A COMPARISON OF TECHNIQUES USED TO ESTIMATE THE AMOUNT OF RESUSPENDEDSOIL ON PLANT-SURFACES

The objectives of this study were to compare four common techniques us ed to estimate soil mass loadings on plant surfaces and to assess the need to account for particle-size distributions of both the soil trace r and contaminant of concern within the soil. Soil loadings (g soil kg (-1) dried plant) from split samples collected in a pasture near Chern obyl were estimated using soil tracers of plutonium analyzed via alpha spectroscopy (mean +/- standard error; 1.0 +/- 0.2), titanium analyze d with an inductive coupled plasma spectrometer; (3.6 +/- 0.6), and ne utron activation analysis for scandium (8.1 +/- 1.6), as well as simpl y washing the soil off the vegetation (34.1 +/- 5.6). Differences were significant at p < 0.001. We also found that soil loading estimates f rom any one technique varied by a factor of 10 depending on the soil p article size used in the calculations. This was because soil loadings decreased when smaller-sized soil fractions dominated the resuspension process. However, the percent of the plant's total contamination attr ibutable to soil loading increased with smaller soil particles. Smalle r soil particles apparently contribute less to the mass of soil loadin g (g soil kg(-1) dry plant), but more to the total plant contamination (Bq) because of the higher concentration of contaminant found in the smaller-sized soil fractions. Differences in mass loading estimates du e to the technique chosen (a factor of 10), or due to differences in e lemental concentration as a result of the soil particle size used in t he calculation (also a factor of 10), were greater than the natural va riability observed in the field (2.5).