Actions for Aerodynamic size associations of natural radioactivity with ambient aerosols

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Aerodynamic size associations of natural radioactivity with ambient aerosols

Author
Bondietti, E. A.
Published
United States : [publisher not identified], 1986
Springfield, Va.: National Technical Information Service, [approximately 1986]
Physical Description
microfiche : negative ; 11 x 15 cm
Additional Creators
Papastefanou, C. and Rangarajan, C.

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Summary
The aerodynamic size of /sup 214/Pb, /sup 212/Pb, /sup 210/Pb, /sup 7/Be, /sup 32/P, /sup 35/S (as SO4/sup 2 -/), and stable SO4/sup 2 -/ was measured using cascade impactors. The activity distribution of /sup 212/Pb and /sup 214/Pb, measured by alpha spectroscopy, was largely associated with aerosols smaller than 0.52 ..mu..m. Based on 46 measurements, the activity median aerodynamic diameter of /sup 212/Pb averaged 0.13 ..mu..m (sigma/sub g/ = 2.97), while /sup 214/Pb averaged 0.16 ..mu..m (sigma/sub g/ = 2.86). The larger median size of /sup 214/Pb was attributed to ..cap alpha..-recoil depletion of smaller aerosols following decay of aerosol-associated /sup 218/Po. Subsequent /sup 214/Pb condensation on all aerosols effectively enriches larger aerosols. /sup 212/Pb does not undergo this recoil-driven redistribution. Low-pressure impactor measurements indicated that the mass median aerodynamic diameter of SO4/sup 2 -/ was about three times larger than the activity median diameter /sup 212/Pb, reflecting differences in atmospheric residence times as well as the differences in surface area and volume distributions of the atmospheric aerosol. Cosmogenic radionuclides, especially /sup 7/Be, were associated with smaller aerosols than SO4/sup 2 -/ regardless of season, while /sup 210/Pb distributions in summer measurements were similar to sulfate but smaller in winter measurements. Even considering recoil following /sup 214/Po ..cap alpha..-decay, the avervage /sup 210/Pb labeled aerosol grows by about a factor of two during its atmospheric lifetime. The presence of 5 to 10% of the /sup 7/Be on aerosols greater than 1 ..mu..m was indicative of post-condensation growth, probably either in the upper atmosphere or after mixing into the boundary layer.
Report Numbers
DE86013414; CONF-860425-35
Other Subject(s)
Collection
NTIS collection.
Note
DOE contract number: AC05-84OR21400
OSTI Identifier 5452416
Research organization: Bhabha Atomic Research Centre, Bombay (India). Div. of Radiological Protection.
Research organization: Oak Ridge National Lab., TN (USA). Environmental Sciences Div.
Research organization: Thessaloniki Univ. (Greece). Dept. of Nuclear Physics.
View MARC record | catkey: 47366978