Assessment of Natural Radioactivity Concentration in Soils from Irrigation Farming Areas within Kudan Local Government Area, Kaduna State, Nigeria

The activity concentrations of natural radionuclides 238U, 232Th and 40K in soil samples from Kudan Local Government Area irrigation farming areas have been evaluated using gamma-ray spectrometry. The results of the activity concentrations of 238U, 232Th and 40K range between 18.15 to 34.66 Bq/kg, 16.01 to 18.83 Bq/kg and 205.51 to 461.25 Bq/kg respectively. The activity concentration of 40K was seen to be higher than the world average value of 370 Bq/kg at Kauran Wali South (GO3K) 375.25 Bq/kg, Doka (GB1K) 389.60 Bq/kg, Kauran Wali North (GB2K) 420.15 Bq/kg, Likoro (GB4K) 383.65 Bq/kg, Garu (GB5K) 461.25 Bq/kg, Zabi (GB6K) 372.76 Bq/kg and Kudan (GB7K) 382.50 Bq/kg. The activity concentrations of 238U and 232Th were observed to be high at Garu (GB5K), with values of 34.66 and 18.83 Bq/kg respectively, however, these values were still below the world average value of 40 Bq/kg as reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSEAR) in 2000. The average values for the indoor absorbed dose rate (Din), Internal Hazard Index (Hin), External Hazard Index (Hex) and Indoor Annual Effective Dose (ADE) were evaluated to be 83.07 nGy/hr, 0.35, 0.28 and 0.41 mSv respectively. The estimated radiological indices were seen to fall within the internationally acceptable limits except for the indoor absorbed dose rate (Din) whose values were all higher than the acceptable limit of 60 nGy/hr as recommended by UNSCEAR in 2000. The high values obtained from this study could be attributed to the excessive use of fertilizers by the farmers within the study area.