Origin and release date assessment of environmental plutonium by isotopic composition.

The origin and release date of environmental plutonium have been assessed by the measurement of plutonium and americium isotopic composition. The applicability and sensitivity of different plutonium isotope ratios, (240)Pu/(239)Pu and (241)Pu/(239)Pu measured by inductively coupled plasma sector field mass spectrometry and (238)Pu/(239)Pu analysed by alpha spectrometry, have been evaluated for origin determination in several types of environmental samples. With use of mixing models the contribution of different sources (e.g. global fallout or Chernobyl) can be calculated. By the measurement of the (241)Am/(241)Pu isotope ratio, the release date (i.e. formation of (241)Pu by irradiation) can be estimated in environmental samples, which is an important parameter to distinguish recent plutonium release from previous (e.g. Chernobyl) emissions.