Comparison of activity concentration of 238U, 232Th and 40K in different Layers of subsurface Structures in Dei-Dei and Kubwa, Abuja, northcentral Nigeria

• Activity concentration of 238U, 232Th and 40K was noted high.
• The two boreholes show significant different concentrations of 238U,232Th and 40K.
• The Th/U ratio was high in both, but distinctly higher in first borehole.
• 232Th was increasing with depth in site one almost 100%.
• The radiological monitoring on groundwater is recommended.

The study of activity concentration of 232Th, 238U and 40K of rock samples from site one (S1L1–S1L11, 70 m) and site two (S2L1–S2L9, 60 m) boreholes in Dei-Dei and Kubwa was presented and the first time in the region to be compared. Activity concentrations were analysed using a high resolution co-axial HPGe gamma ray spectrometer system. The activity concentration ranges in site one borehole were from 45±1 to 98±6 Bq kg−1 for 232Th, from 18±2 to 37±4 Bq kg−1 for 238U and from 254 ±32 Bq kg−1 to 1195 ±151 Bq kg−1 for 40K. The activity concentration ranges in site two borehole were from 32±3 to 84±7 Bq kg−1 for 232Th, from 15±2 to 52±5 Bq kg−1 for 238U and from 119±15 to 705±94 for 40K Bq kg−1. Significantly higher concentration of 232Th and 238U occurs in samples collected from S1L7, S1L11 and S2L1 layers. These zones experienced granitic intrusions produced by denudation and tectonism. 40K in rock samples of S1L4 and S2L4 activity concentrations is close; it could be that biotite granitic intrusion that is inferred as the formation in that layer reflects the same activity of potassium in rock's radioactivity measurement. The area requires further investigation of soil geochemistry and activity concentration of radionuclides in groundwater.