Natural Radioactivity of Environmental Samples and their Impact on the Population at Assalamia-Alhomira Area in Yemen

Measurements of the levels of natural backg round level of the radioactiv ity fro m 226 Ra and 232 Th (and their decay progeny), as well as the primo rdial radionuclide 40 K are the main ob jective of the current study. The present work investigated the radioactivity level of the rocks, soil and water samples at Assalamya-Alho mira area, Abyan district in Yemen. Thirty two rocks and soil samples and 3 groundwater samples fro m Assalamya-Alho mira area were analy zed by gamma-ray spectrometry using NaI(Tl) detector with specially designed shield. The concentration of three natural radionuclides namely 226 Ra, 232 Th, and 40 K has been determined. The results showed that these radionuclides were present in concentrations of (48.68±6.7, 28.8±3.3 and 1618±53 Bq kg -1 ), (102.49±8, 149.8±8 and 2120±73 Bq kg -1 ) and (769.5±39, 4125±124 Bq kg -1 and 40 K not detectable) for mig matit ic biotite gneiss , psammit ic and calc-silicate rocks , respectively. The highest activity concentration for 226 Ra and 232 Th is observed in calc-silicate rocks . Fro m the microscopic study of the calc-silicate rocks we noted it consists of Calcite, Carbonate (Ca, Mg-CO3), diopside, magnetite and zircon minerals wh ich accu mulate in limited uranium and thoriu m. For clay and sandy soil the corresponding values were (41.46±5.6, 68.68±6 and 1224.7±31 Bq kg -1 ) and (80.77±4.5, 211.5±14 and 1004.8±40 Bq kg -1 ), respectively. A lso radiu m equivalent activity, total dose rates and external hazard index of the (rocks/soil) samp les in the area under consideration were calcu lated. The radioactivity concentration of 226 Ra and 232 Th for water samples ranged fro m 2.01±0.6 to 6.55±1.4 Bq l -1 and fro m 1.07±0.7 to 2.93±0.67 Bq l -1 , respectively, while 40 K activity was not detectable. The results showed that this area has a h igh background radiat ion due to the presence of Calc-silicate rocks which contain a h igh proportion of natural rad ioactive elements, and therefore represent a danger to the population lives in this area.