Use of anthropogenic radioisotopes to estimate rates of soil redistribution by wind II: The potential for future use of 239+240Pu

In the previous paper, the use of soilborne Cs-137 from atmospheric fallout to estimate rates of soil redistribution, particularly by wind, was reviewed. This method relies on the assumption that the source of Cs-137 in the soil profile is from atmospheric fallout following the period of atmospheric weapons testing so that the temporal and, to a certain extent, the spatial patterns of Cs-137 deposition are known. One of the major limitations occurs when local or regional sources of Cs-137 contamination mask the pulse from global fallout, making temporal estimates of redistribution difficult or impossible. Like Cs-137, Pu exhibits strong affinity for binding to soil particle surfaces, and therefore, re-distribution of Pu inventory indicates inferred soil re-distribution. Compared to Cs-137, Pu-239 and Pu-240 offer several important advantages: (a) the two major Pu isotopes have much longer half-lives than Cs-137 and (b) the ratio Pu-240/Pu-239 is used to examine whether the Pu is from stratospheric fallout. In this paper, we review the literature concerning Pu in soil and of current attempts to use this tracer to estimate rates of soil redistribution. We also present preliminary, unpublished data from a pilot study designed to test whether or not Pu239+240 can be used to estimate rates of soil redistribution by wind. Based on similarities of profile distribution and relative inventories between Cs-137 measurements and Pu239+240 measurements of split samples from a series of fields with documented wind erosion histories, we conclude that Pu239+240 may well be the anthropogenic radioisotope of choice for future soil redistribution investigations. Published by Elsevier B.V.