Using γγ-Coincidence Spectroscopy to Identify Natural Radiation in Soils Near the Mississippi River

Naturally radioactive nuclides present in soils contain background radiation that humans are exposed to every day. Previous research suggests that there are high background radiation areas (HBRAs) caused by climate, geography, wind, and water currents that accumulate a higher concentration of these radionuclides. An investigation of the Nile Delta confirms the presence of minerals rich in U and Th from monazite and zircon, further suggesting that certain locations have a higher concentration of these radionuclides. The present work is a search for monazite in Great River Road State Park, near the Mississippi River. The acquired samples were measured with a low-background NaI(Tl) spectrometer and digital data acquisition system. Using γγ-coincidence spectroscopy to reduce background radiation, we were able to apply coincidence gates of known gamma-ray energies originating from ²³⁸U and ²³²Th decay chains to identify the presence of the radionuclides in the soil samples. From our results, we confirmed that there is an accumulation of minerals containing ²³⁸U and ²³²Th near the river. Our next steps will focus on calculating activities for quantitative results and collecting samples from an extended region along the river.