Uranium content in surface air in Vienna during the years 1963/64 and 1974 - 1978

Air filters collected at a sampling station in Vienna (Hohe Warte) have been analyzed for their uranium content by means of alphaspectrometry. On these filters of the type Whatman 501 the aerosol was deposited over a period of 24 hours using an air flow rate of 100 1/min. Average values for two or three months were achieved taking 20 - 40 filters with a total air volume of 2000 - 8000 m3 for analysis. Such average air concentrations for uranium (238U) were in the range between 10 - 110 aCi/m3 or 30 - 330 pg U(nat)/m3. During the period 1974 - 1978 a mean value of 33.5+- 14.3 aCi/m3 (102 +- 43 pg/m3) was found. Related to the mean dust concentration of this period, the uranium content of the ashed aerosol samples was about 4 ppm. Although the alphaspectrometric results showed a small increase in the isotopic composition for 234U especially during the springtime there was no hint for fallout particles caused by 235U fission bombs from mass spectrometric investigation of these samples. Besides resuspension of soil materials, emission from coal fired stationary sources (Hausbrand) in crowded urban areas were discussed as possible sources of the uranium concentrations found in the surface air. (Author)