FOLIAR UPTAKE OF CS-137 FROM THE WATER COLUMN BY AQUATIC MACROPHYTES

A transplant experiment was performed to determine the relative import ances of root uptake from the sediments and foliar uptake fr om the wa ter column in determining the accumulation of Cs-137 by aquatic macrop hytes. Uncontaminated individuals of three species, Brasenia schreberi , Nymphaea odorata and Nymphoides cordata, were transplanted into pots containing either contaminated sediments (i.e. 1.2 Bq Cs-137 g(-1) dr y mass) of uncontaminated sediments (i.e. <0.1 Bq g(-1) dry mass) and immersed in Pond B, a former reactor cooling pond where Cs-137 concent rations in surface waters range from 0.4 to 0.8 Bq liter(-1). The plan ts in uncontaminated sediments rapidly accumulated Cs-137 from the wat er column and after 35 days of immersion had Cs-137 concentrations in leaves that were: (1) nor statistically significantly different from t hose for plants in contaminated sediments, and (2) similar to those fo r the same species growing naturally in Pond B. The similarity in Cs-1 37 concentrations between naturally-occurring plants and those in pots with uncontaminated sediments suggests that foliar uptake from the wa ter column is the principal mode of Cs accumulation by these species i n Pond B.