The relative importance of uptake and surface adherence in determining the radionuclide contents of subterranean crops.

The adherence of Pu-bearing particles to external surfaces of carrots, turnips, red potatoes, and sweet potatoes accounted for greater than or equal to 93% of their total Pu content. Uptake, which was measured as Pu content in peeled crops, accounted for less than or equal to 7%. Plutonium concentrations in most peeled crops were below background, and consequently, uptake could not be conclusively demonstrated. However, uptake accounted for most of the 137Cs, 40K, and 226Ra contents of subterranean crops. Concentration ratios for total radionuclide contents (i.e. surface adherence plus uptake) ranged from 3.9 X 10(1) for 40K, to 1.1 X 10(-2) for 239, 240Pu. Approximately 1.5 X 10(-3) pCi 239, 240Pu adhered per cm2 of subterranean crop surface per 1 pCi Pu/g of soil.