Isotope survey used to better understand the Danube

The Water Resources Programme and collaborating Austrian research partners have been supporting the International Commission for the Protection of the Danube River (ICPDR) to help improve understanding of the basin surface water and groundwater systems through the application of isotope techniques. In the summer of 2007, the ICPDR launched the second Joint Danube Survey (JDS-2) to collect information on the river's water quality and ecological status. The survey entailed collection and analysis of samples for a wide variety of water quality parameters such as organics, nutrients, and metals, as well as analyses of sediments, fish and other biota. The survey began in Regensburg, Germany and finished 50 days later in the Black Sea. Samples were collected by ship at over 90 points along 2 375 km of the river covering 10 different countries. Results are now available on the ICPDR website www.icpdr.org/JDS. As part of JDS-2, the IAEA and collaborators established a sampling and analysis program for stable and radioactive isotopes. This was the first time isotope measurements have been included as part of a JDS. The main objectives of the isotope survey were primarily hydrological. Since there are only a few existing environmental isotope data from the Danube (especially from the lower Danube), the JDS-2 was a welcome opportunity to improve the data base for environmental isotopes in this region. Grab samples were collected within the upper one meter for stable isotopes of water (2H and 18O), and tritium (3H) at the 95 official JDS sampling points, including 74 sites in the Danube and 21 sites in tributaries and arms. Additional points near the left and right banks, above and below the confluences of eight major tributaries, were sampled for stable isotopes and 3H to provide information on mixing with tributary waters. A radon survey (222Rn) was also completed using an on-board analyzer. This summary describes some example results from the isotope survey, and additional details and interpretations are planned for a future paper