Uranium concentrations and isotopic ratios in Austrian drinking waters

摘要

With regard to the discussion about limits for the natural uranium concentration in public drinking water, our investigations present a first survey of the situation in Austria. From different locations ～ 1.5 L samples of tap water were collected. Adding ~(232)U as a spike uranium was separated by anionic exchange and measured α-spectrometrically after microprecipita-tion with neodymium fluoride. Measurements were carried out with a Silicon surface barrier detector, combined with a multi channel analyser system (Canberra, MCA S 100) using counting times of 2000 min. With spike recoveries of 71-100% and a counting efficiency of 28.7% a minimum detectable activity of 0.2 mBq ~(238)UL~(-1) corresponding to 0.015 μg U_((nat)) L~(-1) could be achieved. Our results showed uranium concentrations ranging between less than 0.1 and 17 - in one special case up to 80 - μg U_((nat)) L~(-1) depending on the geological background of the water table used for the water supply. Isotopic ratios of ~(234)U/~(238)U were generally above 1.0 in some cases, even much higher, viz. up to 3.0. Only for one sample this ratio was 0.8. In conclusion, we can say that the World Health Organization (WHO) demand to set a limit of 2.0 μg U_((nat)) L~(-1) would be failed in a lot of regions and could cause serious problems with the public water supply.