[en] Radionuclides associated with soil particles can be transported to plant surfaces by wind, raindrop splash, animal activities and mechanical disturbance and can contribute to radiation exposure through ingestion by humans or livestock. The quantities of radionuclides ingested with soil particles borne on plant surfaces can be estimated from the mass loadings of soil on plant surfaces (i.e. mg soil per g dry plant mass) and the radionuclide concentrations in soil. However, relatively few estimates of mass loadings are available for either row or pasture crops. Estimates of the concentration of soil on bahia grass, a common pasture species on the sandy soils of the southeastern United States, were obtained using ²³⁸Pu as an indicator of the presence of soil on vegetation. The mass loading of soil on live bahia biomass average 9.0 mg g^-1, which is similar to that for some row crops grown on the same soils. The mass loading for bahia pasture may be less than that for English pastures but differences in methodologies among studies complicate comparisons. (author)

[en] To evaluate the importance of particle settling on the behavior of ^239,240Pu inventories in the water column of a monomictic reservoir, the sedimentation fluxes of ^239,240Pu were measured using sediment traps and compared to the Pu inventories. Sedimentation flux from surface to deeper waters averaged 5.4 mBq ^239,240Pu m^-2 d^-1 which represented ≥ 3% of the surface water inventory of Pu per day. The fluxes were large enough to account for (1) the observed declines in the Pu inventories of surface waters following stratification and (2) the rapid increase in Pu inventories in deeper waters immediately following stratification. (Author)

[en] Previous studies in Pond B, a 12-m deep, 82 ha reservoir that once served as a reactor cooling pond, had (i) suggested the preferential accumulation of ¹³⁷Cs in sediments at a water depth of 3 m within the littoral zone and (ii) attributed this accumulation to the effects of either macrophyte vegetation or sediment slope. To test for the preferential accumulation of ¹³⁷Cs at intermediate depths within the littoral zone, sediment cores were taken at water depths of 0.5, 1,2,3,4 and 5 m along 6 transects in Pond B. The sediment structure was similar at all water depths in the littoral zone with a surface layer of 0.02-0.04m of plant debris and fine sediments over a base of sandy sediments. The ¹³⁷Cs was largely restricted to the surface layer of fine sediments, and there was no indication of preferential accumulation of fine sediments or ¹³⁷Cs at water depths of 3m. There was no apparent relationship between sediment slope and ¹³⁷Cs content. Although the ¹³⁷Cs entered Pond B more than 20 years ago, its prevalance in the surface layers of littoral zone sediments resembles the pattern observed for ¹³⁴Cs deposited in European lakes from the recent Chernobyl accident. (Author)