Document Type



Radon gas is the second leading cause of lung cancer worldwide after cigarette smoking. One of the primary controls on radon levels is the underlying geology of a region. Understanding these factors can help prevent radon risk and identify homes that may be at a greater risk of dangerous radon levels. Despite being categorized as a low-risk zone for radon, many radon test results from homes in the Virginia Coastal Plain have been found to have levels exceeding the EPA safe limit of 4 pCi/L. Previous surveys of geologic controls on radon in this region have identified high levels of 238U and 226Ra in the Pliocene Yorktown Formation. This suggests that the Yorktown Formation serves as a potential source of elevated radon levels. We hypothesize that the source of uranium and radium is found at the base of the Yorktown Formation. Ultra low background high resolution gamma spectrometry was used to analyze sediments from several boring sites for 238U, 226Ra, 210Pb. Sediments from the bottom of the Yorktown Formation and upper Eastover Formation contain elevated concentrations of these radionuclides, peaking at 167 Bq/kg 210Pb, 159 Bq/kg 226Ra, and 19.9 Bq/kg 238U. The sample with the highest concentrations contained a black, glossy mineral identified as a phosphate. These grains contained about 2300 Bq/kg 226Ra and have a uranium concentration of 210 ppm, which sits near the 0.2% lower threshold for uranium ore. We explore the sources of radon in the lower Yorktown Formation and use our understanding to create an interactive radon risk map to communicate radon risk to the residents of Williamsburg. This will help homeowners better understand the sources of radon and identify whether or not they could be at risk. This research combines geologic research and communication of a public health issue and will provide a model for understanding and presenting similar issues in other areas.

Date Awarded

Spring 2022



Advisor 1

James M. Kaste

Advisor 2

C.R. Berquist

Available for download on Wednesday, May 08, 2024