Radon generation and transport in soils

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5003030

Washington, J W

Soil-gas Rn, soil moisture, and soil temperature have been monitored for one year or more at five sites in Pennsylvania which have been characterized for soil bulk density, porosity, diffusivity and permeability. Radon-222 and {sup 222}Rn vary in an annual, approximately sinusoidal pattern having an amplitude of 2- to 10-fold at all five sites. Since Rn partitioning between gas and water is temperature sensitive, and because soil moisture and temperature change in annual cycles, much of the variability in {sup 222}Rn occurs in annual cycles. Therefore knowledge of regional and temporal soil moisture and temperature patterns allows estimates of {sup 222}Rn in soil gas. These estimates suggest Rn is least elevated by moisture in cold, arid soils, and temporal variability will be small in arid soils. In areas where the soil substrate has lower Rn, emanation coefficient, or bulk density than the soil, soil-gas Rn can diffuse into the substrate. Under extreme conditions the Rn concentration can have a gradient towards the rock. Soil cores were used to measure the fraction of Rn exhaling to the gas phase over a range of moisture tensions. The greatest exhaling fraction generally occurred at intermediate moisture tension. The low exhaling fraction in dry soil is attributed to lodging of recoiling Rn in adjacent soil grains. The low exhaling fraction in wet soil is attributed to waterinhibited diffusion. This core method provides reasonable estimates of the combined effects of emanation and diffusion on Rn in soils. Bulk diffusion coefficients and permeability coefficients generally decrease by nearly 1 and 2 orders of magnitude respectively from the eluvial to the illuvial horizons in typical soils.

• Research Organization: Pennsylvania State Univ., University Park, PA (United States)
• OSTI ID: 5003030
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540230* -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- (1990-)
ALPHA DECAY RADIOISOTOPES
ANNUAL VARIATIONS
DAYS LIVING RADIOISOTOPES
DEVELOPED COUNTRIES
ECOLOGICAL CONCENTRATION
ENVIRONMENTAL TRANSPORT
EVEN-EVEN NUCLEI
HEAVY NUCLEI
ISOTOPES
LAND POLLUTION
MASS TRANSFER
MOISTURE
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NORTH AMERICA
NUCLEI
PENNSYLVANIA
POLLUTION
RADIATION MONITORING
RADIOECOLOGICAL CONCENTRATION
RADIOISOTOPES
RADIONUCLIDE MIGRATION
RADON 222
RADON ISOTOPES
SOILS
TEMPERATURE DEPENDENCE
USA
VARIATIONS