EXPERIMENTAL
Collection areas were selected in the states of Georgia, Texas, and Washington, and surface soils were taken according to the pattern shown in figure 1.
Since surface soils are those most frequently encountered in forensic work, about ½ pound of sample was taken from each collection point at depths less than ½ inch. These samples were dried under infrared lamps, the lumps ground in an agate mortar and pestle, and the sample was then sifted through a 60 mesh standard sieve to remove stones and vegetable matter. The sieved portion of the samples was analyzed by both neutron activation analysis and atomic absorption.