Aerosol, radioactive

Radioactive aerosols can be classified in the following categories (a) Radioactive aerosols associated with radioactive nuclides of cosmogenic origin, such as Be, Na, and (b) radon and thoron decay product aerosols associated with Po Pb, Pb, Pb, and °Po, (c) fission product radionuclide aerosols associated with Sr, Sr, Cs, Ru, isif 132-pg i40g (-(j) radioactive aerosols associated with the operation of high-energy ac- 

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Denmark 1.5 days after the explosion. Air samples collected at Roskilde, Denmark on April 27-28, contained a mean air concentration of 241Am of 5.2 pBq/m3 (0.14 fCi/m3). In May 1986, the mean concentration was 11 pBq/m3 (0.30 fCi/m3) (Aarkrog 1988). Whereas debris from nuclear weapons testing is injected into the stratosphere, debris from Chernobyl was injected into the troposphere. As the mean residence time in the troposphere is 20-40 days, it would appear that the fallout would have decreased to very low levels by the end of 1986. However, from the levels of other radioactive elements, this was not the case. Sequential extraction studies were performed on aerosols collected in Lithuania after dust storms in September 1992 carried radioactive aerosols to the region from contaminated areas of the Ukraine and Belarus. The fraction distribution of241 Am in the aerosol samples was approximately (fraction, percent) organically-bound, 18% oxide-bound, 10% acid-soluble, 36% and residual, 32% (Lujaniene et al. 1999). Very little americium was found in the more readily extractable exchangeable and water soluble and specifically adsorbed fractions. 

LaFuma J, Nenot JC, Morin M, et al. 1974. Respiratory carcinogenesis in rats after inhalation of radioactive aerosols of actinides and lanthanides in various physicochemical forms. In Karbe E, Park JF, eds. Experimental lung cancer Carcinogenesis and bioassays, international symposium. New York Springer, 443-453. 

Ikebe. Y., M. Shimo, and T. Iida, A study on the Behavior of Atmospheric Radioactive Aerosols in Facilities, Department of Nuclear Engineering, Faculty of Engineering, Nagoya University, Nagoya(1979) (in Japanese). 

Busigin, A., A.W. van der Vooren and C.R. Phillips, Measurement of the Total and Radioactive Aerosol Size Distributions in a Canadian Uranium Mine, Amer. Ind. Hyg. Assoc. J. 42 310-314 (1981). 

Mercer, T.T. and W.A. Stowe, Radioactive Aerosols Produced by Radon in Room Air Inhaled Particles III (Edited by Walton, W.H.) pp. 839-850, Old Waking Unwin Bros. Ltd., (1971). 

Sinclair, D., A.C. George, and E.O. Knutson, Application of Diffusion Batteries to Measurement of Submicron Radioactive Aerosols, in Airborne Radioactivity (D.T. Shaw, ed.) American Nuclear Society, La Grange Park, IL, pp. 103-114 (1978). 

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. 

Boecker, 1973) exposed to other radioactive aerosols was also reviewed. An analysis of the data from both studies suggested that for beagles exposed by inhalation to radioactive 144Ce aerosols, individuals in the population would receive radiation doses to a given organ within a fog-normal distribution characterized by a geometric standard deviation of 2. 

Cuddihy, R. G. and Boecker, B. B. (1973). Controlled administration of respiratory tract burdens of inhaled radioactive aerosols in beagle dogs, Toxicol Appl. Pharmacol. 25, 597. 

The characteristic feature of the uranium exploration industry is the radioactivity of all wastes. The quality of these wastes, such as radon, radioactive aerosols, and dust emitted to the atmosphere, depends on mine production and the radioactive budget in the mines. For example, middle range mine exploring the ores with n x 10 1-10 2% of U content emits to the atmosphere up to 8 x 1010 Bq/day of radon. 

As Martell has pointed out (30), in the region of the stratospheric large particle layer near 18-20 km. altitude, radioactive aerosol particles become attached to natural sulfate particles in the size range of about 0.1-0.4 jumeter radius. Subsequent upward transport of the radioactive aerosols is opposed by gravitational sedimentation. This combination of processes affords an explanation for the observed accumulation of 210Pb near 20 km. in the tropical stratosphere (2). At higher latitudes where slow mean motions are directed poleward and downward, no such accumulation is possible. 

The tungsten tracer observations and the excess -1(,Pb in the tropical atmosphere are explained by the competing influence of sedimentation, slow mean motions, and eddy mixing. Radioactive aerosols in the lower stratosphere become attached to the natural sulfate particles which are of sufficient size and density to oppose upward transport to levels much above 20-25 km. (30). The coefficient of meridional eddy mixing appears to increase with latitude near the equator (29), with little seasonal change (33). At higher latitudes the rate of poleward transport exhibits large seasonal variations, with a maximum in winter (33). 

It is well established that in non-arid regions, precipitation is the primary means by which contaminating aerosols are removed from the atmosphere. Many chemical, physical, and meteorological parameters affect the micro, meso, and synoptic scale processes through which precipitation transports radioactive aerosols from atmosphere to ground. These parameters include the radioactivity component of the natural aerosols, the processes by which water vapor condenses and grows to raindrops, and the incorporation of the radioactive aerosol into the precipitation. Thus, the prediction of specific deposition from fundamental considerations has proved to be difficult because of the many uncertainties yet prevalent in these processes. Many attempts have been made to evaluate the deposition of these aerosols by empirical studies. 

Pacific cyclones represent the major source of precipitation over the western United States. Therefore, they also represent a major source of deposition of contaminant aerosols in the waters of these states. The examination of radioactive aerosols in precipitation resulting from Pacific cyclones is thus of interest in understanding the transport of atmospheric aerosols to the ground by precipitation. 

The most important chemical parameter affecting the deposition and subsequent mobility of radioactive aerosols, such as the nuclides 90Sr and 137Cs examined in this study, is their solubility in rainwater. If these aerosols are dissolved in precipitation, the main factor in their transport is the movement of the rainwater, not the transport of insoluble aerosol particles. Huff and Kruger (2) examined the solubility products of strontium and chemically similar compounds which may carry trace amounts of 90Sr, and they estimated that strontium should be soluble in precipitation. Solubility tables also indicate that cesium compounds likely to exist in precipitation should be soluble. It was noted that the possibility did exist that some of the fission product "Sr and 137Cs might be bound within the structure of insoluble natural aerosols or nuclear weapon debris. 

Radioactive aerosols are intercepted by vegetation either by mechanical trapping of dry particulate matter or in the rainfall which wets the vegetation. 

The effect of infiltrating water is a downward migration of radioactive aerosols from the surface into the soil profile. As infiltrating water percolates downward, ion exchange occurs between the soil and water phases, and gradually the radioactive aerosols are left behind in the soil phase. The migration process removes some of the deposited aerosol from the soil surface, altering the aerosol transport rate out of the watershed. 

Both equations consider the migration of a single input source of "Sr in the top layer. Under natural conditions however, additional input of radioactive aerosol to the source layer is furnished by the incoming precipitation. 

Model computations begin with an estimate of the radioactive aerosol content of the infiltrating solution. This may be based on either direct input from vegetal storage in the absence of overland flow or the sheet flow aerosol concentration computed on the basis of exchange reactions during overland runoff. The known value of the surface soil content prior to infiltration is also used to determine the total content of the... 

The final step in the hydrologic transport of radioactive aerosols through a watershed is transmission through the channel system to the basin outlet. Aerosol input to the main channels in the basin from land surface runoff and interflow must pass through the channel system in a manner governed by the laws of hydraulics. Simulation of the timing of radioaerosol outflow from the basin must therefore include a consideration of channel transport. 

Leary, J. A., Fitzgibbon, F. J., Particle-Size Determination in Radioactive Aerosols by... 

Radioactive aerosols Aerosols containing radionuclides are called radioactive aerosols. They have natural and artificial origin. Artificial radioactive aerosols are formed during nuclear explosions, in accelerator tunnels during operation, and during heating operation of activated metals. 

Interception and retention of radioactive aerosols by vegetation. Atmospheric Environment, 4, 57-78. 

Drevinsky, P.J. Pecci, J. (1965) Size and vertical distributions of stratospheric radioactive aerosols. In Radioactive Fallout from Nuclear Weapons Tests, ed. A.W. Element Jr. CONF765. U.S. Dept of Commerce. N.T.I.S. Springfield, Va. 

Miller, C.W. (1980) An analysis of measured values for the fraction of a radioactive aerosol intercepted by vegetation. Health Physics, 38, 705-12. 

The environmental effects of radioactive aerosols depend on their transfer to surfaces, and this is one reason for studying this process. The other reason is that radioactive aerosols can be used, in the wind tunnel or in the field, to obtain results of general interest. There are several advantages in using radioactivity ... 

Wind tunnels provide a partial solution to the study of deposition of particles in the natural environment. The main advantage is that conditions are reproducible. Also, if radioactive aerosols are used, much less activity is needed than in field experiments. The disadvantages are the limitations on the height of the canopy and on the fetch... 

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