THESIS TITLE: Radiological Assessment of ²³⁸U, ²³²Th and ⁴⁰K in The Top Soils of Ahero Paddy Fields of Kisumu County, Kenya

STUDENT’S NAME: Mukanda Kere Wanyama

SUPERVISORS:

1. Dr.  Michael Nakitare Waswa

2. Dr. Linda Ouma

ABSTRACT

Naturally occurring radioactivity has existed in our environment since the creation of the earth. ²³⁸U, ²³²Th and ⁴⁰K radionuclides are found in significant concentrations in soils. These radionuclides pose exposure risks which can lead to health related problems like lung cancer and bone cancer especially when they exceed the recommended safety limits. A radiological assessment of ²³⁸U, ²³²Th and ⁴⁰K in the top soils of Ahero paddy fields of Kisumu County was done using NaI(TI) gamma ray spectroscopy. A total of 17 samples were collected at a depth of 15 – 20 cm and measured for activity concentrations, absorbed dose rate, Annual effective dose rate, and radium equivalent and hazard indices. Samples were collected from fields at various stages of farming process: four (4) weeks after transplanting (field 1), during transplanting (field 2), after harvesting and land ploughed (field 3) and field 4 where rice farming had not been done for 2 years. ²³⁸U activity concentrations ranged from a minimum of 9.93 Bq/kg to a maximum of 44.93 Bq/kg, ²³²Th activity concentrations ranged from 56.69 Bq/kg to a maximum of 144.30 Bq/kg while the activity concentrations of ⁴⁰K ranged from a minimum of 19.21 Bq/kg to a maximum of 217.08 Bq/kg. The average absorbed dose rates from the collected samples ranged from to a minimum of 52.59 nGy/h to a maximum of 91.79 nGy/h. The average AED (in) and AED (out) values from all the samples collected from all the fields were all below the recommended safety limit of 1 mSv/y. the average radium equivalent levels ranged from a minimum of 168.90 Bq/kg to a maximum of 208.81 Bq/kg.  .The average external hazard index for the samples ranged from 0.37mSv/y to 0.65mSv/y while the internal hazard index for the samples ranged from 0.32mSv/y to 0.57mSv/y. The findings of the study have shown that there is no radiological health hazard to the farmers and the general public associated with the top soils of the area of study