greater than or equal to 0.1 indicates that the data sets are similar; a p value of less than 0.1 suggests that they are not similar.
Soil is a valuable environmental monitoring medium because it can accumulate contaminants from both current air emissions and resuspended materials. Hence, soil sampling and analysis evaluates long-term contamination trends and monitors environmental radionuclide inventories (DOE 1991a). In 1994, 20 surface soil samples were taken to evaluate potential radiological impacts from Hanford operations. Fifteen samples were collected within the Hanford Site boundary, four from locations near the Hanford Site perimeter and one from a distant location.
Vegetation surveillance is conducted offsite to monitor atmospheric deposition of radioactive materials in areas not under cultivation and onsite at locations adjacent to potential sources of environmental radioactivity. Nine samples of perennial vegetation were obtained during 1994, four from onsite locations, one from a distant location, and four from perimeter locations (Figure 5.6.1). Soil and vegetation sampling is conducted to monitor the accumulation of radionuclides released from Hanford facilities, to compare current data with previous years' data to determine long-term trends, and to add to the existing database of radionuclide concentrations in soils and vegetation both on and off the Hanford Site.
Radiological contributions from Hanford operations were assessed by comparing results from samples taken onsite with those collected offsite. Results obtained in 1994 were also compared to results from previous years.
Perennial vegetation samples consisted of new growth from shrub-steppe species, rabbitbrush and sagebrush. Vegetation samples were collected from the same general areas as the soil samples.
Radionuclide concentrations in soil are reported in Table 5.6.2 and Appendix A, Tables A.13 through A.16. Concentrations are shown in Figures 5.6.2 and 5.6.3. Nonparametric statistical methods were used to detect differences between locations. The Multi-Response Permutation Procedure (Mielke 1984) calculates the probability that the data sets are similar and represents that likelihood with a p value. A p value
greater than or equal to 0.1 indicates that the data sets
are similar; a p value of less than 0.1 suggests that
they are not similar.
Statistical analyses indicated no significant differences between the onsite and offsite concentrations of cesium-137, plutonium-239,240, strontium-90, and uranium-238 (p values were 0.31, 0.47, 0.98, and 0.25, respectively).
Analysis methods for uranium changed between 1989 and 1994 (Appendix A Table A.13). In 1989, and from 1992 through 1994, uranium-238 was measured by detecting low-energy photons (LEPS method). In 1990 and 1991, the alpha spectroscopy method was used, and the activities of uranium-234, -235, and -238 were summed and reported.
Radionuclide concentrations in vegetation are reported in Table 5.6.3 and are shown in Figure 5.6.4. Nonparametric statistical methods were used to detect differences between grouping categories, which were the same as those used in soil data comparisons.
Strontium-90 was identified in or on all perennial vegetation samples. There was no significant difference between the measured strontium-90 concentrations at onsite and offsite locations (p = 1.0).
Cesium-137 was identified in only 44% of the vegetation samples collected but is discussed here because of its historical interest. None of the samples obtained offsite had detectable concentrations of cesium-137. Statistical tests confirmed a difference between onsite and perimeter concentrations (p=0.086) and between the offsite (pooled perimeter and distant locations) and onsite data, p = 0.079.
The vegetation samples were also analyzed for plutonium-239,240. The nonparametric statistical analysis performed on the analytical data showed no difference between onsite and offsite results, p = 0.76.
Figure 5.6.1
Figure 5.6.2
Figure.5.6.3
Figure5.6.4
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