MASS LOADING OF SOIL PARTICLES ON A PASTURE GRASS

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 Pu-238 as an indicator of the presence of soil on vegetation. The mass loading of soil on live bahia biomass averaged 9.0 mg g-1 (standard error = 1.7 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.