has been studied extensively for idealized systems (i.e., pure water subphases) by the colloid science community, starting with the work of Langmuir nearly a century ago [211, 212]. Since it is known that fatty acid phase behavior depends strongly on factors such as pH, the presence of salts, and mixed organic content [6, 213, 214], it is not possible to extrapolate measurements performed in pure water or very dilute systems to the relevant aerosol conditions. Here we focus on studies which move towards more atmospherically relevant systems. The results of several studies are summarized in Table 4. 

The size of the droplets formed in an aerosol has been examined for a range of conditions important in ICP/MS and can be predicted from an experimentally determined empirical formula (Figure 19.6). Of the two terms in the formula, the first is most important, except at very low relative flow rates. At low relative velocity of liquid and gas, simple droplet formation is observed, but as the relative velocity increases, the stream of liquid begins to flutter and to break apart into long thinner streamlets, which then break into droplets. At even higher relative velocity, the liquid surface is stripped off, and the thin films so-formed are broken down into... 

Verification of the microbial retention efficiency of the membrane filters may be undertaken using either Hquid or aerosol challenge tests. A Hquid challenge test is more stringent. Furthermore, this test can provide retention information for process conditions such as extreme moisture after sterilization or air entrained with water drops. A Hquid challenge is performed using a protocol similar to that described for Hquid filtration. 

Considerable developmental effort is being devoted to aerosol formulations using the compressed gases given in Table 4. These propellants are used in some food and industrial aerosols. Carbon dioxide and nitrous oxide, which tend to be more soluble, are often preferred. When some of the compressed gas dissolves in the product concentrate, there is partial replenishment of the headspace as the gas is expelled. Hence, the greater the gas solubiUty, the more gas is available to maintain the initial conditions. 

Hexafluorophosphoric Acid. Hexafluorophosphoric acid (3) is present under ambient conditions only as an aqueous solution because the anhydrous acid dissociates rapidly to HF and PF at 25°C (56). The commercially available HPF is approximately 60% HPF based on PF analysis with HF, HPO2F2, HPO F, and H PO ia equiUbrium equivalent to about 11% additional HPF. The acid is a colorless Hquid which fumes considerably owiag to formation of an HF aerosol. Frequently, the commercially available acid has a dark honey color which is thought to be reduced phosphate species. This color can be removed by oxidation with a small amount of nitric acid. When the hexafluorophosphoric acid is diluted, it slowly hydrolyzes to the other fluorophosphoric acids and finally phosphoric acid. In concentrated solutions, the hexafluorophosphoric acid estabUshes equiUbrium with its hydrolysis products ia relatively low concentration. Hexafluorophosphoric acid hexahydrate [40209-76-5] 6 P 31.5°C, also forms (66). This... 

Hydrogen chloride in the lungs can cause pulmonary edema, a life threatening condition. In order for HCl in air to reach the lungs, it must be transported either as an aerosol or as a deposit on soot particles of less than 3 p.m in diameter. A procedure for the removal of 99% of the HCl from municipal waste incinerators has been developed (87). Lime is employed as a dry adsorbent which is collected in a filter bag system. 

Ha2ard is the likelihood that the known toxicity of a material will be exhibited under specific conditions of use. It follows that the toxicity of a material, ie, its potential to produce injury, is but one of many considerations to be taken into account in assessment procedures with respect to defining ha2ard. The following are equally important factors that need to be considered physicochemical properties of the material use pattern of the material and characteristics of the environment where the material is handled source of exposure, normal and accidental control measures used to regulate exposure the duration, magnitude, and frequency of exposure route of exposure and physical nature of exposure conditions, eg, gas, aerosol, or Hquid population exposed and variabiUty in exposure conditions and experience with exposed human populations. 

Dry methylene chloride does not react with the common metals under normal conditions however, a reaction with aluminum can be initiated, sometimes explosively, by the addition of small amounts of other halogenated solvents or an aromatic solvent (7). Iron catalyzes the reaction, and this can be significant in the handling and storage of methylene chloride and in the formulation of products, eg, in aluminum aerosol containers of pigmented paints, where the conditions necessary for the reaction are commonly found. A typical reaction in this process is shown in equation 2. 

In addition to the deposition mechanisms themselves, methods for preliminary conditioning of aerosols may be used to increase the effectiveness of the deposition mechanisms subsequently apphed. One such conditioning method consists of imposing on the gas nigh-intensity acoustic vibrations to cause collisions and flocculation of the aerosol particles, producing large particles that can be separated by simple inertial devices such as cyclones. This process, termed sonic (or acoustic) agglomeration, has attained only hmited commercial acceptance. 

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