Navruz Project: Sharing radioactivity data for the rivers of Uzbekistan

The Navruz Project is an international, collaborative, transboundary data collection and data sharing project for rivers in the Aral Sea basin engaging scientist and water managers from Kyrgyzstan, Kazakhstan, Tadjikistan, Uzbekistan and the United States. Standardized sampling and data collection methods assure that data are comparable across international borders, and data are shared among all partners and public through a website at http://ironside.sandia.gov/Central/centralasia.html. As a result of measurement of pollution of water and bottom sediments, the areas with high concentration of radionuclides are revealed. In particular, the Akhangaran and Syr-Darya rivers were studied and it was shown that the beta- and an alpha-activity of Akhangaran river water is significant in the sampling point 19 (former uranium mine). Migration of uranium series radionuclides up to a water deposit (point 21) is observed. At the inflow to the water deposit a small aura of uranium salts was formed due to migration of soluble salts of uranium. However, at confluence of Akhangaran and Syr-Darya the increase of both total beta- and alpha-activity is observed occurring, apparently, due to drainage waters. The beta- and alpha-activity of Syr-Darya river water gradually grows and reaches 1.02 and 0.65 Bq/L, respectively. This increase is possibly caused by the human technogenic activity. Thus, it is necessary to note that the alpha-activity level of water exceeds permissible level for drinking water in practically all investigated points. For the Akhangaran river, alpha-activity of bottom sediments is significant and subjected to seasonal fluctuations (autumn - increase, spring - decrease). Migration of radionuclides in bottom sediments can be observed at the distance up to 60 km from the point where the pollution source is located, which is especially pronounced for uranium series nuclides. This demonstrates the geochemical properties of uranium, and shows that salts of uranium are more mobile, than salts of thorium. (author)