Laura Mahoney

Publication Date

4-1984

Advisor(s) - Committee Chair

Ernest Bondietti, Charles Garten

Comments

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Degree Program

Department of Physics and Astronomy

Degree Type

Master of Science

Abstract

Measurements of natural beryllium-7 (7Be) were made in field vegetation and rainwater at the Department of Energy’s Oak Ridge Reservation throughout the months of July 1982 to June 1983. Laboratory experiments were also conducted on the adsorption and desorption of 7Be, cesium-137 (137Cs), lead-210 (210Pb), and iodine-131 (131I) to the foliage of fescue, 3 varieties of beans, and loblolly pine. The field loss of artificially applied 7Be to field fescue was also measured. The weathering half-life (TW) was found to be 36.5 days during November-January 1982-83; no difference was found in the loss of 7Be during the months March-May 1983, TW = 38.5 days. The loss of sulfur-35 (35S) was studied concurrently with the spring loss of 7Be; the TW for 35S was much smaller, equal to 18.4 days. The interception fraction, r, was determined experimentally in the field using the flux of 7Be in rainwater incident upon clover; the mean value was 0.172. Total deposition velocities were estimated using monthly 7Be rainwater concentrations and quarterly air concentrations; the yearly average was 1.66 cm/sec. An equation for predicting vegetation concentrations was derived for 7Be from the U.S. Nuclear Regulatory Commission’s Guide 1.109. Generic and site-specific values for deposition rate, interception fraction, effective half-life, exposure time, and biomass density were summarized separately and the derived equation was employed to make predictions of monthly 7Be vegetation concentrations. These predictions were compared to actual field observations. With the exception of the month of May, both generic and site-specific predictions were found to underestimate the actual 7Be vegetation concentrations.

Disciplines

Atomic, Molecular and Optical Physics | Earth Sciences | Environmental Health and Protection | Environmental Monitoring | Environmental Sciences | Physical Sciences and Mathematics | Physics

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