LEVEL OF NATURAL AND ARTIFICIAL RADIOACTIVITY IN ALGERIA

A national environmental sampling program was carried out during 1993 to determine natural and artificial radionuclides contents in the (0-1 5 cm) upper layer of the soil. The main objective was to establish a r adioactive reference level in the whole territory, since I-131, Cs-134 and Cs-137 were detected in most of the analysed samples collected ri ght after the Chernobyl accident (May 1986). Soil samples were analyse d by direct counting by gamma-ray spectrometry. In addition, terrestri al gamma-ray dose rates in air have been measured out of doors through out Algeria. In each of the 48 administrative divisions of the country selected sites were chosen to collect soil samples and measure gamma- ray dose rates. The gamma-emitting radionuclides resulting from the ra dioactive decay of U-238 and Th-232, K-40 and Cs-137 were detected in most of the analysed samples. Radioactivity concentrations in Bq kg(-1 ) dry mass in soil samples of Ra-226, Pb-214, Bi-214, Pb-212, Ac-228, K-40 and Cs-137 range between (5-176), (2-107), (3-65), (2-97), (3-144 ), (36-1405) and (0.3-41) respectively. In addition, six selected soil samples were analysed to determine plutonium isotopes contents. Radio activity concentrations in Po kg(-1) dry mass of Pu-238 and Pu239 + 24 0 vary between (0.012-0.013) and (0.24-0.61) respectively. The dose ra tes in air measured over the whole country were found to range between 20 and 133 nGy h(-1). Presence of Cs-137 has been clearly observed. A n approach has been made to determine its origin, considering the glob al fallout, the Chernobyl accident and the French nuclear bomb tests i n the 60s as the main potential sources. It is concluded that Algeria has indeed been affected by the Chernobyl accident. (C) 1998 Elsevier Science Ltd. All rights reserved.