摘要：AbstractWater supply to the extreme north of Madagascar comes from the Amber Mountain catchment. The objectives of this work are to study the presence of natural radionuclides in the waters from the mountain catchment and investigate their origin by determining the radioactivity levels in water and soil, and their transfer factors. Forty samples were collected from various locations at the study site including 13 of water and 27 of soils. The results for the water samples show that40K,238U series and232Th series activities vary, respectively from 2.7 to 19.8 Bq.l−1, 1.7 to 8.2 Bq.l−1and 0.4 to 3.3 Bq.l−1. For soil samples, the activities are in the range of 126 to 327 Bq.kg−1, 14 to 73 Bq.kg−1and 10 to 402 Bq.kg−1, respectively for the40K, the238U series and the232Th series. Regarding the radionuclide soil-water transfer factors, the mean values for the whole study site are 0.04 for40K, 0.10 for238U series and 0.03 for232Th series. These results show that the Amber Mountain catchment soil radionuclides migrate weakly to the water system and their activities vary widely from one place to another. This low level of migration is explained by the geochemical behavior and the physico-chemical properties of the radionuclides present in the area.
