Determination of natural radioactivity levels in soil samples from irrigated vegetable farming land in and around Addis Ababa, Ethiopia

Soil samples were collected from vegetable agricultural areas in and around Addis Ababa, and their levels of radioactivity were measured. Gamma spectrometry with high-purity germanium detector was used to quantify radioactivity level. The average concentration of 226Ra, 232Th, and 40K were 32.8 +/- 2.1, 62.4 +/- 4.4, and 544.3 +/- 23.3 Bq kg-1 respectively. The mean values of 232Th and 40K are higher, whereas the value of 226Ra is comparable with world average values. Radiological hazard indices, including radium equivalent activity (Raeq), absorbed dose rate (Dr), outdoor annual effective dose equivalent (Deff), external hazard index (Hex), internal hazard index (Hin), and gamma radiation representative level index (I gamma), were calculated based on the activity concentration of 226Ra, 232Th and 40K. The mean values were 163.9 Bq kg-1, 78.7 nGy h-1, 0.10 mSv y-1, 0.44, 0.53, and 0.60 respectively. All indices are lower than global recommended limit values. These results revealed that radiation hazard due to radionuclides in the soil of the study area is insignificant.