ASSESSMENT OF NATURAL OCCURRING RADIONUCLIDES (40K, 226RA, 232TH) AND HEAVY METALS IN A DISTURBED AND UNDISTURBED SOIL IN THE REGION OF DAKAR, SENEGAL

Radiometric study of natural radioactivity from soil has been carried out to estimate the concentration of gamma-induced radioisotopes and their associated radiological risk in two sampling sites, an uncultivated (undisturbed) and an agricultural site located near an industrial zone. A High Purity Germanium (HPG) detector was used to measure natural gamma emitting radionuclides of 40K, 232Th and 226Ra. With a portable X-ray fluorescence equipment, elementalconcentration of several major elements (Ca, Fe, Ti and K) and minor element (Mn, Zn, As, Zr, P, Cu, Cr and Ni) were measured. The assessment of soil contamination was made by determining the geoaccumulation index, the enrichment factor, the contamination factor and the pollution load index of the various metals targeted in this study. The results indicate moderate soil pollution at the Bargny site by heavy metal As. But also, that this same soil of the Bargny study site was significantly enriched with arsenic and chromium. Levels of radiological hazard indices associated with the measured radioisotopes were inferred. The average of the radium equivalent activity calculated is 65.76 ?3.40 Bq.Kg-1 (disturbed) and 57.25 ? 5.76 (undisturbed); while the mean of the total absorbed gamma dose rate was 30.20?1.56nGy.h-1 (disturbed), and 26.64 ? 2.67 (undisturbed). The External hazard ranged between 0.17 and 0.19 in the disturbed sampling site and 0.12 and 0.17 (Undisturbed).