Temporal variation analysis of plutonium baseline concentration in surface air from selected sites in the continental US

The temporal variation of plutonium concentrations in surface air was assessed for the Us Department of Energy's (DOE) monitoring sites near Richland, Washington and Chicago, Illinois using historical databases from the Batelle Pacific Northwest Laboratory (PNL) and the Argonne National Laboratory-East (ANL). The data show that Pu-239.240 air concentrations post-1984 are still detectable with analytical techniques used in monitoring fallout, whereas Pu-238 concentrations are not. These Pu-239.240 values are suggested to represent a 'post-fallout equilibrium' concentration in surface air at the two DOE sites. The PNL and ANL Pu-239.240 post-1984 average monthly values are mostly between 0.01 and 0.1 mu Bq m(-3) and fall within the range observed in Europe as well as in four other US cities through the US environmental Protection Agency's Environmental Radiation Ambient Monitoring System (ERAMS) network. Temporal analysis of the post-fallout monthly data for PNL and for the three sites at ANL show that Pu-239.240 concentrations fall within a predictable range of limiting values. The month-to-month fluctuations are quantified into tolerance limits at the 95% confidence level in that PNL data yielded a monthly change that was within +/-0.13 mu Bq m(-3). The limits found for the three ANL sites are +/-0.14 mu Bq m(-3) for site 12N; +/-0.06 and +/-0.07 mu Bq m(-3) for sites 71 and Off-Site, respectively. Magnitudes of the monthly concentration changes are less than the observed post-fallout concentration ranges of Pu-239.240, and therefore, may be useful in flagging unexpected sources of plutonium in the environment. Copyright (C) 1996 Elsevier Science Limited