Radiation Exposure Levels and Excess Lifetime Cancer Risk Associated with Soil, Water and Sub-Surface Rocks in Kargi Area, Marsabit - Kenya

Abstract

Radiometric and Magnetic studies were carried out in Kargi area, located between latitudes 2.476944° and 2.520833° and longitudes 37.542778° and 37.601944°, with approximately 31.26 km2 coverage area. Escalated number of cancer disease cases among humans and animal deaths in this region led to this research work. The aim of the study was to characterize radioactivity in soil and water, magnetic intensities, delineating subsurface structures, anomalous zones with depth to magnetic sources. Gamma ray spectrometer, Proton magnetometer, together with GPS were used for radiometric, magnetic and location points respectively. 14 water and 117 soil samples were collected from the area, examined to have their natural radioactivities due to 40K, 232Th and 226Ra radionuclides measured. 51 magnetometer readings were taken on the eastern part of Kargi, covering an area of 13 km2. Gamma spectrometry method making use of a high purity germanium (HPGe) detector and proton magnetometer were used to gauge the radiological hazard of radioactivities and measure magnetic field respectively. Surfer 10 and GeosoftR Oasis Montaj software were used to map and process magnetic data respectively. Results from radioactivities for 40K, 232Th and 226Ra, gave mean calculated activities as 353.19 ± 110.07, 7.98 ± 3.98 and 7.37 ± 2.60 Bq∙kg−1 for soil and 56.93±20.16, 2.80±2.45, 4.31±2.52 and 11.19±5.74 Bql-1 for water respectively. Evaluation of magnetic images showed lows and highs with variation in amplitude between -791 nT to 420 nT, an indication of lineament structures. Euler Deconvolution was used to image structures and estimate depths to the magnetic basement. Radially averaged power spectrum showed depth estimates to magnetic sources ranging between 100 m to 480. Since internal, external, radium equivalent indices and annual effective dose values are lower than the worldwide acceptable limits, these soils and/or rocks are safe and are recommended for use in building with proper ventilation as any amount of radiation is still harmful. studies were carried out in Kargi area, located between latitudes 2.476944° and 2.520833° and longitudes 37.542778° and 37.601944°, with approximately 31.26 km2 coverage area. Escalated number of cancer disease cases among humans and animal deaths in this region led to this research work. The aim of the study was to characterize radioactivity in soil and water, magnetic intensities, delineating subsurface structures, anomalous zones with depth to magnetic sources. Gamma ray spectrometer, Proton magnetometer, together with GPS were used for radiometric, magnetic and location points respectively. 14 water and 117 soil samples were collected from the area, examined to have their natural radioactivities due to 40K, 232Th and 226Ra radionuclides measured. 51 magnetometer readings were taken on the eastern part of Kargi, covering an area of 13 km2. Gamma spectrometry method making use of a high purity germanium (HPGe) detector and proton magnetometer were used to gauge the radiological hazard of radioactivities and measure magnetic field respectively. Surfer 10 and GeosoftR Oasis Montaj software were used to map and process magnetic data respectively. Results from radioactivities for 40K, 232Th and 226Ra, gave mean calculated activities as 353.19 ± 110.07, 7.98 ± 3.98 and 7.37 ± 2.60 Bq∙kg−1 for soil and 56.93±20.16, 2.80±2.45, 4.31±2.52 and 11.19±5.74 Bql-1 for water respectively. Evaluation of magnetic images showed lows and highs with variation in amplitude between -791 nT to 420 nT, an indication of lineament structures. Euler Deconvolution was used to image structures and estimate depths to the magnetic basement. Radially averaged power spectrum showed depth estimates to magnetic sources ranging between 100 m to 480. Since internal, external, radium equivalent indices and annual effective dose values are lower than the worldwide acceptable limits, these soils and/or rocks are safe and are recommended for use in building with proper ventilation as any amount of radiation is still harmful.