Assessment of Natural Radionuclides in the Top Soil Sample of Ahero Fields, Kenya

A total of 17 soil samples of Ahero fields were collected at a depth of 15 – 20 cm; five samples each of mass 170g were collected from field 1, 2, 3 and two samples from field 4. The field 1 was where rice seedlings were already transplanted, field 2 was one in which transplanting was being done, field 3 was one in which rice had been harvested and the field had just been ploughed while field 4 was a field in which farming had not been done for two years. The activity concentrations were measured, identified and detected using NaI(Ti) detector that were used in calculation of Radium Equivalent, External Hazard Indices and Internal Hazard Indices. The average radium equivalent were 185.82 ± 7.04 Bq/kg, 119.19 ± 5.95 Bq/kg, 168.78 ± 8.44 Bq/kg and 208.81 ± 10.44 Bq/kg for fields 1, 2, 3 and 4 respectively. The average internal hazard index was 0.50 ± 0.02 mSv/y, 0.32± 0.01 mSv/y, 0.45 ± 0.03 mSv/y and 0.57± 0.03 mSv/y for fields 1, 2, 3 and 4 respectively. On the other hand, the average external hazard indices for the fields were 0.59 ± 0.02 mSv/y, 0.37± 0.01 mSv/y, 0.54± 0.02 mSv/y and 0.65± 0.03 mSv/y for fields 1, 2, 3 and 4 respectively. Generally, the results from the study indicate that the radiological health risk associated with the top soils of the study area is insignificant.