Investigation of the Radiological Impact of Naturally Occurring Radionuclides from the usage of Phosphate and Organic Fertilizers on Farmlands in the New Juaben Municipality of Ghana

ABSTRACT

The radiological impact of naturally occurring radioactive materials (NORMs) from the usage of phosphate and organic fertilizers in the New Juaben Municipality of Ghana was investigated. The activity concentrations of 226Ra, 232Th and 40K were measured in seven (7) widely used phosphate and organic fertilizers using gamma spectroscopy. The activity concentrations were found to be 32.10±2.60 Bq/kg, 12.20±1.60 Bq/kg and 3005.50±68.80 Bq/kg respectively. The radioactivity level index (Iγ ) which gives an estimate of the level of risk associated with natural radionuclides in specific material was found to be higher than the recommended limit of one (1) in some of the fertilizer samples collected from storage. The storage also recorded a relatively high dose rates (ranging from 96-624 μSv/a) compared to the surrounding background (ranging from 109-241 μSv/a) suggesting that the storage of large quantities of these fertilizers can lead to a possible increase in the dose rates. The mean activity concentrations of 226Ra, 232Th and 40K in cultivated (fertilized) soils were found to be 12.50±3.30 Bq/kg, 10.60 ± 2.80 Bq/kg and 206.0 ± 30.2 Bq/kg respectively. These values were relatively higher than those found in their respective virgin (unfertilized) soils (226Ra- 9.0±1.7 Bq/kg; 232Th - 8.10±1.70 Bq/kg; and 40K-139.0±13.3 Bq/kg). This might be considered as an indication that the use of fertilizers to increase soil fertility enhances the level of 226Ra, 232Th and 40K in agricultural soils. The averages of other risk indices such as radium equivalent, the absorbed dose rate in air at 1m above the ground, the mean outdoor annual effective dose and the external hazard index estimated for the cultivated soils were found to be higher than their corresponding virgin soils but generally lower than the world averages. Therefore, the radiological impact associated with NORMs in the cultivated lands as a result of the application of fertilizers is expected to be low however, the storage of large quantities of fertilizers in warehouses could be monitored for the long-term to establish exposure rates of the workers.