The Variability in Fallout Content of Soils and Plants and the Design of Optimum Field Sampling Strategies

Abstract

Sampling was carried out at an upland peat site in Ireland to assess the variability in 137Cs deposition to soils and activity concentration in individual vegetation species. A 3,600 m2 quadrat was laid out, and a soil core was extracted within each of sixteen 20 x 20 cm soil monoliths. The coefficient of variation values for 137Cs deposition and activity in individual soil horizons were in all cases greater than 30%, and the relative variability between corresponding horizons tended to increase with depth. Samples of Calluna vulgaris and Juncus squarrosus were taken at each soil sampling location and coefficients of variation for 137Cs activity in these species were 12 and 20%, respectively. The data was used to examine the relationship between the number of samples analyzed in a survey, the variability within those samples, and the way those two factors affect our ability to detect between-site differences in 137Cs contamination levels. A methodology is developed for detection of between-site differences in 137Cs contamination under different experimental criteria. The data show that, of the sample types examined, between-site differences could be detected most efficiently with C. vulgaris. Because of the variability associated with the 137Cs content of each sample type, between-site differences could be detected with fewer plant samples than soil samples. Plant-soil concentration ratios, transfer factors, and plant-plant ratios were calculated from the data, and the variability associated with each parameter was assessed. The variation among values for plant-plant ratios was less than among concentration ratios, and the greatest spread of values was associated with plant-soil transfer factors.

Distribution of pre- and post-Chernobyl radiocaesium with particle size fractions of soils

“…Large variations in radiocaesium deposition on a very small scale within localised areas following the Chernobyl accident have been reported (Horrill et al, 1990;Henrich et al, 1990;Haugen, 1992;McGee et al, 1995). The differences in caesium concentrations in soil within the watershed can be mainly attributed to the physical redistribution of radionuclides during and shortly after the deposition event.…”

Spatial variability of the vertical migration of fallout 137 Cs in the soil of a pasture, and consequences for long-term predictions

“…Even though Ulsh et al [21] observed similarly high values (CV=0.40 and 0.41, respectively) for alpine and montane sites in Colorado (USA) as compared to our site, on a meadow in the City of Salzburg (Austria), Lettner et al [22] observed for the spatial variability of Chernobylderived 137 Cs fallout on a 1-ha area a value of only CV=0.21. Similarly, Sutherland and de Jong [23] found for a native grassland a CV=0.18, and McGee et al [24] for the integrated 137 Cs deposition at an upland peat site a value of 0.24. For a recent review, see Sutherland [25].…”

Spatial variability of radioactive cesium fallout on grasslands estimated in various scales

“…After the Chernobyl accident in 1986, many field studies of fallout radioactive material distribution have been conducted (Bachhuber et al 1987;Simopoulos 1989;Padovani et al 1990;Sutherland and de Jong 1990;Haugen 1992;McGee et al 1995;Golosov et al 2000;Lettner et al 2000;Bossow et al 2001;Sadremomtaz et al 2010). The distribution of radioactive materials was found to be uneven within grasslands (Lettner et al 2000;Korobova and Romanov 2011) and was affected by topography (Kachanoski 1987;Loughran et al 2003).…”