Gross Alpha and Gross Beta Radioactivity in Drinkable Water and Soil/Sediment around Oil Spill Sites in Delta State, Nigeria

Abstract

The gross alpha and beta activity concentration in drinkable water and soil/sediment from oil spilled communities of Delta state have been carried out using calibrated MPC 2000 Protean ORTEC desktop gross alpha/beta counter. A total of 22 water samples (11 River water and 11 well water) and 22 soil/sediment (11 soil and 11 sediment) were collected in 2-litre plastic containers with about 1% air space left for thermal expansion and black polyethene bags respectively. All the samples were prepared following international standard organization (ISO) procedure. The result showed that gross alpha activity in River water ranged from 0.013±0.005 to 0.0783±0.015 Bql-1 while the gross beta activity concentration in River water ranged from 0.0073±0.015 to 0.0928 ±0.024 Bql-1. The gross alpha and beta activity in ground (well) water ranged from 0.018±0.006 to 0.0817±0.014 Bql-1 and 0.0126 ±0.013 to 0.173±0.063 Bql-1 respectively. The mean gross alpha and beta activity in soil and sediment are 12.0±1.0 and 23.27±3.0 Bq/kg and 23.0±4.0 and 21.73± 15.0 Bq/kg respectively. The total annual effective dose estimated from both alpha and beta emitting radionuclides in water resources sampled, ranged between 0.007 to 0.063 mSvy-1 in river water and 0.021 to 0.102 mSvy-1 for well water. The annual gonadal dose resulting from gross alpha and beta activity in surface and ground water ranges from 0.019 to 0.238 mSvy-1 and 0.037 to 0.406 mSvy-1 respectively. The highest gonad dose of 0.238 mSvy-1 and 0.439 mSvy-1 was obtained in surface water (OTU1) and ground water (OTU2) respectively. The estimated excess lifetime cancer risks range from 0.024 x 10-3 to 0.220 x 10-3 and 0.039 x 10-3 to 0.358 x 10-3 for river and well water respectively. The result showed a significant relationship in both surface and ground water with regression values of 0.66 and 0.84 respectively. This implies that the same radionuclide is responsible for both alpha and beta activities in the water studied. The result of this study show that all the water resources sampled pose no immediate health risk to the populace though, there is little radioactive contamination of the sampled water arising from oil spillages and may be effluent discharge into the surface water. Following no threshold model, the water sampled need to be treated to remove the radionuclide in it through ion exchange technology or reverse osmosis technology before consuming to avoid long term internal exposure.