Sampling Variability in Radionuclide Concentrations in Plants Native to the Colorado Front Range

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Abstract
Concentrations of gross gamma radioactivity and individual radionuclides were measured in twelve species of native plants which were collected in the Colorado Front Range in 1963–64. Replicate collections from established plots were carried out in order to secure estimates of plot sampling variability. For gross gamma radioactivity and individual radionuclides, most of the species studied had coefficients of variation within the range of 9–22%. In general, low-growing forms such as grasses and forbs were more variable than shrubs, which in turn were more variable than trees. Many species exhibited plot variances which differed among sampling locations and dates. The changes in variances with dates appeared to be related to phenological stages of the plants. Most of the data appeared to be distributed log-normally. Data suggested that “pooling” tends to decrease within-plot variability. Laboratory and counting variances averaged less than 19% of the plot sampling variances. Heterogeneous variance among plots and among species was more common for 137Cs than for the other nuclides studied.