$sup 239$Pu, $sup 240$Pu, and $sup 241$Am contamination of vegetation in aged fallout areas

Vegetation studies in aged plutonium fallout areas at the Nevada Test Site and Tonopah Test Range showed variations in the $sup 239$-$sup 240$Pu and $sup 241$Am contamination levels attributable to differences in the amounts of resuspendable particulate material superficially entrapped upon plant foliage. There was reasonable agreement between the mean activity levels in vegetation and soil samples collected across different activity strata defined by Fidler survey instrument within each fallout area. The ratio of vegetation Pu to soil Pu tended to increase moving out from higher to lower activity strata, which might reflect the increasing proportion of finer particulate material initially deposited in fallout debris at greater distance from ground zero. The Pu/Am ratio was reasonably constant for vegetation samples collected from a given fallout area. This ratio, however, varied among separate test events primarily as the result of differences in the ingrowth of $sup 241$Am within the aged source materials. Inventory estimates indicate that standing vegetation contributes a rather insignificant portion of the total contaminant remaining in these aged fallout areas. (auth