Uptake of natural and anthropogenic actinides in vegetable crops grown on a contaminated lake bed

Activity concentrations and plant/soil concentration ratios (CRs) of Pu-239 ,Pu-240, Am-241, Cm-244, Th-232 and U-238 were determined for three vegetab le crops grown on an exposed, contaminated lake bed of a former reactor coo ling reservoir in South Carolina, USA. The crops included greens and tubers of turnips (Brassica rapa var. white-globe), bush beans (Phaseolus vulgari s), and husks and kernels of sweet corn (Zea mays var. silver queen). Altho ugh all plots were fertilized, same received K2SO4, while others received n o K2SO4. The K2SO4 fertilizer treatment generally lowered activity concentr ations for Am-241, Cm-244, Th-232 and U-238, but differences were statistic ally significant for Am-241 and Cm-244 only. Highly significant differences occurred in activity concentrations among actinides and among crops. In ge neral, turnip greens exhibited the highest uptake for each of the actinides measured, while corn kernels had the least. For turnip greens, geometric m ean CRs ranged from 2.3 x 10(-3) for Pu-239,Pu-240 to 5.3 x 10(-2) for Am-2 41 (no K2SO4 fertilizer). For corn kernels, geometric mean CRs ranged from 2.1 x 10(-5) for Pu-239,Pu-240 and Th-232 to 1.5 x 10(-3) for Cm-244 (no K fertilizer). In general, CRs across all crops for the actinides were in the order: Cm-244 > Am-241 > U-238 > Th-232 > Pu-239,Pu-240. Lifetime health r isks from consuming crops contaminated with anthropogenic actinides were si milar to the risks from naturally occurring actinides in the same crops (to tal similar to 2 x 10(-6)); however, these risks were only similar to 0.3% of the risk from consuming the same crops contaminated with Cs-137. (C) 199 9 Elsevier Science Ltd. All rights reserved.