Activity median aerodynamic diameter AMAD particles

Activity Median Aerodynamic Diameter (AMAD)—The diameter of a unit-density sphere with the same terminal settling velocity in air as that of the aerosol particle whose activity is the median for the entire size distribution of the aerosol. 

The activity median aerodynamic diameter (AMAD) for the particles is assumed to be 1.5-2.1 pm average 1.8 pm (see Pozzani 1949). Mortality, body weight changes, standard hematology (except in the... 

Depending on the plutonium compound, it may be either soluble or insoluble. Plutonium as the citrate or nitrate was more soluble than the dioxide compound. Plutonium dioxides prepared at temperatures of 700°C or higher had a slower absorption rate compared to air-oxidized forms (Sanders and Mahaffey 1979). The absorption of plutonium was also dependent upon its respirable fraction, or that fraction of the total concentration of plutonium which may deposit in the nonciliated part of the lung. The respirable fraction of plutonium is composed of particles less than 10 om Activity Median Aerodynamic- Diameter (AMAD), which indicates that only particles less than 10 om AMAD would be retained in the nonciliated part of the lung and would be available for absorption (NEA/OECD 1981 Volchoketal. 1974). 

From the 11 measurements carried out over a 2-year period including all seasons, Papastefanou and loannidou (1995) reported that the activity median aerodynamic diameter (AMAD) varied from 0.76 to 1.18 pm (average 0.90 pm) and the geometric standard deviation (a ) varied from 1.86 to 2.77 (average 2.24). The AMAD and (ag) calculations were made by plotting the cumulative distributions on log-normal probability paper. They also showed that 60% of the Be activity was associated with particles with diameter smaller than 1.1 pm. 

E). The data rather indicate that the activity median aerodynamic diameter, AMAD, of Be-aerosols increases with increasing latitude (latitudinal effect). As cosmic radiation increases with latitude, the numbers of Be atoms and ions formed also increase with latitude and so there are more Be atoms and ions available either to form small aerosol particles in the nucleation (Aitken nuclei) mode and then growing or to be attached directly to the existing large particles in the accumulation and in the coarse particle modes thereby increasing the AMAD of the Be-aerosols. 

Table 2.4 summarises the activity median aerodynamic diameter (AMAD) of Pb and Be and the mass median aerodynamic diameter (MMAD) of SO found in measurements made in the spring period. Beryllium-7 activity size distributions are substantially smaller than 804 , regardless of the time of year. The Pb data included in Table 2.4, while limited, suggest that summer aerosol particle sizes are larger than winter aerosol particle sizes. 

In contrast to the findings of Bondietti and Brantley (1986), lost et al. (1986) found no increase of the activity median aerodynamic diameter, AMAD, during the measurement period. They believed that this increase might not reflect the original release at Chernobyl, but was due to transport effects. Apart from this, the activity size distribution of Cs from the Chernobyl fallout was very similar to the activity size distribution in the fallout from nuclear weapons tests (Lockhart et al., 1965b), in contrast to the activity size distribution found in the stratosphere, which is shifted towards smaller particles (Persson and Sisefsky, 1971). 

Lujaniene et al. (1997) reported that the activity median aerodynamic diameter, AMAD, of the soluble aerosols of Cs of Chernobyl origin varied in the range 0.10 to 0.86 pm at Vilnius, Lithuania (54°41 N, 25°19 E), and the size of caesium radioisotopes stuck to insoluble aerosol particles in all the samples was similar (about 1 pm). 

Activity median aerodynamic diameter (AMAD) of atmospheric aerosol particles (pm)... 

A method for estimating the residence time of tropospheric aerosol particles associated with the cosmic-ray produced radionuclides, such as Be, is based on the aerosol particle growth rate, which is the change of particle diameter with time, which was estimated to be 0.004 to 0.005 pmh (McMurry and Wilson, 1982) and the difference between the activity median aerodynamic diameter, AMAD, of a radionuclide, e.g. Be, and the size of the Aitken nuclei in the size distribution of the aerosol particles, which is 0.015 pm (NRC, 1979). The AMAD of all radionuclides is in the accumulation mode of the size distribution of atmospheric aerosol particles which ranges between 0.1 and 2.0 pm (NRC, 1979 Papastefanou and Bondietti, 1987). 

Table 4.1 shows data for the activity median aerodynamic diameter, AMAD, of atmospheric aerosol particles associated with Be and Pb atoms. Regarding the Be aerosols, the AMAD values varied from 0.33 to 1.18 pm (Bondietti and Brantley, 1986 Papastefanou and loannidou, 1995 Reineking and Porstendbrfer, 1995 Winkler et al., 1998 Yu and Lee, 2002 Porstendbrfer and Griindel, 2003), while for the Pb-aerosols, the AMAD values varied from 0.28 to 0.77 pm (Sanak et al., 1981 Reineking and Porstendorfer, 1995 WinMer et al., 1998 Porstendorfer and Griindel, 2003). The residence time, tr, is described by the formula... 

Parameters of the activity size distribution of the aerosol-attached short-Uved radon decay products in air at different locations. Activity median aerodynamic diameter, AMAD, noted as AMD geometric standard deviation, Og fraction of the mode, fpi. The indices i = n, a and c represent the nucleation (Aitken nuclei), accumulation and coarse particles modes, Z = aerosol particle concentrations... 

AMAD (activity median aerodynamic diameter). The value of aerodynantic diameter such that 50% of the airborne activity in a specified aerosol is associated with particles smaller than the AMAD and 50% of the activity is... 

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