FOLIAR ABSORPTION OF RESUSPENDED CS-137 RELATIVE TO OTHER PATHWAYS OFPLANT CONTAMINATION

The foliar absorption of Cs-137 sorbed to suspended soil particles was quantified at two Ukranian locations contaminated by different forms of Chernobyl fallout. Our experimental design, allowed us to separate the pathways of foliar absorption, root uptake, and contamination adhe ring to plant surfaces. Foliar absorption, root uptake, and the quanti ty of soil-attached Cs-137 adhering to leaves were greater at a loamy sand site contaminated with condensation-type fallout (Polesskoye), th an at a sandy site contaminated with fuel-particles (Chistogolavka) (0 .7 vs 0.04 kBq kg(-1); 20.8 vs 0.9 kBq kg(-1); and 3.2 vs 1.1 mBq cm(- 2), respectively). We found that when Cs-137 was very mobile in soils, root uptake grossly dominated all other plant contamination pathways. As the plant/soil concentration ratio decreased, a relative increase in foliar absorption from resuspension occurred, but it was quickly su rpassed in importance by soil adhering to plant surfaces. The data sug gest that although foliar absorption of Cs-137 from suspended soil is measurable, it is inconsequential relative to other plant contaminatio n pathways, and does not need to be considered as a critical pathway i n routine radionuclide transport models.