Fate of Plutonium Intercepted by Leaf Surfaces: Leachability and Translocation to Seed and Root Tissues.

摘要

A low windspeed plant exposure chamber was employed for the generation and deposition of particulate exp 238Pu as nitrate,citrate,and oxide (fresh and aged) onto foliage of Phaseolus vulgaris. Physical deposition characteristics and particle sizing were routinely measured and deposition parameters calculated. At wind speeds of 0.42cm sec exp -1 ,deposition velocities for these compounds were of the order 10exp -3cm sec exp -1with deposition rates onto exposed foliage of 0.26to 0.52 pg exp 238Pu cm exp -2sec exp -1 . The fate of surface deposited Pu compounds with respect to chemical modification and leachability was evaluated by leaching with synthetic rainwater and 0.1percent HNO sub 3solutions. Leaching of contaminated foliage with acidified solutions resulted in a 1-to-9fold increase in Pu removal from foliar surfaces,depending upon chemical form,as compared to rainwater. Sequential leaching of foliage at 1, 7, 14,or 21days after contamination indicated a reduced leachability of surface deposits with residence time on the leaf. The extent of leaching and concentration of soluble component was dependent on chemical form supplied (Pu-citrate greater than -nitrate greater than -aged oxide greater than -fresh oxide). The bioavailability of Pu as measured by translocation of foliarly deposited plutonium to root and seed tissue was markedly affected by the presence of a solution vector (i.e.,simulated rainfall),and also the timing of its application.