13. Romey, E. M., A. Wallace, P. A. T. Wieland, and d. E. Kinnear. 1976, "Plant Uptake of 779°?"pu and 7"!Am Through Roots Containing Aged Fallout Materials." Report UCLA 12-1056. pp. 1-15. 14. Schulz, R. K., G. A. Tompkins, and K. L. Babcock. Plutonium and Americium by Plants from Soils," In: Nuclides tn the Environment. 15. IAEA, Vienna. 1976a. "Uptake of Transuraniwn pp. 303-310. Schulz, R. K., G. A. Tompkins, L. Levanthal, and K. L. Babcock. 1976b. "Uptake of Plutonium and Americium by Barley from Two Contaminated Nevada Test Site Soils." J. Enutron. Qualtty 5:406-410. 16. Wallace, A. 1974. "Behavior of Certain Synthetic Chelating Agents in Biological and Soil Systems." Report UCR 34P51-37. pp. 1-12. 17. Wildung, R. E., and T. R. Garland. 1974. "Influence of Soil Plutonium Concentration on Plutonium Uptake and Distribution in J. Agric. and Food Chem. 22:836-838. ieran AE Shoots and Roots of Barley." RETENTION, ABSORPTION, AND TRANSLOCATION OF FOLIAR CONTAMINANTS D. A. Cataldo and B. FE. Vaughan Battelle Pacific Northwest Laboratories Richland, Washington ABSTRACT The interaction of airborne pollutants with foliage of terrestrial plants has been investigated from many aspects including interception, retention and absorption. Although interception parameters for both gaseous and particulate pollutants have been effectively modeled, the behavior and fate of pollutants following foliar interception are unresolved. This is especially true for particulates. Particles having 10 to 200 ym diameters exhibit retention half-times of 10 to 24 days. However, direct and indirect data suggest that submicronic particles are more effectively retained on plant foliage than are larger particles analogous to Close in fallout. Studies are presented to describe the retention behavior of submicronic size particles deposited onto foliage of bushbean and sugar beet plants. Retention efficiency was evaluated using a simulated rainfall. These studies showed submicronic particles to be increasingly less available for leaching with increasing residence time on the leaf, with > 90% of the foliar plutonium deposits being firmly held to the leaf surface. Retention mechanisms are discussed based on leaf morphology and leaching regimes employed. The absorption of foliar plutonium and its subsequent translocation to seed and root tissues was dependent on a number of parameters including chemical form and the presence or absence of a solution vector. - ete ie INTRODUCTION ee | ES Terrestrial plants represent an effective sink for atmospheric pollutants, both gaseous and particulate. Frey et al., (1964) estimate that of the total land area of the earth, approximately 35% is covered by forest vegetation, 30% by brushiands, tundra and deserts, and 25% is employed for agricultural purposes. Although this provides a large and effective surface area for the interception of airborne pollutants, many questions remain unresolved, especially with respect to particle behavior and fate on interaction with plant canopies. Atmospheric transport and resuspension studies have adequately described the modes of transport of particles, their atmospheric residence time, their hehavior with respect to particle size, and their sedimentation and deposition rates (Slinn, 1976). Much of the information available concerning the interception of particulates by plant canopies results from nuclear-related fallout and resuspension studies, These have generaily been concerned with the extent of foliar 330 331