Date of Award

8-2004

Level of Access

Campus-Only Thesis

Degree Name

Master of Engineering (ME)

Department

Engineering Physics

Advisor

C.T. Hess

Second Committee Member

James McClymer

Third Committee Member

George Bernhardt

Abstract

Radon concentrations and fluxes were measured for two different seasonal snowpacks, one on Bald Mtn. in Dedham and the other on Baldpate Mtn. in Newry, Maine during the winters of 2003 and 2004. An in-pack chilled mirror hygrometer and temperature logging system was developed to monitor snowpack temperature and water vapor density during the radon measurements. Liquid scintillation and gamma spectroscopy analysis of snow samples showed that no particulate radon daughters were trapped in the snow, though substantial concentrations of radon gas were detected in the snowpack. Radon ground flux measurements were performed using a RAD-7 alpha spectrometer and ranged from zero to 0.64 pCi m-2 s-' for frozen and unfrozen ground conditions, respectively. In-pack radon concentration as a function of time was measured using a Honeywell A9000 radon monitor and the RAD-7 instrument and showed average radon concentrations ranging from 10 to 12 pCi L-', though maximum concentrations of over 80 pCi L-' were observed. Wind-driven and natural circulation air flows within the snowpack were shown to be the major factors controlling radon dynamics. Dilution rates of 1.25 pCi L-' h-' were correlated with windspeeds of 9 m s-', while radon concentration rates of 0.8 pCi L-' h-' were observed during periods of calm. Comparison of long term track-etch cup measurements with radon diffusion theory showed that radon within the snowpack rarely exists in steady state distribution due to the ventilation effects of wind and natural circulation air flows. Alpha and gamma spectroscopy analysis was performed for over 60 filtered ice core segments drilled from the glaciers of Mt. Nyainqentanghla and Mt. Everest to establish the depths of fallout horizons used for ice core dating. '37Cs was detected which matched worldwide fallout patterns from 1958 through the present period, including fallout from the Chernobyl accident in 1986 and regional fallout from the Semipalatinsk testing facility in eastern Kazakhstan. Maximum fallout densities of 109.9 Bq m-2 '37Cs were observed during the 1963-65 years. An activity concentration model was developed to aid in properly dating radioactive core sections and in estimating local accumulation rates based on meteorological records from northern India collected during the same period. From these measurements, the average accumulation rates of 0.59 m y-l and 0.74 m y-l water equivalent for Mt. Nyainqentanghla and Mt. Everest coring sites respectively.

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