SEQUENTIAL EXTRACTION OF FALLOUT RADIOCESIUM FROM THE SOIL - SMALL-SCALE AND LARGE-SCALE SPATIAL VARIABILITY

The reproducibility, the small scale as well as the large scale variab ility of Cs-137 extracted sequentially from the soil by using a modifi ed Tessier procedure was investigated sit several grassland sites in B avaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, al l 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 varia tion (CV) for the reproducibility of the extraction procedure for Cs-1 37 was (with some exceotions) around 10-20% for all fractions. For the small scale variability of Cs-137 (samples within an area of 10 x 10 m(2)) the values for the CV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractab le Cs-137 (random soil samples within an area of 100 x 200 km(2)) was higher for all fractions, even though only moderately. The implication s of these results with respect to a sampling design are discussed.