Foliar uptake of 137Cs from the water column by aquatic macrophytes

A transplant experiment was performed to determine the relative importances of root uptake from the sediments and foliar uptake from the water column in determining the accumulation of 137Cs by aquatic macrophytes. 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 137Cs g−1 dry mass) or uncontaminated sediments (i.e. < 0.1 Bq g−1 dry mass) and immersed in Pond B, a former reactor cooling pond where 137Cs concentrations in surface waters range from 0.4 to 0.8 Bq liter−1. The plants in uncontaminated sediments rapidly accumulated 137Cs from the water column and after 35 days of immersion had 137Cs concentrations in leaves that were: (1) not statistically significantly different from those for plants in contaminated sediments; and (2) similar to those for the same species growing naturally in Pond B. The similarity in 137Cs concentrations between naturally-occurring plants and those in pots with uncontaminated sediments suggests that foliar uptake from the water column is the principal mode of Cs accumulation by these species in Pond B.