Ground radioactivity measurements in South Carolina and Georgia with radioelement analyses of surficial sediments

Abstract

Recently published aeroradioactivity maps of parts of the South Carolina and Georgia Coastal Plain, have defined numerous areas of anowlously high total gamma ray intensity (Coastal Plain Regional Commission and U.S. Geological Survey, 1975, Aeroradioactivity maps of parts of Georgia, South Carolina, and North Carolina: U.S. Geol. Survey Open-file Report 75-400, 1:250,000, 15 pls.). During the present study, areas in South Carolina and Georgia having high total gamma aeroradioactivity were sampled in one of two ways. Individual samples labeled "Georgia grab samples", "Columbia grab samples", and "Frogmore samples" were each collected as close as possible to the center of aeroradioactivity highs. Groups of samples labeled St. Matthews, Tillman, Gray's Hill, Route 99, Route 196, and Route 276 were collected by sampling along existing roads that transect aeroradioactivity highs. At each sample location five to ten pound samples were taken from the top two-to-three inches of sediment. The samples were dried, split, and analysed for uranium, thorium, and potassium by gamma-ray spectrometry. In the accompanying table uranium contents are presented as RAEU (radium equivalent uranium) in parts per million (ppm). Thorium is presented in parts per million (ppm) and potassium in percentage (pct). Ground counts of total gamma intensity were taken in the field with a McPhar IV four-channel scintillometer. Gamma ray intensity is presented as counts per minute (cpm) averaged over ten second intervals. More samples and ground radioactivity measurements were taken than are presented in the following table. Only those samples that were analysed for radioelements are listed. Collection of the "Georgia grab samples" was a joint effort of the Georgia Geologic and Water Division and the U.S. Geological Survey. Brenda B. Higgins, John Hack, Isidore Zeitz and Robert Schmidt provided useful discussions concerning the selection of areas to be sampled.