Examination of the modified monostandard method in neutron activation analysis

The reproducibility, the small scale as well as the large scale variability of¹³⁷Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for¹³⁷Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of¹³⁷Cs (samples within an area of 10×10m²) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable¹³⁷Cs (random soil samples within an area of 100×200 km²) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.