Aerosol measurements

For determination of the aerodynamic diameters of particles, the most commonly apphcable methods for particle-size analysis are those based on inertia aerosol centrifuges, cyclones, and inertial impactors (Lundgren et al.. Aerosol Measurement, University of Florida, Gainesville, 1979 and Liu, Fine Paiiicles—Aerosol Generation, Measurement, Sampling, and Analysis, Academic, New York, 1976). Impactors are the most commonly used. Nevertheless, impactor measurements are subject to numerous errors [Rao and Whitby, Am. Ind. Hyg. A.s.soc.]., 38, 174 (1977) Marple and WiUeke, "Inertial Impactors, in Lundgren et al.. Aerosol Measurement and Fuchs, "Aerosol Impactors, in Shaw, Fundamentals of Aerosol Sci-... 

Willeke, K., and Baron, P. A., "Aerosol Measurement—Principles, Techniques, and Applications." Van Nostrand Reinhold, New York, 1993... 

The fraction of unattached daughters (fp), the equilibrium factor (F) and the activity median diameter (AMD) are plotted in Figure 6 for all the measurements. The AMD is derived from the aerosol measurements. These three parameters are important in the dosimetric models. At the top of Figure 6 the effective dose equivalent is plotted, computed with two models called the J-E (Jacobi-Eisfeld) and J-B (James-Birchall) models in the NEA-report (1983, table 2.9, linear interpolation between AMD=0.1 and 0.2 ym). The figure also shows the effective dose equivalent calculated from the equilibrium equivalent radon concentrations with the NEA dose conversion factor (NEA,1983, table 2.11). 

In 1975 there was a new development in the use of wire screens Sinclair and Hoopes (1975) described a diffusion battery (for measuring the particle size of aerosols) made of very fine 635-mesh stainless steel screen. An empirical equation was developed for the collection efficiency. This diffusion battery has become one of the standard techniques in aerosol measurements. Later, Sinclair et al (1978) described a screen diffusion battery configuration suited for measuring the activity - weighted size distribution of radon daughter aerosols. 

Aerodynamic Size Distributions of Naturally-Radioactive Aerosols. Measurements of radionuclide distributions using cascade impactors indicate that Be-7 and Pb-210 are associated with larger aerosols than Pb-212 and Pb-214 (Robig et al., 1980 Papastefanou and Bondietti, 1986). Measurements of Pb-210 associations over oceans indicated activity median aerodynamic diameters (AMAD) near 0.6 pm (Sanak et al., 1981). The impactor measurements of Moore et al. (1980) on Pb-210, Bi-210, and Sr-90 sizes in continental air indicated that about 80% of the activity from all three nuclides was associated with aerosols below 0.3 pm. That work also determined that the mean age of aerosol Pb-210 was about a week. Knuth et al. (1983) compared Pb-210 and stable Pb sizes at a continental location and found that 78% of the Pb-210 found below 1.73 pm was smaller than 0.58 pm. Young (1974) reported that the most of the Be-7 in the atmosphere was associated with submicron aerosols. 

Figure 4. Deposition of submicrometer aerosols measured for cyclic flow through a hollow cast of the human bronchial tree, compared with calculated values.

The model results were compared with the HOx concentrations measured by the FAGE (Fluorescence Assay by Gas Expansion) technique during four days of clean Southern Ocean marine boundary layer (MBL) air. The models overestimated OH concentrations by about 10% on two days and about 20% on the other two days. HO2 concentrations were measured during two of these days and the models overestimated the measured concentrations by about 40%. Better agreement with measured HO2 was observed by using data from several MBL aerosol measurements to estimate the aerosol surface area and by increasing the HO2 uptake coefficient to unity. This reduced the modelled HO2 overestimate by 40%, with little effect on OH, because of the poor HO2 to OH conversion at the low ambient NOx concentrations. 

To help reduce these Influences, various data normalization techniques may be applied. Analysis of deposition (concentration times volume) rather than concentration alone may help avoid variability associated with precipitation amount. Another approach which was previously applied to aerosol measurements In Sweden ( )... 

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. 

Whitby, K.T. Cantrell, B.K., "Electrical Aerosol Analyzer Constants," in Aerosol Measurement, D.A. Lundgren, S.S. Harris, Jr., W.H. Marlow, M. Lippmann, W.E. Clark, M.D. Durham, Eds, University Presses of Florida, Gainsville, Florida, 1979. 

On-line aerosol measurements were made using a Thermo-Systems, Inc., Model 3030 Electrical Aerosol Size Analyzer (EAA). This instrument uses the electrical mobility of the particles to measure the size distribution in the 0.01 to 0.5 ym range. 

These dust storm aerosol measurements are not Included in the weekly average concentration in Figure 7. 

The Owens Lake brine analysis of Table V Indicates that the Na/S ratio should be approximately 3.8 for lake bed materials, which agrees quite well with the ambient ratio measured at Keeler. The above data suggests that airborne sulfur aerosols measured in the Owens Valley are in the form of sulfates which are suspended from the efflorescent crust on the Owens Lake bed. Therefore, if we assume that all the sulfur measured at each site is in the form of sulfate, then during a dust storm, the sulfate standard for the state of California (25pg/m ) is violated near the Owens Lake. It should be noted that the sulfate standard was developed for very fine acidic aerosols. The sulfates measured here are larger and basic particles, so their toxicity may be different from particles for which the standard was written. The calculated sulfate levels at each site during a dust storm are listed in Table VI. 

Zhang, X. Q., P. H. McMurry, S. V. Hering, and G. S. Casuccio, Mixing Characteristics and Water Content of Submicron Aerosols Measured in Los Angeles and at the Grand Canyon, Atmos. Environ., 27A, 1593-1607 (1993). 

Details of the calibration, use, performance, and artifactual problems are given in a proceedings entitled Aerosol Measurement (Lundgren et al., 1979) this also shows data for the mobility distribution for monodis-perse aerosols. 

Baron, P. A., M. K. Mazumder, and Y. S. Cheng, Direct-Reading Techniques Using Optical Particle Detection, in Aerosol Measurement Principles, Techniques, and Applications (K. Willeke and P. A. Baron, Eds.), pp. 381-409, Van Nostrand Reinhold, New York, 1993. 

Durham, J. L L. L. Spiller, and T. G. Ellestad, Nitric Acid-Nitrate Aerosol Measurements by a Diffusion Denuder A Performance Evaluation, Atmos. Environ., 21, 589-598 (1987). 

Fitz, D. R., G. J. Doyle, and J. N. Pitts, Jr., An Ultrahigh Volume Sampler for the Multiple Filter Collection of Respirable Particulate Matter, . /. Air Pollut. Control Assoc., 33, 877-879 (1983). Flagan, R. C History of Electrical Aerosol Measurements, Aerosol Sci. Technol., 28, 301-380 (1998). 

Saros, M. T., R. J. Weber, J. J. Marti, and P. H. McMurry, Ultrafine Aerosol Measurement Using a Condensation Nucleus Counter with Pulse Height Analysis, Aerosol Sci. Techno , 25, 200-213 (1996). 

Sinha, M. P., and S. K. Friedlander, Mass Distribution of Chemical Species in a Polydisperse Aerosol Measurement of Sodium Chloride in Particles by Mass Spectrometry, J. Colloid Inteface Set., 112, 573-582 (1986). 

Bertram, A. K., D. D. Patterson, and J. J. Sloan, Mechanisms and Temperatures for the Freezing of Sulfuric Acid Aerosols Measured by FTIR Extinction Spectroscopy, J. Phys. Chem., 100, 2376-2383 (1996). 

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