The geochemistry of uranium, thorium, and radium in soils of the eastern United States
A detailed study of [sup 238]U, [sup 232]Th, and [sup 226]Ra has been conducted on 12 soils in the eastern US to gain understanding relevant to radon hazard, nuclear waste isolation, and geochemistry. Data on parent rocks, vegetation, and selective chemical soil extraction have also been obtained. Soil concentrations are 2 to 7 [sup ppm] [sup 238]U, 3 to 20 ppm [sup 232]Th, and 19 to 100 mBq/g [sup 226]Ra. Soil radiometric content is always greater than bedrock values, and for Th is up to 27-fold higher (up to 15X for U and Ra). Radium-226 never deviates more than +/-0.20 from equilibrium with [sup 238]U . However, in many organic-rich A- horizons , [sup 226]Ra/ [sup 238]U is up to 1.80, and in some lower C-horizons [sup 226]Ra/[sup 238]U is up to 1.5, with 35% of the total [sup 226]Ra cation-exchange-able. Rocks and float from these sites show [sup 226]Ra/[sup 238]U equilibrium values (av. 0.95). High [sup 226]Ra/ [sup 238]U can be explained by the rapid (0.70-1.0 ka) turnover of plant-incorporated [sup 226]Ra ([sup 226]Ra/[sup 238]U up to 65 in vegetation). Adsorption of [sup 226]Ra from soil water over a period of 1.2 ka explains the abundance and form of excess [sup 226]Ra in C-horizons. Shallow radiometric surveys may not be representative because surface horizons are variable and depleted. However, the correlation of U and Th content in the surface relative to average soil could be useful in correcting this type of error. 10% of the total [sup 226]Ra is cation-exchangeable and 26% is associated with soil organic matter at all depths and is unsupported because less than 1.5% of the total [sup 238]U and [sup 232]Th (and [sup 234]U and [sup 230]Th by analogy) is similarly associated. Up to 38%, 68%, and 21% of the total U, Th, and Ra are associated with Fe-oxides. The [sup 222]Rn emanation coefficients of 17 Pennsylvania soils (av. 24%) correlate well with organic-associated [sup 226]Ra. This relation could be useful in assessing soil radon.
- Research Organization:
- Pennsylvania State Univ., Mont Alto, PA (United States)
- OSTI ID:
- 5982419
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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RADIUM 226
GEOCHEMISTRY
THORIUM 232
URANIUM 238
ORGANIC MATTER
RADIOMETRIC SURVEYS
RADON
SOILS
USA
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
CARBON 14 DECAY RADIOISOTOPES
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HEAVY ION DECAY RADIOISOTOPES
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NUCLEI
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RADIUM ISOTOPES
RARE GASES
SPONTANEOUS FISSION RADIOISOTOPES
SURVEYS
THORIUM ISOTOPES
URANIUM ISOTOPES
YEARS LIVING RADIOISOTOPES
540230* - Environment
Terrestrial- Radioactive Materials Monitoring & Transport- (1990-)