Abstract:
Radiometric and Magnetic studies were carried out in Kargi, at 2°28´36.9984˝ and
2°31´14.9988˝ N and 37°32´34.0008˝ and 37°36´6.9984˝ E. The focus of this study was to characterize radio-activity in soil and water, to find out possible causes of radiation in this area by studying magnetic intensities, zones considered anomalous with deepness to magnetic sources and outlining sub-surface structures. 117 soil and 14 water samples were picked from the entire Kargi and analyzed for radionuclides due to 40K, 232Th and 226Ra. Measurement methods of proton magnetometer and γ-spectrometer using a high purity detector – germanium (HPGe) were basically utilized to gauge the magnetic survey and radiological hazard of radio-activities respectively. A total of 51 magnetic field measurements were taken on the eastern part of Kargi, a place suspected to have more concentration of radionuclides. The data was corrected and magnetic anomaly map plotted. Surfer 10 and GeosoftR Oasis Montaj software were used to process the magnetic data. 40K, 232Th and 226Ra had computed mean
activities of 353.20±110.07, 7.97±3.98 and 7.38±2.59 Bq/kg for soil and 3.55±3.04, 2.20±2.74 and 52.68±25.07 Bql-1 for water respectively. Qualitative interpretation from magnetic intensity map showed lows and highs with variation in amplitude between -791 nT to 420 nT, an indication of lineament structures. Euler Deconvolution of magnetic data revealed the structures orientation, their depths together with the alignment of the anomalous zones to the base. Radially averaged power spectrum of magnetic data show depth estimates ranging between 100 m to 480 m indicating the total depth estimate to that that produced the observed anomalies. The values of annual effective doses together with Radium equivalent (Raeq) values for tested soil and water samples were below international standards making this area regarded safe to humans for agricultural practices, buildings, drinking and other purposes. Magnetic anomaly results show that radiation in the area could be originating from base rocks and not buried objects as the rock spreads along the area.
Keywords: Kargi, magnetic survey, radiometric, power spectrum
