Plutonium isotopes in ground-level air in Northern Germany since 1990

The activity concentrations, ratios and seasonal fluctuations of plutonium isotopes in ground-level air in Northern Germany are reported for the years 1990 to 1997. The Pu239+240 activity concentrations (a) measured on quarterly samples lie in a range 0.4 nBq/m(3)<a<4 nBq/m(3). The Pu-238 activity concentrations are lesser by up to a factor of 0.1 (0.1 nBq/m(3)<a<0.8 nBq/m(3)). The total activity concentration shows a typical seasonal fluctuation in the time period under review. In a few quarterly samples the activity ratio of a(Pu-238)/a(Pu239+240) is significantly increased.