Using 220Rn/222Rn ratios as indicators of soil gas transport.
Item
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Title
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Using 220Rn/222Rn ratios as indicators of soil gas transport.
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Identifier
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AAI9417475
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identifier
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9417475
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Creator
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Hutter, Adam Richard.
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Contributor
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Adviser: Anthony Prave
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Geochemistry
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Abstract
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{dollar}\sp{lcub}220{rcub}{dollar}Rn/{dollar}\sp{lcub}222{rcub}{dollar}Rn ratios were used to address changing soil gas transport mode and migration distance as a cause and control of soil gas {dollar}\sp{lcub}222{rcub}{dollar}Rn concentration variations. First, a method to accurately and precisely measure soil gas {dollar}\sp{lcub}220{rcub}{dollar}Rn was developed. The lowest {dollar}\sp{lcub}220{rcub}{dollar}Rn concentration that can be measured using this method while maintaining an uncertainty {dollar}(1\sigma){dollar} of about 30% is approximately 500 Bq m{dollar}\sp{lcub}-3{rcub}{dollar} (13 pCi 1{dollar}\sp{lcub}-1{rcub}).{dollar} The uncertainty can be decreased to about 20% if multiple samples are obtained in series and an arithmetic mean reported. At typical soil gas concentrations, the {dollar}1\sigma{dollar} single-measurement error is approximately 20%. Bi-weekly {dollar}\sp{lcub}220{rcub}{dollar}Rn, {dollar}\sp{lcub}222{rcub}{dollar}Rn, and permeability measurements were obtained at sites in Chester and Matawan, NJ for a period of two years. At a third site, located in Cheesequake State Park, NJ, these measurements were obtained on a bi-weekly basis whenever possible. Soil gas {dollar}\sp{lcub}222{rcub}{dollar}Rn concentrations at the Chester, NJ site were highest during September/October and up to 10x early-winter lows, variations too large to be explained by a diffusion-only equation. At the other two sites, no seasonal {dollar}\sp{lcub}222{rcub}{dollar}Rn variations were observed. Spatial variations in {dollar}\sp{lcub}222{rcub}{dollar}Rn and {dollar}\sp{lcub}220{rcub}{dollar}Rn concentrations up to 10 times over distances on the order of 10 to 12 m were observed. Soil gas {dollar}\sp{lcub}220{rcub}{dollar}Rn concentrations at the Chester, NJ site were highest during mid-summer, with lowest concentrations occurring during mid-winter, as described according to a diffusion-only equation. At the other two sites, no temporal trends in the {dollar}\sp{lcub}220{rcub}{dollar}Rn soil gas concentration were observed. Permeability measurements, thought to be an indicator of soil parameters controlling soil gas {dollar}\sp{lcub}222{rcub}{dollar}Rn variations, showed no correlations with {dollar}\sp{lcub}222{rcub}{dollar}Rn, {dollar}\sp{lcub}220{rcub}{dollar}Rn, or {dollar}\sp{lcub}220{rcub}{dollar}Rn/{dollar}\sp{lcub}222{rcub}{dollar}Rn ratios. The {dollar}\sp{lcub}220{rcub}{dollar}Rn/{dollar}\sp{lcub}222{rcub}{dollar}Rn ratios at the Chester site showed a strong dependence on {dollar}\sp{lcub}222{rcub}{dollar}Rn only, whereas at the Matawan site, the {dollar}\sp{lcub}220{rcub}{dollar}Rn/{dollar}\sp{lcub}222{rcub}{dollar}Rn ratios were controlled by {dollar}\sp{lcub}220{rcub}{dollar}Rn, indicating longer soil gas migration at the Chester site. The data indicate that changing transport mode may be responsible for unexpectedly large seasonal {dollar}\sp{lcub}222{rcub}{dollar}Rn concentrations, thus providing information on transport distances of soil gas, a critical factor in many environmental concerns.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
