Advisor

Scott F. Burns

Date of Award

6-14-1995

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Geology

Department

Geology

Physical Description

1 online resource (x, 220 p., maps)

DOI

10.15760/etd.6891

Abstract

Radon, a naturally occurring radioactive gas produced as one of the decay products of soil/rock uranium and thorium, is considered to be a leading cause of pulmonary disease. Gamma spectrometry of 146 samples of soil were used to quantify radon source potential relative to lithology by measuring Bi 214 activity of the U 238 decay series. Additional soil radio nuclide data (Th 232, Ac 228, K40 and Cs137 ) were used to help identify regional source provenance geochemistry and soil development. Ac 228, Bi. 214 and Th232 activities in northwest Oregon soils range from five to 55 Bq/kg, while K40 activities range from 53 to 750 Bq/kg. In northwest Oregon, three radon potential zones are defined by soil Bi 214 activity: 62% falls within Low 1 zones (less than 25 Bq/kg), 35% falls within Low 2 zones (25 to 45 Bq/kg) and 3% falls within Moderate zones (greater than 45 Bq/kg). Low 1 zones are significantly influenced by proximal volcanic source provenances, while Low 2 zones and Moderate zones are considered to reflect distal plutonic and/or metamorphic source provenances. Soil radionuclide activity has been shown to vary with soil deve1opment. Th 232:K40 soi1 activity ratios and Bi214 soil activity are found to increase with soil development. Th 232 :K40 soil activity ratios of soils developed on, or from previously unweathered rock and sediment range between 0.03 and 0.08. Th232 :K40 activity ratios of soils developed on, or from previously weathered rock and sediment are often greater than 0.12. Soil radionuclide activity data of this study do not identify areas with known elevated indoor radon. Soil permeability data provided by the Soil Conservation Service (SCS) do identify the Alameda Ridge area of north and northeast Portland, an area with known elevated indoor radon. In Salem, Soil Conservation Service soil permeability data do not identify areas with elevated indoor radon. However, some areas of Salem with elevated indoor radon have landslides capable of affecting subsurface permeabilities. There is a possibility that subsurface soil permeabilities, favorable for convective soil gas transport and elevated indoor radon, exist at depths greater than those measured by the Soil Conservation Service.

Description

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL

Persistent Identifier

https://archives.pdx.edu/ds/psu/29018

Ashbaugh_Plate1.pdf (19869 kB)
Plate 1. Radon Potential Zones of Northwest Oregon

Ashbaugh_Plate2.pdf (11070 kB)
Plate 2. Site Locations of Samples

Ashbaugh_Plate3.pdf (18454 kB)
Plate 3. Radon Potential Zones of Portland, Oregon

Ashbaugh_Plate4.pdf (15815 kB)
Plate 4. Radon Potential Zones of Salem, Oregon

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